Lockheed Martin Corporation

Martin Marietta Corporation

Other

Sparton Corporation

Adic, Inc.

Actran Systems, Inc.

Robert James Martin

Kevin L Brown

Barry L Lane

Terrance L Worchesky

Kenneth J Ritter

Gene Raymond Loefer

Peter Falter

Tom Faska

Mark West

Kirk Reiff

Gregory L Milne

Claude Sims

A photoconductor read out circuit includes a biasing signal generator connected to apply an alternating current biasing signal to a first terminal of the photoconductor. An input capacitance connected to a second terminal of the photoconductor stores charge applied to that terminal. A charge transfer amplifier included in the read out circuit receives a demodulating signal and functions to transfer charge to a summing node in response to the charge stored by the input capacitance and in coordination with the demodulating signal. A charge collection arrangement included in the read out circuit selectively resets the summing node to a base charge level, and stores charge applied to the summing node between resets to the base charge level. A sampling arrangement included in the read out circuit selectively applies a charge from the summing node to an output node, selectively presets the output node to a base output charge level, and stores charge applied to the output node between presets to the base output charge level. The charge stored at the output node between presets represents an output data signal from the read out circuit.

Method of operating a photoconductor in an imaging system, and read-out circuit employing an AC-biased photoconductor

An optoelectronic device has a bright detector and a dark detector and reduces noise in the output of the bright detector using the output of the dark detector.

Optical receiver device and method

An infrared photodetector includes at least two quantum well layers with depths adjusted to provide different peak spectral responses. A readout circuit includes first and second charge wells for receiving moving charges from the photodetector. The readout circuit also includes a switching mechanism for selectively switching the second charge well in parallel with the first charge well, to vary the integration time of the moving charges. Switching the second charge well in parallel with the first charge well increases the dynamic range of the system. The switching can be based on one or more of a) a range to a target that is being detected by the photodetector, b) a brightness (e.g. in the infrared range) of the target, c) a rate charge of the first charge well, and d) a remaining capacity of the first charge well.

Circuit and method for varying the integration time of moving charges from a photodetector

A quantum well infrared photodetector focal plane array is disclosed wherein each detector structure of the array comprises two vertically stacked quantum well layers. Each of the quantum well layers are individually biased by separate bias voltages and the separate bias voltages are modulated to produce two or more measurements at different spectral bands. Each detector structure of the array can therefore perform measurements of incident infrared energy in at least four separate spectral bands. This technique of measuring incident infrared energy in four separate spectral bands can advantageously be applied to the discrimination of hot gas sources from background infrared clutter.

Clutter discriminating focal plane arrays

An infrared photo-detector focal plane array includes detectors with quantum well layers that are spectrally &ldquo;tuned&rdquo; to impinging radiation by modulating the voltage biases applied across each quantum well layer. Read out circuits, interfaced with each detector of the array, process the photo-currents received from each detector to determine the absolute temperature of the remote infrared source from which the impinging radiation originated.

Remote temperature sensing long wave length modulated focal plane array

A quantum well infrared photodetector includes a direct connection between the charge well and detector that induces a nonlinear dynamic bias. This dynamic bias advantageously corrects for nonuniformity in the conductance of the detector.

Integral charge well for QWIP FPA'S

An infrared photodetector focal plane array includes large dynamic range Read Out Integrated Circuits. Increased dynamic ranges are achieved in each ROIC of the array using switched capacitor filter arrangements that include a single &ldquo;cup&rdquo; capacitor and at least two &ldquo;bucket&rdquo; capacitors. Dynamic range is improved by controlling the ratio of the current to voltage transfer resistance gains between the &ldquo;cup&rdquo; capacitor and each &ldquo;bucket&rdquo; capacitor of the filter. With an increased dynamic range, the switched capacitor filter arrangement allows the focal plane array to adequately resolve the infrared radiation received from both hot and cold objects.

Large dynamic range focal plane array

A quantum well infrared focal plane array achieves hyper-spectral measurements of incident infrared radiation using a voltage dividing network that applies different and adjustable biasing voltages to each line of the line by column array. The peak wavelengths of each quantum well layer of each detector structure in the array is set to a specified nominal value by appropriate fabrication of the depths of the quantum wells of the layers. The nominal peak wavelength value of each quantum well layer can further be varied by modulating the bias voltage applied to the gate of the direct injection transistor associated with each detector structure of the array. A read out integrated circuit (ROIC) containing the direct injection transistor processes the photo-current from each quantum well layer of each detector structure. Using an n by n array of vertically stacked detector structures, along with the associated ROIC, a focal plane array can be fabricated where each row of detector elements in the array is responsive to different peak wavelengths.

Programmable hyper-spectral infrared focal plane arrays

Exemplary embodiments of the present invention use a vertically stacked quantum well infrared detector where each &ldquo;tuned&rdquo; quantum well of the detector can be biased separately from any other quantum well of the detector. The vertically stacked detector can include three or more quantum well layers that are &ldquo;tuned&rdquo; to different peak wavelengths to permit detection of infrared radiation of three or more different bands or colors. The simultaneous detection of infrared radiation in three or more different spectral bands permits the determination of more information about an infrared source.

Three color quantum well focal plane arrays

A quantum well infrared photodetector includes a direct connection between the charge well and detector that induces a nonlinear dynamic bias. This dynamic bias advantageously corrects for nonuniformity in the conductance of the detector. In another feature, the charge well is fabricated on the detector element by adding an extra contact layer and a dielectric layer to a standard quantum well. Very dense focal plane arrays can be produced by making the charge well a part of the infrared detector.

Integral charge well for a QWIP FPA

A detector array of a plurality of photodetector cells is provided which operates in two spectral bands by utilizing a polarity reversing multiplexer for directly reversing the polarity of different types of photodetector pairs. More particularly, long wave photoconductive quantum well detectors and near infrared photovoltaic detectors may be advantageously interconnected to supply the two detectors with different bias voltage levels by a polarity reversal function. This polarity reversal function exploits the low and high impedance characteristics of the detectors for enhancing the electrical interconnection. As a result, the system optimally changes the operation of the detector array from one photospectral band to another to take advantage of the electrical interconnection characteristics of both devices. As a further advantage, the circuitry used may be simplified for eliminating bias lines. Thereby, the fill factor of the sensor array is increased by reducing the number of connection nodes or bumps to bias lines which provides a larger active area for the sensor array.

Dual band polarity reversing multiplexer

Apparatus for and method of increasing the effective integration time, and, hence, reducing the noise bandwidth of a photodetector. The current output of the photodetector is converted to a voltage signal in a low pass filter. The low pass filter is preferably implemented as a switched capacitor filter.

Apparatus for and method of providing long integration times in an IR

A SAR radar has an optical processor which uses an electrical-signal-to-light modulator. The modulator includes a tapped delay line which may be either analog or digital, and the signals tapped from the delay line are applied to an array of temporary storage elements, which in the case of analog signals may be a capacitive sample-and-hold, or for digital signals may include storage registers. In order to improve the signal-to-noise ratio (SNR) by comparison with a processor using an acoustic modulator, the signals tapped from the delay line are sampled at a display sampling rate, which is very low by comparison with the signal sampling rate or the highest frequency of interest, and the sampled signals are held until the next following display rate pulse. The signals held in the temporary storage elements are applied to the modulator elements, so that the optical pattern remains fixed for relatively long periods of time during which the optical processing can integrate photons for improved SNR.

Mutiple-clock controlled spatial light modulator

The electronically tuned power oscillator (ETPO) of the present invention provides a method and apparatus that drives a narrow-band (high Q) transducer over a relatively broad band of frequencies. A pseudo-random sequence generator dynamically switches a bank of capacitors varying the resonant frequency of the power oscillator. A node on the power oscillator provides the clock for the pseudo-random sequence generator thereby providing a synchronized frequency change on every time varying cycle.

Electronically tuned electro-acoustic power oscillator

An acoustic transducer, especially adapted for hydrophones, is disclosed. The transducer comprises a piezoelectric ceramic disk with a main or signal electrode, a common electrode and a feedback electrode; negative feedback is provided around an associated amplifier and the transducer. The transducer is useful in either a sonic receiver or a sonic transmitter. Various ceramic disk configurations are disclosed and several electrode configurations are disclosed. The negative feedback minimizes the undesired effects of the high Q characteristic of the piezoelectric ceramic transducer. The transducer exhibits improved frequency response characteristics including increased bandwidth and reduced resonance effects, fixed or linear phase shift over a broad range and improved transient response. Also, the effect of normal manufacturing variations upon sensitivity, frequency and phase response is minimized.

Growing community of inventors

Orlando, FL, United States of America

Robert James Martin