Abstract: An avalanche photodetector having separate absorption and multiplication regions comprising Group III-V compound semiconductors is useful as a detector of small numbers of photons when it is operated with an above threshold bias voltage at ambient temperature.

Abstract: An X-ray image intensifier includes an input screen. The input screen has a base plate, a phosphor layer formed on the base plate, a transparent conductive film formed on the phosphor layer, and a photoemissive layer formed on the conductive film. The conductive film has a crystallinity wherein an average crystal size along a direction parallel to a surface of the conductive film is 500 .ANG. or more.

Abstract: A method for detecting a position wherein a signal outputted from a position detecting scale is detected by at least two detectors, an output value of a preceding detector of these two detectors is stored anew at the time when an output value of a following detector of the two detectors comes near a scale position on which the output value of the preceding detector is once stored and becomes equal to the output value of the preceding detector, and a position detecting signal is outputted, these steps being repeated to detect the position.

Abstract: A current injection compensation circuit for dynamically compensating for the effect of ambient conditions on phototransistor output is disclosed. An output voltage is maintained at a nominal reference voltage level independent of ambient light input to allow use of a large output for a detected signal. Phototransistor current is a function only of ambient conditions, especially incident ambient light and is unaffected by compensation current injection. The ambient compensation current injection network can be employed with interactive touch input devices, such as infrared touch entry systems used with video displays.

Abstract: A high speed light detection tube consists of a planar photoelectron source of transparent type, a photoelectron collection electrode arranged in parallel with the photoelectron source and an acceleration electrode of transmission type arranged in parallel with the photoelectron source in a space between the photoelectron source and the photoelectron collection electrode. The potential distribution has been set so that the photoelectrons passing through the acceleration electrode can be incident on the photoelectron collection electrode at a constant speed or near value.

Abstract: An optoelectronic incremental measuring system for measuring lengths or angles comprises a scale member provided with an incremental scale and a scanning unit, which is adjustable along the scale and comprises scanning grids, which are spaced apart by an integral multiple and a fractional part of a scale increment, a plurality of optoelectronic receivers associated with respective ones of such grids, and a plurality of light-emitting diodes, which are associated with the respective grids and adapted to illuminate the associated receiver via the scale and the associated scanning grid. In such a system a movement of the scanning unit and the scale relative to each other will cause the receivers to generate phase-displaced sine signals having periods in a number depending on the number of scale increments traversed by the scanning unit.

Abstract: A touch entry system employing arrays of emitter and detector opto devices located around the periphery of an irradiated field detects intrusion of an opaque element such as a stylus within the field. The detector analog output is converted to a digital signal for input into a microprocessor. Digital signals input into the microprocessor can vary due to inconsistencies in conventional opto devices. A programmable amplifier responsive to the microprocessors preconditions the analog signals prior to analog to digital conversion to bring all digital signals corresponding to the unblocked emitter beam condition within a normalized range before input into the microprocessor.

Abstract: The invention relates to a hand-held device for detecting whether or not an optical fiber is carrying a light signal. The device includes a spring loaded hook for grabbing an exposed optical fiber anywhere along its length, thereby introducing microbending, a photodetector for responding to the presence of light emitted in the proximity of the microbend, and a light emitting diode connected by way of an amplifier to the photodetector for indicating when a light signal has been detected. Upon release of the spring loaded hook, the fiber returns to its normal state. The device can be easily modified to indicate not only the presence of a light signal, but also the strength of the signal and the direction in which the signal is being transmitted.