JP2017049432A - Wavelength plate unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength plate unit equipped with a structure that prevents the rotational deviation of a wavelength plate relative to a holder body, and that makes it possible to accurately mount an optical axis to the holder body at a prescribed intersection angle without using a plurality of wavelength plates or by means of an adhesive or an optical contact.SOLUTION: A wavelength plate unit is constituted by forming, on a first wavelength plate 2 and a second wavelength plate 3, a front eave 8 having orientation flats 10a, 10b indicting the direction of an optical axis and having, on a spacer 5 interposed between the two wavelength plates, a first flat part aligned and closely contacted with the orientation flat 10a of the first wavelength plate 2 from a side edge, a rear eave 9 having a second flat part aligned and closely contacted with the orientation flat 10b of the second wavelength plate 3 from the side edge, and a salient 6 projecting to the outer circumference and engaging with a recess 7 of a holder body 1, forming an air gap between the first wavelength plate 2 and the second wavelength plate 3, and integrating the two wavelength plates, the salient 6 being engaged with the recess 7 of the holder body and a fixing member 4 being screwed into the holder body 1, whereby the positions in rotational direction of the two wavelength plates are restricted and fixed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a wave plate unit which is an optical element for giving a predetermined phase difference to linearly polarized light, and more particularly to a wave plate unit having a structure suitable for a compound zero order system.

  The wave plate unit is also called a phase shifter or phase retardation, and is configured using a birefringent material such as quartz or mica. When the light beam passes through the birefringent material, it is separated into two light beams (normal light beam and extraordinary light beam) having different phases (different vibration directions) and emitted from the wave plate unit. A phase shift (phase difference) due to the refractive index of the birefringent material occurs in both the emitted lights.

  This type of wave plate unit is roughly classified into three types: a true zero order type, a multi-order type, and a compound zero order type. A true zero order type wave plate unit is composed of a single birefringent plate having a thickness that obtains a predetermined phase difference in the 0th order at the design wavelength. The multi-order type wave plate unit uses a single thick birefringent plate as in the true zero order type, and is designed so that a predetermined phase difference can be obtained at a high order. However, this type of wave plate unit is liable to cause a phase shift due to a minute shift in wavelength, temperature change, etc., as the plate thickness increases.

  The compound zero order type wave plate unit that is particularly targeted by the present invention is a position generated in each wave plate by arranging the optical axes of two wave plates made of homogeneous materials processed into multi-order type wave plates at right angles to each other. The phase shift is offset, and the wavelength dependence and temperature dependence of the obtained phase difference are reduced. The structure for assembling the wave plate of the present invention to the holder body is not limited to a compound zero order type wave plate unit, but also applies to true zero order type and multi order type wave plate units using a single thick birefringent plate. It can be done.

  FIG. 9 is an exploded perspective view for explaining the structure of a conventional compound zero order type wave plate unit. This wave plate unit 200 has a stopper 15 at one end, the other end is released, and a first wave plate 2 is formed inside a cylindrical holder body 1 in which a female screw 13 is formed on the inner periphery of the opening of the opening. A second wave plate 3 is attached. Then, the ring-shaped fixing member 4 provided with the male screw 14 on the outer peripheral surface is screwed into the female screw 13 provided on the inner periphery of the holder body 1, and the first wave plate 2 and the second wave plate 3 are pressed. It is fixed. In the following description, the wave plates 2 and 3 are assumed to be thin quartz plates (quartz plates). Reference numeral 12 denotes a groove (driver tooth contact groove) on which a driver's teeth for screwing the fixing member 4 are applied.

  The first wave plate 2 and the second wave plate 3 have a disc shape, and a flat portion (orientation flat: abbreviated orientation flat) indicating their optical axis direction is formed on the outer periphery. In the compound zero order type wave plate unit, the optical axes of the first wave plate 2 and the second wave plate 3 are arranged so as to intersect each other so as to be orthogonal to each other. The orientation flat direction of the second wave plate 3 intersects at right angles (orthogonal) in the plane of the wave plate.

  Patent Document 1, Patent Document 2, and Patent Document 3 can be cited as disclosures of related art related to the wave plate unit according to the present invention. Patent Document 1 describes a half-wave plate unit in which optical axes of two quartz plates are orthogonally arranged on a short cylindrical holder. Patent Document 2 discloses a polarization conversion unit in which spacers are interposed between the peripheral edges of a plurality of wave plates. Patent Document 3 discloses a combined wave plate unit in which the thickness of a wave plate is set to a desired value by forming a dielectric multilayer film on a birefringent plate.

JP 2010-128329 A JP 2011-176282 A JP 2010-60922 A

  In the work of mounting a birefringent plate (retardation plate, hereinafter also referred to as a crystal plate) on the holder body 1 and assembling it into a unit, a first wave plate (crystal plate) 2 and a second wave plate (crystal plate) 3 A highly skilled worker uses the orientation flats formed in each of these as the assembly position reference and visually aligns them. The quality of each worker is slightly different depending on the level of skill of each worker. Since the two quartz plates 2 and 3 are only pressed with a force perpendicular to the rotational displacement direction, both the quartz plate and the holder body are used as the frequency plate unit is used more frequently. Rotational deviation is likely to occur.

  As a means for preventing rotation deviation between the two quartz plates 2 and 3, a method of bonding both quartz plates using an adhesive, or a so-called optical contact in which the joining surfaces are polished and bonded with high precision A method of integrating both quartz plates by a method is known. Even in the pasting, a high level of skill is required for the operator in order to prevent the rotational deviation from occurring on the optical axis. Further, when bonding or optical contact is adopted, it is necessary to add a manufacturing process for that purpose.

  The purpose of the present invention is to prevent rotation of the wave plate with respect to the holder body, and even with the use of a plurality of wave plates, the optical axis is accurately mounted on the holder body at a predetermined crossing angle without using adhesives or optical contacts. It is to provide a wave plate unit having a possible structure. The wave plate unit according to the present invention is not limited to the compound zero order type, but can be applied to assembling various wave plates such as a true zero order type and a multi order type.

  In order to achieve the above object, the present invention employs a structure in which a ring plate is combined with a wave plate in advance and integrated, and rotation prevention means provided on the spacer is fitted to the holder body. In the case of using a plurality of (for example, two) wave plates, a ring-shaped spacer is interposed between the wave plates, and an air gap is provided between the wave plates so as to be integrated. A structure in which the means is fitted to the holder body is adopted. In particular, in the case of using two wave plates, means (庇) for restricting the optical axis directions of the two wave plates are provided on the front and rear sides of the spacer, respectively, and a predetermined outer circumference of the spacer is provided. A convex portion was formed to fit two wave plates combined with the optical axis into the concave portion of the holder body. And the ring-shaped fixing member was screwed and fixed to the holder main body from the back of the two wave plates integrally combined with the spacer. A typical configuration of the wave plate unit according to the present invention will be described below.

(1) A cylindrical holder body having a ring-shaped stopper made of an inner fringe at one end that is the front and having a recess in a part of the inner wall, the other end being the rear being released, a disc-shaped wave plate, A ring-shaped spacer disposed on the rear side of the wave plate, and a ring-shaped fixing member provided on the rear side of the spacer,
The wave plate unit mounted inside the holder body and the wave plate unit fixed by pressing in the stopper direction with the ring-shaped fixing member from the rear side of the spacer,
The wave plate has an orientation flat indicating the optical axis direction of the wave plate at a part of the periphery of a thin plate made of a birefringent material,
The spacer is formed with a flange having a flat portion that is aligned and intimately contacted from the side edge with the orientation flat of the wave plate, and a convex portion that protrudes to the outer periphery and fits into the concave portion of the holder body,
The wave plate of the wave plate integrated with the spacer by fitting the convex portion into the concave portion of the holder body while integrating and aligning the flange of the spacer with the orientation flat of the wave plate The position in the rotation direction is restricted.

(2) A cylindrical holder body having a ring-shaped stopper made of an inner fringe at one end that is the front, a recess in a part of the inner wall, and the other end being the rear is released, and a disk-shaped first A wave plate and a second wave plate, a ring-shaped spacer interposed between the first wave plate and the second wave plate, and a ring-shaped fixing member,
Inside the cylindrical holder body, the first wave plate is mounted on the front side, and the second wave plate is mounted in parallel on the rear side with the spacer interposed therebetween,
A wave plate unit in which the first wave plate and the second wave plate are pushed and fixed in the stopper direction into the holder body by the ring-shaped fixing member from the rear side of the second wave plate. There,
Each of the first wave plate and the second wave plate has an orientation flat indicating an optical axis direction of the wave plate at a part of a periphery of a thin plate made of a birefringent material having the same diameter,
The spacer includes a front ridge having a first flat portion aligned and closely in contact with the orientation flat of the first wave plate from a side edge, and the second wavelength on the side opposite to the first wave plate. A rear ridge having a second flat portion that is aligned and intimately contacted from the side edge to the orientation flat on the plate, and a convex portion that protrudes to the outer periphery and fits into the concave portion of the holder body,
The front collar and the rear collar of the spacer are formed at a predetermined angle apart from each other,
The first edge of the spacer is aligned and closely aligned with the orientation flat of the first wave plate, and the rear edge of the spacer is aligned and closely aligned with the orientation flat of the second wave plate. An air gap is formed between the second wave plate and the second wave plate, and the two wave plates are integrated, and the convex portion is fitted into the concave portion of the holder body, thereby integrating with the spacer. The rotational position of the two wave plates is regulated.

  (3) The compound zero order type wave plate unit is configured with the angle formed by the optical axis of the first wave plate and the optical axis of the second wave plate in (2) being 90 degrees.

(4) In any one of the above (1) to (3), the holder body has an internal thread on the inner wall, and an external thread that engages with the internal thread on the outer periphery of the fixing member,
The first wave plate mounted on the holder main body, the spacer, and the second wave plate are fixed to the stopper by fixing the male screw of the fixing member and the female screw of the holder main body. It is fixed by pressing between the members.

  (5) In any one of (1) to (4), the wavelength plate is formed of a thin crystal plate.

  (6) In any one of (1) to (5), an axial groove for identifying the axial direction of the optical axis of the wave plate is provided in a part of the outer periphery of the holder body.

  (7) In the above (5), an X-cut or Y-cut quartz plate is used as the quartz thin plate.

  The present invention is not limited to the above-described configuration, and it goes without saying that various modifications can be made without departing from the technical idea of the present invention. For example, modifications such as a configuration in which an orientation flat provided on the birefringent plate is formed in parallel to two locations of the birefringent plate and two ridges are provided at positions corresponding to the spacers are also included in the technical idea of the present invention. Included in the range. Moreover, it is applicable also to what used the wavelength plate as a plurality of 3 or more.

  According to the present invention, there is provided a structure capable of preventing rotation of a wave plate and accurately mounting a plurality of wave plates on a holder body at a predetermined crossing angle without using an adhesive or an optical contact. A wave plate can be provided. The assembly structure of the wave plate unit according to the present invention can be applied to various wave plates of a true zero order type, a multi order type, and a compound zero order type.

  In a true zero order type or multi-order type wave plate with a structure using one birefringent plate (wavelength plate) such as a quartz plate, the wrinkles provided on the spacers depend on the orientation flat formed on the birefringent plate, By forming one or a plurality of projections only on the opposite side of the birefringent plate, rotation in the optical axis direction can be prevented. In a compound zero order type wave plate having a structure using two birefringent plates, the flanges provided on the spacer are respectively formed on the side facing the one birefringent plate and on the side facing the other birefringent plate. The rotation of the optical axis can be prevented by forming one or more according to the formed orientation flats.

  According to the present invention, it is possible to obtain an accurate wave plate unit free from rotational deviation regardless of the level of skill of an assembly worker.

It is a perspective view explaining Example 1 of the wave plate unit concerning the present invention. It is a disassembled perspective view explaining the structure of Example 1 of the wavelength plate unit which concerns on this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is detail drawing of the holder main body which comprises Example 1 of the wavelength plate unit which concerns on this invention, The figure (a) shows the upper surface which provided the plane and the index groove | channel (index) of the optical axis seen from back. FIG. 5B shows a cross section taken along line X-X ′ of FIG. It is explanatory drawing of the spacer which comprises Example 1 of the wavelength plate unit which concerns on this invention. It is explanatory drawing of the external thread provided in the fixing member which comprises Example 1 of the wavelength plate unit which concerns on this invention. It is a figure explaining the other example of the fixing member which comprises Example 1 of the wavelength plate unit which concerns on this invention. It is a disassembled perspective view explaining the structure of Example 2 of the wavelength plate unit which concerns on this invention. It is a disassembled perspective view explaining the structure of Example 3 of the wavelength plate unit which concerns on this invention. It is a disassembled perspective view explaining the structure of the conventional wavelength plate unit.

  Hereinafter, embodiments of a wave plate unit according to the present invention will be described in detail with reference to the drawings of the examples.

  FIG. 1 is a perspective view for explaining a first embodiment of a wave plate unit according to the present invention. The wave plate unit 100 of the present embodiment is a compound zero order type wave plate unit, and is interposed between the two wave plates 2 and 3 and the wave plates 2 and 3 in the cylindrical holder body 1, and both wavelengths. An air gap is formed between the plates to form a spacer 5 for integrating the two wave plates, and a fixing member 4 for fixing the two wave plates 2 and 3 integrated by the spacers inside the holder body 1.

  A groove 11 indicating the regular cubic position of the wave plate unit 100 is formed in a part of the outer peripheral surface of the holder body 1 in the axial direction of the wave plate unit 100. The index groove (index, axial groove) 11 is provided, for example, in a plane orthogonal to the optical axis of the wave plate 2. D shown in FIG. 1 is the outer diameter of the holder body 1, and d is the inner diameter. Two wave plates 2 and 3 integrated by a spacer 5 are fixed inside the holder body 1 by using a fixing member 4 having an outer diameter screwed into the inner diameter d. Reference numeral 42 denotes a groove (driver tooth contact groove) to which a driver's teeth are applied when the fixing member 4 is screwed.

  FIG. 2 is an exploded perspective view for explaining the configuration of the first embodiment of the wave plate unit according to the present invention shown in FIG. FIG. 3 is a detailed view of the holder main body, and FIG. 3A shows a plane viewed from the rear and an upper surface provided with an index groove (index) of the optical axis. FIG. 5B shows a cross section taken along line X-X ′ of FIG. FIG. 4 is an explanatory diagram of the spacer. 5 is an explanatory diagram of a male screw provided on the fixing member, and FIG. 6 is a diagram illustrating another example of the fixing member.

  The holder main body 1 has a cylindrical shape as a whole, and an inner fringe (stopper) 15 protruding in a ring shape is formed on the inner periphery of the opening at one end of the front of the cylinder. The inner periphery of the wave plate, which will be described later, is pressed against the inner fringe 15, and the wave plate is fixed by pressing the fixing member 4. A recess 7 described later is formed in a part of the inner fringe 15.

  A female screw 13 is formed on the inner periphery behind the inner fringe 15 of the holder body 1 in the axial direction. In the holder body 1, a first wave plate 2 and a second wave plate 3 are integrated and inserted by a spacer 5 interposed between both wave plates. The first wave plate 2 and the second wave plate 3 integrated by the spacer 5 are pushed in by a fixing member 4 screwed from the rear end, and are sandwiched and fixed by the inner fringe 15 and the fixing member 4. A male screw 14 is provided on the outer periphery of the fixing member 4, and the fixing member 4 is attached to the female screw 13 of the holder body 1 with a driver having wide teeth or bifurcated teeth in a driver tooth contact groove 42 provided on the back surface (outside). Screw in.

  That is, in a compound zero order type wave plate unit using two birefringent plates (retardation plates, here, quartz plates), a ring-shaped ring formed of an inner fringe 15 at one end in front of the cylindrical holder body 1 is used. It has a stopper and a recess 7 in a part of the inner wall, and the other end at the rear is open. Both the first wave plate and the second wave plate have a thin disk shape, and orientation flats 10a and 10b indicating the direction of the optical axis are formed at end portions of the periphery that do not interfere with the optical path. A ring-shaped spacer 5 is interposed between the first wave plate 2 and the second wave plate 3 so that the first wave plate 2 and the second wave plate 3 are integrated. Then, a ring-shaped fixing member 4 is screwed into the holder main body 1 from behind the first wave plate 2 and the second wave plate 3 integrated by the spacer 5.

  As described above, in this embodiment, the first wave plate 2 is mounted on the front side of the cylindrical holder body 1 and the second wave plate 3 is mounted on the rear side with the spacer 5 interposed therebetween. ing. Then, the first wave plate 2 and the second wave plate 3 are pushed and fixed in the direction of the stopper 15 into the holder body from the rear side of the second wave plate 3 by the ring-shaped fixing member 4. The first wave plate and the second wave plate have an optical axis of the wave plate on a part of the periphery of a thin plate made of a quartz plate (X cut or Y cut) which is a birefringent material having the same diameter. Each has an orientation flat indicating direction. This wave plate is a compound zero order type.

  The spacer 5 includes a front ridge 8 having a first flat portion aligned and closely in contact with the orientation flat 10a of the first wave plate from the side edge, and a second wave plate on the opposite side of the first wave plate. A rear flange 9 having a second flat portion that is aligned and intimately contacted from the side edge, and a convex portion 6 that protrudes to the outer periphery and fits into the concave portion 7 of the holder body 1. The front rod 8 and the rear rod 9 are formed at a predetermined angle apart from each other.

  By aligning and closely contacting the front flange 8 of the spacer 5 with the orientation flat 10a of the first wave plate 2, and aligning and closely contacting the rear flange of the spacer 5 with the orientation flat 10b of the second wave plate 3 An air gap corresponding to the thickness of the spacer 5 is formed between the wave plate and the second wave plate to integrate the two wave plates. Then, by fitting the convex portion 6 of the spacer 5 into the concave portion 7 of the holder body 1, the rotational direction position of the two wave plates 2 and 3 integrated with the spacer 5 with respect to the holder body 1 is regulated. The angle formed by the optical axis of the first wave plate 2 and the optical axis of the second wave plate 3 is 90 degrees.

  As shown in FIG. 5, it is formed over the entire circumference of the female screw 13 fixing member 4 on the inner wall of the holder body 1, but as compared with the screw ring portion 41 in which the male screw is formed as shown in FIG. What provided the base ring part 40 of a big outer diameter can also be used. The base ring portion 40 can be made equal to the outer diameter of the holder body in the finished product state, or can be shaped to protrude like a bowl depending on the receiving structure of the applied equipment to which this wave plate is applied. it can.

  This example prevents rotation of the wave plate with respect to the holder body, and even with the use of multiple wave plates, the optical axis can be accurately mounted on the holder body at a predetermined crossing angle without using adhesives or optical contacts. A wave plate unit having a simple structure can be provided.

  FIG. 7 is an exploded perspective view for explaining the configuration of the second embodiment of the wave plate unit according to the present invention. In the present embodiment, the present invention is applied to a compound zero order type wave plate unit similar to that in the first embodiment, and the same functions and the same components as those in FIG. 2 are denoted by the same reference numerals. This embodiment is different from the first embodiment described above in that the first wave plate 2 and the second wave plate 3 are bonded with an adhesive.

  A transparent adhesive suitable for epoxy resin is used for bonding the two wave plates 2 and 3. The two plates are bonded in advance by using a jig so that the optical axes of both wave plates are precisely crossed at 90 degrees, and an epoxy resin is injected between the two plates to be integrated. In FIG. 7, the second wave plate 3 is bonded to the front and the first wave plate 2 is bonded to the rear. A spacer 5 formed with a front collar 8 aligned and closely aligned with the orientation flat 10a formed on the first wave plate is applied from the rear, and the fixing member 4 is screwed into the holder body 1 and fixed in the same manner as in the first embodiment. .

  The front flange 8 provided on the spacer 5 may have a protruding amount sufficient to align and closely contact only the orientation flat 10a of the first wave plate 2. The first wave plate 2 and the second wave plate 3 may be replaced with each other in the unit axis direction, and integrated with the two wave plates bonded by protruding the hooks provided on the spacer 5 forward. Fixing to the holder body 1 is the same as in the first embodiment.

  Also according to the present embodiment, it is possible to provide a wave plate unit having a structure in which a rotation shift of the wave plate with respect to the holder main body is prevented and the optical axis can be accurately mounted on the holder main body at a predetermined crossing angle.

  FIG. 8 is an exploded perspective view for explaining the configuration of the wave plate unit according to the third embodiment of the present invention. In this embodiment, the present invention is applied to the same compound zero order type wave plate unit as in the first and second embodiments. The same function and the same components as those in FIGS. 2 and 7 are denoted by the same reference numerals. It is. This embodiment is different from the first and second embodiments described above in that the first wave plate 2 and the second wave plate 3 are bonded by so-called optical contact without using an adhesive. The optical contact is a high-precision flat surface on the opposing surfaces of the first wave plate 2 and the second wave plate 3, so that when they are bonded together, the bonded state is maintained firmly at atmospheric pressure. This is a joining method using no adhesive as in Example 2.

  In FIG. 8, the first wave plate 2 and the second wave plate 3 are integrated by optical contact. Similarly to the second embodiment, the optical contact is integrated by using a jig so that the optical axes of both wavelength plates are precisely crossed at 90 degrees and bonded together.

  A spacer 5 is combined behind the integrated first wave plate 2 and second wave plate 3. The spacer 5 is formed with a flange 9 aligned and intimately contacted with an orientation flat 10b provided on the second wave plate 3 from the rear side surface. The flange 9 is aligned and closely integrated with an orientation flat 10b provided on the second wave plate 3, and the fixing member 4 is screwed into the holder body 1 and fixed in the same manner as in the second embodiment.

  The flange 9 provided on the spacer 5 may be a protrusion amount sufficient to align and closely contact only the orientation flat 10b of the second wave plate 3. As in the second embodiment, the two wave plates are replaced by the first wave plate 2 and the second wave plate 3 in the unit axis direction, and the ribs provided on the spacer 5 are protruded forward and bonded together. It can also be integrated. Fixing to the holder body 1 is the same as in the second embodiment.

  Also according to the present embodiment, it is possible to provide a wave plate unit having a structure in which a rotation shift of the wave plate with respect to the holder main body is prevented and the optical axis can be accurately mounted on the holder main body at a predetermined crossing angle.

  The present invention is not limited to the above-described wave plate unit, but can be similarly applied to other optical devices that require special setting of the optical axis and similar electronic components that are required to suppress rotation displacement of built-in structural components.

  DESCRIPTION OF SYMBOLS 1 ... Holder main body, 2 ... 1st wave plate, 3 ... 2nd wave plate, 4 ... Fixing member, 40 ... Base ring part, 41 ... Screw ring part, 42 ... Driver tooth groove, 5 ... Spacer, 6 ... Convex part, 7 ... Concave part, 8 ... (Front) scissors, 9 ... (Back) scissors, 10 (10a, 10b) ) ... Orientation flat (orientation flat), 11 ... Axial groove, 12 ... Screw groove, 13 ... Female screw, 14 ... Male screw, 15 ... Inner flange (stopper), 100 ... Wave plate unit according to the present invention, 200 ... Conventional wave plate unit.

Claims (7)

A cylindrical holder body having a ring-shaped stopper made of an inner fringe at one end on the front side and a recess in a part of the inner wall, and the other end on the rear side being released, a disc-shaped wave plate, and the wavelength A ring-shaped spacer disposed on the rear side of the plate, and a ring-shaped fixing member provided on the rear side of the spacer,
The wave plate unit mounted inside the holder body and the wave plate unit fixed by pressing in the stopper direction with the ring-shaped fixing member from the rear side of the spacer,
The wave plate has an orientation flat indicating the optical axis direction of the wave plate at a part of the periphery of a thin plate made of a birefringent material,
The spacer is formed with a flange having a flat portion that is aligned and intimately contacted from the side edge with the orientation flat of the wave plate, and a convex portion that protrudes to the outer periphery and fits into the concave portion of the holder body,
The wave plate of the wave plate integrated with the spacer by fitting the convex portion into the concave portion of the holder body while integrating and aligning the flange of the spacer with the orientation flat of the wave plate A wave plate unit that regulates a position in a rotation direction. A cylindrical holder body having a ring-shaped stopper made of an inner fringe at one end that is the front and having a recess in a part of the inner wall and the other end being the rear is released, a disk-shaped first wave plate, A second wave plate, a ring-shaped spacer interposed between the first wave plate and the second wave plate, and a ring-shaped fixing member;
Inside the cylindrical holder body, the first wave plate is mounted on the front side, and the second wave plate is mounted in parallel on the rear side with the spacer interposed therebetween,
A wave plate unit in which the first wave plate and the second wave plate are pushed and fixed in the stopper direction into the holder body by the ring-shaped fixing member from the rear side of the second wave plate. There,
Each of the first wave plate and the second wave plate has an orientation flat indicating an optical axis direction of the wave plate at a part of a periphery of a thin plate made of a birefringent material having the same diameter,
The spacer includes a front ridge having a first flat portion aligned and closely in contact with the orientation flat of the first wave plate from a side edge, and the second wave plate on a side opposite to the first wave plate. A rear ridge having a second flat portion aligned and closely in contact with the orientation flat from the side edge of the wave plate, and a convex portion that protrudes to the outer periphery and fits into the concave portion of the holder body,
The front collar and the rear collar of the spacer are formed at a predetermined angle apart from each other,
The first edge of the spacer is aligned and closely aligned with the orientation flat of the first wave plate, and the rear edge of the spacer is aligned and closely aligned with the orientation flat of the second wave plate. An air gap is formed between the wave plate and the second wave plate to integrate the two wave plates, and the convex portion is integrated with the spacer by fitting into the concave portion of the holder body. A wave plate unit that regulates the rotational position of the two wave plates. In claim 2,
An angle formed by the optical axis of the first wave plate and the optical axis of the second wave plate is 90 degrees to constitute a compound zero order type wave plate. In any one of Claims 1 thru | or 3,
It has a female screw on the inner wall of the holder body, and has a male screw that engages with the female screw on the outer periphery of the fixing member,
The first wave plate mounted on the holder main body, the spacer, and the second wave plate are fixed to the stopper by fixing the male screw of the fixing member and the female screw of the holder main body. A wave plate unit, which is fixed by pressing between members. In any one of Claims 1 thru | or 4,
A wave plate unit comprising the wave plate made of a thin crystal plate. In any of claims 1 to 5,
A wave plate unit, characterized in that an axial groove for identifying the axial direction of the optical axis of the wave plate is provided on a part of the outer periphery of the holder body. In claim 5,
An X-cut or Y-cut quartz plate is used as the quartz thin plate.

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