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Tesladownunder

Fri Feb 22 2008, 03:14PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I made up a violet laser from a Blu-ray replacement part. Commonly available as a new replacement part for $40 on eBay. For that you get the 5mW plus violet laser (also has red and IR lasers in the same package) PLUS all the optics and electronics in the carriage assembly.
Plazmatron seems to be one of the early people to do this and has an excellent segment on his site in conjuction with Sam from SAM's laser FAQ.
My construction and all pics are here with a few shown below.
I took a lot of care to do the initial soldering of the laser while in circuit including the 0.1uF cap (shorted and also the iron was earthed to the case). The flexible plastic circuit strip was cut and I removed other shorts and ran from low current10mA with the described LM317LZ constant current supply starting with 10mA. The red laser is speckled (ie lasing) and appears to be several mW.
The violet laser, however was far less bright than the red one and it was not at all speckled. It still fluoresces things. Ith was about 26mA judged by increased brightness but hard to be sure.
The unfocussed beam seems complete unlike the example of a damaged beam. I have run the current briefly (later up to a momentary peak of 79mA without a change in beam).

My question is whether the laser is damaged and how can I tell. Also, is it just running in "LED" mode.

I initially wondered if there might have been a short across to the IR laser lead but that would probably run at a lower voltage and stop the violet one running at all. I am about to test the IR laser separately.

TDU

1203693166 10 FT0 Laservioletassemblyobjective

1203693166 10 FT0 Laservioletredopticpath

1203693166 10 FT0 Laservioletredobjectivepattern

1203693166 10 FT0 Laservioletopticpathplain

1203693166 10 FT0 Laservioletobjectivepattern

Weston

Fri Feb 22 2008, 06:20PM

Registered Member #1316 Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365

make magazine has a article on this. what voltage are you driving the laser at?

...

Fri Feb 22 2008, 07:21PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

It is possible that you damaged the diode from ESD or overcurrent, although honestly I have abused the crap out of these diodes and have not seen any problems with it.

The low brightness is to be expected, because the 400nm wavelength is actually closer to UV than it is to blue/violet. You probably know more about this than I do, but IIRC a dark adapted eye is about as sensitive to 400nm at 680nm, so the spot should not look that much dimmer than a red spot. To an eye that is not dark adapted 400nm is actually almost invisible.

Because the violet diode has a much higher operating voltage (almost 4v!) if there was any other diode shorted across it you would not get any output from the diode at all.

Really, as long as you are able to get a nice beam out of the device I wouldn't worry about the diodes health. It is hard to tell the brightness of the beam from your pictures, but I have found that if you shine the beam at a fluorescing target (piece of bleached paper) it should be about as bright as 3mw or so of 532nm light.

Hopefully Leslie will chime in with his comments on the issue...

Tesladownunder

Fri Feb 22 2008, 11:45PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I have checked the infrared diode which works fine so there was no stuff up with the connections. The first pic below shows the IR beam captured by the camera as a yellow spot (not visible to the naked eye) with a red 1mW handheld pointer for comparison.

I have found my large area photodetector which reads 10mV per mW. The readings were:
________Power_____Current
IR______3.5mW____20mA
Red____3.5mW____20mA
UV____ _1.5mW____20mA
UV_____3.7mW____30mA

This sounds encouraging and suggests that the violet laser is working OK but with different operating parameters to the IR and red which would be expected anyway.
The pic below shows the photodetector reading 1.8mW for the UV running on a somewhat flat battery and 1.4mW for a handheld red laser pointer (1mW nominal).

Still it does not look particularly bright unless you get a fluorescent target. I am aware of the the different frequency sensitivities of the eye and perhaps my tired old eyes don't have the response they used to.

I haven't measured the voltage as I was a bit reluctant to attach long voltmeter leads to the laser re ESD. They are current driven devices and I don't know what happens to the voltage in partial failure.

TDU

1203723646 10 FT39614 Laservioletirandred

1203723646 10 FT39614 Laservioletredpower

Conundrum

Sat Feb 23 2008, 03:56PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

Hehe, interesting. I have a whole pile of IR and red laser diodes here including ten from DVD writers (!)

Any ideas how I might go about testing these?

Last time I used an LM317T and adjusted the threshold until it lased, then increased carefully until the output stopped climbing

I had an idea to use these for, but don't want to blow 'em

Tesladownunder

Sat Feb 23 2008, 05:50PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

DVD burners are over 100mW and will burn things. Have fun. Lots of forums around to help you out with the setup.

I have got mine violet laser running and I am happier with it.
I did arrange switching for the red and IR to be selectable. Focusing is with a red laser pointer optics and will give a 4mm spot at 5m.

Add a bit of fog and the beam stands out nicely to the point of saturating the camera on longer exposures giving a light saber like effect.

The IR beam is shown as a yellowish dot next to the separate red laser pointer. The camera picks up IR to a degree. To the naked eye there is a very faint red dot.

TDU

1203788760 10 FT39614 Laservioletirandred

1203788760 10 FT39614 Laservioletlightsabrelong

Weston

Sat Feb 23 2008, 10:17PM

Registered Member #1316 Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365

where did you find it on ebay? can you give me a link.

mikeselectricstuff

Sat Feb 23 2008, 10:28PM

Registered Member #311 Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253

A search for PS3 Laser will usually find some of these pickup units.

Another fun thing to do with this laser is write messages in glow-in-the-dark material. e.g. as used on emergency exit signs./glow stars etc.

Tesladownunder

Sun Feb 24 2008, 01:37AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

mikeselectricstuff wrote ...

A search for PS3 Laser will usually find some of these pickup units.

Your site was where I first saw this. Thanks.
The part number is KES-400AAA
To find ebay sellers click here

Mike or Leslie. A question. How do you determine Ith? Lasing is clearly present although faint, down to 10mA as shown by the diffraction hologram from a cheapo laser pointer. This is not present with LED action.
I guess I could do a graph like Leslie did of currrent vs output.

Here is a hologram pic at normal power.

TDU

Conundrum

Sun Feb 24 2008, 03:15PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

nice!:-)
I would like to know if bluray ld can expose
the resist on a photosensitive pcb.

Also I have two sensors from lightscribe drives does anyone have a use? And some IR write lasers.

Next project is a Borg eyepiece using those triple junction 10mm 150mw diodes and LCD viewer

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