LCD with integral light confinement having a pair of afocal lenslets positioned between liquid crystal cells and color polarizers

• US 5,574,580 A
• Filed: 12/12/1995
• Issued: 11/12/1996
• Est. Priority Date: 10/01/1993
• Status: Expired due to Term

• Current Assignee: Raytheon Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Ansley, David A.
• Primary Examiner(s): Gross, Anita Pellman
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/570,807
• Time in Patent Office: 336 Days
• Field of Search: 359/40, 359/53, 359/64, 359/41, 359/42
• US Class Current: 349/5
• CPC Class Codes: G02B 3/0006 Arrays G02B3/02, G02B5/188 take precedence
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence

Abstract

Telecentric afocal microlens combinations are inserted between the liquid crystal cells of an active matrix liquid crystal subtractive color display to retain light within a projection of each liquid crystal pixel as the light propagates through the system. A resulting reduction in light losses at the edge of each pixel significantly improves the output brightness and resolution.

Claims

1. An active matrix liquid crystal subtractive color display, comprising:

a light source,

a linear polarizer positioned to linearly polarize light from said light source,

at least three color polarizers positioned successively in a path of polarized light from said linear polarizer,

at least three active matrix liquid crystal cells positioned respectively between said linear polarizer and the first of said color polarizers in said light path, and between each pair of successive color polarizers, said liquid crystal cells being organized into aligned arrays of independently programmable pixels for rotating the polarization of incident light by programmed amounts, said pixels occupying predetermined areas, and

respective optical confiners positioned between each pair of successive liquid crystal cells, said linear and color polarizers and said liquid crystal cells being aligned along an optical axis, each of said optical confiners comprising a respective pair of afocal lenslets, the lenslets of each pair having substantially equal focal lengths and being positioned substantially one focal length from the nearest color polarizer and the nearest liquid crystal cell, said lenslets collectively substantially confining the transmission of light between said cells to pixel projections which do not exceed the areas of said cell pixels so that a collimated beam incident on said linear polarizer along said optical axis emerges as a telecentric collimated beam from the last of said liquid crystal cells in said light patch.

2. The subtractive color display of claim 1, further comprising an image surface on the opposite side of said liquid crystal cells from said light source, and an additional optical confiner positioned between said image surface and its nearest liquid crystal cell, said additional optical confiner substantially confining the transmission of light between said nearest liquid crystal cell and said image surface to said projections of said cell pixels.

3. The subtractive color display of claim 1, each lenslet pair encompassing a respective pixel projection.

4. A subtractive color display, comprising:

a light source,

a linear polarizer positioned to linearly polarize light from said light source,

at least three color polarizers positioned successively in the path of polarized light from said linear polarizer,

at least three pixelizod polarization rotation arrays positioned respectively between said linear polarizer and the first of said color polarizers in said light path, and between each pair of successive color polarizers, said polarization rotation arrays including mutually aligned arrays of independently programmable polarization rotation pixels for rotating the polarization of incident light from said light source by programmed amounts, and

a respective pair of telecentric afocal lenslet arrays positioned between each pair of successive polarization rotation arrays, the lenslets of each array being substantially aligned with and substantially equal in size and focal length to corresponding lenslets in the other arrays along respective optical axes that also extend through said linear polarizer, said color polarizers and respective polarization rotation pixels in each of said polarization rotation arrays, with successive lenslet arrays spaced from each other by approximately two focal lengths, and the lenslet arrays of each pair oriented to inhibit light from said light source from spreading between said polarization rotation arrays substantially beyond the limits of said polarization rotation pixels so that a collimated beam incident on said linear polarizer along one of said optical axes emerges as a telecentric collimated beam from the last of said polarization rotation arrays in said light path.

5. The subtractive color display of claim 4, said pixelized polarization rotation arrays comprising respective active matrix liquid crystal cells.

6. The subtractive color display of claim 4, further comprising an image surface on the opposite side of said polarization rotation arrays from said light source, and an additional pair of afocal lenslet arrays positioned between said image surface and its nearest polarization rotation array, said additional pair of afocal lenslet arrays preventing light from said light source from spreading between said image surface and said nearest polarization rotation array substantially beyond the limits of said polarization rotation pixels.

7. A subtractive color display, comprising:

a linear polarizer positioned to receive and linearly polarize light from a source location,

at least three color polarizers positioned successively in the path of polarized light from said linear polarizer,

at least three pixelized polarization rotation arrays positioned respectively between said linear polarizer and the first of said color polarizers in said light path, and between each pair of successive color polarizers, said polarization rotation arrays including mutually aligned arrays of independently programmable polarization rotation pixels for rotating the polarization of incident light from said linear polarizer by programmed amounts, said pixels occupying predetermined areas, and

respective optical confiners positioned between each pair of successive polarization rotation arrays, said linear and color polarizers and the aligned polarization rotation pixels of said polarization rotation arrays being aligned along respective optical axes, each of said optical confiners comprising a respective array of afocal lenslet pairs, the lenslets of said lenslet pairs having substantially equal focal lengths and being positioned substantially two focal lengths form each other, said lenslets substantially confining the transmission of light between said polarization rotation arrays to pixel protections which do not exceed the area of said pixels so that a collimated beam incident on said linear polarizer along one of said optical axes emerges as a telecentric collimated beam from the last of said polarization rotation arrays in said light path.

8. The subtractive color display of claim 7, said pixelized polarization rotation arrays comprising respective active matrix liquid crystal cells.

9. The subtractive color display of claim 7, further comprising an image surface on the opposite side of said polarization rotation arrays from said linear polarizer, and an additional optical confiner positioned between said image surface and its nearest polarization rotation array, said additional optical confiner substantially confining the transmission of light between said nearest polarization rotation array and said image surface to projections of said polarization rotation pixels.

10. The subtractive color display of claim 7, each lenslet pair encompassing a respective pixel projection.