Detecting laser rays

Thread Starter

neeladrinath

Joined Apr 5, 2017
37
Dear Sir,
I need to detect a laser ray in a project. At first I thought to use LDR for this purpose but it detects sunlight too. I have to test it in field so it will not solve the purpose. Now I am thinking to use RGB color sensors (like TCS3200,TCS3210) for this purpose. Because sunlight is white and laser is red color. But I am in doubt that it will work or not.

So please clear my doubt. If any other sensor can solve the purpose please suggest.
 

DickCappels

Joined Aug 21, 2008
7,565
You have many options.

I think the most common way to solve this problem is to modulate your laser with pulses and then use a tuned AC coupled amplifier before a detector. That is how most infrared remote controls receivers work.

You can also use color filtering to exclude wavelengths that your laser does not produce, thus reducing the interference.

Some kind of automatic gain control might be useful so only the gain necessary to detect your laser is used, thus reducing interference from other sources.

Arrangements of things that block light (think cardboard tubes) and this with holes in them can restrict the field of view. Using a lens to focus a specific spot onto a photodetector is another way to restrict the functional field of view.

RGB sensors might work to detect a particular color (look for correct ratios in the three channels), but if there were more than one light source in the image, the detector would see the result of mixing the colors unless you used an imaging device such as a color video camera.
 

Thread Starter

neeladrinath

Joined Apr 5, 2017
37
You have many options.

I think the most common way to solve this problem is to modulate your laser with pulses and then use a tuned AC coupled amplifier before a detector. That is how most infrared remote controls receivers work.

You can also use color filtering to exclude wavelengths that your laser does not produce, thus reducing the interference.

Some kind of automatic gain control might be useful so only the gain necessary to detect your laser is used, thus reducing interference from other sources.

Arrangements of things that block light (think cardboard tubes) and this with holes in them can restrict the field of view. Using a lens to focus a specific spot onto a photodetector is another way to restrict the functional field of view.

RGB sensors might work to detect a particular color (look for correct ratios in the three channels), but if there were more than one light source in the image, the detector would see the result of mixing the colors unless you used an imaging device such as a color video camera.
Sir,
Means RGB sensors can detect laser rays excluding sunlight if we filter the wavelength.
 
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Thread Starter

neeladrinath

Joined Apr 5, 2017
37
Sir,
I want to just filter the red color rays of laser excluding all other light signals coming from sun. I don't know any sensors about this. Please explain briefly about this with some examples of sensors.
 

GopherT

Joined Nov 23, 2012
8,012
Sir,
I want to just filter the red color rays of laser excluding all other light signals coming from sun. I don't know any sensors about this. Please explain briefly about this with some examples of sensors.
The idea is to pulse the laser (on/off) at 50k HZ. Then your detector will detect all sunlight but will also see a very small but detectable 50khz. You can build an electrical filter that will filter all other frequencies (interferences) except 50kHz much more easily than you can filter light. the unidirectional light of a laser is helpful too - as said above, make sure you use a 1-meter tube to exclude as much ambient (non-columnated) light.
 

Thread Starter

neeladrinath

Joined Apr 5, 2017
37
That I have not choosed.

Please tell me just one thing that if I take a color sensor (TCS3200,TCS3210) and put a red color Laser on it it will sense or not.
 

ericgibbs

Joined Jan 29, 2010
13,273
If the project is required to work in daylight, there will be a 650nm content in that daylight.
As suggested earlier you will need a AC coupled amplifier tuned for 50HZ , part of that circuit will be a 'slicer' which adjusts for the day lights 650nm DC component.
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Thread Starter

neeladrinath

Joined Apr 5, 2017
37
It means before color sensor some filter component is needed to filter out other lights from laser it may be a filter or AC coupled amplifier.
 
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