JP3744233B2 - Polarization separator and projection-type image display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarization separator used in an optical apparatus such as a projection-type image display apparatus, and more specifically, polarization separation that separates two polarized lights whose polarization planes are perpendicular by a combination of a blazed diffraction grating and a birefringent material. Related to the vessel.
[0002]
[Prior art]
A birefringent material is brought into close contact with a blazed diffraction grating, and the two polarizations are separated by utilizing the difference in refractive index of the birefringent material with respect to two polarized lights whose polarization planes are perpendicular to each other. The refractive index of the material of the blazed diffraction grating is N, the refractive index of the birefringent material with respect to the polarized light having the first polarization plane is No, and the birefringent material with respect to the polarized light having the second polarization plane perpendicular to the first polarization plane When the refractive index of Ne is Ne, the difference in refractive index at the diffraction grating surface is (No-N) for polarized light having the first polarization plane and (No-N) for polarized light having the second polarization plane ( Ne-N), and the difference in diffraction angle between the two polarized lights can be separated.
[0003]
JP-A-6-274927 discloses a magneto-optical head using this method. In this publication, minerals such as quartz and calcite are used as a birefringent material, and single wavelength light emitted from a laser light source is separated. In the first embodiment, the refractive index N of the diffraction grating is set to an intermediate value between the refractive indexes No and Ne of the birefringent material with respect to the two polarized lights, and the two polarized lights are extracted as ± first-order diffracted lights. In the second embodiment, the refractive index N of the diffraction grating is set equal to the refractive index No of the birefringent material with respect to the polarized light having the first polarization plane, and the polarization having the first polarization plane is changed to the zeroth order. As the diffracted light, polarized light having the second polarization plane is extracted as the first-order diffracted light.
[0004]
Actually, as in the first embodiment, there is not always a diffraction grating material having a refractive index N just between the refractive indexes No and Ne of the birefringent material. For this reason, as in the second embodiment, the refractive index N of the diffraction grating is made equal to one of the two refractive indexes No and Ne of the birefringent material, and one of the separated polarized lights is set to the 0th order. There are many.
[0005]
[Problems to be solved by the invention]
The apparatus of the above publication is useful when separating light with a small beam diameter, such as a magneto-optical head. However, an apparatus that requires a large light beam diameter, such as a projection-type image display apparatus such as a projection television or a data projector, requires a large-diameter birefringent material. Moreover, in order to display a bright image, it is necessary to increase the diffraction efficiency as much as possible, and the difference between the two refractive indexes of the birefringent material (No-Ne) must be increased. For this reason, minerals such as quartz are difficult to adopt as a birefringent material.
[0006]
A liquid crystal is a birefringent material that has no restriction on the diameter and has a large difference between two birefringences. If a thermoplastic resin or ultraviolet curable resin is used as the substrate material for the diffraction grating, the diffraction grating is formed by transfer from the mold, and the liquid crystal is aligned and adhered to it, the projection image display device A polarization separator having a required large diameter and high diffraction efficiency can be easily and efficiently manufactured.
[0007]
However, when the polarization separator is manufactured in such a manner, another problem arises in the configuration in which the 0th-order and 1st-order diffracted light is extracted as in the apparatus disclosed in the publication. Assuming that the wavelength of light to be separated is λ and the diffraction angle is θ, the arrangement pitch p of the grating for generating the first-order diffraction can be obtained by p = λ / sin θ. Further, the height h of the grating for maximizing the first-order diffraction efficiency is h = λ / (Ne−N).
[0008]
When the wavelength of light λ is 0.55 μm and the diffraction angle θ is 5 °, the grating pitch p is 6.3 μm to obtain the first-order diffracted light, and the refractive index difference (Ne−N) of the birefringent material is reduced. If it is 0.17, the grating height h is 3.2 μm. Such a blazed diffraction grating is very fine, and the influence of the diffraction grating fabrication accuracy such as mold fabrication accuracy and molding transfer accuracy greatly appears in the performance of the grating. FIGS. 12A and 12B show an ideal diffraction grating having the above numerical values and a diffraction grating when an edge of approximately 1 μm is generated at the edge of the grating due to the influence of fabrication accuracy. In the diffraction grating of (b), about 30% of the grating surface is leaked, and the diffraction efficiency is greatly reduced.
[0009]
Further, in the projection type image display device, light having a wavelength (0.45 to 0.65 μm) over the entire visible region is used to display a color image. Unlike the above, a difference in diffraction angle depending on the wavelength and a decrease in diffraction efficiency are problems. Since the diffraction angle changes in proportion to the wavelength, the diffraction angle of the same order of the light in the visible region is approximately 1.5 times different between the short wavelength side and the long wavelength side. FIG. 12 schematically shows first-order diffracted light of red (R) light, green (G) light, and blue (B) light. The light of the three colors R, G, and B travels in different directions due to the difference in diffraction angle. Actually, as shown in (b), the unnecessary light due to the grating is generated outside the R light and the B light.
[0010]
When a diffraction grating having a refractive index N of 1.50 (Nd) and an Abbe number ν of 64 (νd) and a birefringent material having a refractive index Ne of 1.67 and an Abbe number νe of 30 are used, The diffraction angle and diffraction efficiency of the first-order diffracted light of polarized light having a polarization plane are shown in FIGS. As is apparent from FIG. 13, when the diffraction angle of G light having a wavelength of 0.55 μm is 5.0 °, the diffraction angle from 0.45 μm B light to 0.65 μm R light is 4.1 °. It extends in the range of 1.8 ° from 5.9 ° to 5.9 °. Further, as shown in FIG. 14, when the diffraction efficiency of G light having a wavelength of 0.55 μm is 1, the diffraction efficiency of B light is greatly reduced to about 60 to 70%, and the diffraction efficiency of R light is also 80. It decreases to about ~ 90%. Since the refractive indexes N and No are equal, diffraction does not occur in the polarized light having the first polarization plane.
[0011]
As described above, the conventional polarization separator diffracts and separates light having a large light beam diameter having a spread in wavelength, and efficiently extracts polarized light in two or more desired wavelength bands at the same diffraction angle. I can't. It is an object of the present invention to provide a polarization separator that enables this, and to provide a projection-type image display device including such a polarization separator.
[0012]
[Means for Solving the Problems]
  To achieve the above object, the present invention comprises a first member on which a blazed diffraction grating is formed, and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member. In a polarization separator that transmits light of a wavelength having a broad range and separates the polarized light into a first polarized light and a second polarized light that are perpendicular to each other,The polarization plane of the first polarization is parallel or perpendicular to the arrangement direction of the grating of the blazed diffraction grating, and the polarization plane of the second polarization is relative to the polarization plane of the first polarization. Vertical,The absolute value of the difference between the first expression (No (λ) −N (λ)) · h / λ and the second expression (Ne (λ) −N (λ)) · h / λ isIt is approximately equal to the maximum wavelength of the spectral intensity distribution of light within the predetermined range.It is set to 3 or more and 10 or less with respect to the light of the reference wavelength. Here, h is the height of the grating of the blazed diffraction grating, N (λ) is the refractive index of the first member for light of wavelength λ, and No (λ) and Ne (λ) are the first of wavelength λ, respectively. The refractive index of the second member for the polarized light and the second polarized light.
[0013]
The first expression represents the diffraction order of the first polarized light having the wavelength λ, and the second expression represents the diffraction order of the second polarized light having the wavelength λ. Therefore, the diffraction orders of the two polarized lights having the reference wavelength separated by the polarization separator are different by at least 3 or more. In addition, the difference between the diffraction orders of both polarized lights is at most 10 or less.
[0014]
  By making the difference of the diffraction orders of the two polarizations to be separated to be 3 or more, the grating pitch of the blazed diffraction grating becomes 3 times or more compared to the case where the difference of the diffraction orders is 1. As a result, the ratio of any part due to the influence of the fabrication accuracy in the entire diffraction grating is greatly reduced, and the diffraction efficiency can be greatly improved. In addition, by setting the difference in diffraction order to 10 or less, generation of unnecessary diffraction due to the difference in Abbe number between the first member and the second member can be suppressed, and this also improves the diffraction efficiency.Further, by setting the wavelength in the vicinity of the maximum of the spectral intensity distribution of the transmitted light as the reference wavelength, it is possible to increase the diffraction efficiency for the entire wavelength range of the transmitted light.
[0015]
The order with high diffraction efficiency changes according to the wavelength, and the diffraction angle in the wavelength region with high diffraction efficiency falls within a narrow range compared to the diffraction angle of the first-order diffracted light. In other words, a plurality of diffraction wavelength bands having different diffraction orders appear within a relatively narrow diffraction angle range. Therefore, not only the light in the vicinity of the reference wavelength is efficiently separated into the first and second polarizations, but also the light having a wavelength away from the reference wavelength is efficiently separated into the first and second polarizations, and the latter The first and second polarized light beams travel in substantially the same direction as the former first and second polarized light beams, respectively.
[0016]
  The value of the second equation for the second polarization at the reference wavelength is preferably approximated to an integer within a range where the difference is less than 0.2. The pitch and height of the diffraction grating are set so as to meet this condition. The fact that the value of the second equation for the second polarization of the reference wavelength is close to an integer means that the intensity of the diffracted light at the integer order is close to the peak intensity. Therefore, the intensity of the diffracted second polarized light is high.
[0017]
  The present invention also includes a first member on which a blazed diffraction grating is formed and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member, and having a wavelength in a predetermined range. The polarization plane of the first polarized light is separated into the first polarized light and the second polarized light whose polarization planes are perpendicular to each other, and the polarization plane of the first polarization is the arrangement direction of the grating of the blazed diffraction grating The polarization plane of the second polarization is perpendicular to the polarization plane of the first polarization, and the first equation (No (λ) −N (λ)) · The absolute value of the difference between h / λ and the value of the second expression (Ne (λ) −N (λ)) · h / λ is 3 or more and 10 or less with respect to the light of the reference wavelength, and the predetermined value The range corresponds to the range from blue light to red light, and the reference wavelength is substantially equal to the center wavelength of green light. The second value of the expression for the second polarization of approximately equal three wavelengths with the center wavelength of the light and red light, the difference is in the range of less than 0.2, so as to approximate the three different integers each other.
  The present invention also includes a first member on which a blazed diffraction grating is formed and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member, and having a wavelength in a predetermined range. The polarization plane of the first polarized light is separated into the first polarized light and the second polarized light whose polarization planes are perpendicular to each other, and the polarization plane of the first polarization is the arrangement direction of the grating of the blazed diffraction grating The polarization plane of the second polarization is perpendicular to the polarization plane of the first polarization, and the first equation (No (λ) −N (λ)) · The absolute value of the difference between h / λ and the value of the second expression (Ne (λ) −N (λ)) · h / λ is 3 or more and 10 or less with respect to the light of the reference wavelength, and the predetermined value The range corresponds to the range from blue light to red light, and the reference wavelength is substantially equal to the center wavelength of green light. The first value of the expression for the first polarization of approximately equal three wavelengths with the center wavelength of the light and red light, the difference is in the range of less than 0.2, so as to approximate the three different integers each other.
  Here, h is the height of the grating of the blazed diffraction grating, N (λ) is the refractive index of the first member for light of wavelength λ, and No (λ) and Ne (λ) are the first of wavelength λ, respectively. The refractive index of the second member for the polarized light and the second polarized light.
  According to the above configuration, by setting the difference in diffraction order of the two polarized lights to be separated to 3 or more, the grating pitch of the blazed diffraction grating becomes 3 times or more compared to the case where the difference in diffraction order is 1. . As a result, the ratio of any part due to the influence of the fabrication accuracy in the entire diffraction grating is greatly reduced, and the diffraction efficiency can be greatly improved. In addition, by setting the difference in diffraction order to 10 or less, generation of unnecessary diffraction due to the difference in Abbe number between the first member and the second member can be suppressed, and this also improves the diffraction efficiency. Also,The second or first polarized light of each color of R, G, and B is diffracted by different orders, and the diffraction angles can be made substantially the same.
[0018]
In the present invention, the above-described polarization separator is provided in a projection-type image display device that separates light from a light source and uses the separated polarized light for image projection. Light from a light source can be efficiently polarized and separated. For example, even in a device that uses specific polarized light for projection, such as a configuration that modulates light with a liquid crystal panel, one of the separated polarized light A bright image can be displayed by performing polarization conversion that aligns the polarization plane with the other polarization plane. Further, since the R, G, and B three-color lights of each set of polarized light after separation can be advanced in substantially the same direction, the optical system can be made compact.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a polarization separator and a projection-type image display device (hereinafter also simply referred to as a projection display device) of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the optical system of the projection type image display device 1 of the first embodiment. The projection display device 1 decomposes the white light emitted from the light source into light of three colors R, G, and B, modulates the separated three colors of light individually with the three liquid crystal panels, and converts the modulated light. A color image is displayed by combining and projecting. In addition, in order to increase the efficiency of using light for projection, the light from the light source is polarized and separated, and the one polarized light after the separation is converted to match the other polarized light to obtain a linearly polarized light with a constant polarization plane. .
[0020]
The projection display device 1 includes a light source 11, a polarization separator 12 for polarization separation, an integrator 13 for light intensity uniformization and polarization conversion, three transmissive liquid crystal panels 21 R, 21 G, and 21 B for modulation, and A projection lens 27 is provided. Further, the projection display device 1 includes two dichroic mirrors 15a and 15b for decomposing light, three total reflection mirrors 16a, 16b and 16c for guiding the decomposed light to a liquid crystal panel, and two relay lenses 17a, 17b, and two dichroic mirrors 24 and 25 for synthesizing light modulated by the liquid crystal panel.
[0021]
Each of the three liquid crystal panels 21R, 21G, and 21B includes condenser lenses 22R, 22G, and 22B that collect incident light and condenser lenses 23R, 23G, and 23B that collect outgoing light. A dummy flat plate 26 is disposed between the liquid crystal panel 21 </ b> B and the dichroic mirror 25. The dichroic mirrors 24 and 25 for synthesis, the dummy flat plate 26 and the projection lens 27 form a projection optical system.
[0022]
The liquid crystal panels 21R, 21G, and 21B are the same size and have equivalent performance. Each of the liquid crystal panels 21R, 21G, and 21B is provided with a drive circuit (not shown), and these drive circuits are supplied with signals representing the R, G, and B components of the image, respectively. Therefore, the light modulated by the liquid crystal panel 21R is an R component image, the light modulated by the liquid crystal panel 21G is a G component image, and the light modulated by the liquid crystal panel 21B is a B component image.
[0023]
The liquid crystal panel 21G is located on the optical axis Ax of the projection lens 27 and is disposed perpendicular to the optical axis Ax. The dichroic mirror 24 is located on the optical axis Ax and is disposed on the projection lens 27 side in the vicinity of the liquid crystal panel 21G. The dichroic mirror 24 is disposed with an inclination of 45 ° with respect to the optical axis Ax. The dichroic mirror 25 is located on the optical axis Ax, and is disposed near the dichroic mirror 24 on the projection lens 27 side. The dichroic mirror 25 is disposed at an angle of 45 ° with respect to the optical axis Ax, and the dichroic mirrors 24 and 25 are perpendicular to each other.
[0024]
The liquid crystal panel 21R is disposed symmetrically with the liquid crystal panel 21G with respect to the dichroic mirror 24. The liquid crystal panel 21B is arranged symmetrically with the liquid crystal panel 21G with respect to the dichroic mirror 25, and the dummy flat plate 26 is also arranged symmetrically with the dichroic mirror 24 with respect to the dichroic mirror 25.
[0025]
The condenser lenses 22R, 22G, and 22B are arranged so that their optical axes are perpendicular to the liquid crystal panels 21R, 21G, and 21B, respectively. The same applies to the condenser lenses 23R, 23G, and 23B.
[0026]
The dichroic mirrors 24 and 25 are high-precision sandwich mirrors in which a reflective film is sandwiched between two flat glass plates, and both are the same size and the same thickness. The reflecting film of the dichroic mirror 24 is set so as to reflect R light and transmit G light and B light. The reflective film of the dichroic mirror 25 is set so as to reflect B light and transmit G light and R light. The dummy flat plate 26 is made of the same material as the dichroic mirrors 24 and 25, and has the same size and thickness. However, no reflective film is formed on the dummy flat plate 26.
[0027]
The dichroic mirror 15b is located on the opposite side of the projection lens 27 with respect to the liquid crystal panel 21G on the optical axis Ax, and is arranged in parallel with the dichroic mirror 24. The dichroic mirror 15b is set to transmit B light and reflect R light and G light. The total reflection mirror 16 a is arranged symmetrically with the dichroic mirror 15 b with respect to the dichroic mirror 24. The dichroic mirror 15a is located on the intersection of the optical axis Ax folded by the dichroic mirror 15b and the optical axis Ax folded twice by the dichroic mirror 24 and the total reflection mirror 16a, and is arranged in parallel with the dichroic mirror 24. Yes. The dichroic mirror 15a is set to transmit R light and reflect G light and B light.
[0028]
The total reflection mirror 16 c is located on the optical axis Ax turned back by the dichroic mirror 25 and is arranged in parallel with the dichroic mirror 25. The total reflection mirror 16b is located on the intersection of the optical axis Ax folded twice by the dichroic mirror 25 and the total reflection mirror 16c and the extension line of the optical axis Ax folded by the dichroic mirror 15b, and is parallel to the dichroic mirror 24. Are arranged.
[0029]
The light source 11 has a metal halide lamp 11a and a parabolic reflector 11b, and is located on the opposite side of the total reflection mirror 16a with respect to the dichroic mirror 15a. The light source 11 is arranged so that the optical axis of the reflector 11b coincides with the optical axis Ax that is folded twice by the dichroic mirror 24 and the total reflection mirror 16a. The lamp 11a is located at the focal point of the reflector 11b.
[0030]
The polarization separator 12 is located between the light source 11 and the dichroic mirror 15a, and the integrator 13 is located between the polarization separator 12 and the dichroic mirror 15a. The polarization separator 12 and the integrator 13 are arranged perpendicular to the optical axis Ax that is folded twice by the dichroic mirror 24 and the total reflection mirror 16a.
[0031]
The relay lenses 17a and 17b are located between the dichroic mirror 15b and the total reflection mirror 16b and between the total reflection mirror 16b and the total reflection mirror 16c, respectively. The optical axes of the relay lenses 17a and 17b are perpendicular and parallel to the optical axis Ax, respectively.
[0032]
The optical path length from the dichroic mirror 15a through the total reflection mirror 16a to the liquid crystal panel 21R is equal to the optical path length from the dichroic mirror 15a through the dichroic mirror 15b to the liquid crystal panel 21G, but the dichroic mirror 15a to the dichroic mirror 15b and the total reflection mirror are the same. The optical path length from 16b and 16c to the liquid crystal panel 21B is different from these. The relay lenses 17a and 17b are arranged to correct this optical path length difference and make the light incident on the liquid crystal panel 21B substantially equivalent to the light incident on the liquid crystal panels 21R and 21G.
[0033]
In the optical path from the liquid crystal panels 21R and 21G to the projection lens 27, there are two dichroic mirrors 24 and 25 that are oblique to the optical axis Ax. In order to correct the aberration of light from the liquid crystal panels 21R and 21G caused thereby, the projection lens 27 is provided with a cylinder lens 27a formed by molding plastic. The axis of the cylinder lens 27a is parallel to the optical axis Ax turned back by the dichroic mirror 24 or 25.
[0034]
On the other hand, the dichroic mirror 24 does not exist in the optical path from the liquid crystal panel 21B to the projection lens 27, and the light from the liquid crystal panel 21B becomes non-equivalent to the light from the liquid crystal panels 21R and 21G and excessively receives correction. . In order to prevent this, a dummy flat plate 26 is disposed between the liquid crystal panel 21B and the dichroic mirror 25. The projection lens 27 includes a large-aperture aspheric lens 27b formed by molding plastic in the front group, and has a diaphragm 27c between the middle group and the rear group.
[0035]
The configuration of the light source 11, the polarization separator 12, and the integrator 13 is shown in FIG. The light source 11 has a UV / IR cut filter 11c in front of the reflector 11b. The light emitted from the lamp 11a is reflected by the reflector 11b to become a parallel light beam, and is transmitted through the UV / IR cut filter 11c, thereby removing the wavelength components in the ultraviolet region and the infrared region, and the wavelength component in the visible region (wavelength 0). .45 to 0.65 μm). This light is a set of polarized components whose oscillation directions are disordered.
[0036]
The polarization separator 12 includes a grating substrate 12a on which a blazed diffraction grating is formed, a flat plate 12c arranged in parallel to face the grating surface of the grating substrate 12a, and a liquid crystal sandwiched between the grating substrate 12a and the flat plate 12c. 12b. The diffraction gratings of the grating substrate 12a are arranged in parallel with the inclined surfaces of the gratings aligned in the same direction. The refractive index of the lattice substrate 12a is isotropic, and the refractive index is represented by N. The lattice substrate 12a is made of a thermoplastic resin such as acrylic and can be mass-produced using a mold. The material of the lattice substrate 12a is not limited to the thermoplastic resin, and for example, an ultraviolet curable resin can be used, and in this case, it can be mass-produced using a mold.
[0037]
The liquid crystal 12b is a birefringent material and has anisotropy in refractive index. The liquid crystal 12b has a refractive index with respect to a polarized light PY (shown by a solid line in the figure) having a polarization plane Y (shown by an arrow in the figure) in the arrangement direction of the grating of the grating substrate 12a, and a polarization plane X perpendicular to the polarization plane Y. The refractive index with respect to the polarized light PX (shown by a broken line in the figure) having (shown by a circle in the figure) is oriented differently. The refractive index for the polarized light PY of the liquid crystal 12b is represented by No, and the refractive index for the polarized light PX is represented by Ne.
[0038]
Refractive indexes N, No, and Ne change according to the wavelength of light to be transmitted. Refractive indexes for light of wavelength λ are represented by N (λ), No (λ), and Ne (λ). The change in the refractive index increases as the dispersion increases, and as the Abbe number decreases. Here, the Abbe number ν of the grating substrate 12a and the Abbe number νo of the liquid crystal 12b with respect to the polarized light PY are increased, and the liquid crystal 12b with respect to the refractive index N of the grating substrate 12a and the polarized light PY is excluded except for a part of the short wavelength region. The refractive indexes No of the same are made equal. Further, the refractive index Ne of the liquid crystal 12b with respect to the polarized light PX is made larger than the refractive index N of the lattice substrate 12a. The refractive index N of the lattice substrate 12a, the refractive indexes No and Ne of the liquid crystal 12b, and the pitch and height of the lattice of the lattice substrate 12a will be described later with specific numerical values.
[0039]
Since the refractive index N of the grating substrate 12a and the refractive index Ne of the liquid crystal 12b are different, the polarized light PX having the polarization plane X out of the light incident from the light source 11 is diffracted in the arrangement direction of the grating. On the other hand, since the refractive index N of the grating substrate 12a is equal to the refractive index No of the liquid crystal 12b, the polarized light PY having the polarization plane Y out of the light incident from the light source 11 goes straight without being diffracted. As a result, the light from the light source 11 is separated into these two polarized lights PX and PY whose polarization planes are vertical.
[0040]
The integrator 13 includes a first lens array 13a in which lens cells are two-dimensionally arranged, and a second lens array 13b in which lens cells are arranged corresponding to the lens array 13a. These lens arrays 13a and 13b are arranged in parallel, and the optical axis of each lens cell of the lens array 13a is perpendicular to the array surface. The lens cells of the second lens array 13b are formed eccentrically.
[0041]
Each lens cell of the first lens array 13a forms an image of light incident from the polarization separator 12 on a corresponding lens cell of the second lens array 13b. At this time, since the polarized light PX and the polarized light PY are separated, they are imaged at different positions on each lens cell of the second lens array 13b. The polarized light PY is perpendicularly incident on the first lens array 13a and forms an image on the optical axis of the lens cell of the lens array 13b. On the other hand, the polarized light PX is incident on the first lens array 13a while being inclined by the diffraction angle by the polarization separator 12, and forms an image at a position off the optical axis of the lens cell of the lens array 13b. The lens cell of the second lens array 13b is decentered so that the polarized light PX that forms an image at a position off the optical axis travels in parallel with the polarized light PY after transmission.
[0042]
The second lens array 13b is set so that light transmitted through each lens cell is incident on the entire panel surface of the liquid crystal panels 21R, 21G, and 21B. Light from all lens cells of the second lens array 13b also enters the part. This eliminates unevenness in the intensity distribution of the light emitted from the light source 11, and each liquid crystal panel receives light with a uniform intensity distribution. The second lens array 13b is set so that all the light transmitted through the respective lens cells is incident on the liquid crystal panels 21R, 21G, and 21B, and the light from the integrator 13 is guided to each liquid crystal panel without loss. It is burned.
[0043]
On the surface of the second lens array 13b on the first lens array 13a side, a half-wave plate 14 extending in a direction along each grating of the grating substrate 12a (a direction perpendicular to the paper surface) is provided. The half-wave plates 14 are provided in the same number as the number of lens cells in the grating arrangement direction, and are arranged at positions where the polarized light PX passes. The polarization plane of the polarized light PX changes by 90 ° by passing through the half-wave plate 14. On the other hand, the polarized light PY does not pass through the half-wave plate 14, and its polarization plane does not change. In this way, the light incident on the second lens array 13b, and hence the light emitted from the integrator 13, becomes the polarized light PY having the polarization plane Y.
[0044]
The light emitted from the light source 11 is used for modulation without waste because the half-wave plate 14 performs polarization conversion and the integrator 13 guides the light to the liquid crystal panels 21R, 21G, and 21B without loss. Note that the half-wave plate 14 may be disposed not at a position where the polarized light PX passes but at a position where the polarized light PY passes. In that case, all of the light given to the liquid crystal panels 21R, 21G, and 21B becomes the polarized light PX having the polarization plane X.
[0045]
The light from the integrator 13 enters the dichroic mirror 15a and is decomposed into R light that is transmitted and G light and B light that are reflected. The R light is reflected by the total reflection mirror 16a, enters the liquid crystal panel 21R through the condenser lens 22R, and is modulated according to the R signal while passing through this. The modulated R light transmitted through the liquid crystal panel 21R is incident on the dichroic mirror 24 through the condenser lens 23R and reflected, and then incident on the dichroic mirror 25 and transmitted therethrough, and then enters the projection lens 27 and enters the screen. Projected towards. The projected R light forms an image on the screen to form an R component image.
[0046]
The G light and B light reflected by the dichroic mirror 15a enter the dichroic mirror 15b, and are decomposed into reflected G light and transmitted B light. The G light is incident on the liquid crystal panel 21G through the condenser lens 22G, and is modulated in accordance with the G signal while passing through the condenser lens 22G. The modulated G light transmitted through the liquid crystal panel 21G enters the dichroic mirror 24 through the condenser lens 23G and is transmitted therethrough, then enters the dichroic mirror 25 and is transmitted therethrough, and enters the projection lens 27. Projected toward the screen. The projected G light forms an image on the screen to form a G component image.
[0047]
The B light transmitted through the dichroic mirror 15b is reflected by the total reflection mirror 16b through the relay lens 17a, and further reflected by the total reflection mirror 16c through the relay lens 17b. The B light reflected by the total reflection mirror 16c enters the liquid crystal panel 21B through the condenser lens 22B, and is modulated according to the B signal while passing through the condenser lens 22B. The modulated B light transmitted through the liquid crystal panel 21B passes through the condenser lens 23B and enters the dummy flat plate 26, then passes through the condenser plate 23B, then enters the dichroic mirror 25, is reflected, enters the projection lens 27, and enters the screen. Projected towards. The projected B light forms an image on the screen to form a B component image.
[0048]
The R light and G light individually modulated by the liquid crystal panels 21R and 21G are combined by the dichroic mirror 24, and the B light modulated by the liquid crystal panel 21B is further combined with the combined light to produce three colors. The light of the two overlaps and forms an image on the screen without deviation. Thereby, a color image is displayed on the screen.
[0049]
The polarization separator 12 will be described. If the wavelength of light incident on the polarization separator 12 is λ, the pitch of the grating of the grating substrate 12a is p, and the height of the grating is h, the diffraction order me (λ) and polarization of the polarized light PX having the polarization plane X The diffraction order mo (λ) of the polarized light PY having the plane Y is
me (λ) = (Ne (λ) −N (λ)) · h / λ
mo (λ) = (No (λ) −N (λ)) · h / λ
Sought by. Further, the diffraction angle θe (λ) of the polarized light PX and the diffraction angle θo (λ) of the polarized light PY at these diffraction orders are:
sin (θe (λ)) = λ · me (λ) / p
sin (θo (λ)) = λ · mo (λ) / p
It becomes.
[0050]
The refractive index N of the grating substrate 12a is 1.50 (Nd), and the Abbe number ν is 64 (νd). The refractive index Ne of the liquid crystal 12b with respect to the polarized light PX having the polarization plane X is 1.67, and the Abbe number νe is 30. Further, the refractive index No of the liquid crystal 12b with respect to the polarized light PY is equal to the refractive index N as described above, and is 1.50, and its Abbe number νo is 40.
[0051]
The peak of the spectral intensity distribution of the light emitted from the light source 11 is in the G light region, and the polarization separator 12 sets the reference wavelength λ0 to 0.55 μm near the peak wavelength, and sets the polarizations PX and PY of the reference wavelength λ0 to about 5 It is set so as to be separated at an angle of °. The polarized light PY does not diffract and is extracted as 0th-order diffracted light with a diffraction angle of 0 °. Accordingly, the polarized light PX is extracted at a diffraction angle of about 5 °, and the polarization separator 12 is set so that the diffraction order of the polarized light PX becomes the 6th order. That is, me (λ0) = 6 and mo (λ0) = 0.
[0052]
The pitch p and height h of the grating for satisfying the above diffraction conditions are p = 37.9 μm and h = 18.9 μm, respectively, and the grating of the grating substrate 12a is set to these values. A diffraction grating of the grating substrate 12a is shown in FIG. FIG. 3 shows not an ideal grating, but a grating in which a sagging of about 1 μm occurs at the edge of the grating due to the influence of fabrication accuracy. (A) represents the diffraction of the polarized light PX, and (b) represents the diffraction of the polarized light PY. This grating is substantially similar to the diffraction grating for extracting the first-order diffracted light shown in FIG. However, since the grating of the grating substrate 12a is about six times the size of the grating shown in FIG. 12, the ratio of the portion of the entire diffraction grating due to the influence of the fabrication accuracy is about 5% of 1/6. Efficiency is greatly improved.
[0053]
FIG. 4 shows the relationship between the wavelength, diffraction angle, and diffraction order of the polarized light PX having the polarization plane X, and FIG. 5 shows the relationship between the wavelength and diffraction efficiency. As shown in FIG. 4, near the diffraction angle of 5 °, sixth-order diffraction occurs at the reference wavelength λ0, fifth-order diffraction occurs near the longer wavelength of 0.65 μm, and near the shorter wavelength of 0.47 μm. Seventh order diffraction occurs. As shown in FIG. 5, the maximum intensity of the sixth-order diffracted light is in the vicinity of the reference wavelength of 0.55 μm, and the maximum intensities of the fifth-order and seventh-order diffracted lights are in the vicinity of 0.63 μm and 0.49 μm, respectively.
[0054]
In FIG. 4, the hatched range represents a range in which the intensity of each of the fifth, sixth, and seventh order diffracted lights is greater than or equal to the intensity of the diffracted lights of other orders. This range falls within the range of 4.4 to 5.5 ° in terms of diffraction angle, and particularly strong intensity is concentrated in the vicinity of the diffraction angle of 5 °. For example, the intensity range of 80% or more of the maximum intensity is 4.6 to 5.3 °. The diffracted light of 0.58 μm and 0.52 μm generated at a diffraction angle away from 5 ° is a boundary region of R light, G light, and G light and B light, respectively. It is light of an unnecessary wavelength that is not used to increase color purity.
[0055]
The wavelength of the maximum intensity of the fifth order light 0.63 μm, the wavelength of the maximum intensity of the sixth order light 0.55 μm, and the wavelength of the maximum intensity of the seventh order light 0.49 μm are near the center of the R, G, and B primary color lights, respectively. The diffraction angle of each central wavelength falls within the range of 4.8 to 5.2 °. When the center wavelengths of R light, G light, and B light are expressed by λR, λG, and λB, respectively, me (λG) = me (λ0) = 6, me (λR)≒5, me (λB)≒7 Where the approximate equal sign≒Represents that the diffraction order obtained by calculation is an integer within a range of ± 0.2.
[0056]
Thus, when there are a plurality of important wavelengths in the wavelength to be used, it is preferable to diffract those important wavelengths with different orders and to reduce the difference in diffraction angles. By reducing the difference in diffraction angle, in this projection display device 1, it is not necessary to increase the width of the half-wave plate 14, and the lens arrays 13 a and 13 b constituting the integrator 13 are reduced, and between them. The distance can be shortened. Thereby, not only the integrator 13 itself is miniaturized, but also other components are miniaturized, and the entire projection display device 1 is small and light.
[0057]
As described above, the polarized light PY having the polarization plane Y is extracted as 0th-order light having a diffraction angle of 0 °. FIG. 6 shows the relationship between the wavelength of the polarized light PY and the diffraction efficiency. As shown in this figure, the diffraction efficiency is constant in the wavelength range of 0.53 μm or more, but decreases at wavelengths shorter than this, and reaches about 80% at the wavelength of 0.45 μm. This is because, due to the difference between the Abbe number ν of the grating substrate 12a and the Abbe number νo of the liquid crystal 12b with respect to the polarized light PY, first-order or higher diffraction is slightly generated at a short wavelength.
[0058]
In producing the polarization separator 12, it is desirable to minimize the lattice deflection as much as possible. However, no matter how the processing technology advances, it is unavoidable that errors in the processing accuracy include errors, and that any grating caused by this causes a decrease in diffraction efficiency. In order to reduce the influence of grating drift on the diffraction efficiency and reduce the difference in diffraction angle over a wide wavelength range, the difference between the diffraction orders me (λ0) and mo (λ0) of the polarized light PX and PY having the reference wavelength λ0 Is better, and it is necessary that 3 ≦ | me (λ0) −mo (λ0) |. In the polarization separator 12, | me (λ0) −mo (λ0) | = 6, and this condition is satisfied.
[0059]
A decrease in the zero-order diffraction efficiency of the polarized light PY can be prevented by making the Abbe numbers ν and νo of the grating substrate 12a and the liquid crystal 12b equal. However, in general, liquid crystal has a characteristic that its Abbe number is smaller than that of glass or plastic, so that it is almost impossible to actually achieve this condition with liquid crystal. It is also possible to find a combination of an isotropic material and a birefringent material in which the refractive index N is equal to the refractive index No, the Abbe number ν is equal to the Abbe number νo, and the difference between the refractive index N and the refractive index Ne is large. Almost impossible.
[0060]
A decrease in diffraction efficiency of a desired order due to the occurrence of unnecessary order diffraction becomes more significant as the difference between the diffraction orders me (λ0) and mo (λ0) of the polarized light beams PX and PY becomes larger. Therefore, | me (λ0) −mo (λ0) | ≦ 10 is preferable. In order to increase the difference between the diffraction orders me (λ0) and mo (λ0), it is necessary to increase the height h of the grating. If the height h of the grating is increased, the thickness of the birefringent material is greatly different between the peak and valley portions of the grating, and when the liquid crystal is used as the birefringent material as in this embodiment, It becomes difficult to make the orientation constant. Also in this respect, it can be said that the difference between the diffraction orders me (λ0) and mo (λ0) is preferably 10 or less. This condition is also satisfied in the polarization separator 12.
[0061]
The projection type image display apparatus 2 of 2nd Embodiment is demonstrated. The projection display device 2 of the present embodiment is the same as the projection display device 1 described above except for the configuration of the polarization separator and the integrator. The same components as those of the projection display device 1 are denoted by the same reference numerals, and the description of the entire configuration of the optical system already described with reference to FIG. 1 is omitted.
[0062]
FIG. 7 shows the configuration of the light source 11, the polarization separator 32, and the integrator 33 in the projection display device 2. The polarization separator 32 includes a grating substrate 32a on which a blazed diffraction grating is formed, a flat plate 32c arranged in parallel to face the grating surface of the grating substrate 32a, and a liquid crystal sandwiched between the grating substrate 32a and the flat plate 32c. 32b. The diffraction grating of the grating substrate 32a is formed symmetrically with respect to the center in the arrangement direction of the grating, and the half inclined surface is opposite to the other half inclined surface.
[0063]
The liquid crystal 32b is oriented so that the refractive index for the polarized light PY having the polarization plane Y in the arrangement direction of the grating of the grating substrate 32a is different from the refractive index for the polarized light PX having the polarization plane X perpendicular to the polarization plane Y. Has been. The refractive index of the lattice substrate 32a and the refractive index of the liquid crystal 32b with respect to the polarized light PY and the polarized light PX are represented by N, No, and Ne, respectively, as in the first embodiment.
[0064]
The refractive index N of the grating substrate 32a is set to a value between the two refractive indexes No and Ne of the liquid crystal, and the polarization separator 32 uses the polarized light PX as a positive order diffracted light and the polarized light PY as a negative diffracted light. Both are separated as diffracted light of the order.
[0065]
The integrator 33 includes a first lens array 33a in which lens cells are two-dimensionally arranged, and a second lens array 33b in which lens cells are arranged corresponding to the lens array 33a. The lens arrays 33a and 33b are arranged in parallel, and the optical axis of each lens cell of the lens arrays 33a and 33b is perpendicular to the array surface. Further, the optical axis of each lens cell of the first lens array 33a and the optical axis of the corresponding lens cell of the second lens array 33b coincide.
[0066]
Although the lens cells of the second lens array 33b are formed eccentrically, the lens cells of the second lens array 33b are also arranged symmetrically in correspondence with the diffraction grating of the grating substrate 32a being symmetrical. . Further, since the diffraction angles of the polarized light PX and PY by the polarization separator 32 are positive and negative, the degree of decentering of the lens cell of the lens array 33b is smaller than the lens cell of the lens array 13b of the projection display device 1.
[0067]
Each lens cell of the first lens array 33a forms an image of light incident from the polarization separator 32 on a corresponding lens cell of the second lens array 33b. At this time, since the polarized light PX and the polarized light PY are separated, they are imaged at different positions on each lens cell of the second lens array 33b. The polarized light PX and the polarized light PY form an image at a position deviating from the optical axis of the lens cell of the lens array 33b, and the two imaging positions are on the opposite side with respect to the optical axis of the lens cell. Both polarized light beams transmitted through the lens array 32b travel parallel to the optical axis of the lens cell.
[0068]
The second lens array 33b is set so that light transmitted through each lens cell is incident on the entire panel surface of the liquid crystal panels 21R, 21G, and 21B. Light from all lens cells of the second lens array 33b also enters the part. This eliminates unevenness in the intensity distribution of the light emitted from the light source 11, and each liquid crystal panel receives light with a uniform intensity distribution. The second lens array 33b is set so that all the light transmitted through each lens cell is incident on the liquid crystal panels 21R, 21G, and 21B, and the light from the integrator 33 is guided to each liquid crystal panel without loss. It is burned.
[0069]
In addition, since the polarization separator 32 and the integrator 33 are configured symmetrically, the light guided to each liquid crystal panel is such that the symmetrical portions of the light beams exiting the lens array 33b overlap each other. For this reason, even if the diffraction efficiency varies depending on the wavelength and unevenness in intensity occurs in the luminous flux, the unevenness in intensity is canceled out, and unevenness in color is prevented from occurring in the displayed image.
[0070]
On the surface of the second lens array 33b on the first lens array 33a side, a half-wave plate 34 extending in a direction along each grating of the grating substrate 32a (a direction perpendicular to the paper surface) is provided. The half-wave plates 34 are provided in the same number as the number of lens cells in the grating arrangement direction, and are arranged at positions where the polarized light PX passes. The half-wave plates 34 are also arranged symmetrically, and the two half-wave plates 34 at the center are integrated to be approximately twice the size. The polarization plane of the polarized light PX changes by 90 ° by passing through the half-wave plate 34. On the other hand, the polarized light PY does not pass through the half-wave plate 34 and its polarization plane does not change. Therefore, all the light emitted from the integrator 33 becomes the polarized light PY having the polarization plane Y.
[0071]
The refractive index N of the grating substrate 32a of the polarization separator 32 is 1.59 (Nd), and the Abbe number ν is 35 (νd). The refractive index Ne of the liquid crystal 32b with respect to the polarized light PX is 1.73, and the Abbe number νe is 25. The refractive index No of the liquid crystal 32b with respect to the polarized light PY is 1.50, and the Abbe number νo is 30.
[0072]
The polarization separator 32 is set so as to separate the polarized light rays PX and PY having the reference wavelength λ0 into an angle of about 5 ° with 0.55 μm near the wavelength of the peak intensity of the light from the light source 11 as the reference wavelength λ0. Yes. The diffraction orders of the reference wavelength λ0 are me (λ0) = 4.9 and mo (λ0) = − 3.1. In the vicinity of the reference wavelength λ 0, fifth-order diffraction occurs in the polarized light PX, and the diffraction angle is 3.1 °. The polarization PY undergoes -3rd order diffraction, and its diffraction angle is -1.9 °.
[0073]
FIG. 8 shows the relationship between the wavelength, diffraction angle, and diffraction order of the polarized light PX having the polarization plane X, and FIG. 9 shows the relationship between the wavelength and diffraction efficiency. As shown in FIG. 8, near the diffraction angle of 3 °, fifth-order diffraction occurs at the reference wavelength λ0, fourth-order diffraction occurs near the longer wavelength of 0.65 μm, and near the shorter wavelength of 0.47 μm. Sixth-order diffraction occurs. As shown in FIG. 9, the maximum intensity of the fifth-order diffracted light is in the vicinity of a wavelength of 0.54 μm, and the maximum intensities of the fourth-order and sixth-order diffracted lights are in the vicinity of 0.64 μm and 0.47 μm, respectively.
[0074]
In FIG. 8, the hatched range represents a range in which the intensity of each of the fourth-order, fifth-order, and sixth-order diffracted lights is greater than or equal to the intensity of the diffracted lights of other orders. This range falls within the range of 2.6 to 3.4 ° with respect to the diffraction angle, and particularly strong intensity is concentrated in the vicinity of the diffraction angle of 3 °. For example, the intensity range of 80% or more of the maximum intensity is 2.8 to 3.3 °. Diffracted light of 0.58 μm and 0.50 μm generated at a diffraction angle away from 3 ° is a boundary region between R light and G light, and G light and B light, and has low intensity.
[0075]
The wavelength of the maximum intensity of the 4th order light is 0.64 μm, the wavelength of the maximum intensity of the 5th order light is 0.54 μm, and the wavelength of the maximum intensity of the 6th order light is 0.47 μm, and the diffraction angle is 2.9 to 3.2 °. Fits almost within. The diffraction orders of the center wavelengths λR, λG, and λB of R light, G light, and B light are me (λG)=me (λ0)≒5, me (λR)≒4, me (λB)≒6Here, the approximate equal sign≈ means that the diffraction order obtained by calculation becomes an integer within a range of ± 0.2.
[0076]
FIG. 10 shows the relationship between the wavelength, diffraction angle, and diffraction order of the polarized light PY having the polarization plane Y, and FIG. 11 shows the relationship between the wavelength and diffraction efficiency. As shown in FIG. 10, -3rd-order diffraction occurs near the diffraction angle of -2 ° over the entire wavelength in the visible region except a part on the short wavelength side, and -4th-order diffraction occurs at short wavelengths. Yes. In FIG. 10, the hatched range represents a range in which the intensity of each of the -3rd-order and -4th-order diffracted lights is greater than or equal to the intensity of diffracted lights of other orders. When this range is seen with respect to the diffraction angle, it falls within the range of -2.2 to -1.6 °.
[0077]
The difference between the diffraction orders me (λ0) and mo (λ0) of the polarizations PX and PY having the reference wavelength λ0 is 8. In the polarization separator 32 of the present embodiment, 3 ≦ | me (λ0) −mo (λ0) The condition of | ≦ 10 is satisfied. This makes it possible to reduce the effect of grating drift on the diffraction efficiency, to reduce the difference in diffraction angle over a wide wavelength range, and to reduce the diffraction efficiency due to the generation of unwanted orders of diffraction. Is prevented, and the alignment of the liquid crystal 32b is easily made uniform.
[0078]
Although an example of a projection type image display device that modulates light by a transmissive liquid crystal panel is shown here, the polarization separator of each embodiment is a projection type image display device that modulates light by a reflective liquid crystal panel. The present invention is also applicable to optical devices other than projection type image display devices.
[0079]
【The invention's effect】
  Of the present inventionWhen the polarization separator is used, the grating pitch of the blazed diffraction grating is increased, and the influence of the production accuracy of the diffraction grating hardly appears in the diffraction efficiency, and polarization separation can be performed with an efficiency close to ideal. Moreover, it is possible to simultaneously separate and split light having different wavelengths, and the diffraction angles of the respective wavelengths are not so different, and polarized light having different wavelengths can be guided in the same direction after separation.
[0080]
In particular, by setting the wavelength near the maximum intensity of the transmitted light as a reference wavelength and approximating the diffraction order of the second polarized light of this wavelength to an integer, the overall diffraction efficiency including other wavelengths increases, It can be used effectively.
[0081]
The wavelength range of light to be transmitted is a range corresponding to blue light to red light, and three wavelengths of the second polarized light or the first polarized light having three wavelengths substantially equal to the center wavelengths of blue light, green light, and red light are used. By approximating the diffraction orders to three different integers, light of three colors R, G, and B can be polarized and separated, and each separated light can be guided in the same direction.
[0082]
The projection-type image display device of the present invention can display a bright image with high use efficiency of light from the light source. In addition, when displaying a color image, the traveling directions of the three colors R, G, and B after polarization separation can be made substantially the same direction, so the optical system becomes smaller and the entire apparatus is also smaller. Turn into.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of an optical system of a projection type image display apparatus according to first and second embodiments.
FIG. 2 is a diagram illustrating a configuration of a light source, a polarization separator, an integrator, and a half-wave plate according to the first embodiment.
FIG. 3 is a diagram schematically illustrating a diffraction grating of the polarization separator according to the first embodiment.
FIG. 4 is a diagram illustrating a relationship among a wavelength, a diffraction angle, and a diffraction order of polarized light PX in the polarization separator according to the first embodiment.
FIG. 5 is a diagram showing the relationship between the wavelength of polarized light PX and the diffraction efficiency in the polarization separator according to the first embodiment.
FIG. 6 is a diagram showing the relationship between the wavelength of polarized light PY and the diffraction efficiency in the polarization separator according to the first embodiment.
FIG. 7 is a diagram illustrating a configuration of a light source, a polarization separator, an integrator, and a half-wave plate according to a second embodiment.
FIG. 8 is a diagram illustrating a relationship among a wavelength, a diffraction angle, and a diffraction order of polarized light PX in the polarization separator according to the second embodiment.
FIG. 9 is a diagram showing the relationship between the wavelength of polarized light PX and the diffraction efficiency in the polarization separator according to the second embodiment.
FIG. 10 is a diagram illustrating a relationship among a wavelength, a diffraction angle, and a diffraction order of polarized light PY in the polarization separator according to the second embodiment.
FIG. 11 is a diagram showing the relationship between the wavelength of polarized light PY and the diffraction efficiency in the polarization separator of the second embodiment.
FIGS. 12A and 12B are diagrams illustrating an ideal state of a diffraction grating that extracts first-order diffracted light and a state in which the edge of the grating is bent due to the influence of fabrication accuracy. FIGS.
FIG. 13 is a diagram showing an example of the relationship between the wavelength of polarized light and the diffraction angle in a diffraction grating that takes out first-order diffracted light.
FIG. 14 is a diagram showing an example of the relationship between the wavelength of polarized light and the diffraction efficiency in a diffraction grating that extracts first-order diffracted light.
[Explanation of symbols]
1, 2 Projection type image display device
11 Light source
11a lamp
11b reflector
11c UV / IR cut filter
12, 32 Polarization separator
12a, 32a Lattice substrate
12b, 32b liquid crystal
12c, 32c flat plate
13, 33 Integrator
13a, 33a Lens array
13b, 33b Lens array
14, 34 1/2 wavelength plate
15a, 15b Dichroic mirror
16a, 16b, 16c Total reflection mirror
17a, 17b Relay lens
21R, 21G, 21B Transmission type liquid crystal panel
22R, 22G, 22B condenser lenses
23R, 23G, 23B condenser lenses
24, 25 Dichroic mirror
26 Dummy plate
27 Projection lens
27a cylinder lens
27b Aspherical lens
27c Aperture

Claims (5)

A first member on which a blazed diffraction grating is formed; and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member, and transmitting light having a wavelength in a predetermined range. In the polarization separator that separates the first polarized light and the second polarized light whose polarization planes are perpendicular to each other,
The polarization plane of the first polarization is parallel or perpendicular to the arrangement direction of the grating of the blazed diffraction grating, and the polarization plane of the second polarization is relative to the polarization plane of the first polarization. Vertical,
The height of the blazed diffraction grating is h,
The refractive index of the first member for light of wavelength λ is N (λ),
The refractive index of the second member for the first polarized light with the wavelength λ is No (λ),
The refractive index of the second member for the second polarized light of wavelength λ is Ne (λ)
When expressed by
The first equation (No (λ) −N (λ)) · h / λ and the second equation (Ne (λ) −N (λ)) · h / λ
The polarization separator according to claim 1, wherein the absolute value of the difference between the values is 3 or more and 10 or less with respect to light having a reference wavelength substantially equal to the maximum wavelength of the spectral intensity distribution of light within the predetermined range . The polarization separator according to claim 1, wherein the value of the second equation for the second polarization of the reference wavelength is approximated to an integer within a range where the difference is less than 0.2. A first member on which a blazed diffraction grating is formed; and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member, and transmitting light having a wavelength in a predetermined range. In the polarization separator that separates the first polarized light and the second polarized light whose polarization planes are perpendicular to each other,
The polarization plane of the first polarization is parallel or perpendicular to the arrangement direction of the grating of the blazed diffraction grating, and the polarization plane of the second polarization is relative to the polarization plane of the first polarization. Vertical,
The height of the blazed diffraction grating is h,
The refractive index of the first member for light of wavelength λ is N (λ),
The refractive index of the second member for the first polarized light with the wavelength λ is No (λ),
The refractive index of the second member for the second polarized light of wavelength λ is Ne (λ)
When expressed by
The first equation (No (λ) −N (λ)) · h / λ
Second formula (Ne (λ) −N (λ)) · h / λ
The absolute value of the difference between the values is 3 or more and 10 or less with respect to the light of the reference wavelength,
The predetermined range is a range corresponding to blue light to red light,
The reference wavelength is approximately equal to the center wavelength of green light,
The second value of the expression to blue light, green light and a second polarized light having substantially the same three wavelengths with the center wavelength of the red light, within a difference of less than 0.2, is approximated to three different integers mutually polarization separator, characterized in that is. A first member on which a blazed diffraction grating is formed; and a second member made of a birefringent material and in close contact with the diffraction grating surface of the first member, and transmitting light having a wavelength in a predetermined range. In the polarization separator that separates the first polarized light and the second polarized light whose polarization planes are perpendicular to each other,
The polarization plane of the first polarization is parallel or perpendicular to the arrangement direction of the grating of the blazed diffraction grating, and the polarization plane of the second polarization is relative to the polarization plane of the first polarization. Vertical,
The height of the blazed diffraction grating is h,
The refractive index of the first member for light of wavelength λ is N (λ),
The refractive index of the second member for the first polarized light with the wavelength λ is No (λ),
The refractive index of the second member for the second polarized light of wavelength λ is Ne (λ)
When expressed by
The first equation (No (λ) −N (λ)) · h / λ
Second formula (Ne (λ) −N (λ)) · h / λ
The absolute value of the difference between the values is 3 or more and 10 or less with respect to the light of the reference wavelength,
The predetermined range is a range corresponding to blue light to red light,
The reference wavelength is approximately equal to the center wavelength of green light,
The value of the first equation for the first polarization of three wavelengths approximately equal to the center wavelengths of blue light, green light and red light is approximated by three different integers within a range where the difference is less than 0.2. polarization separator, characterized in that is. A projection-type image display device that separates polarized light from a light source and uses the separated polarized light for image projection,
A projection-type image display device comprising the polarization separator according to any one of claims 1 to 4 for polarization separation of light from a light source.

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