Hewlett-packard Company

Kenneth D Gennetten

Steven L Webb

Edward S Beeman

Craig L Miller

David Douglas Bohn

Paul M Hubel

Stephen Paul Langford

Wayne G Phillips

A sensor assembly and an optical image color scanner using the sensor assembly. The sensor assembly is of the type having three separate rows of optical sensors. Two of the three sensor rows have color filters and one is unfiltered (receptive to white light). For gray scale scanning, only the unfiltered (white) sensor row is used, thereby maximizing the speed of gray scale scanning. For color scanning, three color values are computed as a linear transformation of values from the two filtered and one unfiltered values. The linear transformation may be as simple as subtracting signals from the two filtered sensor rows from the signal from the unfiltered (white) sensor row. For color scanning, memory buffers are required for two of the three sensor output signals. For highest accuracy in color scanning, the exposure time for the white sensor row is reduced relative to the exposure time for the two filtered sensor rows. An optional white channel bandpass filter (passing all wavelengths within the human visual range and rejecting wavelengths outside the human visual range) provides improved accuracy if the light source has significant wavelengths outside the human visual range.

Sensor assembly providing gray scale and color for an optical image

An image scanning device, including CCDs provides digital color image data representing an image. A 3-by-3 matrix multiply logic is connected to the image scanning device for modifying or transforming the intensities of each individual color encoded in the digital color image data. The matrix multiply logic has a multiplier and an accumulator. The multiplier provides intermediate products by performing one-stage multiplications between the intensity values for each pixel and the coefficients of the 3-by-3 matrix. The one-stage multiplications are time multiplexed. The accumulator accumulates the intermediate products from the multiplier for each pixel to thereby provide optimized color values for each pixel. The multiplier implements specialized adders to perform the one-stage multiplications.

Digital color matrixing circuit

A document scanner provides compensation for sensitivity nonuniformity that may exist between the individual sensor cells of the sensor array that is used to sense light reflected from a document being scanned. Compensated is provided for both dark (i.e. unilluminated) sensitivity variation and light (i.e. illuminated) sensitivity variation that may exist in the individual sensor cells of the sensor array.

Method and apparatus for providing sensor compensation

A document scanner is disclosed wherein means are provided to dynamically compensate for any changes in document illumination intensity that may occur as a document is scanned. The compensation method and apparatus operates to measure the intensity of light that is reflected from a target area that borders an edge of the document being scanned. The target area is a narrow, elongated, area that extends in the scan direction. The target area is of a color to approximate the document's background area, i.e. the document's nonimage area. Since the target area is of a continuous and uniform color tone, any variation in the quantity of light that is reflected from the target area is caused by a variation in the intensity of illumination thereof by the scanning light source. The method and apparatus of the invention controls the scanning light source so as to maintain the light reflected from the target area at a substantially constant magnitude.

Method and apparatus for providing illumination compensation in a

A delay circuit for producing in an electrical circuit a time delay. The circuit includes a pulse generator which produces an edge at a given time interval after an edge is applied to its input. The time interval can be adjusted so that it automatically follows a reference time interval such as a clock period. The circuit has application in the read circuitry of digital tape devices.

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Fort Collins, CO, United States of America

Kenneth D Gennetten