Hughes Aircraft Company

Sperry Rand Corporation

Colin G Whitney

Bruce A Cameron

Donald H McMahon

David H Chow

Michael Y Pines

James S Duncan

A controllable infrared filter (22) includes a quantum well filter unit (24) operable to absorb infrared energy at a selected wavelength. The quantum well filter unit (24) has a quantum well layer (26) made of an infrared transparent semiconductor mate rial and a barrier layer (28, 32) of another infrared transparent semiconductor material epitaxially deposited on each side of the quantum well layer (26). There is structure for controllably introducing charge carriers into the quantum well layer (26), which may utilize a source of electrons from other semi conductor layers (36, 38) and an applied voltage, or may utilize a laser (76) that generates charge carriers in the quantum well layer (26). The filter (22) further includes a lens (44, 46) or other optical system for directing infrared radiation through the first barrier layer (28), the quantum well layer (24), and the second barrier layer (32). Fixed band pass optical filters may be used in conjunction with the controllable quantum well filters.

Quantum well infrared filter

A two-color focal plane array sensor arrangement (10) operative to simultaneously sense optical energy within first and second wavelength spectra from a scene within a field of view is disclosed herein. The sensor arrangement (10) includes a telescope (12) for collimating the optical energy within the field of view into first and second substantially overlapping beams. The first beam includes optical energy within the first wavelength spectrum, and the second beam includes optical energy within the second wavelength spectrum. A wedged beamsplitter (14) having a pair of non-parallel reflective surfaces (34, 36) redirects optical energy within the first and second beams to a focusing lens (18). The focusing lens projects the redirected optical energy from the first and second beams on first and second regions of a focal plane, respectively. First and second detector arrays (20, 22) positioned in the focal plane generate electrical signals in response to illumination by the projected optical energy.

Two-color focal plane array sensor arrangement

An optical system (10) for producing dual fields of view simultaneously. The system (10) includes a first optical system (12) for producing a first field of view image and a second optical system (36) for producing a second field of view image where the angular displacement of the second field of view is different from that of the first field of view. A dichroic beamsplitter (22) is disposed in the present invention so as to reflect light from the first optical system (12). The dichroic beamsplitter (22) is also disposed so as to simultaneously transmit light from the second optical system (36). As a result, the reflected light (20) is primarily composed of light of a first wavelength band and the transmitted light is primarily composed of a second wavelength band. The light from the two different fields of view are then directed to a dual filter (32) which passes the first wavelength band in one portion and passes the second wavelength band in another portion. Light passing through the dual filter (32) may then be focused onto a sensor (34) which will then detect the first field of view image on one area and simultaneously detect the second field of view image on another area.

Simultaneous dual field of view sensor

A 'Venetian-blind' assembly of dichroic plates (36) is disposed in front of the entrance aperture (26a) of a Cassegrain-type telescope (26) which constitutes the optical focussing assembly in a tracking system for a guided missile (10) or the like. The plates (36) transmit electromagnetic radiation in a first optical wavelength band such as visible light, and reflect radiation in a second wavelength band such as infrared radiation. The plates (36) are inclined at progressively larger angles relative to the optical axis (22) of the telescope (26) such that the infrared radiation is reflected from a front surface (36a) of one plate (36) and subsequently from a rear surface (36a) of an adjacent plate (36) into the telescope (26) at a predetermined angle to the transmitted visible radiation. The predetermined angle is selected such that the telescope (26) forms separate, laterally displaced optical images (46,50) corresponding to the visible and infrared radiation respectively on separate sections (34a,34b) of a focal plane photodetector array (34). Optical filters (54,52) which pass only the visible and infrared radiation therethrough respectively are disposed in front of the respective sections (34a,34b) of the photodetector array (34) to eleiminate optical crosstalk between the two images (46,50).

Dual-band optoelectronic imaging apparatus including 'venetian blind'

A birefringent prism (36) is disposed in front of the entrance aperture (26a) of a Cassegrain-type telescope (26) which constitutes the optical focussing assembly in a tracking system for a guided missile (10) or the like. The prism (36) refracts first radiation (O) having a first polarization in a first direction, and refracts second radiation (E) having a second polarization which is orthogonal to the first polarization in a second direction which is deviated from the first direction by a predetermined angle .DELTA..phi.. The telescope (26) focusses the first and second radiation (O,E) to form separate, laterally displaced first and second optical images (46,50) on first and second respective sections (34a,34b) of a focal plane photodetector array (34). Polarizing filters (56,58) which pass only the first and second polarizations therethrough are disposed in front of the respective sections (34a,34b) of the photodetector array (34) to eliminate optical crosstalk between the two images (46,50). Optical bandpass filters (54,52) having different wavelength passbands may also be provided in front of the two sections (34a,34b) of the photodetector array (34) such that the two images (46,50) constitute different color images of the scene (16).

Dual-image optoelectronic imaging apparatus including birefringent prism

An automatic responsivity control (ARC) circuit compensates for the nonuniform deviation .DELTA.R in the average responsivity R of a column of photodetectors from a nominal responsivity R.sub.0 which is uniform from column to column. The ARC circuit first establishes a reference level by subtracting two known calibration signals occurring during optical retracing and then multiplies the reference level by each image signal occurring during optical scanning. The resulting product contains undesirable signal components or terms which are algebraic functions of .DELTA.R.sup.2 and other terms which are algebraic functions of .DELTA.R. The terms in .DELTA.R.sup.2 are ignored because .DELTA.R is significantly less than R.sub.0. The terms in .DELTA.R are eliminated by establishing a second reference level, which itself includes terms in .DELTA.R, and then subtracting the foregoing product from the second reference level. If the bias voltages applied to the ARC circuit are adjusted according to a formula discussed in the detailed description, this second subtraction results in a cancellation of all terms in .DELTA.R. The resulting output signal therefore contains only terms in .DELTA.R.sup.2 which are negligible, and thus the output signal is substantially free of distortion due to responsivity deviations.

Automatic responsivity control for a CCD imager

A method and apparatus for generating a digital image representation of a printed circuit board. The board has a substrate of insulating material. A pattern of metallic conductors is disposed on a surface of the insulating material. A beam of light energy scans this surface in a predetermined pattern. The beam has an energy level high enough to induce a detectable fluorescence in the surface of the insulating material. This fluorescence is detected and a binary signal is generated to indicate the presence or absence of fluorescence as the beam scans the surface. The binary signal is synchronized with the scanning of the beam such that a binary image representation of the board's surface is provided.

Growing community of inventors

Agoura Hills, CA, United States of America

Colin G Whitney