Hughes Aircraft Company

Hughes-jvc Technology Corporation

Ralph J Gagnon

Alan R Henderson

Robert T Carson

Roy A Cedarstrom

Color and/or polarization beam splitters are used in a multi-color light valve projection systems. The color and/or polarization beam splitters each include first and second prisms with a thin-film stack located therebetween. The prisms are made of glass which has an index of refraction between 1.65 and 1.85. The color and polarization beam splitters operate at an angle of incidence of 45 degrees. By operating at 45 degrees, the color and/or polarization beam splitters can be assembled in a compact and parallel manner and thereby reduce the size of the color and/or polarization beam splitter while increasing the contrast of the light valve projection system. The high index of refraction glass also produces a smaller optical path for a given physical path. The disadvantages associated with index of refraction oil prisms are also eliminated.

Parallel plate beam splitter configuration in high index glass

An LCLV projection system (10) includes color separation dichroic mirrors (50, 52) positioned between a group of reflective liquid crystal light valves (38, 40, 42) and a polarizer analyzer (26) which enables a single projection lens (34) to project all colors via a light beam of single linear polarization with a high degree of contrast, efficiency and color separation. The polarizer analyzer (26) directs a light beam with a single polarization state to a pair of dichroic filters (50, 52) which separate the beam into three different colors that are sent to three different reflective liquid crystal light valves (38, 40, 42). The light valves reflect the respective colored light beams with change in polarization state back to the dichroic mirrors (50, 52) which combine the three colors into a single combined multi-color beam that is fed through the polarizer analyzer (26) to a single system projection lens (34). The polarizer analyzer (26) and dichroic mirrors (50, 52) are enclosed in a fluid filled enclosure (28) containing an optical fluid which has an index of refraction substantially the same as that of the substrate of the dichroic mirrors (50, 52), for effectively increasing the back focal length of the projection lens (34).

Immersed dichroic system for single projection lens liquid crystal video

A two lens optical system for a three primary color liquid crystal light valve image projection system. The first lens projects the red and green primary colors, while the other lens projects the blue primary color. The light from the illumination system is partially prepolarized by a first prism before being split into two optical paths by a first beam splitter. Red light having a first and second polarization and green light having a first polarization is transmitted along a first optical path to a second, or main beam splitter, from the first beam splitter. The red light is transmitted to a first light valve, the green light being reflected to a second light valve. With the first and second light valves 'on' state, the light incident thereon is directed back to the main beam splitter, recombined and then directed to the first projection lens. Green and blue light of the second polarization is reflected along a second optical path by the first beam splitter, the blue color light being transmitted through a third beam splitter to a third light input valve. The third light valve 'on' state, the blue light incident thereon is directed to the third beam splitter and then to the second projection lens. By utilizing the two different optical paths, high image contrast is achieved. The optical system utilizes a minimum of optical components such that light losses in the system are reduced, thus increasing overall system collection efficiency.

Optical system for three color liquid crystal light valve image

The invention provides a two-channel liquid crystal light valve image projection system with prepolarization using an oil coupled optical arrangement. A prepolarizing beam splitter is mounted the container in optical alignment with a first surface for splitting and prepolarizing light from a source into first and second beams having first and second polarization states respectively. First and second dichroic separators are mounted within the container for extracting light of a first color from the first beam and light of a second color from the second beam respectively. The separator outputs are recombined by the prepolarizing prism into a single beam which is directed to a second polarizing beam splitter mounted within the container. The second beam splitter splits the single beam and directs light of the first and second polarizations through the second and third apertures, respectively. Liquid crystal light valves mounted at the second and third apertures modulate the polarization state of the exiting light and return it to the second beam splitter to be directed through the output aperture to projection optics for display.

High efficiency optical tank for two-color liquid crystal light valve

An optical arrangement is disclosed which provides color selective prepolarization of the light incident upon two or more light valves. This is accomplished by the use of a prepolarizing prism which acts on light from a light source to direct light of a first polarization to a first dichroic separator and light of a second polarization to a second dichroic separator. Each separator transmits an output beam having substantially a single color and a single polarization state. The two resulting beams are recombined by a dichroic adder prior to being applied to a second polarizing prism. The second polarizing prism directs light of a first color and polarization to a first light valve and light a second color and polarization to a second light valve. The result is that one light valve sees light of a first color and a first polarization and the other light valve sees light of a second color and second polarization. Each light valve modulates the polarization state of incident light in accordance with the input or writing light. Where the writing light is present, the polarization state is changed from the first to the second or vice versa depending upon the light valve. The output of each light valve is applied to a second or main polarizing prism which converts the modulations of polarization into modulations of brightness. The output of the main polarizing prism is then applied to a projection lens in a conventional manner.

Two color liquid crystal light valve image projection system with single

An optical system is disclosed which incorporates a color selective prepolarizer to improve contrast and reduce stress induced birefringence while allowing a blue mirror to be used to enhance the projected image. The invention includes a source lamp for providing a first beam of unpolarized white light energy; a prepolarizing beam splitter which extracts from the first beam, second and third beams. The second beam contains undesirable color components of a first polarization state, which are removed from the system by reflection to an optical dump. The third beam includes prepolarized light of one color and the first polarization and white light of the second polarization. A main polarizing prism is provided for splitting the third beam into fourth and fifth beams having the first and second polarizing states respectively. The main prism effectively directs the white light to the light valve where it is modulated and returned to the main prism for projection in the conventional manner. The fifth beam being monochromatic and of the first polarization state is directed to the blue mirror where it is filtered to remove residual red and green components, altered in polarization state from the first state to the second state and altered in intensity by a preselected gradient operator before being returned to the main prism for superimposition on the light valve image. The invention includes projection optics for displaying the composite image.

Liquid crystal light valve image projection system with color selective

This invention provides a unitary oil coupled optical arrangement for color selective prepolarization of the light incident upon two light valves. The optical arrangement is immersed within a single tank. It includes dichroic filters which act on polarized light from a light source which has been polarized into two beams by passing through and being reflected from a prepolarizing optical thin film stack. The first dichroic filter provides light of a first color and a first polarization while the second dichroic filter provides light of a second color and a second polarization. The light from each of the filters is then combined into a single beam by a thin film polarization-selective beam combiner prior to being applied to the main polarizing prism. The main prism then passes light of a first polarization and a first color to a first light valve and light of the second polarization and a second color to the second light valve in a conventional manner. Each light valve operates on the light in accordance with the presence of the writing light input from a cathode ray tube. The output of each light valve and is then applied to projection lens by the main polarizing prism.

Two-color liquid crystal light valve image projection system with color

A first color selective beam splitter is provided for splitting light from a source into first and second beams, the first beam being blue and the second beam having red and green color components. A second beam splitter is provided for directing light of the first beam to a blue liquid crystal light valve. The light valve modulates the polarization of the light in the first beam and returns it to the second beam splitter which converts the modulations of polarization to modulations of intensity in the conventional manner and reflects it to a first projection lens. A third beam splitter is provided for splitting the second beam into third and fourth beams having first and second polarization states, respectively. The third beam is reflected to a red filter. The fourth beam is transmitted through a green filter. The output of each filter is a substantially monochromatic beam of a single polarization state. The filter outputs are recombined into a single beam which illuminates a fourth beam splitter. The fourth beam splitter is a main polarizing prism. It reflects light of the first polarization state to the green light valve and transmits light of the second polarization state to the red light valve. The light valves modulate the polarization state of incident light in the conventional manner and return it to the main prism. The main prism recombines the light from the first and second light valves into a single beam which is directed to a second projection lens.

High efficiency optical tank for three color liquid crystal light valve

A full color high contrast image projection system with oil coupled dichroics and a single projection lens is disclosed. The invention includes a unitary optical tank in which a prepolarizer and dichroic separators are mounted in fixed alignment relative to a main polarizing prism. The prepolarizer acts on the incident light from a source to polarize the green light and reflect the S component out of the system. The red and blue components are transmitted unchanged. The main polarizer is mounted at a 90.degree. twist relative to the prepolarizer so that it reflects the green light to a first light valve via a first dichroic separator. The polarized red and blue components are transmitted to second and third light valves via a second dichroic separator. The light valves modulate the polarization state of incident light before returning it to the second beamsplitter. The second beamsplitter then recombines the individual beams into a single output beam. This beam is projected by a telecentric projection lens to provide a full color high contrast image.

Growing community of inventors

Chico, CA, United States of America

Ralph J Gagnon