Abstract: An optical rotary encoder includes four photosensor elements aligned in a square fashion. A first pair of diagonally aligned photosensor elements develop output signals of inverse phase with respect to each other as a slit plate rotates. The thus obtained output signals are applied to a comparator to obtain a first control signal. A second pair of diagonally aligned photosensor elements develop output signals of inverse phase with respect to each other as the slit plate rotates. The output signals from the second pair of photosensor elements are applied to another comparator to obtain a second control signal.

Abstract: In a semiconductor color sensor circuit with two photodiodes having mutually different wavelength sensitivity characteristics, the ratio of numbers or areas of two types of transistors for logarithmic compression of signals from these photodiodes is adjusted so that errors in output voltage due to changes in temperature can be reduced and the dynamic range of illuminance of incident light can be enlarged.

Abstract: A position control system for positioning a D.C. motor at a desired position operates in a speed detection mode in which the D.C. motor is driven to rotate at a predetermined high speed, and in a position detection mode wherein the position of the D.C. motor is precisely controlled. In the speed detection mode, the control circuit forms a phase-locked-loop (PLL) control circuit which compares the phases of the speed instructing pulse signal and the rectangular signal derived from the actual rotation of the D.C. motor. The motor speed is controlled in accordance with the phase difference between the speed instructing pulse signal and the rectangular signal derived from the actual rotation of the D.C. motor.

Abstract: An optical rotary encoder includes a slit plate having a plurality of circumferentially aligned slits of a pitch P, a light emitting diode, and a light responsive section. The light responsive section includes four photodiodes formed on a single substrate. The four photodiodes are aligned in the tangential direction of the slit plate with the interval corresponding to 1/4 P. Output signals derived from each of the four photodiodes are introduced into a detection circuit for determining the angular position and velocity of a rotating shaft to which the slit plate is secured.

Abstract: Disclosed is a photoelectric encoder for providing an electrical pulse signal corresponding to the rotational position and direction of a disk rotor. The encoder possesses a feedback means including a second light sensitive means and associated circuit for obtaining the stabilized output signal thereof in spite of the fluctuation of the power source voltage and/or ambient temperature or adhesion of extraneous substances to light emitting and/or sensing elements and others.

Abstract: An arrangement for detecting sizes of original documents for use in a copying apparatus or the like, which is capable of effecting size detection at high reliability irrespective of thicknesses of original documents, and in which an adverse effect due to cross-talk light by neighboring light emitting elements employed in it is eliminated for detection of various sizes based on presence of correct original documents.

Abstract: A D.C. motor position control system operates either in the motor speed detection mode or in the motor position detection mode. A rotary encoder develops an approximate sinusoidal position indicating analog signal in response to the rotation of the D.C. motor. A waveform shaping circuit receives the approximate sinusoidal position indicating analog signal and develops a rectangular position indicating digital signal to a phase comparator which compares the phase of the rectangular position indicating digital signal with the phase of a speed instructing pulse signal so as to control the motor speed in a phase-locked-loop (PLL) manner in the motor speed detection mode. A slice level determination circuit divides the voltage level of the approximate sinusoidal position indicating analog signal into 16 (sixteen) degrees to obtain a sliced position indicating digital signal which is used to control the motor position in the motor position detection mode.

Abstract: A photoelectric semiconductor device is disclosed which exhibits a reduced spectral sensitivity in a desired wavelength zone. An N(P) type impurity region is formed in a P(N) type semiconductor substrate to establish a first PN junction functioning as a first photodiode. A P(N) type impurity region is shallowly formed in the N(P) type impurity region to establish a second PN junction functioning as a second photodiode. When the first PN junction is shunted, the photoelectric semiconductor device shows a spectral sensitivity which is reduced in the longer wavelength zone. Contrarily, when the second PN junction is shunted, the photoelectric semiconductor device shows the spectral sensitivity which is reduced in the shorter wavelength zone.

Abstract: Disclosed is a solid state wavelength detection system responding to output signals derived from a photoelectric semiconductor device. The photoelectric semiconductor device comprise at least two PN junctions formed at different depth from the surface of the semiconductor substrate. A deeper PN junction develops an output signal related to longer wavelength component of the light impinging thereon. A shallower PN junction develops an output signal related to shorter wavelength component of the impinging light. These two output signals are logarithmically compressed and compared with each other. Difference of the logarithmically compressed output signals represents the wavelength information of the impinging light.