Liquid crystal projection panel having microlens arrays, on each side of the liquid crystal, with a focus beyond the liquid crystal

• US 5,398,125 A
• Filed: 11/10/1993
• Issued: 03/14/1995
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Aastuen, David J. W., Willett, Stephen J.
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): Parker, Kenneth
• Application Number:
  US08/150,215
• Time in Patent Office: 489 Days
• Field of Search: 359/40, 359/41, 359/42, 359/48, 359/49, 359/50, 359/82, 359/619, 359/621, 353/32, 353/30, 348/766, 348/790, 348/791, 348/761
• US Class Current: 349/95
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses

Abstract

A liquid crystal projection panel for use in a projection system. The projection panel is comprised of a large number of pixels of liquid crystal defining a image forming plane provided between two transparent substrates. Microlens arrays are provided on both sides of the projection panel. The microlenses in both arrays have focal lengths such that parallel light rays entering the microlenses at an angle perpendicular to the arrays are focused at points beyond the image forming plane of the display.

Claims

1. A pixellated display projection panel, comprising:

a pixellated display comprised of a plurality of pixels providing an image forming plane between two optically transparent substrates;

a first microlens array provided on one side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a first direction entering the microlenses at an angle perpendicular to the first array are focused at points beyond the image forming plane of the display; and

a second microlens array provided on the other side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a direction opposite said first direction entering the microlenses at an angle perpendicular to the second array are focused at points beyond the image forming plane of the display.

2. The projection panel of claim 1, wherein the pixellated display is a liquid crystal display.

3. The projection panel of claim 1, wherein the focal length of the microlenses in the first array is substantially equal to the focal length of the microlenses in the second array.

4. The projection panel of claim 1, wherein the focal points of the microlenses in the first array are located within one of the substrates, and the focal points of the microlenses in the second array are located within the other substrate.

5. A pixellated display projection system, comprising:

a pixellated display comprised of a plurality of pixels provided an image forming plane between two optically transparent substrates;

a first microlens array provided on one side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a first direction entering the microlenses at an angle perpendicular to the first array are focused at points beyond the image forming plane of the display;

a second microlens array provided on the other side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a direction opposite said first direction entering the microlenses at an angle perpendicular to the second array are focused at points beyond the image forming plane of the display;

a light source emitting light rays toward the display; and

means for projecting light rays exiting the second microlens array toward a viewing screen.

6. The projection system of claim 5, wherein the pixellated display is a liquid crystal display.

7. The projection system of claim 5, further comprising a first fresnel lens, provided between the light source and the first microlens array, for collimating the light rays, and a second fresnel lens, between the second microlens array and the projection lens, for converging the light rays.

8. The projection system of claim 5, wherein the focal length of the microlenses in the first array is substantially equal to the focal length of the microlenses in the second array.

9. The projection system of claim 5, wherein the focal points of the microlenses in the first array are located within one of the substrates, and the focal points of the microlenses in the second array are located within the other substrate.

10. A method of making a pixellated display projection panel, comprising:

providing a pixellated display comprised of a plurality of pixels providing an image forming plane between two optically transparent substrates, wherein the thicknesses of the substrates vary within a known range around an average value;

providing a first microlens array provided on one side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a first direction entering the microlenses at an angle perpendicular to the first array are focused at points beyond the image forming plane of the display;

providing a second microlens array provided on the other side of the display, the microlenses in the array corresponding to the pixels in the display, wherein the microlenses have focal lengths such that parallel light rays from a direction opposite said first direction entering the microlenses at an angle perpendicular to the second array are focused at points beyond the image forming plane of the display; and

selecting the optimum radius of curvature for the microlenses in the arrays based on the upper end of the range of thicknesses of the substrates.