CRT Digital brightness control
First Claim
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1. In combination:
- a cathode ray tube having a nonlinear transfer function;
a first source of first digital signals corresponding to information to be displayed on said cathode ray tube at a plurality of gray shade levels;
a second source of second digital signals corresponding to the intensity range over which said shade levels are to be displayed on said cathode ray tube;
means for producing third digital signals which are a function of said first and said second digital signals; and
a digital to analog converter coupled between said producing means and said cathode ray tube, said converter having an analog output having an amplitude related by a nonlinear transfer function to said third digital signals, said analog output providing gray shade level consecutive steps having substantially equal ratios of luminance of said chathode ray tube for a plurality of different said second digital signals.
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Abstract
A digitally controlled CRT display system providing display intensity levels having equal ratios of luminances for consecutive steps over a plurality of brightness control settings. The digital video is added to a digital brightness code and the sum is converted to an analog signal that is coupled to the cathode of the CRT. The digital-to-analog converter provides a transfer characteristic such that the consecutive gray shade steps have a constant ratio of luminance.
33 Citations
18 Claims
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1. In combination:
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a cathode ray tube having a nonlinear transfer function; a first source of first digital signals corresponding to information to be displayed on said cathode ray tube at a plurality of gray shade levels; a second source of second digital signals corresponding to the intensity range over which said shade levels are to be displayed on said cathode ray tube; means for producing third digital signals which are a function of said first and said second digital signals; and a digital to analog converter coupled between said producing means and said cathode ray tube, said converter having an analog output having an amplitude related by a nonlinear transfer function to said third digital signals, said analog output providing gray shade level consecutive steps having substantially equal ratios of luminance of said chathode ray tube for a plurality of different said second digital signals. - View Dependent Claims (2, 3, 4)
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5. In combination:
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a cathode ray tube having a nonlinear transfer function; a first source of first digital signals corresponding to information to be displayed on said cathode ray tube at a plurality of gray shade levels; a second source of second digital signals corresponding to the intensity range over which said shade levels are to be displayed on said cathode ray tube; means for producing third digital signals which are sums of said first and second digital signals; and a digital to analog converter coupled between said producing means and said cathode ray tube, said converter having an analog output having an amplitude related by a nonlinear transfer function to said third digital signals, said analog output providing gray shade level consecutive steps having substantially equal ratios of luminance on said cathode ray tube for a plurality of different said second digital signals. - View Dependent Claims (6)
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7. In combination:
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a cathode ray tube display; means responsive to digital video signals for producing a plurality of discrete intensity levels on said display; and said producing means comprising means for maintaining the ratios of luminances of adjacent intensity levels constant for a plurality of different intensity level ranges. - View Dependent Claims (8)
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9. In combination:
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a cathode ray tube display; and means responsive to digital control signals for producing a plurality of discrete intensity levels on said display, said intensity level consecutive steps having substantially equal ratios of luminance for a plurality of display brightness settings.
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10. In combination:
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a cathode ray tube display; means coupled to said display for converting a plurality of digital video control signals each corresponding to a display gray shade level to a plurality of analog signals each producing a different gray shade level on said display; and said converting means having a transfer characteristic producing gray shade level consecutive steps having substantially equal ratios of luminance for a plurality of display brightness settings. - View Dependent Claims (11, 12)
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13. A digitally controlled video display system comprising:
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a cathode ray tube display; means coupled to said display for deriving a plurality of analog video signals from a plurality of digital signals, each of said digital signals corresponding to a gray shade level to be displayed; said analog video signals producing gray shade levels on said display, said gray shade level consecutive steps having substantially equal ratios of luminances; said deriving means comprising a digital adder adapted for input of said digital video signals and brightness encoded digital signals; and said deriving means further comprising means for converting the digital output signals of said adder to said analog signals. - View Dependent Claims (14, 15)
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16. A digitally controlled video display system comprising:
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a cathode ray tube display; a digital adder adapted for input of digital video control signals and brightness encoded digital signals; means coupled to said adder for decoding the output of said adder; means coupled between said decoding means and said display means for converting the output of said decoding means to a plurality of analog signals producing discrete gray shade levels on said display; and said gray shade level consecutive steps having substantially equal ratios of luminances. - View Dependent Claims (17, 18)
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Specification