Abstract: Photo-electric detector comprising a multivibrator with two complementary transistors (T.sub.3 and T.sub.4) of which the base of the first is coupled to the collector of the second by a time constant circuit (R.sub.5 -R.sub.6 -C.sub.1) comprising a resistance (R.sub.5) with negative temperature coefficient. This multivibrator excites an electro-luminescent diode (D.sub.1) which cooperates with a photo-transistor (T.sub.1). After integration, the received signals control a commutator (thyristors Th.sub.1 and Th.sub.2). The circuit is fed by a rectifier bridge with diodes (D.sub.11 to D.sub.14) and formed with two wires.Application to the detection of the presence of an object which blocks the luminous beam emitted by the diode (D.sub.1).

Abstract: An apparatus for, and a method for, achieving temperature compensation of an avalanche photodiode. The apparatus and method automatically detect the breakdown voltage of an avalanche photodiode immediately before the photodiode is operated and automatically applies the photodiode with a bias voltage always lower than the breakdown voltage of the photodiode, so that the multiplication factor of the photodiode is maintained constant.

Abstract: A method for masking on the display device associated with a thermal telescope for the night guidance of self-propelled missiles carrying an infrared source, the image of a source of relatively intense stray radiations, wherein, on the one hand, the radiations transmitted in the field of vision of the thermal telescope are simultaneously detected in two different spectral bands, of which the one, called the useful band, corresponds to the maximum radiations from the target and the surrounding landscape, and the other one, called stray band, corresponds to the maximum radiations from the intense infrared sources carried or not by the missile, and on the other hand the signal detected in the first band is corrected by the signal detected in the second band in a manner to leave out the stray portions of the useful signal.

Abstract: Described is a temperature compensation circuit comprising a transistor, a device (to which compensated voltage is to be applied) connected to the collector, and a plurality of resistors forming a voltage divider. A node separates the resistors into two branches and is connected to the base, and a temperature sensor having a negative temperature coefficient of resistance is located in one of the branches. The branches are mutually adapted so that the ratio of the resistance of the branch containing the sensor to the sum of the resistances of both branches is a linear function of temperature. An application of this circuit to the control of the bias voltage supplied to an avalanche photodiode is specifically described.

Abstract: The disclosure is of a light-responsive electric switch which is characterized in that it is constituted mainly by a photoresistive cell inserted in a voltage-divider bridge of which the voltage variations, as functions of the illumination, control a standard integrated circuit comprising four NAND gates which, through the intermediary of a transistor, actuate a triac controlling the illumination circuit.

Abstract: A circuit useful in replicating the current produced in a photo diode operated as a current source at zero bias. A second scaled area photo diode is used to bias the circuit to maintain the zero bias over a wide range of illumination levels. The circuit operates in the picoampere range and is linear over at least six orders of magnitude.

Abstract: A control system is described for converting the output current of a photosensitive image detector to an image location voltage of predetermined first and second levels in response to the image detector receiving high and low levels of light, respectively. The image location voltage is developed by passing the output current from the image detector, as well as a selectively variable control current, through an impedance such that increases and decreases in the amplitude of the control current result in corresponding decreases and increases, respectively, in the level of the image location voltage. To change the level of the image location voltage, the amplitude of the control current is caused to be proportional to the charge on a charge storing element and the latter is rapidly and alternately charged and discharged within predetermined limits to vary the amplitude of the control current, and thus the level of the image location voltage.

Abstract: A photoelectric current log-compression circuit includes a log-conversion diode, a photodiode and an operational amplifier for log-compression. In the negative feedback circuit of the operational amplifier is inserted a thermistor to control the amplification degree of the operational amplifier according to the current flowing through the log-conversion diode. Further, a forward voltage of a temperature compensating diode biased with a constant current is applied to the reference voltage of the operational amplifier.

Abstract: An automatic zeroing circuit normalizes a detector-measuring apparatus to eliminate relatively steady-state DC errors that may develop in response to the temperature or other variable parameter dependency of leakage currents in a transducer, such as dark currents in a photosensitive transistor. Therefore, the outputs from such apparatus are generally insensitive to such variables and errors.

Abstract: In an imaging system, a radiation detector which scans an image has it output amplified by a D.C. preamplifier and to neutralize low frequency noise and drift the preamplifier output is amplified by a further D.C. amplifier having a feedback capacitor and to which a reference voltage is applied the further amplifier output being applied as a second input to the preamplifier. A sample and hold switch controls the application of the preamplifier output to the further amplifier, this switch being closed only during the dead times between consecutive scan lines.

Abstract: A temperature compensating device for use in regulating the voltage to a lamp in a lightfastness tester. The device includes a plurality of aluminum-coated glass rods adjacent the lamp for transmitting the light produced by the lamp to a light-receiving element, such as a photoelectric cell. A heat-sensitive resistance is electrically connected to the light-receiving element and compensates for changes in temperature of the light-receiving element. An electric circuit is combined with the light-receiving element and the resistance to receive the temperature adjusted voltage from the light-receiving element and the resistance and to compare that voltage with a reference voltage. In turn, the voltage to the xenon lamp is adjusted based on the difference between the two compared voltages.

Abstract: In a logarithmic amplifier employing a log-diode connected across an operational amplifier, a dividing resistor and a transistor circuit are connected in parallel between the output of the operational amplifier and the log-diode. The temperature characteristic of the log-diode and that of the transistor circuit cancel each other to effect temperature compensation in the output of the operational amplifier.

Abstract: A spectrofluorometer providing wavelength correction by means of an arbitrary function generator driven by a wavelength scanning element of the spectrofluorometer. The arbitrary function generator may be driven by the emission scanning monochromator to derive a wavelength-dependent voltage signal which is combined with the measure photomultiplier output to thereby provide a base-line compensated resultant output signal. Alternatively, the arbitrary function generator may be driven by the excitation scanning monochromator to derive a wavelength-dependent voltage signal which is combined with the output of a reference photomultiplier tube receiving part of the output of the excitation monochromator to derive an excitation-corrected reference signal which is in turn combined with the measure photomultiplier tube output signal to thereby provide an energy-corrected resultant output signal.