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Detecting Reflected LASER Light

Posted: Mon Feb 03, 2014 3:45 pm
by KDLaun
Just for fun and coding experience, I have conceptualized an Arduino project where a laser line sweeps across a surface (wall) and the range to that surface is determined by triangulation.

The problem I have run into is detecting the light returning to the source. My initial tests using a 5mw red laser diode module and a standard A9950 LDR only nets in a detection range of about 1 meter, and that's in a pretty dark room. (I'm using a small lens to focus the image of the room onto the sensor area.) Before scrapping my idea, I wanted to see if there might be some hardware or software alternatives.

If I keep the laser, it appears there are a couple of possible solutions.
1) a more sensitive sensor
2) modulating the laser in a way that it can easily be picked up. (or a combination of both)

What are the hardware options? I've looked over various photodiodes and phototransisitors, but it's not really clear to me if they would have any markedly better sensitivity/selectivity.

Would the laser module respond to PWM input, and if so, what method would be used to detect the reflected signal? This part of the project was supposed to be incidental :-/

Plan B may be just to go with a very bright focusing flashlight, but the laser would be much cooler.

Re: Detecting Reflected LASER Light

Posted: Sat Feb 15, 2014 6:28 pm
by ThePyroElectro
KDLaun wrote:Just for fun and coding experience, I have conceptualized an Arduino project where a laser line sweeps across a surface (wall) and the range to that surface is determined by triangulation.

The problem I have run into is detecting the light returning to the source. My initial tests using a 5mw red laser diode module and a standard A9950 LDR only nets in a detection range of about 1 meter, and that's in a pretty dark room. (I'm using a small lens to focus the image of the room onto the sensor area.) Before scrapping my idea, I wanted to see if there might be some hardware or software alternatives.

If I keep the laser, it appears there are a couple of possible solutions.
1) a more sensitive sensor
2) modulating the laser in a way that it can easily be picked up. (or a combination of both)

What are the hardware options? I've looked over various photodiodes and phototransisitors, but it's not really clear to me if they would have any markedly better sensitivity/selectivity.

Would the laser module respond to PWM input, and if so, what method would be used to detect the reflected signal? This part of the project was supposed to be incidental :-/

Plan B may be just to go with a very bright focusing flashlight, but the laser would be much cooler.


You could probably use a photoresistor. If the return beam were to land upon it and you had a way to determine the power going through the photoresistor you could use the changing power value to do a very crude triangulation calculation.

A fun project to do is to point a laser at a glass window and have the return beam shine on a photoresistor that connects to an audio amplifier. Then you can hear what people are saying behind the glass window with enough amplification and filtering. Not really what you're looking for, but I thought I'd mention it.

Good luck!