WO2000070376A1 - Systeme optique pour produire une image couleur modulee - Google Patents

Systeme optique pour produire une image couleur modulee Download PDF

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Publication number
WO2000070376A1
WO2000070376A1 PCT/US2000/013063 US0013063W WO0070376A1 WO 2000070376 A1 WO2000070376 A1 WO 2000070376A1 US 0013063 W US0013063 W US 0013063W WO 0070376 A1 WO0070376 A1 WO 0070376A1
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Prior art keywords
spectrum
optical system
color
beamsplitter
light
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PCT/US2000/013063
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English (en)
Inventor
Gary D. Sharp
Michael G. Robinson
Jonathan R. Birge
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Colorlink, Inc.
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Publication date
Application filed by Colorlink, Inc. filed Critical Colorlink, Inc.
Priority to AU48449/00A priority Critical patent/AU4844900A/en
Priority to JP2000618759A priority patent/JP4637370B2/ja
Publication of WO2000070376A1 publication Critical patent/WO2000070376A1/fr

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
    • G02B27/283—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising used for beam splitting or combining

Definitions

  • the present invention relates to image formation, and more particularly, to optical systems which employ color-selective polarizing elements for forming color images.
  • Optical projection systems in the related art use transmissive thin-film- transistor (TFT) liquid crystal display (LCD) panels.
  • TFT thin-film- transistor
  • LCD liquid crystal display
  • Multi-layer evaporated thin- film dichroic beamsplitters that are tilted with respect to the axis of incident light are used to create physically distinct paths, each representing the spectral power in one portion of an additive primary color band red-green-blue (RGB).
  • RGB red-green-blue
  • An LCD in each path controls the local light transmission level of a particular primary color band.
  • Modulated or imagery light is recombined with additional tilted isotropic coatings and full-color imagery is projected onto a front or rear projection screen.
  • the LCD In transmissive systems, the LCD is positioned between crossed polarizers as an approach to obtain high contrast ratios for most LC electro-optic modes.
  • the analogous configuration is to position a polarizing beamsplitter (PBS) directly in front of the panel, as described in a parent application, incorporated by reference above.
  • PBS polarizing beamsplitter
  • One type of polarization beam splitter is a tilted thin-film stack with four ports, which reflects or transmits a light spectrum based on its polarization.
  • a PBS ideally functions as a broad-band reflector for a light spectrum polarized along one axis, and as a transmitter for a light spectrum polarized along an orthogonal axis.
  • a dichroic beamsplitter ideally reflects or transmits a light spectrum based only on the wavelength of the light.
  • a full-color split-path projector may use reflective LCD panels, with dichroic beamsplitters for creating three color paths, a polarizing beamsplitter for each reflective LCD panel, and additional optics for recombining the imagery before the projection lens.
  • Such implementations are cumbersome and expensive.
  • DNF double notch filter
  • Multi-layer thin-film coatings are used in the related art for manipulating color in projection display systems. This technology is well matched to the high efficiency and high power handling requirements of projection. Moreover, the steep transition slopes desired to maximize luminance, while meeting color coordinate standards, can be achieved. However, tilted isotropic coatings can degrade polarization quality, particularly in low f-number systems. In LCDs, polarization must be accurately preserved in order to achieve low dark state leakage. Furthermore, dichroic mirrors have an angle sensitive half-power wavelength that shifts substantially with incidence angle. In order to create physically distinct color paths using a dichroic mirror, the layers are often substantially tilted with respect to the axis of incident light.
  • Reflective silicon display panels are readily known in the related art. The most common reflective silicon display panels are VLSI-based active-matrix panels that are processed to have a high or flat fill factor, and high visible reflectivity.
  • polysilicon panels can be made to function as reflective displays.
  • VLSI-based panels a thin liquid crystal film is sandwiched between the silicon chip and a cover glass coated with a transparent conductor, typically indium tin oxide (ITO).
  • ITO indium tin oxide
  • the liquid crystal can be either a nematic or smectic material, both of which are well documented in the art.
  • the liquid crystal is an anisotropic medium, which responds to an electric field by changing its orientation. This in-turn changes the polarization state of light propagating through the liquid crystal.
  • FIGs 1(a) and 1(b) illustrate related art reflective display architectures where light having a single polarization state is introduced.
  • light enters a polarizing beamsplitter (PBS) 10 through a first port 12, and is reflected out a second port 14 towards a reflective LCD panel 20.
  • PBS polarizing beamsplitter
  • the light reflects the light back through the second port 14 and the PBS 10, where the light exits via a third port 16.
  • the light enters the PBS 10 through the third port 16 travels through the PBS 10, and exits through the second port 14.
  • the LCD panel 20 reflects the light back through the second port 14, where the light is reflected by the PBS 10 and exits via the first port 12.
  • the polarization state of reflected light is locally modulated via the voltage dependent distribution of the LC molecules at each pixel of the LCD panel 20.
  • This polarization encoded imagery is converted to an actual gray shade image using an analyzing polarizer.
  • light is introduced and analyzed using the PBS 10.
  • the PBS 10 effectively positions the LCD panel 20 between crossed polarizers , and also directs light through the system and ultimately to projection lenses.
  • An object of the present invention is to substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
  • Another object of the present invention is to reduce the complexity and cost while increasing contrast ratio and throughput of reflective LCD systems. Still another object of the present invention is to reduce the f-number in color management systems while maintaining contrast ratio.
  • the present invention can be achieved, in whole or in part, by an optical system including an input retarder that transforms a first spectrum of input light from a light source along a first polarization state, and transforms a second spectrum of the input light from the light source along a second polarization state different than the first polarization state, and a beam splitting unit, optically coupled to the input retarder, and including a first beamsplitter that transmits the first spectrum as a transmitted spectrum, and that reflects the second spectrum as a reflected spectrum.
  • the present invention can also be achieved, in whole or in part, by a system that divides input light from a light source into component color bands, red, green, and blue by making the colors travel different physical paths.
  • each color band can be independently processed.
  • processed light can be combined to form a single path, again using a retarder stack (RS) and a PBS.
  • RS retarder stack
  • PBS polarization beamsplitter
  • the present invention can also be achieved, in whole or in part, by merging color and polarization management to produce a split-path projector, based on reflective display panels, that is simple in construction.
  • Retarder stack (RS) components create orthogonally polarized primary colors from a polarized input.
  • a PBS functions as a color splitter, allowing all four ports of the PBS to be utilized.
  • the port containing the subtractive primary band can be further split using a dichroic beamsplitter.
  • all three paths are recombined and analyzed by the input PBS.
  • Full-color imagery can exit the previously unused fourth port of the PBS.
  • a full-color projector according to the present invention would therefore require only one PBS coating and one dichroic color splitter coating, along with one or two retarder stacks.
  • the present invention can further be achieved, in whole or in part, by improving polarization management associated with color optical systems to provide a high contrast ratio.
  • the reduced angle sensitivity exhibited by the retarder stacks of the present invention, relative to dichroic splitters, also results in the projectors of the present invention having high contrast ratios.
  • the present invention can also be achieved, in whole or in part, by providing a wide color gamut with minimal hardware.
  • An aspect of the invention is the recognition that an exit retarder stack, used to manage light leakages from the PBS, can also be used to generate inter-band notch filtering operations. This eliminates the need for an auxiliary notch filter, which is used frequently with related art systems that utilize the Philips prism. Using different input and exit retarder stacks, inter-primary light, such as that produced by a metal halide lamp, can be diminished or eliminated by the exit clean up polarizer. This eliminates the need for a separate double notch filter (DNF).
  • DNF double notch filter
  • the present invention can still further be achieved, in whole or in part, by providing an optical system, such as a reflective LCD projector, that exhibits high overall throughput, or brightness. This is achieved by manipulating color bands with stacks of lossless polymer retarder films, by providing refractive index matching between the retarder films, and by minimizing the number of lossy polarizers. It is further accomplished by eliminating the need for an auxiliary filter for eliminating inter-primary light. Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
  • Figures 1(a) and 1(b) illustrate related art reflective display architectures, where light of a single polarization is introduced through a first port and is transmitted through a second port towards a reflective LCD panel;
  • Figure 2 shows a retarder stack and PBS polarization-based color splitter, in accordance with a preferred embodiment of the present invention
  • FIG. 3 illustrates an optical system, in accordance with another preferred embodiment of the present invention.
  • Figure 4 illustrates an optical system including a three panel reflection display system, in accordance with yet another preferred embodiment of the present invention
  • Figure 5 illustrates another optical system including a three panel reflection display system, in accordance with still another preferred embodiment of the present invention
  • Figure 6 illustrates an equivalent unfolded arrangement of the three-panel reflective display system of Figure 5, with the reflective display system in the off-state;
  • Figure 7 illustrates another equivalent unfolded arrangement of the three-panel reflective display system shown in Figure 5, with the reflective display system in the off-state
  • Figure 8 illustrates an equivalent unfolded arrangement of the three-panel reflective system of Figure 5, with the reflective display system in the on-state
  • Figure 9 illustrates a transition band for the reflective display system of Figure 5
  • Figure 10 shows light leakage through the reflective display system of Figure 5, when the reflective display system is in the off-state
  • FIGS 11, 12, 13 and 14 show measured output of the reflective display system of Figure 5;
  • Figure 15 illustrates a modification of the optical system shown in Figure 4, in accordance with the present invention
  • Figure 16 illustrates an optical system including a three panel reflective display system, in accordance with another preferred embodiment of the present invention.
  • FIG. 2 shows polarization based color splitter 45 that can produce two polarized color paths in accordance with the present invention.
  • the color splitter 45 comprises a retarder stack (RS) 30 and polarizing beamsplitter (PBS) 40. Details of the construction and operation of retarder stack 30 are found in the parent applications, incorporated by reference above. In operation, polarized input light from a light source (not shown) is directed to retarder stack 30.
  • RS retarder stack
  • PBS polarizing beamsplitter
  • An optional polarizer 50 can be used if the input light is unpolarized, or to improve the contrast ratio of polarized input light.
  • the retarder stack 30 receives the polarized input light and converts the polarization of a primary color to one polarization state S( ⁇ ) and converts the polarization of its complementary color to an orthogonal polarization state (1-S( ⁇ )).
  • the PBS 40 is oriented so that the complementary color is reflected by the PBS 40 and the primary color is transmitted by PBS 40.
  • FIG. 3 illustrates a projection system 55, in accordance with one embodiment of the present invention.
  • the projection system 55 includes input and output retarder stacks 60,80, reflective spatial light modulators 65, 75, a PBS 70 and a cleanup polarizer 90.
  • the reflective spatial light modulators 65, 75 are liquid crystal spatial light modulators.
  • any reflective spatial light modulator can be employed in this embodiment and in later embodiments where reflective liquid crystal spatial light modulators are shown for illustrative purposes.
  • at least partially polarized input light propagates through the input retarder stack 60, which polarizes a primary color along one polarization state and its complementary color along an orthogonal polarization state.
  • the retarder stacks 60 and 80 are optically coupled to the polarizing beam splitter.
  • optically coupled refers to any configuration in which light passing through or reflected from an optical element is incident on a second optical component either directly or through one or more intermediate optical elements.
  • light transmitted through the stack is incident on PBS 70 through a first port and a first one of the colors is reflected by the PBS 70 through a second port.
  • the polarizing beam splitters of the present invention are selected from any optical element which can separate light of different polarizations and, in particular, to devices which can separate orthogonally polarized states of light and direct them along substantially orthogonal output paths.
  • the primary color spectrum is modulated and reflected by the LCD 65 through the second port, into PBS 70, where it is output via a third port.
  • the complementary color spectrum is transmitted through the PBS 70 through a fourth port, and is modulated and reflected by the LCD 75 back towards the PBS 70.
  • the PBS 70 reflects the complementary color spectrum, which exits via the third port with the primary color spectrum.
  • the light propagates through an output retarder stack 80 which encodes both the primary color spectrum and the complementary color spectrum along the same polarization state. Then a clean-up polarizer 90 polarizes the light to improve its contrast ratio and to block cross-talk light prior to output.
  • Figure 3 shows that PBS leakage can be minimized by placing an output retarder stack 80 at the exit port. This restores the desired light to a single polarization state, allowing the clean-up polarizer 90 to block all cross-talk light.
  • Figure 4 illustrates an optical system 100 in accordance with yet another embodiment of the present application.
  • the system 100 includes a first beamsplitter 110, color separator 120, first, second and third reflective modulators 130, 140, 150; first and second retarders stacks 160, 170; first and second clean-up polarizers 190, 195; a polarization conversion array 185; first and second optic lenses 180, 182 and a light source 175. While individual lenses 180 and 182 are schematically depicted in FIG.
  • the beamsplitter 110 is a PBS that transmits or reflects the light based on the polarity of the light
  • the color separator 120 is typically a dichroic beamsplitter that transmits or reflects light based on the wavelength of the light.
  • the first, second and third reflective spatial light modulators 130, 140, 150 are, in a preferred embodiment, selected from liquid crystal modulators, and can be nematic on silicon, or FLC on silicon.
  • the light source 175 is an incandescent lamp, laser, light emitting diode
  • LED ultra-high pressure metal halide lamp
  • UHP ultra-high pressure mercury lamp
  • fusion lamp or another source of light.
  • light from the light source 175 is collimated, and may undergo polarization conversion at the polarization conversion array 185, before being polarized by the first clean-up polarizer 190.
  • the first retarder stack 160 encodes a first primary color along one polarization state and its complementary color along an orthogonal polarization state.
  • the complementary color is reflected and the primary color is transmitted by the beamsplitter 110.
  • the color separator 120 separates the reflected complementary color into second and third primary colors, which are spatially modulated by the first and second reflective modulators 130, 140.
  • the first primary color is spatially modulated by the third reflective modulators 150.
  • the first, second, and third primary colors are spatially modulated by polarization of the light in accordance with image information being supplied to each reflective modulator 130, 140, 150.
  • the separated light is then recombined.
  • the spatially modulated second primary colored light is transmitted through color separator 120 and beamsplitter 110, respectively.
  • the spatially modulated third primary colored light is reflected by the color separator 120 and transmitted through the first beamsplitter 110.
  • the spatially modulated first primary colored light is reflected by the first beamsplitter 110.
  • the second and third primary colored lights are recombined to form a spatially modulated complementary color, and is transmitted with the spatially modulated first primary color through a second retarder stack 170, that rotates the spectrum of S polarized first primary color into p polarized light and leaves the p polarization spectrum of the complementary color undisturbed.
  • the first primary color spectrum and the complimentary color spectrum merge to form modulated white light which passes through the second clean-up polarizer 195, and is then output through the projection optic lens 182.
  • Each primary color of the modulated white light has equal path lengths through the system 100.
  • Figure 5 illustrates another three-panel reflective optical system in accordance with still another preferred embodiment of the present invention.
  • Figure 6 illustrates an unfolded arrangement of the three-panel reflective optical system of Figure 5, in an off-state, for ease of polarization tracing.
  • input white light from the light source may be linearly polarized using a polarization conversion array (not shown) to enhance efficiency and polarized by a cleanup polarizer (not shown).
  • the first retarder stack 160 here an input green/magenta (IGM) stack, transits the input white light with green light polarized orthogonal to blue and red light.
  • IGM input green/magenta
  • green light exits the IGM p polarized, and the inverse spectrum, or complementary colored magenta light is S polarized.
  • the beamsplitter 110 which in this example is a PBS, transmits only green light, and reflects magenta light.
  • the reflecting modulators 130, 140, 150 which, for this example, are red, blue, and green LCDs, respectively, with no change in the state of polarization (SOP).
  • Red and blue light are split by the color separator, which in this example is a dichroic splitter, such that blue B, and true cyan C are reflected to the second reflection modulator 140 (blue LCD), and true yellow Y and red R are transmitted to the first reflection modulator 130 (red LCD).
  • the reflected light returns with no change in the SOP and recombines at the color separator 120.
  • Light returning to the beamsplitter 110 remains S polarized, and is therefore efficiently reflected by the beamsplitter 110. Thus all light exits the input port and the contrast ratio is very high to this level of approximation.
  • the first beamsplitter 110 has finite polarization efficiency.
  • the leakage of P polarized light into the S-port is substantially larger than the leakage of s polarization into the P-port often by a factor of ten, at normal incidence.
  • Figure 7 illustrates light leakage through the system shown in Figure 5, when the optical system is in the dark (off) state, under the assumption that e s can be neglected relative to e p .
  • green light transmitted by the first beamsplitter 110 with transmission (l-e p ) is reflected by the third reflective modulator 150 with no change in the SOP. It is analyzed by the first beamsplitter and leaks e p (l-e p ) into the output port.
  • Green input light (e p ) reflected by the first beamsplitter 110 is split by the color separator (dichroic splitter) 120 and is returned by the first and second reflective modulators 130,140 with no change in the SOP.
  • the green input light reflected by the first beamsplitter (PBS) 110 is then combined by the dichroic splitter and returns to the PBS 110.
  • This p polarized light is transmitted by the PBS 110 with leakage e p (l-e p ), and is combined with the leakage from other parts of the system. Due to the lack of system coherence, these components essentially combine on a power basis.
  • Light comprising the inverse spectrum (or complementary color) is efficiently reflected by the PBS 110, and is assumed to contribute relatively little to the system contrast ratio.
  • a second retarder stack 170 here an output green/magenta (OGM) stack is placed at the output port along with the clean-up polarizer 195 that is crossed with the input polarizer.
  • the second retarder stack 170 converts p polarized light transmitted by the PBS 110 to s polarized light, with no effect on blue and red. The green leakage can subsequently be blocked by the clean-up polarizer 195.
  • Figure 8 illustrates an unfolded arrangement of the three-panel reflective system of Figure 5, with the system in the white (on) state.
  • the light transitions in Figure 8 differ from the light transitions in Figure 6 because the first, second and third reflective modulators 130, 140, 150 modulate and polarize the light orthogonally to the SOP of the input light.
  • the spectrum reflected by the first reflective modulator 130 is transmitted by the color separator 120, which in this example of the preferred embodiment is a dichroic beamsplitter, and is combined with the spectrum reflected by the second reflective modulator 140.
  • the combined spectrum which is the complementary color of the first primary color, is transmitted through the first beamsplitter 110, the second retarder stack 170 and the second cleanup polarizer 195.
  • the spectrum reflected by the third reflecting modulator 150 is reflected by the first beamsplitter 110 and joins the complementary colored combined spectrum.
  • the spectrum of the primary color is then polarized by the second retarder stack such that its SOP matches the SOP of the light of the complementary color, and exits the system.
  • the R,Y colored light is modulated by the red LCD (first reflected display 130), and the B,C colored light is modulated by the blue LCD (second reflective display 140).
  • all four colors enter the first beamsplitter 110 in the return path P polarized.
  • the first beamsplitter 110 reflects all s polarized green light, and transmits all p polarized (BCYR) light.
  • the second retarder stack 170 differs in design from the first retarder stack 160 (IGM).
  • the OGM has a broader magenta notch than the IGM, such that a substantial portion of power in the C and Y band is rotated by 90°.
  • the OGM has the dual function of restoring the SOP of green light for maximizing contrast ratio, and for dumping a portion of the C and Y band to improve the color gamut.
  • green light is not transmitted through tilted isotropic coatings in the path between the first beamsplitter 110 and the third reflective modulator 150. This maximizes contrast in the green light, which has the greatest impact on system level contrast ratio.
  • green light effectively passes through four titled isotropic stacks. The result, with the Philips prism, is a loss in polarization fidelity, particularly for rays that do not lie in the plane containing the stack normal (s rotations).
  • reflected light from the first beamsplitter 110 impinges on the color separator 120, which here is a dichroic splitter (mirror) preferably designed to have a half-power point in the green color.
  • Element 120 separates and combines blue light and red light. The elimination of green light from this port relaxes the performance requirements on color separator 120 but does not establish transition band characteristics since there is no light present in the transition band. As such, spectral shifts of a few degrees cause relatively little cross- talk between the first and second reflecting modulators 130, 140 (red and blue LCDs), and therefore relatively little loss in color performance.
  • Polarization modulated light from the first and second reflective modulators 130, 140 is recombined by element 120 and is then analyzed by the beamsplitter 100.
  • the color separator is typically a dichroic splitter which functions as a color selective mirror that reflects substantially all of one primary band and transmits substantially all of the complementary primary band. Though often steep, there is a finite transition band in which portions of a spectral component are both transmitted and reflected. Because the mirror is tilted with respect to the axis of incident light, the dichroic splitter can be considered to have linear Eigenstates. The characteristics can thus be extracted by probing the transmitted/reflected fields with polarizations parallel and perpendicular to the plane of incidence.
  • Dichroic mirrors typically have transition bands for s and p polarizations that are non-overlapping. This separation depends upon the center wavelength, the specific stack design and the incidence angle. Far from the transition band, where substantially all light is reflected or transmitted, the structure has no effect on the degree of polarization. However, within the band that separates the two transmission spectra, the structure behaves like a polarizing beamsplitter.
  • this light is rejected by the fourth port of the dichroic splitter.
  • this band encroaches on the primary color bands at angles within the f-number of the system, significant transmission losses can result.
  • a dichroic splitter has substantially zero polarizing properties (10-15 nm separation of the half- power point), to minimize the transition bandwidth for the combined S and p spectra, which maximizes throughput of blue and red light with the lowest f-number.
  • the first retarder stack 160 (IGM) encodes green along one polarization state and magenta along an orthogonal polarization state. Then the first beamsplitter 110, as a polarizing beamsplitter, transmits green light and reflects magenta, and thus eliminates the green portion of the spectrum from the port containing the second (dichroic) splitter 120.
  • the dichroic splitter transition band is positioned in the green such that the angle sensitivity has no effect on the chrominance of each output, as shown in Figure 9, which illustrates the transition band of the preferred embodiment shown in Figure 5.
  • the preferred dichroic splitter has a half- power point substantially centered in this band, such that reflectivity of blue (or red), and transmission of red (or blue) remain high over the entire f-number of the system.
  • light that falls in transition bands of the first and second retarder stack 160, 170 is shared between two ports of the first beamsplitter 110, as illustrated in Figure 9.
  • the polarization of light occurring at strong source emissions is controlled to maximize system contrast ratio.
  • This interaction is illustrated in the following example in which identical stacks are used in both the input and exit ports.
  • power is ideally divided evenly by the first PBS beamsplitter 100.
  • the SOP generated by the stack is 45° linear, but can be any SOP that has equal projections along the PBS eigenpolarizations.
  • p polarized light leaks into the output port of the PBS 110 from both green and magenta ports.
  • the second retarder stack 170 rotates the leakage light by a non-optimum 45°. As such, substantially half of the leakage light is passed by the clean-up polarizer. Contrast can quickly degrade to about 10: 1 at this wavelength.
  • contrast ratio is maximized by creating first and second retarder stacks that optimally manage the SOP of off-state light that leaks through the first PBS beamsplitter (110).
  • One approach to increase contrast includes raising the transition slope with additional films, and moving the transition band away from strong source emissions.
  • a preferred approach is to create the first retarder stack
  • both the first and second retarder stacks 160, 170 have zero-overlap.
  • An example full-color three-path projector in accordance with the preferred embodiment demonstrates both contrast ratio and color enhancement.
  • the orientations of both stacks are symmetric about the same wavelength, and therefore the notch characteristics in cyan and yellow are fundamentally the same.
  • the retardation is 1.5 waves at 545 nm, and is preferably 535 nm. Though slightly red shifted from optimum, the interaction between the stacks is wavelength invariant and the example thus serves to demonstrate the embodiment.
  • This example of the preferred embodiment includes a quartz-halogen lamp as the light source 175 followed by a dye-stuff S-oriented polarizer as the first cleanup polarizer 190. The output was measured using an optical spectrum analyzer (not shown). The demonstration was assembled using free-standing antireflection (AR) coated components.
  • the first and second retarder stacks 160,170 have pressure sensitive adhesive cemented between broad-band anti-reflection coated windows and attached to input and output ports of the first beamsplitter 110.
  • a red/blue dichroic mirror plate as the second beamsplitter 120, is located parallel to the PBS coating of the first beamsplitter 100, to accept S polarization light.
  • Reflective modulators 130, 140, 150 were formed by laminating retardation films to aluminum mirrors with a quarter wave retardation at 500 nm (blue), 560 nm
  • Figures 11, 12, 13 and 14 show measured output of the reflective optical in accordance with a preferred embodiment of the present invention, as measured by the optical spectrum analyzer.
  • the measurements clearly demonstrate the notches in the yellow and cyan colors.
  • On-axis contrast ratios are high throughout the visible spectrum, for example, greater than about 500:1.
  • the on-axis color gamut is far in excess of that required by the SMPTE standards, and the preferred embodiment combines color gamut and system brightness. Even greater increases in brightness are obtainable by sacrificing color coordinates.
  • One preferred approach for increasing brightness is by increasing the transition slope of the first and second retarder stacks 160, 170, or by decreasing the notch density, by designing the first and second retarder stacks 160, 170 with greater transition band overlap while avoiding increased off-state leakage of inter-primary light.
  • Another preferred approach for increasing brightness is to use different retardation values for the first and second retarder stacks 160,170. Since the designs are not symmetric about the same wavelength, different notch densities can be obtained in the cyan and yellow. In some cases, adequate color coordinates can be obtained by completely avoiding a cyan notch, for example, by blocking 80%-90% of 578 nm light.
  • the density of the notch is determined by the difference in duty ratio, which here is measured as the relative width of the green notch between the first and second retarder stacks 160, 170 and the transition slope.
  • both stacks include 14 layers of films adjacently stacked, giving a transition slope that discriminates between the green line (545 nm) and the yellow line (578 nm) of a light source 175. This approach thus provides a high degree of blocking in each notch.
  • the first minimum of the green output of the first retarder stack 160 coincides with the first minimum of the magenta output of the second retarder stack 170, thereby providing dense blocking in the magenta notch.
  • the magenta output of the second retarder stack 170 has 85% transmission at 491 nm, and 619 nm.
  • the preferred embodiments of the present invention provide an additional benefit of using retarder stack (RS) technology to create and combine color paths for reduced angle sensitivity.
  • RS retarder stack
  • Related art color splitters such as dichroic mirrors, cholesteric films, and holographic mirrors, create two physical paths, and determine the transition band characteristics.
  • An RS 160,170 encodes color by polarization, and can thus determine the transition band characteristics, but a RS 160,170 does not physically separate the co-linearly propagating field components. As such, light is introduced substantially normal to the stack, thereby minimizing angle sensitivity.
  • the retardance shift for small excursions from normal incidence is a second order in angle.
  • the first (PBS) coatings used to create the color paths are substantially tilted (typically with a bias angle of 45 °)
  • the preferred embodiment provide neutral polarizing efficiency over the f-number of the systems. By separating the two functions, a significant decrease in angle sensitivity is provided.
  • a substantially insignificant angle insensitive retardation can be achieved using either a compound retarder, or a single biaxial retarder.
  • a biaxial retardation film can be formed by stretching a polymer substrate both in-plane and along the film normal. When the retardation along the film normal is substantially half of the in-plane retardation, the wavelength shift with incidence angle becomes substantially insignificant.
  • Table 2 shows measured data on the second retarder stack alone between parallel polarizers.
  • results show that the dominant spectral shifts are toward the red, with 0.5 nm maximum shift for a 15° half-cone angle.
  • the first beamsplitter 110 represents the limiting factor in color separation performance.
  • Figure 15 illustrates a three panel reflective optical system 102 in accordance with still another preferred embodiment of the present invention.
  • This preferred embodiment includes the features discussed above in relation to Figure 4, and also includes a first and a second light doubler 115, 125 for increasing the intensity of the light, as it passes through the reflective optical system 102.
  • the first and second light doublers 115, 125 are preferably inverters, which increase the intensity of the light for ferroelectric liquid crystal displays.
  • white light from the light source 175 is polarized by the first cleanup polarizer 190 and is encoded by the first retarder stack 160 to align a first primary color along one polarization state and its complementary color along an orthogonal polarization state.
  • the first primary color is transmitted by the first beamsplitter 110, and travels through a portion used to balance the optical paths of the separated beams. Then the first primary color is transmitted by the first light doubler 115, is spatially modulated by the third reflective modulator 150, and is transmitted back through the first light doubler 115.
  • the first primary color is reflected by the first beamsplitter 110, and exits the system through the second retarder stack 170, the second cleanup polarizer 195, and if needed, the second projection optics 182.
  • the complementary color of the first primary color is reflected by the first beamsplitter 110, and is split into the second and third primary colors after being transmitted by the second light doubler 125.
  • the second primary color is then reflected by the color separator 120, is spatially modulated by the second reflective modulator 140, and is again reflected by the color separator 120 to be transmitted by the second light doubler 125.
  • the third primary color is transmitted by the color separator 120, is spatially modulated by the first reflective modulator 130, and is again transmitted by the color separator 120.
  • the second and third primary colors are combined and transmitted by the second light doubler 125, and the first beamsplitter 110 to exit the system 100 through the second retarder stack 170.
  • the second retarder stack 170 transmits the combined complementary color and the first primary color having the same polarization state, through the second cleanup polarizer 195 and second projection optics 182.
  • an intermediate retarder stack may be optionally positioned between the beamsplitter 110 and the color separator 120 in the embodiment of Figure 4.
  • Figure 16 illustrates an optical system 200 in accordance with yet still another preferred embodiment of the present invention, including first, second, third and fourth polarizing beamsplitters 205, 210, 215, 220; and first, second, third and fourth retarder stacks 260, 265, 270, 275.
  • first, second and third primary colors will be hereinafter referred to as blue, red and green, respectively.
  • the colors are_used for example purposes, as a skilled artisan would readily understand that the order of the colors can be changed as desired.
  • White light from a light source 175 is polarized by the first retarder stack 260 such that blue light is polarized along one polarization state and its complementary color, yellow light is polarized to an orthogonal polarization state.
  • the first polarized beamsplitter (PBS) 520 transmits blue and reflects yellow.
  • the first and second reflective modulators 130, 140 modulate red and green light, respectively.
  • the second PBS 210 then transmits the red light and reflects the green light.
  • the third retarder stack 270 recombines the red and green light into one polarization state that is transmitted by the third PBS 215 through the fourth retarder stack 275.
  • the fourth PBS 220 transmits the blue light from the first PBS 205 to the third reflective modulator 150, which modulates and reflects the blue light back to the fourth PBS 220.
  • the fourth PBS 220 reflects the blue light to the third PBS 215, which reflects the blue light to the fourth retarder stack 275.
  • the fourth retarder stack 270 ' rotates all three primary colors, red, green and blue into the same polarization state and outputs the combined spectrum.
  • the color splitting and combining structure and methods of the preferred embodiments of the present application creates separate color paths using stack retardation films and neutral polarization splitters. It is for use in reflective split-path projectors and applies in particular to reflective liquid crystal on silicon displays.
  • Retarder stack (RS) technology is used to provide separation of color via polarization. When combined with structures that create physically distinct paths from orthogonal polarizations, color splitting is accomplished. Retarder stacks generate flat passband and stopband profiles, narrow transition bandwidths, and low color cross-talk. Unlike related dichroic beamsplitters, RS technology is based on polarization. This allows a merging of color and polarization management in projectors which is integral to the compact architectures described herein.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Liquid Crystal (AREA)
  • Projection Apparatus (AREA)

Abstract

L'invention concerne un système optique qui permet de diviser une source lumineuse selon ses bandes couleur constitutives, rouges, vertes et bleues, la lumière à parcourant différents trajets physiques. Au moins deux de ces trajets utilisent des pellicules de retard en pile (60, 80) et un séparateur de faisceaux de polarisation (74). La création de trajets distincts permet de traiter chaque code séparément et de les combiner pour former un trajet unique utilisant un séparateur de polarisation et une pile de retardateurs. De préférence, le système comporte un retardateur d'entrée qui aligne un premier spectre d'une lumière provenant d'une source lumineuse, avec un premier état de polarisation, puis un second spectre de lumière provenant de la source lumineuse, avec un second état de polarisation, différent du premier; une unité de séparation de faisceaux, couplée de manière optique au retardateur d'entrée, et comprenant un premier séparateur de faisceau qui émet le premier spectre, en tant que spectre émis, et qui réfléchit le second spectre, en tant que spectre réfléchi. L'unité de séparation de faisceau combine le spectre émis modulé et le spectre réfléchi modulé en spectre combiné.
PCT/US2000/013063 1999-05-14 2000-05-12 Systeme optique pour produire une image couleur modulee WO2000070376A1 (fr)

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AU48449/00A AU4844900A (en) 1999-05-14 2000-05-12 Optical system for producing a modulated color image
JP2000618759A JP4637370B2 (ja) 1999-05-14 2000-05-12 変調カラー画像を形成するための光学システム

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US60/134,223 1999-05-14

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JP2002303932A (ja) * 2001-04-09 2002-10-18 Ricoh Co Ltd 投影装置
EP1459113A1 (fr) * 2001-11-30 2004-09-22 Colorlink, Inc. Systemes et procedes de gestion de couleur compensee
JP2005506576A (ja) * 2001-10-24 2005-03-03 ロリク　アーゲー 切替可能なカラーフィルタ
WO2005081039A1 (fr) * 2004-02-03 2005-09-01 3M Innovative Properties Company Separateur de faisceau polarisant comprenant un adhesif sensible a la pression
US7008064B2 (en) 2002-11-05 2006-03-07 Elcos Microdisplay Technology, Inc. Two panel optical engine for projection applications
JP2006133802A (ja) * 1999-09-17 2006-05-25 Hitachi Ltd 映像表示装置
US7315418B2 (en) 2005-03-31 2008-01-01 3M Innovative Properties Company Polarizing beam splitter assembly having reduced stress
US7385582B2 (en) 2002-08-23 2008-06-10 Edwin Lyle Hudson Temperature control and compensation method for microdisplay systems
US7649626B2 (en) 2002-04-18 2010-01-19 Qinetiq Limited Imaging spectrometer
US9784985B2 (en) 2011-10-24 2017-10-10 3M Innovative Properties Company Titled dichroic polarizing beamsplitter
US11538431B2 (en) 2020-06-29 2022-12-27 Google Llc Larger backplane suitable for high speed applications
US11568802B2 (en) 2017-10-13 2023-01-31 Google Llc Backplane adaptable to drive emissive pixel arrays of differing pitches
US11626062B2 (en) 2020-02-18 2023-04-11 Google Llc System and method for modulating an array of emissive elements
US11637219B2 (en) 2019-04-12 2023-04-25 Google Llc Monolithic integration of different light emitting structures on a same substrate
US11710445B2 (en) 2019-01-24 2023-07-25 Google Llc Backplane configurations and operations
US11810509B2 (en) 2021-07-14 2023-11-07 Google Llc Backplane and method for pulse width modulation
US11847957B2 (en) 2019-06-28 2023-12-19 Google Llc Backplane for an array of emissive elements
US11961431B2 (en) 2018-07-03 2024-04-16 Google Llc Display processing circuitry

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110031977A (zh) * 2019-03-18 2019-07-19 惠州市华阳多媒体电子有限公司 一种基于偏振分光的双屏显示系统

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5959773A (en) * 1997-08-20 1999-09-28 Hughes-Jvc Technology Corporation Parallel plate beam splitter configuration in high index glass

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5751384A (en) * 1995-05-23 1998-05-12 The Board Of Regents Of The University Of Colorado Color polarizers for polarizing an additive color spectrum along a first axis and it's compliment along a second axis
JP3370010B2 (ja) * 1999-03-31 2003-01-27 三洋電機株式会社 液晶プロジェクタ装置

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5959773A (en) * 1997-08-20 1999-09-28 Hughes-Jvc Technology Corporation Parallel plate beam splitter configuration in high index glass

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006133802A (ja) * 1999-09-17 2006-05-25 Hitachi Ltd 映像表示装置
JP4658368B2 (ja) * 2001-04-09 2011-03-23 株式会社リコー 投影装置
JP2002303932A (ja) * 2001-04-09 2002-10-18 Ricoh Co Ltd 投影装置
JP2005506576A (ja) * 2001-10-24 2005-03-03 ロリク　アーゲー 切替可能なカラーフィルタ
EP1459113A4 (fr) * 2001-11-30 2006-10-11 Colorlink Inc Systemes et procedes de gestion de couleur compensee
EP1459113A1 (fr) * 2001-11-30 2004-09-22 Colorlink, Inc. Systemes et procedes de gestion de couleur compensee
US7649626B2 (en) 2002-04-18 2010-01-19 Qinetiq Limited Imaging spectrometer
US7385582B2 (en) 2002-08-23 2008-06-10 Edwin Lyle Hudson Temperature control and compensation method for microdisplay systems
US7008064B2 (en) 2002-11-05 2006-03-07 Elcos Microdisplay Technology, Inc. Two panel optical engine for projection applications
US7234816B2 (en) 2004-02-03 2007-06-26 3M Innovative Properties Company Polarizing beam splitter assembly adhesive
WO2005081039A1 (fr) * 2004-02-03 2005-09-01 3M Innovative Properties Company Separateur de faisceau polarisant comprenant un adhesif sensible a la pression
US7315418B2 (en) 2005-03-31 2008-01-01 3M Innovative Properties Company Polarizing beam splitter assembly having reduced stress
US10139645B2 (en) 2011-10-24 2018-11-27 3M Innovative Properties Company Tilted dichroic polarizing beamsplitter
US9784985B2 (en) 2011-10-24 2017-10-10 3M Innovative Properties Company Titled dichroic polarizing beamsplitter
US11568802B2 (en) 2017-10-13 2023-01-31 Google Llc Backplane adaptable to drive emissive pixel arrays of differing pitches
US11961431B2 (en) 2018-07-03 2024-04-16 Google Llc Display processing circuitry
US11710445B2 (en) 2019-01-24 2023-07-25 Google Llc Backplane configurations and operations
US11637219B2 (en) 2019-04-12 2023-04-25 Google Llc Monolithic integration of different light emitting structures on a same substrate
US11847957B2 (en) 2019-06-28 2023-12-19 Google Llc Backplane for an array of emissive elements
US11626062B2 (en) 2020-02-18 2023-04-11 Google Llc System and method for modulating an array of emissive elements
US11538431B2 (en) 2020-06-29 2022-12-27 Google Llc Larger backplane suitable for high speed applications
US11810509B2 (en) 2021-07-14 2023-11-07 Google Llc Backplane and method for pulse width modulation

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JP2002544556A (ja) 2002-12-24
JP4637370B2 (ja) 2011-02-23

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