Three-dimensional integral imaging and display system using variable focal ...

THREE-DIMENSIONAL INTEGRAL IMAGING AND DISPLAY SYSTEM USING VARIABLE FOCAL LENGTH LENS

REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of, and claims priority to U.S. patent application Ser. No. 10/778, 281 (Docket No. 1802.01), filed Feb. 13, 2004, U.S. patent application Ser. No. 10/822,414 (Docket No. 1802.04), filed Apr. 12, 2004, U.S. patent application Ser. No. 10/855,554 (Docket No. 1802.05), filed May 27, 2004, U.S. patent application Ser. No. 10/855,715 (Docket No. 1802.06), filed May 27, 2004, U.S. patent application Ser. No. 10/855,287 (Docket No. 1802.07), filed May 27, 2004, U.S. patent application Ser. No. 10/857,796 (Docket No. 1802.08), filed May 28, 2004, U.S. patent application Ser. No. 10/857,714 (Docket No. 1802.09), filed May 28, 2004, U.S. patent application Ser. No. 10/857,280 (Docket No. 1802.10), filed May 28, 2004, U.S. patent application Ser. No. 10/872,241 (Docket No. 1802.11), filed Jun. 18, 2004, U.S. patent application Ser. No. 10/893,039 (Docket No. 1802.12), filed Jul. 16, 2004, all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to optical systems in general and more specifically to three-dimensional imaging and display systems.

BACKGROUND OF THE INVENTION

[0003] Three-dimensional (3-D) imaging and display using two-dimensional (2-D) display devices has been attempted using various techniques. Stereoscopic techniques can display large images with high resolution. However, stereoscopic techniques typically require that the viewer wear special glasses to have a 3-D visual effect. Furthermore, stereoscopic techniques provide viewers with only horizontal parallax and a limited number of viewpoints. Additionally, viewers using stereoscopic glasses may suffer visual fatigue due to convergence-accommodation conflict.

[0004] Holography has also been used for 3-D displays. Using this technique, true 3-D images with full parallax and continuous viewing points may be produced using diffraction gratings. However, to obtain a proper grating, coherent light is needed when the hologram is recorded. Alternatively, computer-generated holograms can be made, but this approach requires lengthy computation time. Therefore, it is difficult to obtain large, color, 3-D displays using holography.

[0005] Integral imaging, or real-time integral photography, displays 3-D images in space by crossing incoherent light rays from 2-D elemental images, using a lenslet array. Like holography, integral imaging produces true 3-D images with full parallax and continuous viewing points. However, because lenslet arrays are used, the viewing angle, depth of focus, and resolution of the 3-D images is limited. Additionally, 3-D images produced in direct pick-up integral imaging are pseudoscopic (reversed-depth) images.

[0006] FIG. 1 depicts one embodiment of a prior art integral imaging and display system 100. The system 100 includes an imaging system 145 and a display system 175.

The imaging system 145 includes a lens array 110 and an imaging sensor 120. The lens array 110 focuses images of an object 140 onto the image sensor 120, producing elemental images. The display system 175 includes a display panel 150 and a lens array 160. The display panel 150 generates 2-D elemental images 170 that are focused by the lens array 160 into a reconstructed 3-D image 170.

[0007] FIG. 2 depicts an embodiment of a prior art display system 175 to increase the depth range of the 3D image 170. As shown in FIG. 2, to increase the depth range requires macromovement of the lens array 160.

[0008] FIG. 3 depicts an embodiment of a prior art display system 200, that uses a concave mirror array 190 instead of a lens array.

[0009] A similar approach to that found in FIG. 3 uses a micro-convex mirror array. This technique is described in "Three-dimensional projection integral imaging using micro-convex mirror arrays" by Ju-Seog Jang and Bahram Javidi. Use of micro-convex mirror arrays may increase the viewing angle, because the micro-convex mirrors can be produced with a small f number (the ratio of the focal length of the lens to its effective aperture) with negligible aberration. Furthermore, when elemental images obtained from direct camera pickup with a 2-D image sensor and a lenslet array, 3-D orthoscopic virtual images are displayed. Flipping-free viewing of 3-D images is thus possible, even if optical barriers are not used, because each elemental image is projected only onto its corresponding micro-convex mirror. However, this technique using a micro-convex mirror array allows for only limited depth of focus for displayed 3-D images. The limitation to the depth of focus in turn limits the depth range of the displayed image.

[0010] Therefore, what is needed is an integral imaging and display system that provides improved depth range for 3-D images.

SUMMARY OF INVENTION

[0011] The present invention addresses the problems of the prior art and provides a three-dimensional (3-D) integral imaging and display system using a variable focal length lens.

[0012] In one embodiment, a three-dimensional (3-D) display system includes at least one two-dimensional (2-D) display device, configured to display at least one twodimensional image. The display system also includes an array of micromirror array lenses optically coupled to the display device, each micromirror array lens of the array of micromirror array lenses placed at a different location with respect to the display device, configured to focus the at least one two-dimensional image from each different location to provide a three-dimensional (3-D) image.

[0013] In one aspect, the display device is a two-dimensional display panel. In another aspect, the display device is a projector. In another aspect, each micromirror array lens of the array of micromirror array lenses is configured to have its focal length adjusted to increase a depth range of the three-dimensional image. In another aspect, the display system also includes a beam splitter, optically coupled to the display device and the array of micromirror array lenses, configured to change a direction of light beams emitted by the display device by 90° to simulate an in-line optical arrangement. In another aspect, each micromirror array lens of the array of micromirror array lenses is a concave micromirror array lens. In another aspect, each micromirror array lens of the array of micromirror array lenses is a convex micromirror array lens.

[0014] In another embodiment, a three-dimensional imaging system includes an array of micromirror array lenses optically coupled to an image sensor, each micromirror array lens of the array of micromirror array lenses placed at a different location with respect to a three-dimensional object, configured to focus images of the three-dimensional object from each different location onto the image sensor. The image sensor is optically coupled to the array of micromirror array lenses and configured to sense the images of the three-dimensional object focused by the array of micromirror array lenses and to provide an image data signal.

[0015] In one aspect, each micromirror array lens of the array of micromirror array lenses is configured to have its focal length adjusted to focus images of the three-dimensional object from each different location onto the image sensor. In another aspect, the imaging system also includes a beam splitter, optically coupled to the image sensor and the array of micromirror array lenses, configured to change a direction of light beams focused by the array of micromirror array lenses by 90° to simulate an in-line optical arrangement. In another aspect, each micromirror array lens of the array of micromirror array lenses is a concave micromirror array lens. In another aspect, each micromirror array lens of the array of micromirror array lenses is a convex micromirror array lens.

[0016] In another embodiment, a three-dimensional imaging and display system includes a first array of micromirror array lenses optically coupled to an image sensor, micromirror array lenses of the first array of micromirror array lenses placed at first different locations with respect to a three-dimensional object, configured to focus images of the three-dimensional object from the first different locations onto the image sensor. The image sensor is optically coupled to the first array of micromirror array lenses, configured to sense the images of the three-dimensional object focused by the first array of micromirror array lenses and to provide an image data signal to a display device. The display device is communicatively coupled to the image sensor, configured to display at least one two-dimensional image in response to the image data signal. The imaging and display system also includes a second array of micromirror array lenses optically coupled to the display device, micromirror array lenses of the second array of micromirror array lenses placed at second different locations with respect to the display device, configured to focus the at least one two-dimensional image from the second different locations to provide a threedimensional image.

[0017] The advantages of the present invention include increased viewing angles and wide depth range of threedimensional images.

[0018] These and other features of the present invention will be described in more detail below in the detailed description of the invention and in conjunction with the following figures.

BRIEF DESCRIPTION OF THE DRAWINGS [0019] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the

accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0020] FIG. 1 depicts one embodiment of a prior art integral imaging and display system;

[0021] FIG. 2 depicts an embodiment of a prior art display system 175 to increase the depth range of the 3D image;

[0022] FIG. 3 depicts an embodiment of a prior art display system, using a concave mirror array;

[0023] FIG. 4A depicts a three-dimensional display system using an array of concave micromirror array lenses, according to an embodiment of the invention;

[0024] FIG. 4B depicts a three-dimensional display system using an array of convex micromirror array lenses, according to an embodiment of the invention;

[0025] FIG. 4C depicts a three-dimensional display system using an array of micromirror array lenses, according to another embodiment of the invention

[0026] FIG. 5 is a schematic representation showing how the depth range of a three-dimensional image is increased by changing the focal length of a micromirror array lens, according to an embodiment of the invention;

[0027] FIG. 6 depicts a three-dimensional imaging system using an array of micromirror array lenses, according to an embodiment of the invention;

[0028] FIG. 7 depicts a three-dimensional imaging and display system using arrays of micromirror array lenses, according to an embodiment of the invention; and

[0029] FIG. 8 depicts a three-dimensional display system using an array of micromirror array lenses and a beam splitter, according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0030] The present invention will now be described in detail with reference to a few embodiments thereof as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process steps and/or structures have not been described in detail in order to not unnecessarily obscure the present invention.

[0031] A three-dimensional (3-D) integral imaging and display system using a variable focal length lens (optical system) is provided. The variable focal length lens is a micromirror array lens, capable of having its focal length adjusted by translation and/or rotation of each micromirror in the micromirror array lens, as described in U.S. patent application Ser. Nos. 10/855,554, 10/855,715, 10/855,287, 10/857,796,10/857,714,10/857,280, all of which are hereby incorporated by reference. The micromirrors may be concave or convex. By using a micromirror array lens for imaging and display, increased viewing angles and wide depth range of three-dimensional images is provided.

[0032] In the various embodiments of display systems described herein, various types of two-dimensional (2-D) display devices (display devices) may be used, such as