Asymmetrical switching delay compensation in display systems
First Claim
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1. A method of operating an array of pixels to generate an image using a pulse-width-modulation (PWM) technique, wherein each pixel has an asymmetric switching delay between an ON and OFF state, the method comprising:
- assigning a set of nominal weights to a set of bits corresponding to the PWM pattern of a pixel;
providing a desired intensity value to be reproduced by the pixel;
determining the values of a first subset of bits according to the desired intensity such that the bits in the first set collectively present an intensity that approximates the desired intensity value;
determining a residual intensity value based on the desired intensity value, the determined values of the first subset of bits and their corresponding nominal weights, and a parameter that characterizes the asymmetry of the pixel switching delay;
determining the values of a second subset of bits depending on the residual intensity value, the parameter characterizing the asymmetry of the switching delay, the values and weights of the first subset of bits, and a dither threshold value; and
operating the pixels with the PWM technique according to the determined bit values of the first and second subsets.
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Abstract
A method and apparatus of the present invention is particularly for use in display systems having spatial light modulators in which the pixels present asymmetrical switching delays. For a desired illumination intensity of a pixel, a series of pulse-width-modulation bit values for the pixel is determined based at least in part upon a parameter that characterizes the asymmetrical transition behavior of the pixel between states.
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Citations
57 Claims
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1. A method of operating an array of pixels to generate an image using a pulse-width-modulation (PWM) technique, wherein each pixel has an asymmetric switching delay between an ON and OFF state, the method comprising:
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assigning a set of nominal weights to a set of bits corresponding to the PWM pattern of a pixel; providing a desired intensity value to be reproduced by the pixel; determining the values of a first subset of bits according to the desired intensity such that the bits in the first set collectively present an intensity that approximates the desired intensity value; determining a residual intensity value based on the desired intensity value, the determined values of the first subset of bits and their corresponding nominal weights, and a parameter that characterizes the asymmetry of the pixel switching delay; determining the values of a second subset of bits depending on the residual intensity value, the parameter characterizing the asymmetry of the switching delay, the values and weights of the first subset of bits, and a dither threshold value; and operating the pixels with the PWM technique according to the determined bit values of the first and second subsets. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A device for controlling the operation of an array of pixels to generate an image using a pulse-width-modulation (PWM) technique, wherein each pixel has an asymmetric switching delay between an ON and OFF state, the device comprising:
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a set of data bits corresponding to a PWM pattern of a pixel with the data bits assigned with a set of nominal weights; a means for determining a value for each bit of a first subset of the data bits according to a desired intensity such that the bits in the first subset collectively present an intensity that approximates the desired intensity value; a means for determining a residual intensity value based on the desired intensity value, the determined values of the first subset of bits and their corresponding nominal weights, and a parameter that characterizes the asymmetry of the pixel switching delay; a means for determining the values of a second subset of bits depending on the residual intensity value, the parameter characterizing the asymmetry of the switching delay, the values and weights of the first subset of bits, and a dither threshold value; and a means for operating the pixels with the PWM technique according to the determined bit values of the first and second subsets. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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35. A projection system for displaying an image using a pulse-width-modulation (PWM) technique, the device comprising:
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an illumination system providing light for the system; an array of pixels, each of which operates between an ON state and an OFF state for modulating light from the light source into different spatial directions, and wherein each pixel has an asymmetrical switching delay between an ON state and an OFF state; a controller that controls an operation of the pixel array and the illumination system, further comprising; a set of data bits corresponding to a PWM pattern of a pixel with the data bits assigned with a set of nominal weights; a means for determining a value for each bit of a first subset of the data bits according to a desired intensity such that the bits in the first subset collectively present an intensity that approximates the desired intensity value; a means for determining a residual intensity value based on the desired intensity value, the determined values of the first subset of bits and their corresponding nominal weights, and a parameter that characterizes the asymmetry of the pixel switching delay; a means for determining the values of a second subset of bits depending on the residual intensity value, the parameter characterizing the asymmetry of the switching delay, the values and weights of the first subset of bits, and a dither threshold value; and a means for operating the pixels with the PWM technique according to the determined bit values of the first and second subsets; and a projection lens for collecting the modulated light and projecting the modulated light onto a display target. - View Dependent Claims (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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Specification