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I'm currently building a triangulation-based laser rangefinder with a camera and a number of laser pointers. Something that I'm interested in doing is using the strobe output from my Point Grey FireflyMV to trigger the laser, so that it is only on when the shutter of the camera is open. I want to do this primarily for eye safety. In addition, I'm curious as to whether I can then run the laser at a higher power level for this very short period of time.

The camera is gathering images at 60 FPS. This means it is collecting an image every 16.6 ms. The shutter time is adjustable between .12 and 512 ms. In this case, let's say that the shutter is open for .3 ms. I might keep the laser on for .1 ms on either side of the shuttering, just to ensure that the laser is at full brightness for the entirety of image capture.

So, I'm looking for a .5 ms pulse every 17 ms. First of all, is a diode laser (like this one) even capable of pulsing this quickly? Also, could I run the laser at say, 50mW for that short period of time, given that I'm running it at a 3% duty cycle?

Lastly, any circuits capable of doing this would be awesome.

Thanks!

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    \$\begingroup\$ So you're going to protect eyes by using short, high-power pulses... like LASIK? :) Depending on whether tissue cares more about average power or peak power, it will either be equally damaging or worse, not better. \$\endgroup\$
    – endolith
    Commented Apr 16, 2011 at 20:53
  • \$\begingroup\$ Ummm. Not quite. What I'm trying to do is increase the power output to like 10mW, so that it can be visible in a bright environment. I'm spreading the light out over a 2x120 degree arc, so the brightness isn't bad enough to cause an issue. Nonetheless, it looks like I can't increase the output, due to optical concerns. Safety is my number one concern, I wouldn't do anything that could damage anybody. \$\endgroup\$
    – Bradley Powers
    Commented Apr 18, 2011 at 4:05

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Laser diodes themselves can pulse as fast as you like - down to nanosecs - actual speed depends on the driver. It is not generally practical to increase power at lower duty cycles as the limiting factor tends to be optical damage rather then purely thermal. Bear in mind that unless you need the coherence or tight beam of a laser, normal power LEDs will typically give you more output power then lasers, and are more amenable to increasing power for short durations.

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  • \$\begingroup\$ Excellent, thank you. I definitely need the coherence of a laser. I'm using the laser light as a tool to help measure distance. Something like this: makerscanner.com \$\endgroup\$
    – Bradley Powers
    Commented Apr 18, 2011 at 4:03
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    \$\begingroup\$ In any case, it's good to know that I can pulse the laser rapidly. Any ideas on a circuit with which to do it? \$\endgroup\$
    – Bradley Powers
    Commented Apr 18, 2011 at 4:03

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