Abstract: Experiential gradation correction curves for sample images are prepared. By analyzing the experiential gradation correction curves and accumulated density histograms of the sample images, two points (Y.sub.1, Q.sub.1) and (Y.sub.2, Q.sub.2) are specified, where Y.sub.1 and Y.sub.2 are values of accumulated occurrence and Q.sub.1 and Q.sub.2 are halftone dot percentages for image reproduction. The values Y.sub.1 and Y.sub.2 through an accumulated density histogram of an original image whose gradation is to be corrected. A gradation correction curve Q=G(x) is determined so as to pass through the two points (x.sub.1, Q.sub.1) and (x.sub.2, Q.sub.2).

Abstract: A method and apparatus for detecting the shape of a beam spot on a scanning plane in a scanning optical system having a constant scanning speed. When a relative moving speed of the light beam is not known beforehand, four slits are used to detect intensities of light passing through the slits. Three of these slits have different angles of inclination with respect to a scanning direction, and the remaining slit has the same angle of inclination as one of the three slits. When the moving speed of the light beam is known in advance, the first-mentioned three slits are used. The moving speed of the light beam is derived from a time lapse between signals detected through the two slits having the same angle of inclination. Once the moving speed of the light beam is known, periods of movement required for the light beam to traverse the three slits having different angles of rotation are obtained on the basis of detection signals relating to these slits.

Abstract: In an image recorder, a recording photobeam and a reference photobeam are periodically deflected by a polygon mirror in a main scanning direction. The recording photobeam is supplied to a photosensitive film while the reference beam is supplied to a transparent grating scale on which a transparent area and an opaque area are formed. The combination boundary of the transparent area and the opaque area has a portion parallel to the main scanning direction. The reference beam transmitted through the transparent area is detected, and the photobeams are deflected in a subscanning direction by an acoustic-optical deflector in response to the detected optical amount of the reference photobeam.

Abstract: A clock generator (15) and a delay circuit (16) create N dot recording clock signals (.phi..sub.1 to .phi..sub.N) of a cycle t, delayed by t/N. A counter (20) counts a detecting time interval between a start sensor (12) and an end sensor (14) for every surface of a polygon mirror (8) to generate time resolution t/N. The difference between the count value and a reference count value set in a latch (24) is input to a subtracter (23), so that a translation table (28) outputs clock crossover timing responsive to the difference. A latch (17) and an encoder (18) select an N dot recording clock signal synchronous with detection output of the start sensor (12) for every surface of the polygon mirror (8). A second selector (33) outputs a crossover dot recording clock signal (.phi..sub.X) for image recording by performing crossover from the selected dot recording clock signal to other dot recording clock signals that are sequentially along the clock crossover timing.

Abstract: A clock generator (15) and a delay circuit (16) create N dot recording clock signals (.phi..sub.1 to .phi..sub.N) of a cycle t, delayed by t/N. A counter (20) counts a detecting time interval between a start sensor (12) and an end sensor (14) for every surface of a polygon mirror (8) to generate time resolution t/N. The difference between the count value and a reference count value set in a latch (24) is input to a subtracter (23), so that a translation table (28) outputs clock crossover timing responsive to the difference. A latch (17) and an encoder (18) select an N dot recording clock signal synchronous with detection output of the start sensor (12) for every surface of the polygon mirror (8). A second selector (33) outputs a crossover dot recording clock signal (.phi..sub.X) for image recording by performing crossover from the selected dot recording clock signal to other dot recording clock signals that are sequentially along the clock crossover timing.

Abstract: A halftone image recording apparatus has an interpolating function for interpolating previously obtained first halftone pattern data in the main scanning direction to obtain second halftone pattern data. Comparisons between input image signals and the second halftone pattern data per pixel are made to expose a photosensitive material on the basis of the results of the comparisons thereby to create a halftone plate. Through the interpolation, the recording density in the main scanning direction is increased in response to the rate of increase in pixel density.

Abstract: Image signals inputted from an input device are subjected to A-D conversion through an A-D converter to be stored in memory by at least an adjacent pair of pixels. The pair of pixels are interpolated by interpolation arithmetic circuit so that generated interpolation data and data on the pair of pixels are ordered under control by a timing controller to be outputted.

Abstract: An image signal of the input and/or the output side is (are) multiplied by a shading compensation signal obtained from the output signal of a low-pass filter employed in a PLL circuit or a greating signal multiplying means.

Abstract: In a method for emphasizing sharpness in picture scanning recording time in a picture reproducing machine a central picture signal obtained by scanning an original picture according to the scanning sequence and peripheral picture signals of the central picture signal which are appropriately weighted are added to the central signal and averaged to obtain vignette signals, and they are appropriately calculated for emphasizing sharpness of the picture signal. In the method as the peripheral picture signals desired numbers of continuous picture signals are selected by centering the central signal in the main scanning and the sub-scanning directions independently.

Abstract: Calibration and shading correction of output image data of a photosensor array are carried out simultaneously by varying the gain and offset value of a photosensor amplifier in synchronism with input scanning of an original. The variation of gain and offset is made as a function of a first density reference voltage obtained by scanning a first density reference board, a second density reference voltage obtained by scanning a second density reference board and ideal voltages corresponding to the first and the second density reference voltages.

Abstract: An image signal is obtained by scanning an original picture using a sharp beam and an unsharp beam which are different in phase in an image reproducing system.

Abstract: In reproducing images, magnification conversion is performed either by reading image data from a memory in a skipped or overlapped fashion of their addresses of sub-scanning direction factor or by scanning certain scanning lines of an original picture (recording film) in a skipped or overlapped fashion in the sub-scanning direction according to a specified magnification ratio.