DLP Projector lenses - is hacking throw ratio possible?

[mading]

I would like to start a discussion regarding projectors.
Cameras and lenses are quite easy to find, they work out of the box.
They have a variety of features, pros and cons.

Consumer DLP/LCD/Laser/LED/Halogen... projector are used most of the times without modifications.
Lenses are often the weak ring in the chain, and probably the hardest to mod.
(yes: color wheel, kind of light source, etc.. all have their impact).

But the biggest issue I have found is the fixed throw ratio, too long minimum focus distance, poor focus and lens quality, etc...

I got the idea to start this thread following a discussion that started in a Micr0 thread:
https://www.3dscanforum.org/viewtopic.p ... 3&start=10

My wish: to add a tele zoom to my LGPF50KS or a PF1500 I can use to create a multi-FVO (with 3 lenses: 12-16-25 mm) scanner.
Something like the RangeVisionPro (which I suppose is using a zoom projector lens) or HDI Advance (which I don't).
As an alternative, I will consider using three lenses for the projector.
This will help (if I am not in mistake) keeping a similar camera distance and reducing the scanner dimensions.

Polyga is selling a development scanner that uses a TI DLP projector:
https://www.polyga.com/evm-3d-scanner-kit/

People watching films often looks for the opposite: reducing throw ratio:
https://www.avsforum.com/threads/wide-a ... or.378751/
https://www.instructables.com/Turn-a-Re ... hrow-Mode/
(notice the distorsion when usins additional lenses)

So if anybody has good thought based on optical theory and experience, the community of DIY will thank you!

[OBNRacerMan]

I've tried using a regular "third-hand" lens.

My "third-hand" lens :-)

From a distance of 300mm, my projector produced a projection size of 230x130mm (as native size).

Distance 300mm, no lens, size 230x130mm

With this lens (from the same distance), the projection size was 150x90mm (which is almost twice the size without the lens (80x50mm) at a projection distance of 100mm). But with the lens there are problems with geometric distortions (but I think that they can be reduced somewhat by using a lens of a larger diameter).

Distance 300mm, with lens, size 150x90mm

P.S. The main problem is the selection of lenses ... unfortunately, I do not have familiar opticians who have the necessary knowledge and formulas ... so I have to experiment with everything that falls into my hands

[Alonso]

It's just physics and a little bit of math!

[mading]

An under 1k projector will be very interesting.

I was looking at Texas Instruments evaluation boards:
https://www.ti.com/dlp-chip/display-and ... arted.html
that's very informative.

A few evaluation board availables!
https://www.ti.com/dlp-chip/display-and ... pment.html

That's an example around 1K.
I don't understand if the optics can be changed.
https://www.digikey.it/product-detail/i ... ND/7219324

[mading]

It's just physics and a little bit of math!

feel free to contribute with your own equations!

[mading]

Yes!
A turnaround for getting smaller FOV.
Somebody just moved the lens far from the DLP to get a smaller FOV for DLP resin printing:

https://packet39.com/blog/2016/02/03/mo ... d-printer/

[Micr0]

Yes!
A turnaround for getting smaller FOV.
Somebody just moved the lens far from the DLP to get a smaller FOV for DLP resin printing:
Minimum FOV.jpg

https://packet39.com/blog/2016/02/03/mo ... d-printer/

The key here is finding a projector that you can get to the lens mounts without having to take anything else apart. This seems to be easier on older bigger projectors.

[Micr0]

I've tried using a regular "third-hand" lens.
IMG_20210129_225036s.jpg

From a distance of 300mm, my projector produced a projection size of 230x130mm (as native size).
IMG_20210129_224558s.jpg

With this lens (from the same distance), the projection size was 150x90mm (which is almost twice the size without the lens (80x50mm) at a projection distance of 100mm). But with the lens there are problems with geometric distortions (but I think that they can be reduced somewhat by using a lens of a larger diameter).
IMG_20210129_224802s.jpg

P.S. The main problem is the selection of lenses ... unfortunately, I do not have familiar opticians who have the necessary knowledge and formulas ... so I have to experiment with everything that falls into my hands

I've tried those lenses but they seem to introduce too much distortion into the projected image.

[OBNRacerMan]

I've tried those lenses but they seem to introduce too much distortion into the projected image.

It is possible that large diameter lenses will help reduce distortion. I tried - the further I put the lens from the projector, the smaller I can get the picture size. But due to the small diameter of the lens, at such a distance, it no longer captures the entire light beam.

Or approach the alteration radically, and make changes to the design of the projector ...

[Micr0]

I've tried those lenses but they seem to introduce too much distortion into the projected image.

It is possible that large diameter lenses will help reduce distortion. I tried - the further I put the lens from the projector, the smaller I can get the picture size. But due to the small diameter of the lens, at such a distance, it no longer captures the entire light beam.

Or approach the alteration radically, and make changes to the design of the projector ...

I can see in the pictures you posted the pincushioning of the image with the lens. Were you able to get good scans using that aux lens?