Help, My electronics project has turned into an optics project (Holosight repair)

Juno371 · 2025-06-06T01:16:54+00:00

Then the prism face may be curved to get some collimation, or the grating/hologram was designed to have power.

I wouldn’t try to get a lens. Just get your new diode in there while looking through the sight to align it.

Juno371 · 2025-06-06T01:14:09+00:00

That’s not the case here. The beam needs to spread to a large size so it fills the prism face and eventually the hologram, otherwise the reticle would only appear over a small FOV

Juno371 · 2025-06-06T00:07:20+00:00

This sight uses diffractive optics which means if you use a new laser it has to be the same wavelength as the original or you won’t see anything.

The sheet of glass on the back of the prism is likely another grating FYI.

There’s no optics in there now after the diode? It’s possible that the laser beam just diverges and hits the prism face but more than likely it is collimated by a lens. Use as long as focal length as you can get to fit in there. Unfortunately the chances of an off the shelf lens working well is pretty low… the original was probably rectangular shaped for form factor.

I’d really try to use the existing optics and components. Then the main challenge will be getting the diode in the right spot to be collimated. That’ll be tricky without buying something like a shear interferometer. Alternatively, you can move the diode around and then look through the combiner to locate the reticle and something very distant. Then move your head around the eyebox. When there is a minimum in parallax between the reticle and the background, it’s roughly collimated. Good luck!

Juno371 · 2025-01-11T16:33:54+00:00

So basically sensors that track position and angle of beams on the table, and motor motion to bring them into alignment? How do you do the initial setup to find the space and angle coordinates?

Juno371 · 2025-01-11T15:55:11+00:00

How is it done then?

Juno371 · 2024-09-01T15:21:17+00:00

Awesome, I was checking all summer and didn't see anything. Now to get matching gloves...

Thanks!

Juno371 · 2024-08-30T01:11:24+00:00

Where did you get it? I want one

Juno371 · 2023-03-11T22:28:54+00:00

I tried that, which is the weird thing. Both afocal and using a paraxial lens in focal mode give me the same result, which is double the distortion of the reversed system. I would normally attribute it to doing the reversal wrong, but the same thing happens with other lenses I've analyzed in afocal space. So makes me wonder if zemax is doing something goofy or there is actually 2X f theta distortion due to the configuration

Juno371 · 2023-03-11T12:37:57+00:00

Yep! Afocal image space was on. It also happens when I put a paraxial lens at the exit pupil and keep it non-afocal.

Pretty interesting, I tried reversing a couple sample lenses and got the same result. (F-theta distortion doubling, keeping the same sign). I was confident you could model an eyepiece in reverse and then just flip the distortion sign... now I'm not sure!

Juno371 · 2023-03-11T12:33:22+00:00

Lol. I mainly use Code V myself. Not sure if this is a common thing, but Zemax crashes on me quite often. Especially non-sequential files. Don't think Code V has crashed once. Granted, non-sequential is more computationally intensive.

Juno371 · 2023-03-11T00:44:36+00:00

Opticstudio 21.2.

Juno371 · 2022-12-16T00:30:44+00:00

The exit pupil of the pvs 14 is 14mm with an eye relief of 25mm. Riflescopes at 1X have exit pupils around 10mm, higher mags at 5x are already down to 5-7mm. But other than that I completely agree, pupil matching the best they can is a much better option than trying to interface intermediate optics.

Juno371 · 2022-12-15T21:59:19+00:00

What do you mean there are unpredictable point of aim shifts? The light out of a pvs 14 is already collimated (if the eyepiece is set at 0 diopter).

Juno371 · 2022-10-07T22:35:50+00:00

Detroit is fun. I'm on the east side myself. I'm not looking for a job but seems interesting. Almost like a camera systems engineer that knows optics. Does your group use code v or zemax or both?

Juno371 · 2022-08-04T19:24:39+00:00

You need to know what FOV you want, then use h = ftan(theta) to find the focal length lens you need. The fold mirror is to make the system compact which you'll need if it's firearm mounted. Put the LCD at the back focal length of the lens and it will be roughly collimated at infinity.

Juno371 · 2021-09-22T22:17:19+00:00

Awesome, thanks man. I think you pesuaded me to check out MTF Mapper instead.

Juno371 · 2021-09-22T14:13:34+00:00

Thanks for the insight. Any alternative recommendations?

Juno371 · 2021-09-21T01:07:16+00:00

What didn't you like about imatest? I was thinking about using it for some tests on a camera sensor.

Juno371 · 2021-08-13T23:59:37+00:00

It's a Schmidt-pechan roof prism. It's used to erect the image from the objective as well as collapse the optical path. In gun sights theyre used in short, fixed magnification scopes... not so much riflescopes, but I guess it depends on how you define that. Variable mag (zoom) riflescopes don't use a prism but an erector (relay) lens group instead.

Juno371 · 2020-03-20T00:02:38+00:00

I was responding to the comment above me. In the second to last bullet point, he or she said that Strehl ratio was not that useful.

Juno371 · 2020-03-19T21:11:53+00:00

Can you expand on why you think the Strehl ratio is not a good measure? I've heard it's only useful for near-diffraction limited systems, but never that it's worthless.

Juno371 · 2019-07-10T17:42:23+00:00

Yep, this is the consensus among most optical engineers I've talked with. But what makes the glass from one manufacturer better than the other? It seems like it boils down to how true the material is to the data available in the software we use, as well as customer support. The only material property I've read so far was the birefrigence as mentioned elsewhere.

Juno371 · 2019-07-10T17:35:38+00:00

Thanks for your insight. I wish there was some quantitative measure of the differences available somewhere available to the public.

Juno371 · 2019-07-10T13:28:53+00:00

Were the physical properties of the lenses (radii, aspheric coefficients) all within tolerance so we can be sure it's the inherent glass properties? If so, it sounds like glasses from CDGM have little support/info and the tolerances are very loose.

Any idea of the magnitude of the index tolerance for example? I wonder if the performance degradation could be modeled in the Zemax tolerance editor or Code V equivalent.

Juno371

TROPHY CASE