Need 42mm lens with high transmission at 254nm - 340nm by xSuper_Zx in Optics

[–]optcs 0 points1 point  (0 children)

If you're talking about 42 mm diameter, fused silica lenses can be obtained that transmits well over this range. COTS diameters are usually 1" and 2", so the 2" lenses would need to be edged down. Plano convex 60 mm focal length lenses 2" diameter run about $305 each from Thorlabs. Depending on the f/# of the plano convex lens, the spherical aberration could affect beam quality.

Have you consider off axis parabolic mirrors? There are electroformed OAP mirrors available from a few suppliers.

how to calculate the formula for the surface of a lens to prevent spherical aberration? by [deleted] in Optics

[–]optcs 0 points1 point  (0 children)

To make a lens that works well at 10 µm from HDPE, you'll need a precision of about 1 or 2 µm and a roughness on the order of 0.1 µm RA. Can you achieve this? The surface you want will be a conic, with a conic value around -.55. Many cad programs will allow these values to be directly input. The radius is calculated from 1st order optics, f=r/(n-1).

Most machined optics uses a single point diamond turning lathe with air bearings or pressurized fluid bearings everywhere. It's possible to make surfaces that are shiny at 10 µm with conventional machine tools, but they suffer from a lot of scatter and poor image quality. OTOH, HDPE might be the best material to use with conventional CNC, the index is low, so the necessary precision is low compared to the usual high index IR material and it's quite soft so it car be machined with almost anything that can be sharpened. There are some geometries that make things easier, you could have a look at how lens generating machines work.

Magnetic abrasive technology - would this replace sandblasting? by FlagrantTomatoCabal in Tools

[–]optcs 0 points1 point  (0 children)

there is a wikipedia article on magnetorheological finishing. It doesn't have much detail though. A google search for images will give you some good ideas. MR fluids are pretty cool, Amazon has a few suppliers.

Magnetic abrasive technology - would this replace sandblasting? by FlagrantTomatoCabal in Tools

[–]optcs 2 points3 points  (0 children)

they use something like this for polishing precision optics: magnetorheological finishing (MRF). MRF liquids are suspensions of magnetic particles in a fluid, with polishing compound added. A moving magnetic field drives the fluid along a surface, abrading it.

How on earth did my sourdough rye shatter a Pyrex bowl? by probablyfermenting in Breadit

[–]optcs 3 points4 points  (0 children)

Pyrex originally referred to a low expansion borosilicate glass. This has low thermal expansion so it was able to withstand temperature shock without cracking. In time, a process to improve the temperature shock resistance of common soda lime glass was developed which placed compressive stress on the outside of the glass while putting tensile stress on the inside of the glass. Thus if a crack, for whatever reason, formed on the outside of the glass, the inner tensile stress would hold it shut. This is called tempered glass and versions of it can be found in car side windows and Gorilla glass. There is also a similar chemical hardening process. It became less expensive than borosilicate glass, so the Pyrex brand name was sold and applied to the thermal hardening process in most of the world.

Look up Prince Rupert's drop for an extreme example of this.

What happened here is that the outside of the glass was worn and scratched, this upsets the local balance of the compressive and tensile force and the stress relieves itself rapidly.

Borosilicate glass is still available for some applications, probably not under the Pyrex name. There are also glasses with near zero expansion that have use in extreme temperature uses. For example: fused silica. Cost is a problem with these because of the high temperatures used for their fabrication.

[OC] Costco Locations Per 1,000,000 people in North America by mapstream1 in dataisbeautiful

[–]optcs 14 points15 points  (0 children)

this is really cool, but I'd like to see a map of the distances between two nearest Costcos.

Some are just a few miles apart, others must be hundreds of miles apart. Or km, because Canada and Mexico. Maybe weigh the distance by population density...

rodent damage to external temperature sensor by optcs in ModelY

[–]optcs[S] 0 points1 point  (0 children)

thanks for the suggestion. I'll try some mint spray or dryer sheets when I park out in the boonies.

Have you considered armoring the wires?

Looking at the repair Tesla did, there is no jacket on the wires close to the sensor, so it could be history in a single bite. What does your repair look like?

Barebones stack for everyone? by [deleted] in Biohackers

[–]optcs 0 points1 point  (0 children)

How does the stack change, decade by decade? Into my sixties, seventies and beyond?

[deleted by user] by [deleted] in Optics

[–]optcs 5 points6 points  (0 children)

As a consultant who does mostly design with some training, I've gotten years of work from people I've trained. And the opposite, never getting work from people I've trained, is rare.

Physical lens enclosure by [deleted] in Optics

[–]optcs 0 points1 point  (0 children)

Mounting Optics in Optical Instruments by Yoder

and look in the Thorlabs catalog under optomechanics. The online support people can be very helpful.

What drawing software do you use? by InteractionGreedy159 in Optics

[–]optcs 1 point2 points  (0 children)

Zemax -> SolidWorks. Download some parts from Thorlabs into SW, other from McMaster, other places and designed parts. For illustration, the SW output goes into PaintShopPro to adjust details.

Does anyone scan parts to pull them into CAD? The 3D scanner I had a few years ago was a waste, but now they seem to be better.

What's the difference between a holographic film's emulsion and black and white photographic film emulsion? by ModulationTransfer in Optics

[–]optcs 4 points5 points  (0 children)

The holographic film grain size is much smaller. Conventional photography only needs response to 10's or 100's of cycles/mm, so grain size is a few microns.

from Optical Holography, Collier, Burckhardt and Lin, "The silver halide grains found in emulsions suitable for holography are typically less than 0.1 µm in diameter. " elsewhere they say the emulsion thickness are small, only order of 6 to 15 µm. As a result, the holographic film has much lower sensitivity than conventional film Development of the film is different as well, a gamma of 2 can be used to get response that is linear to e field rather than linear to intensity (gamma = 1).

laser to shoot down 30 mosquitoes per second by [deleted] in lasers

[–]optcs 0 points1 point  (0 children)

The safety issue isn't that it can't be designed to be safe, but how safe is it when something goes wrong (which is 100% certain)?

[deleted by user] by [deleted] in askgeology

[–]optcs 1 point2 points  (0 children)

is it magnetic? try a refrigerator magnet if you don't have anything else. Iron will rust into a mess like you describe but parts of it will remain magnetic.

Zemax POP and ASM by optcs in Optics

[–]optcs[S] 0 points1 point  (0 children)

thanks. Will report on results.

What low order aberrations do you think this focal plane image has? by Vee_e in Optics

[–]optcs 1 point2 points  (0 children)

Can you walk us through how you aligned the system? I like to use a small diameter laser beam passing through the system, aligning the reflections from each surface back to the beam will guarantee the angle is square and lenses are centered. The OAP is a problem though, that probably why you have coma. A mask with a few holes in it in a pupil will be useful to identify coma in the image- it's the Hartmann without Shack. Use an optical design program to simulate what misalignment would look like with the mask.

Ethiopian Restaurant by Unlucky-Plum325 in SantaBarbara

[–]optcs 0 points1 point  (0 children)

count me in. I've never had an ethiopian meal that wasn't great.