An image reading apparatus comprises a photoelectric converter including three linear image sensors of red, green and blue aligned in parallel to each other along a main scan direction. When a document is scanned, a document is read by the photoelectric converter by moving it relative to the document. The moving direction is set to be a first direction, for a prescan and a second direction reverse to the first direction, for a normal scan. Analog output signals of the first to third linear image sensor are converted to digital signals. In a prescan, a selector exchanges the digital signals of the first and third linear image sensors, while in a normal scan, the selector does not exchange them. Then, a line correction section receives the digital signals of the first and third linear image sensors from the selector and the digital signals of the second linear image sensor from the analog-to-digital converter and outputs the digital signals of the first to third linear image sensors by delaying outputs of the digital signals with delay times determined in correspondence to spacial distances between positions of the three linear image sensors and a scan speed along the moving direction. Thus, image data can be read without shifts of output timings of the image data of red, green and blue.
The image reading device has a moving mechanism by which a stage, supporting a read object in which a color image is recorded, is intermittently moved so that the color image is read by a line sensor. In a stopping operation during the intermittent movement, the stage passes slightly over the stop position, and then reverses. Thus, the stage oscillates about the stop position. Substantially simultaneously with the stopping operation, i.e., while the stage is still oscillating, a blue light-emitting diode is turned ON, so that B pixel data is sensed by the line sensor. During this sensing operation of the B pixel data, the oscillation of the stage is fully damped. Then, the B light-emitting diode is turned OFF, and a red light-emitting diode is turned ON, so that R pixel data is sensed. Then, the R light-emitting diode is turned OFF, and a green light-emitting diode is turned ON, so that G pixel data is sensed.
In an image reading apparatus, three line sensors simultaneously read images in different positions of a document and output respective image signals. Line memories receive the image signals and output them with a timing corresponding to the positions in which the images represented by the image signals have been read. Analog signal processing for the image signals is executed in a parallel manner to thereby allow a high-speed image read operation to be achieved with a low-speed analog processing circuit.
An image reading apparatus that reads color images by means of scanning the document surface with CCD sensors that correspond to red (R), green (G) and blue (B) colors respectively, comprising: a diagonal line pattern 4 provided within the CCD sensors' reading ranges; a color shift correction factor arithmetic unit 40 that detects color shifts from the data obtained by reading the diagonal line pattern and calculates correction factors; and a correction arithmetic unit 42 that corrects the document image data for each color component read in the previous step using the calculated correction factors.
A portable data collection device providing for dataform decoding and color imaging. An imaging assembly is provided that includes a board camera having black and white circuitry and generates a composite video signal representing an image of a target area of the imaging assembly when actuated. The imaging assembly includes a two dimensional photosensor array overlaid by a color filter having a repeating pattern of four color filter elements. The imaging assembly is selectively actuatable with a first trigger for reading a target dataform in the imaging assembly's target area and actuatable with a second trigger for capturing a image of the target object in the target area. When the device is operated in the dataform reading mode, compensation circuitry is actuated to operate on digital gray scale values extracted from the composite video signal to adjust gray scale value magnitudes to compensate for the transmittivity differences of the color filter elements to improve decodability of the imaged dataform. When the device is operated in the imaging mode, conversion circuitry is actuated to convert the gray scale values to either Y-C or RGB digital data and a D/A converter further processes the Y-C or RGB digital data to provide an analog Y-C or RGB output signal.
A dot pattern with a plurality of pixels representing a two-dimensional image is formed on a printing plate material by applying laser beams, which are turned on and off for each pixel depending on dot pattern data, to the printing plate material in a main scanning direction, while the laser beams are moved in an auxiliary scanning direction that is orthogonal to the main scanning direction. A threshold matrix having an array of thresholds is obtained for generating a dot where the degree of a variation of the dot periphery length in a main scanning direction is smaller, i.e., a dot where the dot periphery length in the main scanning direction has a smaller standard deviation.
