Projection method and system utilizing a variable transmittance color switch
First Claim
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1. A single polarizer projector system, designed for displaying color image on a display panel by switching the color to be displayed by a color switch, comprising:
- an image processing circuit for processing a video signal, input into the system, into an appropriate format suitable for said display panel;
a mean luminance calculation circuit for converting R, G and B signals, outputted from said image processing circuit, into a luminance (Y) signal from which can be calculated a mean luminance during a 1V period;
a transmittance setter for setting a transmittance of said color switch according to an output from said mean luminance calculation circuit;
a color switch drive circuit for driving said color switch according to said output from said transmittance setter; and
a panel drive circuit for sending the inputted video signal to said display panel and a synchronizing trigger signal to said color switch drive circuit.
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Abstract
A single polarizer projector with a color switch and a projection method thereof, wherein the mean luminance of the inputted video signal is calculated so that the transmittance of the color switch can be controlled by the mean luminance in such a fashion that the transmittance is set to a maximum (100%) while setting the same to a low level (50%), thereby preventing unnatural blackening of relatively dark image for improving the contrast ratio.
31 Citations
16 Claims
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1. A single polarizer projector system, designed for displaying color image on a display panel by switching the color to be displayed by a color switch, comprising:
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an image processing circuit for processing a video signal, input into the system, into an appropriate format suitable for said display panel;
a mean luminance calculation circuit for converting R, G and B signals, outputted from said image processing circuit, into a luminance (Y) signal from which can be calculated a mean luminance during a 1V period;
a transmittance setter for setting a transmittance of said color switch according to an output from said mean luminance calculation circuit;
a color switch drive circuit for driving said color switch according to said output from said transmittance setter; and
a panel drive circuit for sending the inputted video signal to said display panel and a synchronizing trigger signal to said color switch drive circuit. - View Dependent Claims (2, 3, 4, 5, 6)
a first optical path for enabling light from a light source unit to reach said display panel through a first polarizer, said color switch, a second polarizer and a polarization beam splitter prism; and
a second optical path for enabling the light reflected by said display panel to reach a screen through said polarization beam splitter prism, wherein the light produced by said light source unit is made to pass through said first polarizer so as to be substantially reduced to only an S wave component, whereupon said S wave component is converted into a color to be displayed by said color switch, said colored light, which comprises both a P wave component and a S wave component, is made to pass through said second polarizer to remove the S wave component, thereby allowing only the P wave component to reach said display panel, leading to an improved contrast ratio of the image.
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5. The projector system defined in claim 1, further comprising:
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a first optical path for enabling light from a light source unit to reach said display panel through a first polarizer, said color switch and a polarization beam splitter prism;
a second optical path for enabling the light reflected by said display panel to reach said screen through said polarization beam splitter prism and a second polarizer;
wherein the light produced by said light source unit is passed through said first polarizer to be substantially reduced to an S wave component, whereupon the S wave component is passed through said color switch and then through said polarization beam splitting prism to the display panel, and whereupon the light reflected by said display panel and polarized by said polarization beam splitting prism in order to be projected on the screen is polarized by said third polarizer to remove any P wave component included in the light reflected by said display panel, thereby improving the contrast ratio.
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6. The projector system defined in claim 5, wherein an absorption polarizer having a high polarizing efficiency is employed as said second polarizer.
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7. A method of displaying an image using a projection display system, comprising the steps of:
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inputting a video signal into said projection display system;
projecting a multi-spectrum beam of light onto a color switch;
selectively allowing a limited-spectrum of light derived from said multi-spectrum beam of light to pass through said color switch and project onto a reflective display panel;
synchronizing control of said reflective display panel with said color switch so that an image displayed by said reflective display panel corresponds to said limited-spectrum of light passed through said color switch;
calculating a mean luminance of said video signal based on R, G and B components of said video signal; and
selectively adjusting a transmittance of said color switch based on said calculated mean luminance of said video signal input into said projection display system. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification