Scale track configuration for absolute optical encoder including a detector electronics with plurality of track detector portions

An encoder configuration for use in an absolute position sensing device usable to measure a relative position between two elements along a measuring axis direction, the encoder configuration comprising:

• an illumination portion;
• a scale element including an absolute scale pattern comprising a fine track pattern and at least a first absolute track pattern arranged to receive light from the illumination portion and output respective spatially modulated light patterns along respective light paths, each track pattern extending along the measuring axis direction;
• and
• a detector electronics comprising a fine track detector portion and at least a first absolute track detector portion arranged in a fixed relationship relative to the illumination portion, and arranged to receive spatially modulated light patterns from the fine track pattern and the first absolute track pattern, respectively, wherein:
• the first absolute track detector portion comprises individual photodetector areas that have a Y direction edge-to-edge dimension YDETABS1 along a Y direction that is perpendicular to the measuring axis direction, and
• the first absolute track detector portion is configured to spatially filter its received spatially modulated light pattern and output a plurality of respective position indicating signals that have respective spatial phases,
• wherein:
• the first absolute track pattern comprises geometrically congruent subtrack portions that extend along the measuring axis direction, the geometrically congruent subtrack portions configured such that:
• the geometrically congruent subtrack portions are separated along the Y direction by a dimension YCENT, and YCENT is less than YDETABS1,
• the geometrically congruent subtrack portions each have a Y direction dimension YTOL, such that the dimensional quantity [YCENT+2(YTOL)] is greater than YDETABS1, and
• the geometrically congruent subtrack portions are arranged such that if one of the geometrically congruent portions is translated along the Y direction by the dimension YDETABS1, then the geometrically congruent portions will nominally coincide;
• and
• the first absolute track pattern comprises patterned signal varying portions configured such that an area of the patterned signal varying portions varies corresponding to a first periodic function of x having a spatial wavelength L1, where x designates an x-coordinate location along the measuring axis direction, and the first periodic function is not a square wave.