Help me with Laser Diodes

[adlife]

Hi. I am a final year student of engineering and need all the help everyone can provide me with.I am supposed to make a vein locator in which 4 laser diodes are put in series and which operate on two 1.5V batteries. the laser diodes should have high intensity. however it should be noted that the light of all the 4 diodes should incident at a common point at the same time, making the light beam intensity all the more powerful.[/b]

 

[Crofty]

Lasers in series????

I think your tripped up before you start???

4 laser diodes electrically in series is a no-no.

Each diode has to monitor and control its power drive via its internal photo diode feedback. in series this wouldn't be possible, unless I've missed some obscure trick?

Unless of course your refering to physical series 'Line' of lasers? if so? then the following is still relevant.

Each of the 4 lasers should have there own control and drive circuit. This doesn't amount to a lot of circuitry, just same X4.

If say you used 4X 5mW laser diodes, with the 4X driver circuits, it will happily run on 3V batts, although at full drive for each of the lasers, this would equate to about 65mA x4 (260mA) and would run on 2X AA's.

I've knocked up a quick Schematic for the type of circuit you could use.

It will probably be harder to colminate all 4 laser to the one spot, physically speaking.

good luck

Steve

 

[TillEulenspiegel]

Interesting project. Have a few questions tho............
Is this devise supposed to be medical grade?
Do You have to use 4 diodes?
What is the depth and lateral detection window?
The electronics side is fairly simple .
The optics side is more problematic.
It involves laser Fq, filtering and sensitivity in the light spectrum of the detector, collimator's,splitters mirrors and an output coupler.
You want to detect blue/violet so you would use blue lasers w/ a blue filter.

I would seek out an expert in optics.I don't know if theres one on this board. I'm sure your local physics or astronomy Prof would know or point You in the right direction.

My guess is that as a probe you would use fiber optic cable( bundle ) perhaps with an adjustable focus and a central fiber for the detector. With all the optics and electronics in a portable case.

 

[fat-tony]

I'm not sure what they would be called internationally, but in Canada we have devices called Stud Finders. Basically, it's a row of LEDs that indicate where a stud is in the wall. You could have a system similar to this. Four lasers pointing down and 4 LEDs pointing towards the viewer. You just have 4 op-amp circuits like the one shown, and have it light the LEDs when you have a vein. With this, you can just slide this along an arm until only the middle LED is lit. You would then know exactly where the vein is.