Patent ID: 7304294

Claim:
An encoder, comprising: a code scale comprising alternating reflective and opaque stripes, and an emitter-detector module comprising a light source and a photodetector operably associated with the light source, the light source and photodetector being encapsulated in a transoarent medium defining an interface, the light source being configured to generate light and emit same in a first direction towards the interface and thence therethrough towards the code scale for reflection from the opaque stripes disposed on the code scale in a second direction towards the interface and thence therethrough towards the photodetector, a gap being disposed between the interface and the code scale; wherein a polarization filter is positioned operably between the photodetector and the interface, the polarization filter comprising a polarization axis oriented to cause the polarization filter to reduce an intensity of light sensed by the photodetector that is emitted by the light source and reflected internally within the encapsulant from the interface towards the photodetector.