Abstract: A processing circuit is provided for use in an optical combustion monitor for an internal combustion engine. The circuit includes a variable gain amplifier for amplifying a signal from one or more opto-electric transducers sensitive to combustion light in the engine cylinders. A gain control circuit including a peak detector controls the variable gain amplifier so that the peak amplitude of the amplifier output signal is substantially constant.

Abstract: A photoelectric switch is adapted for use as either a transmission type or a reflection type switch. To provide an integrated circuit for the photoelectric switch and to minimize input/output pins, multiple functions are assigned to each input/output pin. Such functions are provided via first to fourth integrated circuit input/output pins, i.e., the first pin serves functions in the supply of a detection output and a self-diagnosing output; the second pin supports a circuit for driving a projection type LED and a circuit for turning the LED off; the third pin supports a circuit for reversing a stable indication output and an operation indicating output; and the fourth pin supports a circuit for amplifying a received photo-signal and for controlling the mode of combination of photoelectric signals from a pair of photo-diodes.

Abstract: A photoelectric switch is adapted for use as either a transmission type or a reflection type switch. To provide an integrated circuit for the photoelectric switch and to minimize input/output pins, multiple functions are assigned to each input/output pin. Such functions are provided via first to fourth integrated circuit input/output pins, i.e., the first pin serves functions in the supply of a detection output and a self-diagnosing output; the second pin supports a circuit for driving a projection type LED and a circuit for turning the LED off; the third pin supports a circuit for reversing a stable indication output and an operation indicating output; and the fourth pin supports a circuit for amplifying a received photo-signal and for controlling the mode of combination of photoelectric signals from a pair of photo-diodes.

Abstract: An apparatus and method for controlling gain automatically uses a light receiving element, a gain amplifier, a difference amplifier, a controller and a variable level circuit. The light receiving element generates electrical signals corresponding to received optical signals. The gain amplifier amplifies the electrial signals and the difference amplifier generates signals corresponding to the difference between defined level of amplified signal and predetermined level. In response to output signals from the difference amplifier, the controller generates signals for controlling gain of the gain amplifier and multiplication factor of the receiving element. The level circuit supplies signals to the receiving element in response to output signals from the controller.

Abstract: An optical receiver circuit for an incoming optical signal having a variable power level includes an optical detector for receiving the optical signal and generating a current therefrom which varies with the optical signal power level. The current so generated is applied to a transimpedance amplifier. An automatic gain control (AGC) drive circuit is connected around the amplifier thereby increasing its dynamic range. The AGC drive circuit drives a FET which has one side thereof connected to the transimpedance amplifier for shunting current from the input thereof. A negative feedback circuit comprising an amplifier is connected across the FET, which comprises the resistive feedback element, thus reducing the FET resistance by a factor of 1+T, where T is the feedback circuit loop gain.

Abstract: The light reception signal circuit for photoelectric switch includes a photoelectric conversion circuit for receiving light from a light emitting part controlled for periodic emission. The photoelectric conversion circuit generates an electrical signal corresponding to the quantity of the received light. A programmable attenuator receives the output electrical signal, and attenuates it in even step in response to a digital control signal. A first comparator compares the output voltage with a predetermined upper bound threshold. The first comparator generates a clock signal when the output voltage exceeds the upper bound threshold. A peak holding circuit for receives an output voltage of the programmable attenuator, and holds the peak value of the output voltage on a time constant that is much longer than an emission period of the light emitting part.

Abstract: An optical data medium driving apparatus which constitutes amplifiers for an output current signal of a photosensor including a plurality of current mirror circuits having different amplification factors in order to switch, in a wide range, the output current signal of the photosensor. The photosensor detects a quantity of the reflected light corresponding to a variation of the quantity of reflected light from an optical data medium having various characteristics. The output is obtained with high accuracy and in a wide band. A servo-circuit is used for an AGC circuit and normalizes a difference signal from each light receiving surface at a photosensor having a plurality of light receiving surfaces. An A/D converter is given the difference signal as an analog input signal and the sum signal as the reference input signal. The A/D converter outputs an offset binary type digital signal, thereby being inexpensive to produce, easy to be integrated having high function, and high in reliability.

Abstract: A circuit for providing a signal representing light power received by a photodiode of an optical receiver having control means for controlling the bias voltage of the photodiode, wherein a constant amplitude low frequency current signal is superimposed on the photoelectric current of the photodiode, the resulting low frequency voltage signal being rectified and made available at an output terminal.

Abstract: In a variable high-voltage generating circuit for an avalanche photodiode, a pulse oscillating circuit generates pulses, a current driving circuit current-amplifies the pulses, a Cockcroft-Walton circuit boosts and rectifies the pulses from the current driving circuit, and a low-pass filter is connected at the output of the Cockcroft-Walton circuit. The avalanche photodiode is connected in series with a first resistor, and the series connection is connected to receive the output of the low-pass filter. A series connection of a transistor and a second resistor is connected in parallel with the series connection of the avalanche diode and the first resistor. A control circuit applies a variable signal to the base of the transistor, thereby to vary the voltage applied across the APD.

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: The specification discloses an audio signal level control system including a center-tapped photocell incorporated into an attenuator bridge. The cell elements are monitored while processing the audio signal, and a control circuit regulates the light-emitting device in the cell in response to the monitored bridge values. Preferably, log compression and filtering are performed within the control means. Also preferably, a tracking subtraction principle is used in both the audio and control paths to expand the control dynamic range.

Abstract: A combined optical power meter and receiver is provided in which the optical power meter retains high sensitivity and the optical receiver retains high bandwidth. A single photodiode provides current for both the optical power meter and the optical receiver. A first operational amplifier is configured as an integrating transimpedance amplifier having a current input which is referenced to a reference voltage and receives current from one port of the photodiode. A second operational amplifier is configured as a transimpedance amplifier having a current input which is referenced to ground and receives current from the other port of the photodiode. In this manner, a bias voltage is developed across the photodiode to decrease the capacitance and increase the operational speed of the receiver. A second material photodiode is provided which is shielded from the input light source is coupled to the current input of the first transimpedance amplifier.

Abstract: A circuit arrangement has a pre-amplifier that has its input connected to an opto-electric transducer and whose gain is controllable by a final control element formed by a field effect transistor. In order to achieve an especially great range of dynamics, the pre-amplifier contains the drain-source path of a field effect transistor that is connected in parallel to a resistor in a feedback branch. This field effect transistor is activated or inhibited by a regulator. In this way, the range of control of a controllable amplifier arrangement following the pre-amplifier is doubly utilized. The circuit arrangement can be advantageously used in optical transmission equipment of PCM technology.

Abstract: A sensor device for cumulatively storing incident light in the form of electric charge is arranged to monitor the level of the cumulatively stored electric charge; to have one mode in which the storing action is allowed to continue until the electric charge level reaches a first, high given level if the electric charge level reaches a preset level within a given period of time; to have another mode in which the storing action is allowed to continue until the electric charge level reaches the preset level if the electric charge fails to reach the preset level within the given period of time; and to cause a signal obtained by the storing action to be read out after the end of the storing action with a degree of gain which is variable according to the mode in which the storing action is performed.

Abstract: The image intensifier (22) of night telescope (12) is protected by a deactivate circuit (FIG. 4) which is in series with an off-on switch (S) between a source of electrical energy (28) and the image intensifier (22). The light sensor (26) measures ambient light. If the light level is below a predetermined light level, at which it is safe to operate the image intensifier (22), the light sensor (26) does not conduct. This causes an amplifier circuit (A-1, A-2) to deliver a negative voltage to the base of a transistor (Q-1). This enables the transistor (Q-1) to transmit electrical current from the source (28) to the image intensifier (22). Whenever ambient light exceeds the predetermined light level, the photoconductive sensor (26) conducts. In response to this happening the amplifier circuit (A-1, A-2) delivers a positive voltage to the base of the transistor (Q-1). In response, the transistor (Q-1) becomes incapable of transmitting a current onto the image intensifier (22).

Abstract: An optical high-impedance preamplifier for processing signals over a large dynamic and automatically operating control range. The automatic control is provided by a variable impedance which is arranged in series with the source circuit of a current-stabilized input MOSFET of the optical preamplifier. As a result thereof, no overloading or loss of sensitivity occurs at a high or low input level.

Abstract: An iterative and continuous normalizer for ensuring that the ejector rate of the slave channels in a fungible product sorter are operating at the same rate as a channel selected as the master channel. A distributed trip level value applied to a master channel comparator results in a rate of ejection of non-standard products that are counted to a predetermined count, at which time a master channel counter output is produced. In similar fashion, a slave channel output is produced; however, the comparator in the slave channel operates to an adjusted trip level value, which is the distributed trip level value adjusted by a multiplying factor. This multiplying factor is produced by a multiplier controlled by an up/down counter, in turn controlled up or down by whether the slave channel counter output or master channel counter output arrives first.

Abstract: A self-contained light sensor head (10) has a photodiode (18) operable to produce an electrical response proportional to light intensity, and an amplifier (20) that produces an output signal from the photodiode's response. The head (10) further includes a gain control circuit, for suitably controlling the gain of the output signal, and has noise and oscillation control circuits. The latter circuits permit the sensor to generate a low voltage output signal that is compatible for input directly to an analog computer.

Abstract: A very wide bandwidth, wide dynamic range amplifier incorporating a plurality of feedback paths which are parallel connected upon command is illustrated. The parallel connection is actuated from an input signal strength sensor which has built-in hysteresis so that there is no continuous switching from one feedback configuration to the other at a given input signal strength. The design of the switch feedback path is such that there is very low capacitance at the input of the amplifier, and a single signal peaking compensation circuit can be used to prevent undesirable signal peaking in the response curve.

Abstract: An image reader, comprises a plurality of photosensors which photoelectrically convert incident light from an object to be read, a memory for storing, as correction reference data, data corresponding to photoelectric conversion outputs from said photosensors when said object to be read presents a uniform halftone image, and a correction circuit for obtaining uniform photoelectric conversion output levels among said photosensors using the correction reference data.

Abstract: A circuit is described which can be used to record rapidly occurring faults in a slowly reacting circuit which is self compensating so that the photoelectric light emitters used in the circuit have their flux maintained constant.

Abstract: A controller controlling the dispensing of paper currency including a microprocessor for controlling motors which feed a predetermined mix of paper currency from each dispensing device to a common acceleration device which advances bills to an output stacker. Each individual dispensing device dispenses the proper number of bills to the acceleration device. Apparatus multiplexes the control signals to the stepper motor. After the bills have been dispensed, the stepper motor is halted, and a home positioning sensor determines if the stepper motor has been halted in the proper position. Sensors provided at spaced intervals along the common acceleration device determine if bills have reached the acceleration device. The dispensing operation is repeated if bills do not reach the sensor. The sensors perform the dual function of sensing advancement of a bill and detecting overlapping or multiple fed bills. The adaptive technique conmpensates for changes in the sensor such as component aging and dust accumulation.

Abstract: A focus control system with a novel gain control circuit for continually varying the gain of the focus error signal based on the optical characteristics of the medium. As those optical characteristics change to decrease the amount of light available to the focus error detector, the gain of the focus error signal is increased so that the overall gain of the servo loop and the overall response of the servo to a focus error remains constant. This is accomplished by monitoring the optical characteristics of the medium which affect the focus error detector. In a multiple detector system, the outputs of all of the detectors are summed together. The resultant signal is a reflectivity or a transparency signal and is used in a novel circuit for controlling the servo gain.

Abstract: An optical detector is provided. The optical detector provides automatic zeroing of a logarithmic ration function in applications such as absorption meters, fluorometers and other chromatographic techniques.

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: This invention relates to an automatic range control method for a compact and portable optical density/dot percentage measuring device which can use a conventional light table as its light source, and which can digitally display a result of measurement. In the method, information obtained from an A/D converter, which converts a measured analog signal to a digital signal, is positively employed for reducing overall measuring time. An A/D conversion is first made at x1 range by a 10 bit A/D converter. The A/D conversion value is compared with predetermined values to determine a gain to be selected and perform further A/D conversion.

Abstract: A digital gain controlled current to voltage amplifier having particular utility for interfacing with and forming part of a spectrophotometer system with a photomultiplier tube being responsive to light for producing an analog current proportional to the intensity thereof. The digital gain controlled current to voltage amplifier incorporates a current switched multiplying digital-to-analog converter inside its feedback loop. In this manner, the feedback loop impedance may be maintained constant as its gain is varied under control of a software programmed microcomputer.

Abstract: The present invention is concerned with a self-adjusting document sensor compensating for degradation of the sensor system. A suitable light source and a detector are provided, the output of the detector being fed into an amplifier whose gain depends upon a feedback signal. Periodically, the output of the amplifier is compared to a reference. If the output of the amplifier falls below the reference, a pulse is sent to a ripple counter whose digital output is fed back to the amplifier to change the gain of the amplifier. If the detector is an unbiased photodiode operating in the transconductance mode, the leakage currents and their subsequent effect on output with amplifier gain changes will be minimized.

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: Gain of a photosensitive avalanche member, such as an avalanche photodiode, is stabilized so that a variation in gain of the photosensitive member in terms of temperature is compensated for by applying to the photosensitive member a bias voltage varying with temperature according to a predetermined relationship. The relationship depends on the variation with temperature in the voltage applied to terminals of at least one diode. The gain stabilizing device comprises a temperature-stabilized voltage source, a dc-dc voltage converter having an adjustable gain for applying a bias voltage to the photosensitive member, and at least one diode series-connected between the supply source and an input of the converter.

Abstract: A gain adjuster circuit is disclosed for adjusting the gain of a plurality of photomultiplier tubes (PMT's) by digital circuitry. The circuit includes a plurality of PMT's, each having a specific internal resistance. A plurality of switches and resistances are connected in series with the PMT's. The digital circuitry is designed for adjusting the effective resistances thereof, to adjust thereby the voltage across each of the several PMT's. Preferably, the digital circuitry includes a demultiplexer coupled, via the switches and resistances, to the PMT's, a flip-flop coupled to the demultiplexer, and a presettable counter coupled to the flip-flop.

Abstract: A nonintegrating, high sensitivity, wide dynamic range receiver is described. A voltage dependent current source is connected in negative feedback with a forward voltage amplifier. The transconductance of the current source is essentially independent of frequency within the signal bandwidth frequency, and the feedback pole is the dominant pole in the loop gain. To prevent saturation by high intensity input signals the receiver is combined with a range extender circuit.

Abstract: Apparatus for controlling output signals from two light detectors in a photometer. The sensitivities of the light detectors, or the gains in amplifiers for amplifying output signals from the light detectors are controlled in such a manner that the sensitivity characteristics and output characteristics of the two light detectors are in agreement with one another, to thereby improve the measuring accuracy thereof.

Abstract: Circuitry for optimizing the signal-to-noise ratio of a light receiving circuit having an avalanche photo diode to receive the light and an amplifier connected thereto to provide an output signal, the level of the output signal being kept constant despite variations in the light input level by controlling the multiplication factor of the avalanche photo diode and the gain of the amplifier. For this purpose, when the light input level is low, the multiplication factor control voltage for the avalanche photo diode is controlled through a loop which includes a differential amplifier, a diode, and a high voltage generator circuit.

Abstract: An optical receiver comprises a photodiode (1) which is connected to a biasing circuit (2), and also to the output (14) of the receiver via the series arrangement formed by a preamplifier (3), a control amplifier 4 and an output amplifier (5), the output of the receiver being connected to the control input 10 of the control amplifier (4) via a detector (6) and a differential amplifier (9). The control amplifier (4) is what is commonly referred to as a differential controller, in which alternating current and direct current are processed in the same manner. As a consequence thereof, it is possible to determine the optical input level of the receiver continuously at the output of the control amplifier by means of a simple ammeter (8).

Abstract: A method and system for automatically calibrating a D.C. transducer are described in the environment of an illustrative film retrieval system. In this system, the output of a transducer such as a light sensor is amplified and the amplified output is compared to upper and lower limits within which it is desired to hold the transducer's amplified output. When either of the limits is exceeded, the amplification of the transducer's output is varied so as to shift its average value to a value which is between the upper and lower limits.

Abstract: A light monitoring arrangement, specifically one for monitoring relatively high frequency light pulses and producing corresponding electrical output pulses, is disclosed herein. This arrangement includes circuitry which has the tendency to become electrically saturated if the light pulses being monitored reach or exceed a certain minimum intensity level. This in turn distorts the electrical output pulses in a way which causes these pulses to merge with one another. However, the arrangement disclosed herein also includes circuitry for preventing this from occurring even if the light pulses do reach or exceed circuit saturating intensity levels.

Abstract: A device and method for measuring blood characteristics and parameters, especially arterial, venous, or differential blood oxygen saturation levels uses one or two probes containing a unique configuration of light emitters of two different wavelengths, and sensors which alternately illuminate and read reflected light from blood passing through a specially-designed cuvette. Electronic comparison of reflected radiation received by the probes produces a voltage which is linearly related to blood oxygen saturation level. An opto-electronic feedback network compensates for differences in blood optical density.

Abstract: An optical grating signal system for an use in a document recording system is shown having an acousto-optic modulator which utilizes the zero order beam of the modulator to scan a grating and a grating signal detector. When a modulating signal is applied to the acousto-optic modulator to generate a first order beam that records information, the intensity of the zero order beam is diminished. The same modulating signal is also applied to an amplifier which amplifies the output of the grating detector to increase the gain of that amplifier and thus maintain its output at a constant envelope level as the intensity of the zero order beam diminishes. The optics normally required to create a separate grating scanning beam are thus eliminated.

Abstract: Control apparatus for controlling the quantity of light includes a light emitting device for emitting light in response to a driving signal applied thereto, a photodetector for receiving the light to produce a detection signal representative of the quantity of the light received, a comparator for comparing the detection signal with a reference signal, a circuit for applying a recording signal to the light emitting device, a start control responsive to an instruction signal which causes the control apparatus to start controlling the quantity of light during the time period when no recording signal is applied, an incrementing device for incrementing the driving signal to be applied to the light emitting device in response to the instruction signal received, and a stopping circuit for stopping the incrementing in response to the comparator to hold a count which is contained in the incrementing device when stopping, until the instruction signal is subsequently applied.

Abstract: In the distance measuring system disclosed, light reflected from an object is converted into an electrical signal and processed to detect the distance to the object. Before the distance detecting operation, a signal level detecting operation is carried out in the distance measuring range and the gain of the signal processing or the amount of light for illuminating the object is automatically set for the distance detecting operation.

Abstract: An optical receiver having enhanced dynamic range is achieved through the use of a variable impedance shunt 203 disposed at the receiver input. The optical receiver comprises an optical detector 102 serially connected to a transimpedance amplifier 201. The optical detector 102 receives an optical signal having a variable optical power level and modulation bandwidth and generates a corresponding electrical current therefrom. The transimpedance amplifier provides a fixed amount of gain and converts the electrical current to an output voltage. An automatic gain control circuit 202 produces a control signal which varies in response to the amplitude of the output voltage. The control signal is applied to the variable impedance device to vary the impedance therein. This maintains the output voltage at a predetermined amplitude over the modulation bandwidth without any significant reduction in receiver sensitivity.

Abstract: An adaptive gain integrator circuit is provided having a first integrator for producing an output which is proportional to the ambient light noise level and the amplitude of the laser illumination signals applied thereto. A second feedback circuit having a noise-only integrator is provided to maintain the noise level applied to the first integrator substantially constant despite wide variations in the amplitudes of ambient light detected by the system, thereby to reduce the false alarm rate and increase the sensitivity of the system.

Abstract: A laser inspection system is provided having an absolute closed loop dc system in which the power gain is automatically stabilized. In order to stabilize the power gain of the system and provide a closed loop absolute reference dc level, a sample of the radiation from the laser beam utilized to scan the material being inspected is applied to a photomultiplier tube for generating a reference pedestal signal which is dependent on the intensity of the laser beam and is free of the influence of the characteristics of the material being inspected. The reference pedestal signal is applied to a comparator which develops a control signal which is applied in a single closed feedback loop including in effect, the laser source and the light collection and detection system within the loop. This loop includes the photomultiplier tube and its high voltage power supply to which the control signal is applied for stabilizing the gain of the system.

Abstract: A heat detector having automatic gain control in relation to changes of time constant different from that of the changes to be detected, comprises an outer feedback loop including the light path between emitter (10) and detector (14), and an inner feedback loop (40,42,44) around the emitter drive circuit. The inner feedback loop contains an exponential element (42). The exponential response of the inner loop feedback circuit makes the open-loop gain and the time constant of the system invariable in spite of differences in the light path, for example in different installations.

Abstract: A system (10) for optimizing the gain of an avalanche photodiode (12) and an associated avalanche photodiode preamplifier (14) includes a variable voltage power supply (58) interconnected to the avalanche photodiode (12) for providing a bias voltage source for the avalanche photodiode (12). Circuitry (26, 28) is provided for measuring the output noise level of the avalanche photodiode (12) and preamplifier (14). Additional circuitry (46, 48) is responsive to the circuitry (26, 28) for measuring the output noise level of the avalance photodiode preamplifier (14) for generating a control signal.

Abstract: An improved circuit for an optical smoke detector utilizing an active band pass filter which has a bias feedback to the phototransistor detecting element to bias the phototransistor to a static conductivity state of high gain or high sensitivity without regard to whether the phototransistor is in a high ambient light level or a low (dark) ambient light level.

Abstract: The invention relates to optical inspection apparatus for monitoring a continuously moving rod, the apparatus comprising a circular head through which the rod passes, a first set of fibre optic conductors which transmits light from a source to the head to illuminate the rod, and a second set of fibre optic conductors which pick up light reflected from the rod passing through the head and transmits the reflected light to a number of photoelectric elements. The second set of conductors are divided into angularly spaced groups around the head and adjacent groups lead to separate photoelectric elements. The outputs of the elements are fed via A.C. coupling means into separate channels connected to comparator means responsive to the noise signal level in the individual channels. The comparator means produces a fault pulse in the signal level in any one channel is greater than a preset allowable level.

Abstract: A power supply for a microchannel image tube. Microchannel plate voltage is controlled, to adjust tube gain, as an inverse function of screen current in an intermediate illumination range. In addition, the photocathode plate voltage is controlled as a function of screen current in a second illumination range. The said second illumination range including higher illumination values than said first range and the lowest illumination value in said second range is at least equal to the minimum illumination value in said first range.

Abstract: A gain controllable amplifier wherein a plurality of signal paths are proed with each of the signal paths having predetermined different gain characteristics. The gain of the total amplifier is selected by application of power supply voltages to amplying stages of the different signal paths with the combination of the level of the voltages determining which signal path will be operational and the total gain of the amplifier.