JP2017116602A - Phase difference control device, illumination device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference control device capable of widening an allowable range with respect to thickness accuracy of a retardation plate.SOLUTION: A phase difference control device 80 of the present invention comprises: a retardation plate 81 having a first surface and an optical axis tilted with respect to the first surface; and a retardation plate rotation mechanism 82 rotating the retardation plate 81 about a rotation axis intersecting with a normal line of the first surface and with the optical axis.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a phase difference control device, an illumination device, and a projector.

  In recent years, an illumination device using a rotating fluorescent plate has been proposed as an illumination device for a projector. The rotating fluorescent plate rotates the substrate on which the phosphor layer is provided, irradiates the phosphor layer on the substrate with excitation light to generate fluorescence, and generates illumination light including fluorescence.

  Patent Document 1 listed below includes a light source device including a solid-state light source unit including a semiconductor laser, a dichroic mirror, a fluorescent light-emitting plate, a first retardation plate, a reflecting plate, and a second retardation plate. It is disclosed. In this light source device, blue light emitted from the semiconductor laser is separated into a first polarization component and a second polarization component by a dichroic mirror. The light of the first polarization component is irradiated onto the fluorescent light emitting plate, and emits green and red fluorescence. The polarized light of the second polarization component is converted into circularly polarized light by the first retardation plate, is further reflected by the reflection plate, and is incident again on the first retardation plate. The second retardation plate is disposed between the solid light source unit and the dichroic mirror, and controls the ratio of the P-polarized component and the S-polarized component of the light incident on the dichroic mirror.

JP 2012-137744 A

  In a light source device that emits a phosphor using laser light as excitation light, a retardation plate that controls the polarization state of the laser light needs to be able to withstand high-power laser light. Therefore, this type of retardation plate may be made of an inorganic material such as quartz. However, when the retardation plate is made of an inorganic material such as quartz, the change in the polarization state is determined by the thickness of the retardation plate. Therefore, in order to appropriately control the amount of light incident on the phosphor, It was necessary to increase the accuracy of the thickness.

  One aspect of the present invention has been made to solve the above-described problem, and an object of the present invention is to provide a phase difference control device capable of widening the allowable range for the accuracy of the thickness of the phase difference plate. One. One aspect of the present invention is to provide an illumination device including the above-described phase difference control device. An object of one embodiment of the present invention is to provide a projector including the above-described lighting device.

  In order to achieve the above object, a phase difference control device according to one aspect of the present invention includes a phase difference plate having a first surface and an optical axis inclined with respect to the first surface, and the first phase difference plate. A retardation plate rotating mechanism for rotating the retardation plate around a rotation axis intersecting the surface normal of the surface and the optical axis.

  In the phase difference control device according to one aspect of the present invention, the phase difference plate having the optical axis inclined with respect to the first surface is converted into the surface normal of the first surface and the optical axis by the phase difference plate rotation mechanism. By rotating around the intersecting rotation axes, the phase difference can be adjusted over a wide range. Thereby, the tolerance | permissible_range with respect to the precision of the thickness of a phase difference plate can be expanded.

In the phase difference control device according to one aspect of the present invention, the rotation axis may be orthogonal to a plane including the orthogonal projection of the optical axis onto the first surface and the optical axis.
According to this configuration, the change in the phase difference with respect to the rotation angle of the phase difference plate can be increased, and the phase difference can be adjusted in a wider range.

In the phase difference control device according to one aspect of the present invention, the phase difference plate rotation mechanism may be configured such that two arrangement directions in which the tilt directions of the optical axis with respect to the first surface are opposite to each other are possible. Good.
According to this configuration, even if the angle range in which the phase difference plate can be rotated is, for example, 5 °, the phase difference can be substantially adjusted within an angle range of ± 5 °. Thereby, space saving of a phase difference control apparatus can be achieved.

  The illumination device according to one aspect of the present invention includes a light emitting element that emits a light bundle, the phase difference control device according to one aspect of the present invention into which the light bundle is incident, and the light beam that has passed through the phase difference control device. Is separated into a first light bundle in the first polarization state and a second light bundle in the second polarization state, and a wavelength at which fluorescence is emitted when the first light bundle is irradiated. A conversion element.

  Since the lighting device according to one aspect of the present invention includes the phase difference control device according to one aspect of the present invention, an inexpensive phase difference plate can be used, and cost can be reduced.

  A projector according to an aspect of the present invention includes a lighting device according to one aspect of the present invention, a light modulation device that modulates light emitted from the lighting device in accordance with image information, and the light modulation device. A projection optical system for projecting light.

  Since the projector according to one aspect of the present invention includes the lighting device according to one aspect of the present invention, the cost can be reduced.

It is a schematic block diagram of the projector of one Embodiment of this invention. It is a schematic block diagram of the illuminating device of one Embodiment of this invention. It is a top view of the 1st phase difference plate of one embodiment of the present invention. It is sectional drawing which follows the A'-A line of FIG. It is a top view of the phase difference control apparatus containing the phase difference plate of the state in which the inclination direction of the optical axis faced the 1st direction. It is a top view of the phase difference control apparatus containing the phase difference plate of the state in which the inclination direction of the optical axis faced the 2nd direction opposite to the 1st direction. It is a graph which shows the relationship between the thickness of the phase difference plate of the comparative example whose optical axis is parallel to the 1st surface, and the incident light quantity to a fluorescent substance. It is a graph which shows the relationship between the thickness of the phase difference plate of this embodiment in which the optical axis is inclined with respect to the 1st surface, and the incident light quantity to a fluorescent substance. It is a graph which shows the relationship between the rotation angle of the phase difference plate of this embodiment in which the optical axis is inclined with respect to the 1st surface, and the incident light quantity to a fluorescent substance.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In the following drawings, in order to make each component easy to see, the scale of the size may be varied depending on the component.

The projector according to the present embodiment is an example of a projector using three transmissive liquid crystal light valves.
FIG. 1 is a schematic configuration diagram illustrating a projector according to the present embodiment. FIG. 2 is a schematic configuration diagram showing the illumination device of the present embodiment.
As shown in FIG. 1, the projector 1 of this embodiment is a projection type image display device that displays a color image on a screen SCR. The projector 1 includes an illumination device 70, a uniform illumination optical system 40, a color separation optical system 3, a light modulation device 4R for red light, a light modulation device 4G for green light, and a light modulation device 4B for blue light. The synthesizing optical system 5 and the projection optical system 60 are roughly provided.

  The illumination device 70 emits white illumination light WL toward the uniform illumination optical system 40. The illuminating device 70 includes the light source device of the present invention described later.

The uniform illumination optical system 40 includes a homogenizer optical system 31, a polarization conversion element 32, and a superimposing optical system 33.
The homogenizer optical system 31 includes a first multi-lens array 31a and a second multi-lens array 31b.

  The uniform illumination optical system 40 uniformizes the intensity distribution of the illumination light WL emitted from the illumination device 70 in the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, which are illuminated areas. The illumination light WL emitted from the uniform illumination optical system 40 enters the color separation optical system 3.

  The color separation optical system 3 separates the illumination light WL emitted from the illumination device 70 into red light LR, green light LG, and blue light LB. The color separation optical system 3 includes a first dichroic mirror 7a, a second dichroic mirror 7b, a first reflection mirror 8a, a second reflection mirror 8b, a third reflection mirror 8c, and a first A relay lens 9a and a second relay lens 9b are provided.

The first dichroic mirror 7a separates the illumination light WL emitted from the illumination device 70 into red light LR and light including green light LG and blue light LB. The first dichroic mirror 7a transmits the red light LR and reflects the green light LG and the blue light LB.
The second dichroic mirror 7b separates the light reflected by the first dichroic mirror 7a into green light LG and blue light LB. The second dichroic mirror 7b reflects the green light LG and transmits the blue light LB.

  The first reflection mirror 8a is disposed in the optical path of the red light LR. The first reflection mirror 8a reflects the red light LR transmitted through the first dichroic mirror 7a toward the light modulation device 4R. The second reflection mirror 8b and the third reflection mirror 8c are arranged in the optical path of the blue light LB. The second reflection mirror 8b and the third reflection mirror 8c guide the blue light LB transmitted through the second dichroic mirror 7b to the light modulation device 4B. The green light LG is reflected by the second dichroic mirror 7b and travels toward the light modulation device 4G.

  The first relay lens 9a and the second relay lens 9b are disposed on the light emission side of the second dichroic mirror 7b in the optical path of the blue light LB. The first relay lens 9a and the second relay lens 9b compensate for the optical loss of the blue light LB caused by the optical path length of the blue light LB being longer than the optical path lengths of the red light LR and the green light LG. .

  The light modulation device 4R modulates the red light LR according to the image information, and forms image light corresponding to the red light LR. The light modulation device 4G modulates the green light LG according to the image information, and forms image light corresponding to the green light LG. The light modulation device 4B modulates the blue light LB according to the image information, and forms image light corresponding to the blue light LB.

  For example, a transmissive liquid crystal panel is used for the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. Polarizers (not shown) are respectively arranged on the incident side and the emission side of the liquid crystal panel. The polarizing plate transmits linearly polarized light having a specific polarization direction.

  A field lens 10R is disposed on the incident side of the light modulation device 4R. A field lens 10G is disposed on the incident side of the light modulation device 4G. A field lens 10B is disposed on the incident side of the light modulation device 4B. The field lens 10R collimates the red light LR incident on the light modulation device 4R. The field lens 10G collimates the green light LG incident on the light modulation device 4G. The field lens 10B collimates the blue light LB incident on the light modulation device 4B.

  The combining optical system 5 combines the image light corresponding to each of the red light LR, the green light LG, and the blue light LB, and emits the combined image light toward the projection optical system 60. For example, a cross dichroic prism is used for the combining optical system 5.

  The projection optical system 60 includes a projection lens group including a plurality of projection lenses. The projection optical system 60 enlarges and projects the image light combined by the combining optical system 5 toward the screen SCR. As a result, an enlarged color image is displayed on the screen SCR.

Hereinafter, the illumination device 70 will be described.
As shown in FIG. 2, the illumination device 70 includes a light source device 71, a collimator optical system 72, an afocal optical system 23, a homogenizer optical system 25, a phase difference control device 80, a polarization beam splitter 27, A first pickup optical system 28, a phosphor wheel 29 provided with a phosphor layer, a second retardation plate 36, a second pickup optical system 41, and a rotary diffusing element 42 are provided. Hereinafter, the polarizing beam splitter is abbreviated as PBS.
The PBS 27 of the present embodiment corresponds to the polarization separation element of the claims.

  Light source device 71, collimator optical system 72, afocal optical system 23, homogenizer optical system 25, first phase difference plate 81, PBS 27, second phase difference plate 36, and second pickup The optical system 41 is disposed on the optical axis AX0. The first pickup optical system 28 is disposed on the optical axis AX1 orthogonal to the optical axis AX0.

The light source device 71 includes, for example, a plurality of semiconductor lasers 73 arranged in an array. However, the number and arrangement of the semiconductor lasers 73 are not particularly limited. The semiconductor laser 73 emits a blue light beam BL, for example. The light source device 71 emits a light bundle K1 composed of a plurality of light beams BL emitted from a plurality of semiconductor lasers 73.
The semiconductor laser 73 of the present embodiment corresponds to the light emitting element of the claims.

  The collimator optical system 72 includes a plurality of collimator lenses 74 provided corresponding to each of the plurality of semiconductor lasers 73. The collimator lens 74 converts the light beam BL emitted from the semiconductor laser 73 into a parallel light beam.

  The afocal optical system 23 includes a convex lens 23a and a concave lens 23b. The afocal optical system 23 reduces the light beam K1 emitted from the collimator optical system 72.

  The homogenizer optical system 25 includes a first multi-lens array 25a and a second multi-lens array 25b. The first multi-lens array 25a has a plurality of lenses 25am arranged at an equal pitch. The second multi-lens array 25b has a plurality of lenses 25bm arranged at the same pitch as the lens 25am. The homogenizer optical system 25 makes the intensity distribution of the light beam K1s emitted from the afocal optical system 23 uniform in the illuminated area.

  The phase difference control device 80 generally includes a first phase difference plate 81 and a phase difference plate rotation mechanism 82 for rotating the first phase difference plate 81. The first retardation plate 81 is made of an inorganic material such as quartz, sapphire, or calcite. By rotating the first retardation plate 81 by the retardation plate rotating mechanism 82, the light transmitted through the first retardation plate 81 includes the S polarization component and the P polarization component with respect to the PBS 27 at a predetermined ratio. It can be. The detailed configuration of the phase difference control device 80 will be described later.

  The PBS 27 is disposed at an angle of 45 ° with respect to the optical axis AX0 and the optical axis AX1. The PBS 27 reflects the light of the S polarization component and transmits the light of the P polarization component. The light of the S polarization component is reflected by the PBS 27 and travels toward the phosphor wheel 29. The P-polarized component light passes through the PBS 27 and travels toward the rotary diffusion element 42.

  The S-polarized light beam BLs emitted from the PBS 27 is incident on the first pickup optical system 28. The first pickup optical system 28 collects the light beam BLs toward the phosphor layer 47 on the phosphor wheel 29. The first pickup optical system 28 includes, for example, a first pickup lens 28a and a second pickup lens 28b.

The light emitted from the first pickup optical system 28 enters the phosphor wheel 29. The phosphor wheel 29 is a reflection-type rotating fluorescent plate, and is provided between the phosphor layer 47 that emits fluorescence, a rotating plate 49 that supports the phosphor layer 47, and the phosphor layer 47 and the rotating plate 49. A reflection film (not shown) that reflects the fluorescent light and a drive motor 50 that drives the rotating plate 49 are included. As the rotating plate 49, for example, a disc is used, but the shape of the rotating plate 49 is not limited to a disc, and may be a flat plate.
The phosphor layer 47 of the present embodiment corresponds to the wavelength conversion element in the claims.

  The phosphor layer 47 includes phosphor particles that absorb blue excitation light, convert it into yellow fluorescence, and emit it. As the phosphor particles, for example, YAG (yttrium / aluminum / garnet) phosphors can be used. In addition, the material for forming the phosphor particles may be one kind, or a mixture of particles formed using two or more kinds of materials may be used as the phosphor particles.

  The P-polarized light beam BLp emitted from the PBS 27 is incident on the second retardation plate 36. The second retardation plate 36 is, for example, a quarter wavelength plate. The P-polarized light beam BLp is converted into a circularly-polarized light beam by passing through the second retardation film 36. The light beam BLp that has passed through the second phase difference plate 36 enters the second pickup optical system 41. The second pickup optical system 41 condenses incident light toward the rotary diffusing element 42. The second pickup optical system 41 includes, for example, a first pickup lens 41a and a second pickup lens 41b.

  The rotary diffusing element 42 includes a diffusive reflection plate 52 and a drive motor 53 for rotating the diffusive reflection plate 52. The diffuse reflector 52 diffusely reflects the circularly polarized light beam BLp emitted from the second pickup optical system 41 toward the PBS 27. The diffusive reflector 52 preferably reflects the light beam BLp by Lambertian reflection. The rotation axis of the drive motor 50 is disposed substantially parallel to the optical axis AX0. Thereby, the diffuse reflection plate 52 can be rotated in a plane intersecting the optical axis of the light incident on the diffuse reflection plate 52. The diffuse reflection plate 52 is formed, for example, in a circular shape when viewed from the direction of the rotation axis, but the shape of the diffuse reflection plate 52 is not limited to a circular plate, and may be a flat plate.

The circularly polarized light beam BLp reflected by the diffusive reflecting plate 52 and transmitted again through the second pickup optical system 41 is transmitted through the second retardation plate 36 again and converted to an S-polarized light beam BLs2.
The yellow fluorescent light emitted from the phosphor layer 47 and the light beam BLs2 (blue light) from the rotary diffusing element 42 are combined by the PBS 27 to become white illumination light WL. The illumination light WL is incident on the uniform illumination optical system 40 shown in FIG.

FIG. 3 is a plan view of the first retardation plate 81 of the present embodiment. 4 is a cross-sectional view taken along line A′-A in FIG. 3. 5 and 6 are plan views of the phase difference control device 80 including the first phase difference plate 81 shown in FIGS. 3 and 4.
As shown in FIGS. 5 and 6, the phase difference control device 80 includes a first phase difference plate 81, a rotation shaft 83, and a phase difference plate that rotates the first phase difference plate 81 about the rotation shaft 83. A rotation mechanism 82 and an adjustment knob 84 for the user to rotate the first phase difference plate 81 are provided. In the case of this embodiment, the first retardation plate 81 is accommodated in a rectangular annular frame 85. However, the first retardation plate 81 is not necessarily accommodated in the frame 85.

  As shown in FIGS. 3 and 4, the first retardation film 81 includes a first surface 81a (upper surface in FIG. 4), a second surface 81b (lower surface in FIG. 4), and a first surface 81a. And an optical axis D1 tilted with respect to. The first retardation plate 81 is a flat plate in which the first surface 81a and the second surface 81b are parallel to each other. The planar shape of the first retardation plate 81 viewed from the normal direction of the first surface 81a is a rectangular shape having a long side and a short side.

  An arrow D2 in FIG. 3 indicates an orthogonal projection of the optical axis D1 onto the first surface 81a. As shown in FIG. 3, in the case of the present embodiment, the orthogonal projection D2 of the optical axis D1 onto the first surface and the short side of the first retardation plate 81 when viewed from the normal direction of the first surface 81a. An angle φ formed with the straight line L parallel to the angle is, for example, 34 °. Hereinafter, an angle φ formed by the orthogonal projection D2 and the straight line L is defined as an azimuth angle φ of the optical axis D1. The polarization direction of the light beam BL is parallel to the short side of the first retardation plate 81. Therefore, the angle formed by the orthogonal projection D2 and the polarization direction of the light beam BL is also 34 °.

As shown in FIG. 4, the angle θ between the optical axis D1 and the first surface 81a is, for example, 45 °. Hereinafter, an angle θ formed by the optical axis D1 and the first surface 81a is defined as an inclination angle of the optical axis D1.
The numerical values of the azimuth angle φ and the inclination angle θ of the optical axis D1 in the present embodiment are numerical values aiming to guide 80% of the components of the light beam BL incident on the PBS 27 to the phosphor wheel 29 side. It can be changed.

  The phase difference plate rotation mechanism 82 rotates the first phase difference plate 81 around a rotation axis 83 that intersects the surface normal of the first surface 81a and the optical axis D1. The rotation shaft 83 is orthogonal to a plane (cross section hatched in FIG. 4) including the orthogonal projection D2 and the optical axis D1. When the position where the first surface 81a is orthogonal to the optical axis AX0 (see FIG. 2) is defined as the reference position of the first retardation plate 81 (the position indicated by the solid line in FIG. 4), the first retardation plate 81 is defined. The rotation angle ω when is at the reference position is defined as 0 °.

  The retardation plate rotating mechanism 82 only needs to rotate the first retardation plate 81 together with the frame 85 within a predetermined rotation angle range. The specific configuration of the retardation plate rotating mechanism 82 is not particularly limited, and the rotation angle is not particularly limited.

  As shown in FIG. 5 and FIG. 6, the retardation plate rotating mechanism 82 allows the first retardation plate 81 to be arranged in two directions in which the inclination directions of the optical axis D1 with respect to the first surface 81a are opposite to each other. It is configured. That is, the phase difference plate rotating mechanism 82 can rotate the first phase difference plate 81 within a range of a predetermined rotation angle, and the first phase difference plate 81 is turned over with respect to the frame 85. It is possible to install it by inverting it. 5 and 6 show a state in which the first retardation plate 81 is inverted with respect to each other.

Hereinafter, the operation and effect of the phase difference control device 80 will be described.
For example, it is assumed that the light beam BL emitted from the semiconductor laser 73 is P-polarized light with respect to the PBS 27. The light beam BL is converted into light in which 80% S-polarized component and 20% P-polarized component are mixed by the phase difference control device 80 including the first phase difference plate 81, and the 80% S-polarized component is converted into PBS27. Let us consider a case in which the light is reflected by and led to the phosphor layer 47.

As a comparative example, a phase difference control device including a phase difference plate having an optical axis parallel to the first surface, and a rotation mechanism that rotates the phase difference plate around a rotation axis perpendicular to the first surface. Suppose.
FIG. 7 shows the relationship between the thickness of the phase difference plate and the amount of light incident on the phosphor in the phase difference control device of the comparative example. In FIG. 7, the horizontal axis of the graph represents the thickness [mm] of the retardation plate. The vertical axis of the graph represents the light amount LA [arbitrary unit] of the light beam BLs incident on the phosphor. The light amount LA corresponds to the ratio [%] of the incident light amount to the phosphor with respect to the incident light amount to the PBS. In this case, the optical axis of the retardation plate is parallel to the first surface and forms an angle of 45 ° with respect to the polarization direction of the light incident on the retardation plate.

  As shown in FIG. 7, the light amount LA tends to increase by increasing the thickness of the retardation plate. Therefore, the light amount LA can be controlled by adjusting the thickness of the retardation plate. In this example, it is assumed that the amount of light LA80 corresponding to the ratio of the amount of light incident on the phosphor of 80% is obtained when the thickness of the phase difference plate is 0.308 mm.

  In the range where the thickness of the retardation plate is between 0.308 and 0.322 mm, the light amount LA exceeds the light amount LA80. In this range, the light amount LA can be reduced to the light amount LA80 by rotating the phase difference plate using the rotation mechanism and shifting the angle formed by the optical axis of the phase difference plate and the polarization direction of the incident light from 45 °. it can. Therefore, in order to change the light amount LA to the light amount LA80, the thickness of the retardation plate needs to be 0.308 to 0.322 mm, that is, 0.315 ± 0.007 mm. Thus, in the phase difference control device of the comparative example, since it is necessary to increase the accuracy of the thickness of the phase difference plate, there is a problem that the manufacturing cost of the phase difference plate is increased.

  The phase difference control device 80 of the present embodiment includes a first phase difference plate 81 having an optical axis D1 inclined by 45 ° with respect to the first surface 81a. FIG. 8 shows the relationship between the thickness of the first retardation plate 81 and the light amount LA in the phase difference control device 80 of the present embodiment. In FIG. 8, the horizontal axis of the graph is the thickness [mm] of the first retardation plate 81. The vertical axis of the graph represents the light amount LA [arbitrary unit] of the light beam BLs incident on the phosphor. As shown in FIG. 3, the azimuth angle φ of the optical axis D1 of the first retardation plate 81 is 34 °, and the angle formed between the orthogonal projection D2 and the polarization direction of the light beam BL is 34 °.

  Although the absolute value of the ratio of the amount of light incident on the phosphor is different from that of the comparative example of FIG. 7, the amount of light LA tends to increase as the thickness of the first retardation plate 81 is increased as shown in FIG. Indicates. By setting the thickness of the first retardation plate 81 to about 0.53 to 0.54 mm, the light amount LA can be set to approximately the light amount LA80. Further, in the case of the present embodiment, since the first retardation plate 81 is configured to be rotatable about the rotation shaft 83, the thickness of the first retardation plate 81 is such that the light amount LA does not reach the light amount LA80. Even in this case, the light amount LA can be adjusted to approximately the light amount LA80 by changing the rotation angle ω of the first retardation plate 81.

  FIG. 9 shows the relationship between the rotation angle ω of the first retardation plate 81 and the light amount LA. In FIG. 9, the horizontal axis of the graph represents the rotation angle [°] of the first retardation plate 81. The vertical axis of the graph represents the light amount LA [arbitrary unit] of the light beam BLs incident on the phosphor. In FIG. 9, the thickness of the first retardation plate 81 is 0.487 mm.

  As shown in FIG. 9, when the rotation angle of the first retardation plate 81 is increased from 0 °, the light amount LA tends to increase. By adjusting the rotation angle of the first retardation plate 81 to about 5 °, the light amount LA can be made substantially equal to the light amount LA80. Thus, even when the thickness of the first retardation plate 81 is such that the ratio of the amount of incident light to the phosphor is less than 80%, the rotation angle of the first retardation plate 81 is adjusted. Thus, the ratio of the amount of light incident on the phosphor can be adjusted to 80%. Even when the thickness of the first retardation plate 81 is such that the ratio of the amount of incident light to the phosphor is greater than 80%, the ratio of the amount of incident light to the phosphor is set to 80% as described above. Can be adjusted. Therefore, the thickness of the first retardation plate 81 is not limited in terms of optical characteristics. That is, unlike the prior art, high accuracy with respect to the thickness of the first retardation plate 81 is not required.

  In FIG. 9, the amount of light LA corresponding to the ratio of the amount of light incident on the phosphor of 60% is indicated by the amount of light LA60. For example, when the light amount LA is adjusted to the light amount LA60, the rotation angle of the first phase difference plate 81 may be about 3 °, and the rotation angle of the first phase difference plate 81 than when the light amount LA is adjusted to the light amount LA80. Is small. However, in the curve shown in FIG. 9, the point where the light amount LA is the light amount LA60 has a larger slope than the point where the light amount LA is the light amount LA80, and the sensitivity to the rotation angle of the first retardation plate 81 is high. Therefore, when the light amount LA is adjusted to the light amount LA60, high accuracy is required for adjusting the rotation angle of the first retardation plate 81. Furthermore, in this case, since the sensitivity to the incident angle of the light beam BL incident on the first phase difference plate 81 is also high, light incident from a direction other than an angle close to the first phase difference plate 81 is intended. The polarization state may not be adjusted.

  Therefore, the azimuth angle φ of the optical axis D1 is set so that the phase difference of the first retardation plate 81 becomes λ / 2 + nλ (λ: the wavelength of light, n: a natural number) when the light amount LA becomes a desired value. It is desirable to set. That is, it is desirable to set the azimuth angle φ of the optical axis D1 so that the vertex of the curve in the graph of FIG. Thereby, the vertex of the curve of the graph of FIG. 9 becomes the value of the intended light quantity LA. Since the slope is small in the vicinity of the vertex of the curve in the graph of FIG. 9, the accuracy required for adjusting the rotation angle of the first retardation plate 81 can be lowered. Further, in this case, since the sensitivity to the incident angle of the light incident on the first phase difference plate 81 is also reduced, the light incident on the first phase difference plate 81 from a direction other than an angle close to the perpendicular is also obtained. It becomes easy to adjust to the intended polarization state.

  In the example shown in FIG. 9, the rotation angle of the first retardation plate 81 necessary for obtaining the desired light amount LA was 5 °. As long as it is limited to this example, the first retardation plate 81 can obtain a desired light amount LA as long as it can rotate at least 5 °. However, when the desired light amount LA is different from the example shown in FIG. 9, for example, when the thickness variation of the first retardation plate 81 is large, simply rotating the first retardation plate 81 by 5 ° It is conceivable that the desired light amount LA cannot be obtained. With respect to this problem, in the present embodiment, the phase difference control device 80 is configured so that two arrangements in which the inclination directions of the optical axis D1 are opposite to each other are possible, and therefore the first phase difference plate 81 is 5 °. Even if it rotates only, it is possible to adjust the amount of incident light in the range of ± 5 °. Therefore, the adjustment range of the light amount LA can be expanded without requiring a large space for rotating the first retardation plate 81.

  As described above, according to the phase difference control device 80 of the present embodiment, the allowable range for the accuracy of the thickness of the first phase difference plate 81 can be expanded. In particular, since the rotation axis 83 of the first retardation plate 81 is orthogonal to the plane including the orthogonal projection D2 of the optical axis D1 onto the first surface 81a and the optical axis D1, the first retardation plate 81 is used. The change in the phase difference with respect to the rotation angle of the first phase difference plate 81 can be increased, and the incident light quantity to the phosphor can be adjusted in a wider range without increasing the rotation angle of the first phase difference plate 81 so much.

  Since the illuminating device 70 of the present embodiment includes the above-described phase difference control device 80, an inexpensive phase difference plate can be used as the first phase difference plate 81, so that a low-cost illuminating device is realized. Can do. In addition, it is possible to realize an illumination device with a wide adjustment range of the color balance of illumination light. Since the projector 1 according to the present embodiment includes the illumination device 70 described above, it is possible to realize a low-cost projector having excellent color reproducibility.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the first retardation plate can be reversed and attached to the frame. However, instead of this configuration, the first retardation plate is the first retardation plate. It may be configured to be able to rotate 180 ° around a rotation axis parallel to the surface normal of the surface 81a. The first retardation plate does not need to be rotatable when the phase difference control device is used. For example, the first retardation plate may be configured to be rotatable when adjusting the phase difference before product shipment. After product shipment, the first retardation plate may be fixed and unable to rotate.

  Further, the positional relationship between the rotation shaft 83 and the first retardation plate 81 is not particularly limited. In the example shown in FIGS. 5 and 6, the rotation shaft 83 passes through the approximate center of the first retardation plate 81 in a plan view viewed from a direction parallel to the surface normal of the first surface 81 a. . However, the rotation shaft 83 may pass through, for example, the corner of the first retardation plate 81 in a plan view, or may not overlap the first retardation plate 81.

Although the example of the illuminating device including the reflective phosphor wheel has been described in the above embodiment, the illuminating device including the transmissive phosphor wheel may be used.
In addition, the specific description of the shape, number, arrangement, material, and the like of each component of the phase difference control device, the illumination device, and the projector is not limited to the above embodiment, and can be changed as appropriate. In the above-described embodiment, an example in which the lighting device according to the present invention is mounted on a projector using a liquid crystal light valve is shown, but the present invention is not limited to this. You may mount in the projector using a digital micromirror device as a light modulation apparatus.

  In the said embodiment, although the example which mounted the illuminating device by this invention in the projector was shown, it is not restricted to this. The lighting device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

  In the said embodiment, although the example of the wavelength conversion element which used fluorescent substance as a wavelength conversion element was given, it is not restricted to this. As the wavelength conversion element, for example, a wavelength conversion element using a compound semiconductor such as GaN or GaAs may be used.

  DESCRIPTION OF SYMBOLS 1 ... Projector, 4R, 4G, 4B ... Light modulation device, 27 ... Polarization beam splitter (polarization separation element), 47 ... Phosphor layer (wavelength conversion element), 60 ... Projection optical system, 70 ... Illumination device, 73 ... Semiconductor Laser (light emitting element), 80 ... phase difference control device, 81 ... first phase difference plate (phase difference plate), 82 ... phase difference plate rotation mechanism.

Claims (5)

A retardation plate having a first surface and an optical axis inclined with respect to the first surface;
A phase difference control device comprising: a phase difference plate rotation mechanism configured to rotate the phase difference plate around a rotation axis intersecting the surface normal of the first surface and the optical axis.   The phase difference control device according to claim 1, wherein the rotation axis is orthogonal to a plane including an orthogonal projection of the optical axis onto the first surface and the optical axis.   3. The phase difference control device according to claim 1, wherein the phase difference plate rotation mechanism is configured to be capable of two arrangements in which inclination directions of the optical axis with respect to the first surface are opposite to each other. . A light emitting element that emits a light beam;
The phase difference control device according to any one of claims 1 to 3, wherein the light beam is incident;
A polarization separation element that separates the light bundle transmitted through the phase difference control device into a first light bundle in a first polarization state and a second light bundle in a second polarization state;
A wavelength conversion element that emits fluorescence when irradiated with the first light beam. A lighting device according to claim 4;
A light modulation device that modulates light emitted from the illumination device according to image information;
A projector comprising: a projection optical system that projects light modulated by the light modulation device.

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