IR vs Red

Warning! LaserI improved my laser PSU design: added voltage regulator, additional schottky diodes, some capacitors and it seams that laser supply is quite stable. I tested it with low power led lasers and several high power IR lasers from CDRW devices. Heat sink on the PCB is not mandatory. Only in rare cases, when powered from 12V and using extra power to diode, PCB is hot. As I changed some resistors, the current range is smaller. I decided, that I will not try to pump extra power from these small lasers. Now the range is from 0 to 200mA.


There is two lenses in the photo near PSU. I removed these lenses from photocopier. One lens have build in IR filter, other lens is made from clear optical glass. The bluish color of filtering lens is from copper ions in the glass.

And now, small experiment about wavelength filtering. Take note, that IR laser is much more powerful than RED. Red laser in this experiment is from cheap DVD player.


As we can see, special lenses filter IR light quite efficiently. Similar IR filters are placed inside all digital cameras. Sometimes it is possible to remove this IR filter and get very weird IR camera. The problem in modern USB web cams is, that IR filter is build in camera’s lenses and it is impossible to remove it. The RED beam cross both glass lenses without any visible problem. (Color change of the photo is due to white balance- digital camera set bluish color as white base).
The current through the diodes in both case was about 40mA (IR laser is in low power mode, for “reading”).

Small movie: IR laser. 100mA. From CDRW. Unfocused. (xvid, 1.5Mb)

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2 Responses to IR vs Red

  1. jammit says:

    Have you given any thought about making a “fake” laser? Put together a few regular rectifier diodes, a couple of high power resistors, and a ordinary LED to simulate a laser load. That way you could test the power supply without blowing expensive laser diodes.

  2. Yes, it is possible to use diode to simulate laser. Or it is possible to use powerfull LED.

    Most of lasers were damaged by human error :)

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