Optical: systems and elements – Single channel simultaneously to or from plural channels
Reexamination Certificate
2000-05-17
2001-11-27
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
C359S722000, C348S743000, C348S742000
Reexamination Certificate
active
06324006
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of display systems, more particularly to display systems using sequential color techniques such as color wheels.
BACKGROUND OF THE INVENTION
Modern display systems typically create full-color projected images by projecting three single-color images. The eye of the viewer integrates these single-color images to give the perception of a single, full-color image. Three separate modulators or controllable light sources are often used simultaneously to generate the primary-color images. For example, three liquid crystal display (LCD) panels or digital micromirror device (DMD) arrays and appropriate dichroic filters create three primary-color images using a single light source, or three cathode ray tubes perform both the modulator and light source functions to create three primary-color images.
Alternatively, a single modulator is used with a sequential color light source to sequentially create three primary-color images. If the light source sequences through the primary colors fast enough, the viewer will not see the sequential single-color images but instead will see a single full-color image. A sequential color light source is formed by combining a white-light source with a filtering means such as a color wheel.
A color wheel typically is a disk-shaped assembly of dichroic filters. Other shapes of “color wheels” are possible, such as rotating drums or polygons. The white-light beam is focused on the color wheel and the dichroic filters, which are either transmissive or reflective, filter the white light to form a primary-color light beam. The color wheel includes at least one filter for each of the primary colors.
Spinning the color wheel so that each filter passes through the point at which the white light beam strikes the color wheel generates a sequential primary color light beam. The color wheel typically is spun fast enough to create at least one primary color period for each primary during each frame of a video image. Spinning the wheel faster, or using multiple filter segments for one or more of the primary colors can reduce color separation artifacts that allow the viewer to detect the sequential color nature of the display system.
While a sequential color display system typically costs less to produce than a simultaneous color display system, images created by a sequential filtered color display system are not as bright as images created by simultaneous color display systems using the same light source. This is because at any given time only a portion of the light generated by the light source is being used to form the image. For example, when using a three-color equal-segment filter wheel, each primary color is produced only ⅓ of the time. Additionally, when a sequential filter such as a color wheel is used, the light during the filter transitions, typically called spoke times, will be a varying mixture of the two filters being changed in and out. This mixed-color light is not used since using the mixed color light would adversely affect the color purity of the created image.
High image brightness is one of the major desires of customers in the projection display market. Therefore, a method and system for increasing the brightness of a projected image is needed.
SUMMARY OF THE INVENTION
Objects and advantages will be obvious, and will in part appear hereinafter and will be accomplished by the present invention which provides a method and system for using spoke light, that is light generated during color filter transitions, to increase the brightness of an image. One embodiment of the claimed invention provides a method of producing an image. The method comprising the steps of. providing a sequential color beam of light, the sequential color beam of light changing color during each frame period, each frame period comprising: at least two primary color periods; and at least one spoke period during which the sequential color beam of light changes color, modulating the sequential color beam of light during the primary color periods with primary color intensity data, modulating the sequential color beam of light during at least one spoke period with combined-color intensity data, and focusing the modulated sequential color beam of light on an image plane to form a multi-color image.
According to another embodiment of the present invention a display system is provided. The display system comprising: a sequential color light source operable to provide a sequential color beam of light along a light path, the sequential color beam of light having at least two periods of primary color light each frame period and at least one spoke period during which the sequential color beam of light changes color, a modulator disposed on the light path and operable to modulate the sequential color beam of light in response to image data received by the modulator, and a controller operable to receive input intensity data and process the input intensity data to yield primary color output intensity data and combined color output intensity data, the controller transmitting the primary color output intensity data and the combined color output intensity data to the modulator such that the modulator modulates the sequential color beam of light with the primary color output intensity data during the periods of primary color light and with the combined color output intensity data during at least one spoke period.
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Brady III Wade James
Brill Charles A.
Epps Georgia
Seyrafi Saeed
Telecky , Jr. Frederick J.
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