r/Optics

I am new on this optical experiment and I don't know if the captured image is good enough or not.
Anybody here can gives me some insight?

Laser: Coherent Sappbhire SF NX (488nm)
Camera: Imaging Source DMK 33uX178

The image captured below is when no image(SLM) is projected.
Is this too noisy?

https://preview.redd.it/v5p68m3mfebh1.png?width=731&format=png&auto=webp&s=e053e8cbc31347ce7de4bf3efe7306ff66c590a4

https://preview.redd.it/703tro9889bh1.png?width=1776&format=png&auto=webp&s=994809c36b27df48dfec5683583f9997279a67b5

Hi. For a while I was developing a software for multilayer coating design and analysis. I want to share it now, I intend to continue development in the future. I called it TFStudio.

Features:

• Computing R, T, A values via transfer-matrix method (TMM) at any incidence angle
• Full-system modeling: front coating, substrate (with absorption), and back coating, including incoherent substrate multiple reflections
• Optimization & synthesis features including various local optimizers (DLS, Newton, Newton-CG, SQP, conjugate-gradient, differential evolution, simulated annealing), needle variation, gradual evolution and structural (random) optimizer
• Merit function editor for setting up various targets and constraints. Including default merit function generator and visual target editor (in Optical evaluation window)
• Analysis tools: R, T, A calculation, color evaluation, ellipsometry angles, admittance, E-field, GD/GDD, refractive index (RI) profiler
• Material libraries: refractiveindex.info explorer (offline/online), optilayer materials, .AGF (Zemax) catalogs
• Deposition simulators (broadband, mono)
• Tolerancing features including monte-carlo analysis, scattering, inhomogeneities, layer sensitivities
• Import/export of coating data for Zemax OpticStudio

and more.

Live demo with somewhat limited capabilities (no saving) is available in browser here https://tfstudio.xyz/demo/.

Here's repo https://github.com/aai2k/TFStudio
The license is MIT.

Experiment on left, simulation using KostaCloud

Most ideas in optics don't arrive in a single Eureka moment. The idea of using a Bessel beam for optical alignment took me decades to recognize, beginning with work I did during the Sputnik era measuring the radii of optical test plates with an autostigmatic microscope. (The full story is in supplementary material under preparation; this is the condensed version.)

The journey became more serious while developing methods for centering cemented doublets. The traditional approach requires moving between two centers of curvature, or between a center of curvature and a focus. The problem is that moving the detector introduces centration errors unless the translation stage is exceptionally precise, and therefore expensive.

Inspired by work from Jim Burge and his student Laura Coyle, who used CGH Fresnel zones to simulate a spherical mirror, I designed a computer-generated hologram with two concentric Fresnel-zone patterns. One zone focused on the detector for aligning the first element, while the second focused at the same detector position after the second element was added.

The concept worked exactly as intended. I could perform precision alignment without ever moving the detector. Unfortunately, it wasn't practical for production because every new doublet design required its own custom CGH. What I really needed was a universal method based on the same underlying principle.

That experiment did provide an important insight: concentric Fresnel zones of different radii could serve as reference markers in space. I realized that a regular array of such zones could be used to calibrate an entire measurement volume.

Arizona Optical Metrology fabricated a prototype CGH for me, which I later took to UNC Charlotte. Working with Jesse Groover and his advisor, John Ziegert, we used it to map the volumetric accuracy of a CNC machine by mounting the detector in the tool spindle and the CGH on the machine table. The experiment again worked as expected. We mapped a 150 mm cube with approximately 1–2 μm precision and published the results in a Precision Engineering conference proceeding.

That success naturally led to another question: How can this work over a much larger volume?

As I explored ways to extend the range, I realized that in the limit, uniformly spaced concentric rings, rather than conventional Fresnel spacing, might produce the effect I wanted. It seemed worth testing, so I ordered a grating consisting of 10 μm chrome rings separated by 10 μm transparent spaces.

Illuminating the grating with a laser diode coupled into a single-mode fiber produced significant benefits. I could follow the bright central core and surrounding rings of the diffraction pattern for the entire 10-meter length of the laboratory.

About a year passed before I had time to investigate further experimentally. During that time, however, I discovered that the grating behaved like an axicon, producing what is known as a Bessel beam. More interesting, several theoretical papers, well beyond my mathematical abilities, showed that such a beam propagates through optical systems according to ABCD optical matrix theory. Another paper described generating a Bessel beam using a spherical rather than a using plane wavefront as is usually done.

At the time, I filed those papers away without fully appreciating their significance. Eventually it dawned on me what they implied: unlike a conventional focused beam, a Bessel beam can be observed anywhere along its propagation path. You are not confined to working only at a focal plane or a center of curvature.

When I returned to the lab, I wanted an experiment that would be difficult to reject. A ball lens was the perfect test object because it cannot be tilted. It can only be decentered with respect to the incident beam. Once again, experiment and theory agreed within experimental uncertainty.

By then, Professor Daewook Kim and his student Zac Chen had become interested in the idea that a Bessel beam behaves like an ABCD ray in optical design. Zac carried out an independent theoretical study, and together with collaborators published a paper confirming that this interpretation was correct.

With both experimental and theoretical validation in hand, I've continued developing Bessel-beam-based alignment methods.

What makes the approach attractive is that the beam remains well defined far beyond the focal point of a lens. That provides much greater sensitivity to alignment errors than measuring only at focus. Just as importantly, the alignment axis can be established before any optics are inserted into the beam, eliminating the need for a precision rotary axis. This makes high-precision alignment in tilt and decenter practical even on simple tabletop systems where rotary tables are impractical or impossible.

Because the setup remains fixed in a Cartesian coordinate system, every alignment adjustment produces immediate, useful feedback. That also makes automation more straightforward than with traditional rotational alignment methods.

Looking back, this has been a long journey. Each experiment answered one question while suggesting the next. Piece by piece, the concept of using Bessel beams for optical alignment has taken shape.

The journey is far from over. In fact, I believe we're only beginning to see the possibilities. The evidence so far suggests that Bessel-beam alignment can produce better optical performance while making precision alignment both simpler and faster than current practice.

I'd be interested to hear what others think, especially anyone who has worked in the field of precision optical alignment and lens centering.

Long time listener, first time caller.

Howdy fellow gardeners!

I have a quandary. I have 2 tall garden beds facing ~south on a ~north-facing hill. The garden beds are shaded by our house until mid-morning.

There are spots on our tall fence that get early morning light just a few meters ~east from the garden beds.

So, I’m thinking that I can put some (outdoor rated) convex mirrors on the (strong) fence posts just east of the garden beds to gently redirect some of the early morning sunlight onto the garden beds. The fence posts are about 6 feet (~2 meters) tall.

Would this work? Does anyone have experience with this? Would I still risk burning my plants?

—————

I’m thinking of using convex mirrors because my understanding is that if I were to use a straight (or rather planar) reflection such as reflective Mylar taped to the garden fence it could burn the plants.

I have a setup with a micro oled display, that goes through a beamsplitter then reflects back up from a concave mirror that diverges/magnifies the image and then back through the beamsplitter to the eye. I added the Fresnel lens shown in the image above with its top face being placed exactly at 3mm from the micro oled display. The image produced that goes to the eye; I can see the colors of the display, but I mostly just see the grooves of the Fresnel lens. I have verified orientation and focal length distance. I have also tried to increase and decrease the distance between the lens and the display. Are these lenses just not suited for small displays or high resolution imaging?

https://preview.redd.it/9xyfgaboxxah1.png?width=1288&format=png&auto=webp&s=e8faaf5a641136d970e46c1bede542891998951d

https://preview.redd.it/hjekccw62yah1.png?width=763&format=png&auto=webp&s=ad0be9392b9717f8628a860e29212e0c6928170e

I’m building a Michelson interferometer with a HeNe laser to measure the interferogram on a single Si photodiode. The only lens in the setup is placed after the beam splitter, in the detection arm. With my current alignment, the interference pattern on a screen is a set of straight, parallel fringes, and the photodiode sits in that field to record intensity as I scan one arm.

For a quantitative measurement (i.e., determining the laser wavelength), is there any advantage to having a circular fringe pattern instead of straight fringes?

My understanding is that, as long as the photodiode is small compared to the local fringe spacing and sees a clean modulation from bright to dark as I scan the path length, the global shape of the fringes (circular vs straight) shouldn’t matter.

I posted a similar question quite a while ago on askhistorians, and I didn't have any takers, so I was wondering if someone on this forum may have any insights. One of the things that has always blown my mind is the tiny, tiny detail on inscribed artifacts from Ancient Egypt and other cultures. Most of the google searches that I have found indicate that magnification was done using water-filled vessels. However, I suspect there had to have been magnification through convex lenses, as it seems like the water situation wouldn't have been the sole source for as long as indicated. I'm wondering if anyone in this forum has a history or other tidbit about when convex lenses were first discovered and how used. Thank you!

Is it feasible to gain a roughness measurement of the face down side of a clear crystal while the surface is in contact with another object? My limited understanding is that the beams would be capable of reaching the base of the crystal, but a quick search didn’t yield much information on this. Apologies if this isn’t worded very well, I’m relatively new to this stuff.

Hi all,

I want to build a diffraction grating spectrometer that I can use to observe a large portion of the sky, if not the entire sky.

The main purpose of this setup is to detect whether an aurora is present. I already use an HSV-based detection algorithm, but it isn't very reliable because of ambient light sources such as the Moon, light pollution, and twilight.

I currently have an APS camera, an APS-C camera body, and the following lenses available for this project:

• 50mm f/1.4
• 11–16mm f/2.8
• 70–200mm

Here's where I'm stuck:

Many people seem to have built spectrometers like this, but almost all of them are designed to observe relatively small or localized light sources rather than a large section of the sky. In nearly every design I've found, the optical path starts with a narrow slit, followed by a collimating lens, then a diffraction grating (or even a stripped DVD), followed by another lens and finally the camera sensor.

Would it be possible to use an ultra-wide-angle lens to gather light from a large area of the sky and then feed that light through the slit and the rest of the optical system? Or would the slit simply defeat the purpose of using a wide-angle lens?

For someone with a solid background in optics, this is probably a trivial question. For me, not so much. I'd really appreciate any advice or pointers.

Thanks in advance! I can't wait to have my hopes crushed.

Picture from Google search. This device takes an optical fiber.

https://preview.redd.it/gcoy7177v7ah1.jpg?width=900&format=pjpg&auto=webp&s=7f10c530ec462967970c9eda9a20e914a3563da5

I got scammed on Prime Day! I ordered the Osight SE Green Dot 6 MOA during Amazon Prime Day. I was super excited for this. The item arrived, I opened the Amazon box to find the Osight SE box not shrink wrapped but taped on both sides. Thought that’s odd as I did not order a used product. Opened it up only to find a used Viridian optic with loose screws. I got completely scammed on this! Contacted Amazon and spent several hours, multiple times just to be told they cannot replace it only return it for a refund. Well it’s not on sale anymore as Prime Day is over! Went as high as I could with Amazon customer service and was told take a walk. Contacted Osight directly and they said I could only deal with Amazon. The seller on Amazon is Osight USA. Buyer beware when ordering through Amazon. Also, after this experience and lack of support to just get the product I ordered, maybe look at other companies than Osight! I’m still giving them an opportunity to step up and make things right whether that be through Amazon or different channels. I’ll update if there is any different outcome. Note to Amazon: do better, your customer service is lacking. Note to Osight: please help!

TLDR: scammed by Amazon and Osight USA on Amazon Prime Day. Looking for help from Osight!

I want to simulate a reflective optical mirror that concentrates sunlight into a line focus instead of a point focus.

In addition to that, I would like the reflected sunlight to remain on the same target line or approximately the same target region while the sun moves across the sky from sunrise to sunset. In other words, I am interested in whether this should be modeled as a fixed mirror geometry, a heliostat-like tracking mirror, or a reflective concentrator with some form of solar tracking.

What would be the best way to model this? Should I treat it as a cylindrical mirror, a parabolic trough, a heliostat system, or a non-imaging solar concentrator?

I mainly want to visualize the reflected rays and calculate the irradiance distribution along the focal line during different times of the day. Would 2D ray tracing be enough, or should I use a full 3D simulation with solar position changing over time?

Also, which tools would you recommend for this kind of problem: Zemax OpticStudio, TracePro, COMSOL, MATLAB/Python ray tracing, SolTrace, Tonatiuh, or something else?

Some specific questions I have are:

1. How should I include the sun’s changing position from sunrise to sunset?
2. Is it possible to keep the reflected light on nearly the same target line using only mirror geometry, or would active tracking be required?
3. How should I model the sun’s finite angular size, mirror reflectivity, and the irradiance distribution on the receiver?
4. Are there any recommended papers, tutorials, or example models for heliostats, parabolic troughs, line-focus solar concentrators, or reflective solar tracking systems?

My goal is to understand the correct optical modeling approach, visualize the reflected rays, and estimate the concentration of solar energy on a fixed or nearly fixed target line throughout the day.

Any advice on terminology, simulation setup, or useful references would be appreciated.

Thank you.

Hi everyone,

I am a graduate student working on OEOs, ML- assisted fiber sensor research. I am preparing my first arXiv submission under physics.optics, but arXiv requires endorsement because I have not submitted to this category before.

I understand that arXiv endorsement is not peer review, and I am not asking for random endorsement. I would appreciate advice on how to find an eligible physics.optics endorser, especially in optics/photonics communities where arXiv is not as widely used as in CS or high-energy physics.

If someone here is an eligible physics.optics endorser and would be willing to briefly check whether the abstract/manuscript is appropriate for this arXiv category, I would be happy to send the abstract or PDF privately.

Thank you very much.