[Laser] bar code reader for parts

[TWOSIG at aol.com]

Having a long habit of striping down inoperative devices to see what is  
inside, recently took apart a hand held bar code scanner.   I thought  that I 
would let you know what I found.  The information may be useful for  any of you 
that are scroungers at heart, like me.
 
handgrip case that has trigger switch, a window, and mounting places  for 
circuit boards - (this might inspire an LED light communications  demonstration 
for use at school science classes, scouts, ect.  Short range  demonstration 
units do not need the intensity capability of a laser, and if they  do not have 
them, are not subject to "laser-phobia". )
 
three front surface mirrors of various sizes
 
a servo motor with mount for one of the mirrors ( this one was rigged with  
stops and intended to be driven with an oscillation circuit, instead of 
rotating  in one direction.)
 
a laser diode rated at 1.0 milliwatt in a heatsink.  (This is not a  finned 
heatsink for continuous transfer of heat efficiently to the  air.  It was a 
thermal mass to absorb heat from the diode when the trigger  was pulled long 
enough to aim at the bar code target, read the data,  then cool off while the unit 
was moved to the next item with a bar  code target.  Certainly less than 50 
percent duty cycle.  The block of  metal not only would hold the laser diode, 
but had a threaded hole on the bottom  for easy mounting.  It also had a deep 
cut parallel to the bottom and  another parallel to one side for fine 
adjustment of the pointing angles after  the assembly was mounted.  Also, the laser 
diode was spec at 670 nm, since  the bar code reading beam needed to be seen by 
the operator.)
 
a cylindrical concave lens ( laser beam was passed through a window, then  
one of the mirrors to change its direction, and then the lens expands the  beam 
in the direction at right angles to the scan)
 
A front surface parabolic mirror with a center hole for the  transmitted beam 
( the assembly was set up to pass the expanding beam through  the center hole 
then to the oscillating mirror.  The light returning from  the bar code 
target is then focused on the light sensor which is mounted  behind the oscillating 
mirror.  A slight tilt of the focusing mirror is  required.
 
a light sensor assembly which includes a red filter.   ( I think  the filter 
is the best find because it is intended to discard the ambient  light.  I am 
thinking that I will try to use it in a daylight sensor  assembly for my 
experiments and build a separate nighttime sensor  assembly.   The light sensor 
itself looks like a small photocell  mounted on the kind of ceramic carriers used 
on most Cadmium Sulphide photo  resistors.)
 
 
I enjoyed "dissecting" the unit and may find some use for the parts.   From a 
systems view, it is very similar to a light communications device.   It is 
optimized for short range in high ambient light conditions.  If you  get the 
chance to take a scanner apart, even if it has no hope of providing  useful part, 
you might consider it.
 
James
N5GUI