Abstract: The dynamic range of an image intensifier camera may be extended by using an automatic exposure control system which, in response to imager output (for example, the output of a charge coupled device (CCD) imager included in a solid state image intensifier camera), (a) generates a first control signal that controls the gain of the I.sup.2 Tube itself; (b) generates a second control signal for selectively gating the I.sup.2 Tube on or off; and (c) generates a third control signal for controlling a light attenuator that, according to a preferred embodiment of the invention, is included in the camera. The automatic exposure control system contemplated by the invention has a control range in excess of 10.sup.10 .times.; takes a measurement of the exposure from an imager (again, for example, a CCD sensor) for comparison to a desired setpoint; the measurement used may be a peak, an average or some weighted function and the automatic exposure control logic then adjusts, in order, the I.sup.2 Tube gain, the I.sup.

Abstract: Charge transfer devices typically include a periodically reset floating element output stage coupled to an FET amplifier for sensing the transferred charges. For reducing both low-frequency l/f noise and high-frequency reset noise, the duty factor of the device clocking signals and the reset signal are picked so that at a selected multiple of the clock signal repetition rate, the information component is in phase quadrature with the reset noise component. The charge transfer device output signal is then synchronously detected with a reference signal which is in phase with the selected multiple of the information component.

Abstract: In a television camera including an imager of the field-transfer type having A, B and C registers, an indication signal representative of dark current response accompanying the video signal is generated by comparing first and second signals representative of charge packets derived from the B and C registers, respectively. Specifically, the first signal is generated when the C register supplies signals supplied from the B register which includes substantially no photo-responsive components transferred from the A register. The second signal is generated when the C register supplies signals after the signal supplied from the B register have already been read out and while no new signals from the B register are being transferred into the C register and therefore represents absolute black.

Abstract: Output signal samples from a solid-state imager, responsive to dark currents accumulated therein, are applied to slope responsive circuitry for generating a signal which can be used, for example, for field shading correction or imager temperature control. Dark current slope responsive measuring circuitry is particularly advantageous over prior dark current measuring circuitry since it is uneffected by DC offset of the dark current signal which results from imager mask misregistration or carrier diffusion when receiving radiant energy.

Abstract: A black-level clamp for a signal derived from a transducer such as a camera tube includes a controllable voltage offset generator such as a series capacitor or an amplifier. The television signal is sampled during the horizontal sync interval to produce a control signal indicative of the current black-level signal, and the control signal is applied to adjust the charge on the series capacitor to place one plate at a reference voltage or is compared with a reference level to produce a further control signal for adjusting the offset of the amplifier. In either case, drift of the reference voltage which may perturb the operation of the clamp is reduced by deriving the reference voltage from the television signal at times within the vertical blanking interval.

Abstract: A system for controlling beam current in an image pickup tube so as to prevent comet-tailing and blooming of highlights in the imaged scene. The video signal derived from the image pickup tube (12, 14, 16) is fed back to the beam current control circuitry (22, 24, 26) so that the beam current varies with the video signal. A non-linear amplifier (20) included in the feedback loop has low gain for normal video signals and greater gain for highlights in the video signal. This reduces normal beam current overhead and thus extends the useful life of the tube. The feedback signal provided by the amplifier (20) is a current signal in order to simplify the addition of a DC component to it. A resistor (54) and voltage source (56) perform the addition of the DC component. When multiple image pickup tubes (12, 14, 16) are used, a non-additive mixer (18) combines the plural video signals to provide the amplifier (20) with a signal representative of the video signal of greatest intensity.

Abstract: An amplitude compression circuit for de-emphasizing variations in amplitude of a wide band electrical signal. A gamma circuit is used to compress amplitude variations in the wide band signal. A linear signal is subtracted from the compressed signal, producing a difference signal which represents the portion of the compressed signal resulting from the compression process. The difference signal is multiplied by a controlled factor and then added back to the unprocessed wide band signal to produce a second compressed signal. By varying the controlled multiplication factor, the amount of compression of the second compressed signal is linearly and controllably altered. To prevent emphasizing the noise portion of the signal, the wide band signal is cored before processing by the compression difference circuit. The coring circuit removes noise by subtracting the low amplitude, high frequency portion from the wide band signal.

Abstract: Automatic centering apparatus for use in a television camera having first and second video pickup devices for registering the video signals produced thereby. A first delay circuit responds to the first video signal to provide a first delayed signal, and a second delay circuit responds to the second video signal to provide a second delayed signal. The second delay circuit provides a time delay substantially equal to twice the delay provided by the first delay circuit. If the undelayed first and second video signals are registered properly, the delayed and undelayed second video signals are misregistered by equal yet opposite amounts from the first delayed signal. Relative misregistration of the two signals is detected by subtracting the delayed first video signal from the delayed and undelayed second video signals, and then clipping, integrating and comparing the two difference signals.

Abstract: An automatic iris control for a television camera has a peak detector for producing a peak signal, representative of the illumination level on the imaging tubes, from the video signal. At least one range comparator is included to compare the peak signal with an acceptable signal range. Two command signals, indicating high out of range and low out of range conditions, are produced thereby. A digital counter responds to out of range conditions by counting upwards or downwards in dependence upon the command signals. A digital to analog converter decodes the digital output of the counter into a corresponding analog signal. A D.C. controlled iris servo opens the iris an amount proportionate to the analog signal. The light admitted through the iris is thereby contained within acceptable limits.