K132 mod for a new user

[mading]

Dear community,

I had a look at the old david forum, I'm looking for high quality hardware to create my own SL two-camera system.

I'm going to scan objects from 0,05 to 0,5 meter.

I would like to share my hardware's choice:

1 acer K132 modded as: DAVID-Laserscanner Forum • View topic - Projector/Camera advice

2 DMK 23UX236

2 Pentax H1214-M (0.25 MOD)

Has computar M1214-2Mp any advantages over the H1214, when working with 5x5 cm objects?

Is there any upgraded topics on additional lenses for K132? I found:

http://www.thingiverse.com/thing:1025011

https://www.shapeways.com/product/HR2Y65L8A/acer-k132-lens-adapter-v0-91a

[Curiousjeff]

If your budgets allows,  I would get a superior projector without diamond shape pixels, like the one Micr0 has recommended.

[avogra]

Hi mading,

I almost use your suggested setup but with different lenses, the computar M1214-mp. But I think the Pentax should be fine.

One issue I have with that setup: The field of view of the K132 doesn't exactly fit the field of view of the cameras with the 12mm lenses. At the same distance, the projected image is a bit larger than what the cameras see. You want the camera to see a bit more than the projection. Has anybody else the same issue?

Before the Acer K132, I had an Acer K11, which has a more narrow image at a given distance (projection ratio 2:1 vs. 1,5:1). Here, the combination is perfect. With the K132, i think that a 10mm lens would be better. No idea what they actually ship with the official hardware. Or maybe they have modded the projector for a smaller image?

About the suggested mods for smaller minimum projection: only use achromats! Those cheap close-up lenses bring you lots of chromatic abberations and distortion. But even the achromats mean a bit of distortion. The even better alternative is to modify the projector, so that the lens barrel is moved a little bit outwards. The downside is that it will reduce the maximum image size. If you don't want to use it for general projection, this doesn't matter. I only did this with my old K11. I designed a special spacer which moves the internal lens by 1mm, which is enough to reduce the minimum size to 50%. If I want even smaller projection, I use a weak achromat on top. I didn't dare yet to open the K132.

About the projector: Some are very happy with an LG PF1500. I understood that is has not only far better resolution but also square pixels that are much better than the diamond shaped ones that are used in almost any projector with 1280x720px.

And for the moment, I would save the money for a second camera and lens. No idea if somebody else had more luck, but for me, using 2 cameras doesn't work out very good. If you browse through the forum, you can find more posts about it. Maybe you are pleased with a single cam setup anyway? You can still buy a second set later.

Good luck 🙂

[mading]

Thanks!

So you suggest the LG PF1500G?

What kind of focal length better couple with the projector, when using a 1/2.8" sensor as the 23UX236?

[avogra]

Yes, the LG PF1500 seems to be a very good solution. Micr0 is doing amazing scans and to my knowledge he uses the LG: Link

About the lenses: I didn't hear from anybody else having problems with field of view. No idea if the error is at my side. I think something like 10mm, maybe even 8mm would be a better fit.

At the moment I try to find a way to make the K132 a bit more tele instead. When scanning small objects, you quickly come to the point, where the beamer is in the way of the cameras and everything becomes fiddly and awkward.

So at the moment no clear recommendation from me 😕

[micr0]

I am using the LG and it's been great. However! If you are wanting to scan very small subjects the LG may not be a good choice for the a couple of reasons.

It is big (ish). Even though it is very small for a 1080p projector with 1400 lumens it is big for scanning the very small stuff. I use an Optoma ml 550 for things smaller than 70mm. With the LG the cameras can't be brought in close enough to the projection source to give good camera angle.

Another problem is that it is bright. You will need neutral Density filters to keep the projected image from over exposing the subject. Without ND filters, even with the lenses stopped down to F22 it can be too bright. Also stopping a lens all the way down introduces other problems with David.

[Silver_Ghost]

Ok, here is a custom focusing lever for the modification of acer's K130 family described above. It fit's perfecly and allows to get focus at closer distances.

[mading]

Hi Silver_ghost: Nice work!

thanks to Micr0 for kind replies.

I subscribed to 3dscanforum, I'm looking forwar for the administrator response.

[avogra]

Your account should already be activated. Did you get no notification?