[Laser] bar code reader for parts

[Jim Moss]

The older ones have a short HeNe tube and PS inthe handle.
2 detectors with 2 red filters, a servo/front surface mirror.
The 1-2mW HeNe of course appears much brighter than the 1mW 670nm.


Jim
N9JIM/6

--- TWOSIG at aol.com wrote:

> 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
>  
>  
>  
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