WO2005096056A1 - Anti-aliasing projection lens - Google Patents

Anti-aliasing projection lens Download PDF

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Publication number
WO2005096056A1
WO2005096056A1 PCT/US2004/008435 US2004008435W WO2005096056A1 WO 2005096056 A1 WO2005096056 A1 WO 2005096056A1 US 2004008435 W US2004008435 W US 2004008435W WO 2005096056 A1 WO2005096056 A1 WO 2005096056A1
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WIPO (PCT)
Prior art keywords
lens
projection
nyquist frequency
lens set
transfer function
Prior art date
Application number
PCT/US2004/008435
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French (fr)
Inventor
Estill Thone Hall, Jr.
Eugene Murphy O'donnell
Original Assignee
Thomson Licensing S. A.
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Publication date
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Priority to PCT/US2004/008435 priority Critical patent/WO2005096056A1/en
Publication of WO2005096056A1 publication Critical patent/WO2005096056A1/en

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    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00Optical objectives specially designed for the purposes specified below
    • G02B13/16Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00Details of colour television systems
    • H04N9/12Picture reproducers
    • H04N9/31Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3141Constructional details thereof
    • H04N9/317Convergence or focusing systems

Definitions

  • the invention is directed to a projection lens, and more particularly to a projection lens set that reduces aliasing and sub-pixel defects.
  • a modulated light output from an imager is projected by a projection lens system onto a screen to form a viewable image.
  • Most historical projection devices (slides, film, cathode ray tubes) have been analogue in nature. In these analogue projection devices, a projection lens system was desired having the highest perceived resolution that was economically practical.
  • the projection lens performance is maximized to the extent that it is economically practical.
  • Existing digital projection devices can suffer from projection anomalies such as digital artifacts, aliasing, and sub-pixel defects. Digital artifacts are caused by undesirable energy or noise being projected by the projection lens system.
  • This noise can be caused by components of the projection device and/or transmission of a signal to the device.
  • Digital artifacts are particularly common at frequencies that are multiples of the video signal, particularly at twice the signal frequency. Aliasing results from details that are poorly fitted to individual pixels, and tend to be more pronounced with poorer resolution.
  • Sub-pixel defects are small anomalies that prevent a portion of a crO-mirror or liquid crystal on silicon (LCOS) cell from functioning properly, particularly by providing a bright image over a portion of such structures. Accordingly, it is an object of the invention to provide a projection system for a digital projection device that provides the perceived image quality associated with a high resolution projection system while minimizing projection anomalies.
  • the present invention provides a projection lens system for projecting a video signal of an optical display device.
  • the lens set has a Modulus of the Optical Transfer Function at the Nyquist frequency for the video signal and a Modulus of the Optical Transfer Function at twice the Nyquist frequency for the video signal, such that the Modulus of the Optical Transfer Function at the Nyquist frequency has at least twice the value of the Optical Transfer Function at twice the Nyquist frequency.
  • Fig. 1 shows an exemplary projection lens system comprising a seven lens architecture according to an embodiment of the present invention
  • Fig. 2 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 1 at the Nyquist frequency
  • Fig. 3 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 1 at twice the Nyquist frequency
  • Fig. 4 shows an alternative exemplary projection lens system using long lenses according to an embodiment of the present invention
  • Fig. 5 shows a set of calculated curves for the optical transfer function for the exemplary projection lens system of Fig. 4 at the Nyquist frequency
  • Fig. 6 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 4 at twice the Nyquist frequency.
  • the present invention provides a projection lens system for use in a digital projection device to provide good resolution while reducing undesirable projection anomalies. This is accomplished by maximizing the modulus of the optical transfer function of the lens system at the Nyquist frequency while minimizing the modulus of the optical transfer function of the lens system at twice the Nyquist frequency.
  • An exemplary lens system 10 according to the invention is shown in Fig. 1.
  • the exemplary lens system 10 comprises seven lens elements 81, 82, 83, 84, 85, 86,
  • Lens elements 81, 82, 87 are asymmetric acrylic lenses.
  • Lens elements 83 and 84 are symmetrical lens elements that conform to one another and are joined at the end of element 83 and the start of element 84 to form an acromat lens 83/84.
  • lens elements 85 and 86 are symmetrical lens elements that conform to one another and are joined at the end of element 85 and the start of element 86 to form an acromat lens 85/86.
  • Both surfaces of the second aspheric lens 82 and the third aspheric lens 87 have a forward direction of curvature (i.e., a positive radius or a curvature in the direction of projection).
  • the first surface 81a has a backward direction of curvature (i.e., a negative radius) and the second surface 81b has a forward direction of curvature.
  • the first acromatic lens 83/84 has three surfaces 83a, 84a, 84b defining two lens elements 83, 84.
  • the first surface 83a and third surface 84b have a negative direction of curvature and the second surfaces 84a has a positive direction of curvature.
  • the second acromatic lens 85/86 also has three surfaces 85a, 86a, 86b defining two lens elements 85, 86.
  • Each of the surfaces 84a, 84b, 84c of the second acromatic lens 85/86 have a negative direction of curvature.
  • the acromat lens elements are made from inexpensive glass, such as SF14, SF15, BAK1, and BALF4.
  • Surface data for the lens system 10 is provided in table 1, with the asymmetric coefficients for lens surfaces 81a, 81b, 82a, 82b, 87a, and 87b provided in table 2.
  • These exemplary lens surfaces were developed by the inventors using ZEMAXTM software and novel characteristics determined by the inventors.
  • the thickness values are the distance to the previous surface (i.e., the thickness for the back surface of a lens element is the thickness of that lens element, and the thickness for the front surface of a lens is the air gap in front of that lens).
  • the projection lens system is disposed between an imager 60 and a viewing screen (not shown).
  • the imager 60 provides a matrix of light pixels, each pixel having an intensity modulated according to a signal provided to the imager.
  • the output from the imager passes through a polarizing beam splitter or PBS 50 and into the first lens comprising a single aspheric lens element 81, which directs the modulated matrix of light into the second lens comprising a single aspheric lens element 82.
  • the second asymmetric lens directs the modulated matrix of light into the first acromat lens 83/84 comprising lens elements 83, 84.
  • the first acromat lens 83/84 focuses the matrix of light such that it converges and inverts at the lens system stop 80. After passing the system stop 80, the matrix of light diverges until it enters the second acromat lens 85/86.
  • the second acromat lens 85/86 causes the matrix of light to converge and directs the matrix of light into the third aspheric lens 87.
  • the third aspheric lens 87 projects the matrix of light onto the viewing screen in a diverging pattern to distribute the pixels of light over the viewing screen.
  • Figures 2 and 3 show the calculated modulus of the optical transfer function (MTF) for the exemplary lens system 10, described above. The values are calculated using ZEMAXTM software. As shown in Fig.
  • the MTF is greater than about 0.6 at the worst location.
  • the MTF is less than about 0.25 at the worst location.
  • the MTF at the Nyquist frequency (36 line pairs/millimeter) is between three and six times greater than the MTF at twice the Nyquist frequency (72 line pairs/millimeter).
  • Fig. 4 shows an alternative exemplary lens system 110 for maximizing the MTF at the Nyquist frequency and minimizing the MTF at twice the Nyquist frequency, according to the invention.
  • Alternate exemplary lens system 110 comprises six lenses 181, 182/183, 184/185, 186, 187/188, 189 having a total of nine lens elements 181 - 189.
  • Each of the nine lens elements 181 - 189 has an asymmetrical surface geometry.
  • the first, fourth and sixth lenses (proceeding in the direction of projection - from right to left in Fig. 1) 181, 186, 189 each comprise a single asymmetric lens element 181, 186, 189, respectively.
  • the second, third, and fifth lenses 182/183, 184/185, 187/188 each comprise two asymmetric lens elements.
  • the back surface of the first lens element 182, 184, 187 of each pair conforms to and is joined to the front surface of the second lens element 183, 185, 188, respectively, of each pair to form an asymmetric acromat lens.
  • the thickness values are the distance to the previous surface (i.e., the thickness for the back surface of a lens element is the thickness of that lens element, and the thickness for the front surface of a lens is the air gap in front of that lens).
  • the directions of curvature for the surfaces of the alternate exemplary lens system 110 are indicated again by the sign of the radius values, with positive radii indicating a forward curvature and negative radii indicating a backward curvature.
  • Figures 5 and 6 show the calculated modulus of the optical transfer function (MTF) for the alternate exemplary lens system 110, described above.
  • the values are calculated using ZEMAXTM software.
  • the MTF is greater than about 0.6 at the worst location.
  • the MTF is less than about 0.25 at the worst location.
  • the MTF at the Nyquist frequency (36 line pairs/millimeter) is between three and six times greater than the MTF at twice the Nyquist frequency (72 line pairs/millimeter).
  • the distortion also called grid distortion, as determined for the exemplary lens system 110 using ZEMAXTM software, is less than about 0.2%, meaning that at the worst location, the light from a specific pixel of an imager with a matrix 200 pixels wide will be projected onto the viewing screen at a location about a quarter of a pixel- width from the intended or optimum location.

Abstract

The present invention provides a projection lens set for projecting a video signal of an optical display device. The lens set has a Modulus of the Optical Transfer Function at the Nyquist frequency for the video signal and a Modulus of the Optical Transfer Function at twice the Nyquist frequency for the video signal, such that the Modulus of the Optical Transfer Function at the Nyquist frequency has at least twice the value of the Optical Transfer Function at twice the Nyquist frequency.

Description

ANTI-ALIASING PROJECTION LENS
Field of the Invention The invention is directed to a projection lens, and more particularly to a projection lens set that reduces aliasing and sub-pixel defects.
Background of the Invention In a microdisplay system, a modulated light output from an imager is projected by a projection lens system onto a screen to form a viewable image. Most historical projection devices (slides, film, cathode ray tubes) have been analogue in nature. In these analogue projection devices, a projection lens system was desired having the highest perceived resolution that was economically practical. Similarly, in existing projecting devices for projecting digital (pixelized) images, the projection lens performance is maximized to the extent that it is economically practical. Existing digital projection devices can suffer from projection anomalies such as digital artifacts, aliasing, and sub-pixel defects. Digital artifacts are caused by undesirable energy or noise being projected by the projection lens system. This noise can be caused by components of the projection device and/or transmission of a signal to the device. Digital artifacts are particularly common at frequencies that are multiples of the video signal, particularly at twice the signal frequency. Aliasing results from details that are poorly fitted to individual pixels, and tend to be more pronounced with poorer resolution. Sub-pixel defects are small anomalies that prevent a portion of a miciO-mirror or liquid crystal on silicon (LCOS) cell from functioning properly, particularly by providing a bright image over a portion of such structures. Accordingly, it is an object of the invention to provide a projection system for a digital projection device that provides the perceived image quality associated with a high resolution projection system while minimizing projection anomalies.
Summary of the Invention The present invention provides a projection lens system for projecting a video signal of an optical display device. The lens set has a Modulus of the Optical Transfer Function at the Nyquist frequency for the video signal and a Modulus of the Optical Transfer Function at twice the Nyquist frequency for the video signal, such that the Modulus of the Optical Transfer Function at the Nyquist frequency has at least twice the value of the Optical Transfer Function at twice the Nyquist frequency. By maximizing the MTF at the Nyquist frequency while minimizing the MTF at twice the Nyquist frequency, a sharp digital image is produced (due to the high MTF at the Nyquist frequency) while digital artifacts, which occur primarily due to high energy noise at twice the Nyquist frequency, and anomalies caused by sub-pixel defects in the imager are reduced as compared to a lens system that is only optimized at the Nyquist frequency.
Brief Description of the Drawings The invention will be described with reference to the drawing, in which: Fig. 1 shows an exemplary projection lens system comprising a seven lens architecture according to an embodiment of the present invention; Fig. 2 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 1 at the Nyquist frequency; Fig. 3 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 1 at twice the Nyquist frequency; Fig. 4 shows an alternative exemplary projection lens system using long lenses according to an embodiment of the present invention; Fig. 5 shows a set of calculated curves for the optical transfer function for the exemplary projection lens system of Fig. 4 at the Nyquist frequency; and Fig. 6 shows a set of calculated curves for the modulus of the optical transfer function for the exemplary projection lens system of Fig. 4 at twice the Nyquist frequency.
Detailed Description of the Invention The present invention provides a projection lens system for use in a digital projection device to provide good resolution while reducing undesirable projection anomalies. This is accomplished by maximizing the modulus of the optical transfer function of the lens system at the Nyquist frequency while minimizing the modulus of the optical transfer function of the lens system at twice the Nyquist frequency. An exemplary lens system 10 according to the invention is shown in Fig. 1. The exemplary lens system 10 comprises seven lens elements 81, 82, 83, 84, 85, 86,
87, respectively in ascending order in the projection direction from an imager 60 to a projection screen (not shown) to the left of Fig. 1. A theoretical plane at which transmitted light transitions from convergence to divergence, called the system stop 80, is positioned between lens elements 84 and 85. Lens elements 81, 82, 87 are asymmetric acrylic lenses. Lens elements 83 and 84 are symmetrical lens elements that conform to one another and are joined at the end of element 83 and the start of element 84 to form an acromat lens 83/84. Similarly, lens elements 85 and 86 are symmetrical lens elements that conform to one another and are joined at the end of element 85 and the start of element 86 to form an acromat lens 85/86. Both surfaces of the second aspheric lens 82 and the third aspheric lens 87 have a forward direction of curvature (i.e., a positive radius or a curvature in the direction of projection). In the first aspheric lens 81, the first surface 81a has a backward direction of curvature (i.e., a negative radius) and the second surface 81b has a forward direction of curvature. The first acromatic lens 83/84 has three surfaces 83a, 84a, 84b defining two lens elements 83, 84. The first surface 83a and third surface 84b have a negative direction of curvature and the second surfaces 84a has a positive direction of curvature. The second acromatic lens 85/86 also has three surfaces 85a, 86a, 86b defining two lens elements 85, 86. Each of the surfaces 84a, 84b, 84c of the second acromatic lens 85/86 have a negative direction of curvature. The acromat lens elements are made from inexpensive glass, such as SF14, SF15, BAK1, and BALF4. Surface data for the lens system 10 is provided in table 1, with the asymmetric coefficients for lens surfaces 81a, 81b, 82a, 82b, 87a, and 87b provided in table 2. These exemplary lens surfaces were developed by the inventors using ZEMAX™ software and novel characteristics determined by the inventors. The thickness values are the distance to the previous surface (i.e., the thickness for the back surface of a lens element is the thickness of that lens element, and the thickness for the front surface of a lens is the air gap in front of that lens).
TABLE 1 (dimensions in millimeters)
Figure imgf000006_0001
TABLE 2
Figure imgf000007_0001
TABLE 2 (continued)
Figure imgf000007_0002
The projection lens system is disposed between an imager 60 and a viewing screen (not shown). The imager 60 provides a matrix of light pixels, each pixel having an intensity modulated according to a signal provided to the imager. In a microdisplay using an LCOS imager, the output from the imager passes through a polarizing beam splitter or PBS 50 and into the first lens comprising a single aspheric lens element 81, which directs the modulated matrix of light into the second lens comprising a single aspheric lens element 82. The second asymmetric lens directs the modulated matrix of light into the first acromat lens 83/84 comprising lens elements 83, 84. The first acromat lens 83/84 focuses the matrix of light such that it converges and inverts at the lens system stop 80. After passing the system stop 80, the matrix of light diverges until it enters the second acromat lens 85/86. The second acromat lens 85/86 causes the matrix of light to converge and directs the matrix of light into the third aspheric lens 87. The third aspheric lens 87 projects the matrix of light onto the viewing screen in a diverging pattern to distribute the pixels of light over the viewing screen. Figures 2 and 3 show the calculated modulus of the optical transfer function (MTF) for the exemplary lens system 10, described above. The values are calculated using ZEMAX™ software. As shown in Fig. 2, at a spatial frequency of 36 line pairs per millimeter (the Nyquist frequency), the MTF is greater than about 0.6 at the worst location. As shown in Fig. 3, at a spatial frequency of 72 line pairs per millimeter (twice the Nyquist frequency), the MTF is less than about 0.25 at the worst location. Furthermore, at any one location, the MTF at the Nyquist frequency (36 line pairs/millimeter) is between three and six times greater than the MTF at twice the Nyquist frequency (72 line pairs/millimeter). By maximizing the MTF at the Nyquist frequency while minimizing the MTF at twice the Nyquist frequency, a sharp digital image is produced (due to the high MTF at the Nyquist frequency) while digital artifacts, which occur primarily due to high energy noise at twice the Nyquist frequency, and anomalies caused by sub-pixel defects in the imager are reduced as compared to a lens system that is only optimized at the Nyquist frequency. The distortion, also called grid distortion, as determined for the exemplary lens system 10 using ZEMAX™ software, is less than about 0.6%, meaning that at the worst location, the light from a specific pixel of an imager with a matrix 200 pixels wide will be projected onto the viewing screen at a location about a half of a pixel-width from the intended or optimum location. Fig. 4 shows an alternative exemplary lens system 110 for maximizing the MTF at the Nyquist frequency and minimizing the MTF at twice the Nyquist frequency, according to the invention. Alternate exemplary lens system 110 comprises six lenses 181, 182/183, 184/185, 186, 187/188, 189 having a total of nine lens elements 181 - 189. Each of the nine lens elements 181 - 189 has an asymmetrical surface geometry. The first, fourth and sixth lenses (proceeding in the direction of projection - from right to left in Fig. 1) 181, 186, 189 each comprise a single asymmetric lens element 181, 186, 189, respectively. The second, third, and fifth lenses 182/183, 184/185, 187/188 each comprise two asymmetric lens elements. The back surface of the first lens element 182, 184, 187 of each pair conforms to and is joined to the front surface of the second lens element 183, 185, 188, respectively, of each pair to form an asymmetric acromat lens. Surface data for the lenses 181, 182/183, 184/185, 186, 187/188, 189 of the alternate exemplary lens system 110 are provided in table 3, with the asymmetric coefficients provided in table 4. These exemplary lens surfaces were developed by the inventors using ZEMAX™ software and novel characteristics determined by the inventors. The thickness values are the distance to the previous surface (i.e., the thickness for the back surface of a lens element is the thickness of that lens element, and the thickness for the front surface of a lens is the air gap in front of that lens). The directions of curvature for the surfaces of the alternate exemplary lens system 110 are indicated again by the sign of the radius values, with positive radii indicating a forward curvature and negative radii indicating a backward curvature.
TABLE 3 (dimensions in millimeters)
Figure imgf000010_0001
TABLE 3 (continued)
Figure imgf000011_0001
TABLE 4
Figure imgf000011_0002
Figure imgf000012_0001
TABLE 4 (continued)
Figure imgf000013_0001
Figures 5 and 6 show the calculated modulus of the optical transfer function (MTF) for the alternate exemplary lens system 110, described above. The values are calculated using ZEMAX™ software. As shown in Fig. 5, at a spatial frequency of 36 line pairs per millimeter (the Nyquist frequency), the MTF is greater than about 0.6 at the worst location. As shown in Fig. 6, at a spatial frequency of 72 line pairs per millimeter (twice the Nyquist frequency), the MTF is less than about 0.25 at the worst location. Moreover, at any specific screen location, the MTF at the Nyquist frequency (36 line pairs/millimeter) is between three and six times greater than the MTF at twice the Nyquist frequency (72 line pairs/millimeter). By maximizing the MTF at the Nyquist frequency while minimizing the MTF at twice the Nyquist frequency, a sharp digital image is produced (due to the high MTF at the Nyquist frequency) while digital artifacts, which occur primarily due to high energy noise at twice the Nyquist frequency, and anomalies caused by sub-pixel defects in the imager are reduced as compared to a lens system that is only optimized at the Nyquist frequency. The distortion, also called grid distortion, as determined for the exemplary lens system 110 using ZEMAX™ software, is less than about 0.2%, meaning that at the worst location, the light from a specific pixel of an imager with a matrix 200 pixels wide will be projected onto the viewing screen at a location about a quarter of a pixel- width from the intended or optimum location. The foregoing illustrates some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents.

Claims

What is Claimed is: 1. A projection lens set for projecting a video signal of an optical display device onto a screen, the projection lens set having a Modulus of the Optical Transfer Function at the Nyquist frequency for the video signal at each location on the screen and a Modulus of the Optical Transfer Function at twice the Nyquist frequency for the video signal at each location on the screen, the Modulus of the Optical Transfer Function at the Nyquist frequency having a value that is at least three times greater than the value of the Optical Transfer Function at twice the Nyquist frequency for the same location on the screen.
2. The projection lens set of claim 1 wherein the Nyquist frequency is 36 line pairs per millimeter.
3. The projection lens set of claim 1 wherein the grid distortion of the lens set is less than about 0.6 percent.
4. The projection lens set of claim 1 wherein the grid distortion of the lens set is less than about 0.2 percent.
5. The projection lens set of claim 1 wherein the lens set comprises seven lens elements.
6. The projection lens set of claim 5 wherein the first, second and seventh lens elements in a direction of projection are asymmetric acrylic lenses, the third and four lens elements in the direction of projection are symmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens, and the fifth and sixth lens elements in the direction of projection are symmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens.
7. The projection lens set of claim 6 wherein a system stop is located between the fourth and the fifth lens elements in the direction of projection.
8. The projection lens set of claim 1 wherein the lens set comprises nine lens elements.
9. The projection lens set of claim 8 wherein each lens element is asymmetric.
10. The projection lens set of claim 9 wherein the second and third lens elements in the direction of projection are symmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens, the fourth and fifth lens elements in the direction of projection are symmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens, and the seventh and eighth lens elements in the direction of projection are symmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens.
11. The projection lens set of claim 10 wherein a system stop is located between the fifth and sixth lens elements in the direction of projection.
12. A projection lens set for projecting a video signal of an optical display device having a Modulus of the Optical Transfer Function of at least 60 percent at the Nyquist frequency for the video signal and having a Modulus of the Optical Transfer Function of no more than 30 percent at twice the Nyquist frequency for the video signal.
13. The projection lens set of claim 12 wherein the Nyquist frequency is 36 line pairs per millimeter.
14. The projection lens set of claim 12 wherein the grid distortion of the lens set is less than about 0.6 percent.
15. The projection lens set of claim 12 wherein the grid distortion of the lens set is less than about 0.2 percent.
16. The projection lens set of claim 12 wherein the lens set includes seven lens elements.
17. The projection lens set of claim 16 wherein at least one of the lens elements is an asymmetrical.
18. The projection lens set of claim 16 wherein at least two adjacent lens elements in the direction of projection are assymmetric lenses conforming to and joined to one another at adjacent faces thereof to form an acromat lens.
19. A projection apparatus, comprising: an imager for modulating each pixel of a video signal; a screen for viewing the modulated video signal; and a projection lens system having a plurality of lens elements providing a Modulus of the Optical Transfer Function at the Nyquist frequency for the video signal and a Modulus of the Optical Transfer Function at twice the Nyquist frequency for the video signal, the Modulus of the Optical Transfer Function at the Nyquist frequency having a value that is at least three times greater than the value of the Optical Transfer Function at twice the Nyquist frequency for a single location on the screen.
20. The projection apparatus of claim 19 wherein the lens system has no more than nine lens elements.
PCT/US2004/008435 2004-03-19 2004-03-19 Anti-aliasing projection lens WO2005096056A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189211A (en) * 1978-01-03 1980-02-19 Kollmorgen Corporation Wide angle telecentric projection lens assembly
EP0567995A1 (en) * 1992-04-28 1993-11-03 Kuraray Co., Ltd. Image display apparatus
US5625495A (en) * 1994-12-07 1997-04-29 U.S. Precision Lens Inc. Telecentric lens systems for forming an image of an object composed of pixels
US20010013977A1 (en) * 1998-10-23 2001-08-16 Biljana Tadic-Galeb Projection Lens and system
US6476974B1 (en) * 2001-02-28 2002-11-05 Corning Precision Lens Incorporated Projection lenses for use with reflective pixelized panels

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4189211A (en) * 1978-01-03 1980-02-19 Kollmorgen Corporation Wide angle telecentric projection lens assembly
EP0567995A1 (en) * 1992-04-28 1993-11-03 Kuraray Co., Ltd. Image display apparatus
US5625495A (en) * 1994-12-07 1997-04-29 U.S. Precision Lens Inc. Telecentric lens systems for forming an image of an object composed of pixels
US20010013977A1 (en) * 1998-10-23 2001-08-16 Biljana Tadic-Galeb Projection Lens and system
US6476974B1 (en) * 2001-02-28 2002-11-05 Corning Precision Lens Incorporated Projection lenses for use with reflective pixelized panels

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
WARREN J. SMITH: "MODERN OPTICAL ENGINEERING", 1966, MCGRAW-HILL, US, XP002299890 *

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