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I'm interested in flash detection, what would be equivalent to 1000 FPS. High speed cameras that do this are too expensive and too heavy and provide too much information. In the long run I'm going to have probably 30 of them attached to a half dome with the goal of approximate direction finding.

What are the options for a photoreceptor?

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  • \$\begingroup\$ Thanks for your explanation in comments, elsewhere. Interesting problem to solve. And I'd love to find out how you eventually solve it, as I'd be very interested in the mathematical tools you applied to get there. I don't have an answer. Just some vague thoughts at the back of my head where I might start looking. Beamforming I know about, but not at optical wavelengths. But that makes me immediately wonder about Bragg's work long ago, which takes me towards fiber Bragg gratings and arrays of gratings. (And TDOA, as well.) I'd also wonder about spatial filtering. That's just to get started. \$\endgroup\$ – jonk Sep 19 at 2:21
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    \$\begingroup\$ Nice project. I hope I'm able to read about it, someday! (I'd +1 your question, but you haven't added your commented material to your question yet. And you should.) \$\endgroup\$ – jonk Sep 19 at 2:22
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A typical approach would be to use a photodiode with a TIA (trans-impedance amplifier).

Most small photodiodes are easily capable of 1 kHz operation.

The TIA can just be an opamp and a few resistors.

Without knowing more about your light source and what you are doing with the signal afterwards, that is about all the advice I can give.

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  • \$\begingroup\$ Thanks, I was about confused about photo diodes, I haven't investigated them much but most seem to be focused on the IR band, I need to do some investigation to see what wavelength would be the best for my application. \$\endgroup\$ – FourierFlux Sep 18 at 17:25
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    \$\begingroup\$ @FourierFlux What exactly is your application? It would go a long way in understanding your situation and question (which I'm sure I don't follow well, right now.) \$\endgroup\$ – jonk Sep 18 at 17:27
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    \$\begingroup\$ Most photodiodes work with all wavelengths of visible light, that shouldn't be a problem. If you are looking for brief flashes, a high-pass filter will separate out the ambient light. \$\endgroup\$ – evildemonic Sep 18 at 17:44
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    \$\begingroup\$ I just completed a project that detects an led flashing at 500 Hz in full room light. You will want the high-pass filter, trust me. This will give a big boost to your SNR before further processing. \$\endgroup\$ – evildemonic Sep 18 at 17:48
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    \$\begingroup\$ @evildemonic I learned a lot about such systems by studying devices used at street intersections which allow emergency vehicles to change the lights to block opposing traffic. They combine all of the techniques, optical and electronic, that one needs to know about. \$\endgroup\$ – jonk Sep 18 at 18:03
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One big challenge with photon detectors is sustaining sensitivity, in the presenc of large sunlight fluxes.

One way is to have small load resistors. This of course results in low sensitivity to gun/poweder_firing flashes.

Another way is to feedback the output voltage, thru a low_pass filter, and adjust the current of a constant_current_load.

This circuit is

  • photodiode, connects to collector of transistor; this node is the OUTPUT; cathode of diode is +5v biased (reverse biased)

  • NPN current source, collector to the photodiode, emitter grounded

  • large resistor from collector to VDD/2; this resistor size will set your gain

  • two large resistors in series, from collector to base

  • large capacitor from midpoint of the 2 series resistors, to ground

I've used this circuit a number of times, over the decades, to greatly boost the sensitivity of detection systems, because the sunlight (and 60Hz) gets mostly removed.

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