Best practise: displaying many circles

[Nagilo]

I'm creating my own ILDA frame with a small app. So, what I do is creating a circle and replicating this circle in different pattern. The picture shows 16 circle in a line. I can change the number of circles per line; the number of lines and the number of points per circle. I need to figure out how many I can display at maximum until the frame rate gets too slow and the picture flickers. Currently not more than 30-40 are possible which results in a frame of 700 to 1000 points displayed at 30k PPS.

So, my question is if there is any strategy to increase that number or how to change the construction/design of the ILDA frame.

Thanks, Matthias

[mixedgas]

For older scanners at 30K, 750 to 1000 points was the recommended max count of points for a un-optimized image at small angles such as 8 degrees. You can add velocity, anchor and guide points to that line you have between the circles, the hot spot is the connecting line causing slow entry into circle. You can reduce the scan angle to trade angle for speed. You can create polygons with small numbers of points and scan them at the speed limit like the circle in the square in the ILDA test pattern. The last is bad practice because it reduces the ability to send the files to other users. You can use a optimization program such as ILD-SOS or Laserboy to clean up the file. Laserboy is open source, so if you give James credit, you may look at the code.

Your immediate goal is to reduce the number of points per circle and guide the scanners in between circles to optimize velocity using blanked points. The fastest distance between two vector locations is to maximally accelerate to half way there, then maximally break to a stop. For small jumps from point to point the galvo amp does that for you. For large jumps from object to object, you need optimization along the way. However you do not want to fully stop at the beginning and end points to the circle, so you need to adjust velocity as you enter the next circle.

If your into math you can look at the nearest neighbor and traveling salesman problems. As you do not have sharp corners, your looking for a means of reducing points.

Steve

[Galvonaut]

Out of interest Steve, would you make the hot-spots blanked points (plus additional blanked points?) to reduce the dwell time if you were trying to get rid of those, rather than what Nagilo is looking to do?

Keith

[mixedgas]

Out of interest Steve, would you make the hot-spots blanked points (plus additional blanked points?) to reduce the dwell time if you were trying to get rid of those, rather than what Nagilo is looking to do?

Keith

Blanked points are still scanned by definition, so I would not add unless needed. If doing this by hand, I'd blank the retrace lines between circles unless that is intended. But I would add guide points or velocity points to the retrace while reducing points in the circles. If the between circles retrace has more then 4-5 points, something is wrong. I don't know how his display DAC hardware handles points, if it is a low cost SD card player he may need to "Pull" points by hand to make the image look good. On the other hand, if he were using LSX or Pangolin, we would not be having this discussion.

See where his long back retrace is fast but distorted? That is going to overshoot as it reaches the first circle, there goes three to five point times right there. One velocity or Anchor point there may buy him four or more points elsewhere.

Preventing the "Pulling" of points by hand was one of the reasons for developing the ILDA standard tuning.

Steve

[james]

What DAC and display system are you using?

30 or 40 little circles like that is actually pretty good. That's a fair amount of detail.

When it comes to the number of points in an ILDA frame, the DAC clock (points per second) is absolutely important.

Here's a neat little animation with circles:

http://laserboy.org/free_art/every_byte.zip

I guess this needs to be optimized though... There are no span points in the blanking path, which was a big part of your original question.

That's something that you will run into again. There are different ideas as to what goes into an ILDA file and why.

One idea is to just store the minimum number of points to properly convey the image and leave it up to the display application to add the optimization points.

Other situations require the frames to be as optimized as possible (in file) for systems that have no ability to optimize the frames as they are displayed.

James.

[Nagilo]

Thanks everybody for the detailed discussion.

I'm using the black USB box from Moncha as DAC (30kpps max.) and a 520nm green LED-Laser from Kvant. So the hardware is quite good.

I create the ILDA frame on my own following simple math. But you are right, currently I'm not adding blanking points in the line between the circles. That's why the long way back looks wrong and also the entrance in the next circle is not perfect.

Matthias