355 results about "Fixed-pattern noise" patented technology

An imaging device of the present invention includes an image capturing unit, a noise obtaining unit, a fixed noise calculating unit, and a noise eliminating unit. The image capturing unit generates image data by photoelectrically converting, pixel by pixel, a subject image formed on an available pixel area of a light-receiving surface. The noise obtaining unit reads a noise output from a partial area of the available pixel area. The fixed noise calculating unit calculates an estimation of fixed pattern noise of the available pixel area based on the noise output read from the partial area. The noise eliminating unit subtracts the fixed pattern noise from the image data.

Elimination of dark fixed pattern noise (DFPN) for tethered CMOS sensor-based digital video cameras is supported by supplying and maintaining a host-based dark image cache. Since the camera is tethered to a host computer system such as a PC, it takes advantage of the storage and processing capabilities of the host to manage the cache. By using a dark image cache for updating of the currently applicable dark image for DFPN cancellation processing, operation of the camera shutter for acquiring dark images is dramatically reduced, thereby using less system resources such as power, and increasing the MTBF of the electromechanical devices such as the camera shutter and associated controls. Dark images are obtained at different integration, gain, and temperature operating characteristics of the camera and stored in the cache. The cached dark images are referenced on the host according to a fixed, predetermined dark column of data in video frames generated by the CMOS sensor image array of the camera. The dark column data represents a portion of the CMOS sensor image array which is permanently and totally shadowed for use during DFPN cancellation processing.

A hand-held fingerprint scanner having local storage of image normalization data is disclosed, as well as a method of manufacturing such a scanner. The image normalization data is representative of fixed pattern noise associated with the image sensor used in the fingerprint scanner. This data may be combined with the raw image data resulting in normalized image data. The image normalization data is stored in non-volatile memory where it can be transmitted to a host processor. Alternatively, the fingerprint scanner may include a normalization processor, allowing transmission of normalized fingerprint images to a host processor. Also disclosed is a fingerprint scanning system having remote fingerprint scanners with local storage of image normalization data.

Methods and systems for correcting fixed pattern noise (FPN) in infrared (IR) imaging cameras. The methods and systems include correcting IR sensor data different strength levels of FPN data and selecting the particular strength level that produces corrected data with the least amount of FPN. The correction may occur over several frames of IR sensor data in order to find an optimal strength level for correction.

A solid state imager includes an arrangement for converting analog pixel values to digital form on an arrayed per-column basis. An N-bit counter supplies an N-bit DAC to produce an analog ramp output providing a ramp signal with a level that varies corresponding to the contents of the counter. Latches or equivalent digital storage elements are each associated with a respective column. A counter bus connects the counter to latch inputs of said latches, and comparators associated the columns gate the latches when the analog ramp equals the pixel value for that column. The contents of the latch elements are transferred sequentially to a video output bus to produce the digital video signal. There can be additionally black-level readout latch elements, for storing a digital value that corresponds to the dark or black video level, and a subtraction element subtracts the black level value from the pixel value to reduce fixed pattern noise. An additional array of buffer latches can be employed.

A method for removing a stationary noise pattern from digital images uses an adaptive noise estimation algorithm to calculate a prediction of the fixed pattern noise and a confidence estimate for the prediction. In one embodiment, a predicted noise value is obtained from the captured image and a predicted image derived from spatial and temporal pixel value prediction techniques. The predicted noise value is used to update a fixed pattern noise estimate only when the confidence estimate for the predicted image is high. In another embodiment, the confidence estimate is used as a weight factor for blending the noise prediction into the noise estimate. In yet another embodiment, the adaptive noise estimation algorithm is applied to a prediction area in the image for calculating scaling parameters which scaling parameters are used to calculate a noise estimate for the entire image based on a reference noise image.

A pixel design for CMOS image sensors that has a high frame rate potential and, therefore, provides motion capture capabilities. The pixel is designed for global electronic shuttering so every pixel is exposed simultaneously to images incident upon the pixel array plane. The present invention has the advantages of: (1) Allowing the accommodation of changes in the pixel output groupings for different monochrome output format or CFA patterns with only changes in metal routing layers; (2) allowing true electronic shuttering to image moving scene with all the pixels having the same capture time windows; and (3) providing a symmetric global shutter gate and transfer gate to minimize pixel related fixed pattern noise. The pixel architecture provides for a CMOS based, active pixel image sensor comprising an array of pixels formed in rows and columns, with each of the pixels containing at least one active circuit element. There are a plurality of output channels formed such that each of the output channels are operatively connected to a subset of pixels wherein each of the pixel have an attribute that is the same. The pixel architecture also provides an output gate region and a shutter gate region that are symmetric about the center of the pixel. By arranging the shutter and transfer gates, a symmetric manner about the center of the pixel, a more efficient transfer of electrons to these gates is provided. A Pixel Output Bus structure allows configurable connections to column-wise signal busses that provide parallel output channels.

A system and method adapted for use with a focal plane array of electromagnetic energy detectors to receive first and second frames of image data from electromagnetic energy received from at least a portion of a scene. The first frame is a focused frame and the second frame is a blurred frame. In a feed-forward path the system compares the first frame to the second frame and provides an error signal in response thereto. In a main path, the system multiplies at least a portion of the second frame of image data with the error signal to provide an noise error corrected output signal. In the preferred embodiment, the error signal is scaled prior to being multiplied by the second frame. A min-mean filter is provided to remove dome shading effects from the frames of image data. In the best mode, the min-mean filter is disposed in the main path and blurred and focused outputs therefrom are weighted, averaged and stored. The weighted, averaged and stored focused frames are compared to the weighted, averaged and stored blurred frames to provide a fixed pattern noise error signal. A temporal noise error signal is identified from the weighted, averaged and stored focused frames. The fixed pattern and temporal noise error signals are fed forward and shunted from a current frame using multiplication or division. Thereafter, a constant mean value may be added to provide the output signal. Pixel replacement is consolidated into a single circuit and positioned prior to the min-mean filter.

A method or a device that reduces fixed pattern noise in an image captured by a digital image device and adjusts the reduction based on the level of FPN, preferably on an area-by-area basis or on a pixel-by-pixel basis.

A method and a system for the compensation of Fixed Pattern Noise (FPN) in digital images have been achieved. The FPN compensation is based on processing done during the production of said images. The fixed pattern noise is here defined as the fixed pattern seen in the individual pixel offsets. The fixed pattern noise is uncorrelated noise but it has a statistical distribution that can be scaled to fit all images. The general idea is to measure the distribution for each individual camera, compress it, and save it in the module. For each image that is then taken with the module the noise pattern can be retrieved and rescaled to fit the image. Covered pixels are employed to normalize the FPN data to the current frame. In order to minimize memory requirements a compression scheme has to be used. A method combining a quantization step with a non-lossy compression is used. The black level is corrected for as part of the operation.

A fixed pattern noise subtraction method in a digital imaging system incorporating a digital image sensor includes: acquiring a reference image of the digital image sensor when the digital image sensor receives no illumination, storing a reference value of an operating parameter associated with the reference image where the reference image is indicative of the fixed pattern noise associated with the digital image sensor, storing a model describing the behavior of the fixed pattern noise as a function of the operating parameter. Then, the method continues with acquiring a first image, measuring a current value of the operating parameter associated with the first image, calculating a noise prediction image by extrapolation of the reference image in accordance with the model and based on the current value and the reference value of the operating parameter, and subtracting the noise prediction image from the first image to generate a final image.

Systems and methods provide scene-based non-uniformity correction for infrared images, in accordance with one or more embodiments. For example in one embodiment, a method of processing infrared images includes storing a template frame comprising a first plurality of pixel data of an infrared image; receiving an input frame comprising a second plurality of pixel data of an infrared image; determining frame-to-frame motion between at least some of the first and second plurality of pixel data; warping the template frame based on the determining of the frame-to-frame motion; comparing the first plurality of pixel data to the second plurality of pixel data to determine irradiance differences based on the determining; propagating pixel offset information for scene based non uniformity correction terms, based on the determining of the frame-to-frame motion, for at least some of the scene based non uniformity correction terms to other ones of the scene based non uniformity correction terms; updating the scene based non uniformity correction terms based on the comparing and the propagating; applying the scene based non uniformity correction terms to the second plurality of pixel data to reduce fixed pattern noise; and providing an output infrared image after the applying.

An image pickup apparatus comprises an image pickup unit including a light receiving pixel area including plural pixels each configured to accumulate photoelectric charge and to output signal and a comparative pixel area configured to output always, for example, dark signal in a state free of photoelectric charge, a first storing unit configured to store FPN component values of the light receiving pixel area, a second storing unit configured to store preliminarily FPN component value of the comparative pixel area, a first correction unit configured to perform predetermined comparison processing between the signal from the comparative pixel area and the FPN component value stored in the second storing unit, and to correct the FPN component values stored in the first storing unit, and a second correction unit configured to correct the signal from the light receiving pixel area by the FPN component values after correction by the first correction unit.

A solid-state imaging device comprises: a plurality of pixels including a light-sensitive portion (2) for photoelectrically converting incident light, a transfer gate (10) for transferring a charge stored in the light-sensitive portion, a resettable detection capacitor (18) for storing the charge transferred from the transfer gate, and a selection switch (26) for outputting a charge of the detection capacitor according to a selection signal RWn; a charge amplifier (41) for converting the detection capacitor charge, which is outputted from the pixels, to a voltage; and a correlated double sampling circuit (86) for obtaining a voltage difference between a reset level and a detected level converted by the charge amplifier. According to the above device, a thermal noise is eliminated due to the correlated double sampling circuit. Further, a fixed pattern noise is not generated due to the pixel circuit structure.

Improving fingerprint image measurement despite damage to the stratum corneum. Determining whether a fingerprint image is adequate for matching with a database. If not, re-measure those image portions that are inadequate (overexposed or underexposed), such re-measuring a minimal selection of image portions. An amount of time or power to re-measure is minimized. Improving fingerprint image data collection despite fixed pattern noise like saturated bars in blocks of picture elements. Determining a histogram of grayscale values, removing fixed pattern noise, and expanding real histogram values to obtain more bits of precision.

A method and system for maintaining uniformity in a FLIR display. During a one-time initialization procedure, a plurality of dynamic ranges are defined by covering a specific range of bucket fill levels when in a certain gain. To cover all dynamic ranges possible, a plurality of pairs of responsivity equalization (RE) calibrations (each pair producing a RE set of pixel gain corrections) are also accomplished in the same one time initialization period. A plurality of corresponding level equalization (LE) calibrations (each using the appropriate calibrated RE set and producing a LE set of pixel level corrections) for each anticipated dynamic range are made at every power-up initialization. Each of the calibrations is done with respect to a thermal reference source to produce a uniform scene at the desired bucket fill level. An algorithm is employed which forces the two bucket fill points defined during the responsivity calibration to span as far as possible the dynamic range and forces the level equalization bucket fill point to fall within the two bucket fill points of the responsivity calibration. Then, during an operational time period, the scene and optics temperatures are monitored, and if the average bucket fill value exceeds the bucket fill range of the present dynamic range, the presently selected dynamic range is changed to a second dynamic range (gain is changed along with the RE set and LE set). The dynamic ranges are designed to overlap so that a hysteresis effect is achieved. The pre-calibrations and automatic dynamic range switching prevent saturation and create the best uniformity (lowest fix pattern noise) possible while allowing for continuous operation of the FLIR system, thus eliminating the interruption caused by the prior art touch-up calibration procedure.

An imager having a switching circuit that couples pixel columns to different sample and hold circuits to reduce the noticeability of column-wise fixed pattern noise. A controller randomly couples a pixel column to a sample and hold circuit, therefore fixed pattern noise emanating from a particular sample and hold circuit is not always associated with a single pixel column. Therefore the visual perception of fixed pattern noise associated with a particular sample and hold circuit is reduced.

There is described a pixel value adjustment method and apparatus. In one embodiment, pixel values can be adjusted by execution of an algorithm for adjusting pixel values. In one embodiment, an apparatus capable of executing an algorithm for adjusting pixel values is capable of operating in a decoding operating application. In one embodiment, an apparatus capable of executing an algorithm for adjusting pixel values is capable of operating in a video display operating application.

An on-chip FPN calibration method and circuits scheme applying a reference voltage signal to an array of calibration pixels coupled to a sensor matrix. Two data values are read from each bit line and used to calculate an offset and a gain error for a pixel column. A reference offset and a reference gain error value are then generated by computing the average offset and the average gain error from the collected offset and gain error values of each bit line. Calibration data for each bit line then comprises an offset difference and a gain error difference, the offset difference comprising the difference between the offset value for that bit line and the reference offset, and the gain error difference comprising the gain error difference between the gain error for that bit line and the reference gain error. The calibration data for each bit line is then stored in on-chip volatile memory and is used later under normal operation to compensate for the FPN effect.

A solid-state image pickup apparatus and an image pickup method are disclosed which can detect and correct fixed pattern noise efficiently and accurately. Pickup image signals produced by reading out signals in parallel from a pixel sensor section are subject to an analog gain process, an A / D conversion process and a digital gain process. Within a period within which the pickup image signals which are based on a fixed value are inputted within a one-frame period, a reference signal average is produced from the signals. Sum values of difference values of the signals from the reference signal average are stored. Within a period within which the pickup image signals from valid pixels are inputted within the one-frame period, fixed pattern noise is removed from the pickup image signals using division averages obtained by dividing the stored sum values.

A configurable current source for imager readout system that can be operated as a simple-current-source or as a cascode-current-source. The configurable current source can be operated in a simple-current-source mode during circumstances when a low power supply voltage or large output signal swing is needed to output a pixel signal. The configurable current source can also be operated in a cascode-current-source mode for reduced nonlinearity and column-wise fixed pattern noise when power from a power supply is not a limitation. The configurable current source provides design flexibility and pixel optimization for imager development.

An apparatus and method for fixed pattern noise (FPN) correction in an image sensor utilizes at least one row of test pixels. An external voltage is applied to each pixel circuit in the at least one row. Thus, the output of the test pixels does not depend on the photo or dark current signals. The applied voltage is used to determine a column offset error for each column in the image sensor.

A solid state imager converts analog pixel values to digital form on an arrayed per-column basis. An N-bit counter supplies an N-bit DAC to produce an analog ramp output with a level that varies corresponding to the contents of the counter. A ripple counter or equivalent is associated with each respective column. A clock supplies clock signals to the counter elements. A comparator in each column gates the counter element when the analog ramp equals the pixel value for that column. The contents of the counters are transferred sequentially to a video output bus to produce the digital video signal. Additional black-level readout counter elements can create and store a digital value that corresponds to a dark or black video level. A subtraction element subtracts the black level value from the pixel value to reduce fixed pattern noise. An additional array of buffer counter / latches can be employed. The ripple counters can be configured as counters to capture the digital video level, and then as shift registers to clock out the video levels to an output bus. The clock pulses for the DAC counter and for the ripple counters can be at the same or different rates.

A system and method adapted for use with a focal plane array of electromagnetic energy detectors to receive first and second frames of image data from electromagnetic energy received from at least a portion of a scene. The first frame is a focused frame and the second frame is a blurred frame. In a feed-forward path the system compares the first frame to the second frame and provides an error signal in response thereto. In a main path, the system multiplies at least a portion of the second frame of image data with the error signal to provide a noise error corrected output signal. In the preferred embodiment, a wavelet filter is used to remove dome shading effects from the frames of image data. In the best mode, the wavelet filter is disposed in the main path and blurred and focused outputs therefrom are weighted, averaged and stored. Coefficients from the weighted, averaged and stored focused frames are compared to coefficients from the weighted, averaged and stored blurred frames to provide a fixed pattern noise error signal. A temporal noise error signal is identified from the weighted, averaged and stored focused frames. The fixed pattern noise error signal and the temporal noise error signals are sparse processed and shunted from a current frame. Thereafter, a constant mean value may be added to provide the output signal. Pixel replacement can be consolidated into a single circuit and positioned prior to the wavelet filter.

PCT No. PCT / GB96 / 01805 Sec. 371 Date Jan. 9, 1998 Sec. 102(e) Date Jan. 9, 1998 PCT Filed Jul. 29, 1996 PCT Pub. No. WO97 / 05742 PCT Pub. Date Feb. 13, 1997A thermal sensing system (10) including an array of photon detectors (14) produces a detector-dependent response to irradiation. Variations in individual detector characteristics produce a fixed pattern noise which degrades an image or other response. A switchable mirror (M1) may at one position (Pcal) direct infrared radiation from a light emitting diode (20) onto the detector array (14). The diode (20) is both a negative and positive luminescent emitter, the flux emitted is current controlled to be equivalent to black body radiation at a range of temperatures both colder and hotter than ambient. Calibration relationships comprising transfer functions relating incident intensity to signal response are derived for each detector. Alternatively the mirror (M1) may be at an observation position (Pobs) and infrared radiation from a remote scene reaches the detector array (14). Resulting detector signals are converted into corrected fluxes using individual calibration relationships previously derived and an image or response with reduced fixed pattern noise is obtained.

The present invention is directed to a method and apparatus for reading out signals from a MOS image sensor. The invention allows for a relatively high fixed pattern noise canceling rate, even in low light environments. The invention includes a digital processing structure for processing the signals from a pixel array. The pixel array includes a reference row that is formed by being covered by a light shield or black layer to cover the pixels of the reference row from light. The signals from the reference row are converted to digital values and stored in fixed pattern noise storage circuitry. Then, as each of the remaining rows of the pixel array are read out, they are converted to digital values and the digital reference row signals are subtracted therefrom to produce data image signals that are relatively free of fixed pattern noise. Thus, the fixed pattern noise canceling rate is made to depend on the precision of an analog-to-digital converter, rather than the process variations of an analog subtraction circuit.

A non-traditional, non-uniformity compensation processor. In the illustrative embodiment, the feedforward adaptive non-uniformity compensation processor includes a multiplier which receives a video image and generates a compensated video image by multiplying the video signal by one of a noise reducing constant or one. The inventive processor further includes a shunting multiplication processor which supplies a selected one of the noise reducing constant or one to the multiplier in response to the presence of one of fixed pattern noise (FPN) and temporal noise (TN) in adjacent frames of the video image. In an illustrative embodiment, the inventive system cones the output of an FPA to generate a coned output signal. The system isolates the FPN in the coned output signal and feedforward processes the coned output signal on a pixel-by-pixel basis to generate a FPN-reduced output signal. In an exemplary embodiment, the feedforward processing step includes the step of multiplying the coned output signal by a predetermined value which is substantially smaller, i.e., approximately zero, than the coned output signal.