JP2003121640A - Polarized-light conversion system, optical element, and projection type display system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarized-light conversion system which is small-sized and has high light efficiency. SOLUTION: This polarization conversion system is equipped with a 1st lens array which converges incident parallel light, a polarized light separating element which directs light having 1st polarized light to a 1st direction and also directs light having 2nd polarized light different from the 1st polarized light to a 2nd direction different from the 1st direction, and one or more polarized light converting elements which converts the light having the 1st polarized light and the light having the 2nd polarized light into light having substantially common output polarized light; and the polarized light separating element has an array of 1st prisms which are sectioned in a wedgelike shape and an array of 2nd prisms which are sectioned in a wedgelike shape. The respective prisms of the 1st array are arranged having slanging surfaces arranged nearby slanting surfaces of the corresponding prisms of the 2nd array and at least one prism in the array is a birefringent prism; and the polarized light separating element is so arrayed as to deflect the light having the 1st polarized light and further deflect the light having the 2nd polarized light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization conversion system for converting unpolarized light or partially polarized light into substantially completely polarized light. The invention also relates to an optical element comprising two lens arrays arranged on both sides of a substrate. The invention further relates to a projection display system incorporating such a polarization conversion system.

[0002]

BACKGROUND OF THE INVENTION Many optical systems require illumination with substantially perfect polarization. If such a device operates in unpolarized or partially polarized light, it is necessary that the light be fully polarized, i.e. converted to a single polarization state, before entering the optical system.

One method of converting unpolarized light into fully polarized light is the well known linear polarizer. An idealized linear polarizer transmits linearly polarized light in one direction without loss and completely absorbs linearly polarized light in orthogonal directions, so that unpolarized light incident on the polarizer is converted into completely linearly polarized light. While such a linear polarizer is a simple means of producing linearly polarized light, it has the disadvantage of low efficiency. An ideal linear polarizer, by absorption within the polarizer and / or reflection at the surface of the polarizer, has an efficiency of only 50%, and practical linear polarizer efficiencies are typically 40-45%. Within the range of.

Another known means for converting unpolarized light into polarized light is the polarization conversion system. In a polarization conversion system, incident light that is already polarized in the desired polarization state is transmitted unchanged. Polarized light having a polarization state orthogonal to the desired polarization state is converted into light having the desired polarization state without being blocked as is the case when a conventional linear polarizer is used.

A polarization conversion system essentially consists of a polarization separating element (PS) that separates incident unpolarized or partially polarized light.
E) (polarization splitting
element), light of one polarization state is spatially or angularly separated from light having orthogonal polarization states and emitted from the PSE. Polarization conversion system
It also comprises a polarization conversion element for converting the polarization state of one of the components emitted by the PSE.

Many polarization splitting elements are known. As an example, FIG. 18 shows one embodiment of a known Wollaston prism in which two birefringent wedges W1 and W2 combine to form a composite block and the hypotenuses of the two prisms are close together. In this Wollaston prism embodiment described in EP-A-0 993 323, two wedges W1 and W2 are incorporated as liquid crystal layers having different thicknesses. The optical axis direction of each wedge rotates 90 ° over the thickness of the wedge, and the optical axes of the two wedges are orthogonal to each other at the interface of the two wedges.

US Pat. No. 5,978,136 discloses a conventional PCOS shown in FIG. 20a of the accompanying drawings.
This polarization conversion system comprises two lens arrays 5 and 6. Elements of the first lens array 5 project an image onto corresponding elements of the second lens array 6. Then
A set of polarization beam splitter cubes (polaris
Since the ing beam splitter cube 2 spatially separates the P component and the S component of light, only the P component or only the S component is incident on the set of retarder stripes 2c.
The retarder stripe is configured to be a substantially half-wave plate such that light incident on the retarder is converted into a substantially orthogonal state to the light. The light leaving the polarization conversion system is substantially polarized. An opaque mask 9 is placed between the second lens array 6 and the polarizing beam splitter array 2 to reduce crosstalk.

[0008] Ogiwara et al., "PS Polar
isation Converting Device
for LC Projector Using H
olographic Polymer-Disper
sed LC Films ", SID 1999, describes a further conventional PCOS. The device shown in FIG. 19 comprises two lens arrays 5 and 6, two polymer dispersed liquid crystal (PDLC) gratings 2 and 4, and a set of half-wave retarder elements 3. Polarization separation effectively diffracts only one linearly polarized light (P) and transmits orthogonal linearly polarized light (S) without significant diffraction.
This is achieved by the DLC grating 2.

The half-wave plate 3 is attached to the second grating 4 and the p linearly polarized light arranged in the optical path of the p-polarized light emitted by the grating 2 passes through one of the half-wave plates 3. Then, it is converted into s linearly polarized light.

The half-wave plate 3 is arranged so that the s linearly polarized light emitted by the grating 2 does not pass through the half-wave plate 3. Therefore, the s-polarized light emitted by the grating 2 is
Not affected by the half-wave plate 3. After passing through the array of half wave plates, the light is thus perfectly s-polarized.

In use, the polarization conversion system is illuminated by the collimated light produced by the lamp 7 and the parabolic mirror 8 and the incident light is focused by the first lens array 5. The second lens array 6 has the same focal length and pitch as the first lens array 5. First and second
Lens arrays are separated by approximately their focal lengths.

[0012]

This PCOS also has
It has the disadvantage that the minimum volume is limited by the tolerance of the half-wave retarder element. A further disadvantage is that this system uses two polarization splitting elements to reduce dispersion, which increases the cost and complexity of PCOS.

The dimensions of the polarization conversion system shown in Figure 20a are typically approximately 50 mm x 50 mm x 70 mm. When a polarization conversion optical system (PCOS) is used with a projector, the overall volume of the projector is significantly increased. The volume of PCOS in Figure 20a is
It can only be reduced if the focal length of the lens array is reduced, which requires a corresponding reduction in the pitch of the lens, the half-wave plate and the polarization separating cube. A conventional PCOS of the type shown in Figure 20a.
The lens array used in is usually 6 mm pitch p
However, it is desirable to reduce this to less than 1 mm by correspondingly reducing the projection distance of the optical system. However, in the case of a PCOS incorporating a conventional retarder element and a conventional polarization splitting cube, this is difficult to do because it becomes difficult to align the elements to each other with the necessary tolerances. Therefore, the fabrication and assembly of PCOS becomes even more difficult. Therefore, FIG.
In the elements used in current polarization conversion systems of the type shown in 0a, the physical size of the elements used limits the minimum volume of PCOS.

EP 0 887 667 and GB 2
326 729 discloses a method of making a highly patterned retarder element and its application to a polarization conversion optical system comprising an array of beam splitters of such an element.

FIG. 16 shows a further conventional polarization conversion system proposed by Minolta. This PCO
At S, the polarization separation element 2 is a diffractive optical element (DOE) polarization splitter. In the device shown in FIG. 16, light whose vibrating plane lies in the plane of the drawing, as indicated by the solid optical line, is not diffracted. Polarizations out of the plane of the drawing are diffracted, as shown by the dashed optical line. The device also comprises a first lens array 5 that focuses the light emitted by the polarization splitting element 2, a large conventional array of half-wave retarder elements 3, and a second lens array 6. This device is collimated by a parabolic mirror 8 and illuminated by light from a lamp 7 that has passed through a UV-IR filter 9 '.

The conventional PCOS of FIG. 16 has the disadvantage of using a diffractive element as the polarization splitting element 2. Since this is a diffractive element, it suffers from a large wavelength dispersion and also suffers from polarization mixing due to the overlap of a plurality of diffraction orders. The high wavelength dispersion of the polarization separation element is
It also means that the efficiency of S is low.

FIG. 17 shows a polarization conversion system according to a further prior art. This PCOS is described in US Pat.
No. 00 977, and WO 97/01779, and consists of three elements shown separately in FIG. 17 for clarity.

The first element 10 of the PCOS of FIG. 17 splits unpolarized or partially polarized light into two components that propagate in different directions and have orthogonal linear polarizations. Second element 1
Reference numeral 1 is a polarization-rotation element that rotates a vibrating surface. Second
The rotation of the vibrating surface generated by the element 11 largely depends on the incident angle of light. Light incident on the element 11 such as the beam b ₁ in the vertical direction rotates its vibrating surface by 90 °. Light that does not vertically enter the element 11 such as the beam b ₂ does not change its vibration plane.

The third element 12 bends the light beam so as to produce a substantially parallel output beam. The first element 10 and the third element 12 are composed of alternating portions of birefringent material and optically isotropic material.

The polarization conversion system of FIG. 17 suffers from a small acceptance angle. For example, the acceptance angle of a typical projection system may be about 5 degrees, while a smaller acceptance angle may be expected for this device for high focusing efficiency. Such a device may be suitable for use with a laser such as a CD player.

US Pat. No. 5,440,424 discloses a sheet polarization conversion system comprising a polarization-separation element, a polarization-rotation element and a coupling element. This polarization conversion system also has a small acceptance angle.

EP-A-0 753 780 discloses a polarization splitting element comprising a liquid crystal layer sandwiched between two substrates. Since one substrate has a jagged surface structure, the thickness of the liquid crystal layer is not constant. Non-polarized light incident on the polarization separation element is separated into two different polarization components at the interface between the sawtooth substrate and the liquid crystal layer, and the two polarization components leave the polarization separation element while advancing in different directions.

In the polarization splitting element disclosed in EP-A-0 753 780, one of the polarization components passes through the polarization splitting element without shifting. Therefore, the light
Non-normal incidence (non-normal incidence)
It must be incident on the polarization splitting element in e). This also requires that optical projectors using the polarization splitting element of EP-A-0 753 780 use tilted lamps to prevent significant loss of light.

[0024]

A polarization conversion system according to the present invention comprising a first lens array (17) for focusing incident collimated light and directing light having a first polarization in a first direction, A polarization separation element (16) for directing light having a second polarization different from the first polarization to a second direction different from the first direction, and substantially the light having the first and second polarizations. And one or more polarization conversion elements (15) for converting into light having a common output polarization, wherein the polarization separation element has an array of first prisms each having a wedge-shaped cross section, and each has a wedge-shaped cross section. A second array of prisms having a cross section, each prism of the first array comprising:
The polarization separation element, wherein each prism of at least one of the array of prisms is a birefringent prism arranged with a sloped surface disposed adjacent to a sloped surface of a corresponding prism of the second array. Are arranged to polarize light having the first polarization and polarize light having the second polarization, thereby achieving the above object.

The output polarized light may be the second polarized light.

Each prism in the first array of prisms may be a birefringent prism, and each prism in the second array of prisms may be a birefringent prism.

Each prism of the first array is replaced by the second prism of the second array.
May be arranged with their optical axis perpendicular to the optical axis of the corresponding prism of the array.

Each prism of the first array of prisms may be an optically isotropic prism, and each prism of the second array of prisms may be a birefringent prism.

The ordinary index of refraction n _o of the prisms of the second array, the extraordinary index of refraction n _e of the prisms of the second array, and the index of refraction n of the prisms of the first array.
_May be selected such that n _o <n <n _e .

The refractive index of the prism of the ordinary refractive index n _o of the prism of the second array, and said first array n
May be chosen such that n _o ≈n.

The array of birefringent prisms or one of the array of birefringent prisms may include a liquid crystal material.

A spacer that determines the thickness of the liquid crystal layer may be included.

Each spacer element may be integrated with each one of the prisms of the first array.

The array of birefringent prisms, or one of the array of birefringent prisms may include a photo-curable liquid crystal.

The array of birefringent prisms, or one of the birefringent arrays may include a polymer stabilized liquid crystal material.

Further comprising an array of third prisms each having a wedge-shaped cross section, and an array of fourth prisms each having a wedge-shaped cross section.
Each prism of the array may be arranged with an inclined surface proximate the inclined surface of the corresponding prism of the fourth array, and each prism of the third array may be a birefringent prism.

The optical axis direction of the prisms of the second array may vary over the thickness of the prisms.

The optical axis direction of the prisms of the second array varies by substantially 90 ° across the thickness of the prism, and the optical axis is relative to the direction of incident light across the thickness of the prism. It may be substantially vertical.

The optical axis direction of the prisms of the second array is perpendicular to the optical axis of the third prism on the surface of the prisms arranged near the array of the third prism. May be.

The array of second prisms may include a liquid crystal layer.

The array of polarization conversion elements may be arranged substantially in the focal plane of the first lens array.

The first lens array may be arranged between the polarization separation element and the polarization conversion element.

The first lens array may be arranged in front of the polarization separation element.

A second lens array for parallelizing the outputs of the polarization conversion element may be further provided.

The first lens array and the second lens array may have a common substrate.

The second lens array may be on the back side of the polarization conversion element in the vicinity thereof.

The polarization conversion element may be arranged directly on the second lens array.

The polarization conversion element may be disposed after the second lens and optically coupled to the second lens array.

The output from the polarization separation element is the first
Linearly polarized beam having an oscillating plane of
The second linearly polarized light beam has a second vibrating surface different from the vibrating surface, and the polarization conversion element or each polarization conversion element may be a polarization rotation element.

The vibrating surface of the first beam may be substantially 90 ° with respect to the vibrating surface of the second beam.

The above-mentioned one or more polarization conversion elements include a plurality of first
Of alternating regions and a plurality of second regions, wherein the first and second regions are arranged to receive the first and second polarizations, respectively.

In the projection display system of the present invention, the first and second regions have the same sizes of the cross sections of the first and second polarized beams, respectively, and have different first and second sizes. You may have.

A projection display system comprising a non-polarized or partially polarized light source, a polarization conversion system as defined in any one of claims 1 to 29, and a projection lens, whereby the above objects are achieved. To be achieved.

In the optical element of the present invention, the substrate, the first lens array arranged on one surface of the substrate and each lens have a one-to-one correspondence with the first lens array. , A second lens array disposed on the opposite surface of the substrate to achieve the above objectives.

The first lens array and the second lens array may be integrated with the substrate.

The pitch of the first lens array may be substantially equal to the pitch of the second lens array.

The pitch of the first lens array and the pitch of the second lens array may each be 2 mm or less.

The width W of the optical element and the thickness T of the optical element may satisfy the relationship of W / T> 3.

A first aspect of the present invention is a polarization conversion system, wherein a first lens array for focusing incident parallel light and light having a first polarization are directed in a first direction. A polarization splitting element for directing light having a second polarization different from the polarization to a second direction different from the first direction, and converting the light having the first and second polarizations into a substantially common output polarization. A polarization separation element, comprising one or more polarization conversion elements,
An array of first prisms each having a wedge-shaped cross section, and an array of second prisms each having a wedge-shaped cross section, each prism of the first array being of the second array. Arranged with an inclined surface arranged in proximity to the inclined surface of the corresponding prism, each prism of at least one of said array of prisms being a birefringent prism, said polarization separating element comprising: A polarization conversion system is provided that is arranged to deflect light having a polarization and to deflect light having the second polarization.

The polarization conversion system of the present invention includes a polarization separation element that polarizes both the first polarization component and the second polarization component. That is, both the direction in which the first polarization component is output from the polarization separation element and the direction in which the second polarization component is output from the polarization separation element are different from the direction of incident light. When the polarization conversion system of the present invention is incorporated into a projection display system, the use of a non-tilted lamp geometry does not lead to additional light loss.

The output polarized light may be the second polarized light.

Each prism in the first array of prisms may be a birefringent prism, each prism in the second array of prisms may be a birefringent prism, and each prism in the first array may be a second prism. Can be arranged with an optical axis perpendicular to the optical axis of the corresponding prism of the array.

Each prism of the first array of prisms may be an optically isotropic prism and each prism of the second array of prisms may be a birefringent prism.

The ordinary refractive index n _o of the prisms of the second array, the extraordinary refractive index n _e of the prisms of the second array, and the refractive index n of the prisms of the first array.
_Can be selected such that n _o <n <n _e .

Alternatively, the ordinary index of refraction n _o of the prisms of the second array and the index of refraction n of the prisms of the first array may be chosen such that n _o ≈n.

Where there is more than one array of birefringent prisms, one of the above array of birefringent prisms, or one of the array of birefringent prisms may comprise liquid crystal material.

The polarization conversion system may include spacers that determine the thickness of the liquid crystal layer. Each spacer element is the first
Can be integrated with each one of the prisms of the array.

Alternatively, if more than one array of birefringent prisms is present, then the array of birefringent prisms, or one of the array of birefringent prisms may comprise photocurable liquid crystals or is polymer stable. Liquid crystal material may be included. The polarization conversion system may further comprise an array of third prisms each having a wedge-shaped cross section, and an array of fourth prisms each having a wedge-shaped cross section, each prism of the third array being The prisms of the fourth array may be arranged with ramps proximate the ramps of the corresponding prisms, and each prism of the third array may be a birefringent prism.

The optical axis direction of the prisms of the second array may vary over the thickness of the prisms.

The optical axis direction of the prisms of the second array may vary substantially 90 ° over the thickness of the prisms,
The optical axis is substantially perpendicular to the direction of incident light across the thickness of the prism. The optical axis direction of the prisms of the second array may be perpendicular to the optical axis of the third prism at a surface of the prism arranged near the array of the third prism. The array of second prisms may comprise a liquid crystal layer.

The array of polarization converting elements may be arranged substantially in the focal plane of the first lens array.

The first lens array may be arranged between the polarization separation element and the polarization conversion element. Alternatively, the first lens array may be placed in front of the polarization splitting element.

A second lens array for collimating the outputs of the polarization conversion element may be further provided. The first lens array and the second lens array may have a common substrate. The second lens array may be on the back side of the polarization conversion element in close proximity thereto.

The polarization conversion element may be arranged directly on the second lens array. This prevents the polarization conversion element from being misaligned with the second lens array.

The polarization conversion element may be located after the second lens and may be optically coupled to the second lens array.

The output from the polarization separation element is the first
A linearly polarized beam having an oscillating surface and a second linearly polarized beam having a second oscillating surface different from the first oscillating surface, and the or each polarization conversion element may be a polarization rotating element. .

The vibrating surface of the first beam may be substantially 90 ° with respect to the vibrating surface of the second beam.

The above-mentioned one or more polarization conversion elements have a plurality of first
Of alternating regions and a plurality of second regions, the first and second regions being arranged to receive the first and second polarizations, respectively. The first and second regions may correspond to the cross-sectional size of the first and second polarized beams, respectively, and may have different first and second sizes.

A second aspect of the invention provides a projection display system comprising an unpolarized or partially polarized source, a polarization conversion system as defined above, and a projection lens.

A third aspect of the present invention is to provide a substrate, a first lens array disposed on one surface of the substrate, and each lens having a one-to-one correspondence with the first lens array. , An optical element comprising a second lens array disposed on the opposite surface of the substrate.

The first lens array and the second lens array may be integrated with the substrate.

The optical element according to this aspect of the invention is suitable for use in the polarization conversion system of the first aspect of the invention. Placing both lens arrays on a common substrate can increase the accuracy with which the lenses of one array can be aligned with the lenses of the other array, which can reduce the pitch of the lens arrays. Become. By reducing the pitch of the lens arrays, it is possible to reduce the focal length, thus reducing the distance between the two lens arrays and thus reducing the volume of the polarization conversion system incorporating the lens arrays.

The pitch of the first lens array may be substantially equal to the pitch of the second lens array.

The pitch of the first lens array and the pitch of the second lens array may be 2 mm or less, respectively.

The width W of the optical element and the thickness T of the optical element may satisfy the relationship of W / T> 3.

[0086]

The preferred features of the present invention will now be described by way of example with reference to the accompanying drawings.

In the drawings, like reference numbers indicate like elements.

FIG. 1a is a schematic diagram of a PCOS 15 according to a first embodiment of the present invention.

In use, a collimated light source (not shown)
Supplied by The light from the light source is unpolarized or partially polarized and contains two linearly polarized components with orthogonal polarization directions. One component has a vibrating surface in the plane of the drawing,
This is indicated in FIG. 1 by a line with arrows at both ends and is called "horizontal plane polarization". The other component has an oscillating surface out of the plane of the drawing, which is indicated in FIG. 1 by the circled dots and is referred to as "vertical plane polarized light".

The PCOS 15 shown in FIG.
Including 6. As shown in FIG. 1, this separates the two polarization components in the incident light and deflects each polarization component. One polarization component of the incoming light is directed in a first direction and the polarization component orthogonal thereto is directed in a second direction different from the first direction. The first and second directions are respectively different from the propagation direction of incident light. The configuration of the polarization separation element will be described below.

The PCOS 15 of FIG.
It further comprises a polarization conversion element located on the opposite side of the polarization separation element. The polarization rotation element 19 is arranged to convert the first and second polarization components into light having a substantially common output polarization. This is because the polarization conversion element is provided with a plurality of first areas 19a for converting one of the polarization components generated by the polarization separation element 16 into a desired output polarization, and the light of the first polarization component is substantially provided. This is appropriately performed by arranging the polarization conversion elements so that the light is incident only on these areas. Similarly, the polarization conversion element further includes a plurality of second areas 19b for converting the second polarization component generated by the polarization separation element into a desired output polarization, and the second polarization output by the polarization separation element. The component lights are arranged so that they substantially only enter these areas.

The desired output polarization component is the polarization separation element 16
Can be one of the two polarization components produced by In this case, the polarization conversion element 19 is arranged so as to transmit the light of the desired polarization component substantially without changing its polarization state. The polarization conversion element is further adapted to convert the other polarization component produced by the polarization separation element into a desired output polarization component.

In the embodiment shown in FIG. 1a, the polarization splitting element produces a horizontal plane polarization component and a vertical plane polarization component. The desired output state of the polarization conversion system is horizontal plane polarization. In this embodiment, the polarization conversion element 19 is incorporated as a polarization rotation element. The polarization conversion element is arranged such that one polarization component (in the embodiment of FIG. 1a, a vertical plane polarization component) is incident on the area 19a of the polarization rotation element which rotates the plane of oscillation of that component by substantially 90 °. . The other polarization component (in the embodiment of FIG. 1a, the horizontal plane polarization component) is incident on the area 19b of the polarization rotator that does not rotate the plane of oscillation of that polarization component, which plane of oscillation is substantially the polarization rotator. Not changed by 19. As a result, the output light from the PCOS 15 of FIG. 1a contains only horizontal plane polarized light because the vertical plane polarized light component was converted to horizontal plane polarized light by the polarization rotator.

A polarization rotation element 19 is provided by the polarization separation element 16.
Make sure that the horizontal plane polarized light component directed to does not pass through any of the areas 19a that rotate the vibrating surface, and the vertical polarization directed to the polarization conversion element 19 by the polarization separation element 16 does not rotate the vibrating surface. To ensure that none of the areas 19b pass, a first lens array 17 is provided for focusing the light directed to the polarization conversion element 19. In the embodiment of FIG. 1a, the first
Lens array 17 is disposed between the polarization separation element 16 and the polarization conversion element 19, so that the array 19 is spaced from the first lens array 17 by approximately the focal length of the first lens array 17. .

The output light from the PCOS is substantially telecentric and is arranged to produce an image of each lens of the first array in the plane of the panel when used with an additional condenser lens. To ensure certainty, a second lens array 18 is preferably provided on the PCOS 15 of FIG. 1a. The second lens array 18 is ideally located in the same plane as the array 19, and thus in the focal plane of the first lens array 17, because the separation of the planes of the arrays 18 and 19 causes a loss of light.

The focal length of the first lens array 17 is preferably equal to or substantially equal to the focal length of the second lens array 18. In the embodiment of FIG. 1 a, the pitch and lateral dimensions of the lens elements of the first lens array 17 are equal to the pitch and lateral dimensions of the lens elements of the second lens array 18. The pitch of both lens arrays is preferably 2 mm or less. Alternatively, in order to modify the etendue using the method disclosed in European Patent Application No. 99115664.7, the lateral dimensions of the lens elements of one lens array are
It is also possible that the lateral dimensions of the lens elements of the other array are different.

In the embodiment of FIG. 1a, all the lens elements of the first lens array 17 are replaced by the second lens array 18
Generate two images of the light source on the corresponding lens elements of.
The angle separating element causes the separation of the image of the light source at the second lens array 18 when projected by the first lens array 17. Separation angle degree and first lens array 1
The power of 7 is the image plane of the first lens array 17 that substantially corresponds to the planes of the second lens array 18 and the polarization conversion element 19, so that the two images are alternately arranged and do not substantially overlap. Is set to.

When the polarization separation element 16 is illuminated by substantially unpolarized light, the two separated orthogonally polarized beams produced by the polarization separation element 16 have substantially equal brightness to each other. However, if the light from the light source has some degree of linear polarization, the relative brightness of the two separated orthogonally polarized beams produced by the polarization splitting element will be the input polarization ratio of the light from the light source.
ration ratio).

A suitable light source for use with the PCOS 15 of FIG. 1a is an approximately 1.3 mm UHP (TM) arc lamp, such as manufactured by Philips.

In the embodiment of FIG. 1 a, the first lens array 17 and the second lens array 18 are the same substrate 20.
Are formed on opposite surfaces of the. Alternatively, for example, as shown in FIG. 8, the first lens array 17 and the second lens array 18 can be formed on different substrates.

FIG. 23 is a perspective view of the first lens array 17 and the second lens array 18 of the PCOS of FIG. 1a. The first lens array 17 is formed on one surface of the substrate 20, and the second lens array 18 is formed on the surface of the substrate 20 on the opposite side. Each lens element of the second lens array is a lens element of the first lens array 7 in that the incident light of the lens elements of the first lens array is directed to the associated lens element of the second lens array. Optically associated with. As mentioned above, in the embodiment of FIG. 1a, the pitch P and lateral dimension D of the lens elements of the first lens array are equal to the pitch and lateral dimension of the lens elements of the second lens array 18. The pitch of both lens arrays is preferably 2 mm or less.

The first lens array 17 and the second lens array 18 are preferably integral with the substrate 20.
For example, the first lens array 17, the second lens array 18, and the substrate 20 are made of a transparent plastic material.
It may be molded into one integral unit, or the first lens array 17 and the second lens array 18 may be fitted to both sides of a suitable transparent substrate. Alternatively, the lens array may be fabricated by manufacturing the lens arrays separately and bonding the two lens arrays with index matching material to form a common optical substrate. This avoids mechanical alignment of the elements when assembling the projector and reduces the number of element surfaces, thereby reducing unnecessary surface reflection and cost of the element's anti-reflective coating. These types of lenses can be made by UV casting, hot embossing, glass etching, or a variety of other techniques including forming gradient index lenses on a plastic or preferably glass substrate.

FIG. 24 shows a PCOS of the type shown in FIG. 1a.
15 shows a projection system using 15. In this projection system, the PCOS 15 is illuminated by light emitted by a light source 7 and collimated by a parabolic mirror 8. PCOS1
The light leaving 5 illuminates a light valve 48, eg a spatial light modulator, which allows the display of an image by modulating the brightness of the light. The condenser lens 49 is preferably a PCO
It is arranged between S15 and the light valve 48.

In the example where the light valve has a 4: 3 aspect ratio and a 0.7 inch diagonal, the width of the light valve is 4/5 of the diagonal, or approximately 14.22 mm. When the pitch of the lens array is 2 mm, the ratio of the distance from the first lens array to the second lens array and the distance from the second lens array to the light valve is 14.22 / 2.
Therefore, if it is desired that the distance from the second lens array to the light valve is 100 mm, the distance from the first lens array to the second lens array is 10 mm.
It should be 0 mm × 2 / 14.22 = 14.06 mm (assuming all distances are in air). The lens arrays 17 and 18 and the substrate 20 have a refractive index of 1.
When formed from 52 glass, the thickness T of the substrate 20
Is 21.4 mm. Since both lens arrays can be integrated on a single glass substrate with this thickness, the pitch of the lens arrays is less than 2 mm, so that both lens arrays are on a single substrate. It becomes possible to integrate.

Further, in this example, the reflector 8 is 60 mm.
If you have a diameter of
In order to pass through COS, lens arrays 17 and 1
The width W of 8 is preferably 60 mm or more. Board 2
When the thickness T of 0 is about 20 mm, the width W and the thickness T of the substrate 20 satisfy the following relationship: W / T> 3.
Ideally, the lens pitch is on the order of 200 microns and the glass thickness corresponding to two standard sandwich LCD glass substrates is on the order of 2 mm. This allows the use of bulky, low cost glass and standardized glass processing equipment. That is,
Since the thickness of the lens substrate for a given width is much thinner in the present invention than in the prior art, the volume of PCOS of the present invention is much smaller than that of conventional PCOS. For prior art devices, typical values for W and T are W = 50 mm, T = 50 mm and W
/ T = 1.

1 suitable for use in PCOS 15 of FIG. 1a
The structure of one polarization splitting element 16 is shown in detail in FIG. 2a. It can be seen that the polarization splitting element 16 consists essentially of two arrays of birefringent prisms 20 and 21. The prisms 20 and 21 of each array have a wedge-shaped cross section. The wedge angle of the prisms 20 of the first array is
Equal to the wedge angle of the prisms 21 of the second array,
Or substantially equal, and the cross-sectional dimension of the prisms 20 of the first array is equal to or substantially equal to the cross-sectional dimension of the prisms 21 of the second array.

In the array of these prisms, the prism 20 of the first array has a slope 20a (slope side) which is close to the slope 21a of the prism 21 of the second array.
(In FIG. 2a, a small gap is shown between prism 20 and prism 21 for clarity.) Since the prisms of the first array have substantially the same rust angle as the prisms of the second array, The bottom surface 20b of the prisms 20 of the first array is substantially parallel to the bottom surface 21b of the corresponding prism 21 of the second array.

In FIG. 2a, the first array of prisms 20
Are attached to a first cover plate or substrate 22 and the prisms 21 of the second array are attached to a second cover plate or substrate 23. These cover plates can be made from any transparent optically isotropic material such as glass or plastic materials. The cover plates 22 and 23 preferably each have a uniform thickness so that the front surface 22a of the first cover plate is parallel to the back surface 23a of the second cover plate 23. A front surface 22a of the first cover plate 22 forms an entrance face of the polarization separation element, and a back surface 23a of the second cover plate 23 forms an exit surface of the polarization separation element 16. .

The optical axis of the prism 20 of the first prism array and the optical axis of the prism 21 of the second prism array are parallel to the incident surface and the exit surface of the polarization separation element 16. Therefore, the optical axis of the prism is generally perpendicular to the light propagating through the polarization splitting element. Further, the optical axis of each first prism 20 is orthogonal to the optical axis of each second prism 21.

In use, the light from the light source enters the polarization splitting element 16 and then passes through the first cover plate 22 and one of the prisms 20 of the first birefringent prism array. The angular separation between one linearly polarized light and the orthogonal linearly polarized light results in the prism 20 of the first prism array and the corresponding prism 21 of the second prism array.
Occurs at the sloping interface between and.

FIG. 2b shows an alternative polarization splitting element 16 suitable for use in the PCOS 15 of FIG. 1a. This is because the first array of birefringent wedge prisms 20 of FIG.
Generally, the polarization splitting element 16 of FIG. 2a is replaced with the exception that it is replaced by a wedge prism 24 made of an optically isotropic material such as a glass or plastic material.
Corresponding to. Refractive index of the material used to form the optically isotropic wedge prism 24 is selected to give as n _o <n <n _e, where, n _o and n _e are the birefringent prism 21 Is the ordinary and extraordinary index of refraction of the birefringent material used to form the, and n is the index of refraction of the material used to form the optically isotropic prism 24. Alternatively, ordinary refractive index n _o of the birefringent material used to form the birefringent prism 21,
It may be selected to be substantially equal to the index of refraction of the isotropic material used to form the isotropic prism 24.

The angle of separation of the light beam is defined by the tilt angle and birefringence of the prism, while the average tilt of the two cones with respect to the input optical axis is defined by the relative index of refraction of the isotropic material. Furthermore, the difference in dispersion between the ordinary and extraordinary ray components can mean that the two polarization states have different dispersion characteristics. Therefore, the second lens array 1
It can be considered that the size of the point hitting 8 is different for the two orthogonal polarization states. This is shown in FIG. 1b, where the relative size and shape of one light spot is shown at 50 and the relative size and shape of the other light spot is shown at 51 (for comparison). The first point is shown inserted). To compensate for the difference in dot size,
As shown in FIG. 1b, the polarization rotation element 19 rotates the vibrating surface and receives the light from the larger light spot 51.
9a may be adapted to be larger than the area 19b which does not rotate the vibrating surface and receives light from the light spot 50.

The embodiment of FIG. 1b is further to that of FIG. 1a in that the second lens array 18 is optically coupled to the polarization rotator element 19 by an isotropic medium 52 having a refractive index n ₂ . different. A suitable material for the isotropic medium 52 is O
manufactured by pti-clad, having a refractive index _{n 2 = 1.38 UV-OPTI-} CLAD-138-X
Is. A suitable material for the second lens array 18 is Ny.
OC 462 with a refractive index of n ₁ = 1.6 according to e.

The array of birefringent prisms 21 of FIG. 2b and one or both of the birefringent prisms 20 and 21 of FIG. J. Broer "Mol. Cryst. Liq. Cryst." Vo
l. 261, pp 513-523 (1995), and can be incorporated as a liquid crystal layer. Alternatively, they are prepared using a photo-curable liquid crystal layer or a polymer-stabilized liquid crystal layer.
risen liquid crystal layer
r) can be incorporated.

FIG. 2c shows an alternative polarization splitting element 16 suitable for use in the PCOS of FIG. 2a and 2b
2c, the polarization splitting element of FIG. 2c deflects both polarization components.

The polarization splitting element 16 of FIG. 2c also includes a first transparent cover plate 22 and a second transparent cover plate 2.
2c, but in the polarization splitting element 16 of FIG. 2c, four arrays of prisms are arranged between the first cover plate 22 and the second cover plate 23. It The prisms in each array have a wedge-shaped cross section.

The first array is an array of optically isotropic wedge prisms 25, the second array is an array of birefringent prisms 26, and the third array is an array of birefringent prisms 27. And the fourth array is an array of optically isotropic prisms 28. Each prism 26 of the second array is arranged such that its beveled surface 26a is located in close proximity to the beveled surface 25a of the corresponding prism 25 from the first array. Similarly, each prism 27 of the third array is arranged such that its beveled surface 27a is located adjacent to the beveled surface 28a of the corresponding prism 28 of the fourth array. Each prism 26 of the second array has
6b is a plane 27 of the prism 27 of the third prism array
It is arranged in parallel and close to b. The prisms 25 of the first array have substantially the same rust angle as the prisms 26 of the second array, so that the prisms 25 of the first array 25
The bottom surface 25b of the corresponding prism 26 of the second array.
Is substantially parallel to the bottom surface 26b. Similarly, the prisms 27 of the third array have substantially the same rust angle as the prisms 28 of the fourth prism array, so that the bottom surface 27b of the prisms 27 of the third array corresponds to that of the fourth array. It is substantially parallel to the bottom surface 28b of the prism 28. The wedge angles of the first array prisms 25 and the second array prisms 26 are similar to the angles of the third array prisms 27 and the fourth array prisms 28, and in the illustrated embodiment. . Also, the pitch of prisms 25 and 26 is shown to be the same as the pitch of prisms 27 and 28, but can be different.

The optical axis direction of the prisms 27 of the third array does not change direction throughout its thickness, as shown schematically in FIG. 2e. However, although the optical axis direction of the prisms 26 of the second prism array is not constant, as shown in FIG.
The optical axis proximate the plane 26b of the prisms 26 of the second array is substantially perpendicular to the optical axis proximate the beveled surface 26a of the prism because it varies across the thickness of the prism shown in FIG. The optical axis of the prisms 26 of the second array is always parallel to the front surface 22a of the first cover plate 22, so that the optical axis is always substantially perpendicular to the light passing through the polarization splitting element. The optical axis of the prisms 26 of the second prism array is the plane of the prism closest to the corresponding prism of the third prism array (in FIG. 2c, this is the plane 26b of the prism) and its optical axis is the third. Are arranged so as to be perpendicular to the optical axis of the corresponding prism 27 of the prism array.

In the polarization splitting element of FIG. 2c, the prisms 26 of the second prism array and the prisms 27 of the third prism array are both "wedge grove".
slopes 26b and 2 oriented parallel to
The optical axis of the second array of prisms 26 having an optical axis proximate to 7b but closest to the corresponding prism 27 of the third array is perpendicular to the optical axis of prism 27. This reduces the wedge angle required to provide a given divergence angle between the ordinary and extraordinary rays, thereby reducing the dispersion produced by the uniaxial material of the prism. A further advantage is that ordinary and extraordinary rays
As shown by the optical line in FIG. 2c, it diverges symmetrically around the vertical line of the polarization splitting element. In contrast, when a single uniaxial prism with a wedge-shaped cross section is used, one polarization is greater than the orthogonal polarization because the extraordinary ray index change is greater than the ordinary ray index change. Diversified at an angle.

The wedge prism 26, the optical axis of which rotates through the prism thickness, can be formed using a liquid crystal material, such as the liquid crystal material ZLI-5200-100 (available from Merck). Alternatively, RM257 (M
A photo-curable liquid crystal material (such as available from Erck) or a polymer-stabilized liquid crystal material such as NOA61 (available from Norland) mixed with E7 (available from Merck) with uniform alignment can be used.

FIG. 4 shows a further polarization splitting element 16 suitable for use in the PCOS 15 of FIG. This polarization splitting element also deflects both polarization components.

The polarization separating element 16 of FIG. 4 comprises a first array of optically isotropic prisms 31 arranged between a first transparent cover plate 22 and a second transparent cover plate 23. The optically isotropic prisms are mounted on the second cover plate 23, and each prism 31 of the first prism array has an upper surface 31a (first surface) at an oblique angle with respect to a surface 31b close to the second cover plate. The first prism array has a “sawtooth” profile, since it has a surface located furthest from the two cover plates).

The liquid crystal layer 32 corresponds to the first cover plate 22.
And the optically isotropic prism array 31. Since the distance between the first cover plate and the second cover plate is substantially constant, and the thickness of the isotropic prism 31 changes in a “sawtooth” shape, the thickness of the liquid crystal layer also becomes a “sawtooth” shape. Changes to. Therefore, in the liquid crystal layer 32, each prism has a truncated wedge in a cross section.
forming an array of birefringent prisms that are dge). The array of isotropic prisms 31 can be made of a polymeric material. The “sawtooth” profile of the array of prisms 31 may be provided, for example, by polymer molding using a suitable mold, polymer casting, or lithographic processing.

The liquid crystal layer 32 is the first alignment layer 29.
And it is arranged between the first alignment layer 29 and the second alignment layer 30 for controlling the alignment direction of the liquid crystal molecules adjacent to the second alignment layer 30. In the embodiment of FIG. 4, one alignment layer 29 is arranged on the first cover plate 22 and the second alignment layer 30 is arranged on the upper surface of the array of prisms 31.

Alignment layers 29 and 30 may be formed of any suitable material, such as material PI2555, for example. Alternatively, alignment layers designed for use at lower fabrication temperatures can be used. The alignment layers 29 and 30 are polished or photo-aligned so that the liquid crystal molecules are oriented in a desired direction.
can be aligned). If the alignment layer 30 is aligned by a polishing process, it can in principle be polished parallel to the grooves of the prism array or perpendicular to the grooves of the prism array. However, polishing in the direction perpendicular to the grooves may make alignment difficult and may change the director profile of the liquid crystal material in the vicinity of the alignment layer 30, so that alignment in the direction parallel to the grooves of the prism array may be performed. It is preferred to polish the layer.

FIG. 5 shows the principle of operation of the polarization separation element 16. FIG. 5 relates to a polarization splitting element of the type shown in FIG. 2b, in which an array of isotropic wedge prisms and an array of birefringent wedge prisms are used for the first transparent cover plate 22 and the second transparent cover plate. 23, but in FIGS. 2a, 2c, and 4
The polarization splitting element in general operates in the same manner.

As described above, the polarization separation element 16 of FIG. 5 is illuminated substantially perpendicularly and telecentricly to the surface of the first cover plate 22 forming the incident surface of the polarization separation element. Incident light enters the first cover plate 22. Since the light is incident vertically, the light propagation is substantially unchanged at the front surface 22a of the cover plate 22. Further, at the interface between the transparent cover plate 22 and the isotropic wedge-shaped prism 24, there is substantially no deviation in the light propagation direction. (In principle, the transparent cover plate 22
There is some reflection on the two surfaces of B, but this is omitted from FIG. 5 for clarity. ) When the light passes through one of the isotropic prisms 24, it strikes the interface between the isotropic prism 24 and the corresponding birefringent prism 21. Since this interface is inclined with respect to the surface of the transparent cover plate 22, light is obliquely incident on this interface, and the p linear polarization and the s linear polarization have different refraction angles. Since the refraction angle is different for two orthogonal linearly polarized light, the incident beam of light is p linearly polarized light, which is directed in a first direction,
And s linearly polarized light that is directed in another direction.

Isotropic prism 24 and birefringent prism 21
As a result of the refraction that occurs at the sloping interface between and, the light does not propagate perpendicular to the plane of incidence of the polarization splitting element. This is true for both p and s linearly polarized light rays. As a result, the refraction is caused by the birefringent prism 21 and the front surface 23a of the second cover plate 23.
Occurs at the interface between the back surface 2 of the second cover plate 23.
Refraction also occurs at 3b. Refraction occurring at these last two interfaces increases the angular separation between p and s linearly polarized light. As a result, the p and s linearly polarized lights exit the polarization splitting element 16 in different directions from each other and in different directions than the incident unpolarized or partially modified propagation.

The polarization separation element 16 of FIG. 5 operates similarly to a Wollaston prism, except that only one birefringent wedge prism is used. The deflection angle between two orthogonally polarized beams is mainly due to the isotropic prism 2
4 and the ordinary and extraordinary ray indices of the birefringent prism 21 and the tilt angle θ.
For example, in the particular example of this embodiment, a 5 ° separation between vertical and horizontal polarization is required, as defined by the etendue requirements of the optical system. Inclination angle is 3
An isotropic prism with a refractive index of 1.52 at 0.5 ° is mounted on a glass substrate. A birefringent liquid crystal material having an ordinary ray index of 1.52 at 550 nm and an extraordinary ray index of 1.67 at 550 nm is aligned with the prism surface. A 5 ° separation angle is produced by the element for extraordinary rays, while the ordinary rays are not deflected. While the degree of dispersion of the liquid crystal material is comparable to the ordinary ray index for anisotropic materials, the degree of dispersion is different for extraordinary ray components. Therefore, the unpolarized beam is not dispersed while the dispersed portion is seen in the deflected beam.

As is apparent from FIG. 5, the separation of one linearly polarized light from the orthogonal linearly polarized light occurs at the interface inclined with respect to the light propagation direction. As a rule, such oblique interfaces are arranged one on each of the cover plates,
This can be achieved by providing a single pair of wedge prisms on the polarization splitting element. Then, the polarization separation element is shown in FIG.
Has a single sloping interface extending over the entire area of the device, as schematically shown in. This has the disadvantage that the overall thickness of the device is relatively thick. For a given tilt angle θ of the prism and a given lateral dimension of the polarization separating element, there is a lower limit on the thickness of the polarization separating element, beyond which it is impossible to reduce the thickness. Is.

In contrast, in the present invention, the polarization splitting element of the PCOS is not provided with a single wedge prism, but is provided with an array of "cut" prisms. These prisms do not extend over the entire lateral dimension of the polarization splitting element, but instead have only a portion of the lateral dimension of the polarization splitting element cut away. As a result, the array of prisms has a sawtooth profile as shown in Figure 3b. By cutting the prism in this way,
The total thickness of the polarization separation element can be reduced.

Refraction results from the regular structure of truncated prisms. The refraction angle is inversely proportional to the pitch of the truncated prism. The height of the truncated prism is also proportional to the pitch for a given prism angle. Therefore, increasing the truncated height reduces the refraction angle and increases the amount of refracted light within a given angle.

In the PCOS 15 shown in FIG. 1, the polarization conversion element rotates the vibration plane of the linearly polarized light by 90 °, and the first element 19 is rotated.
a and element 19b that does not rotate the plane of vibration of linearly polarized light
including. In principle, the polarization rotation has a space between adjacent half-wave plates that act as elements 19b that do not rotate the vibrating surface, and a dispersive half-wave plate that acts as the element 19a that rotates the vibrating surface.
f wave-plates). In one embodiment of the invention, however, the polarization rotator element 19 comprises a uniaxial layer extending over the entire area of the PCOS. The thickness of the uniaxial layer is substantially 1 /
Selected to operate as a two-wave plate. The region 19a that rotates the vibration plane of the linearly polarized light and the region 19b that does not rotate the vibration surface of the linearly polarized light are defined by changing the direction of the optical axis of the uniaxial layer. This is shown in FIGS.
Shown in b.

As shown in FIG. 14b, the uniaxial layer 19 has an optical axis that is not uniformly oriented over the area of that layer.
The uniaxial layer 19 has one or more regions whose optical axes are oriented in one direction and one or more regions whose optical axes are oriented in different directions. In the embodiment of Figure 14b, the first optical axis orientation has an optical axis that is substantially parallel to the polarization direction of the first polarization state and the second optical axis orientation has the second polarization state of polarization. It has an optical axis oriented at 45 ° to the direction. P
In COS, uniaxial layer 19 is oriented such that light in the first and second polarization states is incident on regions of layer 19 having the first or second optical axis orientations, respectively. Therefore, the action of the uniaxial layer causes the polarization angle of the second polarization state to be 90 degrees so that the polarization state is substantially the same as the first polarization state.
° To change.

The direction of the optical axis changes over the entire wave plate 1 /
The manufacture of a two-wave plate is described in EP 0 887 667, the content of which is hereby incorporated by reference.

The patterned retarder element shown diagrammatically in FIG. 14a is, instead, EP 0 829 744.
It may consist of a patterned retarder element and an unpatterned retarder element as described in. The contents of this patent application are incorporated herein by reference. As shown in FIG. 14c, the patterned retarder element 19 is used in series with the unpatterned retarder element 32 'to reduce the wavelength dependence of the polarization rotator element.

In the embodiment where the polarization splitting element 16 splits light in the horizontal plane, a pair of linear images of polarized light that are substantially orthogonal to each other are formed on the polarization rotator element 19. In this case, as shown in FIG. 14a, the uniaxial layer 19 has 0
And alternating vertical stripes of 135 ° optical axis alignment with respect to the vertical.

The uniaxial layer whose optical axis direction changes in the manner shown in FIG. 14a over the area of the uniaxial layer is a liquid crystal layer or an optical layer arranged on the alignment layer, as schematically shown in FIG. 14b. It may be composed of a curable liquid crystal material. The device shown in FIG. 14b comprises an optically isotropic transparent substrate 30, an alignment layer 31, and a uniaxial material layer 32 which acts as a half wave plate. The orientation of the alignment layer varies across its area, substantially similar to the desired orientation of the optic axis of the uniaxial material. As shown in FIG. 14c, a second uniaxial material layer having uniform alignment of the optical axis is placed on the opposite side of the substrate 30 to provide an unpatterned retarder element 32 '.

FIG. 6a shows a further embodiment of the PCOS 15 according to the invention. This embodiment is different from the embodiment of FIG. 1 in that the first lens array 17 is arranged between a light source (not shown) and the polarization separation element 16. The polarization separation element 16 ideally lies substantially in the plane of the first lens array 17. In practice, the first array 17
Can be attached to the cover plate 22 of the PSE 16 and the second lens array 18 can be mounted to the PSE 16 with a suitable spacer material as shown in FIG. 6b.
er substrate) 23.

In the embodiment shown in FIGS. 6a and 6b, the polarization splitting element 16 may have the general form shown in any of FIGS. 2a, 2b, 2c, 4 or 5. In particular,
The polarization splitting element preferably comprises an array of truncated wedge prisms as shown in Figure 3b. This reduces the overall thickness of the polarization separation element 16 and allows it to be located between the first lens array 17 and the second lens array 18.

FIG. 7a shows a PCOS according to a further embodiment of the invention. In the present embodiment, the first lens array 17 is arranged between the polarization separation element 16 and the light source (not shown), and the polarization rotation element 19 is composed of the polarization separation element 16 and the second lens array 18. Placed in between. In this embodiment, the polarization rotator 19 is preferably a 1/2 wave plate of the type shown in FIG. 14a, where the optical axis direction varies over the area of the wave plate. The polarization rotator is preferably formed of a thin layer of birefringent material such as photocurable liquid crystal. The use of a thin polarization rotator element allows the polarization rotator element to be positioned between the first and second lens arrays. Thus, in the embodiment of FIG. 7 a, both the polarization splitting element 16 and the polarization rotator element 19 are arranged between the first lens array 17 and the second lens array 18. The second lens array 18 can be a UV cast polymer on the surface of the element 19 that reduces the thickness of the PCOS and protects the element 19.

FIG. 7b shows a PCOS 15 according to a further embodiment of the invention. In this embodiment, the first lens array 17 and the second lens array 18 are arranged on different substrates. This embodiment is particularly advantageous when the focal lengths of the lens arrays 17 and 18 are long, which in this case makes the element large and heavy by forming two lens arrays on a common substrate. This is because

The embodiment of FIG. 7b is generally similar to the embodiment of FIG. 1, except that the first lens array 17 and the second lens array 18 are formed on separate substrates. The polarization splitting element 16 of the embodiment of FIG.
It may be a polarization splitting element as described with reference to any of Figures 2a, 2b, 2c, 4 and 5.

FIG. 8 shows a PCOS 15 according to a further embodiment of the invention. In the present embodiment, the polarization conversion element (formed by the array of the half-wave plate 19 a in the present embodiment) is directly arranged on the second lens array 18. This eliminates the possibility that the polarization conversion element may be misaligned with the lens array during use of PCOS.

The embodiment of FIG. 8 is generally similar to the embodiment of FIG. 1, except that the polarization conversion element is arranged directly on the second lens array 18. The polarization splitting element 16 of the embodiment of FIG. 8 may be a polarization splitting element as described with reference to any of FIGS. 2a, 2b, 2c, 4 and 5.

In the embodiment of FIG. 8, the first lens array 17 and the second lens array 18 are arranged on the common substrate 20. However, the polarization conversion element can be arranged directly on the surface of the second lens array even if the first lens array 17 and the second lens array 18 are not arranged on a common substrate. Is.

As can be understood from the above description, both of the two light beams output from the polarization separation element 16 are linear plane polarized light in which the vibrating surface of one beam is orthogonal to the vibrating surface of the other beam. The standard of performance of the polarization separation element is 2
The degree to which the two output beams are actually linearly polarized.
This is known as the "extinction ratio" of the polarization splitting element.

For polarization splitting devices intended for use in PCOS, relatively low extinction ratio values such as 10: 1 may be acceptable. This is because the output light from the PCOS is often used, for example, before a "clean-up" polarizer is provided to the projection system (for a single beam, due to the extinction ratio of the polarizations, they are orthogonal. Measure the amount of light of a given linearly polarized light versus the amount of light of polarized light). For example, if a large extinction ratio of over 100: 1 is achieved, the polarization splitting element itself can be used as a polarization beam splitter.

9 and 10 show a polarization splitting element used as a polarization beam splitter in a liquid crystal projection system.

9 and 10 show the polarization separation element 16 placed in front of the pixellated liquid crystal panel 33. 9 and 10, the polarization splitting element 16 is a polarization splitting element of the type shown in FIG. 2b, in which the array of birefringent wedge prisms 21 and the array of optically isotropic wedge prisms 24 are transparent to the transparent cover plate 22. It is arranged between the cover plate 23 and the cover plate 23. However, FIG.
The polarization splitting element according to a, 2c, 4 or 5 may instead be used in the projection system shown in FIGS. 9 and 10.

The liquid crystal layer includes a rear substrate 34, a reflective layer 35 disposed on the substrate 34, and a pixellate liquid crystal layer 36 disposed on the reflective layer 35. The second transparent cover plate 23 of the polarization separation element 16 also functions as an upper substrate of the liquid crystal display device 33. The provision of electrodes (not shown) allows addressing of individual pixels of the liquid crystal layer 36. By providing the filtering (not shown), R in FIG.
A set of red, green, and blue pixels, indicated by G and b, is formed.

In operation, the projection system of FIGS. 9 and 10 is illuminated with substantially parallel plane polarized light. The incoming plane-polarized light is vertically and telecentrically incident on the front surface 22a of the upper cover plate 22 forming the entrance surface of the polarization splitting element 16.

The polarization splitting element is arranged such that the incoming plane polarized light is transmitted through the polarization splitting element without a change in polarization. In the embodiment of FIGS. 9 and 10, the incoming plane polarized light has an oscillating plane outside the drawing, so that the light reaching the liquid crystal layer 36 is also plane polarized in this direction.

The liquid crystal layer 36 passes through the liquid crystal layer and passes through the reflective layer 3
5 acts to selectively change the polarization state of the light reflected by 5, and returned after passing through the liquid crystal layer 36. By varying the voltage applied to the pixels of the liquid crystal layer, it is possible to choose that the light leaving the liquid crystal layer 36 after reflection by the reflector 35 does not change its vibrating plane, or by the reflection layer 35. It is possible for the light exiting the liquid crystal layer 36 after reflection to rotate the vibrating surface 90 °. Light exiting the liquid crystal layer 36, which does not change the plane of vibration, is directed by the polarization splitting element back towards the light source. However, the light exiting the liquid crystal layer whose vibrating surface is rotated by 90 °, as shown in FIGS.
The polarization separation element deflects the incident light away from the optical path.

The projection system shown in FIGS. 9 and 10 further comprises a projection lens (not shown in FIGS. 9 and 10). The projection lens is positioned such that the light deflected by the polarization splitting element after being reflected by the reflector 35 is directed to the projection lens. The light reflected by the reflective liquid crystal panel 33 whose vibrating surface does not change is reflected by the polarization separation element 16.
It is directed back to the light source and does not reach the projection lens. In this way, by properly addressing the pixels of the liquid crystal display device 33,
The desired image can be directed to the projection lens for subsequent projection.

A conventional projection system incorporating a reflective liquid crystal panel generally has a dichroic polarization beam splitter (P
BS) is used. However, dichroic PBS is relatively expensive and large. Therefore, it is advantageous to use the polarization splitting element of the present invention in a projection system in order to reduce the cost and volume of the projection system. Further, the polarization splitting element of the present invention has little variation in its optical characteristics even if the angle between the input light and the normal line of the polarization splitting element changes. For projection systems having a small liquid crystal panel with a low F / # illumination flux, the use of the polarization splitting element of the invention offers advantages in terms of flux throughput and contrast ratio.

FIG. 11 is a schematic diagram of the projection system.
The light from the lamp 7 is collimated by the parabolic mirror 8. The parabolic mirror 8 also acts as a "cold" mirror in combination with a "hot mirror" 37, which acts to remove unwanted heat from the light emitted by the lamp 7. Then, the light enters the PCOS element 15 to generate a plane polarized telecentric beam. PCOS1
5 may be the PCOS of the present invention described with reference to any of FIGS. 1, 6, 7, and 8 above.

Light leaving the PCOS passes through a condenser lens or homogenizer lens 38 that produces a magnified image of the lens array elements of the PCOS substantially in the plane of the field lens 39. The light is transmitted to the liquid crystal panel 33 via the field lens 39, so that the liquid crystal panel is reliably illuminated in a telecentric manner.

The polarization beam splitter 40 is located between the field lens 39 and the liquid crystal panel 33. As described above with reference to FIGS. 9 and 10, when the liquid crystal panel 33 reflects light whose plane polarization does not change, it is directed back to the lamp 7 by the polarizing beam splitter 40. However, if the light reflected by the liquid crystal panel 33 causes the vibrating surface to rotate substantially 90 °, the light will be directed with respect to the projection lens 41. Therefore, an image encoded by the liquid crystal panel 33 can be projected.

In the polarization splitting element 16 described with reference to FIG. 4, in which the liquid crystal material is used to form a birefringent wedge prism, the transparent cover plates 22 and 23 are uniformly spaced between the PCOS assemblies. It is necessary to provide different cell gaps and be coupled to each other. FIG. 12 shows the liquid crystal layer 3
2 shows a further embodiment of a polarization splitting element, where 2 is used to form a birefringent wedge prism. The polarization splitting element of FIG. 12 also comprises an array of optically isotropic prisms 31.

In the polarization splitting element 16 of FIG. 12, the optically isotropic prism 31 is formed of a polymeric material, for example by molding or embossing a polymeric sheet to provide an array of wedge prisms. . Spacer ball 4
2 is used to space the polymeric wedge prism 31 from the lower transparent cover plate 23, thus ensuring a uniform spacing between the two transparent cover plates 22 and 23. The spacer balls 42 used in this embodiment can be any conventional spacer balls as used in conventional liquid crystal panels. Spacer ball 42
Can be introduced by a spray process, or the upper transparent cover plate 22 and the lower transparent cover plate 2
It can be mixed with the adhesive used to bond the three.
Spacer balls 42 generally have a diameter on the order of a few microns.

FIG. 13 shows a further polarization splitting element 16. As in the embodiment of FIG. 12, an array of liquid crystal layers 32 and optically isotropic prisms 31 is arranged between the first transparent cover plate 22 and the second transparent cover plate 23. Also in this polarization separation element, the optically isotropic wedge-shaped prism 31 is formed of a polymer material by, for example, molding or embossing. The polymeric material is further shaped to provide the spacer posts 43. When the upper cover plate 22 and the lower cover plate 23 are combined, the spacer posts 43 ensure a uniform spacing between the upper cover plate 22 and the lower cover plate 23. Thus, spacing spacer posts into the polymer layer throughout the polarization splitting element has the advantage of simplifying the fabrication of the polarization splitting element. A further advantage is that the uniformity of spacer post alignment is controllable so that the potential scattered from spacer posts 43 can also be more easily controlled.

The polarization splitting elements of FIGS. 12 and 13 also
It deflects both polarization components from the direction of incidence.

Fabrication of a polarization splitting element incorporating a liquid crystal material can be accomplished using conventional liquid crystal panel assembly methods.
The surface facing the liquid crystal layer, that is, the surface of the polymer layer 31 and the inner surface of the lower transparent cover plate 23 may be coated with an alignment layer for aligning the liquid crystal layer material, for example, a layer of alignment material PI2555. The alignment layer can be deposited by spin coating. The polymer layer is used to form an optically isotropic wedge prism because care must be taken to ensure that the alignment layer does not have to be baked at temperatures that could damage the polymer material. If
The material used to form the alignment layer must be carefully selected.

The upper and lower transparent cover plates may be made of a transparent material having optical isotropy. The upper cover plate 22 and the lower cover plate 23 are preferably made of a polymeric material. This is because it reduces the cost and weight of the polarization splitting element.

As can be seen from the above description, FIGS.
In the polarization separating elements shown in 2 and 13, switching of the liquid crystal material is not required. Therefore, it is not necessary to provide the polarization separation element with an electrode for applying a voltage to the entire liquid crystal layer. This is because the high deposition temperature required to form the transparent electrode usually places severe restrictions on the materials that can be used, and thus a wider selection of materials in the manufacture of polarization separation elements. Means that can be used.

The lack of an essential condition for addressing the liquid crystal layer also makes the choice of cell gap thickness more flexible. If an electric field has to be applied across the liquid crystal layer for switching of the liquid crystal material, a small cell gap is usually preferred so that a given electric field can be achieved at low voltage. This limitation does not require addressing the liquid crystal material 32, as described above, so that FIG.
It does not apply to cell gaps of 2 or 13 PSEs. However, if the cell gap is too large, it may be difficult to maintain alignment of the liquid crystal molecules across the thickness of the liquid crystal layer, so it is preferable to avoid a very large cell gap of, for example, 1 mm. About 10
Cell gaps on the order of 0 microns and below are generally
Maintain alignment throughout its depth.

FIG. 15a shows a further polarization splitting element. This also includes the first transparent cover plate 22 and the second transparent cover plate 22.
And an array of two prisms disposed between the transparent cover plate 23 and the transparent cover plate 23. The first prism array is an array of isotropic prisms 24 and 24a, and the second prism array is an array of birefringent prisms 21 and 21a. The prisms of each array have a substantially wedge-shaped cross section. The wedge angle of the prisms of the first array is determined by the prisms 21 and 21 of the second prism array.
equal to or substantially equal to the wedge angle of a, the cross-sectional dimensions of the prisms 24 and 24a of the first array are:
Equal to or substantially equal to the cross-sectional dimension of the second array of prisms 21 and 21a.

In the array of these prisms, the prisms 24 and 24a of the first array are close to the slopes of the prisms 21 and 21a of the second array (oblique side).
Have. The prisms of the first array have substantially the same rust angle as the prisms of the second array, thus
The bottom surfaces of the prisms 24 and 24a of the second array are substantially parallel to the bottom surfaces of the corresponding prisms 21 and 21a of the second array. In contrast to the above-mentioned polarization separation element,
The prisms in each array are not arranged in a "sawtooth" arrangement in which the thick ends of one prism are placed in close proximity to the thin ends of adjacent prisms. In the polarization splitting element of Figure 15a, the tilt directions of the prisms in the array alternate. Thus, the first prisms 24 of the first array are arranged so that their thickness decreases from left to right, as seen in FIG.
15a increases in thickness from left to right in FIG. 15a. Thus, the prisms 24a of the first array have their thin ends proximate the thin ends of one adjacent prism 24 of the first array and their thick ends different from those of the first prism array. Are arranged so as to be close to the thick ends of the adjacent prisms 24. The prisms of the second prism array are similarly arranged. (The boundaries between adjacent prisms in the array are shown as dashed lines in FIG. 15a, but it should be noted that, depending on the array configuration, there may be no physical boundaries between adjacent prisms in the array.) For convenience, the prism structure shown in FIG.
e) Call it a structure.

The wedge angle θ1 of the prisms of the first array of decreasing thickness from left to right in FIG. 15a is preferably the first increasing thickness from left to right in FIG. 15a.
Is equal to or substantially equal to the wedge angle θ2 of the prisms of the array.

As shown in FIG. 15a, since the polarization splitting element 16 of FIG. 15a deflects the light of both polarization components, each polarization component has a propagation direction of the light incident on the outer surface 22a of the first cover plate 22. Leave the polarization splitting element in different directions. However, the element 50 in which the thickness of the prisms 24 of the first array decreases from left to right in FIG.
Directing the first polarization component in substantially the same direction as the element 51 in which the prism thickness of the first prism array increases from right to left in FIG. 15a directs the second polarization component, and Note that the reverse is also true.

The isotropic prisms 24 and 24a of the polarization splitting element of FIG. 15a are made by any suitable method of making an isotropic prism array, including any of the methods described herein with respect to other embodiments. Can be done. For example, the array of isotropic prisms 24 and 24a can be made from a polymeric material. Array of isotropic prisms "mountain"
The profile can be obtained, for example, by polymer molding using a suitable mold, polymer casting, lithographic processing, or embossing a polymer sheet.

The array of birefringent prisms 21 and 21a may also be provided by any suitable method, such as the method of making any of the birefringent prism arrays described above. For example, a birefringent prism array can be obtained by appropriately shaping a birefringent material. Alternatively, the birefringent prisms 21 and 21a may be formed using a liquid crystal material disposed between the second cover sheet 23 and the isotropic prism array, for example, in the manner described above with reference to FIG. .
When the birefringent prism array is incorporated as a liquid crystal layer having different thicknesses, the polarization splitting element 16 is preferably a first alignment layer (not shown) located on the slopes of the isotropic prisms 24 and 24a. , And a second cover sheet 23 having a second surface disposed on the upper surface 23a.
Alignment layer (not shown).

In FIG. 15a, the polarization splitting element is shown with the isotropic prism array located closest to the light source. Alternatively, the light may pass through the birefringent prism array before traveling into the isotropic prism array,
It is possible to direct the polarization splitting element 16 of FIG. 15a so that the light first enters the lower surface 23b of the second cover sheet 23.

FIG. 15b shows the polarization splitting element 16 of FIG. 15a.
Shows a polarization conversion system using.

The PCOS 15 of FIG. 15b includes a polarization splitting element 16 of the type shown in FIG. 15a. Polarization separation element 16
Are illuminated by unpolarized or partially polarized light from a light source (not shown). The polarization separation element 15 separates the two polarization components of the incident light, and the two polarization components leaving the polarization separation element 16 are indicated by a broken line and a solid line, respectively. As explained above, the direction in which the first and second polarization components are emitted from the polarization splitting element depends on the direction of the interface between the first and second prism arrays.

The PCOS 15 of FIG. 15b further comprises a polarization conversion element located on the opposite side of the polarization separation element 16 with respect to the light source. The polarization conversion element 19 converts the light from the polarization separation element into substantially uniform polarized light. In the embodiment of FIG. 15b, the desired output polarization is one of the two polarization components produced by the polarization splitting element, but this need not be the case.

In the embodiment of FIG. 15b, the polarization conversion element 1
9 is arranged so that one polarization component output from the polarization separation element 16 is incident on the area 19a of the polarization conversion element that rotates the oscillation plane of the polarization component by substantially 90 °. Area 19b of the polarization conversion element in which other polarization components output by the polarization separation element do not rotate the vibration plane of the polarization component.
Further, the vibrating surface of the second polarization component is substantially not changed by the polarization conversion element 19 because it is further arranged so as to be incident on. As a result, the light emitted from the PCOS 15 of Figure 15b contains substantially only one polarization component of light.

To ensure that the two polarization components output by the polarization splitting element are incident on the correct area of the polarization conversion element 19, the first lens array 17 is directed towards the polarization conversion element 19. It is provided for converging the light emitted. In the embodiment of FIG. 15b, the first lens array 17 is arranged between the polarization separation element 16 and the polarization conversion element 19.

The second lens array 18 is preferably
Provided in the PCOS 15 of FIG. 15a, it ensures that the light output from the PCOS is substantially telecentric. When the second lens array is provided, it can be appropriately arranged on the same substrate as the first lens array described above with reference to FIG. This is shown schematically in Figure 15b.

A "mountain" type polarization separation element of the type shown in FIG. 15a has an increased light transmission compared to a "serrated" polarization separation element. However, in order to ensure that the two polarization components are incident on the correct area of the polarization conversion element 19, the lens array needs to be accurately aligned with the polarization separation element. In particular, the pitch d _{m of the} lens array needs to be half the pitch d _s of the polarization separation elements. Furthermore, each element of the lens array
The elements 50 and 51 of the polarization separation element 16 need to be opposed and aligned.

The polarization conversion element pitch d _c must be equal to or substantially equal to twice the lens array pitch d _m . Further, the polarization conversion element 19 is arranged such that each first area 19a is placed so as to face approximately half the area of one element 50 of the lens array and half the area of the adjacent element 51 of the lens array. Needs to be done.

In contrast, in a PCOS incorporating a sawtooth polarization separation element, the pitch of the first lens array 17 need not be the same as the pitch of the polarization separation element, and the first lens array is It need not be aligned with the elements of the isolation element. This is shown schematically in Figure 15c, which illustrates a PCOS of the present invention incorporating a "serrated" polarization separation element. However, the polarization conversion element 19 of PCOS in FIG 15c is aligned with the second lens array 18, or the pitch d _c of the polarization conversion element is equal to the pitch d _m of the second lens array 18, or substantially Note that they are equal.

When PCOS is illuminated with a lamp having a reflector that incorporates a dichroic coating to improve reflectivity, Fresnel reflections cause some polarization in the light reflected by the reflector. . Figure 21a shows the geometry of the polarization produced by this Fresnel reflection.

FIG. 21b shows the polarization directions seen by an observer observing the reflector 8 along its axis of symmetry. When observed from this direction, it can be seen that the polarization direction has radial symmetry. In Figure 21b, P and S are p
Shows plane and s plane polarization states, with a subscript +
And - for indicating the degree of polarization, for example, P ₊ denotes a state having a substantial p polarization, S _- represents s-polarized light state having a low degree of polarization.

Since the light incident on the polarization separation element is already polarized to some extent, the p-polarized beam produced by the polarization separation element does not have the same intensity as the s-polarized beam produced by the polarization separation element. , The two images produced by the elements of the second lens array have different intensities. Due to the nature of the retarder used in the polarization conversion element 19, it is possible to convert the polarization state of the + component of the incident light by using the ½ wavelength retarder element and not change the vibration plane of the − component of the incoming light. More effective. Therefore, the polarization conversion element is patterned so that each region of the polarization conversion element transforms the vibration plane of the higher intensity polarization component incident on that region without changing the vibration plane of the lower intensity polarization component. It is preferable.

FIG. 21c shows a retarder 42 suitable for use as a polarization conversion element in which incident light is polarized as shown in FIG. 21b. The retarder of Figure 21c has four sections 42A-42D. The retarder is oriented so that sections 42A and 42C are predominantly p-plane polarized and receive light with a slight s-plane polarization component. Therefore, the regions 42A and 42C of the retarder
However, it preferably converts the p-polarized component of the incoming light into an s-polarized component, while having no effect on components that are already s-polarized. Conversely, regions 42B and 4 of retarder 42
In use, 2D receives light that is predominantly s-plane polarized, with only a minor component being p-polarized. Therefore, the area 42B
At and 42D, the retarder preferably converts the s-polarized component to p-polarized without affecting the polarization of the s-polarized component.

The retarder 42 of FIG. 21c is intended for use with a polarization splitting element that splits the p and s polarization components in the horizontal plane. Therefore, the optical axis direction of the retarder 42 is patterned into a vertical stripe, the optical axis of one strip is vertical, and the optical axis of the adjacent strip is 45 ° with respect to the vertical line. These strips are arranged such that in each region of the retarder, the polarization component of the maximum intensity of the incident light is directed onto the strip whose optical axis is 45 °. Thus, regions 42A and 42
At C, the p component of the incident light is directed into a strip having an optical axis that is 45 ° with respect to the vertical, thereby converting it to s-polarized light. On the other hand, the regions 42B and 42
At D, the s component of the incident light is directed by the polarization splitting element into a strip with an optical axis aligned at 45 ° to the vertical and converted to p-polarized light.

After the light passes through the wave plate 42 shown in FIG. 21c, the light passing through the retarder regions 42A and 42C becomes s-plane polarized light, while the region 42 of the retarder 42.
Light that has passed through B and 42D is in the p-plane polarization state.
In order to generate light with uniform polarization, it is necessary to pass the light through a second wave plate to convert one polarization component into orthogonal polarization states. FIG. 21d shows one suitable wave plate.

The wave plate 43 of FIG. 21d also has four sections 43A-43D, which match in size and shape with the regions 42A-42D of the wave plate 42 of FIG. 21c.

If it is desired that the output light be the s-polarized component, then sections 43A and 43C of wave plate 43 are used.
As described above, since the sections 42A and 42C of the wave plate 42 generate s-polarized light, it is not necessary to change the vibration plane of the light emitted by the wave plate 42. The optical axes of the regions 43A and 43C are parallel to the polarization of incident light.

Retarder 43 sections 43B and 4
The 3D receives p-polarized light from the retarder 42. Since it is desired that the output from the retarder 43 be s-polarized,
This includes sections 43B and 43 of retarder 43.
It is necessary for D to rotate the plane of vibration of the p-polarized light emitted by sections 42B and 42D of retarder 42 to produce s-polarized light. Therefore, the optical axes of the sections 43B and 43D of the retarder 43 are preferably
Tilted at 45 ° to the vertical.

The direction of the optical axis of the wave plate 43 and the wave plate 42
The polarization received from is shown in Figure 21d.

A further polarization splitting element 44 suitable for use in which the incident light is polarized as shown in FIG. 21d will be described with reference to FIG. 21e. The polarization separation element 44 includes the first and second
Layers of uniaxial material disposed between the transparent cover plates. FIG. 21e shows the optic axis orientation of the uniaxial material across the thickness of the uniaxial material layer, and it can be seen that the optic axis twist of the uniaxial material varies spatially. In regions 44A and 44C of element 44, the optical axis of the uniaxial material proximate one cover plate is substantially in the same direction as the optical axis of the uniaxial material proximate the other cover plate, while section 44B. And at 44D, the optic axis twists substantially 90 ° through the thickness of the layer of uniaxial material.

Sections 44B and 44D serve to rotate the polarization of the two separated beams by 90 °.
For example, if incident light containing components P- and S + is incident on polarization separation element 44, the two polarization components are angularly separated, and in sections 44B and 44D, these components rotate their polarization by 90 °. S- and P +.

Such a polarization splitting element, comprising a prism array configured to split light in the horizontal direction, comprises:
It can be used in a PCOS system 15a as shown in FIG. 1a. In this case, the light leaving the second surface 18 of the lens array comprises alternating vertical stripes of P and S polarization. This alternation depends on which section the light exits the polarization splitting element 44, compared to the stripes produced by sections 44B and 44D.
The stripes generated by C change one stripe at a time. That is, sections 44A and 44C
Produces stripes having alternating P and S polarizations, and then sections 44B and 44D produce stripes having alternating P and S polarizations.

Here, the light emerging from the polarization splitting element is the component P + and S- from sections 44A and 44C.
Components S- and P from sections 44B and 44D
Includes + and.

FIG. 21c shows a patterned polarization rotator element. This element then converts the light exiting the polarization splitting element of Figure 21e into light having a substantially uniform polarization.

When the polarization splitting element comprises a single array of birefringent wedge prisms, light with one linear polarization is:
Experience substantially all material dispersion. Since this index has the maximum degree of dispersion, it is usually the component that is refracted by the extraordinary ray refractive index. If it is desired that both orthogonal linearly polarized light components experience substantially equal dispersion, the optic axis has at least one area having a twist of 90 ° C. across the thickness of the uniaxial material, and This can be achieved by using a birefringent wedge prism that comprises a uniaxial material whose optic axis has at least one area with no twist across the thickness of the uniaxial material. Assuming that the area of a uniaxial material with an optical axis twist of 90 ° and the area of a uniaxial material with an optical axis twist of 0 ° are substantially equal, both orthogonal polarization components are substantially equal. Experience dispersion. Figure 22a schematically illustrates one embodiment of counter substrate alignment that achieves this effect. The counter substrate has two regions 46A and 46B.
The alignment direction of the alignment film changes between the two areas. In region 46A, the alignment direction is 90 ° to the vertical (as seen in FIG. 22a), while in region 46B the alignment direction is 0 ° to the vertical. When used with another alignment film that has a uniform alignment direction of 0 ° with respect to the vertical, the region 46A extends across the thickness of the uniaxial material, as shown in the top left insert of Figure 22a. It causes a 90 ° twist in the optical axis of the uniaxial material. Conversely, area 46B
22a, the optical axis of the uniaxial material does not cause twisting through the thickness of the uniaxial material, as shown in the bottom right insert of FIG. 22a.

FIG. 22b shows a modification of the embodiment of FIG. 22a. This figure shows a counter substrate 47 with multiple regions in different alignment directions. Area 47A has an alignment direction of 90 ° with respect to the vertical and area 47B
Has an alignment direction of 0 ° with respect to the vertical.
When used with another alignment film having a uniform alignment direction of 0 ° with respect to the vertical, the region 47A causes a 90 ° twist in the optic axis of the uniaxial material over the thickness of the uniaxial material. On the other hand, the area 47B is
The optical axis of the uniaxial material does not cause twist through the thickness of the uniaxial material.

1a, 1b, 2a, 2b, 6a, 6b,
In the PCOS embodiments shown in 7a, 7b, 14c and 15b, the polarization conversion element 19 comprises a plurality of first areas which have no effect on the polarization of the components incident thereon,
And another area for rotating the vibrating surface of the component incident thereon by 90 °. Therefore, these polarization conversion elements output light having a common vibrating surface. However, the present invention provides a PC having such a polarization conversion element.
It is not limited to the OS. For example, the PCOS polarization conversion element of the present invention instead comprises a polarization rotator element as described herein and a uniform wave plate or retarder disposed opposite the polarization rotator element with respect to the light source. Combinations may be provided. The uniform wave plate or retarder converts the linearly polarized light output by the polarization rotation element 19 into elliptically or circularly polarized light.

The present invention is directed to polarization separation in which light having a first polarization is directed in a first direction and light having a second polarization different from the first polarization is directed in a second direction different from the first direction. An element (16) and one or more polarization conversion elements (19a, 19b) for converting light having the first and second polarizations into a substantially common output polarization. The polarization separation element has a first prism array (20) having a wedge-shaped cross section,
And a second array of prisms (21) having a wedge-shaped cross section. One of the arrays of prisms is an array of birefringent prisms.

The polarization conversion system of the present invention provides for use in a projection display system.

[0204]

According to the present invention, the length of the polarization conversion system is reduced to, for example, 2 mm or less by using the birefringent retardation plate array and the birefringent P splitter and the birefringent S splitter which are aligned by using lithography. can do. The P-polarized light and the S-polarized light are separated by the P-splitter and the S-splitter so as to have the same angle, and then are projected on the lens array. Further, one of the P-polarized light and the S-polarized light is further polarized so that the polarized light becomes substantially uniform. Further, the retardation plate can be made of a photo-curable liquid crystal or the like in order to minimize pits. The P-splitter and S-splitter include a prism array and a birefringent layer associated therewith. According to the present invention, a very compact optical system is realized by combining such a retardation plate with a P splitter and an S splitter.
Further, since the light leakage of the system is reduced, the advantageous effect of improving the light efficiency can be obtained. Also, the reduction in pitch allows more lens elements to be incorporated into the system. As a result, the uniformity of the light source is improved, and the uniformity of the projected light is further improved.

[Brief description of drawings]

FIG. 1a is a schematic diagram of a first embodiment of a polarization conversion system according to the present invention.

FIG. 1b is a schematic diagram of a second embodiment of a polarization conversion system according to the present invention.

FIG. 2a is a schematic cross-sectional view of a first polarization separation element.

FIG. 2b is a schematic sectional view of a second polarization separation element.

FIG. 2c is a schematic cross-sectional view of a further polarization splitting element.

2d is a partial perspective view of the polarization splitting element of FIG. 2c.

2e is a partial perspective view of the polarization splitting element of FIG. 2c.

FIG. 3a is a schematic cross-sectional view of a further polarization splitting element.

FIG. 3b is a partial cross-sectional view of a further polarization splitting element.

FIG. 4 is a schematic cross-sectional view of a further polarization separation element.

FIG. 5 is a cross-sectional view showing the operation of the polarization beam splitting element.

FIG. 6a is a schematic view of a further embodiment of a polarization conversion system according to the present invention.

FIG. 6b is a schematic diagram of a further embodiment of a polarization conversion system according to the present invention.

FIG. 7a is a schematic view of a further embodiment of a polarization conversion system according to the present invention.

FIG. 7b is a schematic view of a further embodiment of a polarization conversion system according to the present invention.

FIG. 8 is a schematic cross-sectional view of a further embodiment of a polarization conversion system according to the present invention.

FIG. 9 is a schematic diagram of a reflective polarization separation element.

FIG. 10 is an enlarged cross-sectional view showing a reflective polarization separation element.

FIG. 11 is a schematic diagram of a projection system according to the present invention.

FIG. 12 is a schematic sectional view of a further polarization separation element.

FIG. 13 is a schematic sectional view of a further polarization separation element.

FIG. 14a shows a retarder alignment direction suitable for use in a polarization splitting element.

FIG. 14b is a schematic perspective view of the retarder of FIG. 14a.

FIG. 14c is a schematic diagram of another embodiment of a polarization conversion system according to the present invention.

FIG. 15a is a schematic cross-sectional view of a further polarization splitting element.

FIG. 15b is a schematic diagram of an embodiment of a polarization conversion system according to the present invention.

FIG. 15c is a schematic diagram of an embodiment of a polarization conversion system according to the present invention.

FIG. 16 is a schematic cross-sectional view of a conventional polarization conversion system.

FIG. 17 is a perspective view of another conventional polarization conversion system.

FIG. 18 is a schematic perspective view of a liquid crystal Wollaston type prism.

FIG. 19 is a schematic diagram of a further conventional polarization conversion system.

FIG. 20a is a schematic diagram of a further conventional polarization conversion system.

20b shows the fabrication of the polarization splitting element of the polarization conversion system of FIG. 20a.

FIG. 21a shows the polarization produced by a parabolic reflector.

FIG. 21b shows the polarization produced by a parabolic reflector.

FIG. 21c shows two waveplates suitable for utilizing the polarization shown in FIGS. 21a and 21b.

Figure 21d shows two wave plates suitable for utilizing the polarization shown in Figures 21a and 21b.

21e is a schematic perspective view of the optic axis twist of a uniaxial material suitable for utilizing the polarization induced by the reflector of FIG. 21a.

FIG. 22a shows one embodiment of counter substrate alignment directions for uniform dispersion of P and S components of linearly polarized light.

FIG. 22b shows a further embodiment of the alignment direction of the counter substrate for uniform distribution of linearly polarized light for the P and S components.

FIG. 23 is a perspective view of a lens array of the polarization conversion system of FIG. 1a.

24 is a schematic diagram of a projection system incorporating the polarization conversion system of FIG. 1a.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/13 505 G02F 1/13 505 5C058 G03B 21/00 G03B 21/00 E 21/14 21/14 A H04N 5/74 H04N 5/74 A (72) Inventor Marina Vladimir Buna Kazoba UK EX 39 4 Jay Y Oxford Share, Shinoa, Ashridge 3 (72) Inventor Tamotsu Takatsuka 174-1 Hayakawacho, Yaita City, Tochigi Prefecture Sharp There Dormitory 317 (72) Inventor Keisuke Mitani 3715 −32 (72) Inventor Kazuhiro Inoko 4-23-17 Higashi Funabashi, Funabashi City, Chiba Prefecture Graham John Woodgate UK RG 91 HF Oxford Share, Henry-On-Thames, Vicarage Road 9 (72) Inventor Masaharu Hara 2-2598-8 Shizuka, Otawara-shi, Tochigi Prefecture (72) Inventor Grant Boahill GL 541 GL Grochester Share, Stow-on-the -Wold, Mt Pleasant 1 (72) Inventor Emma Walton 4/3 NX Oxford, UK, Cowley, Butchamp Lane Viewchamp Praise 45 F Term (Reference) 2H042 CA09 CA14 CA15 CA17 2H049 BA05 BA42 BB03 BB51 BB62 BC22 205 BA02 BA03 BA09 BA14 2H088 EA47 2H099 AA12 BA09 BA17 CA02 CA07 CA08 CA11 5C058 AB06 BA05 EA11 EA12 EA13 EA26 EA51

Claims (35)

[Claims] 1. A polarization conversion system comprising: a first lens array (17) for focusing incident collimated light; and directing light having a first polarization in a first direction, the first polarization being different from the first polarization. A polarization splitting element (16) for directing light having a second polarization in a second direction different from the first direction, and light having the first and second polarizations having a substantially common output polarization One or more polarization conversion elements (1
5) and the polarization separation element comprises an array of first prisms each having a wedge-shaped cross section, and an array of second prisms each having a wedge-shaped cross section, the first array Each prism of the second array is disposed with an inclined surface disposed proximate an inclined surface of a corresponding prism of the second array, and each prism of at least one of the array of prisms is a birefringent prism. A polarization conversion system, wherein the polarization separation element is arranged to deflect light having the first polarization and deflect light having the second polarization. 2. The output polarization is the second polarization,
The polarization conversion system according to claim 1. 3. The polarization conversion system according to claim 1, wherein each prism of the first array of prisms is a birefringent prism, and each prism of the second array of prisms is a birefringent prism. 4. The polarization conversion system according to claim 3, wherein each prism of the first array is arranged with an optical axis perpendicular to the optical axis of a corresponding prism of the second array. . 5. The polarization conversion of claim 1, wherein each prism of the first array of prisms is an optically isotropic prism and each prism of the second array of prisms is a birefringent prism. system. 6. The ordinary refractive index n _o of the prisms of the second array, the extraordinary refractive index n _e of the prisms of the second array, and the refractive index n of the prisms of the first array.
The polarization conversion system of claim 5, wherein is selected such that n _o <n <n _e . 7. ordinary refractive index n _o of the prism of the second array, and the refractive index n of the prism of the first array is selected to be n _o ≒ n, to claim 5 The described polarization conversion system. 8. The polarization conversion system of claim 1, wherein the array of birefringent prisms, or one of the array of birefringent prisms comprises a liquid crystal material. 9. The polarization conversion system of claim 8 including spacers that determine the thickness of the liquid crystal layer. 10. The polarization conversion system of claim 9, wherein each spacer element is integral with a respective one of the prisms of the first array. 11. The polarization conversion system of claim 1, wherein the array of birefringent prisms, or one of the array of birefringent prisms comprises a photo-curable liquid crystal. 12. The polarization conversion system of claim 1, wherein the array of birefringent prisms, or one of the birefringent arrays comprises a polymer stabilized liquid crystal material. 13. An array of third prisms, each having a wedge-shaped cross section, and a fourth array of prisms, each having a wedge-shaped cross section, each prism of the third array comprising: The polarization conversion system of claim 1, wherein the polarization conversion system is arranged with sloping surfaces proximate the sloping surfaces of the corresponding prisms of the four arrays, each prism of the third array being a birefringent prism. 14. The polarization conversion system according to claim 13, wherein the optical axis direction of the prisms of the second array changes over the thickness of the prisms. 15. The direction of the optical axis of the prisms of the second array varies by substantially 90 ° over the thickness of the prism, the optical axis being the direction of incident light over the thickness of the prism. 15. The polarization conversion system of claim 14, which is substantially perpendicular to. 16. The optical axis direction of the prisms of the second array is perpendicular to the optical axis of the third prism on a surface of the prisms arranged near the array of the third prism. The polarization conversion system according to claim 15, wherein 17. The polarization conversion system of claim 13, wherein the array of second prisms comprises a liquid crystal layer. 18. An array of the polarization conversion elements is the first array.
The polarization conversion system of claim 1, wherein the polarization conversion system is disposed substantially in the focal plane of the lens array of. 19. The polarization conversion system according to claim 1, wherein the first lens array is arranged between the polarization separation element and the polarization conversion element. 20. The polarization conversion system according to claim 1, wherein the first lens array is arranged in front of the polarization separation element. 21. The polarization conversion system of claim 1, further comprising a second lens array that collimates the outputs of the polarization conversion element. 22. The polarization conversion system of claim 21, wherein the first lens array and the second lens array have a common substrate. 23. The polarization conversion system of claim 21, wherein the second lens array is proximate to and behind the polarization conversion element. 24. The polarization conversion system according to claim 21, wherein the polarization conversion element is arranged directly on the second lens array. 25. The polarization conversion system according to claim 21, wherein the polarization conversion element is disposed after the second lens and is optically coupled to the second lens array. 26. The output from the polarization splitting element comprises:
A first linearly polarized beam having a first vibrating surface and a second linearly polarized beam having a second vibrating surface different from the first vibrating surface, wherein the polarization conversion element or each polarization conversion element is polarized light. The polarization conversion system according to claim 1, which is a rotating element. 27. The vibrating surface of the first beam is the second beam.
27. The polarization conversion system of claim 26, wherein the polarization conversion system is substantially 90 ° with respect to the plane of vibration of the beam. 28. The one or more polarization conversion elements each include a retarder array having a plurality of first regions and a plurality of second regions, wherein the first and second regions are respectively the first and second regions. The polarization conversion system of claim 1, wherein the polarization conversion system is arranged to receive first and second polarizations. 29. The first and second regions have first and second sizes that are different from each other and match the cross-sectional size of the first and second polarized beams, respectively. The polarization conversion system described in. 30. A projection display system, comprising: An unpolarized or partially polarized light source, A polarization conversion system as defined in claim 1, A projection display system comprising a projection lens. 31. An optical element comprising a substrate, a first lens array disposed on one surface of the substrate, and each lens having a one-to-one correspondence with the first lens array. A second lens array disposed on the opposite surface of the substrate. 32. The optical element according to claim 31, wherein the first lens array and the second lens array are integrated with the substrate. 33. The optical element according to claim 31, wherein the pitch of the first lens array is substantially equal to the pitch of the second lens array. 34. The pitch of the first lens array and the pitch of the second lens array are each 2 m.
34. The optical element according to claim 33, which is m or less. 35. The optical element according to claim 31, wherein the width W of the optical element and the thickness T of the optical element satisfy the relationship of W / T> 3.