Light source device and projection-type video display device

Abstract

Provided is a light source device that can emit colors with greater color purity by preventing color mixture with fluorescence of blue light, which is excitation light from a laser light source, that has become return light upon the blue light, having been reflected by a dichroic mirror and become retrograde light, being reflected by a reverse surface of a phosphor wheel. This light source device is provided with an excitation light source, a phosphor wheel, and a light guide optical system. The phosphor wheel comprises: a substrate; a phosphor region provided on one surface of the substrate and having a phosphor that converts light from the excitation light source into fluorescence; a light processing region provided at a position on another surface of the substrate that corresponds, back-and-front, with the phosphor region; and an opening provided from the one surface to the other surface of the substrate. The light guide optical system guides the majority of the light from the excitation light source to one surface of the phosphor wheel and generates synthesized light through the synthesis of transmitted light transmitted through the opening and the fluorescence, while meanwhile, the remainder of the light from the excitation light source becomes retrograde light which arrives at another surface of the phosphor wheel by being propagated through the light guide optical system in a different direction from the transmitted light without passing through the opening of the phosphor wheel. The light processing region has a diffusion layer that diffuses and reflects the retrograde light, and a color wheel is provided at a position where the synthesized light is incident.

Description

Light source device and projection-type image display device

[0001] The present disclosure relates to a light source device used in, for example, a projection-type video display device.

[0002] Conventionally, a light source device using a phosphor wheel having a phosphor layer that generates fluorescence when exposed to blue excitation light and an opening that transmits the blue excitation light has been used as a light source for a projection-type image display device (see, for example, Patent Document 1).

[0003] In the light source device, blue light, which is excitation light, is irradiated onto the phosphor layer of the phosphor wheel to generate fluorescence, and the phosphor wheel is rotated to transmit the blue light through an opening, generating a composite light in which the blue light, which is excitation light transmitted through an optical system such as a mirror, and the fluorescence generated before and after it are arranged in chronological order.

[0004] Japanese Patent Application Laid-Open No. 2020-64269

[0005] In a light source device using a phosphor wheel similar to that disclosed in Patent Document 1, a relay optical system for combining blue light, which is excitation light that has passed through an opening in the phosphor wheel, with fluorescence has a problem of backward light, in which the blue light, which is excitation light from the light source, travels backward through the optical system. For example, in the case of a light source device such as that shown in Figure 1, the blue light, which is excitation light from the light source, is partially reflected by a dichroic mirror and enters the optical system. As shown by the long dotted line, the blue light travels backward along the optical path taken by the blue light that has passed through the phosphor wheel, reaches the rear surface of the phosphor wheel, and is reflected by the rear surface. As shown by the short dotted line, the blue light, which is excitation light, travels along the optical path taken by the blue light that has passed through the phosphor wheel, and may be mixed with the fluorescence corresponding to the rotation state of the phosphor wheel.

[0006] The present disclosure aims to provide a light source device that can emit each color with high color purity by preventing the blue light, which is excitation light from a laser light source, from being reflected by a dichroic mirror and becoming back-traveling light, which is reflected by the back surface of a phosphor wheel, and by preventing the blue light, which becomes returned light, from mixing with fluorescence.

[0007] The light source device according to the present disclosure comprises an excitation light source, a phosphor wheel, and a light-guiding optical system, wherein the phosphor wheel has a substrate, a phosphor region provided on one side of the substrate and having a phosphor that converts light from the excitation light source into fluorescence, a light processing region provided on the other side of the substrate at a position corresponding to the front and back of the phosphor region, and an opening provided from one side to the other of the substrate, wherein the light-guiding optical system guides most of the light from the excitation light source to one side of the phosphor wheel and combines the transmitted light that has passed through the opening with the fluorescence to generate combined light, and at the same time, the remainder of the light from the excitation light source propagates through the light-guiding optical system in a direction different from that of the transmitted light without passing through the opening of the phosphor wheel, thereby becoming retrograde light that reaches the other side of the phosphor wheel, and the light processing region has a diffusion layer that diffuses and reflects the retrograde light, and the color wheel is provided at a position where the combined light is incident.

[0008] According to the light source device of the present disclosure, the rear surface of the phosphor wheel has a light processing region (diffusion layer) that diffuses blue light (retrograde light) that is excitation light from a laser light source and is reflected by a dichroic mirror and reaches the rear surface of the phosphor wheel. This makes it possible to suppress return light caused by reflection of the blue light (retrograde light) on the rear surface of the phosphor wheel, and as a result, it is possible to suppress the return light from mixing with the fluorescent light, thereby improving the color purity of the fluorescent light.

[0009] 4A is a schematic diagram showing the configuration of a light source device according to a first embodiment and a projection-type video display device including the light source device. FIG. 4B is a schematic plan view showing the optical path of blue excitation light from a light source in the light source device of FIG. 1 and the optical path of blue excitation light transmitted through a phosphor wheel. FIG. 4C is a schematic perspective view showing the three-dimensional structure of a light source. FIG. 4D is a schematic perspective view showing the configuration of a phosphor wheel in the light source device of FIG. 1. FIG. 4E is a schematic perspective view showing the polarization direction of light emitted from the light source elements in FIG. 4A. FIG. 4F is a schematic perspective view showing the configuration of a magenta color wheel in FIG. 4C. FIG. 4G is a schematic view explaining two color modes achieved by phase shifting using the magenta color wheel of FIG. 4C. FIG. 4H is a schematic view showing magenta segments and achromatic segments in color mode 1 of the magenta color wheel. FIG. 4I is a schematic view showing a light processing region on the back side of a phosphor wheel in a light source device according to a first modification. FIG. 4J is a schematic plan view showing a state in which fins are provided on the back side (the other surface) of the phosphor wheel in a light source device according to a second modification. 7A is a schematic cross-sectional view showing how the reflected blue light that has entered between the fins in FIG. 7A is repeatedly reflected by the side and bottom surfaces of the fins. FIG. 7B is a schematic diagram showing the configuration of a projection-type video display device according to a third embodiment, which is equipped with the light source device according to the first and second embodiments.

[0010] The light source device of the first aspect comprises an excitation light source, a phosphor wheel, and a light-guiding optical system, wherein the phosphor wheel has a substrate, a phosphor region provided on one side of the substrate and having a phosphor that converts light from the excitation light source into fluorescence, a light processing region provided on the other side of the substrate at a position corresponding to the front and back of the phosphor region, and an opening provided from one side to the other of the substrate, wherein the light-guiding optical system guides most of the light from the excitation light source to one side of the phosphor wheel and combines the transmitted light that has passed through the opening with the fluorescence to generate combined light, and at the same time, the remainder of the light from the excitation light source propagates through the light-guiding optical system in a direction different from the transmitted light without passing through the opening of the phosphor wheel, thereby becoming retrograde light that reaches the other side of the phosphor wheel, and the light processing region has a diffusion layer that diffuses and reflects the retrograde light, and the color wheel is provided at a position where the combined light is incident.

[0011] A light source device according to a second aspect is the light source device according to the first aspect, wherein the color wheel has a filter that transmits red light and blue light and reflects other light.

[0012] A light source device according to a third aspect is the second aspect, wherein the phosphor wheel has one surface on which a diffusion layer is provided, and the other surface is the back surface of the phosphor region corresponding to the filter.

[0013] A light source device according to a fourth aspect is the light source device of any one of the first to third aspects, wherein the diffusion layer may have a fine uneven structure.

[0014] A light source device according to a fifth aspect is any one of the first to fourth aspects, wherein the excitation light source emits blue light of a first polarization, and further comprises a dichroic mirror, which is a light combining element, disposed between the excitation light source and the phosphor wheel and transmits the blue light and reflects the fluorescence, and wherein the transmittance of the dichroic mirror for the first polarization of blue light may be higher than the transmittance of a second polarization of blue light having a polarization direction different from that of the first polarization.

[0015] A light source device according to a sixth aspect is the light source device according to the fifth aspect, wherein the first polarized light is P polarized light and the second polarized light is S polarized light.

[0016] A light source device according to a seventh aspect may be such that, in the third aspect described above, the phosphor wheel has a plurality of fins on one side and on the other side which is the back side of the phosphor region corresponding to the filter, and a diffusion layer is provided on the side of the fins and on the bottom surface between the fins.

[0017] A light source device according to an eighth aspect is the light source device according to the seventh aspect, wherein the diffusion layer may also be provided on the top surfaces of the fins.

[0018] A projection-type image display device according to a ninth aspect includes the light source device according to any one of the first to eighth aspects.

[0019] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, in some cases, more detailed explanation than necessary will be omitted. For example, detailed explanation of already well-known matters or redundant explanation of substantially identical configurations will be omitted. This is to avoid unnecessary redundancy in the following explanation and to facilitate understanding by those skilled in the art. Furthermore, in the drawings, substantially identical components are designated by the same reference numerals.

[0020] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0021] (Embodiment 1) [Configuration of Light Source Device] Fig. 1 is a schematic diagram showing the configuration of a light source device 20 according to embodiment 1 and a projection-type video display device 30 including the light source device 20. Fig. 2A is a schematic plan view showing the optical path of blue light 5a, which is excitation light from laser light sources 1a and 1b in light source device 20 of Fig. 1, and the optical path of blue light 5a transmitted through phosphor wheel 10. For convenience, in Fig. 2A, the direction of blue excitation light irradiated onto phosphor wheel 10 from laser light sources 1a and 1b is defined as the -X direction, a plane including the loop described by blue excitation light 5a transmitted through an opening is defined as the XY plane, and a direction perpendicular to this is defined as the Z direction.

[0022] Light source device 20 according to the first embodiment includes laser light sources 1 a and 1 b that emit laser light, a phosphor wheel 10 that converts light (laser light) from laser light sources 1 a and 1 b into fluorescence, a light combining element 6 that combines the light from laser light sources 1 a and 1 b with the fluorescence to generate combined light, and a color wheel 19 that is provided at a position where the combined light is incident. Phosphor wheel 10 includes substrate 11, phosphor region 13 that is provided on one surface of the substrate and has a phosphor that converts light from laser light sources 1 a and 1 b into fluorescence, opening 14 that is provided from one surface of substrate 11 to the other surface, and light processing region 15 that is provided on the other surface of substrate 11 and has a diffusion layer that diffuses blue light (reverse light) 5 b that is excitation light from laser light sources 1 a and 1 b and then reflected by dichroic mirror 6 and reaches the back surface of phosphor wheel 10.

[0023] 2A , blue light 5a emitted from laser light sources 1a and 1b passes through lenses 2a and 2b, is reflected by mirrors 3a and 3b, passes through concave lens 4a, enters diffuser plate 4b, the light beam is diffused, passes through dichroic mirror 6, and is irradiated onto phosphor wheel 10 via lens 7. When blue light 5a irradiated onto phosphor wheel 10 irradiates the phosphor in phosphor region 13 as phosphor wheel 10 rotates, it generates fluorescence 18, and fluorescence 18 passes through lens 7, is reflected by dichroic mirror 6, and is irradiated onto color wheel 19 via lenses 16a and 16b and mirror 17. On the other hand, blue light 5a that has passed through opening 14 travels from the rear surface of phosphor wheel 10 through an optical path consisting of three mirrors 8a, 8b, and 8c and four lenses 9a, 9b, 9c, and 9d, passes through dichroic mirror 6, is combined with fluorescence 18, and is then irradiated onto color wheel 19 via lenses 16a and 16b and mirror 17. The fluorescence having a wide wavelength range is filtered by color wheel 19, and output light in which the colored lights of the light source are arranged in time series is obtained and output via rod 21.

[0024] According to this light source device 20, the back side of phosphor wheel 10 has a light processing region (diffusion layer) 15 that diffuses blue light (reverse light) 5b that is generated when blue light 5a, which is excitation light from laser light sources 1a and 1b, is reflected by dichroic mirror 6 and reaches the back side of phosphor wheel 10. This makes it possible to suppress return light 5c caused by reflection of return light 5b on the back side of phosphor wheel 10, and as a result, to suppress the return light 5c from mixing with the fluorescent light. This makes it possible to emit each color with high color purity.

[0025] The components that make up this light source device 20 will be described below.

[0026] <Excitation Light Source> FIG. 2B is a schematic perspective view showing the three-dimensional structure of the laser light sources 1a and 1b. The laser light sources 1a and 1b emit laser light. For example, the laser light sources 1a and 1b may emit blue light. Furthermore, as in the light source device according to the second embodiment, they may emit blue light of a first polarization (e.g., P-polarized light). The laser light sources 1a and 1b, which are excitation light sources, may be configured, for example, as shown in FIG. 2B , by opposing rows of blue LDs arranged at different heights in the Z direction. The laser light sources 1a and 1b may be focused through convex lenses 2a and 2b, the beam width may be reduced, and the beam may be reflected by tilt-adjusted mirrors 3a and 3b to align the opposing beam directions. The beam may then be collimated by, for example, a concave lens 4a, and directed to a dichroic mirror 6. This allows the length L of the light source device 20 in the depth direction (X direction) to be shortened, thereby realizing space savings, rather than reducing the beam width after laser beam synthesis. Furthermore, since many LDs can be arranged in a small area, high brightness can be achieved. Alternatively, a diffuser 4b may be provided after the concave lens 4a. The diffuser 4b improves the uniformity of the spatial intensity distribution of the excitation light 5a and controls the spot size of the excitation light incident on the phosphor wheel 10 by adjusting the diffusion angle of the transmitted light. The smaller the excitation light spot size, the higher the efficiency with which the fluorescence emitted from the phosphor wheel 10 is transmitted through the subsequent optical system (optical system transmission efficiency). However, the higher the light density on the phosphor wheel, the lower the luminous efficiency of the phosphor. On the other hand, a larger excitation light spot size tends to increase the luminous efficiency of the phosphor but decrease the optical system transmission efficiency of the fluorescence in the optical system. Therefore, it is desirable to design the diffuser 4b to achieve an excitation light spot size that maximizes the final efficiency, which is the product of the luminous efficiency and the optical system transmission efficiency.

[0027] <Phosphor Wheel> Fig. 3A is a schematic diagram showing the configuration of the front surface of phosphor wheel 10 in light source device 20 of Fig. 1. Fig. 3B is a schematic diagram showing the configuration of the rear surface of phosphor wheel 10 in the light source device of Fig. 1. Phosphor wheel 10 includes substrate 11, phosphor regions 13a and 13b provided on the front surface (one surface) of substrate 11 and containing phosphors that convert light from laser light sources 1a and 1b into fluorescence, an opening 14 provided from the front surface (one surface) to the rear surface (other surface) of substrate 11, and a light processing region 15 provided on the rear surface (other surface) of substrate 11 and containing a diffusion layer that diffuses blue light (retrograde light) that reaches the rear surface of phosphor wheel 10 after blue light 5a, which is excitation light from laser light sources 1a and 1b, is reflected by dichroic mirror 6. Phosphor wheel 10 is provided with a motor. The motor is arranged circumferentially around the rotation axis so that blue light 5a, which is excitation light focused by lens 7, is incident on the same radial region from the rotation center where phosphor regions 13a, 13b and opening 14 are located. Each of the components that make up phosphor wheel 10 will be described below.

[0028] <Substrate> The substrate 11 may be, for example, a rotatable substrate. The substrate 11 may be, for example, disc-shaped. Or it may be polygonal. The substrate 11 may be, for example, an aluminum substrate with excellent heat dissipation properties. The substrate is not limited to aluminum and may be made of other metals. It may also be a transmissive substrate such as glass or sapphire, or a transmissive substrate such as glass or sapphire with a reflective area. As shown in Figures 3A and 3B, the substrate 11 may be provided with a motor mounting hole 32 for mounting a motor for rotation. Also, the motor may be attached by a method other than the motor mounting hole 32.

[0029] <Phosphor Region> The phosphor regions 13a and 13b contain a phosphor in a binder. For example, the phosphor region 13a may be a region containing a phosphor that generates yellow fluorescence, and the phosphor region 13b may contain a phosphor that generates green fluorescence. The yellow fluorescence may also contain red fluorescence. Even when the yellow fluorescence contains red fluorescence, light in a wavelength range to be used as each color of light from the light source can be selected by filtering using a color wheel, which will be described later, and yellow light and red light can also be obtained in the above case. Note that the phosphor regions 13a and 13b may be arranged circumferentially around the center of rotation, as shown in FIG. 3A, for example.

[0030] <Phosphor> The phosphor may be, for example, particles of a garnet structure. The chemical formula of the garnet structure is, for example, Y, which converts the wavelength of blue excitation light into yellow fluorescence. ３ Al ５ O １２ Or, Lu that converts blue excitation light into green fluorescence. ３ Al ５ O １２ Alternatively, it may be a mixture thereof ((Y, Lu) ３ Al ５ O １２ The activator may be, for example, Ce or Gd. Alternatively, particles that convert blue excitation light into fluorescence other than the aforementioned yellow or green may be used. The phosphor may be (Sr, Ca)AlSiN ３ :Eu ２＋ and CaAlSiN ３ :Eu ２＋ It is also possible to use red phosphors such as those mentioned above. By changing the structure, composition, etc., it is possible to vary the wavelength to be converted.

[0031] <Binder> The binder is a medium in which the phosphor is dispersed, and may be, for example, a heat-resistant transparent resin such as a silicone resin or polysilsesquioxane, or a glass such as silicon dioxide or silicate glass.

[0032] <Opening> Opening 14 is provided from the front surface (one surface) to the back surface (the other surface) of substrate 11. There may be one or more openings 14. Blue light 5a from laser light sources 1a and 1b passes through the openings and travels from the back surface of phosphor wheel 10 through an optical path formed by three mirrors 8a, 8b, and 8c and lenses 9a, 9b, and 9c, and then passes through dichroic mirror 6, which is a light combining element, and is combined with the fluorescent light.

[0033] <Light Processing Region> The light processing region 15 is provided on the rear surface (other surface) of the substrate 11 and includes a diffusion layer that diffuses blue light (reverse light) 5b, which is the excitation light from the laser light sources 1a and 1b and is reflected by the dichroic mirror 6. The diffusion layer may have a finely textured structure formed by, for example, sandblasting, but is not limited to, this. The diffusion layer may also be formed, for example, by attaching a light-diffusing glass plate. Alternatively, the diffusion layer may be formed by applying and curing a mixture of thermosetting resin and powder. The provision of the diffusion layer can suppress return light 5c due to reflection of return light 5b on the rear surface of the phosphor wheel 10, thereby reducing the remaining rate of return light in the fluorescence by approximately half or more. This is thought to be because the return light is diffused by the reflection of the diffusion layer, preventing it from entering the effective area of ​​at least one of the blue loop lens mirrors. Alternatively, instead of the diffusion layer, a light-absorbing layer coated with black paint, such as black anodized aluminum, may be provided to absorb backlight. The light-absorbing layer can reduce the residual rate of backlight in the fluorescent light to approximately 30% or less. The back surface of the phosphor wheel 10 may be flat, but fins may be provided on the back surface to enhance the cooling performance of the phosphor wheel 10. This can improve the upper limit of excitation light intensity and achieve higher brightness. The diffusion layer can also be provided even when fins are provided.

[0034] <Light Combining Element (Dichroic Mirror)> The light combining element 6 combines the blue light 5a from the laser light sources 1a and 1b with the fluorescent light 18 to generate combined light positioned at different times. The light combining element 6 is, for example, a dichroic mirror (color separation / combining mirror). The dichroic mirror 6 is provided between the laser light sources 1a and 1b and the phosphor wheel 10, and transmits the blue light while reflecting the fluorescent light. The dichroic mirror 6 may also have a higher transmittance for blue light of a first polarized light (P-polarized) than for blue light of a second polarized light (S-polarized) having a polarization direction different from that of the first polarized light. The dichroic mirror is made, for example, by forming a dielectric multilayer film on a glass plate.

[0035] <Relay Optical System> As described above, blue light 5a that has passed through opening 14 of phosphor wheel 10 travels from the rear surface of phosphor wheel 10 through an optical path that is configured by three mirrors 8a, 8b, and 8c and four lenses 9a, 9b, 9c, and 9d, passes through dichroic mirror 6, and is combined with fluorescence 18. These three mirrors 8a, 8b, and 8c and four lenses 9a, 9b, 9c, and 9d constitute first relay optical system 22 that forms an optical path that returns blue light 5a that has passed through opening 14 to dichroic mirror 6. Note that, although the first relay optical system is configured here by three mirrors 8a, 8b, and 8c and four lenses 9a, 9b, 9c, and 9d, the present invention is not limited to this and other configurations may be used.

[0036] As described above, dichroic mirror 6 transmits blue light 5a and reflects the fluorescent yellow light, so that the yellow light has its direction of travel changed by 90 degrees by dichroic mirror 6 and is then irradiated onto color wheel 19 via lenses 16a, 16b and mirror 17. Meanwhile, blue light 5a that has been incident on dichroic mirror 6 by first relay optical system 22 is transmitted through dichroic mirror 6 and combined with the fluorescent yellow light to form combined light, which is then irradiated onto color wheel 19 via lenses 16a, 16b and mirror 17. Note that the combined light referred to here is combined light obtained by chronologically arranging blue light, which is excitation light, and fluorescence generated before and after it.

[0037] <Color Wheel> The color wheel 19 filters the fluorescence generated by the phosphor wheel 10 to obtain light in wavelength ranges that can be used as each color of the light source. The color wheel may be, for example, a magenta color wheel, as shown in the second embodiment described below. Fluorescence may contain light in a relatively wide wavelength range compared to laser light. For example, as described above, yellow fluorescence may contain light in a wavelength range from green to red. In such a case, by using a magenta color wheel that transmits red and blue light but blocks other light, red fluorescence can be extracted from the yellow fluorescence, as described below.

[0038] 4A is a schematic diagram showing the configuration of a light source device 20a according to embodiment 2. Compared to the light source device according to embodiment 1, light source device 20a according to embodiment 2 has a first feature in that the light emitted from laser light sources 1a and 1b is blue light of a first polarization (for example, P-polarized light). A second feature is that color wheel 19a is a magenta color wheel. Light source device 20a according to embodiment 2 is configured so that the light emitted from laser light sources 1a and 1b is P-polarized blue light, and the P-polarized blue light is transmitted through dichroic mirror 6.

[0039] The laser light sources 1a and 1b are rectangular elements, for example, as shown in FIG. 4B , in which the polarization direction of the emitted light (linearly polarized light) is parallel to the short side. In this case, to shorten the length L of the light source device 20a in the X direction, it is desirable to arrange the laser light sources 1a and 1b so that the short side is in the X direction. In this case, the polarization direction of the light emitted from the laser light sources 1a and 1b is the X direction. The polarization direction of the excitation light 5a, which is light reflected and combined by the mirrors 3a and 3b, is the Y direction, and the vibration plane of the excitation light 5a is parallel to the plane (XY plane) determined by the incident light and reflected light of the dichroic mirror 6, so this light is P-polarized (first polarization) at the dichroic mirror 6.

[0040] The phosphor wheel 10 is placed at a position where the excitation light 5a transmitted through the dichroic mirror 6 is incident. Here, the dichroic mirror 6 is a dichroic mirror that transmits blue light and reflects fluorescence. The dichroic mirror 6 may have a higher transmittance for blue light of the first polarized light (P-polarized light) than for blue light of the second polarized light (S-polarized light). When manufacturing a dichroic mirror, it is easier to make the transmittance for P-polarized light higher than that for S-polarized light.

[0041] On the other hand, some conventional light source devices have a configuration in which S-polarized blue light is reflected by a dichroic mirror. That is, S-polarized light is used as the blue light instead of P-polarized light, and the dichroic mirror 6 is a dichroic mirror that reflects blue light and transmits fluorescent light. In this case, the reflectance of the dichroic mirror for S-polarized blue light is often higher than that of P-polarized blue light. When manufacturing a dichroic mirror, it is easier to make the reflectance of S-polarized light higher than that of P-polarized light. Furthermore, in this configuration, the phosphor wheel is installed at a position where the S-polarized reflected light from the dichroic mirror 6 enters.

[0042] In the case of using a configuration in which S-polarized light is reflected by a dichroic mirror in the light source device 20, FIG. 4A shows a perspective view of the phosphor wheel 10a, assuming that the phosphor wheel is installed at a position where S-polarized reflected light from the dichroic mirror 6 is incident. In this case, the phosphor wheel 10a interferes with the laser light source 1a, its holding mechanism, cooling members, etc., so it is necessary to retract the excitation light source consisting of the laser light source 1a and the lens 2a in the X direction. This increases the length L in the X direction. Furthermore, in order to emit S-polarized light, the laser light sources 1a and 2b must be positioned with their long sides aligned in the X direction, further increasing the length L in the X direction. Therefore, by using P-polarized blue light as transmitted light as described above, it is possible to achieve high brightness while saving space compared to a configuration in which S-polarized blue light is reflected by the dichroic mirror 6.

[0043] In the above-described configuration in which P-polarized blue light is transmitted through the dichroic mirror 6, the efficiency of the dichroic mirror is lower than in the conventional configuration in which S-polarized blue light is reflected by the dichroic mirror. As a result, blue light 5a, which is excitation light, is reflected by the dichroic mirror 6 and becomes backlight 5b that travels back through the first relay optical system 22, and is reflected by the back surface of the phosphor wheel, increasing the amount of return light 5c that is mixed with the fluorescent light.

[0044] FIG. 4C is a schematic perspective view showing the configuration of the magenta color wheel 19a in FIG. 4A. In this light source device 20a, the color wheel 19a is a magenta color wheel having a magenta segment 34 that transmits blue and red light and a colorless segment 36 that transmits all colored light. The rotation of the magenta color wheel 19a is synchronized with the rotation of the phosphor wheel 10. As described above, the yellow fluorescent light generated in the phosphor region 13a of the phosphor wheel 10 may contain not only yellow light but also red light. In this case, only the red light contained in the yellow fluorescent light is transmitted through the magenta segment 34, resulting in the extraction of red light. Meanwhile, the fluorescence 18 generated by the other phosphor regions 13a and 13b of the phosphor wheel 10, and the blue light 5a that passes through the aperture 14 and is combined by the dichroic mirror 6 via the first relay optical system 22, are transmitted directly through the colorless segment 36. This allows the light of each color to be arranged in chronological order.

[0045] <Two Color Modes Implemented by Phase Shifting> FIG. 5 is a schematic diagram illustrating two color modes realized by phase shifting using the magenta color wheel of FIG. 4C . Two color modes are explained below, realized by phase shifting using the magenta color wheel 19a, and by arranging each color along two different time series. The phosphor wheel 10 shown in FIG. 5( a) has, similar to FIG. 3A , a phosphor region 13a that generates yellow fluorescence Ye, a phosphor region 13b that generates green fluorescence G, and an opening 14 that allows blue excitation light B to pass through. The phosphor region 13a that generates yellow fluorescence Ye occupies the left semicircular portion, the phosphor region 13b that generates green fluorescence G occupies the upper right quarter, and the opening 14 occupies the lower right quarter. The above area ratio is not limited to this, and may be set to any appropriate area ratio. FIG. 5( b) is a diagram illustrating the time series arrangement of fluorescence and blue excitation light output by the rotation of the phosphor wheel 10. 5B, as the phosphor wheel rotates, the lights are output in the order G, Ye, B, and G in time series. In this case, when the phosphor wheel rotates for a fixed time, each light is output for a time width corresponding to the area ratio on the phosphor wheel 10.

[0046] FIG. 5( c ) illustrates two color modes in which the position of the magenta segment 34 of the magenta color wheel 19 a corresponds to the positions of the phosphor regions 13 a and 13 b of the phosphor wheel 10 in FIG. 5( a ). The left side of FIG. 5( c ) illustrates color mode 1, in which the magenta segment 34 is located in the lower left quarter, corresponding to half of the phosphor region 13 a of the phosphor wheel 10 that produces yellow fluorescence Ye. On the other hand, the right side of FIG. 5( c ) illustrates color mode 2, in which the magenta segment 34 is located across both the phosphor region 13 a that produces yellow fluorescence Ye and the aperture 14. The positions of the left and right magenta segments 34 in FIG. 5( c ) can be adjusted as needed. FIG. 5( d ) illustrates the time ranges of filtering of the magenta segments corresponding to the two left and right color modes in FIG. 5( c ).

[0047] Fig. 5(e) is a diagram showing the time series of output light 40a, 40b as a pie chart with time indicated in the circumferential direction, with the left side being a pie chart of output light 40a corresponding to color mode 1 in Fig. 5(c) and the right side being a pie chart of output light 40b corresponding to color mode 2. Fig. 5(f) is a diagram showing the time series of output light with time indicated on the horizontal axis, with the upper side corresponding to color mode 1 in Fig. 5(c) and the lower side corresponding to color mode 2.

[0048] In color modes 1 and 2, red fluorescence R contained in the yellow fluorescence corresponding to the magenta segments 34 of the light from the phosphor wheel 10 is extracted, and the yellow fluorescence is reflected and replaced with red fluorescence R. The difference between color modes 1 and 2 lies in the number of intersections between the magenta segments 34 and the yellow fluorescence Ye from the phosphor wheel 10. Color mode 1 is a mode used when a vivid image is displayed with a high red luminance ratio, and is also called a color-priority mode. Color mode 2 is a mode used when a bright image is displayed with a high yellow luminance ratio, and is also called a brightness-priority mode.

[0049] When using this magenta color wheel 19a, because blue and red light are transmitted through the magenta segment 34, the light traveling backward through the first relay optical system 22 is reflected by the rear surface of the phosphor wheel, and the blue light returning from the reflected light may be mixed with the fluorescent light, which may cause problems. For example, for each color of output light in FIG. 5(f), the mixed color of the blue light returning from the reflected light is represented as "+B." In particular, problems may occur when blue light is mixed with red light.

[0050] As in the first embodiment, this light source device 20a also has a diffusion layer on the back surface of the phosphor wheel 10 that diffuses blue light (reverse light) 5b that reaches the back surface of the phosphor wheel 10 after blue light 5a, which is excitation light from the laser light sources 1a and 1b, is reflected by the dichroic mirror 6. This can suppress return light 5c caused by reflection of the reverse light 5b on the back surface of the phosphor wheel 10, thereby preventing the return light 5c from mixing with the fluorescent light. This allows each color to be emitted with high color purity.

[0051] (Variation 1) FIG. 6A is a schematic diagram showing the magenta segments 34 and the achromatic segments 36 of the magenta color wheel 19a in color mode 1. FIG. 6B is a schematic diagram showing the light-processing region 15 on the back side of the phosphor wheel 10a in a light source device according to Variation 1. The light source device according to Variation 1 is characterized in that the light-processing region 15 on the back side of the phosphor wheel 10b is provided in a location corresponding to the magenta segments 34 of the magenta color wheel 19a. As described above, the mixing of blue light into red light is particularly problematic. Therefore, by providing the light-processing region (diffusion layer) 15 on the back side of the phosphor wheel 10a corresponding to the magenta segments 34 as described above, mixing of blue light with the returning light into the red light can be suppressed. This allows each color to be emitted with high color purity.

[0052] (Variation 2) FIG. 7A is a schematic plan view showing a state in which fins are provided on the back side (other surface) of the phosphor wheel 10b of the light source device according to Variation 2. FIG. 7B is a schematic cross-sectional view showing how blue light (reverse light) 5b, which is reflected by the dichroic mirror 6 and reaches the back side of the phosphor wheel 10b, enters between the fins 12 in FIG. 7A and is repeatedly reflected by the side surfaces 12a and bottom surface 12b of the fins 12. As shown in FIG. 7A, the phosphor wheel 10b of the light source device according to Variation 2 has fins 12 on the back side. As described above, the fins 12 are provided to enhance cooling performance. The fins 12 may be formed integrally with the substrate of the phosphor wheel 10b. Multiple fins 12 may be provided. Furthermore, the fins 12 do not have to be provided on the entire back side, but may be provided on a portion, for example, a portion corresponding to the phosphor region on the front side. The fins 12 may be straight, curved, or a combination of these. Furthermore, from the viewpoints of cooling performance, air resistance reduction, and noise reduction, the fins may be provided point-symmetrically with respect to the center of the substrate of the phosphor wheel 10b. Furthermore, a diffusion layer may be provided on the side of the fins 12. A diffusion layer may be provided on the bottom surface between the fins. Furthermore, a diffusion layer may be provided on the top surface of the fins. The diffusion layer may be, for example, a finely textured surface formed by sandblasting. By providing fins on the back surface of the phosphor wheel 10b and providing diffusion layers on the side of the fins, the bottom surface between the fins, and the top surface of the fins, the blue light (reverse light) 5b reflected by the dichroic mirror 6 and reaching the back surface of the phosphor wheel 10b can be reflected by the back surface of the phosphor wheel 10b, resulting in a residual rate of approximately 10% of the return light 5c. Incidentally, when fins are not provided and a diffusion layer is not provided as in the prior art, the residual rate of the return light 5c is approximately 40%. In contrast, when a fin is not provided and a diffusion layer is provided, as in the light source device according to embodiment 1, the residual rate of the returned light is about 20%, and the residual rate of the returned light 5c can be reduced to approximately 30% or less. The light source device according to modification 2 has the excellent effect of being able to further reduce the residual rate of the returned light.

[0053] As shown in FIG. 7B , when fins 12 are present, blue light 5b that reaches the back surface of phosphor wheel 10b after being reflected by dichroic mirror 6 is incident on bottom surface 12b, side surface 12a, and top surface 12c of the fin. When fins 12 have sandblasted side surfaces 12a and bottom surface 12b, blue light 5b incident on bottom surface 12b between fins 12 is diffusely reflected, and a portion of this diffusely reflected light is incident on one side surface 12aa of fin 12 and then diffusely reflected. Furthermore, a portion of this diffusely reflected light is incident on the other side surface 12ab and bottom surface 12b of fin 12 and then diffusely reflected. In this way, between fins 12, diffuse reflection is repeated frequently on side surfaces 12a and 12b of fin 12. Of course, light that is incident on bottom surface 12b and then diffusely reflected on side surface 12ab, and light that is incident on side surface 12aa and side surface 12ab without passing through bottom surface 12b, is also diffusely reflected repeatedly. For this reason, the light source device according to Variation 2, which includes a phosphor wheel having sandblasted fins 12, is considered to be more effective in reducing blue light reflected from the rear surface than a device without sandblasting fins. If the top surfaces 12c of the fins are also sandblasted, light incident on the top surfaces 12c of the fins is also diffusely reflected. Note that the material of the fins absorbs some light, so it is considered that an additional effect is that the reflected blue light 5b is further absorbed as it is repeatedly incident on and diffusely reflected by the side surfaces 12a and bottom surfaces 12b of the fins 12.

[0054] To enhance the cooling performance of the phosphor wheel 10, the substrate 11 may be a metal plate, and a microtexture structure may be formed on the back surface of the substrate 11 by plating (electrodepositing), etching, applying a protective film, laser processing, or the like. The microtexture structure may be appropriately designed to function as a light diffusion layer. Such a microtexture structure can be provided even if fins are present or after sandblasting.

[0055] (Embodiment 3) <Projection-type image display device> Fig. 8 is a schematic diagram showing the configuration of a projection-type image display device 30 using the light source device 20, 20a according to embodiment 1 or 2. Note that the configurations of the light source device 20, 20a according to embodiments 1 and 2 have been described above, so a description thereof will be omitted here, and the output light after emission from the light source device 20, 20a will be described.

[0056] Light emitted from light source devices 20, 20a enters total reflection prism 24 via second relay lens system 23. The light that enters total reflection prism 24 enters a minute gap in total reflection prism 24 at an angle equal to or greater than the total reflection angle, and is reflected, changing the direction of travel of the light before entering DMD 26. DMD 26 changes the direction of travel of the light by changing the direction of the micromirrors in response to a signal from a video circuit (not shown), in synchronization with the output light emitted by the combination of phosphor wheels 10, 10a, 10b and color filters 19, 19a, and then emits the light.

[0057] The light whose direction of travel has been changed in response to the video signal by the DMD 26 enters the tiny gap of the total reflection prism 24 at an angle less than the total reflection angle, passes through it as is, enters the projection lens 28, and is projected onto a screen not shown.

[0058] It should be noted that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and can achieve the effects of each embodiment and / or example.

[0059] According to the light source device of the present disclosure, the back surface of the phosphor wheel has a light processing region (diffusion layer) that diffuses the blue light (retrograde light) that reaches the back surface of the phosphor wheel after blue light, which is excitation light from a laser light source, is reflected by a dichroic mirror. Therefore, it is possible to suppress return light caused by the reflection of the blue light (retrograde light) on the back surface of the phosphor wheel, and as a result, it is possible to suppress the return light from mixing with the fluorescent light, making the light source device useful as a light source device for use in a projection-type image display device that can emit each color with high color purity.

[0060] REFERENCE SIGNS 1a, 1b Laser light source 2a, 2b Lens 3a, 3b Mirror 4a Concave lens 4b Diffuser 5a Blue light as excitation light 5b Blue light reflected by dichroic mirror (retrograde light) 5c Blue light reflected by the back surface of phosphor wheel (return light) 6 Dichroic mirror 7 Lens 8a, 8b, 8c Mirror 9a, 9b, 9c Lens 10, 10a Phosphor wheel 11 Substrate 12 Fin 12a, 12aa, 12ab Side surface 12b Bottom surface 12c Top surface 13 Phosphor region 13a Phosphor region (yellow) 13b Phosphor region (green) 14 Opening 15 Light processing region (diffusion layer) 16a, 16b Lens 17 Mirror 18 Fluorescence 19, 19a Color wheel 20, 20a Light source device 21 Rod 22 First relay optical system 23 Second relay optical system 24 Total reflection prism 26 DMD 28 Projection lens 30 Projection type image display device 32 Motor mounting hole 34 Magenta segment 36 Achromatic segment 40 Output light

Claims

1. The device includes an excitation light source, a phosphor wheel, a light guide optical system, and a color wheel, The phosphor wheel is A substrate; a phosphor region provided on one surface of the substrate and having a phosphor that converts light from the excitation light source into fluorescence; a light processing region provided on the other surface of the substrate at a position corresponding to the phosphor region; an opening provided across the one surface of the substrate from the other surface; a drive device that rotates the substrate; having Light source device.

2. The light-guiding optical system comprises: a light source for guiding a majority of the light from the excitation light source to the one surface of the phosphor wheel, and generating a composite light by combining the transmitted light that has passed through the opening with the fluorescent light; At the same time, the remainder of the light from the excitation light source propagates through the light-guiding optical system in a direction different from that of the transmitted light without passing through the opening of the phosphor wheel, and becomes retrograde light that reaches the other surface of the phosphor wheel; the light processing area has a diffusion layer that diffuses and reflects the backlight, The color wheel is provided at a position where the combined light is incident. The light source device according to claim 1 .

3. 2. The light source device according to claim 1, wherein the color wheel has a filter that transmits red light and blue light and reflects other light.

4. 4. The light source device according to claim 3, wherein the phosphor wheel has a diffusion layer on the other surface, which is a rear surface of the phosphor region corresponding to the filter on the one surface.

5. The light source device according to claim 1 , wherein the diffusion layer has a fine uneven structure.

6. the excitation light source emits blue light of a first polarization; a dichroic mirror serving as the light combining element, the dichroic mirror being disposed between the excitation light source and the phosphor wheel and transmitting the blue light and reflecting the fluorescent light; the dichroic mirror has a higher transmittance for the first polarized blue light than for the second polarized blue light having a polarization direction different from that of the first polarized blue light; The light source device according to claim 1 .

7. the first polarization is P polarization and the second polarization is S polarization; The light source device according to claim 6 .

8. the phosphor wheel has a plurality of fins on the other surface, which is a back surface of the phosphor region corresponding to the filter, on the one surface; The diffusion layer is provided on the side surface of the fin and on the bottom surface between the fins. The light source device according to claim 4 .

9. The light source device according to claim 8 , wherein the diffusion layer is also provided on the top surfaces of the fins.

10. A projection-type image display device comprising the light source device according to claim 1 .