The objective of this project is to create a high-powered laser pointer, with sufficient output to fall under the class IIIb category of laser classification.
Using the laser diode from a CD/DVD drive, I plan to create a homemade Class IIIb laser, which has sufficient output power to melt thin plastic and tape, possibly light matches and pop balloons. Also, another main purpose is a workaround to the Singapore Law, which does not permit the importing of Class IIIb lasers. The laser would have a power rating of over 200mW.
A normal red laser pointer used in presentations are class IIIa, having an output of <1 mW.
The decently high-powered green lasers pointers used in astronomy for pointing out stars and constellations, are at the legal limits of a class IIIa laser pointer, rated at <5 mW, and they are easily 50 times more powerful than the standard red lasers used in presentation. The colour green, at 532nm wavelength is also the most sensitive colour to the human eye, thus their laser beams can be seen clearly into the nightsky.
“Class 3a lasers are capable of emitting visible and/or invisible laser radiation with the maximum accessible emission levels as specified. As for visible Class 3a laser dvices, they operate in a power range of 1 -5 mW, which have irradiance in the emergent beam of not more than 25 W/m2. This class of laser are not capable of damaging the eye because of the person’s normal aversion response to bright light, unless the radiation is stared at for a long time, or unless binoculars or optical instruments are used. Many construction alignment lasers fall into the class 3a category.
Class 3b lasers are medium-power and moderate-risk laser devices that are capable of emitting ultraviolet, visible or infrared laser radiation with specified maximum accessible emission levels. It can be in continuous wave or pulsed mode and operating in a power of 500 mW or less for emission duration of longer than 0.25 sec, or a radiant exposure of 100 kJ/m2 or less for emission duration shorter than 0.25 sec. These lasers are capable of causing accidental injuries by exposure from the direct or specularly reflected beam. Diffuse laser beam reflections from class 3b are not hazardous, but may be so if focused to eyes with optical instruments. Therapeutic, acupuncture, bio-stimulation lasers, military laser range finders and designator are all under class 3b lasers.”
Class IIIb lasers are thus not legally permitted for use by individuals in Singapore.
Funnily enough, CD/DVD drives are classified under both Class I and IIIb. Class I makes the product legal for consumer to own because it complies with “no individual, regardless of exposure conditions to the eyes or skin, would be expected to be injured” by the product. Class IIIb refers to the particular laser diode within the CD/DVD drive itself, which is highly dangerous.
Difficulty: 1 2 3 4 5 6 7 8 9 10
Cost: 1 2 3 4 5 6 7 8 9 10
Time: 1 2 3 4 5 6 7 8 9 10
1. DVD Burner laser diode
2. Mini Maglite (AA batteries)
3. Focusing Lens Module (AixiZ Laser Module)
First of all, another set of warnings/disclaimers before you get excited over this project:
- Class IIIb lasers are dangerous; exactly why they’re restricted by law in the first place. Obviously, do not point the laser into anyone’s eyes at all costs. The beam is even dangerous if you look at it on a reflective surface (glass, metals, and even white surfaces), so eye protection is highly recommended!
- If you become blind it’s not my fault. I told you to use protective goggles, and stay AWAY from reflective surfaces!!! Really.
This project is a continuation from High-Power Laser Attempt 1 and High-Power Laser Attempt 2, from which titles you can guess, are failures at attempting this project. In both attempts, I have tried to extract the laser diode from DVD Burner and CD Burner drives. One occasion I overvolted my laser diode, and the other, fed it too much current. Both diodes died.
Although I learned my mistakes, I couldn’t swallow spending more on this project and ending up with failures. I got sick of buying DVD Drives to tear apart just for a tiny diode. I had this project on hiatus, pending abortion, until I saw an online mass order for DVD Burner laser diodes. I joined in the mass order and I received the diodes 3 weeks later.
That’s the little fella.
It’s a SLD1236VL high-power red laser diode. It is produced by Sony for their 16x-speed DVD Burner drives. This laser diode outputs monochromatic red light, rated at 250mW in pulse drive mode. The data sheet of the diode is available here.
If you wish to extract the laser diode from a DVD Burner instead, you can just follow my previous attempts at here and here. However, of course, do NOT test the diode like what I did. Doing so will only dry your diode. Instead, assume all is well and that your diode is working fine. All that remains is to extract the diode from the metal heatsink that it is very tightly attached to. There are various ways to remove the diode from the heatsink, and has to be done VERY carefully if not you’ll end up destroying the fragile diode. For example, you could use a dremel rotary tool on the heatsink, until the metal cracks apart. The diode is soldered in, so an alternative is to use a solderwick to extract the solder, and clean off any remaining solder with a needle file. Or use whichever method that suits you best, as long as the diode falls out without you hurting it.
If you read my previous attempts at extracting the laser diodes from DVD Burners (until I fried them), a successful extraction will produce something similar to these, although in a more poorer condition.
Laser diodes don’t emit a collimated beam, instead they emit an ellipsed-shape beam that’s unfocused.
So to focus the laser beam into a nice sharp beam, we’ll need the lens and optics. I bought a lens module online and had it mailed to me.
[Insert funny comment on ignoring the DANGER sticker]
I peeled off the sticker without a second thought and unscrewed the lens module. It was quite tightly screwed, so I had to do this:
The rubber band protects the nice new lens module casing from being scratched and all, while providing good friction.
From here, I took the module apart entirely.
It is typically made of these components.
However, the lens module comes with a laser diode preinstalled. It wasn’t easy to remove at all. As much as I wanted to save the diode for future use, removing it involved hitting it out with a stick and a hammer directed right into the front end of the diode. ‘Nuff said.
Before installing the new diode into the lens housing, I applied small amounts of Arctic Silver 5 thermal paste at where the diode will go into.
Installing the diode in the lens housing wasn’t easy, too. Using the brass end of the lens module, there’s a small hole at its end. I placed this over the diode, with the lens fitting through the hole, and hammered the diode in until it was flush.
Alternatively, you can do this:
Finally, attach back everything excluding the brass end.
Of course, I needed a cozy housing to keep my lens module with the laser diode powered by batteries and a switch.
While it is possible to make your own circuit, there is a simpler method to doing this. The reason why it isn’t as simple as attaching batteries is because, as I have done in my previous attempts, the current drawn from the battery is too great and it will fry your laser diode. As diodes get hotter, resistance decreases, letting more current pass through the diode, which causes more heat, and so on in a snowballing effect. Finally the diode hits a critical temperature and it blows.
The current supplied by the battery is rather stable, but in most cases, is too much to drive a laser diode. For instance, a DVD-burner laser diode would need about 200-250mA of power at about 2.5-3 volts (for any long life span to actually be expected of the diode). Laser diodes are, unfortunately, a very light load when wired directly to a battery, and an alkaline battery would easily put out about 500mA or more, and lithiums put out 2 or 3 times that much! This too is an instant death situation for our beloved laser diode.
For this project, we have decided to choose the simplistic path and use a flashlight with the right current regulation.
A Mini Maglite was chosen because it provided the current regulation needed in its internal circuit. The current supplied is around the 200-250mA required by the laser diode.
First, take everything apart, as always.
The metal reflector will hold the lens module in place, so I drilled to expand the hole.
The design of the Mini Maglite is also very suitable for this project. The connection to the diode is done using two long leads, as seen here with the original bulb.
I used some White Tack to stick the lens module on. It is important that the leads are fitted in with the right polarity.
And fit everything back nicely…
Of course, the original plastic cover doesn’t go back on because not only it doesn’t fit, but the laser also loses power as it goes through it, and we don’t really want that.
From here, it is important to note that focusing is VERY important. Focusing is done simply by turning and adjusting the lens of the lens module. Aim the laser at a black surface, and observe the size of the laser dot each time you stop, adjust and try again. Every slight bit matters. The laser dot may look focused and small, but we’re looking for the SMALLEST. Even fractions of a millimetre count.
And now, the results…!
I started off with a rather focused laser beam. Yet, it was unable to even light matches after a long period of time!
After precise focusing, the following results can be achieved.
Balloons were also good targets. Have a look.
However, the same focusing doesn’t work for all distances. A laser beam focused to light matches at close range will produce a horrible fat red smudge when pointed to a further wall. It must be refocused to use for long ranges.
After refocusing, pointing into the night sky…
And some other photos:
I read somewhere online that someone measured this Mini Maglite Laser, and reported that it was rated at 250mW. The person also used a high-end laser checking device, and 250mW looked reasonable, although a bit on the high side for a DVD Burner laser diode.
But still, I wanted to be certain. It happened that the lab I’m attached to at NUS had a Coherent LaserCheck lying around.
Now this device isn’t as accurate and high-end as the LPM-1 measurement device used by the person online, but it was all I got. Also, it looked really simple and cheap. And so I tested my laser on it!
Values were ranging between 130-200 mW, depending on how well I focused the laser beam, and angle of incidence into the sensor. After numerous tries, it registered a peak reading of 204mW!
While it’s still short of the 250mW reported online, I’m glad it broke pass 200mW.
Results are great!