WO1998015164A2 - Appareil et technique de projection optique - Google Patents

Appareil et technique de projection optique Download PDF

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Publication number
WO1998015164A2
WO1998015164A2 PCT/IB1996/001129 IB9601129W WO9815164A2 WO 1998015164 A2 WO1998015164 A2 WO 1998015164A2 IB 9601129 W IB9601129 W IB 9601129W WO 9815164 A2 WO9815164 A2 WO 9815164A2
Authority
WO
WIPO (PCT)
Prior art keywords
image
optical system
optical
anamorphic
horizontal
Prior art date
Application number
PCT/IB1996/001129
Other languages
English (en)
Other versions
WO1998015164A3 (fr
Inventor
Leo Beiser
Original Assignee
Leo Beiser
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leo Beiser filed Critical Leo Beiser
Priority to CA002305268A priority Critical patent/CA2305268C/fr
Priority to PCT/IB1996/001129 priority patent/WO1998015164A2/fr
Priority to EP96933567A priority patent/EP0931275A4/fr
Publication of WO1998015164A2 publication Critical patent/WO1998015164A2/fr
Publication of WO1998015164A3 publication Critical patent/WO1998015164A3/fr

Links

Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/147—Optical correction of image distortions, e.g. keystone
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B37/00—Panoramic or wide-screen photography; Photographing extended surfaces, e.g. for surveying; Photographing internal surfaces, e.g. of pipe
    • G03B37/06—Panoramic or wide-screen photography; Photographing extended surfaces, e.g. for surveying; Photographing internal surfaces, e.g. of pipe involving anamorphosis

Definitions

  • This invention relates to the field of optical display and, more particularly, to an optical system and method for displaying an image.
  • an image is projected and displayed on a solid panel display device.
  • tilted image surfaces are also subject to "keystoning", whereby one dimension (say, the horizontal "width”) is enlarged progressively more as viewed from the "top” or the “bottom” of the image .
  • FIG. 1 illustrates the type of panel construction described in the '502 Patent.
  • the panel comprises a stack of thin waveguide-like transparent lamina 111 each of typical thickness t.
  • h t sec S.
  • S measuring typically about 70°
  • h is significantly larger than t.
  • the full display height H is larger than the base thickness T by the same factor, sec S.
  • the device of the '502 Patent is called a "polyplanar optic display" (POD).
  • the rightmost portion of the POD is represented primarily in Figure 1 as an isometric view.
  • the full width W is typically wider than its display height H.
  • the portion which is detailed serves to describe the operation of the POD and is useful in understanding its relationship to the present invention.
  • Each lamination (of thickness t) of the panel is a transparent sheet (glass or plastic) of nominal optical index of refraction n , separated by thin coatings of index of refraction n 2 , where n 1 > n 2 .
  • Light entering the laminations at the base is separated into sheets and is confined to its respective sheets by total internal reflection at the interfaces.
  • each thickness t is displayed as a corresponding resolvable height h.
  • the width W direction there is no confinement of the input illumination, and each sheet propagates its respective slice (in the width direction) as would a continuous transparent medium. This requires that the horizontal image components be focused over varying distances corresponding to the tipped viewing surface.
  • the horizontal information must focus near the sloping plane of the display surface; those components at the "bottom” of the display focusing close to the base, and those higher focusing at progressively greater distances to represent image elements approaching the top of the display. Also, while propagating through the lamina, the horizontal components expand progressively as an extension to the expanding illuminating field. Unless corrected, this generates keystoning, whereby (in this example) the top of the displayed image becomes wider than that at the bottom.
  • an optical system for displaying an image of an object.
  • a display device is provided and has an input surface and an output surface. Means are provided for illuminating the object so that light from the object is directed toward said input surface.
  • Anamorphic optical means is disposed in the light path between the object and the input surface, the anamorphic optical means being operative to focus one directional component of the image at the input surface and to focus a different directional component of the image at the output surface.
  • the display device is a panel device formed of a solid material and having disparate imaging surfaces for said different directional components, at least one of said imaging surfaces being non-perpendicular to the optical axis of the light.
  • the object is a planar object tipped with respect to said optical axis by an angle that satisfies the Scheimpflug condition for said at least one of said imaging surfaces, the angle taking into account the refractive effect of the solid material on said light.
  • a telecentric optical component can be disposed in the path of the light to correct for keystoning of said image.
  • Figure 1 is an isometric view, in partially broken away form, of a prior art POD display panel.
  • Figure 2 is a diagram of the projected optical field, and the POD display, in accordance with an embodiment of the apparatus of the invention and which can be used in practicing an embodiment of the method of the invention.
  • Figure 3 shows a cross sectional view of a POD, and is useful in understanding determination of imaging surfaces and the determination of tilt.
  • Figure 4 shows an embodiment of an apparatus and technique for practicing the invention using a scanning laser beam to form the image.
  • Figure 4A illustrates a lens for providing focusing on a sloping image plane that can be used in the Figure 4 embodiment .
  • IMAGE PROJECTION To develop relationships between the object and its projected image, the entire projected field is represented in Figure 2, with the POD 205 positioned such that the rays (propagating from left to right) remain “unfolded” until they arrive at the POD base. (If a "folding" reflective element is interposed in the ray path, the rays may be directed "upward” such that the POD can be positioned for typical upright viewing) .
  • the principles hereof relate to the transfer of information from the object surface to the image surfaces of the POD.
  • the manner of illuminating the object is independent of this transfer.
  • the object will be assumed conventional; either transmissive or reflective; illuminated with incoherent or coherent light.
  • One exception to this independence is the case of illumination of the POD by a scanned laser beam, wherein the "object" may be virtual; that is, contained in the software which addresses the laser beam intensity while it is scanned. This case will be discussed subsequently.
  • the object can be one of a variety of light valves which may be static for projection of a still picture (such as a photographic slide), or dynamic, forming moving images or changing data (such as by any of the electronically controlled light valves).
  • the object is planar and it exhibits spatial information which is to be projected to a distant image surface.
  • a plane object "light valve" 211 oriented at the origin of an x-y-z coordinate system as shown, the object is tipped such that its plane forms an angle ⁇ with the z-Axis. This will be discussed subsequently.
  • Figure 2 also shows a lens L t close to the POD, operating as a telecentric element to rectify keystoning. It is provided with a long focal length, whereby its focal point is positioned near the source of diverging rays (in the vicinity of C ) so that it operates on the arriving diverging ray bundles to collimate them as they propagate into the POD.
  • This additional optical power positioned close to the focal regions in the POD, also shortens slightly the original focal lengths, as calculated per Equation 1 for C h and C v alone. Considerations for this and other factors relating to the development of the focal surfaces in the POD are now discussed.
  • the horizontal projection components must accommodate the tilting of the horizontal image plane in the POD (due to the differing propagation lengths within the lamina) .
  • the projected image surface of Figure 2 (along the Tilt Axis) is determined by (subsequently described) successive calculation of the optical paths within the POD, allowing for appropriate depth of focus of the horizontal components. This reveals the effective tilt of the image plane which the incoming light must match to provide uniform horizontal focus over the entire image surface.
  • ⁇ is the image plane tilt angle
  • ⁇ is the object plane tilt angle (both with respect to the axis)
  • m is the image/object magnification. This, too, is separated into quadrature directions with appropriate subscripts to represent the individual magnifications and ⁇ -tilts.
  • Figure 3 is a section view of a generic POD (e.g. 205), showing its outline in bold solid lines and several (horizontal component) image surfaces.
  • the width (or horizontal) dimension appears in-and-out of the plane of the paper.
  • the axial dimensions are identified in the z-direction, as is the focal tolerance ⁇ Z.
  • the POD base thickness T corresponds to that in Figures 1 and 2. Illumination, propagating from left to right, traverses the keystone-correcting lens L t (not shown) and encounters the sloping base of the POD.
  • This ⁇ v tilt is determined by application of Equation (2) for the vertical component, after iterative determination of the tilt of the horizontal image surface ⁇ h and the tilt of the object plane ⁇ .
  • the object plane tilt must satisfy Equation (2) for both vertical and horizontal components; each having differing magnifications).
  • the locations and effective tilts of the horizontal image surfaces are established following the sequence of lines numbered (0) to (4), as follows:
  • n 1 refractive index material (air).
  • n 1.5 material (glass, plastic), it is extended by 1.5x to the viewing surface, line (0). This type of consideration allows the optical system to be calculated as though the image distances are completely in air.
  • line (4) is determined analytically as the surface to which cylinder lens C h must be focused such that with the additional keystone correcting lens L t , the image distance is shortened slightly to line (2) in air. It is then (per above) extended inside the higher index POD material to line ( 3) .
  • v h is taken to the vertical center of line (4) in Figure 3; effectively before the addition of telecentric lens L refocuses line (4) to line (2).
  • the image width is taken as greater than W by the ratio of vdonating to the distance from C to L .
  • L t is added, it is to collimate the principal rays of the focusing beams to width W.
  • the focal length of L would normally be taken as the distance from C Compute if there were no ⁇ -tilt of the object. With tilt, however, minor additional keystoning develops; accommodated by reducing the focal length of L t appropriately.
  • its focal length is shortened by approximately 12% to provide a rectilinear focused image.
  • PROJECTION OF SCANNED LASER BEAM(S) An alternate method of illuminating and addressing a POD-type display device, as expressed earlier, is by scanning a laser beam (or beams) in typical raster or line segment format, while modulating the intensity (or intensities) of the beam(s), and projecting the appropriately focusing array of beams into the display device to form an image.
  • This is a relatively conventional "laser projection system” in which a display screen is mounted typically perpendicular to the projection axis.
  • the vertical and horizontal image surfaces are not only disparate, but may be tilted with respect to the axis.
  • the scanned image can be considered for this application as integrated over time into a stationary image.
  • An analog to this process is, therefore, that of a photographic slide projector, as viewed from the principal plane of the projection lens to the screen. Everything before the lens is replaced by the scanned and modulated laser beam. Except for the diffraction-limited characteristics of coherent beam propagation, the flux from the aperture of the projection lens to the screen is analogous to the time-integrated flux during each frame of the scanned and modulated laser(s).
  • the above projection lens is identified as a "scan lens" of laser scanning vernacular. If the desired image spot size ⁇ is so small as to require an f- number F of the converging beam which is too low for its depth of focus ⁇ Z to straddle the disparate horizontal and vertical image planes, as governed by the relations,
  • this lens may be anamorphic. It is implemented with lens elements similar to C,h and Cv of the earlier discussions,' whereby the horizontal and vertical image components focus over different distances. With nominal focal distances established in a manner represented in Figure 3, and with horizontal and vertical laser beam scan angles into the lens determining width W and thickness T respectively, the specification of an appropriate projection lens is straightforward .
  • An alternative which maintains a more conventional flat field projection lens is to make the beam which illuminates the scanners appropriately astigmatic, such that the subsequently-scanned horizontal and vertical image components are projected to their proper disparate image planes. This is accomplished by placing an anamorphic lens element into the beam before the scanners.
  • Keystoning can be controlled in a manner discussed earlier; by adding a telecentric lens L t per Figure 2, to collimate the principal ray groups and to focus them at the center of line (2) of Figure 3.
  • the focal length of L t is determined by its distance to the effective nodal source of the projected beam.
  • Keystoning can also be nulled by predistorting the scanned function such that it forms a keystoned image which is complementary to that which would otherwise appear on the tilted display screen. This may be done by addressing low inertia laser scanners (e.g., acousto- optic or galvanometer deflectors) which are well known in the art to respond to variable rate electronic drive. This leaves only the correction of defocus (if required) appearing near the top and the bottom of the display.
  • Figure 4 shows laser 420, intensity modulating components 430, beam scanning components 440, and lens components C c and C y .
  • a method of providing focus on a sloping image plane is to replace cylindrical lens C h (e.g. of Figure 2) with a lens of conic cylindrical shape, C ; one shaped so that it reduces optical power gradually from “top” to "bottom". It is essentially a small portion of a (solid glass or plastic) cone which is cut therefrom such that its radius of curvature increases gradually from top to bottom, as shown in Figure 4a. This reduces optical power from top to bottom, gradually increasing horizontal focal length to match the tipped horizontal image plane.
  • FIG. 2 Another alternative which allows the laser scanned system to act more like that described earlier and illustrated in Figure 2, is to create a synthetic object plane which may be tilted for Scheimpflug correction.
  • This synthetic plane can be formed by having the laser scanner develop a real image in space; located essentially as is the Object in Figure 2.
  • the imaging process of Figure 2 may be duplicated by converging and propagating the flux through the lenses .
  • this disclosure identifies basic optical elements which in combination satisfy the objectives of the invention, it is understood that designs may be conducted by one skilled in the art to establish characteristics which satisfy such factors as variable (zoom) magnification, aberration reduction, optical efficiency, and production effectiveness. It is also understood that variations to the basic disciplines expressed here, such as the use of folding reflective and/or compound or cemented optical elements which may have equivalent Fresnel, reflective, diffractive or hybrid optical elements, remain within the scope of the principles of this invention.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Lenses (AREA)

Abstract

Certains systèmes optiques d'imagerie présentent des surfaces focales de l'image verticale et de l'image horizontale disparates, dont l'une d'entre elles au moins est inclinée par rapport à l'axe optique. L'optique de projection qui éclaire lesdits systèmes doit faire en sorte que les composants verticaux de l'image convergent sur la surface de l'image verticale nominale et que les composants horizontaux de l'image convergent sur la surface de l'image horizontale disparate. Comme au moins une de ces surfaces d'image peut être inclinée par rapport à l'axe de projection, une correction est nécessaire pour maintenir la convergence sur la totalité des surfaces et éviter la déformation trapézoïdale de l'image. Le système peut également nécessiter des agrandissements verticaux et horizontaux différents des images lorsque celles-ci sont projetées sur lesdites surfaces focales disparates. L'invention décrit, entre autres, les techniques permettant de satisfaire à ces diverses exigences: projeter un champ objet rectiligne dans un système dont les plans d'image sont inclinés et disparates.
PCT/IB1996/001129 1996-10-08 1996-10-08 Appareil et technique de projection optique WO1998015164A2 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
CA002305268A CA2305268C (fr) 1996-10-08 1996-10-08 Appareil et technique de projection optique
PCT/IB1996/001129 WO1998015164A2 (fr) 1996-10-08 1996-10-08 Appareil et technique de projection optique
EP96933567A EP0931275A4 (fr) 1996-10-08 1996-10-08 Appareil et technique de projection optique

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/IB1996/001129 WO1998015164A2 (fr) 1996-10-08 1996-10-08 Appareil et technique de projection optique

Publications (2)

Publication Number Publication Date
WO1998015164A2 true WO1998015164A2 (fr) 1998-04-16
WO1998015164A3 WO1998015164A3 (fr) 1998-08-27

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Application Number Title Priority Date Filing Date
PCT/IB1996/001129 WO1998015164A2 (fr) 1996-10-08 1996-10-08 Appareil et technique de projection optique

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EP (1) EP0931275A4 (fr)
CA (1) CA2305268C (fr)
WO (1) WO1998015164A2 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1240548A1 (fr) * 1999-12-21 2002-09-18 Scram Technologies, Inc. Systeme optique pour panneau d'affichage
EP1354244A1 (fr) * 2001-01-24 2003-10-22 Scram Technologies, Inc. Systeme optique pour panneau d'affichage
JP2007501446A (ja) * 2003-05-13 2007-01-25 スクラム テクノロジーズ インコーポレイテッド ディスプレイパネル用精密光学系
WO2009064467A1 (fr) * 2007-11-15 2009-05-22 Tharpe Christopher S Afficheur

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3212397A (en) * 1962-06-25 1965-10-19 Wendell S Miller Keystone-distortion controlling system
US5220363A (en) * 1988-09-14 1993-06-15 Casio Computer Co., Ltd. Projector
US5381502A (en) * 1993-09-29 1995-01-10 Associated Universities, Inc. Flat or curved thin optical display panel
US5422691A (en) * 1991-03-15 1995-06-06 Seiko Epson Corporation Projection type displaying apparatus and illumination system
US5455882A (en) * 1993-09-29 1995-10-03 Associated Universities, Inc. Interactive optical panel

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5016964A (en) * 1989-10-04 1991-05-21 Spectranetics Corporation Optical fiber coupler with linear input
JPH07159721A (ja) * 1993-12-08 1995-06-23 Sony Corp プロジェクター

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3212397A (en) * 1962-06-25 1965-10-19 Wendell S Miller Keystone-distortion controlling system
US5220363A (en) * 1988-09-14 1993-06-15 Casio Computer Co., Ltd. Projector
US5422691A (en) * 1991-03-15 1995-06-06 Seiko Epson Corporation Projection type displaying apparatus and illumination system
US5381502A (en) * 1993-09-29 1995-01-10 Associated Universities, Inc. Flat or curved thin optical display panel
US5455882A (en) * 1993-09-29 1995-10-03 Associated Universities, Inc. Interactive optical panel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0931275A1 *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1240548A1 (fr) * 1999-12-21 2002-09-18 Scram Technologies, Inc. Systeme optique pour panneau d'affichage
EP1240548A4 (fr) * 1999-12-21 2008-03-19 Scram Technologies Inc Systeme optique pour panneau d'affichage
EP1354244A1 (fr) * 2001-01-24 2003-10-22 Scram Technologies, Inc. Systeme optique pour panneau d'affichage
EP1354244A4 (fr) * 2001-01-24 2008-03-19 Scram Technologies Inc Systeme optique pour panneau d'affichage
JP2007501446A (ja) * 2003-05-13 2007-01-25 スクラム テクノロジーズ インコーポレイテッド ディスプレイパネル用精密光学系
WO2009064467A1 (fr) * 2007-11-15 2009-05-22 Tharpe Christopher S Afficheur

Also Published As

Publication number Publication date
CA2305268A1 (fr) 1998-04-16
EP0931275A4 (fr) 2000-03-01
EP0931275A1 (fr) 1999-07-28
WO1998015164A3 (fr) 1998-08-27
CA2305268C (fr) 2005-12-27

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