JP2009237147A - Wavelength filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength filter equivalent to a multistage-structural filter with a steep transmission spectrum exhibiting a narrow band characteristic, while reducing the number of part items and preventing a device from getting long and large. <P>SOLUTION: This wavelength filter 31 includes a phaser 32 having a fixed optical thickness, and polarizers 35-38 and total-reflection mirrors 39-41 arranged respectively in an incident position 33i, an outgoing position 34o, reflection positions 33r1-33r4, 34r1-34r4 of the first and second main faces 33, 34 of the phaser. An incident light L1 is transmitted through an inside of the phaser, while reflected multiply at a fixed angle θ as to a normal direction of the main faces by the phaser and the total-reflection mirrors, in the reflection positions, from the incident position to the outgoing position, and outgoes. A phase difference between the two polarizers adjacent along an optical path of a transmission light L2 is set to π+2π×n (n:0-2). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wavelength filter for controlling or variably controlling the wavelength of transmitted light at a specific value and / or range.

  Conventionally, various band-pass filters are used to transmit light in a desired wavelength region. For example, a rio filter is known as a bandpass filter that transmits only narrow-band light using a birefringent plate (see, for example, Patent Documents 1 to 3). FIG. 17 shows a basic configuration of the Rio filter. As shown in the figure, the Rio filter 1 includes birefringent plates 3a to 3c between polarizers 2a to 2d having parallel transmission axes, and crystal optical axes 3a1 to 3c1 are transmission axes 2a1 of the polarizers. Arranged at 45 ° with 2d1. As the birefringent plates 3a to 3c, uniaxial crystals such as calcite and quartz are used, and the thickness di is 2i-1d (i = 1 to 3). In Patent Document 1, a rio filter is stacked on the surface of a liquid crystal display panel in order to increase the color purity of the three primary colors of RGB in a liquid crystal display panel having a reflecting mirror on the back. The plastic film constituting the rio filter determines its optical phase difference so that the peak of the transmission spectrum of light reflected from the back side of the liquid crystal display panel corresponds to RGB.

  The rio filter has its transmission spectrum fixed at a specific wavelength by the birefringent plate used. Therefore, a wavelength tunable optical bandpass filter in which a liquid crystal cell is sandwiched between two polarizers instead of a birefringent plate is known (see, for example, Patent Documents 2 and 3). The configuration of this bandpass filter is shown in FIG. In the figure, the band pass filter 11 changes the transmission spectrum wavelength by appropriately setting the voltage applied to the liquid crystal cells 13a to 13c sandwiched between the polarizers 12a to 12d. In particular, the band-pass filter of FIG. 18 is a so-called parallel Nicol liquid crystal cell 13a between so-called crossed Nicols polarizers 12a and 12b arranged with transmission axes 12a1 and 12b1 orthogonal to each other and transmission axes 12b1 to 12d1 arranged in parallel. By combining the two liquid crystal cells 13b and 13c sandwiched between the polarizers 12b to 12d, one of the two monochromatic lights remaining in the visible region is removed.

  Furthermore, a wavelength tunable filter having a configuration similar to that of FIG. 18 in which a composite layer composed of a liquid crystal cell and a retardation film is sandwiched between polarizers is known (see, for example, Patent Document 4). The configuration of this wavelength tunable filter is shown in FIG. In the figure, the wavelength tunable filter 21 is configured such that retardation films 24a to 24c are overlapped on liquid crystal cells 23a to 23c sandwiched between polarizers 22a to 22d, respectively. This retardation film suppresses the cell thickness of the liquid crystal cell to the necessary minimum, supplements the decrease in retardation value thereby, and generates a transmittance peak with a narrow half-value width while avoiding a decrease in the response of the liquid crystal. Also, by setting the cell thickness of the liquid crystal cell to d, 2d, and 1.5d in the order of transmission, the same control voltage is applied to all the liquid crystal cells by sharing one voltage application device, and the wavelength of the transmission spectrum is adjusted. be able to. Similarly, a tunable liquid crystal filter is known in which a liquid crystal cell and a retardation plate made of a birefringent film are disposed between two polarizers (see, for example, Patent Document 5). This wavelength tunable liquid crystal filter combines the birefringence wavelength dispersion of the liquid crystal and the birefringent film for the half width, and adjusts so that the inclination of retardation with respect to the wavelength is constant in the vicinity of showing the maximum value of transmittance. In the visible region, the half width is made constant and the wavelength is made variable.

Japanese Patent No. 3000669 Japanese Patent No. 3102012 JP 2000-267127 A JP 2005-115208 A JP 2006-317645 A

  However, the Rio filter and the above-described conventional wavelength tunable filter have two polarizers and a phase shifter such as a birefringent plate or a liquid crystal cell sandwiched between them as one block, and are arranged in multiple stages along the optical path. Although the transmission spectrum is steeper and narrow band transmission characteristics can be obtained, each component is arranged in series along the optical axis, which increases the number of parts and makes the entire filter longer and larger. There is.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and the object thereof is to reduce the number of parts as much as possible and suppress the increase in the length and size of the entire apparatus, and a multistage rio filter. It is to realize a wavelength filter capable of exhibiting a narrow band characteristic with a sharp transmission spectrum.

  According to the present invention, in order to achieve the above object, the optical surface has a certain optical thickness between the first main surface and the second main surface, and the incident position of the light on any of the main surfaces. Light that includes a phaser provided with an exit position and a plurality of reflection positions, and a plurality of polarizers provided at the incident position, the exit position, or the plurality of reflection positions of the main surface, and is incident on the phaser from the entrance position However, there is provided a wavelength filter in which the inside of the phase shifter is subjected to multiple reflection at an angle with respect to the normal direction of the main surface at each reflection position and is emitted from the emission position.

  The phase difference between two polarizers adjacent to each other along the optical path of light that passes through the phase polarizer while being subjected to multiple reflection is determined by the optical path length between the two polarizers, and the transmission spectrum corresponds to the phase difference. Therefore, the transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained. Furthermore, even if the number of polarizers provided on the main surface of the phaser is increased to 3 or more so that a configuration equivalent to a multistage rio filter can be obtained, only one common phaser is required. The number of parts can be reduced, and the length and size of the entire apparatus can be suppressed. In particular, since the number of parts is significantly reduced as compared with the prior art, it is extremely advantageous in terms of having less influence on the environment in the manufacturing process and used disposal.

  In one embodiment, the wavelength filter has n (n: integer greater than or equal to 2) polarizers at an incident position, an output position, or a reflection position of the main surface of the phase shifter, and is incident from the incident position to be a phase shifter The phase difference Γi between two polarizers adjacent to each other along the optical path of light passing through the inside is Γi = π + 2π × (i−1) with respect to the wavelength of light passing through the optical path (where i = 1 By satisfying the relationship of ~ n), since it is always an odd multiple of π, transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained.

  In another embodiment, the wavelength filter has n (n: integer greater than or equal to 2) polarizers at the incident position, emission position, or reflection position of the principal surface of the phase shifter, and is incident from the incident position to be the phase shifter. The phase difference Γi between two polarizers adjacent to each other along the optical path of light passing through the inside is Γi = 2i−1 × 2π with respect to the wavelength of the light passing through the optical path (where i = 1 to n ) Is always always an integer multiple of 2π, so that transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained.

  In still another embodiment, the wavelength filter has n (n: integer greater than or equal to 2) polarizers at the incident position, emission position, or reflection position of the main surface of the phase shifter, and enters the phase from the incident position. By arranging two adjacent polarizers in a parallel Nicol or crossed Nicol relationship along the optical path of light transmitted through the optical element, transmission characteristics as a bandpass filter similar to a conventional Rio filter can be obtained. .

  In one embodiment, the transmission band can be fixed to a specific wavelength or wavelength range by using a phase retarder of the wavelength filter. In another embodiment, the phase band of the wavelength filter is a variable phase shifter, so that the transmission band can be changed to a desired wavelength or wavelength range.

  In one embodiment, when the polarizer provided on the principal surface of the phase filter of the wavelength filter is a wire grid polarizer, light incident on the polarizer can be selectively reflected according to the polarization direction. There is no need to add a separate reflecting means when provided at the position, the number of components can be reduced, and high transmittance can be obtained for both p-polarized light and s-polarized light, so that high light utilization efficiency can be obtained. .

  In another embodiment, when the polarizer provided on the main surface of the wavelength filter phase shifter is an absorptive polarizing plate, it is necessary to add a separate reflecting means when the polarizer is provided at the reflection position. There is no possibility of causing stray light due to reflection like a grid polarizer, and therefore there is no possibility of degrading the characteristics of the wavelength filter.

Hereinafter, preferred embodiments of a wavelength filter according to the present invention will be described in detail with reference to the accompanying drawings. In each drawing, similar components are denoted by the same or similar reference numerals.
FIG. 1 schematically shows the configuration of a first embodiment of a wavelength filter according to the present invention. The wavelength filter 31 of this embodiment includes a phase shifter 32 having a constant optical thickness and a sufficient length for the thickness. On the first main surface 33 of the phaser, an incident position 33i of light to the phaser is set near the left end in the figure, and on the second main surface 34, the light emission position near the right end in the figure. 34o is set. Further, four reflection positions 33r1 to 33r4 are set on the first main surface from the incident position 33i to the emission side, and four reflection positions 34r1 to 34r1 are set on the second main surface from the incident side to the emission position 34o. 34r4 is set.

  In the phaser 32, a polarizer 35 is disposed at an incident position 33i on the first main surface, and a polarizer 36 is disposed at an emission position 34o on the second main surface. Further, the phaser 32 is provided with polarizers 37 and 38 at the reflection position 34r1 on the second main surface and the reflection position 33r2 on the first main surface, respectively, and the remaining of the main surfaces. Total reflection mirrors 39 to 41 are provided at the reflection positions 33r1, 33r3, 33r4, and 34r2 to 34r4, respectively. The total reflection mirror is formed, for example, by attaching a metal film such as Al, Ag, Au or the like to the surface of the phase plate by a method such as vapor deposition. Further, the total reflection mirror is formed by laminating a dielectric multilayer film so as to selectively reflect only a desired linearly polarized component, but not to reflect other linearly polarized components, thereby further reducing the loss due to reflection. A reduced reflection film can be obtained.

  In an embodiment, the phase shifter 32 is composed of a birefringent plate 42 such as a crystal whose transmission spectrum is fixed to a specific wavelength, as shown in FIG. In another embodiment, the phase shifter 32 includes a liquid crystal cell 43 having a liquid crystal layer 43a sandwiched between two transparent substrates 43b, as shown in FIG. In this case, the wavelength of the transmission spectrum of the wavelength filter 31 can be made variable by controlling the voltage applied to the liquid crystal cell 43.

  In this embodiment, each polarizer is composed of a wire grid polarizer in which fine metal wires are periodically arranged on the surface of a transparent substrate in a lattice pattern with a constant period shorter than the transmission wavelength. The wire grid polarizer has a characteristic of reflecting light having a vibration component perpendicular to the periodic direction of the grating and transmitting light having a vibration component parallel to the grating. The polarizers 35 and 37 at the incident position and the reflection position 34r1 are oriented so that the periodic direction of the grating is perpendicular to the paper surface, as indicated by small circles in the figure. As shown by the short arrows in the drawing, the polarizers 36 and 38 at the emission position and the reflection position 33r2 are oriented so that the periodic direction of the grating is parallel to the paper surface.

  Incident light L1 to the wavelength filter 31 passes through the phase shifter 32 from the incident position 33i to the output position 34o while being reflected by the polarizer and the total reflection mirror at each reflection position. In this embodiment, by arranging the periodic direction of the grating of the wire grid polarizer as described above, two polarizers 35 and 37 and 38 and 36 adjacent along the optical path of the transmitted light L2 are respectively The polarizers 37 and 38 are arranged in a crossed Nicols relationship in which the transmission axes are orthogonal to each other. The phase shifter 32 is configured to rotate the polarization plane by 90 ° for a desired transmission wavelength when the transmitted light L2 is transmitted from one main surface to the other main surface.

  The incident light L1 is incident at an angle with respect to the normal direction N of the principal surface of the phase shifter 32 so that the transmitted light L2 is not totally reflected by the polarizer 36 when the transmitted light L2 is finally emitted from the emission position 34o. . In the incident light L 1, the s-polarized component is reflected by the polarizer 35, and the p-polarized component is transmitted through the polarizer 35 and enters the phase shifter 32. The transmitted light L2 is converted from p-polarized light to s-polarized light when passing through the phase shifter 32, and reflected by the polarizer 37 at the reflection position 34r1 with an angle θ with respect to the normal direction N. Further, the transmitted light L2 is alternately reflected at the same angle θ with respect to the normal direction N by the polarizer or the total reflection mirror at the reflection positions 33r1 to 33r4 and the reflection positions 34r2 to 34r4 of the first and second main surfaces. And transmitted through the phase shifter 32. At that time, each time the phase shifter 32 is transmitted from one main surface to the other main surface, the transmitted light L2 is converted from p-polarized light to s-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 41 at the reflection position 33r4 is converted from p-polarized light to s-polarized light when passing through the phase shifter 32, and is emitted from the emission position 34o.

  In this embodiment, the phase shifter 32 is configured so that the phase difference is 180 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. Then, the phase difference between the two adjacent polarizers is sequentially π + 2π × n, (n: 0 to 2) along the optical path of the transmitted light L2, that is, 180 °, 540 °, and 900 °. Each of the polarizers is disposed. The wavelength filter 31 thus has a transmission characteristic as a bandpass filter similar to a conventional rio filter because the phase difference between two adjacent polarizers is always an odd multiple of π. Furthermore, the phase shifter 32 is used in common between two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one phase shifter 32 can be used. Overall lengthening and enlargement can be suppressed.

  In the embodiment of FIG. 1, the case where the phase shifter 32 is formed of a Y-cut quartz plate will be described. The direction of the p-polarized light transmitted through the polarizer 35 and incident on the phaser 32 makes an angle of 135 ° with respect to the optical axis of the phaser (indicated by a double-lined arrow in the figure). Similarly, the p-polarized light that is transmitted while being repeatedly reflected inside the phaser makes an angle of 135 ° with the optical axis of the phaser. The direction of the s-polarized light reflected by the polarizer 37 makes an angle of 45 ° with respect to the optical axis of the phase shifter. Similarly, the s-polarized light that is transmitted while being repeatedly reflected inside the phaser makes an angle of 45 ° with respect to the optical axis of the phaser.

  Therefore, the transmission characteristic between the polarizer 35 and the polarizer 37 adjacent to each other first has a peak at a wavelength that is an integral multiple of the specific wavelength. Next, the transmission characteristics between the adjacent polarizers 37 and 38 have a peak at a wavelength that is an integral multiple of ½ wavelength of the specific wavelength. Finally, the transmission characteristics between the adjacent polarizers 38 and 36 have a peak at a wavelength that is an integral multiple of the specific wavelength. The peaks of the transmission spectra between the adjacent polarizers all overlap at a wavelength that is an integral multiple of the specific wavelength. As a result, the wavelength filter 31 exhibits a transmission characteristic that provides a sharp peak at an integral multiple of the specific wavelength.

  FIG. 3 schematically shows a configuration of a modification of the first embodiment. The wavelength filter 31 ′ of this embodiment is different from that of the first embodiment in that the wire grid polarizers of the polarizers 35 ′ to 38 ′ are arranged with the periodic direction of the grating opposite to that in FIG. 1. Different. That is, in the wire grid polarizers of the polarizers 35 'and 37' at the incident position 33i and the reflection position 34r1, the periodic direction of the grating is oriented in the vertical direction with respect to the paper surface as indicated by the short arrows in the figure. The polarizers 36 'and 38' at the emission position 34o and the reflection position 33r2 are oriented such that the periodic direction of the grating is parallel to the paper surface, as indicated by small circles in the figure. Other configurations are the same as those of the wavelength filter 31 of FIG.

  In the incident light L 1, the p-polarized component is reflected by the polarizer 35 ′, and the s-polarized component is transmitted through the polarizer 35 ′ and enters the phaser 32. The transmitted light L2 is converted from s-polarized light to p-polarized light when passing through the phase shifter 32, and is reflected by the polarizer 37 'at the reflection position 34r1. Further, the transmitted light L2 is alternately reflected by the polarizer or the total reflection mirror at the reflection positions 33r1 to 33r4 and the reflection positions 34r2 to 34r4 of the first and second main surfaces and passes through the phase shifter 32. At that time, each time the phase shifter 32 is transmitted from one main surface to the other main surface, the transmitted light L2 is converted from p-polarized light to s-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 41 at the reflection position 33r4 is converted from s-polarized light to p-polarized light when passing through the phase shifter 32, and is emitted from the emission position 34o.

  FIG. 4 schematically shows the configuration of another modification of the first embodiment. In the wavelength filter 31 ″ of this embodiment, the emission position 34o in FIG. 1 is changed to the reflection position 34r5, and the total reflection mirror 41 ′ on the first main surface 33 is made shorter than that in FIG. The wire grid polarizer that forms the exit position 33o by opening the vicinity of the right end of the surface and constitutes the polarizer 36 'at the reflection position 34r5 has the periodic direction of the grating perpendicular to the paper surface as indicated by a short arrow in the figure. It differs from the first embodiment in that it is arranged in the direction. Other configurations are the same as those of the wavelength filter 31 of FIG.

  In the incident light L1, the p-polarized component passes through the polarizer 35 and enters the phase shifter 32, and is reflected by the reflection positions 33r1 to 33r4 and the reflection positions 34r1 to 34r4 alternately and passes through the phase shifter 32. Is the same as in the first embodiment. In this embodiment, after the transmitted light L2 reflected by the total reflection mirror 41 at the reflection position 33r4 is transmitted through the phase shifter 32, p-polarized light is converted into s-polarized light, and then at the reflection position 34r5 by the polarizer 36 '. The light is reflected, passes through the phase shifter 32, and is emitted from the emission position 33 o of the first main surface 33.

  FIG. 5 schematically shows the configuration of a second embodiment of the wavelength filter according to the present invention. The wavelength filter 51 of this embodiment includes a phase shifter 52 having a constant optical thickness thinner than that of the first embodiment and a sufficient length with respect to the thickness. The phase shifter 52 is configured such that the phase difference is 90 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. Therefore, when the transmitted light L2 reciprocates once between the first and second main surfaces of the phase shifter 52, the phase difference becomes 180 ° as in the first embodiment.

  On the first main surface 53 of the phaser 52, a light incident position 53i is set near the left end in the figure, and a light emission position 53o is set near the right end in the figure. Further, eight reflection positions 53r1 to 53r8 are set on the first main surface between the incident position and the emission position. On the second main surface 54, nine reflection positions 54r1 to 54r9 are set from the incident side to the emission side.

  In the phase shifter 52, a common polarizer 55 is disposed at the incident position 53i and the first reflection position 53r1 on the first main surface, and a polarizer 56 is disposed at the emission position 53o. Further, a polarizer 57 is disposed at the reflection position 53r4 on the first main surface of the phaser 52, and total reflection mirrors 58a and 58b are provided at the remaining reflection positions 53r1 to 53r3 and 53r5 to 53r8. A total reflection mirror 59 is provided on substantially the entire surface of the second main surface of the phaser 52 so as to include all the reflection positions 54r1 to 54r9.

  Also in this embodiment, each of the polarizers is a wire grid polarizer. As shown by a small circle in the figure, the polarizer 55 at the incident position has the periodic direction of the grating oriented in a plane direction with respect to the paper surface. The polarizers 56 and 57 at the emission position and the reflection position 53r4 are oriented such that the periodic direction of the grating is perpendicular to the paper surface, as indicated by a short arrow in the figure.

  Similarly, the incident light L1 to the wavelength filter 51 is transmitted through the phase shifter 52 from the incident position 53i to the emission position 53o while being multiple-reflected by the polarizer and the total reflection mirror at each reflection position. Since the polarizer 55 is common between the incident position 53i and the reflection position 53r1, the two polarizers sandwiching the phase shifter 52 have a parallel Nicols relationship. Since the periodic direction of the grating of the wire grid polarizer is oriented as described above, the polarizers 55 and 57 adjacent along the optical path of the transmitted light L2 are arranged in a crossed Nicols relationship, Are arranged in a parallel Nicol relationship.

  In the incident light L 1, the s-polarized component is reflected by the polarizer 55, and the p-polarized component is transmitted through the polarizer 55 and enters the phaser 52. When the transmitted light L2 is transmitted through the phase shifter 52, the linearly polarized light is rotated by 90 ° and converted into circularly polarized light as shown by a small ellipse in the figure. Reflected with θ. When the light is transmitted through the phase shifter 52 and reflected at the reflection position 53r2, it is further rotated by 90 ° to become s-polarized linearly polarized light. Further, the transmitted light L2 is alternately reflected at the same angle θ with respect to the normal direction N by the polarizer or the total reflection mirror at the reflection positions 53r2 to 53r8 and the reflection positions 54r2 to 54r9 of the first and second main surfaces. Each time the light passes between the first main surface and the second main surface, the light is transmitted through the phase shifter 52 while rotating the polarized light by 90 °. Finally, the transmitted light L2 reflected by the total reflection mirror 59 at the reflection position 54r9 is transmitted from the phase shifter 52 to be converted from circularly polarized light to s-polarized light, and transmitted from the output position 54o through the polarizer 56 to be emitted.

  Also in this embodiment, the phase difference between two adjacent polarizers is set to be π + 2π × n (n: 0 to 2) in order along the optical path of the transmitted light L2. Therefore, in the wavelength filter 51, since the phase difference between each two adjacent polarizers is always an integer multiple of π, transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained. Further, the phase shifter 52 is used in common between the two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one is required. Overall lengthening and enlargement can be suppressed.

  FIG. 6 schematically shows the configuration of a third embodiment of the wavelength filter according to the present invention. The wavelength filter 61 of this embodiment is configured such that the phase difference becomes 360 ° when the phase shifter 62 transmits the transmitted light L2 once from one main surface to the other main surface.

  The wavelength filter 61 includes a phase shifter 62 having a constant optical thickness that is thicker than that of the first embodiment and a sufficient length for the thickness. On the first main surface 63 of the phaser, an incident position 63i of light to the phaser is set near the left end in the figure, and an output position 64o of light is located near the right end of the second main surface 64 in the figure. Is set. Further, three reflection positions 63r1 to 63r3 are set on the first main surface from the incident position to the output side, and three reflection positions on the second main surface 64 from the incident side toward the output position. 64r1 to 64r3 are set.

  In the phase shifter 62, a polarizer 65 is disposed at an incident position 63i on the first main surface, and a polarizer 66 is disposed at an emission position 64o on the second main surface. A polarizer 67 common to the first two reflection positions 64r1 and 64r2 is disposed on the second main surface of the phaser 62. Further, a total reflection mirror 68 is provided on the first main surface of the phase shifter 62 so as to include all the reflection positions 63r1 to 63r3. A total reflection mirror 69 is provided at the remaining reflection position 64r3 of the second main surface.

  Also in this embodiment, each of the polarizers is a wire grid polarizer. As shown by small circles in the drawing, the polarizers 65 and 66 at the entrance position and the exit position are oriented in the plane direction with respect to the plane of the paper. The polarizer 67 at the reflection positions 64r1 and 64r2 is oriented such that the periodic direction of the grating is perpendicular to the paper surface, as indicated by the short arrows in the figure.

  Similarly, the light incident on the wavelength filter 61 passes through the phase shifter 62 from the incident position 63i to the emission position 64o while being reflected by the polarizer and the total reflection mirror at each reflection position. Since the polarizer 67 is common between the reflection positions 64r1 and 64r2, the two polarizers sandwiching the phase shifter 62 have a parallel Nicols relationship. Further, since the periodic direction of the grating of the wire grid polarizer constituting each polarizer is oriented as described above, the polarizers 65 and 67 and 67 and 66 adjacent to each other along the optical path of the transmitted light L2 are crossed. Arranged in a Nicole relationship.

  The incident light L1 is incident at an angle with respect to the normal direction N of the principal surface of the phase shifter 62 so that the transmitted light L2 is not totally reflected by the polarizer 66 when the transmitted light L2 is finally emitted from the emission position 64o. . In the incident light L 1, the s-polarized component is reflected by the polarizer 65, and the p-polarized component is transmitted through the polarizer 65 and enters the phase shifter 62. The transmitted light L2 is reflected at an angle θ with respect to the normal direction N by the polarizer 67 at the reflection position 64r1 as p-polarized light, and further at the reflection positions 63r1 to 63r3, 64r2, 64r3 of the first and second main surfaces. The light is alternately reflected at the same angle θ with respect to the normal direction N by the polarizer or the total reflection mirror, and is transmitted through the phase shifter 52. Finally, the transmitted light L2 reflected by the total reflection mirror 68 at the reflection position 63r3 is converted from p-polarized light to s-polarized light by the polarizer 66, and is emitted.

  In this embodiment, the phase difference between the two adjacent polarizers is 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2, that is, 360 °, 720 °, and 1440 °. As described above, the respective polarizers are arranged. Since the wavelength difference between the two adjacent polarizers is always an integral multiple of 2π, the wavelength filter 61 can obtain transmission characteristics as a bandpass filter similar to the conventional rio filter. Further, the phase shifter 62 is used in common between two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one is required. Overall lengthening and enlargement can be suppressed.

  FIG. 7 schematically shows the configuration of a fourth embodiment of the wavelength filter according to the present invention. The wavelength filter 71 of this embodiment is configured such that the phase difference becomes 180 ° when the phase shifter 72 transmits the transmitted light L2 from one main surface to the other main surface. Therefore, when the transmitted light L2 reciprocates once between the first and second main surfaces of the phase shifter 72, the phase difference becomes 360 ° as in the third embodiment.

  The wavelength filter 71 includes a phase shifter 72 having a constant optical thickness thinner than that of the third embodiment and a sufficient length for the thickness. On the first main surface 73 of the phaser, a light incident position 73i is set near the left end in the figure, and a light emission position 73o is set near the right end in the figure. Further, six reflection positions 73r1 to 73r6 are set on the first main surface between the incident position and the emission position. Seven reflection positions 74r1 to 74r7 are set on the second main surface 74 from the incident side to the emission side.

  In the phase shifter 72, polarizers 75 and 76 are disposed at the incident position 73i and the exit position 73o on the first main surface, and the polarizer 77 is disposed at the first reflection position 73r1. Further, on the first main surface of the phase shifter 72, a polarizer 78 is disposed at the reflection position 73r3, and total reflection mirrors 79a and 79b are provided at the remaining reflection positions 73r2, 73r4 to 73r6. A total reflection mirror 80 is provided on the substantially entire surface of the second main surface of the phase shifter 32 so as to include all the reflection positions 74r1 to 74r7.

  Also in this embodiment, each of the polarizers is a wire grid polarizer. As shown by small circles in the drawing, the polarizers 75 and 76 at the entrance position and the exit position are oriented in the plane direction with respect to the plane of the paper. In the polarizers 77 and 78 at the reflection position 73r4, as indicated by the short arrows in the figure, the periodic direction of the grating is oriented in a direction perpendicular to the paper surface.

  Similarly, the incident light L1 entering the wavelength filter 71 passes through the phase shifter 72 from the incident position 73i to the emission position 73o while being subjected to multiple reflection by the polarizer and the total reflection mirror at each reflection position. Since the periodic direction of the grating of the wire grid polarizer of each polarizer is oriented as described above, the adjacent polarizers 75 and 77, between the incident position 73i and the reflection position 73r1, and between the emission position 73o and the reflection position 73r3, And 78 and 76 are arranged in a crossed Nicols relationship, respectively. Between the reflection positions 73r1 and 73r3, the polarizers 77 and 78 are arranged in a parallel Nicols relationship.

  In the incident light L 1, the s-polarized component is reflected by the polarizer 75, and the p-polarized component is transmitted through the polarizer 75 and enters the phase shifter 72. When the transmitted light L2 passes through the phase shifter 72, the p-polarized light is converted into s-polarized light, reflected by the total reflection mirror 80 at the reflection position 74r1, and further, the reflection positions 73r1 to 73r6 of the first and second main surfaces. At the reflection positions 74r2 to 74r7, the light is alternately reflected by the polarizer or the total reflection mirror and transmitted through the phase shifter 72. Each time the transmitted light L2 passes through the phase shifter 72 from one main surface to the other main surface, p-polarized light is converted into s-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 80 at the reflection position 74r7 is converted from s-polarized light to p-polarized light when passing through the phase shifter 72, and is transmitted through the polarizer 76 and emitted.

  Also in this embodiment, the phase difference between two adjacent polarizers is 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2, that is, 360 °, 720 °, and 1440 °. As described above, the respective polarizers are arranged. In the wavelength filter 81, the phase difference between two adjacent polarizers is always an integer multiple of 2π, so that transmission characteristics as a bandpass filter similar to a conventional rio filter can be obtained.

  FIG. 8 schematically shows the configuration of a fifth embodiment of the wavelength filter according to the present invention. The wavelength filter 81 of this embodiment is configured such that the phase difference becomes 90 ° when the phase shifter 82 transmits the transmitted light L2 from one main surface to the other main surface. Accordingly, when the transmitted light L2 reciprocates twice between the first and second main surfaces, the phase difference becomes 360 °, the same as in the third embodiment.

  The wavelength filter 81 includes a phase shifter 82 having a constant optical thickness thinner than that of the third embodiment and a sufficient length for the thickness. On the first main surface 83 of the phaser, an incident position 83i to the phaser is set near the left end in the figure, and a light emission position 83o is set near the right end in the figure. Furthermore, thirteen reflection positions 83r1 to 83r13 are set on the first main surface between the incident position and the emission position. Fourteen reflection positions 84r1 to 84r14 are set on the second main surface 84 from the incident side toward the emission side.

  In the phase shifter 82, a polarizer 85 is disposed at an incident position 83i on the first main surface, and a polarizer 86 is disposed at an output position 83o. Further, on the first main surface of the phaser 82, polarizers 87 and 88 are arranged at reflection positions 83r2 and 83r6, and total reflection mirrors 89a to 89c are provided at the remaining reflection positions 83r1, 83r3 to 83r5 and 83r7 to 53r13. Is provided. A total reflection mirror 90 is provided on substantially the entire surface of the second main surface of the phase shifter 82 so as to include all the reflection positions 84r1 to 84r14.

  Also in this embodiment, each of the polarizers is a wire grid polarizer. As shown by small circles in the drawing, the polarizers 85 and 86 at the incident position and the outgoing position are oriented in the plane direction with respect to the plane of the paper. The polarizers 87 and 88 at the reflection positions 83r2 and 83r6 are oriented such that the periodic direction of the grating is perpendicular to the paper surface, as indicated by the short arrows in the figure.

Similarly, the incident light L1 entering the wavelength filter 81 passes through the phase shifter 82 from the incident position 83i to the emission position 83o while being subjected to multiple reflection by the polarizer and the total reflection mirror at each reflection position. Since the periodic direction of the grating of the wire grid polarizer of the polarizer is oriented as described above, the polarizers 85 and 87 adjacent between the incident position 83i and the reflection position 83r2 and between the emission position 83o and the reflection position 83r6, and 88 and 86 are arranged in a crossed Nicol relationship, respectively.
The polarizers 87 and 88 at the reflection positions 83r2 and 83r6 are arranged in a parallel Nicol relationship.

  In the incident light L 1, the s-polarized component is reflected by the polarizer 85, and the p-polarized component is transmitted through the polarizer 85 and enters the phaser 82. When the transmitted light L2 passes through the phase shifter 82, the linearly polarized light is rotated by 90 °, converted into circularly polarized light as shown by a small ellipse in the figure, and reflected by the total reflection mirror 90 at the reflection position 84r1. When the light passes through the phase shifter 82 and is reflected at the reflection position 83r1, it is further rotated by 90 ° to become s-polarized linearly polarized light, and the reflection positions 83r2 to 83r13, 84r2 of the first and second main surfaces. Are reflected by the polarizer or the total reflection mirror alternately and pass through the phase shifter 82. At that time, the transmitted light L2 rotates the polarized light by 90 ° every time it passes between the first main surface and the second main surface. Finally, the transmitted light L2 reflected by the total reflection mirror 90 at the reflection position 84r14 is converted from circularly polarized light to p-polarized light by transmitting through the phase shifter 82, and then transmitted through the polarizer 86 from the output position 83o and emitted. .

  Also in this embodiment, the phase difference between two adjacent polarizers is 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2, that is, 360 °, 720 °, and 1440 °. As described above, the respective polarizers are arranged. In the wavelength filter 81, the phase difference between two adjacent polarizers is always an integer multiple of 2π, so that transmission characteristics as a bandpass filter similar to a conventional rio filter can be obtained.

  In the wavelength filter of each of the above embodiments, the polarizer is composed of a wire grid polarizer. In another embodiment, an absorptive polarizer such as a polarizing film or a polarizing dichroic resin polarizing plate can be used. In this case, the absorptive polarizer has a property of transmitting or absorbing incident light according to the polarization direction thereof, and in order to reflect between the main surfaces of the phaser, a total reflection mirror is provided on the back surface thereof. There is a need.

  FIG. 9 schematically shows the configuration of a sixth embodiment of a wavelength filter according to the present invention. The wavelength filter 91 of the present embodiment uses an absorption type polarizing plate as a polarizer in place of the wire grid polarizer in the wavelength filter 31 of the first embodiment, and the same phase shifter 32 as that of the first embodiment. Is provided. On the first main surface 33 of the phaser 32, the light incident position 33i is set near the left end in the figure, and on the second main surface 34, the light output position 34o is set near the right end in the figure. Has been. Further, four reflection positions 33r1 to 33r4 are set on the first main surface from the incident position 33i to the emission side, and four reflection positions 34r1 to 34r1 on the second main surface from the incident side to the emission position 34o. 34r4 is set.

  In the phase shifter 32, a polarizer 92 is disposed at an incident position 33i on the first main surface, and a polarizer 93 is disposed at an emission position 34o on the second main surface. Further, the phaser 32 is provided with polarizers 94 and 95 at the reflection position 34r1 on the second main surface and the reflection position 33r2 on the first main surface, respectively. Transparent glass plates 96a and 96b having the same thickness as the polarizers 92 and 95 are disposed at the remaining reflection positions 33r1, 33r3, and 33r4 on the first main surface, respectively. A total reflection mirror 97 is provided on the back of these so as to cover them. Transparent glass plates 98 having the same thickness as the polarizers 93 and 94 are disposed at the remaining reflection positions 34r2 to 34r4 on the second main surface, and the transparent glass plates and the polarizers 94 are covered so as to cover the transparent glass plates and the polarizer 94. A total reflection mirror 99 is provided on the back surface. The total reflection mirror is formed, for example, by attaching a metal film such as Al, Ag, Au or the like by a method such as vapor deposition. Further, the total reflection mirror is formed by laminating a dielectric multilayer film so as to selectively reflect only a desired linearly polarized component, but not to reflect other linearly polarized components, thereby further reducing the loss due to reflection. A reduced reflection film can be obtained.

  Similar to the first embodiment, the phase shifter 32 can be constituted by a birefringent plate 42 such as a crystal whose transmission spectrum is fixed to a specific wavelength, as shown in FIG. Further, as shown in FIG. 2B, the phase shifter 32 can be composed of a liquid crystal cell 43 in which a liquid crystal layer 43a is sandwiched between two transparent substrates 43b. In this case, the wavelength of the transmission spectrum of the filter 91 can be made variable by controlling the voltage applied to the liquid crystal cell 43.

  Also in the present embodiment, each of the polarizers composed of absorption polarizers is arranged by selecting the polarization direction of the transmitted light in the same manner as the polarizer of the first embodiment. The polarizers 92 and 95 at the incident position and the reflection position 33r2 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component, as indicated by a short arrow in the drawing. The polarizers 93 and 94 at the emission position and the reflection position 34r1 are arranged so as to transmit the s-polarized component of the incident light and absorb the p-polarized component, as indicated by small circles in the figure.

  Incident light L1 to the wavelength filter 91 is transmitted through the phase shifter 32 from the incident position 33i to the emission position 34o while being reflected by the polarizer and the total reflection mirror at each reflection position. In this embodiment, since the polarizers are arranged as described above, all two adjacent polarizers are arranged in a crossed Nicol relationship in which the transmission axes are orthogonal to each other along the optical path of the transmitted light L2. ing. The phase shifter 32 is configured to rotate the polarization plane by 90 ° for a desired transmission wavelength when the transmitted light L2 is transmitted from one main surface to the other main surface.

  The incident light L1 is incident at an angle with respect to the normal direction N of the principal surface of the phase shifter 32 so that the transmitted light L2 is finally reflected from the output position 34o and is not totally reflected by the polarizer 93. . In the incident light L 1, the s-polarized component is absorbed by the polarizer 92, and the p-polarized component is transmitted through the polarizer 92 and enters the phaser 32. The transmitted light L2 is converted from p-polarized light to s-polarized light when passing through the phase shifter 32, and is reflected back and forth by the total reflection mirror 99 at the reflection position 34r1 with an angle θ with respect to the normal direction N. Further, the transmitted light L2 reciprocates through the polarizer or the transparent glass plate by total reflection mirrors 97 and 99 at the reflection positions 33r1 to 33r4 and 34r2 to 34r4 of the first and second main surfaces and is the same in the normal direction N. The light is alternately reflected at an angle θ and is transmitted through the phase shifter 32. At that time, each time the phase shifter 32 is transmitted from one main surface to the other main surface, the transmitted light L2 is converted from p-polarized light to s-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 97 at the reflection position 33r4 is converted into p-polarized light when passing through the phase shifter 32, and is transmitted through the polarizer 93 from the output position 34o and emitted. .

  Also in this embodiment, the phase shifter 32 is configured so that the phase difference is 180 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. The polarizers are arranged so that the phase difference between the two adjacent polarizers becomes π + 2π × n, (n: 0 to 2) in order along the optical path of the transmitted light L2. In the wavelength filter 91, the phase difference between each two adjacent polarizers is always an integer multiple of π, so that transmission characteristics as a bandpass filter similar to a conventional rio filter can be obtained. Furthermore, the phase shifter 32 is used in common between two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one phase shifter 32 can be used. Overall lengthening and enlargement can be suppressed.

  FIG. 10 schematically shows a configuration of a modified example of the sixth embodiment. The wavelength filter 91 ′ of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the embodiment of FIG. 3. The wavelength filter 91 ′ is different from the sixth embodiment in that the polarizers 92 ′ to 95 ′ are arranged with the polarization directions opposite to those in FIG. 9. That is, the polarizers 92 'and 95' at the incident position and the reflection position 33r2 are arranged so as to transmit the s-polarized component of the incident light and absorb the p-polarized component as shown by small circles in the figure. The polarizers 93 'and 94' at the emission position and the reflection position 34r1 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component as indicated by a short arrow in the figure. Since the other configuration is the same as that of the wavelength filter 91 of FIG. 9, detailed description thereof is omitted.

  In the incident light L 1, the p-polarized component is absorbed by the polarizer 92 ′, and the s-polarized component is transmitted through the polarizer 92 ′ and enters the phaser 32. The transmitted light L2 is converted from s-polarized light to p-polarized light when passing through the phase shifter 32, and is reflected back and forth by the total reflection mirror 99 at the reflection position 34r1. Further, the transmitted light L2 is reflected back and forth alternately by the total reflection mirrors 97 and 99 at the reflection positions 33r1 to 33r4 and 34r2 to 34r4 of the first and second main surfaces, and is reflected in the phase. The light passes through the child 32. At this time, every time the phase shifter 32 is transmitted from one main surface to the other main surface, the transmitted light L2 is converted from s-polarized light to p-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 97 at the reflection position 33r4 is converted into p-polarized light when passing through the phase shifter 32, and is transmitted through the polarizer 93 'from the output position 34o. To do.

  FIG. 11 schematically shows the configuration of another modification of the sixth embodiment. The wavelength filter 91 ″ of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the embodiment of FIG. In the wavelength filter 91 ″, the emission position 34o in FIG. 9 is changed to the reflection position 34r5, and the transparent glass substrate 96b ′ and the total reflection mirror 97 ′ on the first main surface 33 are made shorter than those in FIG. This is different from the sixth embodiment in that the exit position 33o is provided by opening the vicinity of the right end of the main surface of the first surface and the total reflection mirror 99 'is provided so as to cover the polarizer 93 at the reflection position 34r5. Since the other configuration is the same as that of the wavelength filter 91 of FIG. 9, detailed description thereof is omitted.

  In the incident light L1, the p-polarized component passes through the polarizer 35 and enters the phase shifter 32, and is reflected by the reflection positions 33r1 to 33r4 and the reflection positions 34r1 to 34r4 alternately and passes through the phase shifter 32. Is the same as in the sixth embodiment. In the present embodiment, the transmitted light L2 is reflected from the total reflection mirror 97 'at the reflection position 33r4 and converted from p-polarized light to s-polarized light when passing through the phase shifter 32, and then the polarizer 36' at the reflection position 34r5. Thus, the light travels back and forth through the polarizer 93, passes through the phase shifter 32, and exits from the exit position 33 o of the first main surface 33.

  FIG. 12 schematically shows the configuration of a seventh embodiment of the wavelength filter according to the present invention. The wavelength filter 101 of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the second embodiment of FIG. The wavelength filter 101 includes the same phase shifter 52 as in the second embodiment, and is configured such that the phase difference is 90 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. Therefore, when the transmitted light L2 reciprocates once between the first and second main surfaces of the phase shifter 52, the phase difference becomes 180 °, which is the same as in the second embodiment.

  On the first main surface 53 of the phaser 52, a light incident position 53i is set near the left end in the figure, and a light emission position 53o is set near the right end in the figure. Further, eight reflection positions 53r1 to 53r8 are set on the first main surface between the incident position and the emission position. On the second main surface 54, nine reflection positions 54r1 to 54r9 are set from the incident side to the emission side.

  In the phase shifter 52, polarizers 102 and 103 are arranged at an incident position 53i and an emission position 53o on the first main surface, respectively. Further, polarizers 104 and 105 are arranged at reflection positions 53r1 and 53r4 on the first main surface, respectively. Transparent glass plates 106a and 106b having the same thickness as the polarizers 104 and 105 are disposed at the remaining reflection positions 53r2, 53r3 and 53r5 to 53r8 of the first main surface, respectively. , 105 are provided with total reflection mirrors 107 on their back surfaces. On the second main surface, a transparent glass plate 108 and a total reflection mirror 109 are provided on substantially the entire surface so as to include all the reflection positions 54r1 to 54r9. The transparent glass plate 108 can be omitted and the total reflection mirror 109 can be formed directly on the second main surface.

  Similarly, the incident light L1 entering the wavelength filter 101 passes through the phase shifter 52 from the incident position 53i to the emission position 53o while being multiple-reflected by the total reflection mirror at each reflection position. The polarizers 102 and 104 at the incident position and the reflection position 53r4 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component, as indicated by a short arrow in the figure. The polarizers 103 and 105 at the emission position and the reflection position 53r2 are arranged so as to transmit the s-polarized component of the incident light and absorb the p-polarized component as shown by small circles in the figure. Accordingly, the two polarizers adjacent to each other along the optical path of the transmitted light L2 are in a crossed Nicols relationship.

  In the incident light L 1, the p-polarized component passes through the polarizer 102 and enters the phase shifter 52. When the transmitted light L2 is transmitted through the phase shifter 52, the linearly polarized light is rotated by 90 °, converted into circularly polarized light as indicated by a small ellipse in the figure, reflected by the total reflection mirror 109 at the reflection position 54r1, and then the phase shifter 52. Then, it is further rotated by 90 ° to be s-polarized linearly polarized light when reflected at the reflection position 53r2. Further, the transmitted light L2 is alternately reflected by the total reflection mirrors at the reflection positions 53r2 to 102r8 and 54r2 to 54r9 of the first and second main surfaces, and between the first main surface and the second main surface. Is transmitted through the phase shifter 52 while rotating the polarized light by 90 ° each time the light passes through the phase shifter. Finally, the transmitted light L2 reflected by the total reflection mirror 109 at the reflection position 54r9 is transmitted from the phase shifter 52 to be converted from circularly polarized light to s-polarized light, and is transmitted through the polarizer 103 from the emission position 53o to be emitted.

  Also in this embodiment, since the phase difference between two adjacent polarizers is set to be π + 2π × n, (n: 0 to 2) in order along the optical path of the transmitted light L2, the wavelength filter In 101, the phase difference between each two adjacent polarizers is always an odd multiple of π, and transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained. Further, since the phase shifter 52 is used in common between two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one phase shifter 52 is required, the number of parts can be reduced and the apparatus can be reduced. Overall lengthening and enlargement can be suppressed.

  FIG. 13 schematically shows the configuration of an eighth embodiment of the wavelength filter according to the present invention. The wavelength filter 111 of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the third embodiment of FIG. The wavelength filter 111 includes the same phase shifter 62 as in the third embodiment, and is configured so that the phase difference is 360 ° when the transmitted light L2 is transmitted once from one main surface to the other main surface. .

  On the first main surface 63 of the phase shifter 62, a light incident position 63i is set near the left end in the drawing, and a light emission position 64o is set near the right end of the second main surface 64 in the drawing. Is set. Further, three reflection positions 63r1 to 63r3 are set on the first main surface from the incident position to the output side, and three reflection positions on the second main surface 64 from the incident side toward the output position. 64r1 to 64r3 are set.

  In the phase shifter 62, a polarizer 112 is disposed at an incident position 63i on the first main surface, and a polarizer 113 is disposed at an emission position 64o on the second main surface. A polarizer 114 common to the first two reflection positions 64r1 and 64r2 is disposed on the second main surface. Further, a transparent glass plate 115 and a total reflection mirror 116 are provided on the first main surface of the phase shifter 62 so as to include all the reflection positions 63r1 to 63r3. At the remaining reflection position 64r3 of the second main surface, a transparent glass plate 117 having the same thickness as the polarizer 114 is provided, and a total reflection mirror 118 is formed so as to cover them.

  The light that has entered the wavelength filter 111 passes through the phase shifter 62 from the incident position 63i to the emission position 64o while being subjected to multiple reflection by the total reflection mirror at each reflection position. In this embodiment, all the polarizers 112 to 114 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component, as indicated by the short arrows in the figure. Accordingly, the polarizers 112 and 114, and 114 and 113 adjacent along the optical path of the transmitted light L2 are in a parallel Nicols relationship with the phase shifter 62 interposed therebetween.

  In the incident light L 1, the p-polarized component passes through the polarizer 112 and enters the phase shifter 62. The transmitted light L2 passes through the phase shifter 62 while being p-polarized light, and is reflected back and forth through the polarizer 114 by the total reflection mirror 118 at the reflection position 64r1. Further, the transmitted light L2 is alternately reflected by total reflection mirrors 116 and 118 at the reflection positions 63r1 to 63r3, 64r2 and 64r3 of the first and second main surfaces, and reciprocates and phased through the polarizer or the transparent glass plate. The light passes through the child 62. Finally, the transmitted light L2 reflected by the total reflection mirror 116 at the reflection position 63r3 is transmitted through the polarizer 113 and emitted.

  In this embodiment, the polarizers are arranged so that the phase difference between the two adjacent polarizers becomes 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2. Yes. Since the wavelength filter 111 thus always has a phase difference between two adjacent polarizers that is an integral multiple of 2π, transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained. Further, since the phase shifter 62 is used in common between two adjacent polarizers regardless of the number of polarizers provided on the main surface, and only one phase shifter 62 is required, the number of components can be reduced and the device can be reduced. Overall lengthening and enlargement can be suppressed.

  FIG. 14 schematically shows the configuration of a ninth embodiment of a wavelength filter according to the present invention. The wavelength filter 121 of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the fourth embodiment of FIG. The wavelength filter 121 includes the same phase shifter 72 as in the fourth embodiment, and is configured such that the phase difference becomes 180 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. Therefore, when the transmitted light L2 reciprocates once between the first and second main surfaces of the phase shifter 72, the phase difference becomes 360 ° as in the eighth embodiment.

  On the first main surface 73 of the phaser 72, a light incident position 73i is set near the left end in the figure, and a light emission position 73o is set near the right end in the figure. Furthermore, six reflection positions 73r1 to 73r6 are set between the incident position and the emission position on the first main surface. Seven reflection positions 74r1 to 74r7 are set on the second main surface 74 from the incident side to the emission side.

  In the phase shifter 72, the common polarizer 122 is disposed at the incident position 73i and the first reflection position 73r1 on the first main surface, and the polarizer 123 is disposed at the emission position 73o. Further, a polarizer 124 is disposed at the reflection position 73r3 on the first main surface, and transparent glass plates 125a and 125b having the same thickness as the polarizers 122 and 124 are provided at the remaining reflection positions 73r2 and 73r4 to 73r6. The total reflection mirror 126 is provided so as to cover the transparent glass plate and the polarizer 124 and the portion of the polarizer 122 at the reflection position 73r1. On the second main surface, a transparent glass plate 127 and a total reflection mirror 128 are provided on the entire surface so as to include all the reflection positions 74r1 to 74r7. It is also possible to omit the transparent glass plate 127 and form the total reflection mirror 128 directly on the second main surface.

  The light incident on the wavelength filter 121 passes through the phase shifter 72 from the incident position 73i to the emission position 73o while being multiple-reflected by the total reflection mirror at each reflection position. In this embodiment, all the polarizers 122 to 124 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component, as indicated by the short arrows in the figure. Therefore, the polarizers 122 and 124, and 124 and 123 adjacent along the optical path of the transmitted light L2 are in a parallel Nicols relationship with the phase shifter 72 interposed therebetween.

  In the incident light L 1, the p-polarized component passes through the polarizer 122 and enters the phase shifter 72. The transmitted light L2 is transmitted through the phase shifter 72, p-polarized light is converted into s-polarized light, and reflected by the total reflection mirror 128 at the reflection position 74r1. Further, the transmitted light L2 is alternately reflected by the total reflection mirrors 126 and 128 at the reflection positions 73r1 to 73r6 and 74r2 to 74r7 of the first and second main surfaces, and travels back and forth through the polarizer or the transparent glass plate. The light passes through the child 72. Each time the transmitted light L2 passes through the phase shifter 72 from one main surface to the other main surface, p-polarized light is converted into s-polarized light or vice versa. Finally, the transmitted light L2 reflected by the total reflection mirror 128 at the reflection position 74r7 is converted from s-polarized light to p-polarized light when passing through the phase shifter 72, and is transmitted through the polarizer 123 and emitted.

  Also in this embodiment, the polarizers are arranged so that the phase difference between two adjacent polarizers becomes 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2. Yes. Since the wavelength difference between the two adjacent polarizers is always an integer multiple of 2π, the wavelength filter 121 can obtain transmission characteristics as a bandpass filter similar to a conventional rio filter.

  FIG. 15 schematically shows the structure of a tenth embodiment of the wavelength filter according to the present invention. The wavelength filter 131 of this embodiment uses an absorptive polarizing plate as a polarizer in place of the wire grid polarizer in the fifth embodiment of FIG. The wavelength filter 131 includes the same phaser 82 as in the fifth embodiment, and is configured such that the phase difference becomes 90 ° when the transmitted light L2 is transmitted from one main surface to the other main surface. Therefore, when the transmitted light L2 reciprocates twice between the first and second main surfaces of the phase shifter 82, the phase difference becomes 360 °, which is the same as in the eighth embodiment.

  On the first main surface 83 of the phaser 82, an incident position 83i to the phaser is set near the left end in the figure, and a light emission position 83o is set near the right end in the figure. Furthermore, 13 reflection positions 83r1 to 83r13 are set between the incident position and the emission position on the first main surface. Fourteen reflection positions 84r1 to 84r14 are set on the second main surface 84 from the incident side toward the emission side.

  In the phaser 82, a polarizer 132 is disposed at an incident position 83i on the first main surface, and a polarizer 133 is disposed at an output position 83o. Further, polarizers 134 and 135 are disposed at reflection positions 83r2 and 83r6 on the first main surface, and transparent members having the same thickness as the polarizers 134 and 135 are disposed at the remaining reflection positions 83r1, 83r3 to 83r5 and 83r7 to 53r13. Glass plates 136 a and 136 b are arranged, and a total reflection mirror 137 is provided so as to cover these transparent glass plates and polarizers 134 and 135. On the second main surface, a transparent glass plate 1138 and a total reflection mirror 139 are provided on the entire surface so as to include all the reflection positions 84r1 to 84r14. Incidentally, the transparent glass plate 138 may be omitted, and the total reflection mirror 139 may be directly formed on the second main surface.

  The light incident on the wavelength filter 131 passes through the phase shifter 82 from the incident position 83i to the emission position 83o while being subjected to multiple reflection by the total reflection mirrors 137 and 139 at the respective reflection positions. In this embodiment, all the polarizers 132 to 135 are arranged so as to transmit the p-polarized component of the incident light and absorb the s-polarized component, as indicated by the short arrows in the figure. Accordingly, the two polarizers adjacent to each other along the optical path of the transmitted light L2 have a parallel Nicol relationship with the phase shifter 82 interposed therebetween.

  In the incident light L 1, the p-polarized component passes through the polarizer 132 and enters the phase shifter 82. The transmitted light L2 is transmitted through the phase shifter 82, the linearly polarized light is rotated by 90 °, converted into circularly polarized light as indicated by a small ellipse in the figure, and reflected by the total reflection mirror 137 at the reflection position 84r1. Then, when the light passes through the phase shifter 82 and is reflected at the reflection position 83r1, and travels back and forth through the polarizer 134 and passes through the phase shifter 82, the polarization is further rotated by 90 ° to become s-polarized linearly polarized light. The transmitted light L2 is further reflected alternately by the total reflection mirrors at the reflection positions 83r2 to 83r13 and 84r2 to 84r14 on the first and second main surfaces, and travels back and forth through the polarizer 135 or the transparent glass plate. 82 is transmitted through. At that time, the transmitted light L2 rotates the polarized light by 90 ° every time it passes between the first main surface and the second main surface. Finally, the transmitted light L2 reflected by the total reflection mirror 139 at the reflection position 84r14 is converted from circularly polarized light to p-polarized light by passing through the phase shifter 82, and is transmitted through the polarizer 133 from the output position 83o and emitted. .

  Also in this embodiment, the polarizers are arranged so that the phase difference between the two adjacent polarizers becomes 2n × 2π and (n: 0 to 2) in order along the optical path of the transmitted light L2. ing. In the wavelength filter 131, the phase difference between the two adjacent polarizers is always an integer multiple of 2π, so that transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained.

  FIG. 16 schematically shows the configuration of an eleventh embodiment of the wavelength filter according to the present invention. The wavelength filter 141 of the present embodiment includes a phase shifter 142 having a constant optical thickness and a sufficient length for the thickness. The phase shifter 142 is configured such that the phase difference is 360 ° when transmitted light is transmitted once from one main surface to the other main surface. On the first main surface 143 of the phaser, an incident position 143i to the phaser is set near the left end in the figure, and three reflection positions 143r1 to 143r3 are set to the right from the incident position. On the second main surface 144, an emission position 144o near the center in the figure and three reflection positions 144r1 to 144r3 are set. Further, in the phase shifter 142, one reflection position 142r is set on the end face 142a opposite to the incident position.

  In the phase shifter 142, a polarizer 145 is disposed at an incident position 143i on the first main surface, and a common polarizer is included so as to include an emission position 34o and reflection positions 144r1 and 144r2 on the second main surface. 146 is arranged. Further, the phase shifter 142 is provided with a transparent glass plate 147 and a total reflection mirror 148 so as to include the reflection positions 143r1 to 143r3 on the first main surface. On the second main surface, a transparent glass plate 149 having the same thickness as that of the polarizer 146 is disposed at the reflection position 144r3, and the total reflection mirrors 150 and 151 are spaced from the emission position 144o and the vicinity thereof. It is formed so as to cover the reflection positions 144r1 and 144r3 of the plate 149 and the polarizer 146. Further, a total reflection mirror 152 is provided at the reflection position 142r of the end face of the phase shifter 142.

  In this embodiment, the polarizers 143 and 146 are formed of absorption type polarizing plates. The two polarizers are arranged so as to transmit the p-polarized component of incident light and absorb the s-polarized component, as indicated by the short arrows in the figure.

  In the incident light L 1, the p-polarized component passes through the polarizer 145 and enters the phase shifter 142. The transmitted light L2 is reflected at an angle θ with respect to the normal direction N by the total reflection mirror 150 at the reflection position 144r1 while being p-polarized light, reciprocates through the polarizer 146, passes through the phase shifter 142, and passes through the first principal surface. The light is reflected by the total reflection mirror 147 at the reflection position 143r1. Further, the transmitted light L2 passes through the phase shifter 142, is reflected at the reflection position 144r2, passes back and forth through the polarizer 146, passes through the phase shifter 142, is reflected at the reflection position 143r3, reaches the phase shifter end surface 142a, and is reflected at the reflection position 142r. Is reflected inside the phase shifter 142. The transmitted light L2 reflected by the phaser end surface 142a passes through the phaser 142, is reflected by the reflection positions 144r3 and 143r2 of the respective main surfaces, passes through the phaser 142 and the polarizer 146, and exits from the emission position 144o. To do. The transmitted light L2 is converted to s-polarized light when reflected by the retarder end face 142a, and converted again to s-polarized light when reflected by the reflection position 144r3.

  In this embodiment, the polarizers are arranged so that the phase difference between two adjacent polarizers is 2π + 2π × n, (n: 0 to 2) in order along the optical path of the transmitted light L2. ing. In the wavelength filter 141, the phase difference between the two adjacent polarizers is always an integer multiple of 2π, so that transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained. Moreover, since the optical path of the transmitted light L2 is folded back at the end facet of the phaser, the length of the phaser can be shortened to about half that of the above embodiments with respect to the optical path length.

  The present invention is not limited to the above embodiments, and can be implemented with various modifications or changes within the technical scope thereof. For example, the incident position, the emission position, and the reflection position of the wavelength filter can be set at various positions other than the above embodiments. Moreover, each polarizer of each said wavelength filter can be used combining a reflection type wire grid polarizer and an absorption type polarizing plate.

1 is a cross-sectional view schematically showing a first embodiment of a wavelength filter according to the present invention. (A), (B) is sectional drawing which shows schematically the Example from which a phase element differs, respectively. Sectional drawing which shows another modification of 1st Example roughly. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the further another modification of 1st Example. Sectional drawing which shows schematically the 2nd Example of the wavelength filter by this invention. Sectional drawing which shows schematically the another modification of 2nd Example. Sectional drawing which shows schematically the further another modification of 2nd Example. Sectional drawing which shows schematically the further another modification of 2nd Example. Sectional drawing which shows schematically the further another modification of 2nd Example. Sectional drawing which shows schematically the further another modification of 2nd Example. Sectional drawing which shows schematically the further another modification of 2nd Example. The figure which shows the basic composition of a Rio filter. The block diagram of the prior art example using a liquid crystal cell. The block diagram of another prior art example using a liquid crystal cell.

Explanation of symbols

1 ... Rio filter, 2a-2d, 12a-12d, 22a-22d, 35-38, 55-57, 65-67, 75-78, 85-88, 92-95, 102-105, 112-114, 122 ˜124, 132˜135, 145, 146... Polarizer, 2a1˜2d1, 12a1˜12d11, transmission axis, 3a˜3c, birefringent plate, 3a1˜3c1, optical axis, 4 ... optical axis, 11 ... band pass filter , 13a-13c, 23a-23c, 43 ... liquid crystal cell, 21 ... tunable filter, 24a-24c ... retardation film, 31, 31 ', 31' ', 51, 61, 71, 81, 91, 101, 111 , 121, 131, 141 ... wavelength filters, 32, 52, 62, 72, 82, 142 ... phase shifters, 33, 53, 63, 73, 83, 143 ... first main surface, 33i, 53i, 63i, 73i , 8 i, 143i ... incident position, 33o, 34o, 53o, 64o, 73o, 83o, 144o ... emission position, 33r, 34r, 53r, 54r, 63r, 64r, 73r, 74r, 83r, 84r, 142r, 143r, 144r ... Reflection position, 34, 54, 64, 74, 84, 144 ... second main surface, 39 to 41, 58a, 58b, 59, 68, 69, 79a, 79b, 80, 89a to 89c, 90, 97, 99 , 107, 109, 116, 118, 126, 158, 137, 139, 148, 150 to 152, total reflection mirror, 42, fixed phase plate, 43 a, liquid crystal layer, 43 b, transparent substrate, 96 a, 96 b, 98, 106 a 106b, 108, 115, 117, 125a, 125b, 136a, 136b, 138, 147, 149... Transparent glass plates.

Claims (8)

A phaser having a constant optical thickness between the first main surface and the second main surface, and having a light incident position, an output position, and a plurality of reflection positions on the main surface; A plurality of polarizers provided at the incident position, the emission position or the plurality of reflection positions;
The light incident on the phaser from the incident position is multiple-reflected at an angle with respect to the normal direction of the main surface at the plurality of reflection positions in the phaser and is emitted from the emission position. Wavelength filter.   A phase difference Γi between two polarizers having n (n: an integer of 2 or more) polarizers adjacent to each other along the optical path of the light is determined with respect to the wavelength of the light transmitted through the optical path. 2. The wavelength filter according to claim 1, wherein a relationship of [Gamma] i = [pi] +2 [pi] * (i-1) (where i = 1 to n) is satisfied.   A phase difference Γi between two polarizers having n (n: an integer of 2 or more) polarizers adjacent to each other along the optical path of the light is determined with respect to the wavelength of the light transmitted through the optical path. 2. The wavelength filter according to claim 1, wherein a relationship of [Gamma] i = 2i-1 * 2 [pi] (where i = 1 to n) is satisfied.   It has n (n: integer of 2 or more) polarizers, and the two polarizers adjacent along the optical path of the light are arranged in a parallel Nicol or crossed Nicol relationship. The wavelength filter according to claim 1.   The wavelength filter according to claim 1, wherein the phase shifter is a fixed phase shifter.   The wavelength filter according to claim 1, wherein the phase shifter is a variable phase shifter.   The wavelength filter according to claim 1, wherein the polarizer is a wire grid polarizer.   The wavelength filter according to claim 1, wherein the polarizer is an absorption polarizing plate.

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