Photographic copier image contrast control
First Claim
1. In a hard copy recorder, in which light-sensitive paper or film is exposed to an image produced by a cathode ray tube, apparatus for controlling image contrast comprising:
- a source of video signals;
first and second controls for separately adjusting image intensity and background shading;
means, coupled to said first and second controls, for developing a first control signal representative of background shading, and for developing a second control signal representative of image intensity and determining a maximum intensity level established solely by said image intensity control setting;
means for amplifying video signals produced by said source by a factor determined by said second control setting;
means for producing a video pedestal signal exhibiting a level determined by said first control signal;
means for combining said amplified video signals and said video pedestal signal; and
means for applying said combined signals to said cathode ray tube.
1 Assignment
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Accused Products
Abstract
A thermally developed photographic copier is provided having two controls, one for adjusting the contrast, or blackness, of an image, and another for adjusting background contrast. A microprocessor samples and processes the settings of these controls to produce a video pedestal determined bythe background contrast control, and a gain control signal adjusted for effects of the background contrast setting to keep amplified video singals within the dynamic range necessary for the image contrast setting. Video signals used to expose light-sensitive paper or film are amplified in accordance with the gain control signal and combined with the video pedestal for desired background contrast. The system can automatically modify the gain and video pedestal levels for different lots of paper or film by recording a calibrated grey scale, scanning the recorded grey scale image, comparing the scanned image with previously stored information on the desired image, and modifying the gain and pedestal values as necessary to reproduce images of the desired appearance.
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Citations
10 Claims
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1. In a hard copy recorder, in which light-sensitive paper or film is exposed to an image produced by a cathode ray tube, apparatus for controlling image contrast comprising:
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a source of video signals; first and second controls for separately adjusting image intensity and background shading; means, coupled to said first and second controls, for developing a first control signal representative of background shading, and for developing a second control signal representative of image intensity and determining a maximum intensity level established solely by said image intensity control setting; means for amplifying video signals produced by said source by a factor determined by said second control setting; means for producing a video pedestal signal exhibiting a level determined by said first control signal; means for combining said amplified video signals and said video pedestal signal; and means for applying said combined signals to said cathode ray tube.
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2. In a hard copy recorder, in which light-sensitive paper or film is exposed to an image produced by a cathode ray tube, apparatus for controlling image contrast comprising:
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a source of video signals; first and second controls for separately adjusting image intensity and background shading; processing means, coupled to said first and second controls, for producing a pedestal level signal functionally related to the setting of said second control independent of the setting of said first control, and for producing a gain control signal which establishes a maximum intensity level offset for effects of background shading; means for producing a video pedestal signal in response to said pedestal level signal; means for amplifying video signals produced by said source by a factor which is a function of said gain control signal; means for combining said amplified video signals and said video pedestal signal; and means for applying said combined signals to said cathode ray tube.
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3. In a hard copy recorder, in which light-sensitive paper or film is exposed to an image produced by a cathode ray tube, apparatus for controlling image contrast comprising:
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a source of video signals; a first control for producing a background shading control signal; a second control for producing a dynamic range control signal; processing means, coupled to said first and second controls, for producing a pedestal level signal which is a function of said background shading control signal, and for producing a gain control signal for amplifying video signals to be within the dynamic range established by said dynamic range control signal; means for amplifying video signals produced by said source as a function of said gain control signal and for offsetting said amplified signals from a nominal baseline level by an amount which is a function of said pedestal level signal; and means for applying said amplified and offset signals to said cathode ray tube. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10)
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Specification