Patent ID: 7687765

Claim:
An encoder comprising: a scale plate provided with a plurality of regions to be detected alternately arranged, along a reference line, on first and second lines which respectively extend so as to sandwich the reference line, each of the regions to be detected in which one or more light patterns to transmit light and one or more dark patterns to shield light are aligned in an arbitrary order; a light source device irradiating the plurality of regions to be detected with light; and a photodetecting device, arranged so as to face said light source device through said scale plate, having a photodetecting region that includes a plurality of pixels two-dimensionally aligned in a first direction in which the reference line extends and in a second direction perpendicular to the first direction, said photodetecting device having a first signal processing section outputting light intensity profile data indicating a one-dimensional distribution of incident light intensity along the first direction, and a second signal processing section outputting light intensity profile data indicating a one-dimensional distribution of incident light intensity along the second direction, wherein the alignment of the light patterns and dark patterns along the second direction is different among the regions to be detected, and wherein, when a width along the first direction of the photodetecting region is defined as W and arrangement pitches of the regions to be detected alternately arranged between the first and second lines along the reference line are defined as D, a relational expression of W/2<D<W is satisfied.