Low cost ebay red lasers teardown

[muvideo]

Some weeks ago I noticed that red laser pointer heads have come very low cost on ebay.
I bought these:
http://www.ebay.it/itm/160722139793?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

half an euro each including delivery, not much more than an high quality led …

And here are them, a little brass cylinder with a small pcb glued into a slot on the back.
They are small, the brass is 6mm diameter, 10mm long, 15mm including pcb, the wires
are about 70mm long:


The first thing I did was to power one up, at about 3V, it's pretty bright:


The lens isn's a cylindrical one (at this price   ), and the beam is a short line, but
it is decently focused for short distances:


Let's look better at it, the electronics are nothing more than a resistor in series,
for some reason mounted upside-down:



Let's crack it open, the lens holder is screwed on, and locked with glue.
It contains a small spring to hold the lens in position, the resistor is 82Ohm.
The diode starts conduction around 1.7V,  it's at 1.85V at 1mA but the intensity
starts raising very rapidly at 2.9Volts, when the current is 10mA, and the working voltage
is around 2V.



The diode itself is a bare chip without encapsulation:


Here it's powered with small current sourced by the multimeter:



Higher magnification, 10uA and 1mA:



Highest magnification I can go, off...:


...10uA , no lasing...:


...100uA, the emission zone starts being visible...:

...1mA, the emission zone is bright:


Let's reassemble ant test it, does it still work?
The seller sells them for 5V operation, I tried briefly and
the current is around 33mA with a voltage on the diode of 2.28V, the beam is
VERY bright, but don't know how safe it is, last time I played with lasers the
optical feedback was mandatory, otherwise the diode destruction was granted.

Here a comparison 3V (10mA) vs 5V (33mA), the exposure was the same,
the camera cannot reproduce the spot but the light spill intensity around the
spot shows the big increase in brightness :



Fabio.

[saturation]

Very nice work, and the photos are impressive for their clarity and magnification.

[ModemHead]

Very interesting, and excellent photography. Thanks for posting.

[M. András]

the closups were made with a macro lens on a dslr or with a microscope +high res camera?

[muvideo]

the closups were made with a macro lens on a dslr or with a microscope +high res camera?

Usually I use a macro adapter with the 50mm, this time I mounted the dslr
on the microscope, it was installed in the place of one of the two eyepieces.
The reason was magnification but mainly stand stability, the exposure of
some photos was of tens of seconds.
The big sensor on the dslr doesnt help, the depth of field is too thin and uncomfortable,
the photos are much worse than direct viewing trough eyepieces.

Fabio.

P.S. Thank you all for the compliments

[MikeK]

What are your plans for that many?

[Monkeh]

What are your plans for that many?

Sharks with lasers, obviously.

[muvideo]

What are your plans for that many?

Sharks with lasers, obviously.

One for the teardown, that unexpectly survived the treatment.
One of another task that soon will be the subject of another post.
edit: https://www.eevblog.com/forum/projects-designs-and-technical-stuff/fun-with-laser-and-pmt-tube-or-how-much-is-the-speed-of-light-here/
Now I only need 8 sharks, so the other 8 will be used for
frickin' sharks with frickin' laser beams attached to their frickin' heads.

Dr. Fabio.

P.S. By the way, the seller sold them in group of 10 at good price

[westfw]

last time I played with lasers the optical feedback was mandatory, otherwise the diode destruction was granted.

I don't think that's been true for a long time, at the low power levels.  I doubt any cheap red laser pointer has had anything fancier than a constant-current driver since the time they broke the $50 price point.
Still, that's an amazingly minimalist pcb!