Optical rotary encoder and motor control apparatus

An optical rotary encoder comprising:

• a scale, in the form of a circular disk, including a plurality of different reflective parts disposed alternately along the circumference of said circular disk;
• and
• sensors, each including a light emitting part and a light detecting part, for outputting an electrical signal, wherein a light beam is emitted from said light emitting part so as to illuminate said scale with the light beam and a light beam reflected from said scale is incident on said light detecting part, thereby generating an electrical signal corresponding to the amount of light incident upon said light detecting part,
• wherein light emitting parts and light detecting parts of a plurality of said sensors are disposed such that the light emitting part and the light detecting part of each sensor are disposed on the same surface at the same radial distance from the axis of rotation of said scale so that the direction from the light emitting part to the light detecting part is perpendicular to the radial direction when viewed along the axis of rotation and such that said light emitting parts of said plurality of sensors are located at positions corresponding to substantially equal intervals along the circumference of said scale and said light detecting parts of said plurality of sensors are located at positions corresponding to substantially equal intervals along the circumference of said scale.

An optical rotary encoder comprising:

• a scale, in the form of a circular disk, including a plurality of different reflective parts disposed alternately along the circumference of said circular disk;
• and
• device pairs, each pair including a light emitting device and a light detecting device, for outputting an electrical signal, wherein a light beam is emitted from said light emitting device so as to illuminate said scale with the light beam and a light beam reflected from said scale is incident on said light detecting device, thereby generating an electrical signal corresponding to the amount of light incident upon said light detecting device,
• wherein said light emitting devices and said light detecting devices of two of said device pairs are disposed such that the light emitting device and the light detecting device of each pair are disposed on the same surface at the same radial distance from the axis of rotation of said scale so that the direction from the light emitting device to the light detecting device is perpendicular to the radial direction when viewed along the axis of rotation and such that said light emitting device in one device pair and said light emitting device in another device pair are point-symmetric about the axis of rotation of said scale, on the same side of the scale, and said light detecting device in said one device pair and the light detecting device in said other device pair are point-symmetric about the axis of rotation of said scale, on the same side of the scale.

An optical rotary encoder comprising:

• a scale, in the form of a circular disk, including a plurality of different reflective parts disposed alternately along the circumference of said circular disk;
• and
• device pairs, each including a light emitting device and a light detecting device, for outputting an electrical signal, wherein a light beam is emitted from said light emitting device so as to illuminate said scale with the light beam and a light beam reflected from said scale is incident on said light detecting device, thereby generating an electrical signal corresponding to the amount of light incident upon said light detecting device,
• wherein said light emitting devices and said light detecting devices of a plurality of said device pairs are disposed such that the light emitting device and the light detecting device of each pair are disposed on the same surface at the same radial distance from the axis of rotation of said scale so that the direction from the light emitting device to the light detecting device is perpendicular to the radial direction when viewed along the axis of rotation and such that said light emitting devices of said plurality of device pairs are located at positions corresponding to substantially equal intervals along the circumference of said scale and said light detecting devices of said plurality of device pairs are located at positions corresponding to substantially equal intervals along the circumference of said scale.