Abstract: A method and system for detecting gravitational anomalies comprises measuring surface structures, measuring gravitational field characteristics, and estimating the effect of the surface structures on the gravitational measurements. The estimations are then used to derive a representation of nearby non visible features such as changes in rock density, voids, or oil and gas deposits. The surface structures may be measured by a video camera, with the video sequence being processed to estimate 3D positions of structures relative to the measurement point. Other methods may be used, such as lidar or acoustic techniques as appropriate. The method may be applied above ground and also has efficacy in borehole and sewer surveying applications.

Abstract: A photodetector circuit incorporates an avalanche photodiode (APD) 300 produced by epitaxy on a CMOS substrate 302 with implanted n-well 304 and p-well 306. The n-well 304 has an implanted p+ guard ring 310 delimiting the APD 300. Within the guard ring 310 is an implanted n+ APD layer 312 upon which is deposited an epitaxial p+ APD layer 314, these layers forming the APD 300. The APD may be incorporated in an amplifier circuit 50 providing feedback to maintain constant bias voltage, and may include an SiGe absorption region to provide extended long wavelength response or lower avalanche voltage. Non-avalanche photodiodes may also be used.

Abstract: An imaging system comprises an image detection unit (52) and a filter unit (58). Pixel image signals are passed in parallel from the image detection unit (52) to the filter unit (58). Circuit elements within each pixel (56) generate pixel image signal whose amplitude is proportional to the logarithm of the image intensity at that pixel. The filter unit (58) carries out a spatial filtering operation and outputs the result.

Abstract: A buffer circuit includes a MOSFET source follower (M54) and a floating gate MOSFET (MFG53) connected in series with the phototransistor (PT51) to control current through it at an input circuit node (D53). The source follower (M54) buffers the phototransistor (PT51), having a gate (G54) connected to its emitter (PC51). The floating gate (F53) is programmable with charge to preset the phototransistor current under prearranged illumination conditions to counteract unwanted signal contributions (e.g. fixed pattern noise) or non-optimum circuit characteristics. The floating gate MOSFET (MFG67) may alternatively be connected in series with the source follower output (D65) to control current at an output circuit node. The circuit may be a member of a pixel circuit array and may include programming circuitry (M84, M85) to select it for programming and to isolate it to enable other array members to be programmed.

Abstract: The invention provides a sensor system (800) for generating a sensor signal (Sout) corresponding to a filtered image of a scene. The system (800) incorporates a multielement array (526) and associated processing circuits for providing element signals in response to images projected onto it and a projecting lens assembly (502) for projecting images onto the array (526). The lens assembly (502) projects differently blurred images of the scene onto the array (526) for generating a measurement signal during a measurement phase and a local spatial average correction signal during a calibration phase. A light-diffusing shutter (522) is used for generating the differently blurred images. The system (800) substracts the measurement and correction signals of each element from one another to provide a difference signal and uses this signal to generate the sensor signal (Sout) during the measurement phase.

Abstract: The invention provides a sensor apparatus (200) with compensated signal processing for generating a sensor signal corresponding to a filtered image of a scene. The apparatus (200) incorporates a multielement array (52) for providing at each element (58) first and second signals in response to first and second scene images projected onto it and a lens assembly (204) for projecting the images onto the array (52). Each element (58) is connected to an associated circuit (300). Each circuit (300) performs a subtraction of the first and second signals of its associated element from one another to provide a difference signal and supply this signal for use in generating the sensor signal. Each circuit (300) incorporates a transistor (T17) for injecting charge to compensate at least partially for subtraction accuracy degrading parasitic charge injection occurring within the circuit (300) when the apparatus (200) switches between projecting the first image and the second image onto the array (52).

Abstract: A photodetector circuit incorporates an avalanche photodiode (APD) 300 produced by epitaxy on a CMOS substrate 302 with implanted n-well 304 and p-well 306. The n-well 304 has an implanted p+ guard ring 310 delimiting the APD 300. Within the guard ring 310 is an implanted n+ APD layer 312 upon which is deposited an epitaxial p+ APD layer 314, these layers forming the APD 300. The APD may be incorporated in an amplifier circuit 50 providing feedback to maintain constant bias voltage, and may include an SiGe absorption region to provide extended long wavelength response or lower avalanche voltage. Non-avalanche photodiodes may also be used.