JP2017122828A - Wavelength plate, polarization conversion element, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength plate having a high polarization conversion efficiency in a wide wavelength range, and high heat tolerance and light fastness.SOLUTION: A wavelength plate 20 includes: a first wavelength plate 21 having an optical axis azimuth angle θ1; a second wavelength plate 22 having an optical axis azimuth angle θ2, which is bonded to the first wavelength plate 21 at the light emitting side via a plasma polymerization film 201; a third wavelength plate 23 having an optical axis azimuth angle θ3, which is disposed at the light emitting side of the second wavelength plate 22 via a gap 20Gb; and a fourth wavelength plate 24 having an optical axis azimuth angle θ4, which is bonded to the third wavelength plate 23 at the light emitting side via a plasma polymerization film 202. The difference between θ1 and θ2 and the difference between θ3 and θ4 is 90° respectively, and the difference between θ2 and θ3 is 45°.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a wave plate, a polarization conversion element, and a projector.

Conventionally, a projector using a liquid crystal display element is known as a light modulation device that modulates light emitted from a light source. In this projector, light utilization efficiency is improved by aligning light having a random polarization state (random light) emitted from the light source with either the first linearly polarized light or the second linearly polarized light by the polarization conversion element. Things have been done.
The polarization conversion element includes a polarization beam splitter (PBS) prism that separates incident light into first linearly polarized light and second linearly polarized light, and one of the first linearly polarized light and the second linearly polarized light is the other. And a half-wave plate that converts to
Since the polarization conversion element becomes a high temperature at a portion where the light beam emitted from the light source is condensed, a projector (projection display device) configured to reduce deterioration of the polarization conversion element has been proposed (for example, Patent Document 1).

In the projector described in Patent Document 1, the half-wave plate is bonded to the PBS prism, and the polarization conversion element is displaced in a direction orthogonal to the polarization separation direction along the surface irradiated with the light of the polarization conversion element. A drive mechanism is provided.
The projector described in Patent Document 1 is configured such that the polarization concentration element is displaced by a driving mechanism and the luminance concentration portion is dispersed.

JP 2013-20222 A

  However, in the technique of Patent Document 1, although the luminance concentration portion is dispersed, it is considered insufficient to meet the recent demand for higher luminance of the light source. In order to project a high-quality image, the half-wave plate is desired to maintain a high polarization conversion efficiency in the visible light region. Not listed.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A wave plate according to this application example is bonded to a first wave plate having an optical axis azimuth angle of θ1 and a light emitting side of the first wave plate via a plasma polymerization film, and the optical axis azimuth angle is Is disposed with a gap on the light exit side of the second wave plate, the third wave plate having an optical axis azimuth angle of θ3, and the light exit side of the third wave plate. A fourth wave plate having an optical axis azimuth angle of θ4, bonded through a plasma polymerization film, and the difference between θ1 and θ2 and the difference between θ3 and θ4 are 90 °, The difference between θ2 and θ3 is 45 °.

According to this configuration, the first wavelength plate and the second wavelength plate, and the third wavelength plate and the fourth wavelength plate are formed so as to have a phase difference of 180 °, thereby allowing polarization conversion in a wide wavelength range. A half-wave plate with improved efficiency can be formed.
In addition, as described above, the wave plate is joined to the light incident side first wave plate and the second wave plate, and the light exit side third wave plate and the fourth wave plate by the plasma polymerization film, respectively. The heat resistance and light resistance can be improved as compared with bonding using an adhesive. In addition, by using four sheets having different optical axis azimuth angles, there is a risk of warping in different directions at high temperatures. However, since a gap is provided between the second wave plate and the third wave plate. Further, it is possible to suppress the peeling between the first wave plate and the second wave plate and the peeling between the third wave plate and the fourth wave plate, and to improve the heat dissipation due to the increased surface area.
Therefore, it is possible to provide a wavelength plate that has improved polarization conversion efficiency in a wide wavelength range and improved heat resistance and light resistance.

  Application Example 2 In the wave plate according to the application example, the first wave plate, the second wave plate, the third wave plate, and the fourth wave plate are formed of an inorganic crystal material. preferable.

  According to this configuration, since the first to fourth wave plates are formed of an inorganic crystal material such as quartz or sapphire, it is possible to provide a wave plate with further improved heat resistance and light resistance.

  Application Example 3 A polarization conversion element according to this application example has a light incident surface on which light is incident and a light emitting surface that emits light, and is sequentially joined to the light incident surface at a predetermined angle. A plurality of translucent substrates, a polarization separation film and a reflection film provided alternately between the plurality of translucent substrates, and the wave plate described above, The light incident from the light incident surface is separated into a first linearly polarized light and a second linearly polarized light, the first linearly polarized light is transmitted, and the second linearly polarized light is reflected. The second linearly polarized light reflected by the polarization separation film is reflected toward the light exit surface, and the wave plate converts one of the first linearly polarized light and the second linearly polarized light into the other. It is characterized by doing.

  According to this configuration, since the polarization conversion element includes the above-described wave plate, the polarization conversion element has high heat resistance and high light resistance, and the incident light is efficiently converted into the first linearly polarized light or the second light in a wide wavelength range. It becomes possible to emit the light in line with linearly polarized light.

  Application Example 4 In the polarization conversion element according to the application example described above, it is preferable that the first wavelength plate is disposed apart from the light exit surface.

  According to this configuration, in the polarization conversion element, a gap is provided between the first wave plate and the light exit surface in addition to the gap between the second wave plate and the third wave plate. As a result, the heat dissipation of the wave plate can be further increased, and thus a polarization conversion element with further improved heat resistance can be provided.

  Application Example 5 In the polarization conversion element according to the application example, it is preferable that the polarization separation film is bonded to the translucent substrate through a plasma polymerization film.

According to this configuration, since the polarization separation film through which light passes is joined to the translucent substrate via the plasma polymerization film, the polarization conversion element can further have high heat resistance and high light resistance.
Even if the polarization conversion element is configured such that the reflective film is bonded to the translucent substrate via an adhesive, the adhesive is not irradiated with light, and thus maintains high heat resistance and high light resistance. However, the manufacturing of the polarization conversion element can be simplified.

  Application Example 6 A projector according to this application example includes a light source, the polarization conversion element described above that converts light emitted from the light source into the first linearly polarized light or the second linearly polarized light, and the polarized light. A light modulation device that modulates light emitted from the conversion element, and a projection optical device that projects light modulated by the light modulation device are provided.

  According to this configuration, since the projector includes the polarization conversion element described above, it is possible to project an image with good image quality over a long period of time.

1 is a schematic diagram showing a schematic configuration of a projector according to an embodiment. Sectional drawing of the 2nd lens array and polarization conversion unit of this embodiment. The perspective view of the polarization conversion element of this embodiment. The perspective view for demonstrating the structure of the wavelength plate of this embodiment. The disassembled perspective view of the wave plate of this embodiment. The side view of the state which decomposed | disassembled the wave plate of this embodiment. The graph for demonstrating the conversion efficiency of the wavelength plate of this embodiment.

Hereinafter, the projector according to the present embodiment will be described with reference to the drawings.
The projector according to the present embodiment modulates light emitted from a light source according to image information, and enlarges and projects the modulated light onto a projection surface such as a screen. In the drawings shown below, the dimensions and ratios of the constituent elements are appropriately changed from the actual ones in order to make the constituent elements large enough to be recognized on the drawings.

[Main components of the projector]
FIG. 1 is a schematic diagram illustrating a schematic configuration of a projector 300 according to the present embodiment.
As shown in FIG. 1, the projector 300 includes an exterior housing 300 </ b> A that forms an exterior, an optical unit 3 that is accommodated in the exterior housing, and a control unit (not shown). Although not shown, a cooling device that cools the optical unit 3 and the like, a power supply device that supplies power to the control unit, and the like are further arranged in the exterior housing 300A.

  Although detailed description is omitted, the exterior casing 300A is composed of a plurality of members, and is provided with an intake port for taking in outside air, an exhaust port for exhausting warm air inside the exterior casing 300A to the outside, and the like. .

  The control unit includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like, and functions as a computer. The control unit is related to control of the operation of the projector 300, for example, image projection. Control and so on.

The optical unit 3 includes a light source device 30 and optically processes and projects the light beam emitted from the light source device 30 under the control of the control unit.
As shown in FIG. 1, in addition to the light source device 30, the optical unit 3 includes an integrator illumination optical system 31, a color separation optical system 32, a relay optical system 33, an electro-optical device 34, a projection lens 35 as a projection optical device, and An optical component housing 36 for arranging these optical components at predetermined positions on the optical path is provided.

  The light source device 30 includes a discharge-type light source 301 such as an ultra-high pressure mercury lamp or a metal halide lamp, a reflector 302, and the like. The light source device 30 reflects the light emitted from the light source 301 by the reflector 302 and emits the light toward the integrator illumination optical system 31.

The integrator illumination optical system 31 includes a first lens array 311, a second lens array 312, a polarization conversion unit 1, and a superimposing lens 314.
The first lens array 311 has a configuration in which small lenses are arranged in a matrix, and divides the light emitted from the light source device 30 into a plurality of partial lights. The second lens array 312 has substantially the same configuration as the first lens array 311, and partially superimposes the partial light on the surface of a liquid crystal panel 341 described later together with the superimposing lens 314.
The polarization conversion unit 1 includes a polarization conversion element 10 and aligns random light emitted from the second lens array 312 with linearly polarized light that can be used by the liquid crystal panel 341. The polarization conversion unit 1 will be described in detail later.

  The color separation optical system 32 includes two dichroic mirrors 321 and 322, and a reflection mirror 323. A light beam emitted from the integrator illumination optical system 31 is converted into red light (hereinafter referred to as “R light”) and green light (hereinafter referred to as “light”). G light ”) and blue light (hereinafter referred to as“ B light ”).

  The relay optical system 33 includes an incident side lens 331, a relay lens 333, and reflection mirrors 332 and 334, and has a function of guiding the R light separated by the color separation optical system 32 to the R light liquid crystal panel 341R. The optical unit 3 is configured such that the relay optical system 33 guides the R light, but is not limited thereto, and may be configured to guide the B light, for example.

The electro-optical device 34 is a transmissive liquid crystal panel 341 provided for each color light (the R light liquid crystal panel is 341R, the G light liquid crystal panel is 341G, and the B light liquid crystal panel is 341B), An incident side polarizing plate 342 disposed on the light incident side of each liquid crystal panel 341, an exit side polarizing plate 343 disposed on the light exit side of each liquid crystal panel 341, and a cross dichroic prism 344 as a color combining optical device are provided. Yes. The liquid crystal panel 341 corresponds to a light modulation device.
The liquid crystal panels 341R, 341G, and 341B modulate each color light emitted from the color separation optical system 32 based on the supplied image signal to form image light of each color.

The cross dichroic prism 344 has a substantially square shape in plan view in which four right-angle prisms are bonded together, and two dielectric multilayer films are formed on the interface where the right-angle prisms are bonded together. The cross dichroic prism 344 reflects the R light and the B light modulated by the liquid crystal panels 341R and 341B, and transmits the G light modulated by the liquid crystal panel 341G to synthesize three colors of image light.
The projection lens 35 includes a plurality of lenses (not shown), and enlarges and projects the light combined by the cross dichroic prism 344 on the screen.

[Polarization conversion unit]
Here, the polarization conversion unit 1 will be described in detail.
FIG. 2 is a cross-sectional view of the second lens array 312 and the polarization conversion unit 1.
As shown in FIG. 2, the polarization conversion unit 1 includes a polarization conversion element 10, a light shielding plate 19, and a holding frame (not shown).
FIG. 3 is a perspective view of the polarization conversion element 10.
As illustrated in FIGS. 2 and 3, the polarization conversion element 10 includes an element body 10 </ b> A, a wave plate 20, and double-sided adhesive materials 181 and 182.

The element body 10A is formed in a plate shape having a rectangular shape in plan view, and has a light incident surface 10i and a light emitting surface 10e that are parallel to each other.
The element body 10A includes a plurality of light-transmitting substrates 110 that are sequentially joined in a direction along the light emission surface 10e, and a polarization separation film 120 and a reflection film that are alternately provided between the plurality of light-transmitting substrates 110. 130, and is formed symmetrically across the center 10c in the direction in which the plurality of translucent substrates 110 are sequentially joined. Note that the direction of light emitted from the light source device 30 is defined as + Z direction, the direction in which the plurality of translucent substrates 110 are sequentially joined is defined as X direction, and the direction perpendicular to the Z direction and X direction is defined as Y direction.

The element body 10A includes a plate-shaped base material 111 having a polarization separation film 120 formed on one surface and a reflection film 130 formed on the other surface, and a polarization separation film 120 and a reflection film 130 formed thereon. The plate-shaped base materials 112 that are not formed are alternately joined, and the one formed by processing such as cutting is joined at the center 10c.
Specifically, the base material 111 is bonded to the base material 112 via a plasma polymerization film 150 to which the polarization separation film 120 is molecularly bonded, and the reflective film 130 is bonded to the base material 112 via an ultraviolet curable adhesive 160. Is done. The main material of the plasma polymerized film is polyorganosiloxane. The plasma polymerized film is formed by a plasma polymerization method and includes a siloxane bond, and includes a Si skeleton and a desorber composed of an organic group bonded to the Si skeleton. Then, by applying energy, the leaving group existing in the vicinity of the surface is released from the Si skeleton, thereby exhibiting adhesiveness.
And the some base material 111,112 joined alternately is cut | disconnected by a predetermined angle with respect to the end surface joined. As a result, the light incident surface 10i and the light emitting surface 10e are formed, and the cut base materials 111 and 112 have a predetermined angle (45 ° in this embodiment) at the end surfaces to be joined to the light emitting surface 10e. And formed as a translucent substrate 110. That is, the plurality of translucent substrates 110 are sequentially joined to the light incident surface 10i with a predetermined angle. Then, the polarization separation film 120 and the reflection film 130 are alternately disposed between the plurality of translucent substrates 110.

As shown in FIG. 2, the light shielding plate 19 is disposed between the second lens array 312 and the polarization conversion element 10, and is used effectively by the polarization conversion element 10 out of the light emitted from the second lens array 312. Shield light that is not being used. Specifically, the light shielding plate 19 is formed in a rectangular shape in plan view, and has an opening 191 in a region corresponding to a region where the polarization separation film 120 of the polarization conversion element 10 is provided when viewed from the light incident side. , The light traveling toward the region where the reflective film 130 is provided is blocked.
A holding frame (not shown) holds the periphery of the element body 10 </ b> A and the light shielding plate 19.

Random light emitted from the second lens array 312 and passing through the opening 191 of the light shielding plate 19 enters the polarization separation film 120 from the light incident surface 10 i of the polarization conversion element 10.
The polarization separation film 120 separates incident light into first linearly polarized light (P-polarized light) and second linearly polarized light (S-polarized light), transmits P-polarized light, and reflects S-polarized light.
The reflective film 130 reflects the S-polarized light reflected by the polarization separation film 120 toward the light exit surface 10e.

The wave plate 20 is disposed on the light exit surface 10e side of the polarization conversion element 10, and is provided in a region corresponding to the region in which the polarization separation film 120 is provided when viewed from the light exit side. As shown in FIG. 3, the wave plate 20 is formed in a strip shape in which the Y direction is longer than the X direction. The wave plate 20 functions as a half-wave plate, transmits the polarization separation film 120, and converts P-polarized light emitted from the light exit surface 10e into S-polarized light.
In this way, the polarization conversion element 10 emits the random light emitted from the second lens array 312 in alignment with the S-polarized light.

(Configuration of wave plate)
Here, the wavelength plate 20 will be described in detail.
FIG. 4 is a perspective view for explaining the configuration of the wave plate 20.
As shown in FIGS. 2 and 4, the wave plate 20 includes a first wave plate 21, a second wave plate 22, a third wave plate 23, and a fourth wave plate 24 that are sequentially arranged from the light exit surface 10 e side. Have. That is, the second wave plate 22 is disposed on the light emission side of the first wave plate 21, and the third wave plate 23 is disposed on the light emission side of the second wave plate 22. The fourth wave plate 24 is disposed on the light exit side of the third wave plate 23.

  The first wave plate 21 to the fourth wave plate 24 are formed of an inorganic crystal material, which is quartz in this embodiment. The first wave plate 21 and the second wave plate 22 are bonded via the plasma polymerization film 201, and the third wave plate 23 and the fourth wave plate 24 are bonded via the plasma polymerization film 202. Yes. The joined first wave plate 21 and second wave plate 22 are referred to as a first unit 20A, and the joined third wave plate 23 and fourth wave plate 24 are referred to as a second unit 20B.

As shown in FIG. 2, the wave plate 20 has a first unit 20A (first wave plate 21) separated from the light exit surface 10e, and a first unit 20A (second wave plate 22) and a second unit 20B (first wave plate). The three-wavelength plate 23) is spaced apart.
Specifically, as shown in FIG. 3, the first unit 20A is fixed to the element body 10A via double-sided adhesive materials 181 disposed at both ends in the Y direction of the light exit surface 10e. The second unit 20B is fixed to the element body 10A via both end portions of the first unit 20A in the Y direction and the double-sided adhesive material 182 laminated on the double-sided adhesive material 181. As a result, as shown in FIG. 2, the wave plate 20 is provided with a gap 20Ga between the first unit 20A (first wave plate 21) and the light exit surface 10e, and the first unit 20A and the second unit 20B. A gap 20Gb is provided between the first and second wave plates 22 and 23 (between the second wave plate 22 and the third wave plate 23).

FIG. 5 is an exploded perspective view of the wave plate 20. FIG. 6 is a side view of the state in which the wave plate 20 is disassembled.
The first wave plate 21 to the fourth wave plate 24 have different optical axis azimuth angles. The first wave plate 21 to the fourth wave plate 24 are converted to S-polarized light whose phase is shifted by 180 ° and whose polarization plane is rotated by 90 ° as a whole. , Optical axis azimuth, and phase difference are set. The optical axis azimuth is an angle formed between the crystal optical axis Ax and the polarization plane of S-polarized light incident on the wave plate 20.

Specifically, the first wave plate 21 to the fourth wave plate 24 are the difference between the optical axis azimuth angle θ1 of the first wave plate 21 and the optical axis azimuth angle θ2 of the second wave plate 22, and the third wave plate 23. The difference between the optical axis azimuth θ3 and the optical axis azimuth θ4 of the fourth wave plate 24 is 90 °, and the difference between the optical axis azimuth θ2 and the optical axis azimuth θ3 is 45 °. ing. For example, as shown in FIG. 5, θ1 = 22.5 °, θ2 = 112.5 °, θ3 = 67.5 °, and θ4 = 157.5 ° can be exemplified.
Further, the optical axis azimuth angles θ1, θ2, θ3, and θ4 are not limited to the angles described above, and may be the angles shown below. θ1 = 67.5 °, θ2 = 157.5 °, θ3 = 22.5 °, θ4 = 112.5 °, or θ1 = 157.5 °, θ2 = 67.5 °, θ3 = 112.5 ° , Θ4 = 22.5 °, or θ1 = 112.5 °, θ2 = 22.5 °, θ3 = 157.5 °, θ4 = 67.5 °. Further, the allowable tolerance of the optical axis azimuth angles θ1, θ2, θ3, and θ4 is about ± 2 ° with respect to the set angle.

  The first wave plate 21 to the fourth wave plate 24 are processed by a Y cut cut out at an angle parallel to the crystal optical axis Ax, that is, as shown in FIG. 6, the principal surface normal and the crystal optical axis Ax Is set to 90 °.

The thickness of the first wave plate 21 to the fourth wave plate 24 is set such that the phase difference Γ1 of the first unit 20A and the phase difference Γ2 of the second unit 20B satisfy 180 °.
The phase differences Γ1 and Γ2 with respect to light of wavelength λ are expressed by the following formulas (1) and (2).
[Equation 1]
Γ1 = 2π / λ × | ne-no | × | t1-t2 | (1)
[Equation 2]
Γ2 = 2π / λ × | ne-no | × | t3-t4 | (2)
Where ne: refractive index of extraordinary light, no: refractive index of ordinary light, t1: plate thickness of the first wave plate 21, t2: plate thickness of the second wave plate 22, t3: plate thickness of the third wave plate 23 , T4: The thickness of the fourth wave plate 24 is set.

From the expressions (1) and (2), | t1-t2 | and | t3-t4 | are derived by the following expressions.
[Equation 3]
| T1-t2 | = λ / (2 × | ne-no |) (3)
[Equation 4]
| T3-t4 | = λ / (2 × | ne-no |) (4)

The wave plate 20 is required to have high polarization conversion efficiency in the region where the wavelength is about 400 nm to about 700 nm in order for the projector 300 to project a high quality image. Therefore, 520 nm light (G light) was used as the wavelength λ, and t1, t2, t3, and t4 were determined so as to satisfy the expressions (3) and (4).
As a result, for example, t1 = t3 = 0.8221 mm and t2 = t4 = 0.3103 mm were obtained. Moreover, as long as the expressions (3) and (4) are satisfied, t1 ≠ t3 and t2 ≠ t4 may be satisfied, and t1> t2 and t3> t4 may be satisfied. Also, the allowable tolerance for the set values of | t1-t2 | and | t3-t4 | is about ± 5%.

  FIG. 7 is a graph for explaining the conversion efficiency of the wave plate 20 with respect to the wavelength, and is a graph compared with the characteristics of the wave plate composed of two quartz plates of the prior art. Specifically, FIG. 7 is a graph showing a simulation result of conversion efficiency for wavelengths of 400 nm to 700 nm when the incident angle is changed to 0 ° and 5 °.

As shown in FIG. 7, in the conventional wave plate, the polarization conversion efficiency is approximately 100% at a wavelength of 520 nm, but the polarization conversion efficiency decreases as the distance from the wavelength 520 nm increases, and the wavelength conversion is about 73% at a wavelength of 400 nm. At 700 nm, it is about 83%.
On the other hand, in the wave plate 20 of this embodiment, the wavelength is about 100% in the region of about 460 nm to about 600 nm, about 93% at the wavelength of 400 nm, about 97% at the wavelength of 700 nm, and the polarization conversion efficiency in a wide wavelength region. Is expensive.
The first wave plate 21 to the fourth wave plate 24 may be artificial quartz crystal or natural quartz crystal, and as long as it is an inorganic crystal material, for example, sapphire or the like can be used.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Since the wave plate 20 is composed of the first wave plate 21 to the fourth wave plate 24 described above, it is possible to form a half wave plate with improved polarization conversion efficiency in a wide wavelength range. It becomes.
Further, the wave plate 20 has a first wave plate 21 and a second wave plate 22, and a third wave plate 23 and a fourth wave plate 24, which are bonded by a plasma polymerized film, respectively. , Heat resistance and light resistance can be enhanced. Further, by using four sheets having different optical axis azimuth angles, there is a risk of warping in different directions at high temperatures, but a gap 20Gb is provided between the second wave plate 22 and the third wave plate 23. Therefore, it is possible to suppress the peeling between the first wave plate 21 and the second wave plate 22 and the peeling between the third wave plate 23 and the fourth wave plate 24, and to improve the heat dissipation by increasing the surface area. .
Therefore, it is possible to provide the wavelength plate 20 with improved polarization conversion efficiency in a wide wavelength range and improved heat resistance and light resistance.

  (2) Since the first wave plate 21 to the fourth wave plate 24 are formed of an inorganic crystal material, it is possible to provide the wave plate 20 with further improved heat resistance and light resistance.

  (3) Since the polarization conversion element 10 includes the wave plate 20 described above, the polarization conversion element 10 has high heat resistance and high light resistance, and can efficiently emit incident light aligned with S-polarized light in a wide wavelength range. Become.

  (4) In the polarization conversion element 10, a gap 20 Ga is provided between the first wave plate 21 and the light exit surface 10 e in addition to the gap between the second wave plate 22 and the third wave plate 23. Thereby, since the heat dissipation of the wave plate 20 can be further increased, it is possible to provide the polarization conversion element 10 with further improved heat resistance.

(5) Since the polarization separation film 120 through which light passes is joined to the translucent substrate 110 via the plasma polymerization film 150, the polarization conversion element 10 can further have high heat resistance and high light resistance. .
Moreover, although the reflective film 130 is joined to the translucent base material 110 through the adhesive material 160 in the polarization conversion element 10, since this adhesive material 160 is not irradiated with light, it has high heat resistance and high light resistance. The manufacturing can be simplified while maintaining the above.

  (6) Since the projector 300 includes the polarization conversion element 10 described above, it is possible to project an image with good image quality over a long period of time.

  (7) Since the first wave plate 21 to the fourth wave plate 24 have a cutting angle β of 90 °, when the artificial crystal or the like is used as a base material, a larger number of sheets are obtained from one base material. This makes it possible to simplify the production of the wave plate 20 and reduce the cost.

(Modification)
In addition, you may change the said embodiment as follows.
In the wave plate 20 of the above-described embodiment, the first unit 20A (first wave plate 21) is disposed away from the light emission surface 10e. However, the first wave plate 21 is disposed on the light emission surface via a plasma polymerization film. You may comprise so that it may join to 10e.

  The wave plate 20 of the embodiment is disposed in a region corresponding to the region where the polarization separation film 120 is provided, and converts the P-polarized light as the first linearly polarized light into the S-polarized light as the second linearly polarized light. However, the wave plate 20 is disposed in a region corresponding to the region where the reflective film 130 is provided, and S-polarized light as the second linearly polarized light is converted into P-polarized light as the first linearly polarized light. You may comprise as follows.

  The projector 300 according to the embodiment uses the transmissive liquid crystal panel 341 as a light modulation device, but may use a reflective liquid crystal panel.

  The light source 301 is not limited to a discharge lamp, but may be a solid light source such as a lamp of another type, a light emitting diode, or a laser.

  DESCRIPTION OF SYMBOLS 1 ... Polarization conversion unit, 10 ... Polarization conversion element, 10e ... Light emission surface, 10i ... Light incident surface, 20 ... Wave plate, 20Gb ... Gap, 21 ... 1st wave plate, 22 ... 2nd wave plate, 23 ... 1st 3 wavelength plate, 24 ... 4th wavelength plate, 35 ... projection lens (projection optical device), 110 ... translucent substrate, 120 ... polarization separation film, 130 ... reflection film, 150, 201, 202 ... plasma polymerization film, 160: Adhesive material, 181, 182: Double-sided adhesive material, 300: Projector, 301: Light source, 341, 341B, 341G, 341R ... Liquid crystal panel (light modulation device), θ1, θ2, θ3, θ4: Optical axis azimuth.

Claims (6)

A first wave plate having an optical axis azimuth angle of θ1,
A second wave plate having an optical axis azimuth of θ2 bonded to the light emitting side of the first wave plate through a plasma polymerization film;
A third wave plate having a gap on the light exit side of the second wave plate and having an optical axis azimuth of θ3;
A fourth wave plate having an optical axis azimuth of θ4, which is bonded to the light emitting side of the third wave plate through a plasma polymerization film;
With
The wave plate according to claim 1, wherein a difference between the θ1 and the θ2, and a difference between the θ3 and the θ4 is 90 °, and a difference between the θ2 and the θ3 is 45 °. The wave plate according to claim 1,
The first wave plate, the second wave plate, the third wave plate, and the fourth wave plate are made of an inorganic crystal material. A plurality of light-transmitting substrates having a light incident surface on which light is incident and a light emitting surface that emits light, and sequentially joined to the light incident surface at a predetermined angle;
Polarization separation films and reflection films alternately provided between the plurality of translucent substrates,
The wave plate according to claim 1 or 2,
With
The polarization separation film separates light incident from the light incident surface into a first linearly polarized light and a second linearly polarized light, transmits the first linearly polarized light, and reflects the second linearly polarized light. And
The reflective film reflects the second linearly polarized light reflected by the polarization separation film toward the light exit surface,
The wavelength conversion plate according to claim 1, wherein the wave plate converts one of the first linearly polarized light and the second linearly polarized light into the other. The polarization conversion element according to claim 3,
The polarization conversion element, wherein the first wave plate is disposed apart from the light exit surface. The polarization conversion element according to claim 3 or 4, wherein
The polarization conversion element, wherein the polarization separation film is bonded to the translucent substrate through a plasma polymerization film. A light source;
The polarization conversion element according to any one of claims 3 to 5, which converts light emitted from the light source into the first linearly polarized light or the second linearly polarized light.
A light modulation device for modulating light emitted from the polarization conversion element;
A projection optical device for projecting light modulated by the light modulation device;
A projector comprising:

Images