JP2012173593A - Light source device, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device which includes a laser light source and a light-emitting device including a fluorescent substance, reduces disturbance of a polarization direction of a laser light, and can solve a problem caused by the disturbance of the polarized light.SOLUTION: In the light source device 100 which includes a solid light source 10, and a rotatable substrate 40 including a crystalline member 46, when the thickness of the crystalline member 46 is represented by t, the birefringence of the crystalline member 46 is represented by Δn, and the wavelength of a light Lb emitted from the solid light source 10 is represented by λ, the thickness t of the crystalline member 46 satisfies Formula (1): (m-1/2)λ/Δn<t<(m+1/2)λ/Δn. In the formula, m is an arbitrary integer.

Description

  The present invention relates to a light source device and a projector.

  In the field of projectors, conventionally, a discharge lamp such as an ultra-high pressure mercury lamp has been mainly used as a light source. On the other hand, in recent years, a light source device has been proposed in which a phosphor emits fluorescence using light from a solid light source such as a light emitting diode (hereinafter abbreviated as LED) or a laser as excitation light, and the light is used. (For example, Patent Document 1).

The light source device of Patent Document 1 includes an excitation light source composed of an LED, a laser emitter, and the like, and a rotatable fluorescent wheel having three regions of a red phosphor forming region, a green phosphor forming region, and a diffusion layer forming region. I have. In this light source device, when the blue wavelength band light is emitted as excitation light from the excitation light source, and the excitation light is irradiated to the fluorescent wheel, the excitation light is irradiated to the red phosphor forming region at the same time as rotating the fluorescent wheel. During the period when red light fluoresces, green light fluoresces during the period when the excitation light is irradiated on the green phosphor formation region, and it is excitation light during the period when the excitation light is irradiated on the diffusion layer formation region Blue light is diffused and emitted.
According to Patent Document 1, it is described that visible light having lower energy than ultraviolet light is irradiated as excitation light, so that deterioration over time of optical components irradiated with excitation light can be suppressed and performance can be maintained over a long period of time. ing.

JP 2009-277516 A

  In the light source device of Patent Document 1, even if the laser light applied to the phosphor is a laser light in the visible light region having lower energy than ultraviolet light, if the intensity of the laser light is high, conversion loss in the phosphor As a part of the heat is changed into heat, the phosphor wheel generates heat. On the other hand, the fluorescent wheel can be cooled to some extent by adopting a configuration in which light is irradiated from a laser emitter to a predetermined position of the fluorescent wheel while rotating the fluorescent wheel. This is because the area of the fluorescent wheel is sufficiently large relative to the irradiation area of the laser light, and the effect of heat diffusion is that the irradiation position changes continuously as the fluorescent wheel rotates, so the laser light is a phosphor. This is because three effects can be expected: an effect of shortening the irradiation time to a specific place, and an effect of cooling the entire wheel by rotating the fluorescent wheel.

  Here, if it is going to improve the output of a light source device, it is necessary to increase the irradiation amount of a laser beam further, In that case, the improvement of the further cooling performance is desired. Therefore, quartz (thermal conductivity: about 5 to 9 W / m) that is superior in thermal conductivity to general optical glass (thermal conductivity: about 0.9 to 1.1 W / m · K) as the base of the fluorescent wheel. A method using a crystalline material such as K) is conceivable. However, since this type of crystalline material has a crystal axis, when the fluorescent wheel using this is rotated, the relationship between the polarization direction of the laser light and the crystal axis direction of the fluorescent wheel always changes, and the laser The polarization direction of light will be disturbed.

  Such disturbance of the polarization direction of the laser light has an adverse effect on the optical system in the subsequent stage. For example, when a polarization conversion element is used for the purpose of improving the light utilization efficiency of the projector, the polarization direction of the laser light is optimized by optimizing the polarization direction of the phase difference plate attached to the polarization conversion element. The amount of light incident on the phase difference plate can be reduced. However, if the fluorescent wheel made of a crystalline material is rotated for the purpose of suppressing the temperature rise of the phosphor, the polarization direction of the laser light is disturbed, and the amount of light incident on the phase difference plate attached to the polarization conversion element increases. To do. As a result, the life of the retardation plate is reduced. When the performance of the polarization separation film or the retardation plate of the polarization conversion element is deteriorated, light loss at the time of polarization conversion occurs, and the light use efficiency of the projector is lowered.

  The present invention has been made to solve at least a part of the above-described problems, and even when the substrate made of a crystalline material is rotated, disturbance in the polarization direction of light transmitted through the substrate is reduced. An object of the present invention is to realize a light source device. It is another object of the present invention to realize a projector using the above light source device.

In order to achieve the above object, a light source device of the present invention is provided on a solid light source and an optical path of light emitted from the solid light source, and is rotatable about a predetermined rotation axis. A substrate including a crystalline member, the wavelength of the light is λ (nm), the birefringence of the crystalline member is Δn, the thickness of the crystalline member is t (nm), and an arbitrary integer When m is m, the thickness of the crystalline member satisfies the following formula (1).
(M−1 / 2) λ / Δn <t <(m + 1/2) λ / Δn (1)

The polarization axis of light emitted from the solid light source is fixed. Hereinafter, the light emitted from the solid light source is referred to as emitted light. When the emitted light is transmitted through a substrate including a crystalline member having a predetermined crystal axis, the crystal axis is also rotated with the rotation of the substrate, so that the polarization axis of the emitted light and the crystal axis of the crystalline member included in the substrate are The angle formed by changes sequentially.
At this time, when the angle between the polarization axis of the emitted light and the crystal axis of the crystalline member is 0 ° or 90 °, the polarization is not disturbed, but the polarization axis of the emitted light and the crystal axis of the crystalline member As the angle formed by the angle shifts from 0 ° or 90 °, the polarization disturbance increases, and at 45 °, the polarization disturbance becomes maximum. Thus, when the angle formed by the polarization axis of the emitted light and the crystal axis of the crystalline member changes periodically, the degree of polarization disturbance also changes periodically.

  Specifically, when the crystalline material has a monolithic structure, the polarization disturbance appears to be minimum (no polarization disturbance) four times during one rotation, and the maximum appears four times. Further, the phase difference of the substrate determined by the thickness of the crystalline member and the birefringence Δn greatly affects the polarization disturbance. When the phase difference of the substrate is an odd multiple of half the excitation light wavelength λ, the polarization disturbance becomes maximum. That is, when the phase difference of the substrate is λ / 2, 3λ / 2, 5λ / 2,..., The polarization disturbance becomes maximum.

  On the other hand, if the thickness of the crystalline member is selected so as to satisfy the formula (1), it is possible to reduce the state in which the polarization disturbance is maximum or close to the maximum. As a result, it is possible to realize a light source device that can reduce the disturbance in the polarization direction of the light emitted from the solid light source and solve various problems associated with the disturbance in the polarization direction.

In the light source device described above, the thickness of the crystalline member can be further selected so as to satisfy the following formula (2).
t = mλ / Δn (2)

  By selecting the thickness of the crystalline member as in the formula (2) and setting the phase difference of the substrate to an integral multiple of the wavelength λ of the emitted light, it is possible to minimize the polarization disturbance. For example, when the phase difference of the substrate is λ, 2λ, 3λ,..., If the light emitted from the solid light source is incident on the substrate perpendicularly, the polarization is not disturbed. Even when the light emitted from the solid-state light source has a light distribution with a large component that is perpendicularly incident on the substrate, the polarization disturbance is minimized in the case of equation (2). As a result, it is possible to realize a light source device that can reduce the disturbance of the polarization direction of the light emitted from the solid light source and solve various problems associated with the disturbance of the polarization direction.

In the light source device described above, the solid light source may be a laser.
Since the laser has high polarization characteristics, the effect when the disturbance of the polarization direction is reduced is great. Thereby, by maintaining the polarization direction, it is possible to realize a light source device having a long lifetime and high efficiency.

In the light source device described above, quartz or sapphire can be selected as the crystalline member.
Quartz is a crystalline material that has a large volume of optical applications and is inexpensive, so that a light source device can be realized at low cost. In addition, since sapphire has high thermal conductivity among crystalline materials, a more reliable light source device can be realized.

In the light source device described above, a fluorescent material can be provided on the substrate.
The fluorescent material emits light when irradiated with excitation light, but generates heat due to conversion loss. Therefore, the fluorescent material is required to have a higher cooling performance than other materials such as a dielectric material. Therefore, a light source device in which the thermal deterioration of the fluorescent material is reduced can be realized.

  In the light source device described above, the solid-state light source, the base, and a polarization converter that is disposed downstream of the base and converts the polarization state of incident light into a predetermined polarization state and emits the converted light. An element.

  The polarization conversion element includes a polarization separation element and a phase difference plate, and the ratio of the P-polarized component and the S-polarized component of incident polarized light affects the efficiency and lifetime. Here, the S polarization component is a polarization component in a direction parallel to the polarization separation film surface of the polarization conversion element, and the P polarization component is a polarization component in a direction perpendicular to the S polarization component. The phase difference plate is provided only in the optical path of one polarization component of the polarization conversion element. Since the retardation plate has limitations on the polarization conversion efficiency and the lifetime, the efficiency and lifetime of the light source device can be improved by applying the present invention to increase the specific component in the polarization direction.

In the projector according to the aspect of the invention, the light source device described above, a light modulation element that modulates light emitted from the light source device, and a projection optical system that projects light modulated by the light modulation element onto a projection surface And.
By using the light source device of the present invention, a projector with high efficiency and long life can be realized.

It is a schematic block diagram of the projector of one Embodiment of this invention. It is the schematic which shows the example of the fluorescent substance wheel used for this projector. (A) is the top view seen from the direction of a rotating shaft, (B) is the side view seen from the direction orthogonal to a rotating shaft. It is the schematic which shows a part of polarization conversion element used for this projector. It is the schematic which shows the example of the fluorescent substance wheel used for this projector. (A) is the top view seen from the direction of a rotating shaft, (B) is the side view seen from the direction orthogonal to a rotating shaft. It is the schematic which shows the example of the fluorescent substance wheel used for this projector. (A) is the top view seen from the direction of a rotating shaft, (B) is the side view seen from the direction orthogonal to a rotating shaft. It is a schematic diagram which shows angle (theta) which the crystal axis of the fluorescent substance wheel used for this projector and the polarization axis of a laser beam make. (A) is a view with an angle θ of 0 °, (B) is a view with an angle θ of 45 °, and (C) is a view with an angle θ of 90 °.

Hereinafter, a light emitting element, a light source device, and a projector according to an embodiment of the invention will be described with reference to the drawings.
In all the drawings below, dimensions and ratios are appropriately changed depending on the components in order to make each component easy to see.

[Embodiment 1]
FIG. 1 is a schematic configuration diagram illustrating a light source device 100 and a projector PJ according to the present embodiment. As shown in FIG. 1, the projector PJ includes a light source device 100, a color separation optical system 200, a liquid crystal light valve (light modulation element) 400R, a liquid crystal light valve 400G, a liquid crystal light valve 400B, a dichroic prism (color combining element) 500, A projection optical system 600 is provided.

  The projector PJ generally operates as follows. The light emitted from the light source device 100 is separated into a plurality of color lights of different colors by the color separation optical system 200. The plurality of color lights separated by the color separation optical system 200 are incident on the corresponding liquid crystal light valve 400R, liquid crystal light valve 400G, and liquid crystal light valve 400B and modulated. The plurality of color lights modulated by the liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B enter the dichroic prism 500 and are combined. The light synthesized by the dichroic prism 500 is enlarged and projected onto the screen SCR by the projection optical system 600, and a full-color projection image is displayed.

Hereinafter, each component of the projector PJ will be described.
The light source device 100 includes a laser light source 10 (solid light source for excitation light), a condensing lens 22, a phosphor wheel 30 (an element in which a fluorescent material is provided on a substrate including a crystalline material), a collimating optical system 60, a lens. The array 120, the lens array 130, the polarization conversion element 140, and the superimposing lens 150 are arranged in this order.

Light emitted from the laser light source 10 enters the phosphor wheel 30 as excitation light Lb that excites a phosphor layer provided in the phosphor wheel 30 described later.
The laser light source 10 is a blue laser light source that emits blue laser light whose emission intensity peak is, for example, 445 nm. Here, a single laser light source is provided as the laser light source 10, but a plurality of laser light sources may be provided. Further, it may be a laser light source that emits colored light having a peak wavelength other than 445 nm as long as it is light having a wavelength that can excite a phosphor layer to be described later.

The condenser lens 22 is a convex lens. When a plurality of laser light sources 10 are provided, one condensing lens is arranged corresponding to each laser light source 10, and one convex lens common to all the laser light sources is arranged at the subsequent stage. good.
The condenser lens 22 is disposed on the optical axis of the laser light emitted from the laser light source 10 and condenses the excitation light Lb emitted from the laser light source 10.

  The phosphor wheel 30 transmits a part of the excitation light Lb (blue laser light) emitted from the laser light source 10, and the phosphor absorbs the rest, and the peak of the emission intensity becomes yellow fluorescence of about 550 nm, for example. It has a function to convert. Accordingly, white light is emitted from the phosphor wheel 30 as a result of the synthesis of the blue light that is the excitation light Lb and the yellow light emitted from the phosphor. The phosphor wheel 30 is provided with a motor 50 connected to the center of the base body 40 so as to be rotatable about the axis of the motor 50 as the rotation axis O.

FIG. 2 is a schematic view showing the phosphor wheel 30 of the present embodiment. 2A is a plan view of the phosphor wheel 30 viewed from the direction of the rotation axis O, and FIG. 2B is a side view of the phosphor wheel 30 viewed from the direction X orthogonal to the rotation axis O.
As shown in FIG. 2, the phosphor wheel 30 includes a base body 40 having a circular planar shape, and a phosphor layer 42 provided around the rotation axis O on the base body 40. The phosphor wheel 30 is arranged such that, of the two main surfaces of the base body 40, the main surface on which the phosphor layer 42 is not formed faces the condensing lens 22. It is arranged so that the focal position of the emitted excitation light Lb coincides with the position of the phosphor layer 42.
For example, the diameter of the circular phosphor wheel 30 is 50 mm, and the phosphor wheel 30 is provided so that the excitation light Lb is incident at a position about 22.5 mm away from the center of the phosphor wheel 30 in plan view. .

As shown in FIG. 2B, the base body 40 includes a crystalline member 46 having a crystal axis and a thickness t, and an amorphous member 44. The thickness t of the crystalline member 46 is equal to or less than the thickness t0 of the base body 40. Specifically, as the crystalline member 46, quartz, sapphire, or the like that transmits blue light that is the excitation light Lb can be used. As the non-crystalline member 44, white plate glass, heat-resistant glass, quartz, plastic, or the like can be used.
In the present embodiment, the base body 40 is composed of quartz that is an example of the crystalline member 46 and heat-resistant glass that is an example of the amorphous member 44. By combining quartz having excellent thermal conductivity and heat-resistant glass having excellent mass productivity, a design that achieves a balance between the heat dissipation characteristics and cost of the base 40 becomes possible. In this specification, for easy understanding, the crystal axis of the crystalline member 46 provided in the phosphor wheel 30 may be referred to as the crystal axis of the phosphor wheel 30.

  As described above, the phosphor layer 42 transmits a part of the excitation light Lb (blue laser light) emitted from the laser light source 10 and absorbs the rest to be yellow (emission intensity peak: about 550 nm). Emits fluorescence. The light emitted from the phosphor layer 42 forms white light by synthesizing the blue excitation light Lb and the yellow fluorescence. Further, the phosphor layer 42 includes a light-transmitting base material, a plurality of phosphor particles that emit fluorescence, and a plurality of filler particles that are particulate substances having light transmittance. The base material contains a plurality of phosphor particles and a plurality of filler particles. As the material for forming the base material, a resin material having optical transparency can be used. For example, a silicone resin having a high heat resistance (refractive index: about 1.4) can be suitably used.

The phosphor particles are particulate fluorescent materials that absorb the excitation light Lb emitted from the laser light source 10 shown in FIG. 1 and emit fluorescence. For example, the phosphor particles include a substance that emits fluorescence when excited by blue laser light having a wavelength of about 445 nm, and a part of the excitation light Lb emitted from the laser light source 10 is changed from the red wavelength band to the green color. Are converted into light that includes up to the wavelength band, i.e., yellow light, and emitted. As such phosphor particles, those having an average particle diameter of about 1 μm to several tens of μm are known to exhibit high luminous efficiency. As the phosphor particles, known YAG (yttrium / aluminum / garnet) phosphors can be used. For example, a YAG phosphor (refractive index: about 1.8) having an average particle size of 10 μm and a composition represented by (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce can be used. In addition, the constituent material of the phosphor particles may be one kind, or a mixture of particles made of two or more kinds of constituent materials may be used as the phosphor particles.

The filler particles have a function of diffusing the excitation light Lb incident on the phosphor layer 42 and the fluorescence emitted from the phosphor particles. As a constituent material of the filler particles, a wide variety of materials such as a resin material and an inorganic material can be used as long as they are particulate substances having light transmittance. Among them, an inorganic material having high heat resistance can be suitably used. For example, Al ₂ O ₃ (refractive index: about 1.8) having an average particle diameter of 10 μm can be used.

  The motor 50 rotates the phosphor wheel 30 at, for example, 7500 rpm. In this case, the irradiation area (beam spot) of the excitation light Lb on the phosphor wheel 30 moves at about 18 m / second. That is, the motor 50 functions as a position displacement unit that displaces the position of the beam spot on the phosphor wheel 30. Thereby, since the excitation light Lb does not continue to irradiate the same position on the phosphor wheel 30, it is possible to prevent thermal deterioration of the irradiation position and extend the life of the apparatus.

  The collimating optical system 60 includes a first lens 62 that suppresses the spread of light from the phosphor wheel 30 and a second lens 64 that substantially collimates the light incident from the first lens 62, and the phosphor wheel as a whole. The light emitted from 30 is collimated. The first lens 62 and the second lens 64 are configured as convex lenses.

The lens array 120 and the lens array 130 make the luminance distribution of the light emitted from the collimating optical system 60 uniform. The lens array 120 includes a plurality of first microlenses 122, and the lens array 130 includes a plurality of second microlenses 132. The first microlens 122 has a one-to-one correspondence with the second microlens 132.
The light emitted from the collimating optical system 60 is spatially divided and incident on the plurality of first microlenses 122. The first micro lens 122 forms an image of the incident light on the corresponding second micro lens 132. Thereby, a secondary light source image is formed on each of the plurality of second microlenses 132. Note that the outer shapes of the first microlens 122 and the second microlens 132 are substantially similar to the outer shapes of the image forming regions of the liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B.

The polarization conversion element 140 converts the polarization state of the light L emitted from the lens array 130 into one state. FIG. 3 shows a part of the polarization conversion element 140. The polarization conversion element 140 includes two lights having different polarization directions included in the light L incident on the polarization conversion element 140, for example, a polarization separation element 141 that separates P-polarized light and S-polarized light, and two different polarization directions. A retardation plate 142 that converts the polarization direction of one of the lights into the polarization direction of the other light.
Further, the polarization separation element 141 includes a polarization separation film 143 (hereinafter referred to as a PBS film) and a mirror 144 provided corresponding to each second microlens 132 of the lens array 130. The light incident on the polarization separation element 141 from the second microlens 132 is separated into P-polarized light (P-polarized light with respect to the PBS film) and S-polarized light (P-polarized light with respect to the PBS film) by the PBS film 143. One of the P-polarized light and S-polarized light (for example, S-polarized light) is reflected by the mirror 144 and then enters a phase difference plate 142 provided corresponding to the second microlens 132. One polarized light (S-polarized light) incident on the retardation film 142 is converted into the polarization state of the other polarized light (here, P-polarized light) by the retardation film 142 and transmitted through the PBS film 143. The light is emitted in the same state (here, P-polarized light) as (P-polarized light).

  The superimposing lens 150 shown in FIG. 1 superimposes light emitted from the polarization conversion element 140 on the liquid crystal light valve (illuminated area) 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B. The light emitted from the light source device 100 is spatially divided and then superimposed, whereby the luminance distribution is made uniform and the axial symmetry around the light axis 100ax is enhanced.

The color separation optical system 200 includes a dichroic mirror 210, a dichroic mirror 220, a mirror 230, a mirror 240, a mirror 250, a relay lens 260, and a relay lens 270.
The dichroic mirror 210 and the dichroic mirror 220 are obtained by, for example, laminating a dielectric multilayer film on a glass surface. The dichroic mirror 210 and the dichroic mirror 220 have a characteristic of selectively reflecting color light in a predetermined wavelength band and transmitting color light in other wavelength bands. Here, the dichroic mirror 210 has a characteristic of reflecting green light and blue light and transmitting red light. The dichroic mirror 220 has a characteristic of reflecting green light and transmitting blue light among green light and blue light transmitted through the dichroic mirror 210.

  The light L emitted from the light source device 100 enters the dichroic mirror 210. The red light R of the light L enters the mirror 230 through the dichroic mirror 210, is reflected by the mirror 230, and enters the field lens 300R. The red light R is collimated by the field lens 300R and then enters the liquid crystal light valve 400R for red light modulation.

  Green light G and blue light B in the light L are reflected by the dichroic mirror 210 and enter the dichroic mirror 220. The green light G is reflected by the dichroic mirror 220 and enters the field lens 300G. The green light G is collimated by the field lens 300G and then enters the liquid crystal light valve 400G for green light modulation.

  The blue light B that has passed through the dichroic mirror 220 passes through the relay lens 260 and is reflected by the mirror 240, then passes through the relay lens 270, is reflected by the mirror 250, and enters the field lens 300B. The blue light B is collimated by the field lens 300B and then enters the liquid crystal light valve 400B for blue light modulation.

The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B are configured by a light modulation device such as a transmissive liquid crystal light valve. The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B are electrically connected to a signal source (not shown) such as a personal computer that supplies an image signal including image information. The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B modulate the incident light for each pixel based on the supplied image signal to form an image.
The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B form a red image, a green image, and a blue image, respectively. The light (formed image) modulated by the liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B enters the dichroic prism 500.

The dichroic prism 500 has a structure in which four triangular prisms are bonded to each other. The surface to be bonded in the triangular prism becomes the inner surface of the dichroic prism. On the inner surface of the dichroic prism 500, a mirror surface that reflects red light and transmits green light and a mirror surface that reflects blue light and transmits green light are formed orthogonal to each other. The green light incident on the dichroic prism 500 is emitted as it is through the mirror surface. The red light and blue light incident on the dichroic prism 500 are selectively reflected or transmitted by the mirror surface and emitted in the same direction as the emission direction of the green light.
In this way, the three color lights (images) are superimposed and combined, and the combined color light is enlarged and projected onto the screen SCR by the projection optical system 600.

  In the light source device 100, the position of the laser light source 10 and the direction of the polarization axis of the laser light (excitation light Lb) emitted from the laser light source 10 are fixed. Here, as shown in FIG. 6, the polarization axis of the laser beam is represented by P, and the crystal axis of the phosphor wheel 30 (crystal axis of the crystalline member 46) is represented by K. While the phosphor layer 42 is irradiated with laser light, the phosphor wheel 30 is always rotating around the rotation axis O. Therefore, with the rotation of the phosphor wheel 30, the laser beam irradiation spot LS on the phosphor layer 42 moves around the rotation axis of the phosphor wheel 30, and the phosphor wheel 30 at the laser beam irradiation spot LS The crystal axis K also rotates. Therefore, the angle θ formed between the polarization axis P of the laser light and the crystal axis of the phosphor wheel 30 at the laser light irradiation spot LS changes sequentially.

As shown in FIGS. 6A and 6C, when the angle θ formed by the polarization axis P of the laser beam and the crystal axis K of the crystalline member 46 is 0 ° or 90 °, the polarization is disturbed. Does not occur. However, as the angle θ formed between the polarization axis P of the laser beam and the crystal axis K of the crystalline member 46 deviates from 0 ° or 90 °, the disturbance of polarization increases, and as shown in FIG. When θ is 45 °, the polarization disturbance is maximized.
Thus, when the angle θ formed by the polarization axis P of the laser beam and the crystal axis K of the crystalline member 46 changes periodically, the degree of polarization disturbance also changes periodically. Specifically, when the crystalline material has a monolithic structure, the polarization disturbance appears to be minimum (no polarization disturbance) four times during one rotation, and the maximum appears four times.

Further, the phase difference N of the crystalline member determined by the thickness t of the crystalline member 46 (see FIG. 2B) and the birefringence Δn of the crystalline member 46 greatly affects the polarization disturbance. Here, the phase difference N of the crystalline member 46 is obtained by the following formula (3).
N = t × Δn (3)

When the phase difference N of the crystalline member 46 is an odd multiple of half the wavelength λ of the excitation light Lb (N = λ / 2, 3λ / 2, 5λ / 2,...), The polarization disturbance becomes maximum. That is, when the thickness t of the crystalline member 46 satisfies the following formula (4), the polarization disturbance is maximized.
t = (m−1 / 2) λ / Δn (m is an arbitrary integer) (4)
On the other hand, when the phase difference N of the crystalline member 46 is an integral multiple of the wavelength λ of the excitation light Lb (N = λ, 2λ, 3λ,...), The polarization disturbance is minimized. That is, when the thickness t of the crystalline member 46 satisfies the following formula (2), the polarization disturbance is minimized.
t = mλ / Δn (2)
In particular, when the excitation light Lb emitted from the laser light source 10 satisfies the formula (2) and is completely linearly polarized parallel light, and the excitation light Lb is incident on the substrate 40 perpendicularly, the polarization is disturbed. Does not occur.

  Next, the effect of this invention is demonstrated using Example 1 thru | or 6.

Example 1
In the present embodiment, x = 1 in the following formula (5), so that the formula (5) is satisfied, the crystalline member 46 has a birefringence Δn and the wavelength λ of the excitation light Lb according to the birefringence Δn. A thickness t was set.
t = xλ / Δn (5)
In the formula (5), when x = 1, the phase difference N of the crystalline member 46 is an integral multiple of the wavelength λ of the excitation light Lb, so that the polarization disturbance is minimized. If the laser light (excitation light Lb) is completely linearly polarized parallel light, and the polarization separation function of the polarization conversion element 140 is perfect, the light amount of the laser light irradiated on the phase difference plate 142 is 0, that is, Be minimized.

  Thereby, even if the phosphor wheel 30 is rotating, the polarization direction disturbance of the excitation light Lb emitted from the laser light source 10 and transmitted through the phosphor wheel 30 is extremely reduced, and various problems associated with the polarization direction disturbance are solved. It is possible to realize a light source device that can be used.

Since the polarization state of the laser light has a high degree of polarization and can be regarded as linearly polarized light, the polarization state in the projector PJ is maintained by maintaining the polarization state from being emitted from the laser light source 10 to being incident on the polarization conversion element 140. The amount of laser light applied to the phase difference plate 142 of the conversion element 140 can be reduced.
In the polarization conversion element 140, only one polarization (referred to as the first polarization) out of the two polarizations having different polarization states is transmitted through the retardation plate 142, and the other polarization (referred to as the second polarization) passes through the retardation plate 142. Not transparent. Therefore, if the laser light does not include the first polarized light, the laser light can be prevented from being irradiated onto the retardation plate 142.
However, when a crystalline member such as quartz is used for the phosphor wheel 30, the amount of light transmitted through the phase difference plate 142 increases as a result of the polarization state being disturbed by passing through the crystalline member. It causes a decrease in lifespan and a decrease in light utilization efficiency.

  In that respect, in the light source device 100 of the present embodiment, the phosphor wheel 30 in which the thickness of the crystalline member 46 is optimized is set to x = 1 in the equation (5). Thereby, even if the phosphor wheel 30 rotates, the disturbance of the polarization state of the laser light (excitation light Lb) transmitted through the phosphor wheel 30 can be extremely reduced.

  Specifically, if the laser light (excitation light Lb) is completely linearly polarized parallel light and the polarization separation function of the polarization conversion element 140 is perfect, the amount of laser light irradiated to the phase difference plate 142 is 0. As a result, it is possible to realize the light source device 100 that can solve various problems such as a problem of a decrease in the lifetime of the polarization conversion element 140 due to disturbance of the polarization direction and a problem of a decrease in light utilization efficiency.

  Further, according to the projector PJ of the present embodiment, since the light source device 100 is provided, a projector with high reliability and excellent display quality can be realized.

(Example 2)
In this embodiment, the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the equation (5) is satisfied with x = 1.1. . In this case, the amount of laser light applied to the phase difference plate 142 is about 10% of the amount of laser light applied to the phase difference plate 142 when x = 1.5. In addition, the light quantity of the laser beam irradiated to the phase difference plate 142 means the average value of the light quantity of the laser beam irradiated to the phase difference plate 142 when the phosphor wheel 30 rotates once. The same applies to the following embodiments. Therefore, also in the present embodiment, compared with the case of x = 1.5, the effect of suppressing the lifetime reduction of the polarization conversion element 140 is high, and the effect of suppressing the decrease in light utilization efficiency is also high.
In this embodiment, x = 1.1, but even if x = 0.9, the same effect as in the case of x = 1.1 can be obtained.

(Example 3)
In this embodiment, the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the equation (5) is satisfied with x = 1.2. . In this case, the amount of laser light applied to the phase difference plate 142 is approximately 35% of the amount of laser light applied to the phase difference plate 142 when x = 1.5. Therefore, also in the present embodiment, compared with the case of x = 1.5, the effect of suppressing the lifetime reduction of the polarization conversion element 140 is high, and the effect of suppressing the decrease in light utilization efficiency is also high.
In this embodiment, x = 1.2, but even if x = 0.8, the same effect as in the case of x = 1.2 can be obtained.

Example 4
In this embodiment, the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the equation (5) is satisfied when x = 1.25. . In this case, the amount of laser light applied to the phase difference plate 142 is approximately 50% of the amount of laser light applied to the phase difference plate 142 when x = 1.5. Therefore, also in the present embodiment, compared with the case of x = 1.5, the effect of suppressing the lifetime reduction of the polarization conversion element 140 is high, and the effect of suppressing the decrease in light utilization efficiency is also high.
In this embodiment, x = 1.25, but even if x = 0.75, the same effect as in the case of x = 1.25 can be obtained.

(Example 5)
In this embodiment, the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the equation (5) is satisfied when x = 1.35. . In this case, the amount of laser light irradiated to the phase difference plate 142 is about 80% of the amount of laser light irradiated to the phase difference plate 142 when x = 1.5. Therefore, also in the present embodiment, compared with the case of x = 1.5, the effect of suppressing the lifetime reduction of the polarization conversion element 140 is high, and the effect of suppressing the decrease in light utilization efficiency is also high.
In this embodiment, x = 1.35, but even if x = 0.65, the same effect as in the case of x = 1.35 can be obtained.

(Example 6)
In this embodiment, the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the equation (5) is satisfied with x = 1.4. . In this case, the amount of laser light applied to the phase difference plate 142 is approximately 90% of the amount of laser light applied to the phase difference plate 142 when x = 1.5. Therefore, also in the present embodiment, compared with the case of x = 1.5, the effect of suppressing the lifetime reduction of the polarization conversion element 140 is high, and the effect of suppressing the decrease in light utilization efficiency is also high.
In this embodiment, x = 1.4, but even if x = 0.6, the same effect as in the case of x = 1.4 can be obtained.

As can be seen from Examples 1 to 6, the crystal member 46 is crystallized according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the thickness t of the crystalline member 46 satisfies the following formula (1). If the thickness t of the crystalline member 46 is set, the phase difference N of the crystalline member 46 cannot be an odd multiple of half the wavelength λ of the excitation light Lb, so that the polarization disturbance can be prevented from being maximized. it can. Thereby, the effect which suppresses the lifetime reduction of the polarization conversion element 140, and the effect which suppresses the fall of light utilization efficiency can be made higher than the case where Formula (4) is satisfied.
(M−1 / 2) λ / Δn <t <(m + 1/2) λ / Δn (1)
Further, if the thickness t of the crystalline member 46 is set according to the birefringence Δn of the crystalline member 46 and the wavelength λ of the excitation light Lb so that the thickness t of the crystalline member 46 satisfies the following formula (2): , Polarization disturbance can be minimized. Thereby, the effect which suppresses the lifetime reduction of the polarization conversion element 140, and the effect which suppresses the fall of light utilization efficiency can be made very high.
t = mλ / Δn (2)

[Embodiment 2]
FIG. 4 is a schematic configuration diagram showing the phosphor wheel 31 of the present embodiment. 4A is a plan view of the phosphor wheel 31 viewed from the direction of the rotation axis O, and FIG. 4B is a side view viewed from the direction X orthogonal to the rotation axis O. FIG.
As shown in FIG. 4, the phosphor wheel 31 includes a base body 41 having a circular planar shape and a phosphor layer 42 provided around the rotation axis O on the base body 41. As shown in FIG. 4, the base 41 is made of quartz that is an example of a crystalline member having a crystal axis and having a thickness t. Therefore, the thickness t of the crystalline member is equal to the thickness t0 of the base body 41. Since the crystal is excellent in thermal conductivity, the base body 41 can realize high heat dissipation characteristics. Further, the substrate 41 can achieve high mechanical durability with a simple configuration of a single crystal.

  When the thickness t of the crystalline member (base 41) satisfies the above-described formula (2), the polarization of the excitation light Lb that passes through the phosphor wheel 30 by the crystalline member even when the phosphor wheel 30 is rotating. Disturbance is minimal.

[Embodiment 3]
FIG. 5 is a schematic configuration diagram showing the phosphor wheel 32 of the present embodiment. 5A is a plan view of the phosphor wheel 32 viewed from the direction of the rotation axis O, and FIG. 5B is a side view viewed from the direction X orthogonal to the rotation axis O. FIG.
As shown in FIG. 5, the phosphor wheel 32 includes a base 43 having a circular planar shape and a phosphor layer 42 provided around the rotation axis O on the base 43. As shown in FIG. 5, the base body 43 includes a sector-shaped crystalline member 47, a sector-shaped crystalline member 48, a sector-shaped crystalline member 49, and a circular amorphous member 45. The crystalline member 47, the crystalline member 48, and the crystalline member 49 are all made of quartz, and the non-crystalline member 45 is made of heat resistant glass.
Further, if the thickness of the crystalline member 47 is t1, the thickness of the crystalline member 48 is t2, and the thickness of the crystalline member 49 is t3, the thickness t1, the thickness t2, and the thickness t3 are any Also, the thickness of the substrate 43 is not more than t0.
When a large crystal is used as the crystalline member, the cost becomes very high. Therefore, the phosphor wheel 32 can be manufactured at low cost by configuring the crystalline member with a plurality of small crystals as in this embodiment. Further, when the phosphor wheel 32 is configured using a plurality of crystalline members by attaching the crystalline member 47, the crystalline member 48, and the crystalline member 49 on the non-crystalline member 45, the phosphor wheel 32 is easily manufactured. can do.

When the thickness t1 satisfies the following formula (6), the thickness t2 satisfies the following formula (7), and the thickness t3 satisfies the following formula (8), the phosphor wheel 30 is rotated. However, the disturbance of polarization due to the crystalline member of the excitation light Lb that passes through the phosphor wheel 30 is minimized.
t1 = mλ / Δn (m is an arbitrary integer) (6)
t2 = nλ / Δn (n is an arbitrary integer) (7)
t3 = pλ / Δn (p is an arbitrary integer) (8)

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, although the example in which the phosphor layer 42 is formed on the substrate 40 as the phosphor wheel 30 has been shown, the phosphor may be dispersed in the substrate. The crystalline material is not limited to quartz, and sapphire may be used.

  Further, the shape of the rotating wheel is not limited to a circle, and a square or a polygon may be used. Even when a polygon is used as the rotating wheel, if the laser irradiation position is inside the rotating wheel, the locus of the laser irradiation spot is a circle. Therefore, even when a polygon is used as the rotating wheel, the locus of the laser irradiation spot is circular.

Further, the base body may be configured by combining a plurality of parts (for example, fan-shaped parts). If the thickness is optimized according to the crystalline material contained in each component (base), the same effect can be obtained.
Further, it is not always necessary to form a single and the same phosphor layer on the substrate. For example, it is possible to set a plurality of regions on one substrate, select a phosphor type, a thickness of the phosphor layer, and the presence or absence of the phosphor layer, and manufacture a rotating wheel in which the emission color changes in a time-sharing manner. . Even when the base is composed of a plurality of parts (for example, a fan shape), select the type of phosphor, the thickness of the phosphor layer, and the presence or absence of the phosphor layer for each part, and a rotating wheel whose emission color changes in a time-sharing manner. It can also be manufactured.

  Further, the specific configuration, arrangement, shape, number, and the like of each optical element of the projector can be appropriately changed without being limited to the above embodiment. The combination of the wavelength range of light emitted from the light source and the phosphor material can be changed as appropriate.

  DESCRIPTION OF SYMBOLS 10 ... Laser light source (excitation light source) 30, 31, 32 ... Phosphor wheel (light emitting element), 40, 41, 43 ... Substrate, 42 ... Phosphor layer, 46-49 ... Crystalline member, 100 ... Light source 140, polarization conversion element, 400R, 400G, 400B, liquid crystal light valve (light modulation element), 600, projection optical system, PJ, projector.

Claims (7)

A solid light source;
Provided on the optical path of the light emitted from the solid-state light source,
And is rotatable about a predetermined rotation axis,
And a substrate including a crystalline member,
The wavelength of the light is λ (nm),
The birefringence of the crystalline member is Δn,
The thickness of the crystalline member is t (nm),
When an arbitrary integer is m,
A thickness of the crystalline member satisfies the following formula (1).
(M−1 / 2) λ / Δn <t <(m + 1/2) λ / Δn (1) The light source device according to claim 1, wherein the thickness of the crystalline member further satisfies the following formula (2).
t = mλ / Δn (2)   The light source device according to claim 1, wherein the solid light source is a laser.   The light source device according to any one of claims 1 to 3, wherein the crystalline member is quartz or sapphire.   The light source device according to claim 1, wherein a fluorescent material is provided on the base. The solid-state light source; and the substrate;
Furthermore, it is arranged behind the base body,
And a polarization conversion element that converts the polarization state of incident light into a predetermined polarization state and emits the polarization state;
The light source device according to any one of claims 1 to 5, further comprising: The light source device according to any one of claims 1 to 6,
A light modulation element for modulating light emitted from the light source device;
A projection optical system that projects the light modulated by the light modulation element onto the projection surface;
A projector characterized by comprising:

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