Abstract: A method and arrangement for reproducing an original image, scans and digitizes an original image into pixels of a digitized image. A dot template, a bit-depth, and a dot type structure are selected. A set of gray dot patterns are generated from the dot template, pixel bit-depth and dot type structure that are selected. A 4-quadrant tone reproduction on the set of gray dot patterns is then performed to produce a set of thresholding values at each pixel of the digitized image. A first signal corresponding to a gray level halftoned representation of the digitized image using the thresholding values is then produced. From the first signal, a gray level halftoned reproduction of the original image is printed.

Abstract: A color information reading apparatus wherein the apparatus basically comprises an original information reading unit provided with a photoelectric converter element, for scanning an original once with each of first and second light of different colors so as to convert light reflected from the original into electric signals, thereby outputting the converted respective signals in line sequence, an amplifier for amplifying each output from the photoelectric converter element, a bi-level digitizing circuit for representing the output of the amplifier in binary form, a plurality of line memories for storing therein data output from the bi-level digitizing circuit, a threshold level shifting device for changing the threshold level to another for each pixel, a color discriminating circuit for discriminating among colors base on data representing in binary form the signal obtained by scanning the original with the first light and data representing in binary form the signal obtained by scanning the original with the s

Abstract: This invention relates to an image binarization threshold computing apparatus comprising a window scanning means for setting a window of predetermined area over a multilevel image and scanning the same image, a first information generating means for generating a first data on brightness of the image within the window, a second information generating means for generating a second data on fitness of the image within the window with respect to a preset pattern, a third information generating means for generating a third data serving as a picture quality assessment criterion from the first and second data, and an optimal threshold computing means for calculating the optimal threshold value providing the best picture quality according to the third data.

Abstract: In a document scanner that is operating in the binary mode, the magnitude of the signal that is generated for each picture element (PEL) of each document scan line is compared to the magnitude of a threshold signal. Either a binary 0 or a binary 1 is generated as a result of this comparison. The threshold signal magnitude is dynamically established by a method and an apparatus that provides a stored history or histogram of the various signal magnitudes that are generated for each PEL of a plurality of the document scan lines. Since the signal magnitude(s) that is provided by scanning the background, non-image, area of the document occurs the majority of the time within this histogram, the magnitude of this majority signal(s) is used to set the threshold signal magnitude. As a result, the PELS of the document's visible image are converted to a binary electronic image with a minimum loss of visual image content.

Abstract: A method for the optimization of optical scanners by automatically determining image processing threshold values using a novel threshold calibration sheet. The calibration sheet image has lines at a forty-five degree angle to the path of the document through the scanner and has a predetermined image dot count. One embodiment comprises the steps of repetitively scanning the sheet until scanner threshold values which satisfy predetermined relationships with said dot count are determined. Another embodiment comprises the steps of a single calibration scan with multiple processing of the gray scale scan data on a host computer. By using this method, two or more scanner cameras can work together on processing document images and consistently give uniform results, independent of their individual technical operating or performance differences.

Abstract: An image data processing apparatus binary-codes an image signal obtained from an image sensor of the CCD type or the like so as to output a binary-coded image signal. The image signal obtained from the image sensor A/D-converted into digital image data. Based upon the digital image data, average values of luminance values of the digital image data are calculated for an array of pixels in a preselected area of the CCD. This average value is used as a threshold level for binary coding the image data for these pixels at the center portion of this preselected area. Furthermore, to detect coutours this data processing apparatus calculates a gradient in the luminance values of the pixels in a portion of the preselected area of the CCD in an X direction and a Y direction, and the gradient value is used to obtain binary-coded data in accordance with the above-described method.

Abstract: Saturation problems are alleviated, when displaying image data on a device capable only of displaying pixel intensity values between a minimum value (Imin) and a maximum value (Imax), by smoothly mapping source intensity values greater than a threshold value (T), which is intermediate the minimum and maximum values, to output intensity values (Io) in a range between the threshold value (T) and the maximum value (Imax). Intensity values darker than the threshold value are not altered by the image generator with the result that image detail in the lower range of values is not lost. In order to maintain the correct color balance where separate color component intensities are defined in the source image data, each color component is mapped in accordance with a mapping determined for the largest color component value.

Abstract: An apparatus for converting image signals into binary signals is disclosed. The apparatus comprises: a binarizing section for binarizing image signals; a connectivity distribution section for obtaining connectivities between pixels from binary signals and for producing a connectivity distribution; and a judging section for, from connectivity distributions obtained with different binary levels, judging the level at which the frequencies of maximum and minimum connectivities are highest and the sum of the frequencies of intermediate connectivities is minimal.

Abstract: A digital binarization circuit for image data includes a background level detecting circuit which uses a video signal as a reference input for determining the background level of an image represented by the video signal, and outputs the background level as a first address signal. A character level detecting circuit compares the video signal with a character level in a load decision comparator and loads the video signal as a character level when the signal is less than the reference level, and outputs the character level as a second address signal. A memory circuit ouputs a threshold value stored at an address designated by the first and second address signals to a comparator. The optimum threshold value is outputted among prescribed threshold values stored in the memory circuit. The comparator compares the digitized video signal with the optimum threshold value and outputs a binary signal corresponding to the comparison result.

Abstract: A binary digitizing system which is effective when it is desired to reproduce a picture having a half-tone level with use of, for example, a dot printer or the like. Binary threshold data for comparison with a current picture signal is randomly changed slightly within a predetermined range to such an extent that users cannot recognize change in the level of the binary threshold data, thus preventing the continuation of such regular binary pattern. Further, the binary threshold data for comparison with a current input picture signal is changed according to a desired density to obtain a binary picture signal corresponding to the desired density.

Abstract: A scanner device can be used in a facsimile machine or the like for reading a document on line basis. Each line of the document is read on pixel basis while irradiating a light onto the document. The scanner device includes an image sensor which receives a light reflected from the document and converts the light to an analog electrical signal. A controller controls the reading operation of the image sensor. A comparator translates the analog electric signal into a binary signal. The binary signal is stored in a shift register wherein the contents therein represents an image of a preceding line with respect to the present line being read by the image sensor. A threshold value applied to the comparator to read the present line image is varied depending upon the preceding line data stored in the shift register. As such, images on the document can be read with excellent fidelity, particularly when a fine line extending in a main scanning direction is present on the document.

Abstract: A digital image preprocessing method for eliminating background patterns and scenes from digitized gray level document image data. The method accepts multi-gray level image data as input and produces a gray level output image containing a "white" background. Document image backgrounds are eliminated (or suppressed) by computing a separate (and typically different) threshold value for each gray level pixel of the original document image. Input image pixels whose gray level is greater (brighter) than the threshold value are assumed to be background picture data and are modified to be "white" pixels in the output image. The pixel threshold value is determined dynamically pixel-to-pixel based on gray level pixel data observed within the input image. Additionally, the pixel threshold can be automatically controlled to insure retention of written and/or printed information present in the input image.

Abstract: An image processing apparatus comprises: first binarizing means for binarizing input image data by an average value based on the binarized data of pixels near an objective pixel which has already been binarized; second binarizing means for binarizing the input image data by a predetermined threshold vlaue; and selecting means for selecting either one of the first and second binarizing means in accordance with whether the input image data indicates an edge portion or not, whereby by selecting either a binarizing process by the average density preservation method or a binarizing process by a fixed threshold value in accordance with the presence or absence of an edge of input data, an image of a high grade can be reproduced for either a half tone image or a character image.

Abstract: An image processor performs error diffusion by thresholding an incoming gray pixel to black or white, comparing the difference between the black or white print value and the incoming pixel gray level and superimposing the difference on the next pixel gray level. The threshold value is read out from a threshold matrix which has been modulated with a pattern which is complementary to the known artifact pattern of the error diffusion process. Typically, the threshold matrix has sparce threshold values along one of its diagonals, the direction of the diagonal being perpendicular to the prevailing direction of artifacts generated by the error diffusion algorithm.

Abstract: In the present invention each input pixel value is compared against a randomly selected threshold value to provide an output pixel having a value indicative of which of the values is greater. The threshold value is selected from one of a plurality of threshold matrices, each having a predetermined number of threshold values that are arranged in a pattern with the values for a base matrix being increased by an increment for each succeeding one of the plurality of threshold matrices. The selection of the one threshold matrix is made by means of a pseudo-random number generator.

Abstract: A line region segmentation method includes the steps of grouping pixels of an input image indicated by image signals into three sets of black, gray and white pixels, performing a pattern matching of black pixels in a region of the input image with a set of matrix patterns to determine if a black pixel is closely associated with other pixels and determine if a black pixel is one of screened black pixels for each pixel of the set of black pixels, deciding if the black pixel being considered is one of black bilevel pixels by checking the number of black pixels that are determined as being associated black pixels and as being non-screened black pixels, performing a pattern matching of white pixels in a region of the input image with a set of matrix patterns to determine if a white pixel is closely associated with other pixels for each pixel of the set of white pixels, deciding if the white pixel being considered is one of white bilevel pixels by checking the number of white pixels that are determined as being ass

Abstract: An image processing method distinguishes an object from within an image area by determining a stable threshold value of light intensity values from within the image area. Received light is converted into image data denoting light intensity values of the received light at a plurality of points from within the image area. A bright portion average value denoting an average of the light intensity values which exceed a predetermined threshold and a dark portion average value denoting an average of the light intensity values which are less than the predetermined threshold are calculated. A new threshold is obtained by applying the bright portion average value and the dark portion average value to a predetermined dividing ratio. The object within the image area is distinguished using the new threshold. The method is also applicable to the use of multivalue thresholds.

Abstract: An image region segmentation system for segmenting a color image into a number of elemental regions according to the type of images contained in the elemental region comprises a first detection circuit for discriminating whether an elemental region under processing contains a black pixel or not, a second detection means for discriminating whether the elemental region under processing contains a color pixel or not, a first discrimination circuit for discriminating the elemental region as to whether or not the region includes a black pixel and simultaneously no color pixels, a line image recognition circuit for discriminating as to whether the image in the elemental region under processing includes a line or not, and a second recognition circuit for discriminating such that the elemental region under processing represents a bi-level black line when the elemental region under processing contains a black pixel and simultaneously no color pixels and further simultaneously when the elemental region represents a lin

Abstract: A video image processor for generating an enhanced image of data based upon input gray scale picture element values of image data of a document background and printed information contained thereon generates a histogram of the gray scale picture element values for each tile of image data for an area of the document representing the frequency of occurrence of picture elements of a particular gray scale value. A correlator processes each histogram to determine a back reference level and a white reference level for each tile. Normalization factors are calculated based upon the black reference level and the white reference level. The input gray scale picture element values for each tile of the image data associated with the normalization factors of each tile are normalized based upon the normalization factors for each tile and correlated to generate a normalized and correlated representation of the image data.

Abstract: For highlight or dark areas of images, the error terms diffused to neighborhood pixels include components which are periodic with respect to a wavelength where the wavelength is a function of the density level of the pixels from which the error terms are diffused. In this manner, patterned artifacts or "worms" in the highlight or dark areas of the images are reduced or illuminated.

Abstract: Image processing apparatus having an input device for inputting the data of an objective pixel, calculator for obtaining an average density value in a specified region and a quantizer for quantizing the data of the objective pixel based on the average density value. The entire image including its edge being effectively binarized and during serial scanning of the data continuity not being lost at the connection of scans, thereby obtaining an image with excellent gradation and resolution.

Abstract: A scan apparatus, comprising: a platen on which a document can be placed; a criterion member on which at least one black zone and at least one white zone are formed successively in the subscan direction, criterion member being arranged near the platen on the side from which a subscan is started; a device for detecting a linear optical image of the document to obtain the density distribution of the linear optical image; a device for scanning the criterion member and a document in the subscan direction which includes a device that illuminates a document placed on a document area of the platen and the criterion member; and a device for determining a reference timing for starting a scan of the document on the platen, which is connected to the device that detects a linear optical image so as to detect a boundary between the black and white regions and determine the reference timing from the boundary detected.

Abstract: An extractor extracts, from image data to be binarized, a feature amount of a target pixel including at least a maximum density difference among pixels in a local region including the target pixel. A predictor predicts an image type of the target pixel in accordance with a minimum density value among the pixels in the local region. A selector selects one of the feature amount of the target pixel from the extractor and a feature amount obtained by adding the feature amount of the target pixel to feature data of neighboring pixels in accordance with the image type predicted by the predictor. A discriminator discriminates the image type of the target pixel in accordance with the feature amount selected by the selector.

Abstract: Apparatus and methods for converting continuous grey tone images into high resolution halftone images utilize an iterative, multi-level, multi-resolution error convergence process. The continuous grey tone image is first binarized. At each level of the process, the binarized image is compared with the grey tone image over a larger window of pixels. Within each window, selected binarized image pixels are tested for possible change in binary assignment. The binary assignment of a given test pixel is changed if the change would result in a lower average error over the entire window. By varying the selection of test pixels, the process can provide clustered dot patterns and dithering.

Abstract: An image forming device which can form an image by printing a plurality of dots based on an image information that contains a plurality of density data corresponding to a plurality of pixels defined by the fractionalization of the original image, and which can express the density of an image by controlling the number of dots to be printed within a predetermined tone unit area. The image forming device includes a threshold pattern generator for generating a threshold pattern which is a repetition of a basic pattern including a predetermined number "L" of thresholds, a comparator for comparing respective density data with a predetermined number "M" of thresholds selected from all "L" of the thresholds in which "L" is not an integer multiple of "M", and for producing a predetermined number "M" of print data corresponding to the respective density data; and a printer for printing on a printing sheet dots corresponding to the "M" print data in a line along a main scanning direction.

Abstract: A binarization method obtains an optimum threshold value for binarization which is used when converting a multi-level image data which describes an input image into a black-and-white bi-level image data. The binarization method includes the steps of counting a first number of black picture elements by varying a threshold value from a darkest tone level to a lightest tone level, counting a second number of picture elements having a tone level other than the lightest tone level, obtaining a percentage of the first number with respect to the second number for each of the varied threshold values so as to normalize a density of the input image, and determining the optimum threshold value for binarization based on the percentage which is obtained for each of the varied threshold values.

Abstract: An apparatus for determining a background level of an image to be scanned. The apparatus builds a series of histograms of the image each corresponding to a line of the image, analyzes each of the histograms, and averages the results of the analysis, to continually update a background level during the scan of the image. The apparatus may be implemented with a simple architecture capable of operating at high speed.

Abstract: During segmentation of individual characters in a column, the invention predicts for the next character an optimal minimum gray level sensitivity threshold while scanning pixel rows between characters by lowering the threshold unless or until noise in the image causes the scanner to detect too many "ON" pixels between adjacent numerals. During subsequent attempts to recognize the segmented character, the invention computes a confidence score and increases the sensitivity threshold above the predicted level if the confidence score is insufficient.

Abstract: An image processing apparatus including an input circuit for receiving image data, a binarizing unit for binarizing a subject pixel of the image data supplied from the input circuit, an error detector for detecting an error between a binarized image data obtained by the binarizing unit and the image data supplied from the input circuit, an error diffusing circuit for diffusing the error on other image data associated with other pixels around the subject pixel, a compensating unit for compensating the image data of the subject pixel by using a compensation data which is caused by a previous error diffusion of the error diffusing circuit, a circuit for detecting an image density of the image data for a prescribed image area surrounding the subject pixel and a controller for controlling the compensating unit in response to the image density detected by the image density detecting circuit.

Abstract: An image recording apparatus reproduces a halftone image with high resolution by using a systematic diether method and an error scattering method. Sharpness of an image to be reproduced is selectively variable.

Abstract: To read a document accurately and produce an image signal faithfully representing the document, an image reading method and apparatus adopts various means, of "latching an average light-shielded signal in a digital form", "using an average light-shielded signal resulting from averaging output signals of a plurality of light-shielded pixels as a black reference signal", "replacing that part of an image signal in which an average light-shielded signal is larger than an effective pixel signal in level with a signal of a zero level", "driving CCD sensors at such timing as to allow effective pixel signals output from the CCD sensors to be continuous in time" and "setting DC offset voltages of signals output from CCD sensors to a predetermined clamp potential.

Abstract: An image signal processor is capable of precisely reading a dark-colored character or the like drawn on a light-colored background, such as a white board, and to perform binary encoding, but also capable of precisely reading a light-colored character or the like drawn on a dark-colored background, such as a blackboard, and to perform binary encoding. The image signal processor includes an automatic gain control circuit for receiving an image signal generated by an image pickup element and for changing to either a first cutoff frequency for performing automatic gain control on only a low-frequency component of the signal or a second cutoff frequency for performing automatic gain control on both the low-frequency component and a high-frequency component of the image signal.

Abstract: An image processor analyzes objects such as work pieces passing along an assembly line. The processor stores a reference ratio of exemplary signal levels from the object and its background. As subsequent images are processed, a signal level for the image background is detected and multiplied by the reference ration to derive a theoretical signal level for the object in the image. The theoretical signal level and the actual signal level for the object are compared to detect a predetermined relationship therebetween. When the predetermined relationship exists, the amplification of the image signal is adjusted to achieve a predetermined difference between the background and object signal levels. If the predetermined relationship does not exist, the amplification of the image signal is adjusted to achieve a predetermined difference between the background image signal level and the theoretical signal level for the object.

Abstract: According to an image signal processing apparatus in accordance with the present invention, an input signal is converted to a digital image signal and then the digital image signal is cyclicly shifted. Therefore, a desired signal component can be collected on a first or second level side. Therefore, a signal can be divided into bilevels in reference to one threshold value or it can be divided into multiple levels in reference to a plurality of threshold values. As a result, it is possible to precisely extract contours of the image signal even if there is a small density difference between a background signal and an information signal. In addition, a background can be converted between white and black.

Abstract: An image scanner for producing a halftone image is provided with a halftone signal generator which generates an exposure signal (S) for controlling the exposure duration of a laser beam (L) which beam is focused on a photosensitive material. The halftone signal generator is so constructed that image data (N) is compared with a threshold data (screen pattern data) for each elementary area and the exposure duration for each elementary area is determined mainly according to a difference between the image data and the threshold data. Some of the elementary areas are partially exposed, to an extent which depends on the exposure duration.

Abstract: A system for converting gray-level input data into binary output data and efficiently preserve much of the original sharpness information. The input data is divided into halftone cells which correspond to several pixels in the original image information. The halftone cells are further divided into subcells which correspond to a plurality of pixels in the halftone cell. The subcells are thresholded with a matrix of threshold values to determine which binary pixels are to be rendered. Any error between the rendered pixels and the average density value of the subcell input values is propagated to adjacent subcells. The thresholding of the subcell pixels can use a separate threshold value for the individual pixels or can use an average threshold value for the entire subcell.

Abstract: A method of dynamically adjusting the threshold level of an error diffusion algorithm to selectively control the amount of edge enhancement introduced into the encoded output. The threshold level is selectively modified on a pixel by pixel basis and may be used to increase or decrease the edge enhancement of the output digital image, thus, more closely representing the original detail and edge sharpness of the continuous tone input image.

Abstract: An image reading apparatus such as facsimile or digital copying apparatus comprises: a lamp to illuminate an original; an image reading device such as CCD to read the original image line by line; a memory to store dark-output data (data output from a reading while the lamp is off) of the reading device by an amount of one line; and a correction circuit to correct the image data obtained by reading the image by the reading device every pixel on the basis of the data stored in the memory. A black level of the image data is corrected by the correction circuit and the memory stores the dark output data of the reading device before the image is read. The memory also stores the output data of the reading device when the lamp is off. With this apparatus, the unevenness of the output image signals which is caused due to a variation in dark currents obtained by photoelectrically reading the original image can be corrected by eliminating the unevennesses of the black and white levels of the CCD line sensor.

Abstract: Thresholding and background referencing apparatus are disclosed for use with apparatus for scanning documents having images with object and background regions. The background referencing apparatus receives, from the scanning apparatus, a video signal representing the document image and generation a signal having a value representative of an estimate of the background density level of the document being scanned. The apparatus produces a difference signal representative of the difference between the estimated background level signal and the received video signal. The estimated background level signal is stored, and updated in response to (1) the difference signal being of a first sign associated with transition from object to background, and (2) only small difference signals of a second sign associated with transition from background to object, whereby large difference signals of the second sign result in substantially no change in the stored estimated background level signal.

Abstract: An image processing system for converting gray level, digital, pixel information into binary data. Pixels with digital values close to the threshold value are further processed to determine the binary value to be specified for that pixel. In such cases, the adjacent horizontal pixel is tested and, if that test is inconclusive, the adjacent vertical pixel is tested. Depending upon the tests of whether the adjacent pixels were also close to the threshold value, the current pixel value is assigned the opposite value as the previous adjacent pixel. This has the effect of specifying, for transition areas at the boundaries of text characters and graphic lines, alternating pixels which produce a serrated edge along the borders of the character or line. These edges are of high spatial frequency and are substantially undetectable under ordinary circumstances by an observer. These edges are also smoothed in the printing process by the fusing of the toner to the output medium.

Abstract: In an electronic image scanning device having an array of photosensitive elements, or photosites, arranged and supported for deriving electronic image information from an original, an arrangement for input of control information to the device includes a surface with a plurality of unique control images thereon, detectable by the photosites, is arranged for operator controlled movement. The scanning of the control images occurs during a non-image scanning period in the operation of the scanning device. The unique control images are recognized as control information. The operator controlled movement reflects operator selection of control information.

Abstract: An image reader comprises a line image sensor for reading images of an original for every line, a CPU for extracting the density level of the background based on the read image data for comparing the extracted density level with a reference level to find the difference, light adjusting circuit for adjusting the intensity of a lamp for exposing the original so as to make the difference obtained by the operation equal to 0 and a compare circuit for converting the read image data to binary data, wherein the adjustment of the intensity of the lamp by the light adjusting circuit is carried out in parallel to the conversion of the image data by the compare circuit.

Abstract: An image processor converts a multiple gray-level image to a bi-tonal image using both error diffusion and ordered dither to enhance image quality. The error diffusion process is attenuated smoothly as the local area intensity approaches a light or dark maximum, while the ordered dither process is attenuated smoothly as the local area high spatial frequency content increases.

Abstract: A half-tone binarization generator that produces high-quality half-tone binarization images by converting multilevel brightness information into sets of black and white bitonal data by adding noise to the multilevel brightness information and using a thresholding technique.

Abstract: An image processing device capable of processing images containing poorly contrasted letters and/or bold letters in addition to well contrasted letters and pictures such that both resolutions of letters and tones of pictures can be preserved. The device may includes a circuit to distinguish two level images from non two level images according to image concentration related quantity, and a circuit to distinguish picture images out of non two level images according to another image concentration related quantity. The device may include a circuit to distinguish letters from pictures according to the maximum and the minimum values of the image concentration related quantity. The device may includes a circuit to distinguish letters from pictures according to the maximum and the minimum values of changes in the image concentration related quantity.

Abstract: A feature-analyzing section determines whether a given picture element included in image information supplied from a line buffer represents a character portion or a photograph portion. In accordance with the determination made by the feature-analyzing section, a threshold value selection section selects either a threshold value calculated by a first threshold value calculation section, and to be used in relation to charcter portion, or a threshold value calculated by a second threshold value calculation section, and to be used in relation to photograph portion. By using the threshold value selected by the threshold value selection section, a binary-encoding section binary-encodes image information which is supplied thereto through a delay circuit. On the basis of the determination made by the feature-analyzing section, a determination section determines whether or not the given picture element represents a bold character portion.

Abstract: An image processing system for obtaining a binary signal from a multi-level signal read by an image scanner from an original document including mixed characters, ruled lines, and photos, and then obtaining a reproduced image from the binary signal, the image processing system including: a fixed slice processing unit for receiving said multi-level signal, and for slicing the multi-level signal by a predetermined fixed threshold level, and outputting the binary signal sliced by the fixed threshold level; a half-tone processing unit for receiving the multi-level signal, and for slicing the multi-level signal by a plurality of threshold levels defined by a dither method, and outputting the binary signal sliced by the plural threshold levels defined by the dither method; a character/photo separating unit for receiving the multi-level signal; and for detecting a pattern of the multi-level signal, separating either a character portion or photo portion based on the pattern, and outputting a selection signal; a select

Abstract: A circuit arrangement is composed of a first adder whose first output is assigned to the digitized output signals of the photosensors and a second input connected to the outputs of a white level memory, and a second adder at whose input side the currently stored white level are linked with the correction signal and which reads the resultant signal back into the white level memory, the comparator following the first adder which, dependent upon the threshold level derived from maximum and average blackening values of the output signal of the first adder supplies a black signal or a white signal. A correction signal derived from a plurality of influencing variables serves for white level correction, the correction signal supplying a white level increment/decrement for delivery into the white level memory dependent on a carry signal that appears or, respectively, that does not appear at the first adder.

Abstract: An optical character reader apparatus includes an image sensor, and a background reflection plate having such reflectivity which allows the image sensor to detect the entry of a document carrying thereon image information such as characters, graphics or the like within the field of view of the image sensor.

Abstract: Apparatus for enhancing and thresholding scanned microfilm images, specifically for removing single pixel noise therefrom, and accompanying methods for use therein are disclosed. Specifically, this apparatus convolves each one of a pre-defined group of incoming pixel values with a corresponding one of a pre-defined set of coefficients in order to generate an convolved pixel value. The convolved pixel is then compared against a threshold level to produce a thresholded pixel value indicative of the results of the comparison. The inventive apparatus also includes a noise processing circuit that contains a noise tracker and a noise detector and filter circuit. The noise tracker is used to produce a noise value that tracks a noise level present in the threshold pixel value.