Abstract: Methods and apparatus are disclosed for broadening the bandwidth of a radiation detector and diminishing heat generated noise generated within the detector in order to enhance detectivity. The improved performance is achieved by applying a pulsed bias to the detector which consists of a sequence of waveforms which reduces the duty cycle of the detector in comparison to a detector subjected to a constant bias. A sophistication of this use of a pulsed bias is the utilization of a swept bias which employs a sequence of waveforms having gradual rise-times which further reduces unwanted detector noise and enhances detectivity.

Abstract: An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal.

Abstract: The improved power supply of the present invention adjusts the voltages applied to an image tube to provide automatic brightness control and automatically compensate for temperature changes. A first oscillator, transformer and multiplier supply DC high voltage to a microchannel plate (MCP) electron multiplier of an image tube. The oscillator is controlled via control circuitry to modify the voltage applied to the MCP to automatically compensate for temperature changes associated with an image tube and to provide an automatic brightness control mode of operation. A second oscillator, transformer and individual multipliers are used to supply appropriate DC voltages to the cathode and screen of an image tube; these voltages are also automatically adjusted for temperature changes associated with the image tube. The screen current is detected and is used by additional control circuitry as feedback for the first oscillator to provide the automatic brightness control mode of operation.

Abstract: A light receiving section of a photocoupler according to the present invention has, for example, a light receiving element, a converting circuit, an oscillator, an updown (U/D) counter, a decoder and a clock signal supply control circuit, and those devices are monolithically integrated therein. When the light receiving element receives light from a light generating section, an output of the converting circuit becomes High. At this time, an output of the decoder is delayed until the U/D counter has counted up to the preset number a clock signal supplied by the clock signal supply control circuit. On the other hand, upon having Low of the output of the converting circuit, the output of the decoder is delayed until the U/D counter has counted down to "0" the clock signal supplied by the clock signal supply control circuit.

Abstract: An integrator having a first circuit including an integrating capacitor and a feedback resistor, both being connected in parallel to each other in a negative feedback loop of the first circuit, and a second circuit, connected to an output side of the first circuit, for compensating for a leak by the feedback resistor. The first circuit operates as an integrator in high frequencies, and as a current-voltage converter in low frequencies. Further, the second circuit compensates for the leak by the feedback resistor, thereby to produce a value indicative of the result of integrating an input current.

Abstract: A corrective factor is applied so as to remove anomalous features from the signal generated by a photoconductive detector, and to thereby render the output signal highly linear with respect to the energy of incident, time-varying radiation. The corrective factor may be applied through the use of either digital electronic data processing means or analog circuitry, or through a combination of those effects.

Abstract: An ambient light rejecting quad photodiode sensor having compensation diodes connected with reverse polarity to respective quadrant photodiodes within the sensor, the compensation diodes being located outside of the area of illumination. By direct connection of compensation diodes in reverse polarity to each quadrant of the quad photodiodes, a large boost in signal to noise ratio is achieved for eliminating the effects of ambient room light as well as sensor dark current.

Abstract: Apparatus for measuring a particle size distribution by analyzing the intensity distribution of light scattered by particles suspended in a medium fluid. The apparatus is provided with not only a photosensor assembly for detecting forward scattered light but also that for detecting sideward and backward scattered light for the purpose of increasing the precision of measurement. Both the photosensor assemblies are temperature-monitored to prevent erroneous measurement due to small temperature-dependent zero-level shifts of photosensors used in the photosensor assemblies. If temperature variations of or a temperature difference between the assemblies exceeds a predetermined value, an alarm signal is generated with the measurement interrupted automatically.

Abstract: An optical encoder, having an offset adjustment function for causing light receiving element outputs to have the same direct current component level, and capable of greatly reducing an adverse affection by noise, to thereby generate an accurate position signal. A combined signal (i10), generated in a third electric current mirror circuit (T17-T19) for receiving output currents (ia11, ia12) from light receiving elements (A11, A12) through first and second electric current mirror circuits (T11-T13, T14-T16) and serving as a feedback signal (i10', i10") for eliminating an offset between direct current components of the output currents of the light receiving elements, is superimposed through a variable resistor (VRa1) on these output currents.

Abstract: The linearity and dynamic range of a photodetector system is enhanced by providing real time cancellation of condition-dependent quiescent output signals from the photosensitive devices by provision of a condition-dependent output signal monitoring device which drives the input section of a current mirror having output sections connected to the active photosensitive devices to zero out the condition-dependent quiescent output signals of those photosensitive devices during system operation. Multiple output sections may be run from a single input section of the current mirror.

Abstract: A light absorption detector has one or two light emitting members and a light receiving element spaced a predetermined distance apart from each other on a film substrate (1). Light is transmitted from one side to the other side of a subject. a change in the absorption magnitude of this transmitted light by the subject is then detected to provide respective information. A photodiode (PD) is located near the light emitting member or near two light emitting diodes (LED1, LED2). The photodiode detects a change in the quantity of light emitted. A CPU (16) corrects a change in the quantity of light with a change in the temperature of the light emitting element for controlling the current flowing to the light emitting member or light emitting diodes. Futher, a thermistor (37) and a heater (39) are located in the vicinity of at least one of a light emitting diode (34) and a photodiode (31).

Abstract: A method and apparatus implementing the method are provided for controlling optical power output level of a laser diode modulated during a burst mode interval by digital data transitions within a shared logical bus optical communications network and over a predetermined thermal gradient. The method comprises the steps of: optically monitoring a component of the optical output power of the laser diode during each burst mode interval and converting the component into a control signal, establishing a reference signal and comparing the control signal with the established reference signal and for providing a logical condition from said comparison, generating a strobe signal from information related in time to the burst mode interval, storing the logical condition upon receipt of the strobe signal, integrating the stored logical condition over a time period to provide an integrated control signal, and regulating current flow through the laser diode in accordance with the integrated control signal.

Abstract: A method for temperature compensation of a bipolar transistor through optically-induced carrier density enhancement. In response to the output of a temperature sensor, the optical output power of a photon source directed toward the bipolar transistor to be compensated is varied. Photons incident on the semiconductor surface effect variations in supplemental carrier concentration that maintain junction potential of the bipolar transistor at a predetermined level.

Abstract: In a measuring device including a magnetic-optic current transformer (2) defining an optical path having an input (4) and an output (6) and having an optical transmission characteristics such that the relation between optical energy supplied to the input (4) and optical energy arriving at the output (6) is a function of an electrical parameter being monitored, an electrically driven photoemitter (8) disposed for supplying optical energy to the optical path input (4), a photodetector circuit (10, 12) optically coupled to the optical path output (6) for producing an electrical signal representative of the optical power arriving at the output (6), and a control circuit (14,16) connected between the photodetector circuit (10,12) and the photoemitter (8) for controlling the light energy supplied by the photoemitter (8) and forming with the transformer (2) a high pass filter having a corner frequency, the control circuit (14,16) is composed of an amplifier (20) and a first compensation unit (24,26) connected to for

Abstract: An optical shaft angle encoder has a plurality of active photodiodes in an array on a semiconductor chip. A rotary code wheel has alternating areas for alternately illuminating or not illuminating the active photodiodes in response to the rotation of the wheel. Errors in the duty cycle involving the end active photodiodes in the array are largely avoided by having a plurality of inactive photodiodes at each end of the array with width and electrical properties effectively the same as the active photodiodes so that leakage current to each end active photodiode of the array is substantially equal to the leakage current to active photodiodes remote from the end of the array. Similarly, leakage current may affect the duty cycle of individual photodiodes may be minimized by surrounding the individual photodiodes with a reverse biased photodiode junction.

Abstract: An automatic gain control apparatus includes an optical receiving element. The optical receiving element generates electrical signals with an adjustable multiplication factor. A variable gain controller amplifies the electrical signals with an adjustable gain. A comparator generates determined signals corresponding to the difference between levels of an amplified signal from the gain controller and a predetermined signal. A comparator controls the gain of the controller. Also, bias signals are produced for setting the multiplication factor to first and second defined values.

Abstract: An ambient light rejecting quad photodiode sensor having compensation diodes connected with reverse polarity to respective quadrant photodiodes within the sensor, the compensation diodes being located outside of the area of illumination. By direct connection of compensation diodes in reverse polarity to each quadrant of the quad photodiodes, a large boost in signal to noise ratio is achieved for eliminating the effects of ambient room light as well as sensor dark current.

Abstract: Three means or methods for compensating for thermal noise, also referred to as dark signal, are utilized to enhance the accuracy of a monolithic diode array. A charge-coupled linear photodiode array is used in a camera to detect densities of any image projected or reflected onto the array. After conversion, voltage variations of one/one thousandth (1/1,000) volt in a ten volt range are significant to the measurement of densities. Therefore, extremely accurate control of thermal noise, which is generated in the cell sites and in the shift registers used to obtain the data from the cell sites, is extremely important. The three methods or means of control are as follows. Temperature control maintains the temperature of the photodiode array at approximately ten degrees centigrade to minimize the generation of thermal noise. A thermistor is used to detect any temperature variations within the range controlled by the cooling means and the reading is compensated for those variations in temperature.

Abstract: A light intensity detecting circuit using a charge storage type of optical sensor having a parallel capacitor eliminates the influence of the dark current of the optical sensor and/or the influence of the offset of the comparator included in the detecting circuit so that the accuracy of the light intensity detection is improved over that of the prior art. To eliminate the influence of the dark current of the optical sensor in an image sensor, there is provided an optically shielded mimic sensor having the same structure as that of the optical sensor including a corresponding parallel capacitor. In order to eliminate the influence of the offset of the comparator, there is provided a time constant circuit having a capacitor that may be composed partially of the parallel capacitor of the mimic sensor corresponding to the parallel capacitor of the optical sensor; with potential applying means for operating the time constant circuit.

Abstract: An optical shaft angle encoder has a plurality of active photodiodes in an array on a semiconductor chip. A rotating code wheel has alternating areas for alternately illuminating or not illuminating the active photodiodes in response to the rotation of the wheel. Errors in the duty cycle involving the end active photodiodes in the array are largely avoided by having a plurality of inactive photodiodes at each end of the array with width and electrical properties effectively the same as the active photodiodes so that leakage current to each end active photodiode of the array is substantially equal to the leakage current to active photodiodes remote from the end of the array. Similarly, leakage current which may affect the duty cycle of individual photodiodes may be minimized by surrounding the individual photodiodes with a reverse biased photodiode junction.

Abstract: A thermally stabilized optical preamplifier includes a first transimpedance amplifier which receives a photosignal current from a photodiode. The gate of a GaAs device is the input to the first transimpedance amplifier, and the drain is coupled to a source of constant current. Also coupled to the drain of the GaAs device is a common base stage, and the gain of the first transimpedance amplifier is set by a resistor coupled between the input of the first transimpedance amplifier and the output of the common base stage. A current setting resistor coupled to the output of the first transimpedance amplifier converts output voltage to current, which is summed with a compensating current in a second transimpedance amplifier. The compensating current consists of a variable current generator and a thermal current generator which compensate for the current produced by the absolute value and thermal characteristics of the gate to source voltage of the input GaAs device.

Abstract: The device comprises a photo-electric detection sensor (4), a luminescent diode (1) that produces a light beam for illuminating the detection sensor (4) and an opaque element (5) that is formed with an opening (6) and is mechanically connected to a mobile member (A), such as a hand of a timepiece, whose transit through a reference position is to be detected. The opaque element (5) and the opening (6) are so disposed as to allow the light beam to travel on or to be interrupted depending on whether the mobile element (A) is in its reference position or in another position. The device further comprises a comparator (13) which compares the signal produced by the detection sensor (4) with a reference signal produced in response to a signal supplied by a reference photo-electric sensor (9) that is manufactured on the same plate of semi-conductor material (3) as the detection sensor (4) and is so disposed as to receive no light.

Abstract: A circuit comprising a semiconductor photodiode with a first and a second terminal and an internal series resistor, including an amplifier with a first input, a second input and an output, the first photodiode terminal being connected to the first amplifier input, the second photodiode terminal being connected to the second amplifier input and a negative feedback being inserted between the output of the amplifier and its first input, characterized in that a coupling is introduced between the output and the second input of the amplifier, by means of which a voltage is generated between the second input of the amplifier and the second terminal of the photodiode, this voltage being oppositely equal to the product of the internal series resistance and the signal current flowing through the resistor.

Abstract: A temperature-compensated apparatus and method for determining the percentage of solid particles in a suspension (consistency) is provided. A source of diffused radiant energy is directed toward a suspension to be measured. The portion of the energy which is forward-scattered by the suspension is detected and a first signal indicative of the magnitude of the forward-scattered energy is produced. The portion of energy which is back-scattered by the suspension is detected and a second signal indicative of the magnitude of back-scattered energy is produced. The first and second signals are combined at a predetermined ratio to produce a feedback signal used to control the intensity of energy emitted from the radiant energy source. The intensity of energy emitted from the source is a function of the forward-scattered and back-scattered energy and is directly proportional to the consistency of the suspension being measured.

Abstract: A single beam wavelength scanning spectrophotometer comprises means for passing radiation from a radiation source (1) to a radiation detector (4) over a defined path which includes a monochromator (2) capable of being scanned across a selected wavelength range, means (7) for storing a first set of signals representative of the radiation falling on the radiation detector, the first set of signals being spread across the selected wavelength range to form a first spectral response, means for inserting a sample (3) in the defined path, means for producing a second set of signals representative of the radiation falling on the radiation detector when the sample (3) is inserted in the defined path, the second set of signals being spread across a selected wavelength range to form a second spectral response, and means (7) for calculating the transmittance or absorbance of the sample at desired wavelengths from the first and second spectral responses.

Abstract: Measurement value signals (S1), for example from a signal transmitter which is located at high-voltage potential, which are transmitted by a signal transmitter (1) with a transmit diode (6) on the high voltage side via an optical waveguide (8) to a signal receiver (9) with a photodiode (10) at ground potential, are subject to an optical signal attenuation along the way. To ensure automatic attenuation compensation both for alternating and for direct voltage measurement signals (S1), a reference direct current (I.sub.REF) is fed back to the transmit diode (6). The transmission system is calibrated before each measurement. During this process, the input of an amplifier (4) of the signal transmitter (1) is connected to reference potential (U0) via a switch (3) and the gain factor of the signal receiver (9) is controlled in such a manner that its output signal (S9) is equal to a predeterminable reference voltage (U.sub.REF).

Abstract: A photoelectric amplifier comprising a photodiode having an anode connected to a gate of a first FET and a cathode connected to a gate of a second FET, with the second FET having a source-gate interconnection so as to be self-biasing. The photodiode cathode is connected to a high impedance feedback loop, including an output transistor, which is connected back to the photodiode anode. In a preferred embodiment, further included is a feedback circuit gain controlling transistor having a base driven by the feedback circuit and a current electrode connected to the source of the first FET.

Abstract: A circuit for protecting a protected circuit against radiation has a PIN diode series coupled to a laser, which is optically coupled to a photodiode. The photodiode is coupled to the protected circuit. When radiation occurs, the resistance of the PIN diode increases, which causes the laser to cease emitting light. In turn, the resistance of the photodiode increases, thereby decreasing the current from a power supply through the protected circuit.

Abstract: A sensitivity calibration circuit for use in an absorption analyzer provided with a check-signal generator for easily checking the sensitivity, includes a temperature compensating circuit for use in an optical system for compensating for a temperature draft due to said optical system and a temperature compensation circuit for use in a sample system for compensating for a temperature draft due to the sample system.

Abstract: A semiconductor light detecting integrated circuit comprises a light detecting element, a constant current source having a first FET connected in series to the light detecting element and a power source, the constant current source having a region in which a constant current flows through the first FET, and an electrical circuit having a second FET the gate of which is connected to a connecting point between the light detecting element and the constant current source, the electrical circuit providing a two-valued output for the gate voltage at the connecting point generated according to whether or not the output current of the light detecting element reaches a predetermined current set in the constant current region of the constant current source.

Abstract: A bias circuit accurately compensates temperature coefficient of an optical multiplication in an avalanche photodiode with low power consumption. Temperature coefficient voltage for compensating temperature coefficient of the multiplication of the photodiode is delivered from an emitter follower added a constant voltage to an input of an operational amplifier. The output of the operational amplifier is added, via a voltage regulating diode, to a base of a transistor of which emitter and collector are respectively connected to a terminal of the photodiode and a negative power source. Emitter voltage of the transistor is dividedly connected to another input terminal of the operational amplifier, wherein this connection is negative feedback. The temperature coefficient voltage generated at the emitter follower is amplified inversely proportional to the divided ratio of the emitter voltage of the transistor in order to compensate the temperature coefficient of the multiplication of the photodiode.

Abstract: An optoelectronic transducer is proposed which includes a PIN diode (2) that delivers a current that is proportional to a light signal that is received. The diode is connected to the input of an inverting amplifier (4) that delivers a voltage signal v.sub.s. A negative feedback means of the transfer impedance type (6) is connected across the inverting amplifier. The transducer further includes a stabilizing means (8) for the amplifier gain and a temperature drift compensating means (10) for compensating for the drift in amplifier temperature. The stabilizing means (8) includes a detector (26, 28, 32) for the high peak of the signal v.sub.s, and the temperature drift compensating means (10) includes a filter means (38) for producing the means value v.sub.m of the signal v.sub.s, and a comparator (40) that receives the signals v.sub.s and v.sub.m and delivers a signal that reproduces the interference of the light signal that has been received.

Abstract: A photo-electric conversion device includes a first photodiode in which a current is changed in accordance with a light intensity; a second photodiode which is connected to the first photodiode and in which a current flows in the same direction as that in the first photodiode; a light shielding structure for shielding the second photodiode with regard to light; a capacitor, connected in parallel with the second photodiode, for charging/discharging a current from the first photodiode; and an oscillator circuit for performing a switching operation in accordance with the charging/discharging operation of the capacitor so as to generate an oscillation voltage output. The light intensity is thus converted into a frequency of the oscillating voltage, and dark current in the first photodiode is discharged through the second photodiode such that the capacitor is always charged only by a current caused by received light detected by the first photodiode.

Abstract: A device for stabilizing an output of a photosensor which uses a light-emitting element and a light-receiving element is disclosed. A resistor is connected in series with the light-emitting element to control a voltage across the series connection of the light-emitting element and resistor to a constant value. The output of the light-receiving element is stabilized against temperature variations without resorting to an extra light-receiving element for compensation.

Abstract: A semiconductor laser drive circuit functioning as a light source of an optical recording/reproducing apparatus using an optical disk. In the recording mode, the input light of a semiconductor laser is modulated by a recording signal, the output light of the semiconductor laser is detected as a monitor signal by a photo sensitive device, the peak value of this monitor signal is held by a peak-hold circuit, a differential compensation control signal is obtained from the output of the peak-hold circuit and is fed back, and a photo control system to control the output light to a constant level is constituted, thereby controlling in such a way that the output light of the semiconductor laser becomes a certain constant modulation amplitude. Even upon recording, the output light can be stably controlled within a wide temperature range even if the characteristic of the semiconductor laser changes with the elapse of time. Also, this drive circuit can be realized by a simple arrangement.

Abstract: The present invention provides an opto-electric position detector circuit utilized in encoders or the like which determine the position and speed of the motion of robots, processing machines, recorders or the like. The output from a photodetector is input to the Schmitt trigger circuit of which threshold voltage is derived from the output of a voltage dividing resistor circuit. The voltage dividing circuit is arranged in a series-parallel circuit configuration with a series combination of resistor and thermistor having negative temperature coefficient of resistivity which combination is in parallel relation to another resistor, such that the Schmitt trigger circuit provides a consistent rectangular waveform output over a wide temperature range to thereby assure exact control and measurements even in actual operating locations suffering from severe environmental conditions where temperatures are high.

Abstract: There is a method and an apparatus for reading an image in which the light emitted from a light source through an original is converted into an electric signal by a photoelectric converting device and is outputted as an image singal. In this method, a compensation light is radiated onto the photoelectric converting device and thereby causing a compensation signal to be generated therefrom; this compensation signal is stored into a memory; an original image is then read; and the read signal is compensated by the compensation signal stored in the memory. The compensation light corresponds to each intensity of lights which are obtained through a reference original to be read and which are received by the photoelectric converting device. By use of this method in an original reading section of a facsimile apparatus or the like, an ununiformity and a variation in signal of each bit which is read by the photoelectric converting device are compensated, so that a stable output image signal can be derived.

Abstract: A laser-doppler-anemometer for measuring the velocities of moving test specimens employing a laser beam source, deflection optics for at least two partial beams, collecting optics for focussing at least one of the partial beams on the test specimen, and a detector for the scattered light radiated from by the moving test specimen. A compact construction and further possible applications can be obtained when the laser beam source is provided by at least one laser diode whose temperature can be adjusted and kept constant with a temperature control circuit.

Abstract: A light sensing apparatus comprising a solid-state photocell responsive to low levels of light connected to an impedance matching buffer stage, a gain controlled amplifier stage and an output amplifier stage; a gain control network controlled by a temperature sensor for receiving an amplified signal from said output stage, the gain being adjustable to compensate for temperature dependance of the photocell signal.

Abstract: A pair of photodetectors are electrically connected in series. A common interconnection point of the two photodetectors is electrically connected to the inverting input of an opertional amplifier to provide a signal indicative of visible light falling on one of the photodetectors. The other of the photodetectors is masked to block visible but allow a response to non-visible radiation in the form of gamma, x-rays and the like.

Abstract: A color information detecting device comprising a plurality of color detecting apparatus for detecting respective different color lights from each other, converting apparatus for producing an output in non-linear relation to the input signal, changeover apparatus for selectively applying the outputs of the color detecting apparatus to the converting apparatus, apparatus for coinciding a number of successive outputs of the converting apparatus, and computing apparatus for computing the coincided signals from the coincidence apparatus. The device also includes a first constant current source for applying current of a prescribed intensity and a second constant current source for supplying current of another intensity equal to the prescribed intensity times the intensity of the current supplied from the first source which are included so that another mode can operate. The outputs of the first and second constant current sources are selectively applied to the converting apparatus.

Abstract: The average video level of a video camera is corrected for film-to-video conversion by having a film aperture plate with a light-passing opening that is slightly enlarged with respect to the image area of the film. Non-image light passes through a peripheral region of the film, as defined by the enlarged opening, and strikes a part of the camera sensor not receiving image-wise illumination. By enlarging the aperture plate opening just enough that the video signal from the non-imaged part of the sensor approximates a desired average video level, the automatic video level correction performed by the camera will pertain only to the image. The aperture plate is part of a film gate that is rotatably mounted so that the film may be supported in either a "horizontal" or "vertical" orientation, depending on how the film image was initially exposed.

Abstract: A color printing control system for making prints from negatives having a color printer and a microprocessor. The output of photocells which read color negatives is applied to the microprocessor enabling it to calculate print time signals. These signals are applied, for example, to paddles and move them into the light path to terminate light exposure. A print test probe reads the density of the prints and is coupled to the microprocessor and forms a feedback loop which allows the microprocessor to adjust its internal values. In this manner, color balancing is performed and prints made from over and underexposed negatives have the same density as properly exposed negatives, without knowledge of paper characteristics and without operator setup calculations.

Abstract: A distance detecting device comprising radiation projecting means for projecting a radiation beam; radiation sensing means which is disposed away from the radiation projecting means with a given length and is arranged to receive a reflected radiation beam coming from an object whose distance is to be detected as the radiation beam is projected from the projecting means; and movable means for relatively varying the incident condition of the projected radiation beam onto the sensing means. The distance to the object is found either by the position of the movable means or by the amount of displacement thereof which occurs at a time point at which the sensing means optimally receive the reflected radiation beam coming from the object in the process of relatively varying the incident condition of the projected radiation beam onto the sensing means.

Abstract: An image information detecting device for detecting the density for printing is required to cover a wide dynamic range corresponding to the density scope of the original film as well as to cover the fluctuation in values caused by different lamps and filters used in the photometric system. It is also important in photographic printing process to detect the density information on a relatively wide area of a frame of a negative film or the like in order to determine exposure or correction amount. The present invention enables the use of a storage-type light receiving element over a wide dynamic range as well as segmentation of picture images of a film of a wide scope into a large number of picture elements for detection.

Abstract: A circuit for reducing noise and increasing the reliability of touch panels involves the use of a supplemental noise or electromagnetic interference pickup lead which extends generally coextensively with the parallel connected outputs from a series of successively coupled photodetectors and a high pass filter for substantially reducing the noise signals created by variations in the level of ambient light. When the photodetectors output is connected to one of the inputs of a differential operational amplifier, and the compensating pickup lead is connected to the opposite polarity other input, the noise is substantially cancelled out, and a cleaned-up photodetector pulse is provided. A pulse forming circuit squares up the photodetector output signal pulse; and a hysteresis type storage or buffer 15 circuit is employed to indicate the presence or absence of photodetector output signals, from successive photodectors, thereby indicating whether or not the light beams are interrupted either fully or partially.

Abstract: Disclosed is a temperature compensation system for light measuring circuits. Said system compensates for the change, over temperature, of the output of the light measuring circuit by applying a bias source with a predetermined temperature coefficient. The system is designed so the bias voltage source is derived from the V.sub.BE (base to emitter voltage) difference between a pair of transistors, which difference is generated by the difference of current density at the junction of the pair of transistors obtained by flowing a pair of currents with a constant ratio independent of temperature.

Abstract: An improved digital photoelectric position measuring device of the type comprising a scale, a scanning unit for generating scanning signals, and an evaluating circuit for evaluating the scanning signals, wherein the scanning unit includes at least one photoelectric circuit comprising a pair of photosensitive elements for generating counterphase scanning signals, and wherein the evaluating circuit includes at least one pulse forming circuit response to the difference of the counterphase scanning signals. The measuring device includes at least one photosensitive element for generating a direct flux signal and a light source for illuminating the photosensitive element. The direct flux signal is applied to at least one photoelectric circuit in order to balance the pair of photosensitive elements independently of the evaluating unit.

Abstract: An automatic responsivity control (ARC) circuit compensates for the nonuniform deviation .DELTA.R in the average responsivity R of a column of photodetectors from a nominal responsivity R.sub.0 which is uniform from column to column. The ARC circuit first establishes a reference level by subtracting two known calibration signals occurring during optical retracing and then multiplies the reference level by each image signal occurring during optical scanning. The resulting product contains undesirable signal components or terms which are algebraic functions of .DELTA.R.sup.2 and other terms which are algebraic functions of .DELTA.R. The terms in .DELTA.R.sup.2 are ignored because .DELTA.R is significantly less than R.sub.0. The terms in .DELTA.R are eliminated by establishing a second reference level, which itself includes terms in .DELTA.R, and then subtracting the foregoing product from the second reference level.

Abstract: A sample and hold auto-zeroing feedback circuit is utilized to drive the dark current of a solid state photodiode to zero in the absence of incident light photons. The just previously attained compensation is then held during a subsequent quantitative measurement cycle when the photodiode is illuminated. Plural linear and/or non-linear signal processing stages may also be included within the auto-zero compensation feedback loop such that their normal offset errors are also simultaneously compensated.