JP2009265199A - Wavelength variable filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength variable filter equivalent to a multistage-structured Lyot filter, in which utility efficiency of light is high, an increase in the length/size of equipment is suppressed by decreasing the number of components, sharp and narrow-band characteristics of transmitting spectrum can be demonstrated in a wide wavelength band including short wavelength band. <P>SOLUTION: The wavelength filter 31 has first and second Babinet-Soleil phase plates 32 and 33 composed of two wedge-shaped double refraction plates, respectively. The inside double refraction plates 35 and 37 of both Babinet-Soleil phase plates are laminated with an incident side polarizer 38, an inside reflection film 40 and an emission side polarizer 39 interposed therebetween, and outside polarizers 42 to 44 and 46 to 48 and outside reflection films 45 and 49 are arranged on the respective principal surfaces of outer double refraction plates 34 and 36 along the advance direction of light beam. Incident light L1 is spectroscopically branched into s-polarized light and p-polarized light by an incident side polarizer, which pass through the inside of the first and the second Babinet-Soleil phase plates, respectively, while being multiply-reflected, combine with each other by an emission side polarizer and emitted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wavelength tunable 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. 10 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. The birefringent plates 3a to 3c are made of uniaxial crystals such as calcite and quartz, and have a thickness di of 2 ^i-1 d (i = 1 to 3), that is, d, 2d, and 4d. Is done. 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 shown in FIG. 11 is a so-called parallel Nicol liquid crystal cell 13a between so-called crossed Nicols polarizers 12a and 12b arranged so that transmission axes 12a1 and 12b1 are 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 in FIG. 11 is known in which a composite layer composed of a liquid crystal cell and a retardation film is sandwiched between polarizers (see, for example, Patent Document 4). The configuration of this 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.

  Further, as a phase element that can adjust the phase difference, a Babinet Soleil compensator is known (see, for example, Patent Document 5). The Babinet Soleil compensator has a birefringent element composed of two wedge-shaped birefringent plates whose optical axes are parallel to each other, and a parallel plane plate perpendicular to the optical axis direction, and slides the wedge-shaped birefringent plates relative to each other. Thus, the phase difference can be controlled by adjusting the thickness of the birefringent element. In general, a Babinet Soleil compensator is used for measuring the gap thickness of an optical material having a birefringent layer, for example, to return elliptically polarized light to linearly polarized light or to provide a desired phase difference in reproduction of magneto-optical recording, or for a liquid crystal display device. Is used as a phase difference compensation element for eliminating the coloring of the display of the liquid crystal cell (see, for example, Patent Documents 6 to 8).

Japanese Patent No. 3000669 Japanese Patent No. 3102012 JP 2000-267127 A JP 2005-115208 A JP-A-63-113838 JP-A-3-40252 Japanese Patent Laid-Open No. 9-5040 Japanese Utility Model Publication 4-9016

  However, since the rio filter and the conventional wavelength tunable filter described above require that incident light be first polarized by the polarizing plate, half of the incident light amount is lost by being absorbed or reflected by the first polarizing plate, and the use of light. The efficiency is very low. Therefore, when the output of the light source is increased in order to increase the amount of emitted light, there is a problem that the life of the light source lamp is shortened and the cost is increased. Furthermore, since the polarization direction of the emitted light is limited by the first polarizing plate on the incident side, the degree of freedom in using the filter is low.

  Further, in the above-described conventional wavelength filter, a multistage configuration in which two polarizers and a phase shifter such as a birefringent plate or a liquid crystal cell sandwiched between them are used as one block, and this is arranged along an optical path, a transmission spectrum is obtained. While a sharper and narrow band transmission characteristic can be obtained, each component is arranged in series along the optical axis, which increases the number of components. Therefore, there is a problem that the entire filter is lengthened and enlarged. In particular, a multi-stage variable wavelength filter requires a plurality of liquid crystal cells having different specifications, which increases costs.

  Further, the liquid crystal cell has a property of absorbing light in a short wavelength range from ultraviolet to blue in addition to causing a loss in transmitted light amount due to reflection on an ITO (indium tin oxide) film or the like. Therefore, as described above, the wavelength tunable filter using the liquid crystal cell has a problem that the transmittance in a short wavelength region is significantly reduced.

  Furthermore, in order to precisely control the voltage applied to the plurality of liquid crystal cells, an independent drive control circuit is required for each liquid crystal cell, which causes a problem that the configuration and control of the entire apparatus are complicated. Moreover, the liquid crystal cell has problems such as low heat resistance and large transmitted wavefront aberration. Moreover, since the liquid crystal cell has a slow response to the applied voltage of the refractive index, it may be practically difficult to continuously change the transmission wavelength by changing the applied voltage continuously.

  In addition, the conventional wavelength filter uses an absorption polarizer such as a retardation film as the polarizer, and therefore has a large optical loss. On the other hand, reflective polarizers such as wire grid polarizers, photonic crystal polarizers, and brightness enhancement films generally have low loss and broadband optical characteristics, and are excellent in heat resistance. However, if a reflective polarizer is used in a wavelength filter having a multi-stage configuration in which conventional optical elements are arranged in series along the optical path, unnecessary reflected light is generated and stray light cannot be obtained. .

  The inventors of the present application have a high heat resistance and a short wavelength because the Babinet Soleil compensator is formed of a material having high transmittance such as quartz and adjusts the phase difference by mechanically controlling the thickness of the birefringent element. We focused on features such as high transmission efficiency and good responsiveness even in the region. In view of the above-described conventional problems, the present invention has been devised as a result of various studies on applying a Babinet Soleil compensation plate to a wavelength tunable filter.

  Accordingly, an object of the present invention is to provide a high light utilization efficiency, to reduce the number of parts, thereby suppressing an increase in the length and size of the entire apparatus, and a transmission spectrum that is steep and narrow as in a multistage rio filter. Wavelength tunable that can control the transmission wavelength more easily and with high accuracy for light in a wide wavelength range including the short wavelength range from ultraviolet to blue by using the Babinet Soleil compensator while exhibiting band characteristics To implement a filter.

  According to the present invention, in order to achieve the above object, the first and second retardation elements, the incident side polarizer, the first and second outer polarizers, the inner reflection film, the first and second An outer reflection film, and the first and second phase difference elements are each arranged in a wedge shape with a thickness decreasing from one end to the other end and opposed to each other to change the thickness of each phase difference element The first and second phase difference elements are laminated with the incident-side polarizer and the inner reflection film sandwiched between them, and the first phase difference element The first outer polarizer and the first outer reflective film are disposed on the outer principal surface of the second retardation element, and the second outer polarizer and the second outer reflective film are disposed on the outer principal surface of the second retardation element. The light incident on the phase difference element is split into reflected light and transmitted light by the incident side polarizer, and the reflected light is reflected in the first phase difference element. The first outer polarizer or the first outer reflective film and the inner reflective film are multiple-reflected and transmitted at a certain angle with respect to the normal direction of the main surface of the phase difference element, and the transmitted light is transmitted through the second phase difference element. Is provided with a second outer polarizer or a second outer reflecting film and a second outer reflecting film and an inner reflecting film so as to allow multiple reflection at a certain angle with respect to the normal direction of the main surface of the phase difference element.

  Incident light is split by the incident-side polarizer, and each of the split lights is transmitted through the first phase difference element and the second phase difference element, so that high light utilization efficiency can be obtained. Furthermore, since the same light quantity is maintained and secured even if the output of the light source is lowered, at least the amount of the improvement in the transmittance can extend the life of the light source lamp as compared with the conventional case. In the first and second retardation elements, the phase difference between the two polarizers adjacent to each other along the optical path of the light that passes through the respective internal reflections is determined by the optical path length between the two polarizers. The peak wavelength of the transmission spectrum is set corresponding to the phase difference. The retardation element can adjust the wavelength of light to be transmitted by relatively moving the two retardation plates constituting the retardation element, that is, the birefringence plate, and changing the optical thickness thereof. . Therefore, for each phase difference element, a wavelength tunable filter capable of freely changing the transmission spectrum wavelength is realized as a bandpass filter similar to the conventional rio filter.

  In addition, in the case of a configuration equivalent to a multistage rio filter, it is not necessary to increase the number of phase difference elements, and the first and second elements arranged on the outer main surfaces of the common first and second phase difference elements, respectively. Since it is only necessary to increase the number of outer polarizers, the number of parts can be significantly reduced as compared with the conventional case. Therefore, it is possible to suppress an increase in the length and size of the entire apparatus and an increase in cost. In particular, since the number of parts is significantly reduced as compared with the prior art, it is extremely advantageous in that the environmental impact of the manufacturing process and disposal after use is small.

  Furthermore, a retardation element using a birefringent plate made of quartz or the like exhibits high transmittance even in the short wavelength range from ultraviolet to blue, so that the transmission wavelength can be varied for light in a wide wavelength range including the short wavelength range. A tunable filter that can be controlled can be realized. In addition, since the phase difference element is excellent in heat resistance, the heat resistance of the wavelength tunable filter is greatly improved as compared with the conventional technique using a liquid crystal cell.

  In one embodiment, the wavelength tunable filter further includes an output-side polarizer sandwiched between the stacked first and second phase difference elements, and the second position of the light reflected by the multiple reflection inside the first phase difference element. The light that has undergone multiple reflection inside the phase difference element is combined by the output-side polarizer and emitted from the first and second phase shifters, so that emitted light with a light amount with less loss than the incident light amount can be obtained.

In another embodiment, the phase difference Γ _1i between two polarizers adjacent to each other along the optical path of light transmitted through the first phase difference element is Γ _1i = 2 with respect to the wavelength of light transmitted through the optical path. ^i-1 × 2π (where i = ₁ to n ₁ , n ₁ : an integer greater than or equal to 2), and two adjacent adjacent optical paths of light passing through the second phase difference element The phase difference Γ _2i between the polarizers is Γ _2i = 2 ⁱ⁻¹ × 2π with respect to the wavelength of light transmitted through the optical path (where i = 1 to n ₂ , n ₂ : an integer of 2 or more). By satisfying the relationship, both are always integral multiples of 2π, so that the transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained in each of the first and second phase difference elements.

  In yet another embodiment, two polarizers adjacent along the optical path inside the first phase difference element and two polarizers adjacent along the optical path inside the second phase difference element are in a parallel Nicols relationship. As a result, the transmission characteristics as a band-pass filter similar to the conventional rio filter can be obtained in each of the first and second phase difference elements.

  In one embodiment, each of the first and second retardation elements is composed of two wedge-shaped birefringent plates, and the inner birefringent plates facing each of the retardation elements are arranged between the incident side polarizer and the inner reflective film. When the two layers are integrally laminated, the transmission spectral wavelengths of both the first and second phase difference elements can be adjusted and controlled simultaneously by being driven by one actuator. Conversely, by fixing the laminated inner birefringent plates and driving the outer birefringent plates of each phase difference element individually or integrally, the transmission spectral wavelengths of the first and second phase difference elements are individually adjusted. It can also be controlled.

  In one embodiment, the first retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ1, and the second retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ2, and the wedge angle θ1 Since the wedge angle θ2 is the same, the transmission spectrum of both phase difference elements can always be adjusted and controlled at the same wavelength and in the same ratio. This is particularly advantageous when the transmitted light of both phase difference elements is synthesized and emitted.

  In another embodiment, the first retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ1, and the second retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ2, and the wedge angle θ1 and the wedge angle Since θ2 is different, the transmission spectrum of each phase difference element can be adjusted and controlled to different wavelengths at different ratios. This is particularly advantageous when the transmitted light of each phase difference element is emitted separately.

  In an embodiment, when the incident side polarizer is a wire grid polarizer, high transmittance can be obtained for both p-polarized light and s-polarized light.

  In another embodiment, when the output side polarizer is a wire grid polarizer, both the p-polarized light and the s-polarized light exhibit high transmittance, so that high light utilization efficiency can be obtained.

  Further, in an embodiment, when the outer polarizer is a wire grid polarizer, there is no need to add a separate reflecting means when reflecting light transmitted through the first and second phase shifters, and the number of components is reduced. This is advantageous.

  In another embodiment, if the outer polarizer is an absorptive polarizing plate, it is not necessary to add a separate reflecting means, but there is no risk of stray light due to reflection as in a wire grid polarizer. There is no risk of degrading the characteristics of the wavelength filter.

  In another embodiment, the phase difference plate of at least one of the first and second phase difference elements constituting the phase difference element is configured such that one surface of the parallel plate is left as it is and the opposite surface is a predetermined wedge. By being inclined and processed at the corners, the inclined surfaces are opposed to each other, and the thicker end and the thinner end are arranged in a staggered manner on the same side. The optical thickness of the retardation element can be changed by moving them relative to each other along the inclined surface. In yet another embodiment, at least one of the first and second phase difference elements constituting the phase difference element has a phase difference plate with a surface on one side of the parallel plate being left as it is. Formed by inclining at a wedge angle, the one surface is opposed to each other, and the thicker end and the thinner end are arranged alternately on the same side. .

  In one embodiment, the two retardation plates of at least one of the first and second retardation elements are arranged in parallel with each other so that the transmitted light maintains its polarization direction as it is. And can be transmitted. In another embodiment, two retardation plates of at least one of the first and second retardation elements are arranged with their crystal optical axes orthogonal to each other, so that the transmitted light has a polarization direction of 90. It can be rotated and transmitted.

  In one embodiment, at least one of the first and second phase difference elements further includes a parallel plate phase difference plate combined with at least one phase difference plate, thereby expanding the wavelength range of transmitted light. be able to.

  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.

  1A to 1C schematically show the configuration of a first embodiment of a wavelength filter according to the present invention. The wavelength filter 31 of the present embodiment includes a first Babinet Soleil phase plate 32 and a second Babinet Soleil phase plate 33 as phase difference elements each having a certain optical thickness and a sufficient length with respect to the thickness. . The first Babinet Soleil phase plate 32 includes two wedge-shaped birefringent plates 34 and 35 having the same wedge angle θ1. The second Babinet Soleil phase plate 33 includes two wedge-shaped birefringent plates 36 and 37 having the same wedge angle θ2. Each birefringent plate is made of quartz or other similar optical crystal material.

As shown in FIG. 1 (C), first Babinet Soleil phase plate 32, the upper birefringent plate 34 is made of the wedge plate 34 ₁ and the parallel plate 34 ₂ which, under the birefringent plate 35 is only wedges Consists of. The wedge plate 34 ₁ and the lower birefringence plate 35 of the upper birefringent plate, one face of the birefringent plate of a parallel plate inclined processed by polishing or the like, which remains in its inclined surface parallel to the flat plate surface opposite It is formed so as to define a predetermined wedge angle θ1 with the side surface. Similarly, the second Babinet Soleil phase plate 33, the birefringence plate 36 of the lower side is from the wedge plate 36 ₁ and the parallel plate 36 ₂ which, above the birefringent plate 37 is made of only the wedge plate. The wedge plate 36 ₁ and the upper birefringent plate 37 of the lower birefringent plate, one surface of the birefringent plate similarly parallel plate inclined processed by polishing or the like, while the inclined surface parallel to the flat plate surface It is formed so as to define a predetermined wedge angle θ2 with respect to a certain opposite surface.

  In the first and second Babinet Soleil phase plates 32 and 33, the two wedge-shaped birefringent plates are arranged so that their inclined surfaces are opposed to each other, and the thicker end portion and the thinner thickness portion are arranged. They are arranged in a staggered manner with the ends on the same side. Each of the Babinet Soleil phase plates is moved optically by moving the two birefringent plates 34, 35 and 36, 37 in the width direction of the Babinet Soleil phase plate by an actuator including a micrometer (not shown). The wavelength of transmitted light can be adjusted by changing the thickness. The birefringent plates 34, 35 and 36, 37 can be moved relative to each other while the opposed inclined surfaces are in contact with each other and slid therebetween, or the opposed inclined surfaces are separated from each other with a gap therebetween. it can. The attached drawings show a state in which the inclined surfaces facing each other of the birefringent plates are separated from each other for easy understanding.

In the first Babinet Soleil phase plate 32, the wedge plate 34 ₁ and the birefringent plate 35, into their optical axes Op 11, the orientation of Op12 45 ° is relative to the length direction of and the Babinet Soleil phase plate in the same direction Oriented. The wedge plate 34 ₁ and the parallel plate 34 _2, the optical axis Op 11, Op 13 is oriented at 45 ° orientation relative to the longitudinal direction of and each of the Babinet Soleil phase plate so as to be perpendicular to each other. In the second Babinet Soleil phase plate 33, the wedge plate 36 ₁ and the birefringent plate 37, into their optical axes Op21, the orientation of Op22 45 ° is relative to the length direction of and the Babinet Soleil phase plate in the same direction Oriented. The wedge plate 36 ₁ and the parallel plate 36 _2, the optical axis Op21, Op23 is oriented at 45 ° orientation relative to the longitudinal direction of and each of the Babinet Soleil phase plate so as to be perpendicular to each other.

  The first Babinet Soleil phase plate 32 and the second Babinet Soleil phase plate 33 are arranged between the inner principal surfaces facing each other, that is, between the inner birefringent plate 35 and the birefringent plate 37, and incident side and outgoing side polarized light. The members 38 and 39 and the inner reflection mirror 40 are stacked on top and bottom, and are joined together with an adhesive 41 at both ends. The outer principal surface of the first Babinet Soleil phase plate, that is, the vicinity of one end 32a (the left side in the figure) of the outer birefringent plate 34 is used as a light incident port, and the vicinity of the other end part 32b (the right side in the figure) is light. The light exit is used so that light travels from the left to the right in the drawing along the length direction in a direction perpendicular to the driving direction of the Babinet Soleil phase plate. An incident-side polarizer 38, an inner reflection mirror 40, and an exit-side polarizer 39 are arranged in this order along the light traveling direction.

  First outer polarizers 42 to 44 and a first outer reflective film 45 are provided on the outer principal surface of the first Babinet Soleil phase plate 32, that is, the upper surface of the outer birefringent plate 34. From the left side to the right side in the figure, the first first outer polarizers 42 and 43, the first outer reflective film 45, and the first outer polarizer 44 are arranged in this order in the light traveling direction. Is done. Second outer polarizers 46 to 48 and a second outer reflecting film 49 are provided on the outer principal surface of the second Babinet Soleil phase plate 33, that is, the lower surface of the outer birefringent plate 36. Similarly, in the drawing, from the left side to the right side, the two second outer polarizers 46 and 47, the second outer reflection film 49, and finally the second outer polarizer 48 are finally formed along the light traveling direction. Are arranged in order.

  In the present embodiment, the incident side and output side polarizers and the first and second outer polarizers are wire grid polarizers. Wire grid polarizers are arranged on a transparent substrate surface in the form of a lattice of metal thin wires periodically with a constant period shorter than the transmission wavelength, reflect the light of vibration components perpendicular to the periodic direction of the lattice, and are parallel to each other It has the characteristic of transmitting light of vibration components. In the figure, s-polarized light is linearly polarized light perpendicular to a plane (the paper surface of FIG. 1B) including light incident on the wavelength filter 31 and the normal line of the upper surface of the outer birefringent plate of the first Babinet Soleil phase plate. A black circle dot ● represents parallel linearly polarized light as p-polarized light and is represented by a short double-ended arrow in the figure. As the incident side and emission side polarizers, various known polarizers other than the wire grid polarizer can be used as long as they split the incident light so as to be transmitted or reflected depending on the polarization direction. The inner reflection film 40 and the first and second outer reflection films 45 and 49 are formed of a metal film such as Al, Ag, Au, or a dielectric multilayer film, for example.

  In this embodiment, the gratings of the first outer polarizer, the incident side and the output side polarizer are aligned with the width direction of the first Babinet Soleil phase plate 32, and the periodic direction thereof is the optical axis Op11 of the Babinet Soleil phase plate. It is oriented so as to form an angle of 45 ° with .about.Op13 and coincide with the length direction of the Babinet Soleil phase plate. The grating of the second outer polarizer is aligned with the length direction of the second Babinet Soleil phase plate 33, and the periodic direction forms an angle of 45 ° with the optical axes Op21 to Op23 of the Babinet Soleil phase plate, And it orients so that it may correspond with the width direction of the said Babinet Soleil phase plate. For example, the orientation of the grating of each polarizer is represented by a number of parallel thin vertical lines in FIGS.

  As described above, the wavelength filter 31 includes the first Babinet Soleil phase plate 32, the incident side polarizer 38, the first outer polarizers 42 to 44, the inner reflection mirror 40, the first outer reflection film 45, and the emission side polarizer 39. A first wavelength filter unit, a second Babinet Soleil phase plate 33, an incident side polarizer 38, second outer polarizers 46 to 48, an inner reflection mirror 40, a second outer reflection film 49, and an output side polarizer 39. Provided integrally with the two-wavelength filter section. According to the present embodiment, since the incident side polarizer 38, the inner reflection mirror 40, and the output side polarizer 39 are common, the number of components is reduced and the configuration is simplified.

  Incident light L1 entering the wavelength filter 31 passes through the first Babinet Soleil phase plate 32 from the light incident port, enters the incident-side polarizer 38, and is split into an s-polarized component and a p-polarized component. The s-polarized light is reflected by the incident-side polarizer at a predetermined angle φ with respect to the normal direction of the principal surface of the Babinet Soleil phase plate, and the first Babinet Soleil phase plate 32 is reflected at the same reflection angle φ with respect to the normal direction. Transmits with multiple reflections. The p-polarized light is transmitted through the incident-side polarizer and is incident on the second Babinet Soleil phase plate 33, and is transmitted therethrough while being subjected to multiple reflection at the same reflection angle θ with respect to the normal direction.

  The s-polarized light Ls reflected by the incident side polarizer passes through the first Babinet Soleil phase plate 32 and is reflected by the first first outer polarizer 38. Next, the s-polarized light Ls is reflected by the inner reflective film 40, and then reciprocates once through the first Babinet Soleil phase plate, and is reflected by the second first outer polarizer 43. Further, the s-polarized light Ls is reflected three times by the inner reflection film and the first outer reflection film 45, reciprocates twice through the first Babinet Soleil phase plate, and is reflected by the last first outer polarizer 44. The The s-polarized light Ls reflected from the first outer polarizer 44 further passes through the first Babinet Soleil phase plate, is reflected by the output-side polarizer 39, and passes through the first Babinet Soleil phase plate again to transmit the light. The light exits from the exit.

The first Babinet Soleil phase plate 32 is configured such that a phase difference of 360 ° is given while light is once transmitted between its main surfaces. Each polarizer includes two polarizers adjacent to each other along the optical path of s-polarized light Ls, that is, an incident-side polarizer 38 and a first outer polarizer 42, a first outer polarizer 42 and a first outer polarizer 43, It arrange | positions so that the phase difference of the 1st outer side polarizer 43 and the 1st outer side polarizer 44 may become 360 degrees, 720 degrees, and 1440 degrees in order, ie, ^2n-1 * 2 (pi), (n: 1-3). ing. Since the first wavelength filter section always has an integer multiple of 2π in this way, transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained.

  Further, the two adjacent polarizers are arranged in a parallel Nicol relationship in which the transmission axes are parallel to each other by aligning the periodic direction of the grating of the wire grid polarizer as described above. Therefore, the s-polarized light Ls reflected by the incident-side polarizer passes through the first Babinet Soleil phase plate 32 while maintaining the polarization direction.

  The p-polarized light Lp that has passed through the incident-side polarizer passes through the second Babinet Soleil phase plate 33, enters the first second outer polarizer 46, and is reflected. Next, the p-polarized light Lp is reflected by the inner reflective film 40, and then reciprocates once through the second Babinet Soleil phase plate, and is incident on the second second outer polarizer 47 and reflected. Further, the p-polarized light Lp is reflected three times by the inner reflection film and the second outer reflection film 49, reciprocates twice through the second Babinet Soleil phase plate, and enters the last second outer polarizer 48. , Reflected. The p-polarized light Lp reflected from the second outer polarizer 48 further passes through the second Babinet Soleil phase plate and enters the output-side polarizer 39, and the output-side polarizer and the first Babinet Soleil phase plate are transmitted through the second Babinet Soleil phase plate. The light passes through and exits from the light exit.

The second Babinet Soleil phase plate 33 is configured such that a phase difference of 360 ° is given while light is once transmitted between the principal surfaces. Each polarizer includes two polarizers adjacent to each other along the optical path of p-polarized light Lp, that is, an incident-side polarizer 38 and a second outer polarizer 46, a second outer polarizer 46 and a second outer polarizer 47, The second outer polarizer 47 and the second outer polarizer 48 are arranged so that the phase difference is sequentially 360 °, 720 °, 1440 °, that is, 2 ⁿ⁻¹ × 2π, (n: 1 to 3). ing. Since the phase difference of the second wavelength filter unit is always an integer multiple of 2π, transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained.

  Further, the two adjacent polarizers are arranged in a parallel Nicol relationship in which the transmission axes are parallel to each other by aligning the periodic direction of the grating of the wire grid polarizer as described above. Therefore, the p-polarized light Lp that has passed through the incident-side polarizer passes through the second Babinet Soleil phase plate 33 while maintaining its polarization direction.

  The s-polarized light that has been transmitted through the first Babinet Soleil phase plate 32 and the p-polarized light that has been transmitted through the second Babinet Soleil phase plate 33 are combined by the output-side polarizer 39 to be incident light from the light output port as one output light L2. The light is emitted in a direction different from L1. Thereby, the wavelength filter 31 with less loss of the amount of emitted light than the amount of incident light and high light utilization efficiency is realized. Further, in the first and second wavelength filter units, the wavelength filter 31 has the first and second Babinet Soleil phase plates 32 and 33 in common regardless of the number of polarizers provided on the outer principal surface thereof. In addition to the fact that only one is required, the incident side polarizer, the inner reflection film, and the output side polarizer are shared between the first and second filter sections, so that the number of components is greatly reduced. In addition, the overall length and size of the apparatus can be suppressed.

  In the wavelength tunable filter 31 of this embodiment, by driving the actuators in the first and second Babinet Soleil phase plates 32 and 33, the wavelength of light passing through them changes, so that the transmission spectrum wavelength can be freely changed. Can be made. In particular, the Babinet Soleil phase plate using a birefringent plate made of quartz exhibits high transmittance even in a short wavelength range from ultraviolet to blue. Therefore, a tunable filter capable of variably controlling the transmission spectrum wavelength for light in a wide wavelength range including a short wavelength range is realized. In addition, since the Babinet Soleil phase plate is excellent in heat resistance, the heat resistance of the wavelength tunable filter 31 is greatly improved as compared with the conventional technique using a liquid crystal cell.

2A to 2D show the results of simulating the wavelength characteristics of the wavelength tunable filter 31, that is, the transmittance of the peak of the transmission spectrum. FIGS. 2A to 2D show transmittances relating to the wavelengths of light at the positions P1 to P4 shown in FIG. 1B along the optical path of the light transmitted through the first Babinet Soleil phase plate 32, respectively. Shows changes. Here, λ ₀ is a specific wavelength, that is, a wavelength of incident light, and λ is a wavelength of transmitted light or outgoing light at each of the positions P1 to P4. In the figure, the solid line indicates the case where the optical thickness of the first Babinet Soleil phase plate 32 is a reference value, and the broken line indicates the case where the optical thickness of the Babinet Soleil phase plate is made thinner than the reference value. Represents.

  After the incidence, at the position P1 of the optical path after being reflected from the incident-side polarizer 38, the light transmittance is constant 50% in the entire wavelength range (FIG. 2A). The position P2 of the optical path after being reflected from the first outer polarizer 42 first shows transmission characteristics between the adjacent polarizers, and has a peak at a wavelength that is an integer multiple of the specific wavelength (FIG. 2B )). Next, since the transmission characteristics between the adjacent polarizers have a peak at a wavelength that is an integral multiple of ½ wavelength of the specific wavelength, at the position P3 of the optical path after being reflected from the first outer polarizer 43, The transmission characteristics obtained by superimposing this and FIG. 2B are shown (FIG. 2C). Finally, since the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of a quarter wavelength of the specific wavelength, this is further reduced at the position P4 after being reflected from the first outer polarizer 44. FIG. 2C shows the superimposed transmission characteristics (FIG. 2D).

  Since the peaks of the transmission spectra between the adjacent polarizers all overlap at a wavelength that is an integral multiple of the specific wavelength, the first wavelength filter unit is an integer of the specific wavelength as shown in FIG. Transmission characteristics having double and steep peaks can be obtained. Here, when the optical thickness of the first Babinet Soleil phase plate 32 is changed by driving the actuator, the transmission characteristics are such that the peak wavelength is as shown by a broken line in FIGS. Shift to the high wavelength side or the low wavelength side. Note that the transmission characteristics of the second wavelength filter unit of the second Babinet Soleil phase plate 33 are the same as those of the first wavelength filter unit, and thus description thereof is omitted.

FIG. 3 schematically shows a configuration of a modification of the first embodiment. The wavelength filter 31 ₁ of this embodiment is different from that of the first embodiment in that the output side polarizer 39 ₁ has its polarization direction oriented parallel to the paper surface. That is, the exit side polarizer 39 ₁ is arranged periodic direction of the grating of the wire grid polarizer in a direction rotated 90 ° with respect to the exit side polarizer 39 of the first embodiment.

S polarized light reflected on the first outer polarizer 44 of the last transmitted through the first Babinet Soleil phase plate 32 is transmitted through the exit side polarizer 39 _1. P polarized light reflected on the second Babinet Soleil phase plate 33 and the second outer polarizer 48 of the last pass through the is reflected by the exit side polarizer 39 _1. The first Babinet Soleil phase plate 32 and the second Babinet Soleil phase plate 33 a s polarized light transmitted respectively p-polarized light, is synthesized by the exit side polarizer 39 _1, the first Babinet Soleil phase plate 32 side the light exit The vicinity of the end 33b (right side in the figure) of the outer main surface of the second phase shifter 33 located on the back side of the mouth is used as a light exit, and the light is emitted to the outside in the same direction as the incident light L1. In this embodiment, the direction of the emitted light L2 can be changed in this way. Other configurations are the same as those of the wavelength filter 31 of FIG.

FIG. 4 schematically shows the configuration of another modification of the first embodiment. Wavelength filter ₃₁₂ of the present embodiment, in addition to oriented parallel examples similarly to the polarization direction of the output-side polarizer 39 ₁ of FIG. 2 with respect to the paper surface, the polarized light incident side polarizer 38 ₁ The direction is oriented parallel to the paper surface, and the polarization directions of the first external polarizers 42 _{1 to} 44 ₁ and the second external polarizers 46 _{1 to} 48 ₁ are opposite to those of the first embodiment. However, this is different from the first embodiment. The first external polarizers 42 _{1 to} 44 ₁ have their polarization directions oriented parallel to the paper surface, and the second external polarizers 46 _{1 to} 48 ₁ have their polarization directions oriented perpendicular to the paper surface. ing.

Thus, the incident light L1 is transmitted through the first Babinet Soleil phase plate 32 from the light entrance, is reflected p-polarized light component by the incident side polarizer 38 _1, multiple reflections within the first Babinet Soleil phase plate 32 While transmitting. s-polarized light component is incident on the second Babinet Soleil phase plate 33 is transmitted through the incident side polarizer 38 _1, it transmits with multiple reflections therein. Wherein the first Babinet Soleil phase plate and the 2 p-polarized light Babinet Soleil phase plate were respectively transmit and s-polarized light, is synthesized by the exit side polarizer 39 _1, the light emission opening of the first Babinet Soleil phase plate 32 side To the outside. As described above, it can be freely set as to which of the first and second Babinet Soleil phase plates 32 and 33 s-polarized light and p-polarized light are transmitted. Other configurations are the same as those of the wavelength filter 31 of FIG.

FIG. 5 schematically shows the configuration of still another modification of the first embodiment. Wavelength filter ₃₁₃ of the present embodiment omits the exit side polarizer 39, and _{which one} end of the first outer polarizer 44 is oriented parallel to the embodiment similarly to the paper surface of the polarization direction in FIG. 3 This is different from the first embodiment. As a result, the s-polarized light transmitted through the first Babinet Soleil phase plate 32 is incident on the last first outer polarizer 44, is transmitted therethrough, and is emitted to the outside as it is. The p-polarized light transmitted through the second Babinet Soleil phase plate 33 enters the last second outer polarizer 48 and is reflected. The reflected p-polarized light is transmitted through the second Babinet Soleil phase plate, the adhesive 41 and the first Babinet Soleil phase plate 32, and is emitted to the outside. In this case, the adhesive 41 is preferably one that has sufficient optical transparency at the desired transmission wavelength range of the wavelength filter 31 _3.

As described above, according to this embodiment, two lights having different polarization components in a desired wavelength region can be extracted separately. Further, when the first Babinet Soleil phase plate 32 and the second Babinet Soleil phase plate 33 are set to different optical thicknesses, light of two different wavelengths can be extracted. For example, the wedge angle θ1 of the first Babinet Soleil phase plate 32 may be set to be different from the wedge angle θ2 of the second Babinet Soleil phase plate 33, or each Babinet Soleil phase plate may be driven separately. In yet another embodiment, it can be synthesized by separately emitting the two beams of the wavelength filter 31 _third polarization beam splitter and a birefringent plate such as an optical means arranged outside.

FIG 6 (A) ~ (D) shows the wavelength characteristics of the wavelength tunable filter 31 _3, i.e. the results of simulation of the transmittance of the peak of the transmission spectrum. 6 (A) to 6 (D) respectively show transmittances relating to the wavelengths of light at the positions P1 to P4 shown in FIG. 5 (B) along the optical path of the light transmitted through the first Babinet Soleil phase plate 32 and emitted. Shows changes. Here, λ ₀ is a specific wavelength, that is, a wavelength of incident light, and λ is a wavelength of transmitted light or outgoing light at each of the positions P1 to P4. In the figure, the solid line indicates the case where the optical thickness of the first Babinet Soleil phase plate 32 is a reference value, and the broken line indicates the case where the optical thickness of the Babinet Soleil phase plate is made thinner than the reference value. Represents.

  After the incidence, at the position P1 of the optical path after being reflected from the incident side polarizer 38, the light transmittance is constant 50% in the entire wavelength range (FIG. 6A). The position P2 of the optical path after being reflected from the first outer polarizer 42 first shows transmission characteristics between the adjacent polarizers, and has a peak at a wavelength that is an integral multiple of the specific wavelength (FIG. 6B )). Next, since the transmission characteristics between the adjacent polarizers have a peak at a wavelength that is an integral multiple of ½ wavelength of the specific wavelength, at the position P3 of the optical path after being reflected from the first outer polarizer 43, A transmission characteristic obtained by superimposing this on FIG. 6B is shown (FIG. 6C). Finally, since the transmission characteristic between the adjacent polarizers has a peak at a wavelength that is an integral multiple of a quarter wavelength of the specific wavelength, this is further reduced at the position P4 after being emitted from the first outer polarizer 44. FIG. 6C shows the superimposed transmission characteristics (FIG. 2D).

  Since the peaks of the transmission spectra between the adjacent polarizers all overlap at a wavelength that is an integral multiple of the specific wavelength, the first wavelength filter unit is an integer of the specific wavelength as shown in FIG. Transmission characteristics having double and sharp peaks can be obtained. Here, when the optical thickness of the first Babinet Soleil phase plate 32 is changed by driving the actuator, the transmission characteristics are shown in FIG. 6A to FIG. Shift to the high wavelength side or the low wavelength side. Note that the transmission characteristics of the second wavelength filter unit of the second Babinet Soleil phase plate 33 are the same as those of the first wavelength filter unit, and thus description thereof is omitted.

FIG. 7 schematically shows the configuration of still another modification of the first embodiment. Wavelength filter 31 ₄ of this embodiment, in that replaced the absorptive polarizer said first and second outer polarizer from the wire grid polarizer, different from the first embodiment. As an absorptive polarizer, there is a dichroic polarizing plate using a resin film or a sheet, for example. Since the absorption polarizer has a property of transmitting light of a predetermined wavelength or wavelength range, it is necessary to provide a reflective film on the back side thereof.

  On the outer principal surface of the first Babinet Soleil phase plate 32, first outer polarizers 50 and 51 made of absorption polarizers are positioned at the positions of the first outer polarizers 42 and 43 of the first embodiment. The first outer polarizers 52 are respectively arranged at the positions of the first outer polarizers 44 of the first embodiment, and the first outer reflective film 53 and the first outer reflective film 54 are laminated thereon. On the outer principal surface of the second Babinet Soleil phase plate 33, second outer polarizers 55 and 56 made of absorption polarizers are positioned at the positions of the second outer polarizers 46 and 47 of the first embodiment. The second outer polarizers 52 are respectively arranged at the positions of the second outer polarizers 48 of the first embodiment, and the first outer reflection film 58 and the first outer reflection film 59 are laminated thereon. Other configurations are the same as those of the wavelength filter 31 of FIG.

  Also in this embodiment, the polarization direction of each polarizer can be changed as in the embodiment of FIG. Further, the present embodiment is configured as in the embodiment of FIG. 5, omits the exit side polarizer 39, and changes the polarization direction of the first outer polarizer 44 to separately separate two lights of different polarization components. Can be taken out. In addition, the first and second Babinet Soleil phase plates 32 and 33 can be set to different optical thicknesses to extract light having two different wavelengths.

FIG. 8 schematically shows the configuration of still another modification of the first embodiment. Wavelength filters 31 ₅ of the present embodiment, in the embodiment of FIG. 2 are replaced with absorptive polarizer EXAMPLE similarly to the first and second outer polarizer of Figure 5 from the wire grid polarizer . According to the present embodiment, the s-polarized light and p-polarized light transmitted through the first and second Babinet Soleil phase plate, synthesized by the exit side polarizer 39 _1, the outer main surface of second Babinet Soleil phase plate 33 The vicinity of the end portion 33b (right side in the figure) can be used as a light emission port to be emitted to the outside in the same direction as the incident light L1. Other configurations are the same as those of the wavelength filter 31 of FIG.

  FIG. 9 schematically shows the configuration of a second embodiment of the wavelength filter according to the present invention. In the wavelength filter 61 of this embodiment, the first and second Babinet Soleil phase plates 62 and 63 are shorter than those of the first embodiment, and the exit side polarizer 69 sandwiched between them is an entrance side polarizer 68. And the inner reflective film 70. A first outer polarizer 72 made of a wire grid polarizer and a first outer reflecting film 73 are disposed on the outer main surface of the first Babinet Soleil phase plate 62. A second outer polarizer 75 made of a wire grid polarizer and a second outer reflection film 76 are disposed on the outer principal surface of the second Babinet Soleil phase plate 63. The laminated first and second Babinet Soleil phase plates 62 and 63 are provided with vertical reflecting films 74 and 77 on the end faces opposite to the light incident direction, respectively.

  The s-polarized component of the incident light L 1 reflected by the incident side polarizer 68 passes through the first Babinet Soleil phase plate 62 and is reflected by the first outer polarizer 72. Next, the s-polarized light is reflected by the inner reflective film 70, reciprocates once through the first Babinet Soleil phase plate, and is reflected by the first outer polarizer 72 again. Further, the s-polarized light is reflected four times by the inner reflection film, the vertical reflection film 74, and the first outer reflection film 73, reciprocates twice through the first Babinet Soleil phase plate, and again returns to the first outer polarizer 72. And is incident on the exit-side polarizer 69. In this way, the s-polarized light that has passed through the first Babinet Soleil phase plate 62 after multiple reflection is transmitted through the output-side polarizer 69, transmitted through the second Babinet Soleil phase plate 63, and emitted to the outside.

  The p-polarized component of the incident light L1 that has passed through the incident side polarizer is transmitted through the second Babinet Soleil phase plate 63 and reflected by the second outer polarizer 75. Next, the p-polarized light is reflected by the inner reflection film 70, reciprocates once through the second Babinet Soleil phase plate, and is reflected by the second outer polarizer 75 again. Further, the p-polarized light is reflected four times by the inner reflection film, the vertical reflection film 77, and the second outer reflection film 76, is transmitted twice through the second Babinet Soleil phase plate, and is again transmitted to the second outer polarizer 75. And is incident on the exit-side polarizer 69. The p-polarized light that has been transmitted through the second Babinet Soleil phase plate 63 after being reflected in this way is reflected by the output-side polarizer 69, passes through the second Babinet Soleil phase plate 63, and exits to the outside.

Similar to the first embodiment, the first and second Babinet Soleil phase plates 62 and 63 are configured such that a phase difference of 360 ° is given while light is once transmitted between the principal surfaces. The incident side polarizer 68, the output side polarizer 69, and the first and second outer polarizers 72 and 75 are the two polarizers adjacent to each other along the optical path of the first and second Babinet Soleil phase plates 62 and 63. It arrange | positions so that a phase difference may become 360 degrees, 720 degrees, and 1440 degrees in order, ie, ^2n-1 * 2 (pi), (n: 1-3). Thus, since the phase difference is always an integral multiple of 2π, transmission characteristics as a bandpass filter similar to the conventional rio filter can be obtained.

The s-polarized light that has been transmitted through the first Babinet Soleil phase plate 62 and the p-polarized light that has been transmitted through the second Babinet Soleil phase plate 63 are synthesized by the output-side polarizer 69, and the second Babinet Soleil phase plate is obtained as one output light L 2. The light exits from the light exit port of the outer main surface of 63. As a result, the wavelength filter ₆₁ having a high light utilization efficiency with less loss of the emitted light amount than the incident light amount is realized. Further, the wavelength filter 61 is configured such that the light transmitted through the first and second Babinet Soleil phase plates is folded at the end face and travels in both directions, so that the number of components can be significantly reduced compared to the first embodiment. In particular, the length of the device can be reduced.

  As described above with reference to FIG. 1, each of the first and second Babinet Soleil phase plates 32, 33, 62, and 63 in each of the above embodiments is configured such that one of the two birefringent plates is a wedge plate and a parallel plate. It is composed of By combining parallel birefringent plates in this way, the phase difference of the Babinet Soleil phase plate can be set freely in a wide range from 0 ° to infinity, so the transmission wavelength range can be designed with a high degree of freedom. it can.

  In another embodiment, as illustrated below, various configurations of the Babinet Soleil phase plate different from the above embodiment can be used. In this specification, in order to simplify the explanation, the following description will be made in relation to the first babynet soleil plate 32 of FIG. 1, but it goes without saying that the same configuration can be applied to the second babynet soleil plate. Yes.

Babinet Soleil phase plate 32 ₁ shown in FIG. 10 is obtained by omitting the parallel plate 34 ₂ from the first Babinet Soleil plate 32 of FIG. 1. Accordingly, the upper birefringent plate 34 is composed only of a wedge plate. The optical axes Op1 and Op2 of the birefringent plates 34 and 35 are oriented in the same direction and at an angle of 45 ° with respect to the length direction of the Babinet Soleil phase plate, as in the embodiment of FIG. In this case, the first to third polarizers and the upper reflection mirror are provided on the parallel plate surface 34c of the wedge plate. In this way, by configuring the Babinet Soleil phase plate with only two wedge plates, the number of parts can be minimized, and the overall configuration of the filter can be made simpler and more compact.

Babinet Soleil phase plate 32 ₂ shown in FIG. 11, in the first Babinet Soleil plate 32 in FIG. 1, and upside down both birefringent plates 34 and 35, and the parallel plate 34 ₂ and the lower upper birefringent plate 34 The side birefringent plate 35 is arranged to face the parallel flat plate surface 35c. Wedge plate 34 ₁ and the optical axis of the birefringent plate 35 Op1, Op2 is oriented at 45 ° orientation with respect to the length direction of the same direction and the Babinet Soleil phase plate, the optical axis Op3 of the parallel plate 34 ₂ is wedge It is oriented perpendicular to each other with respect to the optical axis Op1 plate 34 _1. In this case, the first to third polarizer and the upper reflection mirror provided on the wedge plate 34 ₁ of the inclined surface on 34d, the lower reflection mirror is provided on the inclined surface of the lower birefringent plate 34. Babinet Soleil phase plate 32 ₂ of the present embodiment, when adjusting the phase difference, the two birefringent plates 34, 35 parallel to the surface direction of the opposing surface, even those in the state of being sliding contact with the opposing surface , It can be driven more smoothly.

Babinet Soleil phase plate 32 ₃ shown in FIG. 12, the Babinet Soleil phase plate 32 ₂ of FIG. 11 is obtained by omitting Example similarly to the parallel plate 34 ₂ of FIG. 10. The upper birefringent plate 34 is composed only of a wedge plate, and the parallel flat plate surface 34c and the parallel flat plate surface 35c of the lower birefringent plate 35 are arranged to face each other. Thus, when adjusting the phase difference of the Babinet Soleil phase plate 32 _3, both birefringent plates 34, 35 parallel to the surface direction of the parallel flat plate surface to its opposite, was sliding them in the parallel flat plate surface Even in the state, it can be driven smoothly. Furthermore, by configuring the Babinet Soleil phase plate with only two wedge plates, the number of parts can be minimized, and the overall configuration of the filter can be made simpler and more compact.

Babinet Soleil phase plate 32 shown in FIG. _{13. 4,} in the embodiment of FIG. 11, the birefringent plate 34 and 35, the inclined surface 34d, bonding the wedge-shaped glass plate 78, 79 of the same wedge angle θ respectively 35d And formed in parallel flat plates. Accordingly, the first to third polarizers, the upper reflection mirror, and the lower reflection mirror are provided on the upper surface of the wedge plate 78 and the lower surface of the wedge plate 79, that is, the parallel flat plate surface, respectively, so that the alignment is easy. Easy to manufacture. Further, the birefringent plate 34 and 35, when adjusting the phase difference of the Babinet Soleil phase plate 32 _4, even them in a state of being sliding in the opposing surface, can be smoothly driven.

Babinet Soleil phase plate 32 ₅ shown in FIG. 14, in the embodiment of FIG. 13 is obtained by omitting the parallel plate 34 ₂ from the upper birefringent plate 34 as with the embodiment of FIG. 10. Thereby, the number of parts can be reduced and the configuration can be simplified. Upper birefringent plate 34 is bonded to the wedge-shaped glass plate 78 in the wedge plate 34 ₁ is formed in a parallel plate, similarly to face the lower birefringent plate 35 by bonding wedge glass plate 79 formed in a parallel plate Arranged. Thus, the birefringent plate 34 and 35, when adjusting the phase difference of the Babinet Soleil phase plate 32 _5, even them in a state of being sliding in the opposing surface, can be smoothly driven.

Babinet Soleil phase plate 32 ₆ shown in FIG. 15, in the embodiment of FIG. 10, the optical axis Op1 of the birefringent plate 34, 35, Op2 are both oriented in the same direction as the longitudinal direction of the Babinet Soleil phase plate ing. In general, it is advantageous to orient the optical axis in the horizontal or vertical orientation with respect to the outer peripheral shape of the birefringent plate, since this makes it easy to manufacture especially in processing of a wedge plate. In this case, corresponding to the orientation of the optical axis of the birefringent plate 35, the polarization axis of the polarizer provided on the upper and lower principal surface of the Babinet Soleil phase plate 32 _6, the implementation of FIG. 1 It is necessary to orient in the direction rotated by 45 ° from the case of the example.

  In still another embodiment, the birefringent plates 34 and 35 are turned upside down in the embodiment shown in FIGS. 13 and 14, and the wedge-shaped glass plates 78 and 79 attached to them are arranged to face each other. Can do. Also, these various configurations of the Babinet Soleil phase plate can be similarly applied to the embodiments of FIGS. 3 to 5 and FIGS. 7 to 9.

  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, each wavelength filter can be configured in a two-stage structure or a multistage structure having four or more stages. Further, 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.

(A) is a plan view schematically showing a first embodiment of a wavelength tunable filter according to the present invention, (B) is a side view showing the traveling direction of light, and (C) is an end face on the incident side. Figure. (A)-(D) are diagrams each showing the transmission characteristics of the first embodiment. (A) is a plan view schematically showing a modification of the first embodiment, (B) is a side view along the light traveling direction, and (C) is an end view on the incident side. FIG. 5A is a plan view schematically showing another modification of the first embodiment, FIG. 5B is a side view showing the traveling direction of light, and FIG. 5C is an end view on the incident side. (A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing along the traveling direction of light, and (C) is an end view on the incident side. . FIGS. 6A to 6D are diagrams each showing transmission characteristics of the embodiment of FIG. (A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing the traveling direction of the light, and (C) is the incident side. End view. (A) is a plan view schematically showing still another modification of the first embodiment, (B) is a side view showing along the traveling direction of light, and (C) is an end view on the incident side. . (A) is a plan view schematically showing a second embodiment of a wavelength tunable filter according to the present invention, (B) is a side view showing the light traveling direction, and (C) is an incident side thereof. End view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. (A) The figure is a side view which shows another structure of a baby-brain soleil phase plate, (B) The figure is the top view. 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

DESCRIPTION OF SYMBOLS 1 ... Rio filter, 2a-2d, 12a-12d, 22a-22d ... Polarizer, 2a1-2d1, 12a1-12d11 ... Transmission axis, 3a-3c ... Birefringent plate, 3a1-3c1 ... Optical axis, 4 ... Optical axis , 11 ... band pass filters, 13a to 13c, 23a to 23c ... liquid crystal cells, 21 ... wavelength tunable filters, 24a to 24c ... phase difference films, 31, 31 _{1 to} 31 ₆ , 61 ... wavelength tunable filters, 32, 32 ₁ 32 ₆ , 33, 62, 63... Babinet Soleil phase plate, 34 to 37, 64 to 67... Wedge-shaped birefringent plate, 34 ₁ , 36 ₁ , 64 ₁ , 66 ₁ ... Wedge plate, 34 ₂ , 36 ₂ , 64 ₂ , 66 ₂ ... parallel flat plates, 38, 38 ₁ , 68 ... incident side polarizer, 39, 39 ₁ , 69 ... output side polarizer, 40, 70 ... inner reflection film, 41, 71 ... adhesive, 42 to 44 , ₄₂ 1 _{to 44} 1, 0～52,72 ... first outer _polarizer, 45, 45 1, 53,54,73 ... first outer reflective _film, 46～48,46 _1-48 1, 55～57,75 ... second outer polarizer 49, 49 ₁ , 58, 59, 76 ... second outer reflection film, 74, 77 ... vertical reflection film, 78, 79 ... wedge-shaped glass plate.

Claims (16)

A first and second retardation element, an incident side polarizer, a first and second outer polarizer, an inner reflection film, and a first and second outer reflection film;
Each of the first and second phase difference elements is disposed in a wedge shape with a thickness decreasing from one end to the other end and facing each other, so that the thickness of each of the phase difference elements is relatively changed. It consists of two displaceable retardation plates,
The first and second retardation elements are stacked with the incident-side polarizer and the inner reflective film sandwiched therebetween, and the first outer polarizer and the outer surface of the first retardation element are stacked on each other. A first outer reflection film is disposed, and the second outer polarizer and the second outer reflection film are disposed on an outer main surface of the second retardation element,
Light incident on the first phase difference element is split into reflected light and transmitted light by the incident side polarizer, and the reflected light passes through the first outer phase polarizer or the first inside the first phase difference element. The outer reflection film and the inner reflection film are multiple-reflected and transmitted at a fixed angle with respect to the normal direction of the phase difference element main surface, and the transmitted light passes through the second phase difference element inside the second outer side. A wavelength tunable filter characterized in that it is subjected to multiple reflection at a fixed angle with respect to a normal direction of the main surface of the phase difference element by a polarizer or the second outer reflection film and the inner reflection film.   The light further includes an output-side polarizer sandwiched between the stacked first and second phase difference elements, and light that has undergone multiple reflections within the first phase difference element and light that has undergone multiple reflections within the second phase difference element Are synthesize | combined by the said output side polarizer, and are radiate | emitted from the said 1st and 2nd phase difference element, The wavelength variable filter of Claim 1 characterized by the above-mentioned. The phase difference Γ _1i between the two polarizers adjacent to each other along the optical path of the light transmitted through the first phase difference element is Γ _1i = 2 ⁱ⁻¹ × with respect to the wavelength of the light transmitted through the optical path. The two polarizers satisfying the relationship of 2π (where i = ₁ to n ₁ , n ₁ : an integer of 2 or more) and adjacent to each other along the optical path of light transmitted through the second phase difference element Phase difference Γ _2i between the wavelengths of light passing through the optical path Γ _2i = 2 ⁱ⁻¹ × 2π (where i = 1 to n ₂ , n ₂ : an integer of 2 or more) 3. The wavelength tunable filter according to claim 1, wherein the wavelength tunable filter is satisfied.   Two polarizers adjacent along the optical path inside the first phase difference element and two polarizers adjacent along the optical path inside the second phase difference element are arranged in a parallel Nicols relationship, respectively. The tunable filter according to claim 1, wherein the tunable filter is provided.   Each of the first and second retardation elements is composed of two wedge-shaped birefringent plates, and the inner birefringent plates facing each of the retardation elements are disposed between the incident-side polarizer and the inner reflective film. The wavelength filter according to any one of claims 1 to 4, wherein the wavelength filters are integrally laminated with a gap therebetween.   The first retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ1, and the second retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ2, and the wedge angle θ1 and the wedge angle θ2 are the same. The wavelength filter according to claim 1, wherein the wavelength filter is provided.   The first retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ1, and the second retardation element is composed of two wedge-shaped birefringent plates having a wedge angle θ2, and the wedge angle θ1 and the wedge angle θ2 are different. The wavelength filter according to claim 1, wherein:   The wavelength filter according to claim 1, wherein the incident side polarizer is a wire grid polarizer.   The wavelength filter according to claim 2, wherein the output side polarizer is a wire grid polarizer.   The wavelength filter according to claim 1, wherein the outer polarizer is a wire grid polarizer.   The wavelength filter according to claim 1, wherein the outer polarizer is an absorptive polarizing plate.   The two retardation plates of at least one of the first and second retardation elements are formed by inclining the opposite surface with a predetermined wedge angle while leaving one surface of the parallel plate as it is, The inclined surfaces are opposed to each other, and the thicker end portion and the thinner end portion are arranged on the same side, and the inclined surfaces are alternately arranged. Or the wavelength filter described.   The two retardation plates of at least one of the first and second retardation elements are formed by inclining the opposite surface with a predetermined wedge angle while leaving one surface of the parallel plate as it is, 12. One of the surfaces according to claim 1, wherein one surface is opposed to each other, and the thicker end portion and the thinner end portion are arranged on the same side and are alternately arranged. Any one of the wavelength filters.   The wavelength according to any one of claims 1 to 13, wherein the two phase difference plates of at least one of the first and second phase difference elements are arranged so that their crystal optical axes are parallel to each other. filter.   The two retardation plates of at least one of the first and second retardation elements are arranged with their crystal optical axes orthogonal to each other. Wavelength filter.   16. The wavelength filter according to claim 1, wherein at least one of the first and second retardation elements further includes a parallel plate retardation plate combined with at least one of the retardation plates. .

Images