https://alexbock.github.io/open-optical-designer/

The iPhone camera sensor is prone to saturating and clipping the blue channel when strong light from a blue LED is in the frame. Once the blue channel clips at the maximum value, a typical HDR gain map won't do anything to restore more nuance to it because they're not designed to add high-frequency detail to a blob of clipped pixels with identical values in the base image.

When I experimented with connecting two thermal cameras to a VR headset for stereo thermal vision, I used two Seek CompactPRO FastFrame units. They're 320x240@15Hz for $400 which is a lot more usable than the typical 80x60@9Hz consumer thermal, and it's easy to integrate the Android model into custom applications. They also have a 320x240@25Hz model for $1000.

I'm still impatiently waiting for affordable 640x480 thermal cameras, but in my opinion 320x240 at moderate frame rate is past the good-enough threshold to be legitimately useful for high contrast situations like identifying warm-blooded life on the side of a rural road.

> I'd love some sort of setup that outputs to >=8" 1080p display attached to my dash.

The Tesla Cybertruck has an option to display the view from the front bumper camera on the 18.5" main screen, but front camera display is unfortunately not available in any of Tesla's other models. With the proliferation of large touchscreens and camera arrays, more vehicles may support this from the factory soon.

[1] https://alexbock.github.io/blog/nir-water-red-wine-compariso...

[The word "bizarre" in the title quote has been replaced with "unusual" as HN appears to automatically delete the former word from titles.]

Comments URL: https://news.ycombinator.com/item?id=39321603

Points: 2

# Comments: 1

If you have a silver coin or a small piece of copper pipe and a large, strong neodymium magnet, then you can easily observe this effect at home by putting the metal sample on a table and quickly waving the magnet past it as close as you can without touching it. The metal will slide across the table following the magnet, despite the metal itself not being magnetic, because the moving magnet induces eddy currents which temporarily create a magnetic field like an electromagnet. Other metals besides silver and copper exhibit weaker responses due to higher electrical resistivity.

[1] https://en.wikipedia.org/wiki/Eddy_current_brake

I think the large R&D investments tech companies are making into VR/AR headsets are ultimately centered on the idea that years in the future, an affordable, comfortable, and socially acceptable headset for all-day wear in daily life could hypothetically replace smartphones, tablets, laptops, and screens.

If a future daily wear headset as a phone/computer replacement reached a critical mass of adoption, then control of the platform will provide the owner with a huge profit source in selling virtual goods that can be "worn" or "placed" in the real world and are seen equally by any other person wearing a headset. I won't speculate on exactly what would be popular, but it is conceivable that this could include things like: buying virtual wall posters of licensed characters, virtual landscaping objects placed outside a house, filters that virtually "repaint" the exterior or interior of a house, or personal adornments like virtual clothing or appearance modifiers. That is to say, a digital layer of adjustment on top of the real world where everyone wearing a headset is automatically shown the virtual objects or adjustments that anyone else has made (within the scope of the latter's own appearance and owned spaces - random members of the public could not place publicly visible digital objects in the middle of a NYC street). Note that this virtual economy is a profit motive for a company to build AR, but not the selling point for a headset adopter.

Apple is not trying to sell this headset to consumers for $3500. They're showing off future hardware that they believe represents the bare minimum for what average people might be willing to wear regularly, with the expectation that they will be able to produce essentially this same unit and sell it for perhaps a third of the current price in several years. The way it's presented is also an early form of reputation management for the product space trying to influence public perception of how someone wearing a headset is viewed by others around them.

Standard see-through AR headset designs face fundamental implementation limits with the display technology that generally result in accepting one of two unacceptable limitations: a display that projects an image over the real world but cannot render black or otherwise draw anything darker than the scene behind it, or a liquid crystal light modulator with a polarizer that permanently makes the glass tinted dark like sunglasses even indoors. Apple is instead making a VR headset that is completely enclosed, displaying the world through pass-through cameras and drawing the wearer's eyes on a front display for everyone else to see.

The front lenticular OLED shows how Apple is approaching the social aspect of trying to market the acceptability of wearing a headset in the company of other people. In the long term, establishing a virtual economy for digital world overlays is fundamentally dependent on the social acceptance of wearing an AR device regularly. This announcement seems to be trying to thread that needle in advance of when this technology could eventually be priced and sold as a consumer product. I.e. establish an image of an Apple headset positioned without the kind of negative associations Google Glass quickly garnered.

I have no idea whether AR will succeed in replacing smartphones years from now or fade into obscurity, but what I find interesting about this announcement is that it makes a timeline where AR does take off at least appear conceivable. They've only taken a first and early step into trying to make it happen, but they haven't made a fatal mistake yet.

However, the sd Quattro is sensitive enough from 1000 nm - 1100 nm that I can take handheld shots outdoors on a sunny day while stopped down to f/5.6, and the smaller aperture gives more consistent sharpness across the frame. It also only takes a few seconds exposure on tripod to capture astrophotography of red giant stars that emit significant infrared like Betelgeuse.

Incidentally, the original reason I wanted an infrared-sensitive camera and a 1000 nm long pass filter was to photograph stars in the sky during the middle of the day, taking advantage of the quartic dependence on wavelength in Rayleigh scattering to remove the overpowering brightness of the sky.

[1] https://alexbock.github.io/blog/nir-examples/near-infrared-8... (note: this image used an 850 nm long pass filter rather than 1000 nm but was taken with the same doublet described before)

https://www.zeiss.com/vision-care/int/eye-care-professionals...

If you're going to make your own, keep in mind that there will be a tradeoff between magnification and field of view.

I plan to add optimization features in the future to automatically tune design parameters to suit specified target criteria, as well as some application-oriented design generators for things like telescopes, binoculars, and camera lenses.

In the current version, the only features that automatically determine system specifications to achieve a specific result are autofocus for the distance from the last surface to the image, and a generator that produces a planoconvex singlet lens given a specified focal length and glass material.

> How does one buy lens elements? Are they custom manufactured or out of a catalog?

If I need some basic singlets or achromatic doublets for a visible-light use case that does not place strict requirements on the specific type of glass or the precise specifications of their AR coatings (if any), then I will typically order from Surplus Shed. They are significantly cheaper than other domestically shipped (US) sources for individual lens elements, but it is often necessary to design around the diameters and focal lengths that they have in stock rather than designing a finished system first and ordering exactly what it needs.

For specialized components like infrared and ultraviolet optics or for parts with formally documented specifications and product line consistency, I order from Thorlabs. They are more expensive.

Both Surplus Shed and Thorlabs will sell directly to individuals from their online stores. I have no affiliation with either company.

Comments URL: https://news.ycombinator.com/item?id=34939954

Points: 59

# Comments: 5

It's still ultimately a silver nitrate reduction reaction, but it's extremely consistent. I tried reproducing the classic silver nitrate/glucose/sodium hydroxide/ammonia silvering baths astronomers used before the modern switch to aluminum vacuum coatings, and my success rate was only about one in five attempts. It's much more difficult to execute than the typical silver nitrate demonstrations where someone silvers the inside of a glass flask because you need the silver to produce a perfectly even layer on the outside surface of the glass for a telescope. The spray reaction has worked for me every time.

Chemically depositing silver with the old-fashioned immersion setup is also very tricky as the reaction is quite temperamental. I recommend the two-part spray process if you want to try silvering a telescope mirror.