Abstract: A transmission type encoder is disclosed, which comprises a main scale, a light source that radiates collimated light to the main scale, and a photodiode array that also functions as an index scale. The main scale has a rectangular grating in which light transmitting portions and light non-transmitting portions are arranged at pitch P, and each width of the light transmitting portions is set to 2p/3, whereby a third harmonic distortion in an output signal can be removed.

Abstract: A reflection-type main scale G1 is disposed on a first member 10. A diffused light source 40, a transmission-type light source index scale G2, and a photodiode array PDA are disposed on a second member 20. The diffused light source 40 irradiates the main scale G1 through the index scale G2 for generating a reflected image pattern. The photodiode array PDA detects the reflected image pattern obtained from the main scale G1. The photodiode array PDA and the index scale G2 are integrally united in such a manner that the receiving surface of the photodiode array PDA and the grating surface of the index scale G2 are aligned in a plane.

Abstract: A main scale 11 and an index scale 12 are arranged in parallel with each other so as to be relatively movable. A light source 10 for irradiating collimated light on the main scale 11 is provided above the main scale 11. A light detecting devices 13a and 13b for detecting the amount of light which pass trough the index scale 12 are provided below the index scale 12. The main scale 11 has an uniform grating which consist of transmitting portions 14 and non-transmitting portions 15 which are formed with a uniform width and alternately arranged by uniform pitch P. The index scale 12 has non-uniform grating portions 12a and 12b whose phase are mutually shifted 90 degrees. Transmitting portions 16 and non-transmitting portions 17 of the non-uniform grating portions are arranged at the same pitch as the main scale 11.

Abstract: A light emitting device assembled in a light transmitting type of photoelectric encoder is required to generate light having high parallelism and large quantity of light. This device uses one half of a concave mirror having a small aberration and long focal point. Hence, light radiated from a LED disposed at the focal point of the concave mirror has high parallelism. Further, using a plane mirror disposed at the optical axis of a concave mirror, light reflected with the plane mirror from a LED onto the concave mirror travels in parallel rays. Parallel rays, having a large quantity of light resulting from overlapping parallel rays, reflected from the concave mirror directly and indirectly from the light emitting element can be obtained.

Abstract: A capacitance-type measuring device for absolute measurement of positions is disclosed, which comprises a displacement sensor having a fixed element and a movable element, the movable element being capacitance-coupled to the fixed element and relatively movable against the fixed element, the displacement sensor being adapted to output signals corresponding to relative positions of the movable element against the fixed element, a signal processing circuit for processing the output signals of the displacement sensor and outputting an absolute measurement value corresponding to displacement of the movable element against the fixed element, a control circuit for controlling the operations of the displacement sensor and the signal processing circuit, and a power supply for supplying electric power to the displacement sensor, the signal processing circuit, and the control circuit, wherein the control circuit activates the signal processing circuit at a suitable interval so as to perform an intermittent measurement