Lasers? In my Altoids?

Hey guys! I know I promised all of you that I would post some of my engineering projects. Well, this is one of my favorite ones, primarily due to its simplicity. This is also one of my first laser projects, so it isn't remarkably unique. However, I did manage to slip in a few extra features in it, notably the safety switch on the inside.

It has seen better days.

Operation is simple: Just flip the switch so it is pointing at the aperture of the laser, which is covered by the orange dust cap. For now, lets take a look inside.

Where are the Altoids?

As you can see, the bulk of the inside holds the batteries. You can also see the driver, the safety switch, the actuator, and the diode, which is fed by the red and black wires going into the aluminum heat sink.

Gruesome!

The driver is the fabled Groove 2 driver, which is based on a TLV1117 voltage regulator with a LM385 as a voltage reference. I reverse engineered it so that the safety switch selects a different resistor upon a different setting of the switch. Since it is a 3-throw switch, the center position is a secondary off position. Hence the purpose of the safety switch. The upper position corresponds to a low power setting, adjustable from 40mA to 100mA. The lower position corresponds to a high power setting, adjustable from about 150mA to 300mA. Unfortunately, I do not have a laser power meter, so I cannot test the output power. I can test the input current by putting a 1-ohm resistor in series with the laser, so each mV read by my multimeter translates to one mA. For the test, I put the resistor across the turned off switch.

The low power setting.

The high power setting.

Here is a look at the laser diode, a 16X LCC, meaning long closed can, originally extracted from the DVD module of a Blu-Ray disc burner.

You can see the blue AR (anti reflective) coated window of the diode.

In the following picture I turned the laser on low power to see the die of the laser in operation, and added a lens and a blue filter to the camera to help it focus and to reduce the saturation.

Notice how the light comes out at a pinpoint.

Amazing! There's one more thing I must add to this post. On the topic of laser safety, I did not turn on the laser on high power without wearing my laser safety glasses. Sure, they may be cumbersome, but the eyes are objects that can never be replaced. One risky move can damage them forever.

Certified to filter out red wavelengths by a factor of 10,000. 

That's all for now!

Grant