- Sun Nov 03, 2013 6:23 pm
#165189
I have just joined. I spent time following a very impressive topic in this forum, "Trying to understand how Laser Range Finders work" yet I still need your expert advice on selecting a photo detector.
I am prototyping an invention and the task I am solving is this:
Imaging a white screen with a laser dot (from a laser pointer, 650nm wavelength) slowly moving on it in a random pattern. A stationary objective lens is positioned 8 foot from the screen and it has a 12 inch diameter field of view in the center of the screen. A shutter opens for 50 - 150 millisecond to allow light to reach the photo detector.
The task for the photo detector is to reliably detect all instances when the laser dot happens to be within the field of view of the lens. The screen may be also lighted by natural light or any kind of common household electric lighting.
I am concerned that a tiny red dot from the laser will not be resolved against the lighted background in the large field of view.
The speed is irrelevant, the shutter is opening at the rate of 1Hz or less.
While the cost of building the prototype is not important I am looking for a low cost photo detector for a possible commercial viability. Thus Avalanche Photo Diodes ($100) and tight optical band filters ($60, from Andover Inc.) are not very desirable. Will a conventional photo transistor work? Or a photo darlington has a better chance? Or something else?
I am a mechanical engineer and I have no experience with photo detectors. I can just buy the components and try them one at a time but I hope that your advice will guide me in the right direction.
Thank you.
I am prototyping an invention and the task I am solving is this:
Imaging a white screen with a laser dot (from a laser pointer, 650nm wavelength) slowly moving on it in a random pattern. A stationary objective lens is positioned 8 foot from the screen and it has a 12 inch diameter field of view in the center of the screen. A shutter opens for 50 - 150 millisecond to allow light to reach the photo detector.
The task for the photo detector is to reliably detect all instances when the laser dot happens to be within the field of view of the lens. The screen may be also lighted by natural light or any kind of common household electric lighting.
I am concerned that a tiny red dot from the laser will not be resolved against the lighted background in the large field of view.
The speed is irrelevant, the shutter is opening at the rate of 1Hz or less.
While the cost of building the prototype is not important I am looking for a low cost photo detector for a possible commercial viability. Thus Avalanche Photo Diodes ($100) and tight optical band filters ($60, from Andover Inc.) are not very desirable. Will a conventional photo transistor work? Or a photo darlington has a better chance? Or something else?
I am a mechanical engineer and I have no experience with photo detectors. I can just buy the components and try them one at a time but I hope that your advice will guide me in the right direction.
Thank you.