To provide a sensor configuration suitable for edge detection operation.

A photosensitive chip in one embodiment includes: at least one set of photosensors substantially aligned in a Y direction; and a layer of a non-transmissive material including a plurality of openings. Each opening in the plurality of openings includes a respective center line and overlaps only a portion of each photosensor so that only the portion of the each photosensor is photosensitive. The respective center lines for openings for each set of photosensors are not collinear in the Y direction. The plurality of openings include at least one row of openings substantially aligned in an X direction orthogonal to the Y direction. Each opening has an equal width in an X direction orthogonal to the Y direction.