JP2009069519A - Wavelength filter and optical device - Google Patents

Abstract

A wavelength filter capable of selectively extracting light of different wavelengths or selectively removing light of a specific wavelength.
In a wavelength filter 31, phase plates 33a to 33c are arranged along a light path between a plurality of polarizers 32a to 32d. Each phase plate has a transmission surface divided into a plurality of regions, and each region has a predetermined different thickness so as to function as a wavelength plate having a different transmission spectrum wavelength. The thicknesses of the respective regions at the same vertical and horizontal positions (i, j) of the respective phase plates are set in a geometric sequence of a common ratio 2 of dij, 2dij, 4dij. Therefore, when white light is incident on the wavelength filter, different transmission wavelengths, that is, light of different colors are emitted for each vertical and horizontal position of each region. As a result, light of different wavelengths can be selected and synthesized, or only specific wavelengths can be removed from the light of the light source.
[Selection] Figure 1

Description

  The present invention relates to a wavelength filter that controls the wavelength of transmitted light and an optical device using the same.

Conventionally, various band-pass filters are used to transmit light in a desired wavelength region. For example, a rio filter is known as a band-pass filter that transmits only narrow-band light using a birefringent plate (see, for example, Patent Documents 1 and 2). FIG. 6 shows a basic configuration of the Rio filter. As shown in the figure, the Rio filter 1 includes birefringent plates 3a to 3c between parallel polarizers 2a to 2d of transmission axes 2a1 to 2d1, and crystal optical axes 3a1 to 3c1 of the polarizer. It arrange | positions so that the transmission axes 2a1-2d1 may make 45 degrees. The birefringent plates 3a to 3c are configured so that the thickness di is 2 ^i-1 d (i = 1 to 3). A uniaxial crystal such as calcite or quartz is used for the birefringent plate.

  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 1 and 3). As shown in FIG. 7, the band pass filter 11 can change 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. 7 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 in which a color filter is combined with a liquid crystal cell in the configuration of FIG. 7 is known (see, for example, Patent Document 4). As shown in FIG. 8, in the wavelength tunable filter 21, retardation films, that is, color filters 24a to 24c are arranged so as to overlap each of the liquid crystal cells 23a to 23c sandwiched between polarizers 22a to 22d. By this color filter, an unnecessary peak can be absorbed from the transmission spectrum, and only one peak can appear in the observation wavelength range, that is, the transmission wavelength range of the color filter.

  On the other hand, it is preferable to use various colors suitable for the purpose or application for indoor lighting of houses, lighting for plants, and lighting of instruments such as vehicles and airplanes. In general, for the purpose of such illumination, a color filter of a color suitable for it is directly used as a light source. In addition, in the field of spectroscopic analysis using a spectrophotometer or the like, in order to measure light of different wavelengths, there is a method of arranging a plurality of monochromatic optical filters having different transmission wavelengths perpendicular to the optical axis and in the same plane. It is general (see, for example, Patent Documents 5 and 6). Furthermore, a light receiving sensor is known in which filter elements having different light transmission characteristics are bonded to the light incident surface of a photodiode array (see, for example, Patent Document 7).

JP 2000-267127 A Japanese Patent No. 3000669 Japanese Patent No. 3102012 JP 2005-115208 A JP-A-6-50880 JP 2000-304615 A JP 2001-50813 A

  However, the conventional rio filter and wavelength tunable filter described above are intended to transmit only one desired single color light, and simultaneously transmit a plurality of single color lights having different wavelengths, or one or more specific wavelengths. The light cannot be removed. Further, the conventional wavelength filter used in the above-described spectroscopic analysis is obtained by simply bonding individual filters to each other or fixing them on a light receiving element or a frame. Therefore, it is troublesome and difficult to assemble each filter with high accuracy. Furthermore, a filter particularly used for illumination is required to have heat resistance enough to withstand the high heat of the light source.

  Therefore, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a highly accurate wavelength filter capable of transmitting a plurality of lights having different wavelengths simultaneously from one light source or incident light. It is to provide.

  A further object of the present invention is to provide an optical device that can selectively extract light of different wavelengths or selectively remove light of a specific wavelength by using such a wavelength filter.

  According to the present invention, in order to achieve the above object, a plurality of polarizers and a phase plate arranged between them are provided, and the phase plate is divided into a plurality of regions having different thicknesses on the transmission surface. Wavelength filters are provided.

Since the phase plate constitutes a multi-division wavelength plate that functions as a wavelength plate having a different phase difference for each region, a single wavelength filter can simultaneously transmit a plurality of lights having different wavelengths.

  Further, according to the present invention, two polarizers and a phase plate disposed between the polarizers are regarded as one block, and k blocks (k: an integer of 2 or more) are disposed along the optical path. The phase plate of the block is divided into a plurality of regions each having a different thickness on the transmission surface, and each of these regions is provided in the same vertical and horizontal position of each phase plate, and the thickness of each region in the same vertical and horizontal position. A wavelength filter having a geometric sequence with a common ratio of 2 is provided.

  The phase plate of each block constitutes a multi-division wave plate that functions as a wave plate having a different phase difference for each region. Therefore, steep narrow band characteristics can be obtained for each region by setting and arranging each phase plate at a predetermined thickness in the same vertical and horizontal positions as in the rio filter.

  In one embodiment, each phase plate is formed of a single quartz plate, so that each region can be made to a predetermined thickness with high accuracy and relatively easily, for example, by wet etching using photolithography. Can be processed.

  According to another aspect of the present invention, the wavelength filter of the present invention described above and shutter means arranged on the incident side or the emission side of the wavelength filter are provided, and the shutter means is the same as each region of the wavelength filter. An optical device is provided that selectively blocks light incident on or emitted from the wavelength filter for each longitudinal and lateral position. Thereby, the light of each wavelength which permeate | transmitted the wavelength filter from the light source can be selected for every said area | region, it can block | intermit or pass, or it can be made to radiate | emit only a specific wavelength.

  In one embodiment, the shutter means is a liquid crystal shutter composed of a plurality of liquid crystal cells arranged in the same vertical and horizontal positions as each region of the wavelength filter, so that it is not necessary to use a mechanical control means. In particular, the operation of blocking light can be controlled relatively quickly and easily with high accuracy, and the entire apparatus can be downsized.

  In another embodiment, by further including a superimposing lens disposed on the emission side of the wavelength filter and shutter means, a plurality of lights emitted at different wavelengths can be combined into one light.

Hereinafter, preferred embodiments of a wavelength filter according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an embodiment of a wavelength filter according to the present invention. As shown in the figure, the wavelength filter 31 of this embodiment includes a plurality of polarizers 32a to 32d arranged in parallel. Between the polarizers, first to third phase plates 33 a to 33 c are arranged along the optical axis 4 in parallel with each other. In this embodiment, two polarizers and the phase plate sandwiched between them are used as one block, and three blocks are arranged in multiple stages in the order of transmission, that is, along the optical path. In another embodiment, four or more multi-stage blocks can be arranged in transmission order.

  The first to third phase plates 33a to 33c are formed of a single quartz plate having a substantially square shape. As shown in FIGS. 2A to 4A, each of the phase plates 33a to 33c has a substantially square area 33a11 to 33a33, 33b11 to 33b33, 33c11 to 33.degree. 33c33. Each of the regions is formed to have a predetermined thickness so as to function as a wave plate. In another embodiment, each of the regions can be provided in various shapes such as a rectangle such as a rectangle, a triangle, and a hexagon, and a circle other than a square.

  The regions 33a11 to 33a33 of the first phase plate 33a shown in FIGS. 2B to 2D have different thicknesses d1111 to d133. The regions 33b11 to 33b33 of the second phase plate 33b shown in FIGS. 3B to 3D have different thicknesses d211 to d233. The regions 33c11 to 33c33 of the third phase plate 33c shown in FIGS. 4B to 4D have different thicknesses d311 to d333. Accordingly, the first to third phase plates 33a to 33c constitute multi-divided wave plates in which the respective regions function as wave plates having different phase differences.

In the first to third phase plates 33a to 33c, the thicknesses of the respective regions at the same vertical and horizontal positions (i, j) (i, j = 1 to 3) have dij, 2dij, 4dij, that is, 2h ^- 1dij (h, i, j = 1 to 3) forming a geometric sequence with a common ratio of 2. In a multi-stage structure in which four or more blocks are arranged, the thickness of each region for each block is 2 ^h−1 dij (h = 1 to k (k: integer of 4 or more); i, j = 1 to 3). Further, when each of the phase plates has a transmission surface divided into m × n regions in the vertical and horizontal directions, the phase plates are in the same vertical and horizontal positions (i, j) (i = 1 to m, j = 1 to n). The thickness of the region is set to 2 ^h−1 dij (h = 1 to k, k: integer of 3 or more) in the order of transmission.

  The polarizers 32a to 32d are arranged in parallel Nicols with their transmission axes 34a to 34d in parallel as in the conventional rio filter. The first to third phase plates 33a to 33c are arranged so that the crystal optical axes 35a to 35c of the respective regions form an angle of 45 ° with the transmission axes 34a to 34d of the respective polarizers. The wavelength filter 31 sets a thickness of each region of the first to third phase plates 33a to 33c as described above, thereby providing a multi-division wavelength filter having a different transmission wavelength for each region having the same vertical and horizontal positions. Constitute. For example, when white light is incident on the wavelength filter 31, the light transmitted through the wavelength filter along the optical path for each vertical and horizontal position of each region is emitted as light of a different color.

  Each of the phase plates can be easily and accurately formed by wet etching a single crystal plate using, for example, a photolithography technique. Each of the phase plates and the polarizer can be bonded to each other using a known adhesive. In this way, a highly accurate multi-division wavelength filter can be realized.

In the wavelength filter 31 of the above embodiment, the thicknesses of the regions in the same vertical and horizontal positions of the first to third phase plates 33a to 33c are set so as to form a geometric sequence with a common ratio of 2 in the order of transmission. According to the present invention, it is not necessary to arrange the thicknesses of the regions forming the geometric sequence of the common ratio 2 in the transmission order, for example, arranging the geometric sequences in the reverse order of the transmission direction, They can be randomly arranged regardless of the transmission order, such as 2dij: dij: 4dij.

  FIG. 5 shows an embodiment of an optical device using the wavelength filter 31 of FIG. The optical device 41 of this embodiment is for use as a part of a lighting device, for example. First and second lens arrays 42 and 43 are arranged on the incident side and the emission side of the wavelength filter 31. A liquid crystal shutter 44 is disposed between the second lens array 43 on the emission side and the wavelength filter 31. A superimposing lens 45 is disposed on the emission side of the second lens array 43. Further, on the incident side of the optical device 41, for example, a light source 46 that generates white light is disposed. In another embodiment, the liquid crystal shutter 44 can be disposed between the incident side of the wavelength filter 31 and the first lens array 42.

  The first and second lens arrays 42 and 43 are so-called fly-eye lenses, and a plurality of small convex lenses are arranged in the same vertical and horizontal positions as the regions of the phase plates 33 a to 33 c of the wavelength filter 31. The light from the light source 46 is transmitted through the first lens array 42, the wavelength filter 31, and the second lens array 43 for each vertical and horizontal position of each region to form a plurality of secondary light source images having different wavelengths. These are superposed by the superimposing lens 45 to become one light with uniform illuminance distribution.

  The liquid crystal shutter 44 has a plurality of liquid crystal cells arranged in the same vertical and horizontal positions as the regions of the phase plates 33 a to 33 c of the wavelength filter 31. Each of the liquid crystal cells can be individually controlled on and off, and light emitted from the wavelength filter 31 can be selected and blocked or allowed to pass for each region. The light that has passed through the liquid crystal shutter 44 passes through the second lens array 43 and is combined into one light by the superimposing lens 45.

  The color of the synthesized light is determined by the transmission wavelength of each region selected by the liquid crystal shutter 44. In another case, only a specific wavelength can be removed from the light from the light source 46 by blocking one specific liquid crystal cell of the liquid crystal shutter 44. As described above, since the optical device 41 of the present invention does not require a mechanical control mechanism, the on / off operation for blocking or passing light can be controlled relatively quickly and easily with high accuracy. In addition, the entire apparatus can be reduced in size.

  As mentioned above, although this invention was demonstrated in detail using the suitable Example, this invention can add and implement various modifications and changes to the said Example in the technical range. For example, each of the phase plates can constitute a multi-divided wave plate by joining and integrating small wave plates formed individually. For each of the phase plates, a conventionally known uniaxial crystal material can be used in addition to quartz. The optical device shown in FIG. 5 can use a collimator instead of the first lens array to allow parallel light to enter the wavelength filter.

The block diagram of the Example of the wavelength filter by this invention. (A) is a perspective view of the first phase plate of FIG. 1, and (B) to (D) are explanatory views showing respective regions in the longitudinal direction. (A) is a perspective view of the second phase plate of FIG. 1, and (B) to (D) are explanatory diagrams showing respective regions in the longitudinal direction. (A) is a perspective view of the third phase plate of FIG. 1, and (B) to (D) are explanatory views showing respective regions in the longitudinal direction. The block diagram of the optical apparatus using the wavelength filter of this invention. The figure which shows the basic composition of a Rio filter. The block diagram of the prior art example of the wavelength filter using a liquid crystal cell. The block diagram of another prior art example of the wavelength filter using a liquid crystal cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rio filter, 2, 12a-12d, 22a-22d, 32a-32d ... Polarizer, 2a1-2d1, 12a1, 12b1, 3a1-3c1, 34a-34d ... Transmission axis, 35a-35c ... Optical crystal axis, 3a -3c: birefringent plate, 11: band pass filter, 13a-13c, 23a-23c ... liquid crystal cell, 21 ... wavelength tunable filter, 31 ... wavelength tunable filter, 33a-33c ... phase plate, 33a11-33a33, 33b11-33b33 , 33c11 to 33c33 ... area, 42, 43 ... lens array, 44 ... liquid crystal shutter, 45 ... superimposing lens, 46 ... light source.

Claims (6)

  A wavelength filter comprising: a plurality of polarizers; and a phase plate disposed between the polarizers, wherein the phase plate is divided into a plurality of regions having different thicknesses on a transmission surface.   Two polarizers and a phase plate arranged between the polarizers are regarded as one block, and it is composed of k blocks (k: an integer of 2 or more) arranged along the optical path. Are divided into a plurality of regions each having a different thickness on the transmission surface, and each region is provided at the same vertical and horizontal position of each phase plate, and the thicknesses of the respective regions at the same vertical and horizontal positions are publicly known. A wavelength filter characterized by forming a geometric sequence of ratio 2.   The wavelength filter according to claim 1, wherein each of the phase plates is formed of a single quartz plate.   A wavelength filter according to any one of claims 1 to 3, and shutter means disposed on an incident side or an emission side of the wavelength filter, wherein the shutter means is provided for each vertical and horizontal position of each region of the wavelength filter. In addition, the optical device is characterized in that it selectively blocks light incident on or emitted from the wavelength filter.   5. The optical device according to claim 4, wherein the shutter means is a liquid crystal shutter including a plurality of liquid crystal cells arranged in the same vertical and horizontal positions as the respective regions of the wavelength filter.   The optical apparatus according to claim 4, further comprising a superimposing lens disposed on an emission side of the wavelength filter and the shutter unit.

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