Optical systems with compact back focal lengths

• US 20130182227A1
• Filed: 07/16/2012
• Published: 07/18/2013
• Est. Priority Date: 05/09/2008
• Status: Active Grant

• Current Assignee: RealD Incorporated
• Original Assignee: RealD Incorporated
• Inventors: Schuck, Miller H.
• Granted Patent: US 9,244,287 B2
• Time in Patent Office: Days
• US Class Current: 353/8
• CPC Class Codes: G02B 13/0095 Relay lenses or rod lenses in instruments for viewing the inside of hollow bodies G02B23/2446
• CPC Class Codes: G02B 13/16 for use in conjunction with image converters or intensifiers , or for use with projectors, e.g. objectives for projection TV
• CPC Class Codes: G02B 17/0896 with variable magnification or multiple imaging planes, including multispectral systems systems with only refractive elements G02B15/14
• CPC Class Codes: G02B 26/008 in the form of devices for effecting sequential colour changes, e.g. colour wheels
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G02B 30/25 using polarisation techniques
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: H04N 13/337 using polarisation multiplexing
• CPC Class Codes: H04N 13/341 using temporal multiplexing
• CPC Class Codes: H04N 13/363 using image projection screens volumetric display H04N13/388
• CPC Class Codes: H04N 9/3167 for polarizing the light beam polarizing optical systems per se G02B27/28

Abstract

Optical systems, such as 2-D and 3-D projection systems, may be configured to have a compact back focal length to allow for more compact projection lenses, lower throw ratios, improved contrast, or any combination thereof. In an embodiment, an optical system may include a relay element configured to form an intermediate image having a focal point proximate to a projection lens.

Claims

1. An optical system, comprising:

an imaging source operable to output light;

a relay element operable to receive the light from the imaging source; and

a projection lens;

wherein the relay element is configured to form an intermediate image having a focal point proximate to an entry surface of the projection lens, the focal point of the intermediate image and the entry surface of the projection lens defining a back focal length therebetween; and

wherein the projection lens is operable to project the intermediate image.

2. The optical system of claim 1, wherein the optical system further comprises a polarization conversion system operable to convert the light comprising the intermediate image to substantially a single polarization state and output converted light along first and second optical paths.

3. The optical system of claim 1, further comprising a polarizing beam splitter assembly and a second projection lens, wherein the projection lens and the second projection lens are disposed proximate to first and second exit ports of the polarizing beam splitter assembly, respectively, and wherein the relay element is configured to form a second intermediate image having a focal point proximate to an entry surface of the second projection lens, the focal point of the second intermediate image and the entry surface of the projection lens defining a back focal length therebetween.

4. The optical system of claim 1, wherein the relay element is configured to compensate for aberration.

5. The optical system of claim 1, wherein the projection lens is configured to compensate for aberration.

6. The optical system of claim 1, wherein the relay element and the projection lens are configured to cooperate to compensate an overall aberration.

7. The optical system of claim 1, wherein the imaging source comprises a spatial light modulator.

8. The optical system of claim 1, wherein the imaging source comprises a reflecting micromirror device.

9. The optical system of claim 1, wherein the imaging source is illuminated by laser light source, a lamp source, or a source comprising light emitting diodes.

10. The optical system of claim 1, wherein the projection lens comprises a zoom lens or a fixed focal length lens.

11. The optical system of claim 1, wherein the imaging source is a first imaging source, the relay element is a first relay element, and the projection lens is a first projection lens, and wherein the first imaging source, the first relay element, and the first projection lens are comprised in a first projection subsystem, and the optical system further comprises a second projection subsystem comprising:

a second imaging source operable to output light;

a second relay element operable to receive the light from the second imaging source; and

a second projection lens;

wherein the second relay element is configured to form a second intermediate image having a focal point proximate to an entry surface of the second projection lens, the focal point of the second intermediate image and the entry surface of the second projection lens defining a back focal length therebetween; and

wherein the second projection lens is operable to project the second intermediate image.

12. An optical system, comprising:

an imaging source operable to output light;

a relay element operable to receive the light from the imaging source;

a polarizing beam splitter assembly; and

first and second projection lenses disposed proximate to first and second exit ports of the polarizing beam splitter assembly, respectively;

wherein the relay element is configured to form a first intermediate image having a focal point between the first exit port of the polarizing beam splitter assembly and the first projection lens, the focal point of the first intermediate image and an entry surface of the first projection lens defining a first back focal length therebetween;

wherein the relay element is configured to form a second intermediate image having a focal point between the second exit port of the polarizing beam splitter assembly and the second projection lens, the focal point of the first intermediate image and an entry surface of the second projection lens defining a second back focal length therebetween;

wherein the first and second projection lenses are operable to project the first and second intermediate images, respectively.

13. The optical system of claim 12, wherein the polarizing beam splitter assembly comprises:

a polarizing beam splitter;

an odd number of reflectors optically following the polarizing beam splitter in a first output light path; and

an even number of reflectors optically following the polarizing beam splitter in a second output light path.

14. The optical system of claim 12, wherein the polarizing beam splitter assembly comprises:

a polarizing beam splitter;

a single reflector optically following the polarizing beam splitter in a first output light path; and

no reflector optically following the polarizing beam splitter in a second output light path.

15. The optical system of claim 12, further comprising first and second polarization elements optically following the first and second projection lens, respectively, and a polarization rotator disposed between the first exit port of the polarization beam splitter assembly and the first polarization element.

16. The optical system of claim 15, wherein the first and second polarization elements each comprise a passive polarizer or retarder.

17. The optical system of claim 15, wherein the first and second polarization elements each comprise a polarization modulator operable to output light of orthogonal polarizations.

18. The optical system of claim 12, wherein the imaging source is a first imaging source, the relay element is a first relay element, and the polarizing beam splitter assembly is a first polarization beam splitter assembly, and wherein the first imaging source, the first relay element, the first and second projection lenses, and the first polarization beam splitter assembly are comprised in a first projection subsystem, and the optical system further comprises a second projection subsystem comprising:

a second imaging source operable to output light;

a second relay element operable to receive the light from the second imaging source;

a second polarizing beam splitter assembly; and

third and forth projection lenses disposed proximate to first and second exit ports of the second polarizing beam splitter assembly, respectively;

wherein the second relay element is configured to form a third intermediate image having a focal point between the first exit port of the second polarizing beam splitter assembly and the third projection lens, the focal point of the third intermediate image and an entry surface of the third projection lens defining a third back focal length therebetween;

wherein the second relay element is configured to form a fourth intermediate image having a focal point between the second exit port of the second polarizing beam splitter assembly and the fourth projection lens, the focal point of the fourth intermediate image and an entry surface of the fourth projection lens defining a fourth back focal length therebetween;

wherein the third and fourth projection lenses are operable to project the third and fourth intermediate images, respectively.

19. An optical system, comprising:

an imaging source operable to output light;

a relay element operable to receive the light from the imaging source; and

a projection lens; and

a polarization conversion system;

wherein the relay element is configured to form an intermediate image having a focal point proximate to an entry surface of the projection lens, the focal point of the intermediate image and entry surface of the projection lens defining a back focal length therebetween; and

wherein the projection lens is operable to project light comprising the intermediate image through the polarization conversion system, the polarization conversion system being operable to convert the light comprising the intermediate image to substantially a single polarization state and output converted light along first and second optical paths.

20. The optical system of claim 19, wherein the polarization conversion system comprises a polarizing beam splitter operable to split light received from the projection lens into first and second light paths and first and second polarization elements disposed in the first and second light paths, respectively, and wherein the first and second polarization elements are each operable to switchably modulate light passing therethrough and output light of substantially orthogonal polarization states.

21. The optical system of claim 20, wherein the polarization conversion system further comprises a reflector to direct light along a first path towards a same direction as the second light path.

22. The optical system of claim 20, wherein the first and second polarization element are operable to sequentially output light of the substantially orthogonal polarization states, thereby providing stereoscopic images.

23. The optical system of claim 19, wherein the imaging source is a first imaging source, the relay element is a first relay element, the projection lens is a first projection lens, and the polarization conversion system is a first polarization conversion system, and wherein the first imaging source, the first relay element, the first projection lens, and the first polarization conversion system are comprised in a first projection subsystem, and the optical system further comprises a second projection subsystem comprising:

a second imaging source operable to output light;

a second relay element operable to receive the light from the second imaging source; and

a second projection lens; and

a second polarization conversion system;

wherein the second relay element is configured to form a second intermediate image having a focal point proximate to an entry surface of the second projection lens, the focal point of the second intermediate image and the entry surface of the second projection lens defining a back focal length therebetween; and

wherein the second projection lens is operable to project light comprising the second intermediate image through the second polarization conversion system, the second polarization conversion system being operable to convert the light comprising the second intermediate image to substantially a single polarization state and output converted light along first and second optical paths;

wherein the second polarization conversion system comprises a second polarizing beam splitter operable to split light received from the second projection lens into third and fourth light paths and third and fourth polarization elements disposed in the third and fourth light paths, respectively, and wherein the third and fourth polarization elements are each operable to switchably modulate light passing therethrough and sequentially output light of substantially orthogonal polarization states, thereby providing stereoscopic images.