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Thread: bare bonz laser projector

  1. #11
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    It will be outdoor and low-level light. It will be a tool for sign painters. The reason why I want direct control is that I want to draw a square. (for example) A square will by obtuse when projected onto the wall. However, because I'm a draftsman, I can draw an obtuse square. It will then become square when projected on the wall.

    They don't have to be csv files spacifically. They can be ascii. In either case, I'll probably have a program written that will compensate the values. For example. I'm not 100% square when I shine on the wall. I'm oblique by 5 degrees right and 30 degrees too low.


    Thanks for your offer. I'd love to be paired up with someone and try out their projector. However, I'm in Brisbane Australia.

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    The fact you want to use it for sign painters causes a whole host of other issues, namely safety. Pretty much unless you want a whole load of safety issues, you're going to be limited to below 5mw output. Green is the most visible colour.

    You're also probably going to have to self build the laser as lasers in the 5mw range are usually toys with very poor slow quality stepper motors instead of galvos.

    You also need to check local laser regulations as you're proposing both outside and commercial usage both of which can trigger a whole host of further regulatory requirements.

  3. #13
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    Quote Originally Posted by chris64 View Post
    The reason why I want direct control is that I want to draw a square. (for example) A square will by obtuse when projected onto the wall. However, because I'm a draftsman, I can draw an obtuse square. It will then become square when projected on the wall.
    This is where a little bit of knowledge becomes a problem. You are clever enough to recognize the need for geometric correction of the projected image, but are unaware that most commercial laser software includes geometric correction as a standard feature. That's why people are asking for more information. It makes it easier to recommend a solution if we understand the entire problem.

    For the record, what you're proposing (using an image projected from a laser projector as an outline guide to aid in painting shapes, or to align posters prior to gluing them down on a billboard, etc) is something that other companies are already doing. And with the right prep work (read: the proper frame files, and the knowledge of how to set up the projection zone and apply geometric correction), it works quite well and *can* be very effective.

    However, in many cases it would be easier to use a video projector in place of the laser projector. Video projectors don't pose an eye-exposure hazard like a laser projector does. Also, video projectors don't suffer from image flicker when trying to display a complex pattern of lines or shapes. Since laser projectors have to physically move tiny mirrors back and fourth to draw the image, there is a limit to how many times a given frame can be drawn per second. More complex frames yield lower frame rates, which can cause flicker. Also, you'll have many more software solutions to choose from if you use a video projector.

    The cases where the laser projector is the superior choice include very large surfaces (hundreds to thousands of square feet range), or surfaces that must be worked on while already brightly illuminated (eg: sunlight), or cases where the projector must be located a long distance away from the display surface. If your application falls into one of these broad categories, then yeah, it's worth looking into a laser projector and some basic software. But if you can get away with a video projector instead, you'll have far fewer hoops to jump through. (And it will probably be cheaper as well.)

    I'd love to be paired up with someone and try out their projector. However, I'm in Brisbane Australia.
    There are a few PhotonLexicon members in Australia who may be able to help. Alternately, you could contact a commercial laserist directly, but that could get expensive fast. At a minimum you'd want to do a "proof of concept" before you bought anything, and of course eye-safety absolutely must be at the forefront of any endeavor involving a laser projector. However, if the laser projector does turn out to be the best solution for you, know that this is basically a solved problem. Just keep in mind that lasers are also going to be the most expensive way of doing this...

    Adam

  4. #14
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    Chris, drop me a PM, I'm not just an entertainment person.
    ~
    I've done this as a sub-contractor on a project for a very large bank, where we had to project the new sign from 16 stories up, from an adjacent building. We used off the shelf software, but there are a few careful considerations to the type of laser used and galvanometer scanner used, as well as the control hardware. The CEO of the bank then overflew the building in a helicopter to choose which of the three sign options he preferred. We did this over several nights, and if things changed in size or position, it was damn obvious.
    We also did it on a sunny evening in New York City, and I'm damn sure I could have never done that with anything but the most expensive large video projector, whereas the laser projector used cost about twenty grand. Compared to the greater then ten million Dollar cost of the final sign project, a laser preview with exact scaling was cheap.
    ~
    We used existing points on the building as fiducial marks and then transitioned the image to the correct spot, under the guidance of documents prepared by the sign designers and architects. The built in geo correction in the entertainment software easily corrects for complex curved surfaces, tangent distortion from the galvos at wide scan angles, image size issues, pincushion, barrel, etc. You literally project some test patterns, then drag the corrections in with a mouse. We could then drag that around the building to satisfy the customer, who was very picky about their logo, right down to matching the Pantone Colors as close as possible. If I had to do it again, there would be a few subtle, inexpensive things I'd add to the hardware.
    ~
    I also have a few of the carbon fiber layup machines using scanned lasers to align parts to 0.1 mm over a range of twenty feet. I bought them used (three for three hundred Dollars, minus the software) to obtain the high accuracy scanner amplifiers. There are a few small differences between what is in them, and entertainment projectors. Basically there is a subtle difference in the circuit of the scanner amplifier that drives the galvos, plus ultra stable voltage references, compared to the references used in most entertainment grade scanner amps. There is a trick to the initial alignment, using a easy to build widget to find the initial position on the table (or side of building) , so you can come back day after day and hit the same alignment. You can even take down the gear for the evening and come back and hit the same marks within less then one half of one percent of final image size.
    ~
    I can fill you in on the details. The hardware is available off the shelf, both new and used. Since your down under, and I'm up here in the North, your not a competitor and I'd be glad to spill the beans. I know a few of the laser guys in Oz, we've attended conferences together. Let me see if my friend knows a guy in your neck of the woods.
    ~
    The gear is off the shelf, cheap used, and with the right choices, easy to build yourself.
    ~
    I've also used the rectification software for aligning and correcting multiple video projectors on curved surfaces, for large scale flight simulation, and if I had my choice between vector based laser or dealing with the jaggies and lens distortion from video, I'd rather go laser. Basic video edge blending and distortion correction software using off the shelf video projectors starts at 450-750 USD depending on options. Again, the concept is project a grid, measure it, and drag the corrections in with a mouse or enter correction factors manually. The price of a good projector with interchangeable lenses starts getting comparable with lasers. Video has the advantage of no flicker, but gets exponentially expensive for laying out very large images, in which case you start needing a lot of video projectors. While in full room light/day light you may be projecting only part of the image at a time with a eye safe laser, you can come back and hit the same location very accurately, day after day. Whereas moving the video projector back and adjusting the lens may not be so easy on a wall sized project. But video does have its uses, and if you understand how both methods work, you can pick which is best for a given application.
    ~
    With the right software, you could also do "follow the dot" and trace with a pencil in full blown daylight with next to nothing in laser power.
    ~
    For very large distances, (tens of meters) the position sensor and DAC voltage reference chips start to matter, two brands of galvo and one brand of control hardware actually bothered to think this through. The Chinese clone stuff often uses a 7805 as the position sensor reference, and you can bet that one drifts a bit over an evening of large scale scanning.
    ~
    For those PLers who have not thought this out, think DPSS or Gas laser with guaranteed tem00 beam, capacitive position sensor vs optical butterfly, and a means to accurately compensate for the step size of the DAC not lining up with the desired size of the final image, without loosing image resolution by using the DACs for image size. So you do NOT use the software to set final image size, but use external potentiometers. Outdoors for very, very large projections, think more then one scan head and keeping the galvo shell at constant temperature.
    ~
    Beware of cheap projectors with eight bit resolution SD card readers for this application. 1 part in 256 from a SD card reader does not cut the mustard. 12 Bit resolution is 1 part in 4096, much better, and 16 bit resolution is available.
    ~
    You can also do this using a laser or optical theodolite to place templates, then pounce the outline in the classic way. This very curvy beast is based a few kilometers from my house, and here is a video of a local company using laser guided masking placement for her paint job. I had nothing to do with this project, but it made the local newspaper. All three new ships look identical, the three older ships always had subtle differences in marking and cheat line placement. Note they never show the alignment process, just the results. She's 246 foot long, and very curvy.
    ~
    https://vimeo.com/95537465
    ~,

    Again, what is your Budget Chris? You can start at about 1000$ with a mix of new and used parts and work your way up. Most of that would be choosing a good program and control hardware with real time Geo-correction.

    Steve
    Last edited by mixedgas; 05-30-2017 at 06:57.
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    I draw human sundials. It's an analemmatic sundial of a large scale. (about 5.5 meters x 3.5 meters) You stand on the month on the date calendar. You're own shadow points to the time of the day. They're popular in gardens and landscaping but hard to construct accurately.

    That's why I want to draw on a cheap camping tarp 6x4 meters. The landscaper will then use this as a template to accuratly place the paving blocks.

    https://www.youtube.com/watch?v=kZsUTCGA-pw

    Ignore the kids activity of constructing this sundial. (measured it out manually as a learning tool) It didn't sell well because teachers were intimidated that it would be too complicated.

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    That just cries out for a small laser. That we can do.
    I was taught to make a crude one of those to find time and/or direction if lost, in Boy Scouts. But determining high noon on two consecutive days burns a day's ration of water if your lost.
    ~
    The same source laser, with an additional mirror mount on a long arm, lets you do a co-incidence rangefinder, tying in the basic trig. Ie overlap two laser spots to set your central distances. It will take some thinking, but your project is very "do-able"
    ~
    You can also skip the scanners and computer with some thought, using a laser, a beamsplitter with the co-incidence rangefinder, a rotary mirror with an angle readout, and some pegs for marking the locations. Do the whole thing by geometry. I suspect that would result in frustrated teachers, trying to explain all that layout in a 45 minute class period. However, I'm trained as a teacher, and right now I'm a Senior Technician at a major university, also working on a Masters in Adult Education. I understand what your trying to do. Laser shows led to lab lasers and other things, although I still do the odd laser show, now and then.
    ~
    OK Boys and Girls, we'll go with a TeM00 mode green DPSS at 532, a scan pair, a few optics to do some beam splitting, and something where we can get the frame refresh rate down to near DC, to optimize use of a license free Class IIA or Class IIIA laser in a bright sun light. For older children, he can turn up the laser power to the low end of IIIB. I actually thought of just using the galvo pair with a voltmeter to mark the locations with a dot, without even a computer, but I suspect that takes the "fun" and "interesting" out of the learning experience. (Well, unless your a serious math Geek)
    '
    This just went from a show projector to a learning tool, and maybe down the road he could use RGB.
    `
    I just contacted one of my two friends in OZ, lets see what happens.
    '

    Steve
    Last edited by mixedgas; 05-30-2017 at 17:00.
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  7. #17
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    You misunderstood.

    I already made a progam that designs this. I input on a spreadsheet the latitude and longitude. It produces all of the x and y cordinates. I have several programs. One on these programs will read this data on a csv or ascii file and will draw it in cad. I'd like to do the same to a laser projector.

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    My sundials are very accurate. I made a miniature one and used a metal pole for the shadow casting device. I made a 365-day calendar for it. I drew it on cad and laminated the paper for outdoor use. The only inaccuracy is that I used a math formula that took the leap year average. (each day was off by a few seconds) This dial was accurate to within under 1 minute.

    However, landscapers are not very accurate. They often make my dial accurate to within 1 hour.

  9. #19
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    Quote Originally Posted by chris64 View Post
    You misunderstood.

    I already made a progam that designs this. I input on a spreadsheet the latitude and longitude. It produces all of the x and y co-ordinates. I have several programs. One on these programs will read this data on a csv or ascii file and will draw it in cad. I'd like to do the same to a laser projector.
    Put simply they're trying to tell you, you can't. Not directly anyway. Laser programs don't simply take eg 4 co-ordinates and draw a perfect square. There's a lot more to it than that as the number of points affects the brightness and depending on the complexity, there may even be a need to pay someone (such as Pieter on here) to optimise a design so it scans ballistically in which case some points can be completely outside of the drawn area. Lasers also require blanked points (points that exist and connect areas but aren't actually projected in the final cue). A laser cue isn't simply made up of what you see.

    Here's a logo cue taken from Beyond:

    It looks like this in the preview window (which is what you'll see when projected):




    But in the cue Editor, you can see there are blanked points outside of the design that correspond to the beam path the laser must take when drawing the logo - these are the grey points in the middle of logo's gaps (one of which I've highlighted with a green arrow for clarity):



    In my opinion, the easiest way to project a sundial would be to either output it from a drawing program in an extension a laser program's drawing program understands so it can simply be imported and converted into a cue, or alternatively save the design as a bitmap or jpeg and then trace the design into a cue and then you can simply project it and use the software controls to control the size and correct the geometry. One word of warning here, tracing software likes very thin lines and high contrast, - thick lines can be doubled up so, so output as something like black on white and use thin lines.

    As for using tarp, can't really see the point (!) - those cheap nylon based tarps will reflect the light back into the face of anyone attempting to cut it out. Not necessarily dangerous if the laser is low powered but the brightness can be uncomfortable. Why not simply project straight onto the ground and let the gardener place the blocks directly on the laser lines? Much more accurate as well. The latter does require an eye safe laser though and may cause you to have to comply with some local laws regarding outside projection. If you're projecting onto grass (which is green obviously!) then a red laser may be better although a lot less visible. If projecting onto soil or concrete, I'd stick with going green due the visibility. However, the colour visibility issue eg green on green or red in daylight, may be less of a concern if working after dusk or before dawn, which seems to be the hint from what you said about low light.

    If you must make a physical template and intent to keep the laser for "factory use", then I'd suggest projecting onto canvas tarp. It will be far less reflective, if heavier. There is a small fire risk with lasers, but again not at the powers you're talking especially if the beam is modulated.

  10. #20
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    What Whitelight is trying to tell you about is the "rectification" step, which is done with math in software and hardware. The laser scanner, while incredibly precise, has two issues. Unless the scan head is located exactly perpendicular to the surface it's scanning on, you need some mathematic corrections that are difficult to do in a spreadsheet. They are difficult because every time you change the size of the projected image, the math needs done again for every point in the image. Next the moving mirrors have inertia, they will briefly overshoot and/or undershoot when sent to a new position. We only turn the laser on when the control electronics and software "know" the moving dot is in the right spot.
    ~
    The scanner drive amplifiers are typically calibrated to move 5 mechanical degrees per volt of signal input. Due to the geometry of mirrors, 5 degrees mechanical deflection becomes 10 degrees of optical deflection once the beam bounces off the mirror. The optical angle is always twice the mechanical angle. We control them by generating voltages with a computer. You can also manually position them, if you just want to project to a location in a 2D plane space, but not generate an image.

    ~
    The scanners are Ballistic, when moving fast enough for persistence of vision to kick in, so the viewer sees lines and curves, not just a dot of laser light. For the laser image not to flicker, it must scan at least 15 times a second, and we usually shoot for 30 refreshes a second. When moving rapidly, the scanners overshoot by a few percent, and settle to position literally thousands of times a second, getting a control signal from the computer at 30,000 position signal per second (30K PPS). So the computer pre-computes the corrections and applies them to the image.
    ~
    The scanner amplifier takes the control signal from the computer, which is a DC to audio waveform. It looks at a position sensor on the mirror shaft and computes a proportional signal, an integral, and a differential spike, scales these signals, and uses them to correct the mirror position in about 12 microseconds on a 30K PPS scan pair. Lots of math, and modern systems let you totally ignore doing it manually. If you don't have the system do the math, you see a blob of light at every point in the image until the mirror position settles.
    ~
    IF your not projecting an image, and just slowly and precisely positioning the laser beam, such as is done in laser cutting, then you could work from a CSV file, wait for the scanners to settle to your new beam location, mark the location of a dot using a pencil, and move to the next co-ordinate, very precisely. You would still need to compensate if the scan head is off axis, using some serious trigonometry. This can take hours to set up. Which is why both the machine tool industry and laser show industry, and now the medical people, have moved to software control of everything. Its cheap, its very, very, accurate, and you can move the laser much faster.
    ~
    Its a lot more fun and useful if you scan the image and let the real time software correct the image, which it does to an amazing level of accuracy.
    ~
    In the old days, when we used analog computers (universal geometric corrector) to correct for any distortion, it took an hour or two hours to set up the corrections and get ready. But we were really limited in changing the size and position of the image. Customers could never understand why we needed at least four to six hours to set up for a simple laser show. Now we do that in about 30 minutes, of which maybe five is setting up the software image correction. Its accurate enough that you would need a theodolite to measure the error in what the eye sees, once trimmed.
    ~
    The way you want to do this is stuck in the 1970s, its cumbersome, difficult, and very slow. From an onlooker's point of view, its maddening. I started out doing it that way in the late 1980s. We call it "Pulling Points", when you manually correct for any issues. What "pulling points" did, was prevent users from interchanging data from system to system. You could only ensure a good image at ONE location.
    ~
    Let the computer import the CSV and trust twenty five years of software and hardware development. You still have ways to correct for any errors from the size and offset control screen, artistic editor, and geometric correction screens. You can still grab any point of light that is "out of position" with a mouse or arrow keys, and move it manually. The computer will spit out a location of where each point is, and you can then run that through a spreadsheet and convert to degrees, centimeters, whatever.
    ~

    OK, part II with pictures in a minute..

    Steve
    Last edited by mixedgas; 05-31-2017 at 10:25.
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