US Patent 7204424 Retro-reflective scanner having exit window with positive optical power

A portable electo-optical scanner for reading a target bar code having a plurality of bar code elements. The portable scanner includes: a housing supporting a scanning module and an exit window. The scanning module scans the target bar code with a scanning beam and collecting reflected light returning from the bar code. The scanning module includes: a beam source emitting a scanning beam; photodetector circuitry; and a retro-reflective oscillating mirror including a light collection mirror and an integral scanning or beam directing mirror. The scanning mirror is positioned to intersect the scanning beam and direct the scanning beam through the exit window. Oscillation of the oscillating mirror causes the scanning beam to be repetitively scanned along a scanning direction across the target bar code. The light collection mirror has a field of view that follows the scanning beam. The light collection mirror receives reflected light from the target bar code and directs the reflected light toward the photodetector circuitry. The exit window comprises a lens having a positive optical power with respect to the scanning direction.