Method and apparatus for distortion correction in optical projectors
First Claim
1. A method of projecting onto a screen an image having reduced distortion using a projector having an optical train that includes an image source, a field lens, and a projection lens, the image source and field lens having optical centers and the projection and field lenses having optical axes, the method comprising:
- offsetting the optical center of the image source from the optical axis of the projection lens to position the image;
orienting the field lens so that its optical axis is not parallel to that of the projection lens to reduce keystone distortion; and
positioning the optical center of the field lens on the optical axis of projection lens to reduce distortion, whereby the image is projected without keystoning or trapezoidal distortion.
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Accused Products
Abstract
A projector (100) including an liquid crystal display image source (120), a field lens (126), and a projection lens (128) projects a full-color image by projecting and converging images of multiple liquid crystal displays ("LCDs"). The image is properly positioned without keystoning by tilting the field lens and offsetting the center of the LCD image source from the optical axis (142) of the projection lens. Trapezoidal error is eliminated by maintaining the optical center (156) of the field lens on the optical axis of the projection lens. During focusing, a mounting apparatus (164) adjusts the offset (154) between the center of the LCD and the optical axis of the projection lens for proper convergence of the images and maintains the optical center of the field lens on the optical axis of the projection lens.
91 Citations
14 Claims
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1. A method of projecting onto a screen an image having reduced distortion using a projector having an optical train that includes an image source, a field lens, and a projection lens, the image source and field lens having optical centers and the projection and field lenses having optical axes, the method comprising:
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offsetting the optical center of the image source from the optical axis of the projection lens to position the image; orienting the field lens so that its optical axis is not parallel to that of the projection lens to reduce keystone distortion; and positioning the optical center of the field lens on the optical axis of projection lens to reduce distortion, whereby the image is projected without keystoning or trapezoidal distortion. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A projector capable of projecting a substantially distortion-free image onto a viewing screen, comprising:
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an image source having an optical center and providing an image to project; a field lens having an optical axis and optical center and concentrating light from the image source; and a projection lens having an optical axis, receiving light from the field lens, and projecting an image of the image source, wherein the optical center of the image source is offset from the optical axis of the projection lens, the optical axis of the field lens is not parallel to that of the projection lens, and the optical center of the field lens is positioned on the optical axis of the projection lens, thereby positioning the image on the viewing screen without distortion. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. In a multiple lens projection system having multiple projection lenses and a field lens and image source corresponding to each projection lens, a method of eliminating distortion, comprising:
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tilting at least one of the field lenses to eliminate keystone distortion; offsetting the center of at least one of the image sources from the optical axis of the projection lenses to position the image without introducing keystone distortion; and maintaining the optical centers of the field lenses on the optical axis of the projection lenses, thereby eliminating trapezoidal error.
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Specification