An electronic analog gating means for an image intensifier in which transted pulsed illumination that is returned from targets down range are gated through the image intensifier in an analog manner according to the inverse square law in illumination drop off in distance. The image intensifier is enabled in distinct incremental time elements which correspond to and are inclusive within the time that it takes for illumination to travel to and from corresponding incremental depths of range. The distinct incremental time elements are produced by comparing a series of linear ramps, which are produced at the same frequency as the transmitted pulsed illumination, with an increasing parabolic square function curve that repeats every one-tenth of a second to produce at least ten viewings per second on the nearest target to eliminate flicker but producing an increasing number of viewings of increasing distant targets. The electronic analog gating means is duty cycled to permit illumination reflected from these targets to be amplified in proportion to the square of the distances to the targets, and thus provide an effective equal illumination of all targets down range. By changing certain portions of the parabolic curve, the effective illumination reflected from a selected range, represented by one of the incremental time elements, may be emphasized by gating the image intensifier on more often than normal at that specific incremental time element.
An improved active type of infrared viewing system is provided using pulse ated techniques which displays the complete Z (range) axis simultaneously and provides uniform image intensity at all ranges.
An electrooptical camera comprises an image intensifier connected to a control system for gate and scanning, which system includes a serial arrangement of a trigger oscillator, a master oscillator and an amplifier unit, which comprises preamplifiers and output amplifiers for the gate and scanning channels. The trigger oscillator is a relaxation oscillator utilizing an avalanche transistor and a storage capacitor in its collector circuit. The master oscillator is a Marx oscillator with an optical input and with cable line timing sections of different lengths in its collector circuits. The output amplifier of the gate channel is coupled to the gate system of the image intensifier. The output amplifier of the scanning channel is electrically coupled, via integrators, to a load in the form of a wide-band two-channel cable transformer/shaper, which is coupled to the deflection system of the image intensifier. The integrators utilize RLC-elements and can be inserted between the output amplifier of the scanning channel and its load, via a scanning time selector which includes sealed terminals.
A self-synchronizing optical radiation imaging device and optical delay circuit is provided with optics for receiving optical radiation and directing the radiation to an optical image delay system for delaying the optical radiation for a predetermined length of time. An optical radiation energy detector detects when optical radiation of a predetermined energy level has been received and actuates a gating circuit, which in turn, turns an image intensifier either on or off, depending upon the embodiment used, to coincide with the reception of the delayed signal by the image intensifier and to maintain the image intensifier on or off during the period that the receiving optics is receiving optical radiation of at least the predetermined level. An optical delay system is provided in which a bundle of incoherent fiber-optics of predetermined length are mounted to receive a signal at one end and a reflecting mirror is mounted to the opposite end for reflecting the received signal back through the bundle of fiber-optics.
A gating circuit for use with an image intensifier tube which allows the e to be turned on and off without producing residual image distortions, and when the tube is off eliminates scintillations on the image screen. The gating circuit provides for direct voltage control with the voltage across the cathode, anode, and the focusing electrodes of the image intensifier tube. The circuit includes a pair of triode vacuum tubes coupled together by a voltage divider network with an RC timing circuit controlling one tube which in turn acts as the bias and control of the other tube for turning the device on and off. The gating circuit is especially useful when utilizing an image intensifier tube in conjunction with photographic film which is time exposed to reproduce an image on the intensifier tube such that switching the tube on and off will not cause deleterious defocusing effects resulting in distortions on the photographic film. When the tube is off, scintillations which would reduce the quality of any photograph of the image will not be present because no voltage exists across the tube cathode and anode.
A low light level image pick-up tube is protected from excessive illumination intensity damage by controlling very high voltage generating means supplying the tube. The tube comprises in a preferred embodiment two image intensifier stages in cascade preceding an electron gun from which a video signal is provided by electronic scanning. A mean level video measuring circuit provides from the video signal a control signal used to produce on the one hand, a video regulation by varying the amplitude of a supply DC voltage provided to the second image intensifier stage, i.e. that preceding the electron gun, and on the other hand, a diaphragm effect by varying the amplitude and duration of a supply voltage provided by a VHV switched supply circuit to the input image intensifier stage. Further, the switched supply is controlled to cancel out instantaneously the gain of the input intensifier stage so as to protect the camera against sudden and too intensive illumination.
