Abstract: An encoder having a code strip, a light emitter, a photodetector, and a spacing member is disclosed. The code strip includes an encoding region having a plurality of reflective and absorptive regions on a carrier having an encoding surface. The light emitter generates a light signal that is reflected from one of the reflective regions. The reflected light is measured by the photodetector. The spacing member maintains a fixed distance between the encoding surface and the photodetector when the code strip moves relative to the photodetector in a travel direction. The spacing member is attached to the photodetector and moves relative to the code strip when the code strip moves relative to the photodetector. A mechanism for allowing one of the photodetector and the code strip to move in a direction perpendicular to the travel direction to accommodate alignment errors can also be included.