Photoelectric absolute encoder and installation method therefor

A method for installing a photoelectric absolute encoder, the photoelectric absolute encoder including:

• a scale having a plurality of tracks with different pitch patterns;
• and
• a detector having a light source and light receiving elements including a plurality of light receiving element arrays corresponding to the plurality of tracks, wherein
• a light receiving element array is additionally arranged at a position in the detector corresponding to a boundary between the track having a pattern with a wide pitch and the track having a pattern with a narrow pitch adjacent to each other in the scale, and
• displacement of the detector relative to the scale in a lateral direction is detected from a signal amplitude of the added light receiving element array, the method comprising:
• detecting the signal amplitude of the added light receiving element array;
• and
• performing positional alignment between the scale and the detector so as to correct displacement of the detector relative to the scale in the lateral direction that is detected from the signal amplitude.