Image projection system with a polarizing beam splitter

• US 7,306,338 B2
• Filed: 03/08/2005
• Issued: 12/11/2007
• Est. Priority Date: 07/28/1999
• Status: Active Grant

• Current Assignee: Moxtek (Polatechno Co.,Ltd.)
• Original Assignee: Moxtek (Polatechno Co.,Ltd.)
• Inventors: Hansen, Douglas P., Perkins, Raymond T., Gardner, Eric W.
• Primary Examiner(s): Dowling, William C.
• Application Number:
  US11/075,841
• Publication Number:
  US 20050206847A1
• Time in Patent Office: 1,008 Days
• Field of Search: 353/20, 353/31, 353/33, 353/34, 353/37, 353/122, 349/5, 349/7, 349/8, 349/9, 359/486
• US Class Current: 353/20
• CPC Class Codes: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

An image projection system has a wire grid polarizing beam splitter which functions as both the polarizer and the analyzer in the system. A light source produces a source light beam directed at the beam splitter which reflects one polarization and transmits the other. A liquid crystal array is disposed in either the reflected or transmitted beam. The array modulates the polarization of the beam, encoding image information thereon, and directs the modulated beam back to the beam splitter. The beam splitter again reflects one polarization and transmits the other so that the encoded image is either reflected or transmitted to a screen. The wire grid polarizing beam splitter is capable of being oriented at various incident angles with respect to the source light beam and modulated beam, and accepts relatively divergent light.

Claims

1. An image projection system for providing a bright and clear image, the system comprising:

a light source producing a visible light beam;

a wire-grid polarizing polarizing beam splitter locatable in the light beam and oriented at an angle with respect to the light beam, the wire-grid polarizing beam splitter comprising;

a transparent substrate having a first surface located in the light beam with the light beam striking the first surface at an angle, and

a generally parallel arrangement of thin, elongated elements supported by the substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

a reflective array locatable in either the reflected or transmitted beam, the array modulating the polarization of the beam by selectively altering the polarization of the beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

the wire-grid polarizing beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam and so that the arrangement of thin, elongated elements supported by the substrate is oriented to face towards the reflective array, and the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam, to separate out the unaltered polarization from the modulated beam;

a screen located in either the second reflected beam or the second transmitted beam for displaying the encoded image information.

2. The system of claim 1, wherein the beam splitter is a generally planar sheet.

3. The system of claim 1, wherein the beam splitter is oriented with respect to the light beam or the modulated beam at an incident angle between approximately 0 to 80 degrees.

4. The system of claim 1, wherein the beam splitter is oriented with respect to the light beam or the modulated beam at incidence angles greater than 47 degrees or less than 43 degrees.

5. The system of claim 1, wherein the light beam has a useful divergent cone with a half angle between approximately 12 and 25 degrees.

6. The system of claim 1, wherein the beam splitter is used at an F-number less than approximately f/2.5.

7. The system of claim 1, wherein the beam splitter has a throughput of at least 50% defined by the product of the fractional amount of p-polarization transmitted light and the fractional amount of s-polarization reflected light;

and wherein the s-polarization transmitted light and p-polarization reflected light are both less than 5%.

8. The system of claim 1, wherein the beam splitter has a throughput of at least 50% defined by the product of the fractional amount of s-polarization transmitted light and the fractional amount of p-polarization reflected light;

and wherein the p-polarization transmitted light and s-polarization reflected light are both less than 5%.

9. The system of claim 1, wherein the beam splitter has a throughput for the light beam of at least 65%, defined by the product of the fractional amount of reflected light and the fractional amount of transmitted light;

and wherein the percent of reflected light or the percent of transmitted light is greater than approximately 67%.

10. The system of claim 1, further comprising a pre-polarizer disposed between the light source and the beam splitter.

11. The system of claim 1, further comprising a post-polarizer disposed between the beam splitter and the screen.

12. The system of claim 1, wherein the array is disposed in the reflected beam;

and wherein the screen is disposed in the second transmitted beam.

13. The system of claim 1, wherein the array is disposed in the transmitted beam;

and wherein the screen is disposed in the second reflected beam.

14. The system of claim 1, wherein:

the arrangement of elements has a period less than approximately 0.21 microns,

the elements have a thickness between approximately 0.04 to 0.5 microns, and

the elements have a width of between approximately 30 to 76% of the period.

15. The system of claim 1, wherein the elements each have a cross section with a base, a top opposite the base, and opposite left and right sides;

and wherein the sides form an angle with respect to the base greater than approximately 68 degrees.

16. The system of claim 1, wherein the visible light beam produced by the light source has a wavelength between approximately 0.4 and 0.7 microns.

17. An image projection system comprising:

a light source producing a visible light beam having a wavelength between approximately 0.4 and 0.7 microns;

a wire-grid polarizing beam splitter locatable in the light beam and oriented at an angle with respect to the light beam, the wire grid polarizing beam splitter comprising;

a transparent substrate having a surface locatable in the light beam with the light beam striking the surface at an angle, and

a generally parallel arrangement of thin, elongated elements supported by the surface of the substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

a reflective array located near the polarizing beam splitter in the reflected beam, the array modulating the polarization of the reflected beam by selectively altering the polarization of the reflected beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back to the polarizing beam splitter;

the wire-grid polarizing beam splitter further being located in the modulated beam and oriented at an angle relative to the modulated beam, the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, to separate out the unaltered polarization from the modulated beam; and

a screen disposed in the transmitted beam for displaying the encoded image information.

18. An image projection system comprising:

a light source producing a visible light beam having a wavelength between approximately 0.4 and 0.7 microns;

a wire-grid polarizing beam splitter locatable in the light beam and oriented at an angle with respect to the light beam, the beam splitter comprising;

a transparent substrate having a surface locatable in the light beam with the light striking the surface at an angle, and

a generally parallel arrangement of thin, elongated elements supported by the substrate opposite the surface, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam;

a reflective array located near the polarizing beam splitter in the transmitted beam, the array modulating the polarization of the transmitted beam by selectively altering the polarization of the transmitted beam to encode image information thereon and creating a modulated beam, and being oriented to direct the modulated beam back to the beam splitter;

the wire-grid polarizing beam splitter further being located in the modulated beam and oriented at an angle with respect to the modulated beam, the arrangement of elements of the beam splitter interacting with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam, to separate the altered polarization from the unaltered polarization in the modulated beam, thereby extracting the image information in the modulated beam; and

a screen located in the reflected beam for displaying the extracted image information in the modulated beam.

19. An image display system for producing a visible image, the system comprising:

a light source for emitting a source light beam having a wavelength in a range between approximately 0.4 to 0.7 microns;

a liquid crystal array positioned and oriented for receiving and modulating at least a portion of the source light beam and creating a modulated beam, the modulated beam containing image information;

a screen positioned and oriented for receiving and displaying at least a portion of the modulated beam; and

a wire-grid polarizing beam splitter disposed in both the source light beam and the modulated beam, the polarizing beam splitter comprising;

a generally parallel arrangement of thin, elongated elements configured and sized to interact with electromagnetic waves of the source light beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam, and interacts with the electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the modulated light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization orientation that lies in the plane that includes at least one of the elements and the direction of the modulated light beam, defining a second reflected beam; and

the beam splitter being oriented so that the generally parallel arrangement of thin, elongated elements face towards the liquid crystal array.

20. An image projection system for providing a bright and clear image, the system comprising:

a light source producing a visible light beam;

a bandwidth separator, locatable in the visible light beam, to separate the visible light beam into a plurality of colored beams of different bandwidths;

a plurality of color modulator systems, each locatable in a different one of the plurality of colored beams of different bandwidths, each color modulator system including;

a wire grid polarizing beam splitter, locatable in the color beam, comprising;

a transparent substrate locatable in the colored beam, and

a generally parallel arrangement of thin, elongated elements supported by the substrate, the arrangement being configured and the elements being sized to interact with electromagnetic waves of the colored beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to a plane that includes at least one of the elements and the direction of the incident light beam, defining a transmitted beam, and (ii) reflect light from the elements which has a polarization oriented parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a reflected beam;

a reflective array, locatable in the transmitted beam from the wire grid polarizing beam splitter, the array modulating the polarization of the transmitted beam by selectively altering the polarization of the transmitted beam to encode image information thereon and creating a modulated beam, the array being oriented to direct the modulated beam back towards the polarizing beam splitter;

the wire grid polarizing beam splitter further being located in the modulated beam so that the arrangement of elements of the beam splitter interact with electromagnetic waves of the modulated beam to generally (i) transmit light through the elements which has a polarization oriented perpendicular to the plane that includes at least one of the elements and the direction of the incident light beam, defining a second transmitted beam, and (ii) reflect light from the elements which has a polarization parallel with the plane that includes at least one of the elements and the direction of the incident light beam, defining a second reflected beam;

a combiner, disposable in the second reflected beam of each color modulation system, to combine the second reflected beams into a combined beam; and

a screen locatable in the combined beam.

21. The system of claim 20, wherein each of the plurality of color modulator systems produces a modulated color beam without a pre-polarizer disposed prior to the wire-grid polarizing beam splitter.

22. The system of claim 20, wherein the wire grid polarizing beam splitter is oriented so that the generally parallel arrangement of thin, elongated elements face towards the reflective array.