Patent Application
20070091285
This invention relates to optical engines for displays, including rear projection televisions.
U.S. Pat. No. 6,857,752 discloses various optical engines. Particularly,
In one embodiment of the invention, an optical engine includes adjustable optical components that provide rapid and accurate alignment of color lights to imagers. A light pipe homogenizes light from a light source, a focusing lens focuses the homogenized light, a first dichroic mirror passes a first color light and reflects second and third color lights from the focused light, a turning mirror turns the second and the third color lights, and a second dichroic mirror passes the second color light and reflects the third color light. The imagers reflect the color lights to form color images that combine to form a projected image.
In one embodiment, the light pipe is translatable along a first direction to match the focal point of the light source. The focusing lens is translatable along second and third directions to match the first color light to a first imager. The turning mirror is (1) translatable along the first, the second, and the third directions, and (2) rotatable about the first and the second directions, to match the second color light to a second imager. The second dichroic mirror is rotatable about the third direction to match the third color light to a third imager.
Use of the same reference numbers in different figures indicates similar or identical elements.
Optical engine 100 includes a UHP (ultra-high performance) lamp 102 that generates white light. Lamp 102 includes an elliptical reflector that focuses the white light to the input end of a light pipe 104. Note that other light sources may be used in place of lamp 102, and other light integrators may be used in place of light pipe 104.
Light pipe 104 homogenizes the intensity of the white light. Uniform white light exits generally along the positive X-direction from the output end of light pipe 104. In one embodiment, light pipe 104 is made of glass and has a rectangular cross-section to generate either a rectangular white light having the aspect ratio of the display (e.g., 16:9 or 4:3). To accommodate variations in each lamp 102, the location of light pipe 104 along the X-direction can be adjusted to align the input end of light pipe 104 to the focal point of lamp 102.
Referring to
Referring back to
A focusing lens 108 receives the s-polarized white light from polarizer 106 and focuses the white light generally along the positive X-direction. Focusing lens 108 may be an aspheric lens. To accommodate variations in the components of engine 100, the location of focusing lens 108 along the Y and the Z-directions can be adjusted to align a red color light to an imager 124.
Referring to
Referring back to
Following the path of the red light, a pair of relay lenses 112 and 114 passes the red light generally along the positive X-direction to an input face 116 of a polarizing beam splitter (PBS) 118 (only visible in
A liquid crystal on silicon (LCOS) imager 124 is located opposite of imager face 122 to receive the s-polarized red light. In one embodiment, LCOS imager 124 is mounted on imager face 122. LCOS image 124 reflects the s-polarized red light and modulates part of the s-polarized red light to generate a red image having p-polarized red light. The red image travels in the positive Z-direction back towards PBS 118. Polarizing surface 120 of PBS 118 passes the red image having the p-polarized red light to an input face 126 (only visible in
Referring back to the path of the blue and green lights, a turning mirror 130 reflects the blue and green lights generally along the positive X-direction. To accommodate variations in the components of engine 100, the location of turning mirror 130 along the X, Y, and Z-directions, and the angle of turning mirror 130 about the X and the Y-directions, can be adjusted to align the blue color light to an imager 144.
Referring to
Referring back to
A dichroic mirror 134 receives the blue and the green lights from relay lens 132. In one embodiment, dichroic mirror 134 passes the blue light and reflects the green light. Oriented about 45 degrees to the X and Y plane, dichroic mirror 134 passes the blue light generally along the positive X-direction and reflects the green light generally along the negative Z-direction. To accommodate variations in the components of engine 100, the angle of dichroic mirror 134 about the Y-direction can be adjusted to align the green color light to an imager 156. Note that other color separators may be used in place of dichroic mirror 134.
Referring to
Referring back to
A LCOS imager 144 is located opposite of imager face 142 to receive the s-polarized blue light. In one embodiment, LCOS imager 144 is mounted on imager face 142. LCOS image 144 reflects the s-polarized blue light and modulates part of the s-polarized blue light to generate a blue image having p-polarized red light. The blue image travels in the negative Z-direction back towards PBS 136. Polarizing surface 140 of PBS 136 passes the blue image having the p-polarized blue light to an input face 146 of color combiner 128. In one embodiment, PBS 136 is mounted on input face 146. Note that other types of imagers may be used in place of LCOS imager 144.
Following the path of the green light, a PBS 148 receives the green light at an input face 150. PBS 148 has a polarizing surface 152 that reflects the s-polarized green light generally along the negative X-direction through an imager face 154.
A LCOS imager 156 is located opposite of imager face 154 to receive the s-polarized green light. In one embodiment, LCOS imager 156 is mounted on imager face 154. LCOS image 156 reflects the s-polarized green light and modulates part of the s-polarized green light to generate a green image having p-polarized green light. The green image travels in the positive X-direction back towards PBS 148. Polarizing surface 152 of PBS 148 passes the green image having the p-polarized green light to an input face 160 of color combiner 128. In one embodiment, PBS 148 is mounted on input face 160. Note that other types of imagers may be used in place of LCOS imager 156.
Color combiner 128 has a dichroic coating on a diagonal face 162 that reflects red light and passes blue and green lights, and a dichroic coating on a diagonal face 164 that reflects blue light and passes red and green lights. The red image from imager 124 reflects from diagonal face 162 and leaves through an exit face 166. The blue image from imager 144 reflects from diagonal face 164 and leaves through exit face 166. The green image from imager 156 passes through diagonal faces 162 and 164 and leaves through exit face 166. At exit face 166, the red, green, and blue images merge to form a single image with the appropriate colors. The single image then travels from color combiner 128 to a projection lens 168. Note that other color combiners may be used in place of X-cube color combiner 128. In one embodiment, PBS 118, PBS 136, PBS 148, and X-cube color combiner 128 are the Vikuiti Optical Core from 3M Optical System Division of St. Paul, Minn.
In step 602, imagers 124, 144, and 156 are connected to a pattern generator to project a white image on the screen and light source 102 is powered up.
In step 604, the signals for blue imager 144 and green imager 156 are turned off and the location of light pipe 104 is adjusted along the X-direction to project a uniform and bright red image with sharp edges on the screen (i.e., to focus the red image). In one embodiment, the uniformity and brightness of the red image is measured by a light meter at 9 or 13 different points.
In step 605, the location of focusing lens 108 is adjusted along the Y and the Z-directions to move the red image to a specified area defined by the shadow mask of the resulting display.
In step 606, the signal for red imager 124 is turned off and the signal for green imager 156 is turned on to project a green image on the screen. Turning mirror 130 is adjusted along the X, Y, and Z-directions and about the X and Y-directions to (1) project a uniform and bright green image with sharp edges on the screen (i.e., to focus the green image), and (2) place the green image to the specified area defined by the shadow mask of the resulting display (i.e., to provide a rectangular shape into the specified area). In one embodiment, the uniformity and brightness of the green image is measured by a light meter at 9 or 13 different points.
In step 608, the signal for blue imager 144 is turned on to project a blue image on the screen along with the green image. Any misalignment between the blue and the green images appears visually as a blue light and a green light at the top and the bottom of the combined image, or vice versa. Dichroic mirror 134 is adjusted about the Y-direction until the blue and the green images are aligned. Note that the uniformity and brightness of the blue image are not measured because they should be the same as the uniformity and brightness of the green image, which were adjusted with turning mirror 130 in step 606.
In step 610, the signal for red imager 124 is turned on to project the red image on the screen along with the green and the blue images. At this point, one of three types of misalignment occurs. In a first type of misalignment, a cyan light (a mixture of green and blue lights) appears at two of the edges of a white image. Focusing lens 108 is adjusted along the Y and the Z-directions until a fully white image appears. In a second type of misalignment, a magenta light (a mixture of red and blue lights) appears around the edges of a white image. Turning mirror 130 is adjusted along the Z-direction until a fully white image appears. In a third type of misalignment, a cyan light appears around the edges of a white image. Light pipe 104 is adjusted along the X-direction until a fully white image appears.
In step 612, it is determined if the red, the green, and the blue images are aligned within an acceptable tolerance. If the red, the green, and the blue images are not aligned within the acceptable tolerance, then method 600 loops back to any of the above steps from step 604 to 610 to further adjust the alignment of the components. From experience, only further adjustments to turning mirror 130 and focusing lens 108 are needed to align the images within the acceptable tolerance. Step 612 is followed by step 614 if the images are aligned within the acceptable tolerance.
In step 614, the locations and positions of light pipe 104, focusing lens 108, turning mirror 130, and dichroic mirror 134 are fixed.
Various other adaptations and combinations of features of the embodiments disclosed are within the scope of the invention. Numerous embodiments are encompassed by the following claims.
