Optics (Like Mechanics) is a bitch, well for me anyway!
The latest problem I have overcome is the positioning of the barcode scanner, being far too keen to get into the electronics part of the MT700 scanner datasheet I skipped passed the mechanics and optics portions as usual and just popped the unit in the most prominent forward position of the PCB directly in front on the acrylic window.. FAIL!
If you read the datasheet (for ANY Barcode scanner) you will find that if the window is in front of it the laser reflects back off it and confuses the reading, worst case you wont read anything.
The solution is to mount the scanner at an angle to the window so any reflections from the laser do not bounce back into the sensor.
A temporary fix has worked, but again because of my haste I will need to re-design the PCB so somehow accommodate moving the scanner back and at an angle of about 15-20 degrees to the window.
Next time you look at a barcode scanner or any optical device with lasers and sensors , take note of this little quirk!