JP2017211482A - Illumination device, method for manufacturing lens, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device capable of reducing stray light, a method for manufacturing a lens and a projector.SOLUTION: An illumination device includes: a light source for emitting first light of a first wavelength band; a phosphor layer for generating second light of a second wavelength band different from the first wavelength band by being irradiated with at least a part of the first light; a polarized light separation element being provided in an optical path between the light source and the phosphor layer, and transmitting or reflecting the second light while having a polarized light separation function with respect to the first light; a condensation optical system provided in the optical path between the polarized light separation element and the phosphor layer; and a first reflection element provided at an opposite side of the phosphor layer to the condensation optical system. The condensation optical system includes a lens having birefringence.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lighting device, a lens manufacturing method, and a projector.

  As a light source device for a projector, one using a solid light source that emits blue light made of laser light has been proposed (for example, Patent Document 1). In this light source device, the S-polarized component of the blue light emitted from the solid state light source is reflected by the dichroic mirror and condensed on the phosphor by the condenser lens.

JP 2012-137744 A

  By the way, in the light source device, a part of the blue light is converted into fluorescence by the phosphor, and the blue light that has not been converted to fluorescence is reflected to the light source device side by the dichroic mirror and becomes stray light. The stray light may cause problems such as heat generation of the solid light source and the casing.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an illumination device, a lens manufacturing method, and a projector that can reduce stray light.

  According to the first aspect of the present invention, the light source that emits the first light in the first wavelength band, and the first wavelength band by irradiating at least a part of the first light, Is provided in the optical path between the light source and the phosphor layer that generates second light in a different second wavelength band, and has a polarization separation function with respect to the first light And a polarization separation element that transmits or reflects the second light, a condensing optical system provided in an optical path between the polarization separation element and the phosphor layer, and the condensing of the phosphor layer. And a first reflecting element provided on the opposite side of the optical system, wherein the condensing optical system includes a birefringent lens.

In the illumination device according to the first aspect, the first light emitted from the light source is transmitted or reflected by the polarization separation element, and further passes through the condensing optical system and enters the phosphor layer. The polarization state of the first light is disturbed by the condensing optical system. A part of the first light is reflected by the surface layer of the phosphor layer, and the polarization state is further disturbed by passing through the condensing optical system again. Accordingly, a part of the component reflected by the surface layer of the phosphor layer is reflected or transmitted by the polarization separation element and proceeds in a direction different from that of the light source.
Thus, stray light traveling toward the light source can be reduced.

In the first aspect, the glass of the lens is preferably made of a material exhibiting birefringence.
According to this configuration, the polarization state of the first light transmitted through the condensing optical system can be disturbed.

In the first aspect, it is preferable that the lens has an optical axis, and the optical axis is substantially parallel to the optical axis of the lens.
According to this configuration, the refractive index distribution is rotationally symmetric with respect to the optical axis. Accordingly, the first light transmitted through the lens forms a small spot on the phosphor layer, so that the fluorescence emitted from the phosphor layer can be used efficiently. Since the first light is refracted on the surface of the lens and travels obliquely with respect to the optical axis, the lens causes disturbance in the polarization state of the first light.

In the first aspect, the glass is preferably quartz.
According to this configuration, it is possible to satisfactorily disturb the polarization state of the first light.

The first aspect may further include a lens fixing member that holds the lens in contact with a peripheral portion of the lens, and the stress distribution generated in the lens by the lens fixing member is non-uniform. preferable.
According to this configuration, even when the lens does not exhibit birefringence, birefringence can be imparted to the lens by generating a non-uniform stress distribution in the lens.

In the first aspect, the lens fixing member has at least three urging portions that come into contact with a peripheral edge portion of the lens, and the at least three urging portions are rotationally asymmetric around the optical axis of the lens. Preferably it is provided.
According to this configuration, a non-uniform stress distribution can be generated in the lens.

In the first aspect, it is preferable that the lens has a residual stress.
According to this configuration, birefringence can be imparted to the lens by residual stress.

The first aspect further includes a second reflecting element, wherein the polarization separation element separates the first light into third light and fourth light, and the phosphor layer includes the third light. The second reflection element is provided on the optical path of the fourth light so as to reflect the fourth light toward the polarization separation element. The phase difference plate is preferably provided on an optical path of the fourth light between the second reflecting element and the polarization separating element.
According to this configuration, illumination light composed of the second light and the fourth light can be generated.

  According to the second aspect of the present invention, there is provided a method of manufacturing a lens having birefringence, a molding step of molding a lens body by a hot press method, and the birefringence by forcibly cooling the lens body. And a cooling step to be produced.

  The lens manufacturing method according to the second aspect can easily and reliably manufacture a lens having birefringence.

In the second aspect, it is preferable that in the cooling step, the forced cooling is performed in a state where the temperature of the lens body is not uniform.
According to this configuration, the birefringence can be favorably imparted to the lens.

  According to the third aspect of the present invention, the illumination device according to the second aspect, a light modulation device that forms image light by modulating light from the illumination device according to image information, and the image light A projection optical system for projecting is provided.

  In the projector according to the third aspect, stray light is reduced.

FIG. 2 is a diagram illustrating a schematic configuration of a projector. The figure which shows schematic structure of an illuminating device. The figure which shows the lens with which the optical axis and the optical axis orthogonally crossed. The figure which shows the lens from which an optical axis and an optical axis become substantially parallel. The figure which shows the structure of a lens fixing member. The figure which shows the structure which concerns on the modification of a lens fixing member.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

First, an example of a projector according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a schematic configuration of a projector according to 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 video on a screen SCR. The projector 1 includes an illumination device 2, a color separation optical system 3, a light modulation device 4R, a light modulation device 4G, a light modulation device 4B, a combining optical system 5, and a projection optical system 6.

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

  The first dichroic mirror 7a separates the illumination light WL from the illumination device 2 into red light LR and other light (green light LG and blue light LB). The first dichroic mirror 7a transmits the separated red light LR and reflects other light (green light LG and blue light LB). On the other hand, the second dichroic mirror 7b reflects the green light LG and transmits the blue light LB, thereby separating the other light into the green light LG and the blue light LB.

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

  The first relay lens 9a and the second relay lens 9b are arranged on the light emission side of the second total reflection mirror 8b in the optical path of the blue light LB. The first relay lens 9a and the second relay lens 9b function to 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. have.

  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. A polarizing plate (not shown) is disposed on each of the incident side and the emission side of the liquid crystal panel.

  Further, a field lens 10R, a field lens 10G, and a field lens 10B are disposed on the incident side of the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, respectively. The field lens 10R, the field lens 10G, and the field lens 10B collimate the red light LR, the green light LG, and the blue light LB incident on the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, respectively.

  Image light from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B is incident on the combining optical system 5. The synthesis optical system 5 synthesizes image lights corresponding to the red light LR, green light LG, and blue light LB, respectively, and emits the synthesized image light toward the projection optical system 6. For example, a cross dichroic prism is used for the combining optical system 5.

  The projection optical system 6 includes a projection lens group, and 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.

(Lighting device)
Then, the illuminating device 2 which concerns on one Embodiment of this invention is demonstrated. FIG. 2 is a diagram showing a schematic configuration of the illumination device 2. As shown in FIG. 2, the illumination device 2 includes a light source device 2A, an integrator optical system 31, a polarization conversion element 32, and a superimposing lens 33a. In the present embodiment, the integrator optical system 31 and the superimposing lens 33a constitute a superimposing optical system 33.

  The light source device 2A includes an array light source 21A, a collimator optical system 22, an afocal optical system 23, a first retardation plate 28a, an optical element 25A including a polarization separation element 50A, and a first condensing optics. A system 26, a fluorescent light emitting element 27, a second phase difference plate 28b, a second condensing optical system 29, and a diffuse reflection element 30 are provided.

  An array light source 21A, a collimator optical system 22, an afocal optical system 23, a first retardation plate 28a, an optical element 25A, a second retardation plate 28b, and a second condensing optical system 29 The diffuse reflection elements 30 are sequentially arranged on the optical axis ax1. On the other hand, the fluorescent light emitting element 27, the first condensing optical system 26, the optical element 25A, the integrator optical system 31, the polarization conversion element 32, and the superimposing lens 33a are sequentially arranged on the optical axis ax2. Has been. The optical axis ax1 and the optical axis ax2 are in the same plane and are orthogonal to each other.

  The array light source 21A includes a plurality of semiconductor lasers 211 as solid light sources. The plurality of semiconductor lasers 211 are arranged in an array in a plane orthogonal to the optical axis ax1. The semiconductor laser 211 emits, for example, a blue light beam BL (for example, a laser beam having a peak wavelength of 460 nm). The array light source 21A emits a light bundle composed of a plurality of light beams BL. In the present embodiment, the array light source 21A corresponds to the “light source” in the claims, and the blue light beam BL corresponds to “first light in the first wavelength band” in the claims.

  The light beam BL emitted from the array light source 21 </ b> A enters the collimator optical system 22. The collimator optical system 22 converts the light beam BL emitted from the array light source 21A into parallel light. The collimator optical system 22 is composed of, for example, a plurality of collimator lenses 22a arranged in an array. The plurality of collimator lenses 22 a are arranged corresponding to the plurality of semiconductor lasers 211.

  The light beam BL that has passed through the collimator optical system 22 enters the afocal optical system 23. The afocal optical system 23 adjusts the beam diameter of the light beam BL. The afocal optical system 23 includes, for example, a convex lens 23a and a concave lens 23b.

  The light beam BL that has passed through the afocal optical system 23 enters the first retardation plate 28a. The first retardation plate 28a is, for example, a half-wave plate that can be rotated. The light beam BL emitted from the semiconductor laser 211 is linearly polarized light. By appropriately setting the rotation angle of the first phase difference plate 28a, the light beam BL transmitted through the first phase difference plate 28a includes the S polarization component and the P polarization component with respect to the optical element 25A at a predetermined ratio. It can be a light beam. By rotating the first retardation plate 28a, the ratio of the S-polarized component and the P-polarized component can be changed.

  A light beam BL including an S-polarized component and a P-polarized component generated by passing through the first retardation plate 28a is incident on the optical element 25A. The optical element 25A is composed of, for example, a dichroic prism having wavelength selectivity. The dichroic prism has an inclined surface K that forms an angle of 45 ° with the optical axis ax1. The inclined surface K forms an angle of 45 ° with respect to the optical axis ax2.

The inclined surface K is provided with a polarization separation element 50A having wavelength selection characteristics. Polarization separation element 50A has a light BL, the polarization separation function of separating into a light beam BL _p of the light beam BL _s and P-polarized component of S-polarized light component to the polarization separation element 50A. Specifically, the polarization separation element 50A reflects the light beam BL _s of the S polarization component and transmits the light beam BL _p of the P polarization component. The light beam BL _s and the light beam BL _p correspond to the third light and the fourth light, respectively, in the claims.

  Further, the polarization separation element 50A has a color separation function of transmitting the fluorescence YL having a wavelength band different from that of the light beam BL regardless of the polarization state.

The S-polarized light beam BL _s emitted from the polarization separation element 50 </ b> A enters the first condensing optical system 26. The first condensing optical system 26 condenses the light beam BL _s toward the phosphor layer 34. In the present embodiment, the first condensing optical system 26 corresponds to a “condensing optical system” in the claims.

In this embodiment, the 1st condensing optical system 26 is comprised from the 1st lens 26a and the 2nd lens 26b, for example. The light beam BL _s emitted from the first light collecting optical system 26 is incident on the fluorescent light emitting element 27 in a condensed state. The fluorescent light emitting element 27 includes a phosphor layer 34, a substrate 35 that supports the phosphor layer 34, and a fixing member 36 that fixes the phosphor layer 34 to the substrate 35.

In the present embodiment, the phosphor layer 34 is fixed to the substrate 35 by a fixing member 36 provided between the side surface of the phosphor layer 34 and the substrate 35. To the side where the light beam BL _s of the phosphor layer 34 is incident surface opposite is in contact with the substrate 35.

Phosphor layer 34 includes a fluorescent material that is excited by absorbing light BL _s. Excited phosphor by this ray BL _s is fluorescence (yellow light) YL emits having a peak wavelength in a wavelength range of 500 to 700 nm. In the present embodiment, the fluorescence YL corresponds to “second light in a second wavelength band different from the first wavelength band” in the claims.

  It is preferable to use a material having excellent heat resistance and surface processability for the phosphor layer 34. As such a phosphor layer 34, for example, a phosphor layer in which phosphor particles are dispersed in an inorganic binder such as alumina, or a phosphor layer in which phosphor particles are sintered without using a binder is suitable. Can be used.

To the side where the light beam BL _s of the phosphor layer 34 is incident reflecting portion 37 to is provided (the side opposite to the first condensing optical system 26) opposite. The reflection unit 37 reflects a component traveling toward the substrate 35 in the fluorescence YL generated in the phosphor layer 34. In the present embodiment, the reflecting portion 37 corresponds to a “first reflecting element” in the claims.

  A heat sink 38 is disposed on the surface of the substrate 35 opposite to the surface that supports the phosphor layer 34. In the fluorescent light emitting element 27, since heat can be radiated through the heat sink 38, thermal deterioration of the phosphor layer 34 can be prevented.

  Among the fluorescence YL generated in the phosphor layer 34, a part of the fluorescence YL is reflected by the reflecting portion 37 and emitted to the outside of the phosphor layer 34. In addition, among the fluorescence YL generated in the phosphor layer 34, another part of the fluorescence YL is emitted outside the phosphor layer 34 without passing through the reflection portion 37. In this way, the fluorescence YL is emitted from the phosphor layer 34.

  The fluorescence YL emitted from the phosphor layer 34 is non-polarized light. The fluorescence YL passes through the first condensing optical system 26 and then enters the polarization separation element 50A. The fluorescence YL travels from the polarization separation element 50 </ b> A toward the integrator optical system 31.

On the other hand, the P-polarized light beam BL _p emitted from the polarization separation element 50A is incident on the second retardation plate 28b. The second retardation plate 28b is composed of a quarter-wave plate disposed in the optical path between the polarization separation element 50A and the diffuse reflection element 30. Therefore, the P-polarized light beam BLp emitted from the polarization separation element 50A is converted into, for example, the clockwise circularly-polarized blue light BL _c 1 by the second retardation plate 28b, and then the second condensed light. The light enters the optical system 29.
The second condensing optical system 29 includes, for example, lenses 29a and 29b, and causes the blue light BL _c 1 to be incident on the diffuse reflection element 30 in a condensed state.

The diffuse reflection element 30 is disposed on the opposite side of the phosphor layer 34 in the polarization separation element 50A, and diffusely reflects the blue light BL _c 1 emitted from the second condensing optical system 29 toward the polarization separation element 50A. . As the diffuse reflection element 30, it is preferable to use an element that causes Lambertian reflection of the blue light BL _c 1 and that does not disturb the polarization state. In the present embodiment, the diffuse reflection element 30 corresponds to a “second reflection element” in the claims.

Hereinafter, the light diffusely reflected by the diffuse reflection element 30 is referred to as blue light BL _c 2. According to the present embodiment, the blue light BL _c 2 having a substantially uniform illuminance distribution is obtained by diffusely reflecting the blue light BL _c 1. For example, clockwise circularly polarized blue light BL _c 1 is reflected as counterclockwise circularly polarized blue light BL _c 2.

The blue light BL _c 2 is converted into parallel light by the second condensing optical system 29 and then enters the second retardation plate 28 b again.

The counterclockwise circularly polarized blue light BL _c 2 is converted into S-polarized blue light BL _s 1 by the second retardation plate 28b. The S-polarized blue light BL _s 1 is reflected toward the integrator optical system 31 by the polarization separation element 50A.

Thereby, the blue light BL _s 1 is used as the illumination light WL together with the fluorescence YL transmitted through the polarization separation element 50A. That is, the blue light BL _s 1 and the fluorescence YL are emitted from the polarization separation element 50A in the same direction, and white illumination light WL in which the blue light BL _s 1 and the fluorescence (yellow light) YL are mixed is generated. The

  The illumination light WL is emitted toward the integrator optical system 31. The integrator optical system 31 includes, for example, a lens array 31a and a lens array 31b. The lens arrays 31a and 31b are composed of a plurality of small lenses arranged in an array.

  The illumination light WL that has passed through the integrator optical system 31 enters the polarization conversion element 32. The polarization conversion element 32 includes a polarization separation film and a retardation plate. The polarization conversion element 32 converts the illumination light WL including the non-polarized fluorescence YL into linearly polarized light.

  The illumination light WL that has passed through the polarization conversion element 32 enters the superimposing lens 33a. The superimposing lens 33a cooperates with the integrator optical system 31 to uniformize the illuminance distribution by the illumination light WL in the illuminated area. In this way, the lighting device 2 generates the illumination light WL.

In the above description, an ideal case has been described in which all the light beams BL _s incident on the phosphor layer 34 are converted into fluorescence YL. However, in practice, a part of the light beam BL _s is reflected by the surface layer of the phosphor layer 34. Hereinafter, the reflected light reflected by the surface layer of the phosphor layer 34 is referred to as blue light BL _s 2. The blue light BL _s 2 passes through the first condensing optical system 26 and enters the polarization separation element 50A again.

  Here, the reflection at the surface layer of the phosphor layer 34 means direct reflection by the surface of the phosphor layer 34 or back scattering by a scatterer (for example, a bubble) provided in the vicinity of the surface layer of the phosphor layer 34. including.

For example, the polarization disturbance generated in the blue light BL _s 2 due to reflection on the surface layer of the phosphor layer 34 is small. Therefore, when the lens constituting the first condensing optical system 26 does not exhibit birefringence as in the prior art, the blue light BL _s 2 is incident on the polarization separation element 50A as approximately S-polarized light, and polarization separation is performed. It becomes stray light by being reflected to the array light source 21A side by the element 50A. The stray light may cause problems such as heat generation of the light source device 2A including the array light source 21A.

However, in the present embodiment, because of the use of those having birefringence as a lens constituting the first condensing optical system 26, the polarization state of the blue light BL s ₂ is the first condensing optical system 26, the blue light BL _s 2 becomes light including a P-polarized component for the polarization separation element 50A.

Here, the relationship between the optical axis of a lens having general birefringence and the optical axis of the lens will be described. However, it is assumed that the lens exhibits uniaxial birefringence.
3 and 4 are diagrams showing the relationship between the optical axis and the optical axis in the lens.
In the lens R1 shown in FIG. 3, the optical axis A1 of the lens R1 and the optical axis K1 of the lens R1 are orthogonal to each other. In the lens R2 shown in FIG. 4, the optical axis A2 of the lens R2 and the optical axis K2 of the lens R2 are parallel.

In the lens R1 shown in FIG. 3, since the optical axis A1 and the optical axis K1 are orthogonal to each other, the polarization state of the light (the light beam BL _s ) transmitted through the lens R1 is likely to be disturbed. However, since the optical axis A1 and the optical axis K1 are orthogonal to each other, the refractive index distribution is rotationally asymmetric around the optical axis A1. For this reason, the spot size formed in the illuminated region by the plurality of light beams that have passed through the lens R1 is relatively large.

On the other hand, in the lens R2 shown in FIG. 4, since the optical axis A2 and the optical axis K2 are parallel to each other, the refractive index distribution is rotationally symmetric around the optical axis A2. For this reason, the spot size formed in the illuminated area by the plurality of light beams that have passed through the lens R2 is smaller than when the lens R1 is used.
Even if the optical axis K2 and the optical axis A2 are parallel, as shown in FIG. 4, the light is refracted on the surface of the lens R2 and travels obliquely with respect to the optical axis. This advances in the direction intersecting the optical axis K2. Therefore, the lens R2 can cause disturbance in the polarization state of the light transmitted through the lens R2.

In the present embodiment, the lens R2 in which the optical axis and the optical axis satisfy the relationship (substantially parallel) shown in FIG. 4 is adopted as the first lens 26a and the second lens 26b that constitute the first condensing optical system 26. . That is, the first condensing optical system 26 has both the function of disturbing the polarization state of the blue light BL _s 2 and the function of reducing the spot size formed on the phosphor layer 34 (illuminated region). be able to. Actually, since the light beam BL _s passes through the first condensing optical system 26 once before entering the phosphor layer 34, the blue light BL _s 2 is transmitted through the first condensing optical system 26. Will pass through substantially twice.

As described above, the blue light BL _s 2 whose polarization state is disturbed by the first condensing optical system 26 includes a P-polarized component for the polarization separation element 50A. The P-polarized component is separated from the blue light BL _s 2 by the polarization separation element 50A, and becomes the blue light BL _p 1. The blue light BL _p 1 travels from the polarization separation element 50A toward the integrator optical system 31.
The blue light BL _p 1 can be used as blue light constituting the illumination light WL.

According to the illumination device 2 according to the present embodiment, it is possible to reduce the generation of stray light by reducing the component (S-polarized light component) of the blue light BL s ₂ is reflected by the polarization separation element 50A.

Further, since the blue light BL _p 1 that is a part of the blue light BL _s 2 is effectively used as the illumination light WL, the light output efficiency of the light beam BL can be increased, thereby suppressing the light output of the array light source 21A. It becomes.

  In addition, according to the present embodiment, since the lens R2 shown in FIG. 4 is used, the spot size formed on the phosphor layer 34 that becomes the illuminated region can be reduced, so that the light is emitted from the phosphor layer 34. The fluorescent YL can be used efficiently.

The degree of stray light reduction can be adjusted by the birefringence imparted to the first lens 26a and the second lens 26b. For example, the first lens 26 a and the second lens 26 b adjust the birefringence of each lens so as to give a total phase difference of λ / 2 to the light transmitted through the first condensing optical system 26 in a reciprocating manner. You may do it. By adjusting in this way, the blue light BL _s 2 can be converted into substantially P-polarized light when the first condensing optical system 26 is transmitted twice in a reciprocating manner. Then, since generation | occurrence | production of stray light (light of S polarization component) can be minimized, the blue light BL _s 2 can be efficiently used as the illumination light WL.

  In addition, this invention is not limited to the content of the said embodiment, In the range which does not deviate from the main point of invention, it can change suitably.

(Modification 1)
In the above-described embodiment, the case where both the first lens 26a and the second lens 26b are composed of lenses having birefringence has been described as an example. However, only one of the first lens 26a and the second lens 26b is used. It may have birefringence.

(Modification 2)
The first lens 26a or the second lens 26b may partially have birefringence. For example, only the region away from the optical axis of the lens may have birefringence. This is because the greater the distance from the optical axis, the greater the angle that the light traveling inside the lens makes with the optical axis.

(Modification 3)
In the above embodiment, the first lens 26a and the second lens 26b are made of birefringent material (quartz) so as to have birefringence. However, the present invention is not limited to this, and the lens Birefringence may be imparted by internal residual stress.

  Hereinafter, a method for manufacturing a lens having residual stress (birefringence) inside will be described. This lens manufacturing method includes a molding step and a cooling step.

  The molding step is a step of molding a lens body by a hot press method. As the hot press method in the molding process, there are a direct press method and a reheat press method. The direct press method is a method in which a lens body is press-molded by directly casting glass flowing out of a melting furnace into a mold. In the reheat press method, a glass material preliminarily processed into a fixed shape is placed between a pair of molds, and a lens body is molded by heating and pressing. In the molding process, it is desirable to use a direct press method. This is because the direct press method cures from a state in which the entire glass is melted, so that the residual stress inside the lens as described later can be increased.

The cooling step is a step of generating birefringence by forcibly cooling the hot-formed lens body that has been press-molded. In the present embodiment, in the cooling process, forced cooling is performed in a state where the temperature of the lens body is not uniform. For example, in the cooling process, the cooling air is applied to only one surface of the lens body, or the cooling air is applied to only one half when the lens body is viewed in plan from the optical axis direction. Can be in a state. The lens body cooled in a non-uniform temperature state is cured in a state where distortion is generated. A lens composed of a lens body cured through such a cooling process has distortion (residual stress). The lens having such distortion has birefringence due to the photoelastic effect.
According to the lens manufacturing method described above, it is possible to easily and reliably manufacture a lens having birefringence.

  As another manufacturing method, the annealing step may be omitted from the manufacturing process of a normal optical lens (lens having no birefringence). By omitting the annealing step, the temperature of the lens body can be cooled in a non-uniform state, so that a lens having residual stress as described above can be easily manufactured.

(Modification 4)
It is also possible to realize a lens having birefringence by distorting the lens by an external force. FIG. 5 is a diagram illustrating a configuration of a lens fixing member that holds a lens. The lens fixing member 40 shown in FIG. 5 holds the lens 41 in a state where the lens fixing member 40 is in contact with a peripheral edge portion 41 a located around the optical axis 45 of the lens 41. The lens fixing member 40 includes three urging portions 42 that come into contact with the peripheral edge portion 41 a of the lens 41, and a main body portion 43 that holds the urging portion 42. Each urging portion 42 is configured by, for example, a leaf spring, and applies an urging force to the peripheral portion 41 a of the lens 41.

  The three urging portions 42 are provided around the optical axis 45 of the lens 41 so as to be rotationally asymmetric. The lens 41 is in a state where an external force is applied to a position that is rotationally asymmetric around the optical axis 45 in the peripheral edge portion 41a. Therefore, the lens 41 is in a state where a non-uniform stress distribution is generated. Therefore, since the lens 41 is in a state where stress strain is generated, the lens 41 has birefringence.

  By using such a lens fixing member 40, it is possible to impart birefringence to a lens that does not have birefringence in a state where no external force is applied. Therefore, by attaching a normal optical lens to the lens fixing member 40, an optical lens having the same birefringence as that of the first embodiment can be realized. In addition, you may make it attach the lens which has birefringence to the said lens fixing member 40, If it does in this way, the birefringence which a lens has with the lens fixing member 40 can be adjusted.

  The number of urging portions 42 in the lens fixing member 40 is not limited to three. The lens fixing member 40 only needs to have at least three urging portions 42. If the lens 41 is held in a state where the uneven stress distribution is generated as described above, four or more are provided. May be.

(Modification 5)
FIG. 6 is a diagram showing a configuration according to a modification of the lens fixing member.
A lens fixing member 60 shown in FIG. 6 includes a frame-shaped main body 62 that holds a peripheral edge 61 a located around the optical axis 55 of the lens 61 from three directions, and a single lens presser attached to the main body 62. Part 63. Based on such a configuration, the lens fixing member 60 holds the lens 61 so that an external force is applied to the lens 61 from four directions by the main body portion 62 and the lens pressing portion 63. The external force applied to the lens 61 is rotationally asymmetric around the optical axis 56 of the lens 61. Therefore, a non-uniform stress distribution occurs in the lens 61, and the lens 61 has birefringence.

  By using such a lens fixing member 60, it is possible to impart birefringence to a lens that does not have birefringence in a state where no external force is applied. Therefore, by attaching a normal optical lens to the lens fixing member 60, an optical lens having the same birefringence as that of the first embodiment can be obtained. In addition, you may make it attach the lens which has birefringence to the said lens fixing member 60, By doing in this way, the birefringence which a lens has with the lens fixing member 60 can be adjusted.

(Modification 6)
The fixing member may be composed of a ring-shaped frame. In this ring-shaped fixing member, the shape of the opening for holding the lens is not similar to the outer shape of the lens. According to this configuration, a non-uniform stress distribution can be generated in the lens held in the opening.

In the above-described embodiment, the S-polarized light beam BL _s reflected by the polarization separation element 50A is incident on the phosphor light emitting element 27, and the P-polarized light beam BL _p transmitted through the polarization separation element 50A is incident on the diffuse reflection element 30. However, the positional relationship between the phosphor light-emitting element 27 and the diffuse reflection element 30 with respect to the polarization separation element 50A may be interchanged. That is, the S-polarized light beam BL _s reflected by the polarization separation element 50A is incident on the diffuse reflection element 30, and the P-polarized light beam BL _p transmitted through the polarization separation element 50A is incident on the phosphor light emitting element 27. good.

  In the above-described embodiment, the projector 1 including the three light modulation devices 4R, 4G, and 4B is exemplified. However, the projector 1 can be applied to a projector that displays a color image with one light modulation device. A digital mirror device may be used as the light modulation device.

  In the above embodiment, the example in which the light source device according to the present invention is mounted on the projector has been shown, but the present invention is not limited to this. The light source device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

DESCRIPTION OF SYMBOLS 1 ... Projector, 2 ... Illuminating device, 4R, 4G, 4B ... Light modulation device, 6 ... Projection optical system, 21A ... Array light source (light source), 26 ... 1st condensing optical system (condensing optical system), 26a ... 1st lens, 26b ... 2nd lens, 30 ... Diffuse reflection element (2nd reflection element), 37 ... Reflection part (1st reflection element), 40, 60 ... Lens fixing member, 41, 61 ... Lens, 41a, 61a ... peripheral edge portion, 42 ... biasing portion, BL ... light beam (first light), YL ... fluorescence (second light), A1 ... optical axis, K1 ... optical axis.

Claims (11)

A light source that emits first light in a first wavelength band;
A phosphor layer that generates second light in a second wavelength band different from the first wavelength band by being irradiated with at least a part of the first light;
A polarization separation element provided in an optical path between the light source and the phosphor layer, having a polarization separation function with respect to the first light, and transmitting or reflecting the second light;
A condensing optical system provided in an optical path between the polarization separation element and the phosphor layer;
A first reflective element provided on the opposite side of the phosphor layer from the condensing optical system,
The condensing optical system includes a lens having birefringence. The illumination device according to claim 1, wherein the glass of the lens is made of a material exhibiting birefringence. The lens has an optical axis;
The illumination device according to claim 2, wherein the optical axis is substantially parallel to the optical axis of the lens. The lighting device according to claim 2, wherein the glass is crystal. A lens fixing member that holds the lens in contact with the peripheral edge of the lens;
The illumination device according to any one of claims 1 to 4, wherein a stress distribution generated in the lens by the lens fixing member is non-uniform. The lens fixing member has at least three urging portions that come into contact with the peripheral edge of the lens,
The lighting device according to claim 5, wherein the at least three urging portions are provided rotationally asymmetrically around the optical axis of the lens. The lighting device according to claim 1, wherein the lens has a residual stress. A second reflective element and a retardation plate;
The polarization separation element separates the first light into third light and fourth light,
The phosphor layer is provided on the optical path of the third light,
The second reflecting element is provided on the optical path of the fourth light so as to reflect the fourth light toward the polarization separating element,
The illuminating device according to claim 1, wherein the retardation film is provided on an optical path of the fourth light between the second reflective element and the polarization separation element. A method for producing a birefringent lens,
A molding process for molding a lens body by a hot press method,
A cooling step of generating the birefringence by forcibly cooling the lens body. The method for manufacturing a lens according to claim 9, wherein in the cooling step, the forced cooling is performed in a state where the temperature of the lens body is not uniform. The illumination device according to any one of claims 1 to 8,
A light modulation device that forms image light by modulating light from the illumination device according to image information; and
A projection optical system that projects the image light.

Images