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Showing papers on "Image sensor published in 1994"


Journal ArticleDOI
TL;DR: In this paper, a 2.0 /spl mu/m double-poly, double-metal foundry CMOS active pixel image sensor is reported, which uses TTL compatible voltages, low noise and large dynamic range, and is useful in machine vision and smart sensor applications.
Abstract: A new CMOS active pixel image sensor is reported. The sensor uses a 2.0 /spl mu/m double-poly, double-metal foundry CMOS process and is realized as a 128/spl times/128 array of 40 /spl mu/m/spl times/40 /spl mu/m pixels. The sensor features TTL compatible voltages, low noise and large dynamic range, and will be useful in machine vision and smart sensor applications. >

302 citations


Patent
15 Feb 1994
TL;DR: In this paper, an image sensor formed using a CMOS process is described, which includes a pixel array core of phototransistors whose conductivities are related to the magnitude of light impinging upon the photottransistors.
Abstract: An image sensor formed using a CMOS process is described herein which includes a pixel array core of phototransistors whose conductivities are related to the magnitude of light impinging upon the phototransistors. The analog signals generated by the phototransistors are converted to a serial bit stream by an A/D converter connected at the output of each phototransistor and formed in the immediate area of each phototransistor within the array core. Thus, a separate digital stream for each pixel element is output from the array core, and parasitic effects and distortion are minimized. In one embodiment, a filter circuit is connected to an output of the array core for converting the individual digital streams from each pixel element to multi-bit values corresponding to the intensity of light impinging on the phototransistor.

299 citations


Proceedings ArticleDOI
16 Feb 1994
TL;DR: In this paper, an area image sensor with a one-bit sigma-delta modulator is presented. But the analog image data is immediately converted to digital at each pixel using a one bit sigmoid modulator, and the data-conversion circuitry is simple and insensitive to process variations.
Abstract: Charge-coupled devices (CCD) are at present the most widely used technology for implementing area image sensors. However, they suffer from low yields, consume too much power, and are plagued with SNR limitations due to the shifting and detection of analog charge packets, and the fact that data is communicated off chip in analog form. This paper describes an area image sensor that can potentially circumvent the limitations of CCDs and their alternatives. It uses a standard CMOS process and can therefore be manufactured with high yield. Digital circuitry for control and signal processing can be integrated with the sensor. Moreover, CMOS technology advances such as scaling and extra layers of metal can be used to improve pixel density and sensor performance. The analog image data is immediately converted to digital at each pixel using a one-bit sigma-delta modulator. The use of sigma-delta modulation allows the data-conversion circuitry to be simple and insensitive to process variations. A global shutter provides variable light input attenuation to achieve wide dynamic range. Data is communicated off chip in a digital form, eliminating the SNR degradation of analog data communication. To demonstrate the viability of the approach, an area image sensor chip is fabricated in a 1.2 /spl mu/m CMOS technology. The device consists of an array of 64x64 pixel blocks, a clock driver, a 6:64 row address decoder, 64 latched sense amplifiers, and 16 4:1 column multiplexers. The chip also contains data compression circuitry. >

175 citations


Journal ArticleDOI
TL;DR: The results show that the selenium-based detector has a wide dynamic range and a significantly better DQE than screen-film and storage phosphor systems for spatial frequencies below the Nyquist limit (2.7 lp/mm), and the detectability of small, low-contrast details is considerably improved.
Abstract: A digital chest radiographysystem has been developed, with a detector based on the photoelectric properties of amorphous selenium. The selenium layer is deposited on a cylindrical aluminium drum, large enough to cover the full field of view for chest imaging. The electrostatic charge image which is formed on the selenium surface after x‐ray exposure is read out by electrometer probes using fast drum rotation. For a physical evaluation of the attainable image quality, the characteristic curve, the modulation transfer function, and the noise spectra were measured. From these measurements, the signal‐to‐noise properties of the detector in terms of detective quantum efficiency (DQE) and noise equivalent quanta (NEQ) were derived. The results show that the selenium‐based detector has a wide dynamic range and a significantly better DQE than screen‐film and storage phosphor systems for spatial frequencies below the Nyquist limit (2.7 lp/mm). As a consequence, the detectability of small, low‐contrast details is considerably improved.

139 citations


Patent
22 Nov 1994
TL;DR: A sequential video imaging system as mentioned in this paper uses a video sensor having full frame whereby image data is moved from sensor image elements to a video amplifier, and the object being viewed is sequentially illuminated with colored light sources to produce RGB or luminance and chrominance video signals.
Abstract: A sequential video imaging system uses a video sensor (15) having full frame whereby image data is moved from sensor image elements to a video amplifier (16). The object being viewed is sequentially illuminated with colored light sources (11-13) to produce RGB or luminance and chrominance video signals. A digital signal processor (35) includes data buffering and summing circuits.

139 citations


Patent
30 Dec 1994
TL;DR: In this paper, a progressive scan image sensor with a fast dump structure is used to focus the lens of an electronic still camera using the average contrast of a central region of the image to determine how well the image is focused.
Abstract: A technique for automatically focusing the lens of an electronic still camera employs a progressive scan image sensor 20 with a fast dump structure 62. The image sensor 20 itself is operated first in a "fast flush " mode to focus a lens 22, and then in a normal readout mode to obtain the final still image. To focus the lens 22, an image is integrated on the sensor 20. The average contrast of a central region 66 of the image is used to determine how well the image is focused. The portion of the image surrounding a central focusing area 66 is rapidly read out and discarded, using "fast flush" clocking where the vertical and horizontal registers are continuously clocked and lines of image charge are dumped to the substrate through the fast dump structure 62. In the central focusing area 66, a pattern of lines are eliminated through the fast dump structure 62, and the intervening lines are transferred out to generate a focus adjustment signal. The process is repeated numerous times as the lens focus is adjusted until the maximum average contrast is obtained. At this point, the entire sensor is cleared using "fast flush" clocking, and the final image is then captured and read out.

132 citations


Journal ArticleDOI
TL;DR: The results show that scattered radiation can reduce contrast significantly in portal films while deteriorating image quality only moderately in on-line systems, and the reduction in DSNR depends on the light collection efficiency and the noise characteristics of the TV camera.
Abstract: The physical characteristics of x rays scattered by the patient and reaching the imaging detector, as well as their effect on verification (portal) image quality, were investigated for megavoltage (0.1–20 MeV) x‐ray beams. Monte Carlo calculations and experimental measurements were used to characterize how the scatter and primary fluences at the detector plane were influenced by scattering geometry and the energy spectrum of the incident beam. The calculated scatter fluences were differentiated according to photon energy and scattering process. Scatter fractions were measured on a medical linear accelerator (Clinac 2100c, 6 MV) for a typical imaging geometry using an ionization chamber and a silicon diode. After correction for the energy dependence of the chamber and diode, the scatter fractions generated by the Monte Carlo simulations were found to be in excellent agreement with the measured results. In order to estimate the effect of scatter on image quality, the scatter and primary signals (i.e., energy deposited) produced in five different types of portal imaging detectors (lead plate/film, storage phosphor alone, lead plate/storage phosphor, Compton recoil‐electron detector, and a copper plate/Gd2O2S phosphor) were calculated. The results show that, for a specified geometry, the scatter fraction can vary by an order of magnitude, depending on the sensitivity of the imaging detector to low‐energy (<1 MeV) scattered radiation. For a common portal imaging detector (copper plate/Gd2O2S phosphor), the scattered radiation (i) reduced contrast by much as 50% for a fixed display‐contrast system, and (ii) decreased the differential‐signal‐to‐noise ratio (DSNR) by 10%–20% for a quantum‐noise‐limited portal imagingsystem. For currently available TV‐camera‐based portal imagingsystems, which have variable display contrast, the reduction in DSNR depends on the light collection efficiency and the noise characteristics of the TV camera. Overall, these results show that scattered radiation can reduce contrast significantly in portal films while deteriorating image quality only moderately in on‐line systems.

127 citations


Patent
21 Nov 1994
TL;DR: A sequential video imaging system uses a video sensor (15) having interline architecture whereby image data is moved from sensor elements to adjacent interlined storage elements as mentioned in this paper, where the object being viewed is sequentially illuminated with colored light sources (11-13) to produce luminance and chrominance video signals.
Abstract: A sequential video imaging system uses a video sensor (15) having interline architecture whereby image data is moved from sensor elements to adjacent interlined storage elements. The object being viewed is sequentially illuminated with colored light sources (11-13) to produce luminance and chrominance video signals. Binning of image data corresponding to low level color signals is carried out in the sensor (15). A digital signal processor (35) includes data buffering and averaging circuits whereby the camera head and base unit can be operated asynchronously.

118 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a taxonomy that includes 15 techniques for measuring the image center of a precision automated zoom lens, and several techniques are applied to a precision automatic zoom lens and experimental results are shown.
Abstract: To model the way that cameras project the three-dimensional world into a two-dimensional image we need to know the camera’s image center. First-order models of lens behavior, such as the pinhole-camera model and the thin-lens model, suggest that the image center is a single, fixed, and intrinsic parameter of the lens. On closer inspection, however, we find that there are many possible definitions for image center. Most image centers do not have the same coordinates and, moreover, move as lens parameters are changed. We present a taxonomy that includes 15 techniques for measuring image center. Several techniques are applied to a precision automated zoom lens, and experimental results are shown.

118 citations


Journal ArticleDOI
TL;DR: Research is described on two imaging range sensors that use defocus to estimate range and one technique is completely passive and provides dense range measurements in textured areas with an rms error of 2.5%.
Abstract: We describe research on two imaging range sensors that use defocus to estimate range. One technique is completely passive and provides dense range measurements in textured areas with an rms error of 2.5%. This method can be useful when stereo is unreliable because of correspondence errors or when imaging geometry prevents the use of multiple viewpoints (e.g., microscopy). The second technique uses structured light and provides dense range measurements with an rms error of 0.5%. This method can be useful when imaging geometry prevents the use of multiple viewpoints and for acquiring range imagery of rapidly moving objects, as the structured light can be delivered in a single stroboscopic flash.

110 citations


Proceedings ArticleDOI
01 May 1994
TL;DR: An investigation of various designs for the pixel, including photogate devices of various geometries and photodiode devices, has been performed and results regarding on-chip suppression of fixed pattern noise are presented.
Abstract: Recent research results regarding the investigation of CMOS active pixel image sensors (APS) are reported. An investigation of various designs for the pixel, including photogate devices of various geometries and photodiode devices, has been performed. Optoelectronic performance including intrapixel photoresponse maps taken using a focused laser scanning apparatus are presented. Several imaging arrays have also been investigated. A 128 X 128 image sensor has been fabricated and characterized. Both p-well and n-well implementations have been explored. The demonstrated arrays use 2 micrometers CMOS design rules and have a 40 X 40 micrometers pixel pitch. Typical design fill-factor is 26%. Output sensitivity is 3.7 (mu) V/e- for the p-well devices and 6.5 (mu) V/e- for the n-well devices. Read noise is less than 40 e- rms for the baseline designs. Dynamic range has been measured to be over 71 dB using a 5 V supply voltage. The arrays are random access with TTL control signals. Results regarding on-chip suppression of fixed pattern noise also are presented.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
TL;DR: A phase-diversity wave-front sensor has been developed and tested at the Lockheed Palo Alto Research Labs (LPARL), which consists of two CCD-array focal planes that record the best-focus image of an adaptive imaging system and an image that is defocused.
Abstract: A phase-diversity wave-front sensor has been developed and tested at the Lockheed Palo Alto Research Labs (LPARL). The sensor consists of two CCD-array focal planes that record the best-focus image of an adaptive imaging system and an image that is defocused. This information is used to generate an object-independent function that is the input to a LPARL-developed neural network algorithm known as the General Regression Neural Network (GRNN). The GRNN algorithm calculates the wave-front errors that are present in the adaptive optics system. A control algorithm uses the calculated values to correct the errors in the optical system. Simulation studies and closed-loop experimental results are presented.

Journal ArticleDOI
TL;DR: In this article, a detailed analysis of the characteristics, regularities, and relationships of the centroiding errors of image spots caused by discrete and limited sampling, photon noise, and readout noise of the detector in a Hartmann-Shack wavefront sensor is presented.
Abstract: A detailed analysis of the characteristics, regularities, and relationships of the centroiding errors of image spots caused by discrete and limited sampling, photon noise, and readout noise of the detector in a Hartmann-Shack wavefront sensor, wherein an image intensified charge-coupled device used as a photon detector is presented. The theoretical analysis and experimental results herein prove useful for optimum design and application of the sensor.

Journal ArticleDOI
TL;DR: In this article, a two-dimensional (2D) pH-imaging sensor was constructed that enables us to observe th H+ distribution produced by living cells, which is similar to that of the light-addressable potentiometric sensor.
Abstract: We have constructed a two-dimensional (2-D) pH-imaging sensor that enables us to observe th H+ distribution produced by living cells. The pH-sensing principle is similar to that of thelight-addressable potentiometric sensor. The electrolyte-insulator-semiconductor (EIS) structure (electrolyteSi3N4SiO2Si) is illuminated by a focused (∼1 μm) and modulated (1–10 kHz) He—Ne laser bean from the backside of the semiconductor, and the a.c. photocurrent flowing through the EIS structure is measured. By scanning the laser beam, 2-D pH images can be obtained. By using this sensor, pH distributions of colonies of yeast (Saccharomyces cerevisiae) have been observed. The spatial resolution of this sensor could be improved by thinning the Si wafer.

Journal ArticleDOI
TL;DR: An energy transport model incorporating measured breast tissue attenuation coefficients and published exposure-to-dose conversion values was developed to describe the image acquisition process and can be used to compare and improve upon novel detector designs.
Abstract: It has been proposed that breast cancerdetection can be improved through the use of digital mammography. It is hypothesized that the choice of proper shape of the x‐ray spectrum incident upon the breast can yield an improved image signal‐to‐noise ratio (SNR) for a given dose. To test this hypothesis, an energy transport model incorporating measured breast tissue attenuation coefficients and published exposure‐to‐dose conversion values was developed to describe the image acquisition process. The choice of applied kilovoltage and filter for Mo and W target x‐ray sources has been optimized with respect to SNR and absorbed dose for detectors based on a Gd2O2S scintillating screen under the conditions of perfect coupling of light between the screen and a solid state photodetector. For the W spectra, the optimum filter–kVp combinations could provide 41%, 13%, and 42% improvements in SNR for 2‐cm, 6‐cm and 8‐cm breasts, respectively, over the conventional Mo filtration, for a practical imaging time of 1.0 s. W and Mospectra produce similar SNR values for a given filter thickness except for the 4‐cm breast. Given the limitations of current technology, however, the W spectra produce the optimum SNRs in a shorter imaging time for breast thicknesses greater than and less than 4 cm. The maximum SNR for imaging both infiltrating ductal carcinoma and calcifications is provided by the same filter–kVp combination, allowing optimization based on breast thickness and composition only. The model can now be used to compare and improve upon novel detector designs.

Patent
28 Feb 1994
TL;DR: In this article, an electronic imaging system is provided that records both motion and still video images at a standard thirty frame per second (FPS) rate in a motion mode of operation.
Abstract: An electronic imaging system is provided that records both motion and still video images. In a motion mode of operation, the electronic imaging system records NTSC resolution images at a standard thirty frame per second rate. In a still mode of operation, the electronic imaging system records megapixel resolution still images at a much lower frame rate. The electronic imaging system utilizes an electronic image sensor that incorporates column selective "charge clearing" structures and column selective "charge parking" structures. The charge clearing structures are used to selectively discard the signal charge from certain color pixels. The charge parking structures are used to sum the charge from multiple vertical pixels. The architecture of the electronic image sensor also allows different image aspect ratios to be provided for the motion and still modes described above.

Patent
03 Oct 1994
TL;DR: In this article, a peripheral IC for a solid state imaging device is mounted on an island 7 of a lead frame and thereafter covered and sealed by a molding resin, thus forming a premolded package 2.
Abstract: A peripheral IC 6 for a solid state imaging device is mounted on an island 7 of a lead frame and thereafter covered and sealed by a molding resin, thus forming a premolded package 2. Subsequently, a solid state image sensor 1 is mounted on the island 7 on one side thereof facing an opening. Thereafter, for protection of the solid state image sensor 1, a transparent lid 11 is attached to the premolded package 2 by adhesive. As a result, packaging area can be reduced in mounting the solid state image sensor on a packaging substrate, allowing video equipment such as video cameras to be miniaturized.

Patent
15 Apr 1994
TL;DR: In this paper, a gas visualizing apparatus includes an image sensor for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory A, a laser source for emitting a detection infrared beam in two-dimensional form toward the area of interest, a CRT for displaying information relating to gas leakage as a 2D visible image corresponding to the region of interest (ROI).
Abstract: A gas visualizing apparatus includes an image sensor for detecting infrared light radiated or reflected from a background of a gas leak monitoring territory A, a laser source for emitting a detection infrared beam in two-dimensional form toward the gas leak monitoring territory A, the detection infrared beam having a wavelength absorbable by a gas "g" to be detected and a CRT for displaying information relating to gas leakage as a two-dimensional visible image corresponding to the gas leak monitoring territory A. The laser source includes a beam expander for converging or diverging the detection infrared beam to vary an area of the gas leak monitoring territory A. The image sensor includes a transmission and width varying device for setting the infrared light entering the image sensor to a band substantially centering on the wavelength of the detection infrared beam, and varying a width of the band, to realize an excellent visible image.

Patent
Ichiro Fujieda1, Yuzo Ono1, Seijin Sugama1
11 May 1994
TL;DR: In this article, a two-dimensional image sensor with openings 28 through which light can pass is formed on a transparent substrate and combined with a planar light source 11 and an optical element 13 which defines optical paths.
Abstract: A two-dimensional image sensor 12 having openings 28 through which light can pass is formed on a transparent substrate 21 and combined with a planar light source 11 and an optical element 13 which defines optical paths. The optical element 13 is formed by combining one of a diffraction grating, a microlens and a specular surface of V-shaped grooves with a collected fiber member formed from bundled optical fibers having light shielding side faces so as to allow the transfer of an image. The profiles of these components are determined so that light may be focused upon a finger contacting area on the center line between the openings 28 and photo-sensitive elements 24 of the sensor 12.

Patent
13 Sep 1994
TL;DR: In this article, a timing logic system which includes a generic television-standard timing generator selectably provides precisely timed horizontal and vertical control signals for controlling the operation of a high-resolution charge coupled device (CCD) image sensor of the type having two line pixel registers in a high resolution mode of picture imaging.
Abstract: A timing logic system which includes a generic television-standard timing generator selectably provides precisely timed horizontal and vertical control signals for controlling the operation of a high resolution charge coupled device (CCD) image sensor of the type having two line pixel registers in a high resolution mode of picture imaging. Alternatively, the timing logic system selectably provides precisely timed horizontal and vertical control signals, and a precisely timed display field control signal applied to a switch mechanism, for controlling the operation of the high resolution CCD image sensor in a television resolution mode of picture imaging in accordance with a television standard, for example, the NTSC standard. The timing logic system also provides sync and control signals to a television-standard display in the television mode of operation. In both the high resolution mode and the television mode of operation, the timing logic system provides the respective horizontal and vertical control signals to the CCD image sensor so that both line pixel registers are operative.

Proceedings ArticleDOI
01 May 1994
TL;DR: In this paper, the limits of the signal/noise ratio in large area x-ray image sensor with digital readout and full dynamic performance were evaluated in 2D thin-film amorphous silicon arrays.
Abstract: The dream of an all-solid state large area x-ray image sensor with digital readout and full dynamic performance will most probably find a first realization in 2D thin-film amorphous silicon arrays. In this paper we address in particular the evaluation of the limits of the signal/noise ratio in this concept. Using small prototype detectors measurements of MTF and noise power spectra have been made as a function of x-ray dose. The results are given in terms of the detective quantum efficiency as a function of dose and spatial frequency. We further present an analysis of the different noise sources and their dependence on the detector parameters, and we provide estimates on the maximum signals that may be achieved per unit dose. The intrinsic lag of the amorphous silicon photodiodes causes a second problem area with this type of x-ray detectors. Especially in radiography/fluoroscopy mixed applications, memory effects may not be negligible.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Patent
22 Nov 1994
TL;DR: In this article, a portable hand-held reader unit for reading two-dimensional information and generating an image therefrom wherein an optical axis of the reader is oriented obliquely to the surface containing the coded information.
Abstract: A portable hand-held reader unit for reading two-dimensional information and generating an image therefrom wherein an optical axis of the reader is oriented obliquely to the surface containing the coded information. The reader includes a sensing system designed such that the rectilinear dimension of the generated image corresponding to an axis of the coded information undergoing the most distortion from oblique reading is magnified, by the lens system or the resolution configuration of the image sensor, to a greater extent than that of the rectilinear dimension undergoing the least distortion from oblique reading. Alternatively, the sensor is oriented relative to the optical axis such that the received image does not exhibit the distortion which may result from oblique reading. The coded information may contain height-to-width ratio of the coded information such that the generated image can be automatically corrected for distortion from oblique reading. Ranging marker beams may be used in conjunction with the obliqueness correcting embodiments to align the reader with the coded information.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the spatial resolution of a laser-scanning semiconductor-based pH-imaging sensor both experimentally and theoretically, and predicted the optimal choice of parameters of Si substrate (thickness, doping, etc.) for the pH imaging sensor.
Abstract: We investigated the spatial resolution of a laser-scanning semiconductor-based pH-imaging sensor both experimentally and theoretically. A spatial resolution better than 100 µ m was obtained by thinning the Si substrate to 100 µ m. The simulation results on the spatial resolution based on a carrier diffusion model agreed well with those obtained by experiment. From the simulation results, we also predicted the optimal choice of parameters of Si substrate (thickness, doping, etc.) for the pH-imaging sensor.

Journal ArticleDOI
TL;DR: This work attacks the image-deconvolution problem in a more realistic formulation than that used by Berenstein and explicitly takes into account image sensor noise and the necessity for adaptive restoration with estimation of all required signal and noise parameters directly from the observed noisy signals.
Abstract: Deconvolution of images of the same object from multiple sensors with different point spread functions as suggested by Berenstein [Proc. IEEE 78, 723 (1990); Stochastic and Neural Methods in Signal Processing, Image Processing, and Computer Vision, S. Chen, ed., Proc. Soc. Photo-Opt. Instrum. Eng. 1569, 35 (1991)], opens new opportunities in solving the image-deconvolution problem, which has challenged researchers for years. We attack this problem in a more realistic formulation than that used by Berenstein; it explicitly takes into account image sensor noise and the necessity for adaptive restoration with estimation of all required signal and noise parameters directly from the observed noisy signals. We show that arbitrary restoration accuracy can be achieved by the appropriate choice of the number of sensor channels and the signal-to-noise ratio in each channel. The results are then extended to the practically important situation when true images in different sensor channels are not identical.

Patent
24 Oct 1994
TL;DR: In this paper, the grey level transformation rule is stored in a look-up table, which contains at least two different laws applying to distinct groups of pixels, and pixel selection is performed by the microcontroller.
Abstract: The method involves using a camera (20) with a matrix array of e.g. 256 x 256 CCD image sensors (21) which deliver an analogue video signal (23) contg. pixel grey levels for digitisation (24). A microcontroller (26) operates on the image stored in memory (54) using a data bus (55) for the grey level signals and an address bus (56) for the pixel row and column numbers (43, 42). A grey level transformation rule is stored in a look-up table (52) which contains at least two different laws applying to distinct groups of pixels. Selection (50) is performed by the microcontroller.

Journal ArticleDOI
TL;DR: The input/output characteristics of a matrix liquid ion-chamber electronic portal imaging device (EPID) are investigated to elucidate the imaging properties of EPIDs and results indicate that the output pixel value is not a linear function of the incident radiation intensity.
Abstract: The input/output characteristics of a matrix liquid ion-chamber electronic portal imaging device (EPID) are investigated to elucidate the imaging properties of EPIDs. The radiation input to the detector, represented by dose rate, and the pixel value output from the device are related by a characteristic curve. Various incident radiation intensities are obtained by changing the source-to-detector distance (SDD). For each incident radiation intensity, an electronic portal image is obtained using a field size of 5 x 5 cm2. The output pixel value of the EPID is represented by the average pixel value of a region of interest of 9 x 9 pixels centered at a selected point. The effects of various accelerator settings, such as the repetition-rate setting and photon energy, gantry angle, field size, SDD, and acquisition mode of the EPID on characteristic curves are investigated at the central axis. The off-axis response of the detector is also examined. The derivative of the pixel value with respect to the input dose rate is used to analyze the detector contrast. Results indicate that the output pixel value is not a linear function of the incident radiation intensity. The detector contrast is comparable between photon energies of 10 and 6 MV and increases at low dose rates. The response of the imaging device varies substantially with acquisition mode, but is less sensitive to the SDD used for calibration. Characteristic curves are consistent for different gantry angles at the central axis and with the off-axis locations when the gantry angle is used for imaging and calibration, but vary with off-axis locations when the gantry angle is not at the calibration direction. Characteristic curves are also found to vary with different field sizes, but are similar in shape.

Patent
08 Dec 1994
TL;DR: In this paper, a wide-angle lens produces a distorted wideangle optical image, and an imaging sensor, having a surface in optical communication with the wideangle lens, converts the wide-angles optical image into a corresponding output signal.
Abstract: A wide-angle lens produces a distorted wide-angle optical image. An imaging sensor, having a surface in optical communication with the wide-angle lens, converts the wide-angle optical image into a corresponding output signal. The imaging sensor includes a plurality of imaging elements. The plurality of imaging elements have a distribution on the surface of the sensor that is representable by a nonlinear function, wherein the distribution of the imaging elements corrects the distortion in the wide-angle image.

Patent
25 Jan 1994
TL;DR: In this paper, a video camera for real time simulation of the visual appearance of motion picture film that has been transferred or converted to a video signal comprising analog signal input conditioning circuitry, analog to digital convertor, timing and control circuitry, an address multiplexer and memory control, a digital adder, and a digital to analog convertor.
Abstract: Video output emulating the broadcast look of motion picture film is created by the present invention. A video camera for real time simulation of the visual appearance of motion picture film that has been transferred or converted to a video signal comprising analog signal input conditioning circuitry, an analog to digital convertor, timing and control circuitry, an address multiplexer and memory control, a digital adder, and a digital to analog convertor. A method for creating the look of broadcast motion picture film comprising the steps of increasing the scan rate of CCD image sensors to output non-interlaced video images, converting said video images from analog to digital form, writing said video images to memory, adding a selective, adjustable amount of two dimensional, electronic artifacts to simulate film grain, reading said video images from said memory banks to a video output data bus at predetermined rates, and converting said video images from digital to analog form for recording or broadcast.

Proceedings ArticleDOI
29 Jul 1994
TL;DR: In this paper, the uncertainties in determining the percent of polarization P and angle of the plane of polarization (phi) using the Physics Innovations sensor are made explicit by analytical expressions and by computer simulations of the images.
Abstract: In order to recognize 3-D objects, conventional methods in robot vision perform shape extraction by sensing the intensity of light reflected by objects. A fundamental problem associated with sensing the intensity of reflected light is that intensity gives one parameter while the surface orientation of objects has two degrees of freedom. Physics Innovations Inc. is developing a thermal imaging technique for determining surface orientation where, in each image pixel, two parameters are sensed simultaneously. The two parameters, percent of polarization P and angle of the plane of polarization (phi) , are directly related to the two angles of surface orientation. In this paper the uncertainties in determining P, and (phi) using the Physics Innovations sensor are made explicit by analytical expressions and by computer simulations of the images. These uncertainties are related to temporal and spatial noise characteristics of the imaging system and to the polarization efficiencies of the polarizers. Automatic object recognition using polarization information is dependent on the uncertainties in determining P, and (phi) .

Patent
13 Oct 1994
TL;DR: In this article, a range imaging sensor for classifying and determining the position and orientation of remote objects combines a high resolution three-dimensional range imaging camera with a conventionally configured data processor.
Abstract: A range imaging sensor for classifying and determining the position and orientation of remote objects combines a high resolution three-dimensional range imaging camera with a conventionally configured data processor. Three-dimensional object geometry sensed by the camera is compared with a plurality of three-dimensional models stored in a memory of the data processor. The spacial relationship between iteratively selected models and the sensed object is evaluated for varying positions and orientations of the model, and an optimum object classification and object position/orientation are detected and transmitted as an output signal.