Summary
Transmitting analog video via photons is old hat: that’s how everything started, after all, back in the day with over-the-air TV. Up the frequency of those photons from radio to visible light, though? Well, now that’s rather interesting. [Daniel] aka [milar111]’s LYME 101– which doesn’t seem to stand for anything–laser-video transmitter/receiver pair was a strong contender in the recently-completed Frikken’ Laser Beams challenge, but somehow we missed putting it up on the blog. The project is documented quite well on GitHub as linked above, as well as on Instructables, and Hackaday.io, and in a YouTube video we’ve embedded below so you can see it in action. In principle it’s pretty simple: a Raspberry Pi is used to generate the composite video signal, which modulates a red laser diode through a 2N2222 NPN transistor and some passives. The reciever is a BPW34 photodiode wired with reverse bias for speed and fed through a LM318N op-amp. To get +9V and -9V for this circuit, [Daniel] makes the easy hack of using a pair of 9V batteries for a noiseless dual supply. It hooks up to a CRT just fine, but a little finessing in the form of a terminator resistor and a DC bias pot on the transmitter were needed to get his USB capture card working with the signal. It’s not the weirdest way we’ve seen people hack analog video signals– there’s no audio cassettes to be seen, and the signal isn’t even SECAM, the oddest encoding— but that’s not a slight. Transmitting video with higher-than-normal-frequency photons might not be that weird, but it looks like a lot of fun. Transmitting analog video via photons is old hat: that’s how everything started, after all, back in the day with over-the-air TV… What he is talking about?, did I miss something? I always thought TV development was on shoulders of radio tech. Wave-particle duality, my confused friend! Electromagnetic waves of all sorts– from the longest-wave radio to the shortest of gamma rays– can be conceptualized as photons. There’s not usually much point when it comes to radio, as the wave paradigm dominates there, but radio is photons all the same. So you’re totally right that TV broadcasts were using the technology developed by radiomen– but those radiomen were blasting photons into the non-existant aether. It was, but radio = light = electromagnetic radiation, same thing, just different properties at different frequencies. That is what this article meant when he said “Up the frequency of those photons from radio to visible light” Not true at all. Radio is electrons. Otherwise instead of powerful water-cooled lamps (or nowdays arrays of MOSFETs) you’d need a bog standard lightbulb to transmit. For most of the 1930s TV was developed independently of the radio. Only after WW2 when cheap electronics from China became available the industry really boomed and converged.