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Figure 2 - Laser modules are often higher quality and include adjustable optics
Figure 2 - Laser modules are often higher quality and include adjustable optics

Laser pointers and Laser modules are basically the same thing - a cylindrical enclosure containing a laser diode, front end optics and some kind of current limiting circuit. In the case of laser pointers, the enclosure also makes room for a battery pack, which means that the laser driver circuitry can be made simpler, or often just run the diode directly off of the battery. Laser modules are designed with much more robust driver electronics and also include power regulation so they can be run from a range of voltages. Laser modules also include much higher quality optics, and are often fully adjustable so that the beam can be focused or spread for a given distance.

This ability to defocus the beam will be the key to making a working laser illumination system, so the laser module may be the best choice for this project if your budget permits. The small laser modules shown in Figure 2 have various wavelengths, and output low power (5mW) laser radiation in the red, green, and infrared bands. I also have several high power infrared laser modules that I use in night vision systems, and they range in power from 50 milliwatts to almost 1 watt in power! I 1 watt laser diode is more like a weapon than an illuminator, and special care must be taken in order to avoid serious eye damage or spontaneous fires in the lab!



Figure 3 - DVD and CD burners are a great source of high power laser diodes
Figure 3 - DVD and CD burners are a great source of high power laser diodes

If you are looking for a less expensive source for high power lasers, then you may consider using a bare laser diode along with some home brew driver circuit or a simple battery power pack. Laser diodes are usually less expensive than laser modules, and available at much higher power levels than most laser pointers. The downside to using bare laser diodes is that some type of current limiting circuit needs to be made and there are no included optics. The good news is that for illumination use, optics can be found from many salvaged sources, and often laser diodes can be powered directly from a 3 volt battery. The strange looking blocks shown in Figure 3 are the laser heads taken from several old DVD and CD burners. This is the part that slides up and down the two linear bearings to allow the laser to read the disc surface.

You can purchase a used or brand new DVD/CD burner combo pretty cheap these days. Inside you will find a pair of very powerful laser diodes. The DVD burner will include a high power 150 mW or better visible red laser diode working in the 650 nanometer bandwidth, and the CD burner will include a 60 mW or better infrared laser diode running in the 780 (infrared) nanometer bandwidth. For night vision illumination, the infrared laser diode will be the one you want, so look for a DVD/CD writer combo, or just a CD writer. The parts shown in Figure 3 will be easy to remove from the unit, and contain the single or dual laser diodes.

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