I have IR laser, lets say 300mW, i need to detect reflected light of this laser, with 4 sensors, and measure direction, something similar to this project Making an infrared-guided water rocket - YouTube
Distance is 1-200meters, which sensor you think can fit for my case?
i have readed articles, about avalance photodiods, and seems it can help me - they are used in distance measurement, but they are too expensive, min price is 20$ for one
and since i dont need to measure distance, maybe i can use som eother type of photodiodes? on video used some other type of it, its not avalanche, cause i saw pcd, and there is only 2 connectors per diode, thank you for help.
Can you show a drawing of how you understand such a system working for you? By the way, you can't measure direction, but you may be able to compute it. Will the reflected laser light be a SINGLE beam or will it be a dispersed reflection?
The project in the video uses a high power array of IR LEDs as the target.
To detect reflected IR light outdoors requires you to distinguish it from the intense IR background from the sun and sky. The guide beam should be modulated (typically 38 to 50 kHz), as done with IR remote controls.
red - photodetector, green - reflected laser, blue - some signal value
case 1 - laser i between all detectors, and signal is equal - means we are looking direct to the point.
case 2 - laser is obsservable only by 2 detectors, we need to move to the left intul signal is equal, and we are on case 1.
yes, laser its just single beam, which is pointed on some surface
signal modulation is next step of my work, first of all i need to know which sensors i should use
IR Photodiodes, each followed by a narrow band amplifier/filter tuned to the modulation frequency.
i have tryed with BPW34S photodiode, and with amplifier, it worked but in that time, i had broken laser, without beam so i didnt measured distance of detection, will it work, or maybe you can provide some other name of photodiode?
for now, wavelength its not matter for me, i can choose any, but it should be IR so like 800 - 1000 nm work for me
Yes, but the reflection of that beam, even by a perfect front silvered mirror will no longer be a single beam. Describe the surface that will reflect the laser beam. Have you tested the reflected laser light to see if it is still a single beam. You really need to do that.
yes its not singlebeam (reflection) but in this case photodiode, can help me calculate count of reflected photons catched by himself, and in this case, if photodiode directed right to the reflected dot, signal will rise, and fall down when its not direct
Pick a photodiode with a response wavelength range that matches the IR emitter wavelength range as closely as possible.
you want to say that this small photodiode, can work for me?
i also understand that i need some kind of lense to catch more signal
That photodiode would work if the response wavelength range is similar to the wavelength range of the IR emitter.
Check the data sheets for both.
i didnt have laser yet, but this photodiode has 900nm, so you think 200meters can work, right? just want make sure.
Almost certainly not, unless you use a high power IR laser (wear eye protection), but the project will be a great learning experience.
Good luck with your project!
Have you priced IR lenses, yet?
not yet, i event dont know which one i need, can you suggest something please?
and im not sure that IR lenses is cheap, i think on usual lense, and ir filter, whish seems like is preinstalled in my diode
Would an IR lens be any different than a visible light one? I know that when I do IR photography I have to correct for the fact that IR focuses a little in front of the film plane. My lenses have a pointer that corrects for that. One can use an IR filter to block some of the visible light as well.
So maybe OP can find an old film camera with a telephoto lens for cheap to mount the sensors in.
i think i can find a best focus distance, for some lenses, i need a lot of them actually, 4 its for one device, but i want to have many devices, i mean i need some type os lenses, which i can purchase on ali or somewhere else
what if i increace laser power to ~3W, will it help?
something like this
Found this interesting IR matrix sensor:
IR Sensor
Adafruit packages it:
Adafruit breakout
Might give you some ideas.
