Galvo/Amp Upgrade

Hey everyone, I wanted to start a new thread which is somewhat a continuation of https://photonlexicon.com/forums/sho...ion-Help/page5.

I will have my new Compact 506 Scanners today and have a few questions on the upgrade as I really do not want to fry anything. So to sum it up, i have a Chinese laser from aliexpress (Emma Laser EM-RGB24B) in which I am replacing scanners. I have been looking at this thread as a hopeful source of information among others and have started to ohm back from the ILDA referring to ilda pinout but I have a few questions.

1. I can attach the new amp boards directly from the ILDA connector, correct? I have been trying to ohm back and I get beeps on multiple pins going through the onboard ilda connector. Not sure how best to explain it.
2. When I disconnect the ribbon cable from the back of the ilda port board which also has the RGB connectors for lasers I get no laser output which I am sure has to do with the laser key switch. How could I still utilize that? Connect all the lasers common grounds to it and back to lasers?

Thanks everyone for the help and let me know if I need to give anymore information that could help.


Attachment 56808
Attachment 56809
Attachment 56810
Attachment 56811

I bet the reason you lose output when you unplug the ribbon cable from the ILDA board is because the ILDA board is powered from the SD card board via that ribbon cable. The best way to hook up the new scanners depends on how all of the components currently connect and what you want to achieve with the whole projector. Are you looking to keep the SD/DMX board in there and usable, or do you only care about ILDA input? If the latter, you can rip out most of the electronics in there and replace them with a simple ILDA breakout board. Either way, start by tracing out the physical wires from component to component, and if you can make a diagram to share here that would certainly help get you useful advice. A photo of the SD card board and the other side of the ILDA board would help, too.

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Originally Posted by aberry

I bet the reason you lose output when you unplug the ribbon cable from the ILDA board is because the ILDA board is powered from the SD card board via that ribbon cable. The best way to hook up the new scanners depends on how all of the components currently connect and what you want to achieve with the whole projector. Are you looking to keep the SD/DMX board in there and usable, or do you only care about ILDA input? If the latter, you can rip out most of the electronics in there and replace them with a simple ILDA breakout board. Either way, start by tracing out the physical wires from component to component, and if you can make a diagram to share here that would certainly help get you useful advice. A photo of the SD card board and the other side of the ILDA board would help, too.

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Thanks for reply. I actually have no care to keep the existing sd card setup. I primarily just want ILDA control I was thinking i could just use the current ILDA breakout board and solder the connections directly to the back (maybe not the cleanest)? My hopes were that I would only need to worry about Y+ Y- and X+ X- but the lasers not outputting when the ribbon is disconnected threw a wrench into that. It looks as if the laser signals or grounds are transmitted from the ILDA board, through the ribbon to the display/sdcard board and then possibly back to the ILDA board again. The display/sdcard board has a two pin connector from the key switch so I would assume that the laser signals have to pass through it and then back? If any of that makes sense. I will try to work on a diagram if it is needed.

From the back of the ILDA PCB it looks like there's circuitry on the front, so it depends on what functionality that board contains. Your minimal effort solution to get the new galvos working is probably to leave all of the existing electronics in place and just connect the new galvos exactly how the old ones were connected. If you want to get rid of the SD/DMX boards then it's probably easiest to remove and replace the existing ILDA board as well rather than trying to make it work without the other bits, but that may require hacking up the case a bit.

Here is my diagram, sorry its not the greatest.
Attachment 56815

Looks like I may be pretty stuck. The lasers will only light up, ILDA or SD, when the existing amp and galvos are plugged in. I know this laser has a beam safety mechanism when the laser scan angle is below a certain degree. This may be preventing the lasers from firing up. So I suppose my next line of questioning is, if I get another ILDA breakout board, what are all the wires I need to worry about? X+ X- Y+ Y- Ground, R+, R-, G+, G-, B+, B-? or will I also need Intensity + and Intensity - as well?

ILDA Standard Pinout


Pin Number Signal Name
1 X+
2 Y+
3 Intensity +
4 Interlock A
5 R+
6 G+
7 B+
8 User-defined signal 1+
9 User-defined signal 2+
10 User-defined signal 3+
11 User-defined signal 4+
12 Projector return signal
13 Shutter
14 X-
15 Y-
16 Intensity -
17 Interlock B
18 R-
19 G-
20 B-
21 User-defined signal 1-
22 User-defined signal 2-
23 User-defined signal 3-
24 User-defined signal 4-
25 Ground

Your diagram only shows part of the system. It's possible that the galvo driver is providing a +/- 15V supply to the rest of the components.

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Originally Posted by aberry

Your diagram only shows part of the system. It's possible that the galvo driver is providing a +/- 15V supply to the rest of the components.

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That makes sense, not sure what the 4 pin wire is, cannot see any writing.

The post I linked to has almost an identical board. Just need to know how he set everything up lol. Here is the rest of the diagram, wasnt sure how much was needed but I supposed the whole picture is good.

Attachment 56816

To add a little more about the laser 2 pin connectors on the ILDA board. The positives do "ohm back correctly to their respective R, G, B + pins on the ILDA connector. The Grounds for each seem to have commonalities amongst a few pins (not sure if this is as intended). This was done without the ribbon cable connected.

I think I am progressing along here, not too sure. For the laser shut off key, can I route the gounds from the ILDA RGB negatives through this to work it properly or does it need to be controlled by a relay of sorts?

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Originally Posted by jdavis7765

To add a little more about the laser 2 pin connectors on the ILDA board. The positives do "ohm back correctly to their respective R, G, B + pins on the ILDA connector. The Grounds for each seem to have commonalities amongst a few pins (not sure if this is as intended).

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Yes, it is normal for the negative color signals to share a common ground. Most controllers use a single-ended output for the color modulation signal, so the R-, G- and B- signals are already common to ground from the controller end.

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Originally Posted by jdavis7765

For the laser shut off key, can I route the gounds from the ILDA RGB negatives through this to work it properly or does it need to be controlled by a relay of sorts?

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You can do this, but a better method would be to use the keyswitch to control a triple-pole, double-throw relay and switch each one of the POSITIVE inputs to the drivers.

The idea is that in the de-energized position the relay would connect the positive side of the laser driver modulation inputs to ground, making sure that there is no possibility of laser output. (Certain laser drivers will allow some output if the positive modulation input is disconnected and left floating, so by crowbarring to ground you eliminate that possibility.)

When the relay is energized it should connect the modulation inputs on the drivers to the appropriate R+, G+ and B+ pins on your ILDA connector.

Here's a complete interlock schematic. Look at the relay contacts for Red, Green, and Blue and you'll see what I'm talking about. Note, however, that this circuit also includes a remote, a latching relay, a projector "start" circuit, and a few other features that you probably weren't planning to add to your projector.

Adam

First of all, thank you all for the replies!

I am reuploading the schematic, not sure what revising I need to do to omit the remote interlock box. I took electronics is highschool but I am far from perfect, but does this looks like what I would need to omit? Would I need to keep the diode and the inductor as well (circled in purple)Attachment 56831 or can that be ommited as well?

Again thanks for helping me out :)

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Originally Posted by buffo

Yes, it is normal for the negative color signals to share a common ground. Most controllers use a single-ended output for the color modulation signal, so the R-, G- and B- signals are already common to ground from the controller end.



You can do this, but a better method would be to use the keyswitch to control a triple-pole, double-throw relay and switch each one of the POSITIVE inputs to the drivers.

The idea is that in the de-energized position the relay would connect the positive side of the laser driver modulation inputs to ground, making sure that there is no possibility of laser output. (Certain laser drivers will allow some output if the positive modulation input is disconnected and left floating, so by crowbarring to ground you eliminate that possibility.)

When the relay is energized it should connect the modulation inputs on the drivers to the appropriate R+, G+ and B+ pins on your ILDA connector.

Here's a complete interlock schematic. Look at the relay contacts for Red, Green, and Blue and you'll see what I'm talking about. Note, however, that this circuit also includes a remote, a latching relay, a projector "start" circuit, and a few other features that you probably weren't planning to add to your projector.

Adam

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Sorry for the double reply, but two more quick questions. In the drawing I did above. Can you tell from the looks of it if the RGB two pin laser connectors look as if they would plug into their respective ILDA pins? It looks as though they do but I just want to be safe?

Second question, would I want to make all the RGB ILDA grounds common all the way back to the laser PSU? How about common ground to the Scanner PSU?

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Originally Posted by jdavis7765

I think I am progressing along here, not too sure. For the laser shut off key, can I route the gounds from the ILDA RGB negatives through this to work it properly or does it need to be controlled by a relay of sorts?

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No, this will only work if the input terminals are isolated from the power supply, which is not going to be the case with virtually any laser driver. The positive modulation lines are still referenced to the system ground, which your diode drivers are still going to be connected to via the power supply. So there's still a common ground reference that can cause the drivers to see a modulation signal even with the negative modulation line connected, even if the driver has differential inputs. (A standard opamp+four resistor diff amp like this one just becomes a unity-gain amplifier with divided input if you disconnect the negative input.) Even without that implicit ground reference between the control signals and the drivers, the diode drivers still share a common ground via the power supply with each other, and differential voltages between the color signals can be converted into voltages that will activate one or more diode drivers by parasitic pathways through the driver input circuitry.


Using a relay as buffo has shown will be the simplest and most reliable way to go.

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Originally Posted by jdavis7765

I think I am progressing along here, not too sure. For the laser shut off key, can I route the gounds from the ILDA RGB negatives through this to work it properly or does it need to be controlled by a relay of sorts?

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That inductor is actually the coil for the relay, and the diode is there to suppress the voltage spike that will otherwise occur when the relay switches off. I've taken the liberty of sketching a minimal relay-based key switch circuit just to make the base circuit clearer. This can be extended in many ways by changing how the relays are driven. I've also shown two relays because many of the multi-pole relays you can find off-the-shelf are designed for handling high power circuits and are not necessarily suitable for small signals. Note that a Class IV laser is actually required to have a manual reset action to restore output, which requires the sort of latching circuit included in buffo's schematic.

I updated the original thread here with the final results if you want to check it out. Thanks all for answering my questions along the way!

Thanks to Andrew for re-drawing the schematic. :) Also, he correctly pointed out that interrupting the ground connection on the modulation input won't work because of the shared ground on the power input side. I had forgotten about that! But yeah, the correct method is to interrupt the positive modulation signal, which is shown in both schematics.

The parts of my original schematic you crossed out are mostly correct, assuming that you don't want the remote box, but you did miss a few points. First, you need to connect the emitter of the 3055 transistor (the bottom part with the arrow pointing out - basically the output of the transistor in this circuit) directly to the input side of the relay coil and remove the latching contact portion of the relay (the first set of contacts above the coil). You also need to leave the 10K resistor in place that connects the base of the transistor to ground.

If you trace through the circuit, this will become obvious: Closing the keyswitch applies 12 volt power to the collector of the 3055 transistor. If you have the ILDA plug connected to the controller, then 12 volt power will also flow to pin 17, down the ILDA cable to your controller, through the loop at the controller end, and back to the projector on pin 4. That 12 volt signal then hits the base of the 3055 transistor, so you've got 12 volts positive on the base. (The 10K resistor from the base to ground ensures this.) So now you have an NPN transistor with the collector positive and the base positive, which means the transistor will be "ON" and you'll have somewhat less than 12 volts at the emitter. But now you need this voltage to get to the relay coil to pull the contacts closed, and since you've removed the remote box (with the run button) there's no path for the output of the transistor to get to the relay at this point.

To remedy this you need to remove the latching contact entirely and just connect the output of the transistor directly to the relay coil. Or, if you wanted to keep the ability to have a "run" or "start" button that would have to be pressed each time you wanted to re-start the projector following a power loss or unplugging a cable, then you could install a normally open, momentary push-to-close switch between the output of the transistor and the input to the relay coil and leave the latching contacts wired as shown. Then when you push the run button the relay coil energizes for a brief moment, but as soon as the contacts close that first set of latching contacts will complete the circuit from the transistor to the coil, at which point you can let go of the run button and the coil will stay energized through the latching contacts.

Note also that you crossed out the wire for the emission indicator LED, but you did not cross out the actual LED. So if you want an emission indicator, you need to leave the LED and the wire that feeds it hooked up. Otherwise, yeah, remove both. (Andrew's circuit keeps the emission indicator intact.)

Another difference is that one of the relay contacts on my circuit is used to switch the DC + supply to the lasers on and off, whereas in Andrew's circuit that pole is used to connect or disconnect the shutter signal from the controller to the shutter. Either option is fine, but as my projector did not have a shutter I decided to use DC power interruption as my secondary beam attenuation method.

I completely agree with Andrew's suggestion to use a pair of double-pole, double-throw relays instead of a single, larger relay with more poles. In truth, when this circuit was installed in the projector that's exactly what I did - the schematic simply shows all the poles on a single relay for simplicity's sake. Also, some folks may wonder why I chose a 3055 transistor (which is normally used for power switching of large loads - up to 10 or 15 amps), and the answer is that it was what I had laying around when I first put this together. But any NPN transistor that can handle the combined current draw of the relay coil and the emission indicator will work.

Finally, I feel it's important to note that I am a self-taught amateur when it comes to electronics, while Andrew makes a living designing electronics for X-Laser. The fact that he could explain things in two paragraphs while I had to write a book to explain my schematic should be an indicator of his superior knowledge and experience! :) Furthermore, his schematic is far easier to follow. The only reason for the added complexity of the transistor in my circuit was due to concerns about voltage drop over possibly long cable runs (both the ILDA cable and the remote box cable), but since you're omitting all that along with the redundant attenuation method I think you'd actually be better off using Andrew's simplified design rather than trying to modify mine.

Adam

Still have to complete the key switch circuit when I have some more time. Had another question before that though.

I wondered how to correctly position the scanner block so that the beam hits is correctly? I can figure out the horizontal position, but vertically, I can't seem to find a great way to do this. Should I just buy a solid block of aluminum and cut as needed? If so, what would be the best way to measure the height I would need the block to be? I have a digital caliper for measurements, but am confused how to measure the beam height in relation to mounting location without adding a lot of trial and error.

Thanks again :)

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Originally Posted by jdavis7765

I wondered how to correctly position the scanner block so that the beam hits is correctly? I can figure out the horizontal position, but vertically, I can't seem to find a great way to do this. Should I just buy a solid block of aluminum and cut as needed?

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Most scanner blocks have a designed beam-entry elevation of close to 1". Actually, there will be two acceptable entry elevations, depending on how you orient the scanner block in the projector (left entry vs right entry, meaning either you hit the top mirror first or you hit the bottom mirror first).

Here's a drawing for the Pangolin Compact 506 scanner block showing both beam elevations: https://www.scannermax.com/pdf/4mm_W...m_Assem_LH.PDF

If you don't have a drawing for your scanners you can measure from the bottom of the scanner block to the height of the galvo shaft on the mirror that the beam will strike first. That's the native elevation of the scanner block. Now measure the height of the incoming beam. If there is a significant difference between the two measurements , you will need to either shim the scanner block up or shim the lasers up. Ideally you want the incoming beam to be exactly level with the center of the first scanner mirror that the beam will strike. But if you are off a tiny amount it's not the end of the world. As long as you aren't so far off that part of the beam will "spill" off the edge of the mirror when it moves, you'll be fine.

I don't know that you need to go buy a solid block of aluminum though. Unless you have access to a milling machine it will be very difficult to cut a solid block of aluminum down to size. It's far easier to simply stack up some thin layers of sheet metal underneath the scanner block to raise it to the correct height.

On the other hand, if you need to adjust the height of the lasers, then you need to do a little planning first. Layering several pieces of sheet metal under the lasers will reduce the heat transfer to the baseplate, which might be a concern. In this case it might be better to purchase a single piece of plate aluminum and then cut out a rectangle that is large enough to mount your laser on while leaving room at the edges so you can bolt the whole thing to the baseplate. (You can easily cut the rectangle out from the plate with a jig saw and a metal blade.)

Of course, plate aluminum is commonly available in just a few thicknesses, so you'll probably end up shimming the lasers until they are too high, and then doing the fine-adjustment by shimming the scanner block with some thin sheet metal until you match everything up.

Note that if you end up shimming the lasers you will need to re-align them, which is going to be a pain if you don't have good adjustable mounts. So if you can avoid messing with the optical path that would be best!

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If so, what would be the best way to measure the height I would need the block to be? I have a digital caliper for measurements, but am confused how to measure the beam height in relation to mounting location

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A digital caliper is far more precise than necessary. :) Just power up the lasers, stick a tape measure in the beam just before it would enter the scanner block, and measure the height of the beam above the optical baseplate. Now measure the distance from the bottom of the scanner block to the center of the first mirror. Ideally the scanner measurement will be slightly less than the beam height measurement. The difference is how much shim thickness you need to add under the scanner block to match everything up.

If the beam height is too low, then you have to consider shimming the lasers up, which is more involved. Alternately, if you do have access to a mill, you could put your scanner block in the mill and shave off some material from the bottom of the scanner block to lower it's height...

Adam

To expand on what I posted above - sometimes the beam heights just don't work out. (Particularly in home-built projectors where the red, green, and blue lasers could be in wildly different housings.) One solution to this problem is to use "floating tables" for the laser mounts. Basically you mount each laser on it's own 1/4 inch thick aluminum plate, and each laser table is then supported at the 4 corners by a threaded rod with a nut on the bottom (to hold it up off the main baseplate) and a nut on the top (to keep it secure).

This arrangement allows you to tweak the beam height of the laser very accurately, and it also allows you to adjust the beam direction (up, down, or perfectly horizontal) relative to the main baseplate. It was more commonly used in the past when you had mixtures of DPSS and direct diode lasers in the same projector.

Here is a picture from 2007 (link) of a test stand that I put together when I was building my very first RGB projector. You'll notice that the lasers are on floating tables and the scanner block also has a large shim (5/8 inch) beneath it. The MM1 mounts are for adjusting the dichros, while the large MM2 adjusts the steering mirror that aims the combined white beam at the galvo block. Having that final steering mirror allowed for slight miss-alignment between the beam height coming off the optical table and the beam entry elevation on the scanners.

https://photonlexicon.com/gallery/bu...tor/Layout.jpg

And yeah, it is super-messy, I know! I threw it together rather quickly. The idea was to test everything to make sure it all worked before I started mounting stuff inside the actual projector case. (And yeah, everything worked. :o My avatar picture is from some of the "first light" pictures that I took when I first powered up this test stand.)

Adam

https://photonlexicon.com/gallery/?d=buffo/rgbprojector

Awesome stuff, thanks for sharing the picture as well. It gives me ideas for how I can make it work better. I thought I would be able to cut a 2x2 block of aluminum with metal blade on circular saw (metal blade), but maybe I was wrong :/. I was thinking, if I could not cut on my own, I could give a machine shop the specs and have them fab something for me as well. I did look at the diagram but for some reason it did not register that the one view shows the beam entering and the height at which it should enter. Okay, I just needed someone to help start the gears turning in my brain lol.


Side note... If I were thinking about upgrading the lasers at any point, is there any website that sells them you could recommend or even recommended lasers? When I say upgrade, i do not mean higher power, I quite like where I am at now. I just wonder if I can get better color from better lasers vs what I have now.

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Originally Posted by jdavis7765

I thought I would be able to cut a 2x2 block of aluminum with metal blade on circular saw (metal blade), but maybe I was wrong :/.

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I have successfully cut 1/4 inch thick aluminum plate using a table saw with a carbide-tipped blade, but this is admittedly a risky task. You need to go very slow! If you overload the saw it can violently kick the plate back at you, potentially causing serious injury. Also, this only works with aluminum. Do *not* try it with steel. (Trust me on this - you will have a very bad time if you try it with steel!)

In theory you could do the same thing with a circular saw, but again, it's risky. For sure you'd want to have the aluminum plate clamped down really firmly before you started, and again you need to go slow with the skill saw. But a carbide-tipped blade will cut through aluminum reasonably well provided you take the appropriate precautions.

Note that this only applies to cutting plate. Cutting a 2 inch thick piece of solid aluminum is probably beyond the abilities of your average hobbyist unless you happen to have a mini mill or a really nice band saw. If you need to work with material that thick you probably want to take it to a machine shop.

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I did look at the diagram but for some reason it did not register that the one view shows the beam entering and the height at which it should enter.

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OK, but you see it now, right? The Compact 506 scanners have a beam entry height of 25 mm if you come in from the right and hit the top mirror first, or a beam entry height of 18 mm if you come in from the left and hit the bottom mirror first. (To do the "left entry" the block has to be rotated 90 clockwise.) All of this assumes that you are facing the block with the output beam coming straight at you.

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If I were thinking about upgrading the lasers at any point, is there any website that sells them you could recommend or even recommended lasers? When I say upgrade, i do not mean higher power, I quite like where I am at now. I just wonder if I can get better color from better lasers vs what I have now.

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There are several suppliers, sure, but I'm not sure exactly what you're wanting to improve.?. I thought the lasers in your projector already supported analog color modulation... If so, then you should be able to dial in just about any color you want. Or is there another problem with color that you're referring to?

Usually when people ask about getting "better color" it's because they're looking to get rid of subtle modulation issues that can leave "tails" or other artifacts in graphics shows - particularly when parts of an image have the intensity faded down very low. Fixing issues like this is normally a matter of switching to a better diode driver for the lasers. Is that what you're talking about?

Adam

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Originally Posted by buffo

I have successfully cut 1/4 inch thick aluminum plate using a table saw with a carbide-tipped blade, but this is admittedly a risky task. You need to go very slow! If you overload the saw it can violently kick the plate back at you, potentially causing serious injury. Also, this only works with aluminum. Do *not* try it with steel. (Trust me on this - you will have a very bad time if you try it with steel!)

In theory you could do the same thing with a circular saw, but again, it's risky. For sure you'd want to have the aluminum plate clamped down really firmly before you started, and again you need to go slow with the skill saw. But a carbide-tipped blade will cut through aluminum reasonably well provided you take the appropriate precautions.

Note that this only applies to cutting plate. Cutting a 2 inch thick piece of solid aluminum is probably beyond the abilities of your average hobbyist unless you happen to have a mini mill or a really nice band saw. If you need to work with material that thick you probably want to take it to a machine shop.

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Yeah, I got the block in the mail today and I do not think this is something I want to do on my own. I think I will just get the measurement and pop into a local machine shop to see if they can cut it for me.

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Originally Posted by buffo

OK, but you see it now, right? The Compact 506 scanners have a beam entry height of 25 mm if you come in from the right and hit the top mirror first, or a beam entry height of 18 mm if you come in from the left and hit the bottom mirror first. (To do the "left entry" the block has to be rotated 90 clockwise.) All of this assumes that you are facing the block with the output beam coming straight at you.

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Yes, I see it now, should be fairly easy to measure once I get the beam height. :)

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Originally Posted by buffo

There are several suppliers, sure, but I'm not sure exactly what you're wanting to improve.?. I thought the lasers in your projector already supported analog color modulation... If so, then you should be able to dial in just about any color you want. Or is there another problem with color that you're referring to?

Usually when people ask about getting "better color" it's because they're looking to get rid of subtle modulation issues that can leave "tails" or other artifacts in graphics shows - particularly when parts of an image have the intensity faded down very low. Fixing issues like this is normally a matter of switching to a better diode driver for the lasers. Is that what you're talking about?

Adam

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I suppose maybe my ignorance got the best of me. I guess what I am referring to is the blending of colors (assume this would be the effect of modulation) when comparing laser to program on the computer. I know it will not be 100 percent accurate, it just sometimes appears "off". Do you have a an example of the "tails" you referred to?

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Originally Posted by jdavis7765

I think I will just get the measurement and pop into a local machine shop to see if they can cut it for me.

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With luck the beam height of the lasers will be equal to or greater than the beam entrance height for your scanners. Then you can just shim the scanner block up if needed using several layers of sheet metal, which you can cut yourself.

But yeah, if the laser height is lower than the beam entrance elevation for the scanner block then your best bet is to take the scanner block to a shop and have them shave it.

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what I am referring to is the blending of colors (assume this would be the effect of modulation) when comparing laser to program on the computer.

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The quality of the color blending you see in the output is directly related to the quality of the laser diode drivers. If the analog modulation response of the driver is linear, you should see great color blending. On the opposite end, a pure TTL driver (so on-off modulation only) will only give you 7 possible colors. Most analog drivers show at least some non-linearity, but any analog modulation ability (even from a really cheap driver) is still going to look worlds better than TTL modulation. But yeah, better drivers = better color gradients.

Don't forget that you can also tweak your color settings in software. Often a little software adjustment can largely correct the limitations of a cheap analog driver. For example, if you notice that your orange looks more like yellow, or if your white has a greenish tint to it, these are things you can tweak in software. Some software will also allow you to adjust the modulation curve throughout the range from 0 to 100% output, which is even more helpful.

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Do you have a an example of the "tails" you referred to?

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I had to do some digging, but I found a few examples. (Funny how people never seem to save pictures that show a problem!)

In this post, have a look at the 3rd picture which shows a green question mark being displayed. The dot beneath the question mark has a pronounced tail where the laser did not turn off at the point when the dot was fully drawn. The is the most common example of a "tail", and it can usually be fixed by simply adjusting the blanking offset value in software. However, if you have wildly miss-matched drivers you may need to install a delay circuit to match up the response times. (This was a bigger problem back when we had both DPSS and direct-diode lasers in the same projector, but nowadays nearly all projectors use all direct-diode lasers.)

Another, more subtle example of tails can be seen in this post. Here the effect is harder to notice, but if you look at the starting and ending points of the white line segments you can see a small yellow tail on some of them, and a very tiny blue tail on some as well. The corrected picture to the right isn't perfect, as there are still a few blue tails visible, but it's much better than the initial picture. Fixing this problem required the addition of the delay circuit I mentioned above.

If you're experiencing tails as shown in the first example (the question mark picture), then you can probably fix that by adjusting your blanking offset. But if you have tails and/or blending artifacts that look more like the second example, then you'll either need to install a delay circuit on each of the 3 color modulation inputs to the projector, or you'll need to replace the laser drivers with ones that have superior modulation response.

But again, before you start pricing new drivers be sure you've tried to adjust your colors in software first, because most modern laser show software includes several settings that can be used to tweak your color modulation.

Adam

So, got my block of aluminum and machine shop said 130 dollars to cut. I went and bought aluminum cutting blade for miter saw, secured black to saw with clamp, put cinder block in between me and saw for safety and it cut through like butter. Got that done and holes drilled to mount and it seems like I have the tails you are referring to, only these appear to be cause by galvo block placement. If I slide the block toward or away from the back or front of projector, it moves to the top of the bottom. It looks like there is a sweet spot but with my limited abilities it will take quite a few attempts to get right. This leads me to think, did I get the wrong size mirrors? Should I have went with 5mm instead of 4 as it may have been easier to align? It seems to be more pronouced on red than any other color as well, not sure what that indicates as the blue beam appears to not be circular yet it looks more like a small vertical rectangle so I figure that would have more spill off on mirrors. Let me know what you all think.
Attachment 56924

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Originally Posted by buffo

With luck the beam height of the lasers will be equal to or greater than the beam entrance height for your scanners. Then you can just shim the scanner block up if needed using several layers of sheet metal, which you can cut yourself.

But yeah, if the laser height is lower than the beam entrance elevation for the scanner block then your best bet is to take the scanner block to a shop and have them shave it.



The quality of the color blending you see in the output is directly related to the quality of the laser diode drivers. If the analog modulation response of the driver is linear, you should see great color blending. On the opposite end, a pure TTL driver (so on-off modulation only) will only give you 7 possible colors. Most analog drivers show at least some non-linearity, but any analog modulation ability (even from a really cheap driver) is still going to look worlds better than TTL modulation. But yeah, better drivers = better color gradients.

Don't forget that you can also tweak your color settings in software. Often a little software adjustment can largely correct the limitations of a cheap analog driver. For example, if you notice that your orange looks more like yellow, or if your white has a greenish tint to it, these are things you can tweak in software. Some software will also allow you to adjust the modulation curve throughout the range from 0 to 100% output, which is even more helpful.



I had to do some digging, but I found a few examples. (Funny how people never seem to save pictures that show a problem!)

In this post, have a look at the 3rd picture which shows a green question mark being displayed. The dot beneath the question mark has a pronounced tail where the laser did not turn off at the point when the dot was fully drawn. The is the most common example of a "tail", and it can usually be fixed by simply adjusting the blanking offset value in software. However, if you have wildly miss-matched drivers you may need to install a delay circuit to match up the response times. (This was a bigger problem back when we had both DPSS and direct-diode lasers in the same projector, but nowadays nearly all projectors use all direct-diode lasers.)

Another, more subtle example of tails can be seen in this post. Here the effect is harder to notice, but if you look at the starting and ending points of the white line segments you can see a small yellow tail on some of them, and a very tiny blue tail on some as well. The corrected picture to the right isn't perfect, as there are still a few blue tails visible, but it's much better than the initial picture. Fixing this problem required the addition of the delay circuit I mentioned above.

If you're experiencing tails as shown in the first example (the question mark picture), then you can probably fix that by adjusting your blanking offset. But if you have tails and/or blending artifacts that look more like the second example, then you'll either need to install a delay circuit on each of the 3 color modulation inputs to the projector, or you'll need to replace the laser drivers with ones that have superior modulation response.

But again, before you start pricing new drivers be sure you've tried to adjust your colors in software first, because most modern laser show software includes several settings that can be used to tweak your color modulation.

Adam

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Originally Posted by jdavis7765

it seems like I have the tails you are referring to, only these appear to be cause by galvo block placement

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The tails I mentioned in my previous post are artifacts in the displayed image on the wall. They are caused by the timing of the lasers not being sync'd to the galvos. So you have a situation where the galvos are still trying to get to the point where the laser should turn on, but the laser turns on too early and the line that should be blanked ends up being partially lit. Or, if the laser timing is late, then the galvos have gone past the end of the line and are now heading off to another part of the image, but the laser is still on so again part of the line that should be blanked ends up being partially lit.

I can't understand how moving the galvo block would cause tails like this in the displayed image. Also, the picture you posted only shows a single vertical red line with clearly-defined end-points, so that doesn't really look like the tails that I was talking about.

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If I slide the scanner block toward or away from the back or front of projector, it moves to the top of the bottom.

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What is the "it" that you are referring to? Are you, perhaps, seeing a line that is coming out of the top of the projector that ends up being projected on the ceiling? That is, you have the normal image being displayed on the wall, but you also have a line that is "leaking" out of the top of the scanner block? (Roughly 90 degrees from the normal projection direction?)

If that's what you've got, then yes, the problem is that your scanner mirrors are not wide enough to capture the full width of your lasers. This isn't a huge concern so long as the amount of red that is "spilling" off your scanner mirrors isn't excessive. Basically, if you still have enough red in your output to get a decent color balance, then as long as you have a lid on your projector it will block that line of red light that is coming out of the top of the scanner block. No one will ever see it.

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Should I have went with 5mm instead of 4 as it may have been easier to align?

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It's not so much an alignment problem as it is a beam diameter problem. People forget that the mirrors have to move through a range of angles. With the mirror at a 45 degree angle to the beam, you need a mirror that is at least 5.7 mm wide to capture the full width of a 4 mm beam. But as you rotate the mirror closer to horizontal, the required mirror width needed to capture the full beam increases dramatically. At 30 degrees you need an 8 mm mirror, and at 20 degrees you need an 11.7 mm mirror. And yes, each of these examples assumes an otherwise absolutely perfect alignment. Normally you want at least little wiggle-room beyond that point because perfect alignment is not easy!

Most scan systems have a max optical scan angle of around 60 degrees, which means the scanner mirrors need to move 30 degrees. That's +/- 15 degrees on either side of the perfect 45 degree middle point. So the worst case in this example is when the mirror is at the 30 degree point (that's 45 minus 15), and that means you need at least an 8 mm mirror if everything else is perfect in order to capture the entire width of the 4 mm beam. In practice, you probably want a 9 or 10 mm wide mirror to be on the safe side.

So yeah, if you had gone with 5 mm aperture mirrors you probably would have had an easier time. However, as I mentioned above, so long as you aren't losing a great deal of light you can live with the problem because the projector lid will block any part of the beam that spills off the scanner mirrors.

And again, all of this assumes that the "tails" problem you're describing is actually part of the beam spilling off the scanner mirrors and leaking vertically out of the scanner block to create a line on the ceiling. That's not "tails", that's spillage. If my understanding of your problem is incorrect, then please post additional pictures and we'll try to figure things out. ;)

Adam

I will try to do a better job explaining. The issue is only with the red laser. When single points are projected it is more pronounced and always manifests as a vertical line either to the bottom or the top of the point. If I move the scanners forward and backwards in the case this vertical line moved to the top or the bottom of the point. When complex visuals are displayed the lines dissapear as I am sure this is because the laser is not dwelling on a single bright point but is spread over a larger area?

I do have some spill off that shoots vertically, but the older scanners did this so I assumed it was probable these would too.

I belive that I only have two options (If my thoughts are correct about the mirrors being too small), precisely align the scanners in the center of the spill off or return the galvos for a 5mm set. The latter I really do not want to do as I would be wasting peoples time by not doing my own research from the beginning. I guess I just wanted to see if I was correct in my assumption.

A few curious questions... Is beam diameter correlated to beam power or is it pretty much just something you decide when purchasing a laser? So if I, for instance, wanted to purchase another red laser with a smaller beam diameter, would that be feasable? Probably will not do it, just curious.. Also, we had talked about laser amps, is there a site you could recommend buying from if I wanted to upgrade and are they something that can just be replace easily or do I have to match laser voltage etc.

Again, thanks for sticking with me and answering all of my newbie questions! I really do appreciate it.

Artifacts like that can be due to either issues with the collimation of the laser diode, or the near field alignment being off and the spot hitting the edge(s) of the galvo mirror (or the spot just being too big). If the artifacts look the same across the entire scan field, then it's almost certainly the first problem. It also just looks like beam artifacts from your photo.

Getting a nice beam out of diode lasers, especially multimodes, is tricky. The raw diode, despite being a laser, kinda just poops light like an LED, and you'll need a collimating lens to convert that poop into a nice beam. Due to fundamental limitations in optics, there is only so good you can make the beam, especially if you need to fit the whole diode and optical assembly in a reasonably-sized module or projector. There will almost always be a certain amount of spill from light that the collimator can't wrangle into the beam, which usually shows up as a faint glow around the spot, and sometimes the spot itself has little sticky-outy bits of higher intensity light from the main spot. The glow is usually not intense enough to notice in use, as you've seen, but human eyes have really good dynamic range and we can often perceive it when the spot is static. Because that that spill has a much higher divergence than the beam of interest, it drops off much more rapidly in intensity than the beam, so as you get farther from your projection surface it will be less visible.

Going to a larger set of mirrors on your galvos will help if your problem is that the spot is too big for what you have and the mirror edges are causing your trouble, but if the diode collimation is the problem, then bigger mirrors may actually give you more spill out the front and make things slightly worse, depending on what the beam characteristics actually look like. If the problem is your near field alignment causing the red to fall off the galvos while the G&B are centered, then ideally you want to fix your near field alignment. Going to bigger mirrors would of course help with that, but that's kind of a sledgehammer fix.

Beam diameter and divergence are linked by conservation of etendue. Basically, you can't reduce the spot size without commensurately increasing the divergence, and vice versa. Low divergence requirements necessarily implicate a large diameter requirement, all else being equal. But you may be able to find a red module (or a different correction strategy) that gives better results. It's hard to tell exactly how bad this sort of thing is from photos. Getting REALLY good beam quality generally requires shifting technologies, either going from multimode diode to single mode diode, or from direct injection diode to something else, but generally that sort of shift means giving up a lot of power or going way up in price--sometimes both.

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Originally Posted by jdavis7765

When single points are projected it is more pronounced and always manifests as a vertical line either to the bottom or the top of the point. If I move the scanners forward and backwards in the case this vertical line moved to the top or the bottom of the point.

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OK, that sounds like the beam is just barely spilling over the edge of the scanner mirror and the line artifacts you are seeing are caused by refraction as the beam spills off the edge. Moving the scanner block in or out changes the mirror edge that the beam spills off of, which is why the line flips from top to bottom.

There are a couple things you can do to fix this... For starters, larger scanner mirrors will help. But that's a lot of work to pull everything out and swap things, and you may still have some artifacts present due to the imperfect collimation of the red multi-mode diode. In my opinion a better option is to install a spacial filter.

Basically this is a pair of identical lenses in a keplerian collimator arrangement (so you have a focal point in the middle and no change in beam diameter from input to output) with a movable pinhole (that's the spacial filter) in the middle. As you move the pinhole from the focal point in the center to a position closer to the input lens you will progressively mask off more and more of the outer portions of the beam. This will allow you to clean up the beam profile to remove any artifacts and it will also reduce the beam diameter slightly before it hits your scanners. That way the beam fits more comfortably on the scanner mirrors and you don't have any stray artifacts. Once you find the sweet spot for the pinhole between the two lenses you can mount it permanently in that location.

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When complex visuals are displayed the lines disappear as I am sure this is because the laser is not dwelling on a single bright point but is spread over a larger area?

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Yeah - even a really messy beam will blend into a fairly uniform-looking line when the scanners are busing drawing lots of complex shapes. But if you are displaying a simple point (like a "hot beam" cue), any beam artifacts will be more apparent.

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Is beam diameter correlated to beam power or is it pretty much just something you decide when purchasing a laser?

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Tough question to answer, as there are lots of variables. For a given range of power there are really good (and expensive) lasers that have the best beam characteristics and there are cheaper lasers that have poor beam characteristics. But the power range has an effect as well, because once you transition into the multi-mode diodes there's only so much you can do no matter how much you spend on optics.

So while you might be able to get a 50 mw red beam in anything from 1 mm to 6 mm, if you want 2 watts of red the smallest beam you'll find is likely to be around 4 mm, if not more. Well, that's for direct-injection diodes anyway. Gas lasers, OPSL, and DPSS lasers are another story!

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So if I, for instance, wanted to purchase another red laser with a smaller beam diameter, would that be feasable?

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Do you know what the rated output power of your red laser is? I'm guessing it's somewhere between 200 mw and 500 mw... If so, then yes, you could probably purchase a replacement module that had a better (narrower) beam profile.

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we had talked about laser amps, is there a site you could recommend buying from if I wanted to upgrade and are they something that can just be replace easily or do I have to match laser voltage etc.

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Are we talking about laser diode drivers (the electronic circuit that powers the diode and controls the modulation), or scanner amps (which control the movement of the scanner mirrors and are matched to the individual scanners)?

If you mean replacement diode drivers there are several options, but many of the DIY folks here have nothing but good things to say about the BBE driver, which sells for under $30. As for matching the drivers to the diodes, there are two things to consider: 1) the supply voltage to the driver must be at least a volt or two higher than the forward voltage drop across the laser diode. 2) the max current output of the driver must be equal to or greater than the max current draw of the laser diode.

Normally the voltage supply isn't an issue when you are replacing drivers, since the existing driver should already have the appropriate supply voltage routed to it. As for the current rating, as long as you select a driver that is in the proper range you should be OK. So if the max laser current is 1 amp and all you have is a driver that goes up to 2 amps, you're still OK. I think the BBE driver comes in a few different current ranges - up to 500 ma for single mode diodes on the low end, and up to 2.5 or 4 amps for larger multi-mode diodes on the high end.

Note that at some point before you install the new driver you will need to look up (or measure) the max current of the existing driver with the modulation input at 100%. That way you can adjust the gain on the new driver so that 100% modulation input yields the same output current to the diode as before with the old driver. If you don't do this you could easily over-drive your diode and destroy it with the new driver.

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thanks for sticking with me and answering all of my newbie questions! I really do appreciate it.

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No sweat dude - that's what PhotonLexicon is for. ;)

Adam

Thank you for the reply buffo! I think I am plaugued with a few problems now. I was able to fix the red beam artifact by undoing one screw from galvo block and twisting a bit (I know this is a hack fix, but it works). I still have a little spill off, but nowhere near as bad as before. The other problem I noticed (which happens regardless of the galvo block being rotated or not) is the blue laser has a vertical rectangular shape to the beam so this spills off the first mirror is hits (y mirror?) causing a spill off on it. Not sure how I didnt notice before. Also, the blue laser light seems to be signifigantly fatter that green and red.

Buffo, you had mentioned using a keplerian collimator and a pin hole. Looks like this can be used to expand or contract a laser beam size, correct? Then the pinhole will only allow the laser to pass through and come out perfectly circular? Maybe this is a tough question to answer, but where exactly would I purchase this at? I found https://www.edmundoptics.com but seems like there are many things to pick through. Do you have any information that could help me decide what I need or is this fix sort of a custom solution?

To be honest I was thinking of taking the easy way out and purchasing an RGB collimated laser module, but then too I am worried about the specs I need to look for so the beam size would be compatible with my 4mm galvo mirrors. My mind is all over the place, ahhhh! lol Guess this is what I get for upgrading lasers instead of buying a good brand from the get go. I suppose I would not learn anything with the former. hehe

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Originally Posted by jdavis7765

the blue laser has a vertical rectangular shape to the beam so this spills off the first mirror

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This is a common beam profile for multi-mode diodes, especially the 445 nm blues. Basically the emitter is rectangular so you have two different divergence numbers, one for the narrow axis of the emitter and one for the wide axis. The narrow axis of the rectangular emitter will have the worst divergence. (Between 3x and 8x higher divergence than the wide axis of the emitter.)

Some lasers use a set of secondary optics to help tame this "fast" axis. The idea is to use a pair of cylindrical lenses or anamorphic prisms to expand the fast axis and then re-collimate it so it's close to the size of the other axis. By expanding the beam in only that one axis you reduce the divergence in only that one axis. So long as you position these secondary correction optics really close to the laser (before the narrow axis has diverged too much) you can widen the beam in that axis so it's close to the width of the the beam in the other axis. Then when you re-collimate that axis it should have close to the same divergence as the "slow" axis.

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the blue laser light seems to be signifigantly fatter that green and red

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As a general rule, the beams from the blue multi-mode diodes are fatter than the beams from the multi-mode greens and reds. However, you may want to check the primary collimation lens on your blue laser. If it is adjustable, it's possible that it has moved slightly from the optimal setting.

The primary collimation lens is usually just a standard AR-coated aspheric lens mounted in a threaded housing. If it is adjustable you should see either a slot on the lens holder or possibly a small hole near the edge that you can grab with a pointed pick. Rotating the threaded lens holder will move the lens in or out relative to the diode emitter which will change the focus. Try to get the smallest spot size you can at a distance of ~ 15 ft from the projector.

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Buffo, you had mentioned using a keplerian collimator and a pin hole. Looks like this can be used to expand or contract a laser beam size, correct?

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A Keplerian collimator can be used to expand or contract the beam diameter, yes. But in this application the idea is to use identical lenses on either end of the collimator so the output beam is identical to the input beam. The idea is not to change the beam diameter but to position a spacial filter (the pinhole) at the focal point in the middle between the two lenses. This allows you to "carve out" the center of the beam. And since the beam is converging to a point as it passes through the pinhole, any stray light that diffracts around the edge of the pinhole will spread out far enough that it will completely miss the second lens and thus will not be present in the output beam.

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Then the pinhole will only allow the laser to pass through and come out perfectly circular?

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Yes, exactly. I should point out that the pinhole is not really as small as a pin. It's just a small diameter hole that will only allow the center portion of the beam to pass. Normally the hole is made a bit larger than the beam diameter at the focal point. Then by moving the pinhole closer to the first lens (where the beam is still converging) you begin to filter out more and more of the outer edges of the beam. When you get to the beam profile you want, you lock the pinhole in that position.

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Maybe this is a tough question to answer, but where exactly would I purchase this at?

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You can buy the lenses from Edmund Optics, or Thorlabs, or any other supplier, but you will need to mount them and position them yourself. You'll also need a thin sheet of metal with a tiny hole in it that you will mount between the two lenses. The focal length you choose will determine how far the two lenses need to be positioned from each other (basically they will be twice the focal length apart). This lens has a 2 cm focal length (OK, technically 19 mm), so that gives you 4 cm between the pair. $70 for two of them. You could go with a shorter focal length, but alignment becomes more crucial as the distance between the lenses gets shorter and shorter, so I would not go shorter than 1 cm for the focal length (giving you a 2 cm gap to work with).

If you don't want to try to make your own mounts for the lenses then you'll need to buy those, which adds to the cost, but again any optics supplier can provide those. You can even buy the lenses already mounted in metal barrels to make them easier to mount if you want. The lenses should be identical positive lenses (plano-convex) that are AR coated for visible wavelengths with a diameter at least a couple mm wider than your beam width and with a focal length that, when doubled, will allow you enough room to position the pinhole in the middle while still fitting the whole mess somewhere in the beam path between the last dichro and the scanners inside your projector.

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is this fix sort of a custom solution

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Most definitely a custom solution! But it's not terribly expensive or difficult, and it will be a good learning experience.

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I was thinking of taking the easy way out and purchasing an RGB collimated laser module, but then too I am worried about the specs I need to look for so the beam size would be compatible with my 4mm galvo mirrors.

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Most commercial RGB modules list the beam diameter and divergence, so it's easy to make sure that whatever you buy will work with your scanners. Be sure to measure the width of your mirrors first though, because there is a big difference between a 4 mm wide mirror and a 4 mm *aperture* mirror. (Because the mirror is positioned at an angle to the beam the mirror must be wider than the beam to capture the whole beam.)

Adam

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Originally Posted by buffo

A Keplerian collimator can be used to expand or contract the beam diameter, yes. But in this application the idea is to use identical lenses on either end of the collimator so the output beam is identical to the input beam. The idea is not to change the beam diameter but to position a spacial filter (the pinhole) at the focal point in the middle between the two lenses. This allows you to "carve out" the center of the beam. And since the beam is converging to a point as it passes through the pinhole, any stray light that diffracts around the edge of the pinhole will spread out far enough that it will completely miss the second lens and thus will not be present in the output beam.

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So, if I am reading this right and understand correctly, there will be two identical lenses and the idea is to first make the beam diameter smaller with the first lens? Then you would carve out the beam with the "pinhole" and then the other lens is put at the other end after the pinhole to upconvert essentially, back to the original beam only with the pinhole having corrected the beam into a perfect circle? Ideally, would i do this for each individual laser or after the lasers have been combined?

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Originally Posted by buffo

Most commercial RGB modules list the beam diameter and divergence, so it's easy to make sure that whatever you buy will work with your scanners. Be sure to measure the width of your mirrors first though, because there is a big difference between a 4 mm wide mirror and a 4 mm *aperture* mirror. (Because the mirror is positioned at an angle to the beam the mirror must be wider than the beam to capture the whole beam.)

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So, I have the compact 506's 4mm. Say I were to go the route of buying collimated RGB laser module such as this for instance. Would it work? I am not sure I understand what it means showing the different beam sizes. Could that be for the distance from the laser?

Or, just for reference, this laser module am I looking at the 5.6mm as the beam size?

Thanks again!

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Originally Posted by jdavis7765

So, if I am reading this right and understand correctly, there will be two identical lenses and the idea is to first make the beam diameter smaller with the first lens?

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The first lens in a Keplerian collimator converges the beam (focuses it to a point), but beyond that focal point the beam begins to expand again. (The beam is now flipped in orientation, but that's not important.) When the beam has expanded back to it's original size, that's where you should position the second lens. That second lens re-collimates the beam so it's parallel again.

Thus you have a 1:1 collimator. It doesn't really do anything to the beam (apart from flipping it, which is only relevant if we were talking about an imaging system). The key is the focal point in the middle, as that is where we will position the pinhole spacial filter.

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Then you would carve out the beam with the "pinhole" and then the other lens is put at the other end after the pinhole to upconvert essentially, back to the original beam only with the pinhole having corrected the beam into a perfect circle?

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Yup! Exactly right.

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Ideally, would i do this for each individual laser or after the lasers have been combined?

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After all beams have been combined, but before the scanners.

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I have the compact 506's 4mm. Say I were to go the route of buying collimated RGB laser module such as this for instance. Would it work?

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The goldenstar module you linked to lists the beam width at the laser aperture as 2 mm by 5 mm. The 5 mm axis is too wide for your scanners. You can probably clean that up with a spacial filter (as described above), or just accept that you'll have a small amount of the beam spilling off the scanner mirrors when you scan wider than 45 degrees.

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I am not sure I understand what it means showing the different beam sizes. Could that be for the distance from the laser?

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Yes, the "at aperture" measurement is beam width and height at the output of the laser module. The rest of the measurements are at 5 meters away, 10 meters away, and 15 meters away from the output window of the laser module. The beam gets bigger due to divergence. :) Also, there are two beam width measurements because the module uses multi-mode diodes with rectangular beam profiles. (See fast and slow axis explanation above.)

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Or, just for reference, this laser module am I looking at the 5.6mm as the beam size?

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No. On that website they are talking about the physical size of the diode module itself. 5.6 mm is a common diode can size. 9 mm is another common diode can size. Neither of these two measurements have anything to do with the size of the output beam.

When buying a bare diode you need to know the size of the diode can (basically the diameter of the can) so you can purchase the same size diode module to mount the diode in. This often gets confusing, because the module will have two sizes listed: One is for the diode can diameter and the other is for the total outside diameter of the module. Typical outside diameters for modules on DTR's site are 12 mm, 20 mm, and 25 mm.

Adam

So I purchased the lenses from edmunds and will be giving this a try. I also found these lens holders for 3d printing. Not sure how well they will work or even if the optic will fit but I am sure I can rig something up or also take up CAD as another hobby haha. :) I will follow up here when they arrive!

Thanks for the help, not sure I would be anywhere with this if it wasn't for this forum!

Wow! Those 3D printed lens holders look great! If you can make those you'll have no trouble building the collimator. :)

Adam

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Originally Posted by buffo

Wow! Those 3D printed lens holders look great! If you can make those you'll have no trouble building the collimator. :)

Adam

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Printing one now to see how it looks. Looks like you can even customize for different lens sizes. Also, looks like Edmunds is in NJ and I am in PA. Ordered the optics yesterday and they will be here today. That was fast!

So, I have a question about this. First things first, lenses have arrived and man they are smaller than I thought (damnit to America for not using metric system). Anyway, the lenses are flat on one side and convex on the other. Does the laser go into the flat side of first lens, then out the convex side moving toward the second lens which would be into the flat side then out the convex side?

Also, do the lenses have to be exactly oriented (not sure of the correct way to say this) so the laser enters the exact center or is there a little wiggle room?

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Originally Posted by jdavis7765

Does the laser go into the flat side of first lens, then out the convex side moving toward the second lens which would be into the flat side then out the convex side?

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Nope - exactly the opposite. Put the flat faces towards the middle of the collimator (towards the focal point in the center). The convex faces should be facing the outside. (It *will* work the other way, but you'll get more reflection off that flat surface if it's facing outward, and you don't want that.)

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do the lenses have to be exactly oriented (not sure of the correct way to say this) so the laser enters the exact center or is there a little wiggle room?

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It depends on the diameter of the lenses compared to the diameter of the beam. You mentioned that the lenses were very small though. This suggests that you will not have a lot of "wiggle room". Try to get the beam to hit the dead center of the lens. If you are off, you'll notice that the output beam will not have the same shape as the input beam.

Adam

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Originally Posted by buffo

Nope - exactly the opposite. Put the flat faces towards the middle of the collimator (towards the focal point in the center). The convex faces should be facing the outside. (It *will* work the other way, but you'll get more reflection off that flat surface if it's facing outward, and you don't want that.)



It depends on the diameter of the lenses compared to the diameter of the beam. You mentioned that the lenses were very small though. This suggests that you will not have a lot of "wiggle room". Try to get the beam to hit the dead center of the lens. If you are off, you'll notice that the output beam will not have the same shape as the input beam.

Adam

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That makes sense! Is the idea here that you could hit the optic (not exactly straight on) and it will still be able to shape the beam out the flat side a little better?

I got the optics holders printed and designed my own rail (its not the greatest) to keep then more aligned. I need to figure out how to adjust small increments a little better though. A lot more difficult than I imagined it to be, but here I am lol. Ill post back when (if) I get it setup. lol

Thanks again,

Jeremy

Believe it or not but even with 500mw laser you can punch your own pinholes in aluminum foil. I’ve also used guitar picks. Remember the best place to put the pinhole is slightly forward or back of the focus. I tend to burn the hole then move the first lens forward a tiny.

ive also done it after the dichros combine the beams. Just need to use the right achromatic lens set. One pinhole.

use a worm gear to move the lens. I’ve used threaded rod too. Those cnc rail mounts are cheap on eBay. I get the 12mm ones. Use them for your diodes too and consistent beam height.

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Originally Posted by jdavis7765

Is the idea here that you could hit the optic (not exactly straight on) and it will still be able to shape the beam out the flat side a little better?

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No, the lens will perform equally well in either orientation. But having the incident beam hitting the flat surface directly parallel to it is the ideal case for back-reflection, which can harm the laser diode source if the anti-reflection coating on the lens is not up to the challenge. So you want to avoid that if at all possible. (Admittedly this is more of a risk with single-mode diodes though; most modern multi-mode diodes are remarkably robust by comparison, even if their beam quality is nowhere near as good.)

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I got the optics holders printed and designed my own rail (its not the greatest) to keep then more aligned.

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I admire your dedication to the do-it-yourself ethic, but if you get really stuck you might want to consider using one of the commercial mounts that Mark suggested above. Worst case, maybe you use one of your mounts for the fixed lens and then a commercial one with fine adjustments to tweak the final alignment. :)

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Originally Posted by kecked

Believe it or not but even with 500mw laser you can punch your own pinholes in aluminum foil.

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I hadn't considered using aluminum foil, but this is a great suggestion! The beam artifacts at the periphery of the beam will be much lower in power than the center of the beam, so the aluminum foil will easily mask that while allowing the main power in the center to punch a nice clean hole.

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the best place to put the pinhole is slightly forward or back of the focus.

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I've seen people start with a pinhole that is much wider than the beam waist at the focal point and then move the pinhole closer and closer to the first (incident) lens until the pinhole begins "carving out" the outside edges of the beam. When you get an acceptable output beam, that's where you lock the pinhole in position...

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use a worm gear to move the lens. I’ve used threaded rod too. Those cnc rail mounts are cheap on eBay.

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I bought a set of linear translation optical stages off E-bay years ago for exactly this sort of project. But I ended up paying quite a bit for those units, even though they were used and the price was marked down a lot. (I think I paid around $150 each? Retail was over $400.) So yeah, if you have a source for a linear translation stage that is more affordable, please share!

Adam

Alright, still working on this and wanted to post my progress! I actually made this from scratch in Fusion 360 and after many versions it is coming together. Still needs more work, but the idea is that the lens holders are pretty much a single piece with threads I split in two that has a spot for 6mm lens. Still need to work out the holder for it though.

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