Light source device and projection-type image display device

Abstract

This light source device comprises: a light source; and a wavelength conversion element that has a first phosphor layer which is composed of a first phosphor that converts the wavelength of excitation light from the light source into first fluorescence, and a second phosphor layer which is composed of a second phosphor that converts the wavelength of a part of the first fluorescence or the excitation light into second fluorescence. The ratio of the amount of the first fluorescence at a second temperature higher than a first temperature to the amount of the first fluorescence at the first temperature from the first phosphor included in the first phosphor layer is greater than the ratio of the amount of the second fluorescence at the second temperature to the amount of the second fluorescence at the first temperature from the second phosphor included in the second phosphor layer.

Description

Light source device and projection type video display device

[0001] The present disclosure relates to a light source device and a projection type video display device.

[0002] Conventionally, as a component of a projection type video display device such as a projector, a wavelength conversion element that converts the wavelength of light from a light source and outputs the wavelength-converted light has been used. For example, Patent Document 1 discloses a light source device including a wavelength conversion element, a ratio acquisition unit, and a control unit. The wavelength conversion element converts a part of the light beam from the light source into converted light having a wavelength different from that of the light beam from the light source and emits it, and also emits non-converted light having the same wavelength as the light beam from the light source. Then, the ratio acquisition unit acquires a conversion light ratio that is the ratio of the intensity of the non-converted light to the intensity of the converted light. And the control unit controls the temperature of the wavelength conversion element based on the result acquired by the ratio acquisition unit.

[0003] Japanese Patent Application Laid-Open No. 2017-134181

[0004] The present disclosure has been devised in view of the above-described conventional circumstances, and an object thereof is to suppress an increase in the temperature of the wavelength conversion element.

[0005] The present disclosure provides a light source device including a light source, a first phosphor layer configured to include a first phosphor that wavelength-converts excitation light from the light source into first fluorescence, and a second phosphor layer configured to include a second phosphor that wavelength-converts a part of the excitation light or the first fluorescence into second fluorescence, and a wavelength conversion element having the second phosphor layer, wherein a ratio of the amount of the first fluorescence at a second temperature higher than the first temperature to the amount of the first fluorescence at the first temperature of the first phosphor included in the first phosphor layer is larger than a ratio of the amount of the second fluorescence at the second temperature to the amount of the second fluorescence at the first temperature of the second phosphor included in the second phosphor layer.

[0006] Furthermore, this disclosure provides a projection-type image display device having a light source device, the wavelength conversion element comprising: a light source; a first phosphor layer comprising a first phosphor that wavelength-converts excitation light from the light source into a first fluorescence; and a second phosphor layer comprising a second phosphor that wavelength-converts the excitation light or a portion of the first fluorescence into a second fluorescence, wherein the ratio of the amount of light of the first fluorescence at a second temperature higher than the first temperature to the amount of light of the first fluorescence at a first temperature of the first phosphor contained in the first phosphor layer is greater than the ratio of the amount of light of the second fluorescence at a second temperature to the amount of light of the second fluorescence at a first temperature of the second phosphor contained in the second phosphor layer.

[0007] Furthermore, any combination of the above components, as well as any conversion of the expressions of this disclosure between methods, apparatus, systems, etc., are also valid as aspects of this disclosure.

[0008] According to this disclosure, it is possible to suppress the temperature rise of the wavelength conversion element.

[0009] Schematic diagram showing an example configuration of a light source device according to Embodiment 1 Front view showing an example configuration of a phosphor wheel according to Embodiment 1 Cross-sectional diagram showing the AA cross-section of the phosphor wheel according to Embodiment 1 Graph showing the temperature characteristics of the phosphor wheel according to Embodiment 1 Cross-sectional diagram showing the cross-section of a phosphor wheel according to Modification 1 of Embodiment 1 Schematic diagram showing an example configuration of a light source device according to Embodiment 2 Schematic diagram showing an example configuration of a light source device according to Embodiment 3 Front view showing an example configuration of a phosphor wheel according to Embodiment 3 Cross-sectional diagram showing the BB cross-section of the phosphor wheel according to Embodiment 3 Front view showing an example configuration of a color wheel according to Embodiment 3 Schematic diagram showing an example configuration of a light source device according to Embodiment 4 Schematic diagram showing an example configuration of a light source device according to Embodiment 5 Front view showing an example configuration of a color wheel according to Embodiment 5 Front view showing an example configuration of a phosphor wheel according to Embodiment 5 Schematic diagram showing an example configuration of a projection-type video display device including a light source device according to Embodiment 1 Schematic diagram showing an example configuration of a projection-type video display device including a light source device according to Embodiment 2 Schematic diagram showing an example configuration of a projection-type video display device including a light source device according to Embodiment 3

[0010] (Background to this Disclosure) A phosphor wheel equipped with a phosphor layer is an example of a wavelength conversion element used in projection-type image display devices such as projectors. The phosphor converts excitation light from a light source into fluorescence of a different wavelength than the excitation light. The temperature of the phosphor provided in the phosphor wheel rises due to the incidence of excitation light from the light source. The conversion efficiency of the phosphor decreases with increasing temperature. Furthermore, if the temperature of the phosphor continues to rise, quality problems such as burnout may occur. Therefore, it is necessary to suppress the temperature rise of the phosphor, or more precisely, the phosphor wheel containing the phosphor.

[0011] However, directly measuring the temperature of a phosphor can be difficult. Furthermore, even if the ambient temperature around the phosphor is measured, there may be a time lag between the measurement result and the actual temperature change of the phosphor. Patent Document 1 adjusts the rotation speed of the phosphor wheel motor based on a ratio that shows the balance between light converted by the phosphor, i.e., fluorescence, and light that was not converted, thereby adjusting the temperature of the phosphor. When estimating the temperature of a phosphor using a ratio that shows the balance between fluorescence and light that was not converted, in other words, the conversion efficiency, after the phosphor temperature exceeds the threshold temperature at which the conversion efficiency begins to decline, the conversion efficiency drops sharply, and the phosphor temperature also rises sharply, which can lead to the following situation: That is, the temperature at which the conversion efficiency of the phosphor declines and the temperature at which quality problems such as burnout occur are close together, and there may not be enough time to provide some kind of feedback for adjusting the phosphor temperature after detecting the decline in conversion efficiency. Here, in order to increase the temperature difference between the temperature at which the conversion efficiency of the phosphor declines and the temperature at which quality problems occur (the upper limit of usable temperature), it is conceivable to raise the temperature at which the decline in conversion efficiency begins or to lower the upper limit of usable temperature. However, raising the temperature at which conversion efficiency begins to decline requires, for example, improving the conversion performance of the phosphor, but there may be limits to how much the conversion performance of the phosphor can be improved. Furthermore, this could lead to increased costs. Also, lowering the upper limit of usable temperature would require, for example, reducing the brightness of the light source device or projection-type image display device, which is undesirable from a practical standpoint.

[0012] Therefore, in the following embodiment, we will describe a technique for suppressing the temperature rise of a wavelength conversion element by early detection of a decrease in the conversion efficiency of the phosphor contained in the wavelength conversion element.

[0013] Hereinafter, embodiments specifically disclosing the light source device and projection-type image display device according to this disclosure will be described in detail, with appropriate reference to the attached drawings. However, unnecessarily detailed explanations may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding by those skilled in the art. The attached drawings and the following explanation are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0014] In the drawings, equivalent components are indicated by the same reference numeral. When describing the various embodiments shown in this specification, if a component included in each embodiment requires individual explanation, a subscript (a, b, ...) is added to the reference numeral. On the other hand, when a component is described in common, the subscript is omitted from the reference numeral.

[0015] Furthermore, in this specification, terms such as "first" and "second" are used merely to distinguish components for explanatory purposes and are not intended to be interpreted as limiting to any particular component. Therefore, these expressions should be understood to be appropriately reinterpreted depending on the configuration to which the invention relating to this disclosure applies.

[0016] Furthermore, each figure shows a three-dimensional coordinate system consisting of the x, y, and z axes, and the orientation of each axis is assumed to correspond to that of the other. In addition, the dimensions and arrangement of each layer in the figures described below are simplified for illustrative purposes and are not intended to be interpreted restrictively unless otherwise specified.

[0017] One embodiment of the light source device according to this disclosure is used, for example, in a projection-type image display device such as a projector. The control method for the light source device within the projection-type image display device may be a known method, and a detailed explanation is omitted here.

[0018] The following description will explain the light source device according to Embodiment 1 using Figures 1 to 5. The light source device according to Embodiment 2 will be explained using Figure 6. The light source device according to Embodiment 3 will be explained using Figures 7 to 10. The light source device according to Embodiment 4 will be explained using Figure 11. The light source device according to Embodiment 5 will be explained using Figures 12 to 14. Then, various examples of projection-type image display devices including the light source device will be explained using Figures 15 to 17. Note that the light source device according to one embodiment of this disclosure includes a phosphor wheel as a wavelength conversion element. Furthermore, the light source devices according to Embodiment 3, Embodiment 4, or Embodiment 5 include a color wheel, which is a time-division wavelength selector, as a wavelength selector. Details will be described later. Furthermore, the combination of the light source device and the projection-type image display device may be arbitrary, except where specifically limited below. Therefore, the configuration examples and combinations described below are just examples and are not limiting. Moreover, the phosphor wheel provided in the light source device according to one embodiment of this disclosure is an example of a wavelength conversion element, and the light source device may, for example, include a fixed-type wavelength conversion element. Similarly, the color wheel provided in the light source device according to Embodiment 3, Embodiment 4, or Embodiment 5 is an example of a wavelength-selective element, and the light source device may, for example, be equipped with a fixed-type wavelength-selective element.

[0019] [Light Source Device] <Embodiment 1> Figure 1 is a schematic diagram showing an example of the configuration of a light source device 10a according to Embodiment 1.

[0020] The light source device 10a is configured to continuously emit blue, green, and red light. The light source device 10a is a light source device suitable for projection-type image display devices that use a three-panel Digital Mirror Device (hereinafter referred to as "DMD"), which will be described later.

[0021] The light source device 10a is composed of an excitation light optical system, a fluorescence illumination system, a blue light optical system, an integrator illumination system, and a fluorescence separation illumination system.

[0022] The excitation light optical system of the light source device 10a is composed of a plurality of laser diode light sources 11, a plurality of collimator lenses 12 corresponding to each of the plurality of laser diode light sources 11, a convex lens 13, a diffuser plate 14, a concave lens 15, a dichroic mirror 16a, a convex lens 17, and a convex lens 18.

[0023] The fluorescent illumination system of the light source device 10a is composed of a phosphor wheel 19a, a convex lens 18, a convex lens 17, a dichroic mirror 16a, a separated dichroic mirror 25a, and a convex lens 27.

[0024] The blue optical system of the light source device 10a is composed of a plurality of laser diode light sources 20, a plurality of collimator lenses 21 corresponding to each of the plurality of laser diode light sources 20, a convex lens 22, a diffuser plate 23, a concave lens 24, a dichroic mirror 16a, a separated dichroic mirror 25a, and a convex lens 27.

[0025] The integrator illumination system of the light source device 10a is configured to include a rod integrator 28.

[0026] The fluorescent separation illumination system of the light source device 10a consists of a convex lens 18, a convex lens 17, a dichroic mirror 16a, a separation dichroic mirror 25a, and a sensor 26.

[0027] First, the excitation light optics of the light source device 10a will be described. The blue wavelength excitation light emitted from each of the multiple laser diode light sources 11 is collimated by multiple collimator lenses 12, each of which is provided in relation to each of the multiple laser diode light sources 11. The collimated blue light is incident on a subsequent convex lens 13 to reduce its beam width, and is then incident on a subsequent diffuser plate 14 to diffuse it, improving the uniformity of the light. The blue light that has been incident on the diffuser plate 14 and diffused is then incident on a subsequent concave lens 15 to be made into a parallel beam. The blue light made into a parallel beam by the concave lens 15 is then incident on a dichroic mirror 16a, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0028] The dichroic mirror 16a transmits excitation light in the blue wavelength range from the laser diode light source 11 and reflects the fluorescence emitted by the phosphor wheel 19a, which will be described later, after wavelength conversion of the excitation light from the laser diode light source 11.

[0029] The blue wavelength light from the laser diode light source 11 that is incident on the dichroic mirror 16a passes straight through the dichroic mirror 16a and then passes through the subsequent convex lenses 17 and 18 to be focused onto the phosphor wheel 19a.

[0030] Next, the phosphor wheel 19a will be described with reference to Figures 2 and 3. Figure 2 is a front view showing an example of the configuration of the phosphor wheel 19a according to Embodiment 1.

[0031] The phosphor wheel 19a is composed of a substrate 100a to which the motor 120 is attached, a plurality of phosphor layers, and a reflective layer 110.

[0032] The reflective layer 110 is provided on one side of the substrate 100a in an annular shape at the same distance from the center of rotation of the substrate 100a. Multiple phosphor layers are provided on the reflective layer 110. The phosphor layers are composed of two types of phosphors. Specifically, phosphor layer 101 is provided on the reflective layer 110, and phosphor layer 102 is provided on phosphor layer 101. Phosphor layers 101 and 102 are provided in an annular shape, similar to the reflective layer 110. Further details will be described later with reference to Figure 3.

[0033] The substrate 100a may be made of a material such as aluminum, which has excellent heat dissipation properties. However, the substrate 100a is not limited to aluminum and may be made of other metals. Furthermore, the substrate 100a may be a transmissive substrate such as glass or sapphire, or a transmissive substrate such as glass or sapphire may have a reflective region provided on it.

[0034] Figure 3 is a cross-sectional view showing the AA cross-section of the phosphor wheel 19a according to Embodiment 1.

[0035] The phosphor layer 101 is a mixed layer in which a phosphor that is excited by blue light from the laser diode light source 11 and emits wavelength-converted yellow (green and red) fluorescence is filled into a heat-resistant resin such as silicone or silsesquioxane. Specific examples of phosphors include yttrium (Y) and aluminum (Al) composite oxide phosphors, YAG, and Y ３ Al ５ O １２ These are some examples.

[0036] The phosphor layer 102 is provided on top of the phosphor layer 101 and is a mixed layer in which a phosphor that is excited by light in a certain wavelength range of the yellow (green and red) fluorescence converted by the phosphor layer 101 and emits wavelength-converted fluorescence is filled into a heat-resistant resin such as silicone or silsesquioxane. A specific example of a phosphor is Cr ３＋ Examples include composite oxide phosphors.

[0037] Referring to Figure 4, the temperature characteristics of the phosphors in phosphor layer 101 and phosphor layer 102 will be described. Figure 4 is a graph showing the temperature characteristics of the phosphor wheel 19a according to Embodiment 1. Characteristic 1000 shows the relationship between the temperature of the phosphor contained in phosphor layer 101 and the conversion efficiency (relative value) at each temperature, with the conversion efficiency at room temperature set to 1. Characteristic 2000 shows the relationship between the temperature of the phosphor contained in phosphor layer 102 and the conversion efficiency (relative value) at each temperature, with the conversion efficiency at room temperature set to 1. Hereafter, in order to avoid redundancy in the explanation, the phosphor contained in phosphor layer 101 may be simply referred to as phosphor layer 101, and the phosphor contained in phosphor layer 102 may be simply referred to as phosphor layer 102.

[0038] As shown in Figure 4, the conversion efficiency of the phosphor layer 102 begins to decrease at a lower temperature compared to the conversion efficiency of the phosphor layer 101. For example, the temperature at which the conversion efficiency of the phosphor layer 102 becomes 90% of its conversion efficiency at room temperature is temperature T2. In contrast, the temperature at which the conversion efficiency of the phosphor layer 101 becomes 90% of its conversion efficiency at room temperature is temperature T1, which is higher than temperature T2. Note that 90% of the conversion efficiency at room temperature is just one example and is not limited to this.

[0039] Here, let's assume that the usable temperature of the phosphor layer 101 is, for example, between temperature T3 and temperature T4. As shown in Figure 4, the decrease in the conversion efficiency of the phosphor layer 101 begins after the temperature of the phosphor layer 101 rises to around temperature T3. In this case, it is difficult to detect the decrease in the conversion efficiency of the phosphor layer 101 to understand that the temperature of the phosphor layer 101 is rising, and then to suppress the temperature rise of the phosphor wheel 19a. This is because, at temperatures below the upper limit of the usable temperature of the phosphor layer 101, such as temperature T3, the difference in conversion efficiency is small, making it difficult to detect the difference in conversion efficiency. Conversely, at temperatures above temperature T3, the conversion efficiency decreases rapidly, so there is insufficient time and temperature margin to detect the decrease in conversion efficiency, perform processing to suppress the temperature rise, and return to below temperature T3. On the other hand, the decrease in the conversion efficiency of the phosphor layer 102 is easier to detect compared to the decrease in the conversion efficiency of the phosphor layer 101. More precisely, a decrease in the conversion efficiency of the phosphor layer 102 is easier to detect at lower temperatures compared to a decrease in the conversion efficiency of the phosphor layer 101. By detecting a decrease in the conversion efficiency of the phosphor layer 102, it is possible to detect that the temperature of the phosphor layer 102 is rising. When the temperature rise of the phosphor layer 102 is detected, the temperature rise of the phosphor layer 101 is also detected. Note that the usable temperature of the phosphor layer 101 described above is just an example for illustrative purposes and is not limited to this.

[0040] The ratio of the amount of the first fluorescence at a second temperature (e.g., temperature T3) higher than the first temperature to the amount of the first fluorescence at the first temperature (e.g., temperature T4) of the first phosphor contained in the phosphor layer 101 is defined as the first ratio. Also, the ratio of the amount of the second fluorescence at the second temperature to the amount of the second fluorescence at the first temperature of the second phosphor contained in the phosphor layer 102 is defined as the second ratio. In this case, the second ratio is smaller than the first ratio (the first ratio is larger than the second ratio). This is because, as described above, the decrease in conversion efficiency is more remarkable in the phosphor layer 102 than in the phosphor layer 101. Note that the above first temperature and second temperature are temperatures within the actual use range of the product (light source device or projection-type video display device having the light source device). The temperature within the actual use range of the product may be, for example, between room temperature (e.g., 25°C) and 150°C, which is an example of the heat-resistant temperature of silicone used for the wavelength conversion element (i.e., 25°C to 150°C).

[0041] Returning to the description with reference to FIG. 3, as described above, the excitation light for exciting the phosphor layer 102 preferably includes light in a partial wavelength range of the yellow (green and red) fluorescence from the phosphor layer 101. However, it is not limited thereto, and the excitation light for exciting the phosphor layer 102 may be the excitation light from the laser diode light source 11. Alternatively, the excitation light for exciting the phosphor layer 102 may be light in a wavelength range not used as image light in the projection-type video display device having the light source device 10a. Specifically, light in the wavelength range between green and red can be given as an example.

[0042] Also, the fluorescence from the phosphor layer 102 may be light in the infrared wavelength range, or may be light in the wavelength range between green and red, which is finally cut and rarely used.

[0043] Also, the phosphor layer 101 or the phosphor layer 102 may be formed of a sintered body of phosphor particles and configured to form a part of an annular shape, or may be a combination of a sintered body and a mixed layer.

[0044] Furthermore, in the description herein, a configuration in which the phosphor layer 102 is provided on the phosphor layer 101 has been exemplified, but the present invention is not limited thereto. For example, as shown in Modification 1 described later, the phosphor layer 102 may be provided between the phosphor layer 101 and the reflective layer 110. Also, the phosphor layer 102 may be a mixed layer in which phosphors contained in the phosphor layer 101 and phosphors contained in the phosphor layer 102 are mixed and filled in a heat-resistant resin such as silicone or silsesquioxane.

[0045] The fluorescence emitted after wavelength conversion by the phosphor layer 102 is not used as the emitted light of the light source device 10a. Since the temperature of the phosphor layer increases as the thickness of the phosphor layer increases, it is desirable that the thickness t2 of the phosphor layer 102 is thinner than the thickness t1 of the phosphor layer 101.

[0046] The reflective layer ********** filled with high-reflectivity particles. The particles filled in the reflective layer 110 are not limited to high-reflectivity particles, and high thermal conductivity particles may also be filled therein. The reflective layer 110 may be a mixed layer in which not only the reflectivity but also the thermal conductivity is improved.

[0047] Next, the behavior of the light condensed on the phosphor layer 102 will be described. As shown in FIG. 3, the phosphor layer 101 and the phosphor layer 102 are formed on the reflective layer 110 formed on the surface of the substrate 100a.

[0048] The light from the laser diode light source 11 first enters the phosphor layer 102. As described above, the phosphor layer 102 is configured to include a phosphor that is excited by light in a partial wavelength range of the yellow (green and red) fluorescence from the phosphor layer 101 and emits wavelength-converted fluorescence. Therefore, the phosphor layer 102 is hardly excited by the light from the laser diode light source ********** hereinafter, the phosphor layer 102 is assumed not to be excited by the light from the laser diode light source 11.

[0049] It should be noted that there is an unclear part in the original text of which is marked with **********, please check and provide the complete correct content for a more accurate translation.Light from the laser diode light source 11 passes directly through the phosphor layer 102 and enters the phosphor layer 101. The light from the laser diode light source 11 that enters the phosphor layer 101 is wavelength-converted and emitted from the phosphor layer 101 as yellow fluorescence, which is a mixture of green and red light. Due to complete diffusion, the wavelength-converted yellow (green and red) fluorescence is emitted both on the substrate 100a side and on the phosphor layer 102 side.

[0050] Of the light from the laser diode light source 11, the light that is not wavelength-converted by either the phosphor layer 101 or the phosphor layer 102, and the fluorescence that is wavelength-converted by the phosphor layer 101 and emitted towards the substrate 100a, are reflected by the reflective layer 110, change direction of propagation, and emitted towards the phosphor layer 101.

[0051] Light from the laser diode light source 11, reflected by the reflective layer 110, is wavelength-converted by the phosphor layer 101 and emitted from the phosphor layer 101 as yellow fluorescence, which is a mixture of green and red light. Due to complete diffusion, fluorescence is emitted from the phosphor layer 101 to both the substrate 100a side and the phosphor layer 102 side. Of this fluorescence, the fluorescence emitted to the substrate 100a side is reflected back to the phosphor layer 101, so the following explanation will focus on the light from the laser diode light source 11 and the fluorescence emitted to the phosphor layer 102 side.

[0052] For the sake of explanation, the fluorescence emitted after wavelength conversion in the phosphor layer 101 will be referred to as the first fluorescence, and the fluorescence emitted after wavelength conversion in the phosphor layer 102 will be referred to as the second fluorescence. The first fluorescence includes green light and red light.

[0053] The phosphor layer 102 is excited by light in the wavelength range between green and red, for example, and has the characteristic of wavelength-converting said light to a second fluorescence. Therefore, light from the laser diode light source 11 emitted from the phosphor layer 101, which is not wavelength-converted, passes directly through the phosphor layer 102. For the sake of simplicity, the following explanation assumes that the light from the laser diode light source 11, i.e., the excitation light, is not wavelength-converted by the phosphor layer 102, but it is not limited to this. It is desirable that the phosphor layer 102 is not excited by light from the laser diode light source 11, but this does not exclude the case in which the phosphor layer 102 is excited by light from the laser diode light source 11.

[0054] Furthermore, of the yellow first fluorescence emitted from the phosphor layer 101, light in the wavelength range between green and red, for example, is wavelength-converted into second fluorescence in the phosphor layer 102, while light in other wavelength ranges passes through the phosphor layer 102 as is. The second fluorescence emitted from the phosphor layer 102 is also emitted towards the substrate 100a side for complete diffusion, but passes through the phosphor layer 101 without wavelength conversion, is reflected by the reflective layer 110, and then transmits through the phosphor layer 101 again. As a result, the second fluorescence is emitted from the phosphor layer 102 toward the surface (positive z-axis direction). The behavior of the second fluorescence after emission from the phosphor layer 102, the light from the laser diode light source 11 that was not wavelength-converted, and the first fluorescence that passed through the phosphor layer 102 as is will be described later in the explanation of the fluorescence illumination system.

[0055] Next, the behavior of the light whose wavelength has been converted by the phosphor wheel 19a in a fluorescent illumination system will be explained with reference to Figure 1.

[0056] The first and second fluorescence, which are wavelength-converted by the phosphor wheel 19a and emitted, are made into parallel light by the convex lens 18 and the convex lens 17, and incident on the dichroic mirror 16a, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0057] The dichroic mirror 16a transmits light in the blue wavelength range and reflects fluorescence, specifically the first and second fluorescence, which is excited and wavelength-converted by light from the laser diode light source 11 in the phosphor wheel 19a. Therefore, fluorescence incident on the dichroic mirror 16a is reflected, its direction of propagation is changed by 90 degrees, and it is incident on the separated dichroic mirror 25a, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0058] The separation dichroic mirror 25a transmits light in the blue wavelength range and has the characteristic of passing through the first fluorescence and reflecting the second fluorescence, which is excited and wavelength-converted in the phosphor wheel 19a by light from the laser diode light source 11, specifically the first fluorescence and the second fluorescence.

[0059] Of the first and second fluorescence from the phosphor wheel 19a that is incident on the separating dichroic mirror 25a, the first fluorescence passes through the separating dichroic mirror 25a, is incident on the subsequent convex lens 27, and is focused near the aperture of the rod integrator 28.

[0060] The behavior of the second fluorescence reflected by the separation dichroic mirror 25a will be described later in the explanation of the fluorescence separation illumination system.

[0061] This section describes the behavior of the second fluorescence, which is reflected by the separating dichroic mirror 25a and separated from the green and red light, in a fluorescence separation illumination system. The fluorescence separation illumination system consists of a separating dichroic mirror 25a and a sensor 26. The second fluorescence, which is reflected by the separating dichroic mirror 25a and separated, is incident on the subsequent sensor 26. The sensor 26 is provided with a circuit (not shown), which allows the sensor 26 to measure the light intensity of the second fluorescence. Hereinafter, the separating dichroic mirror may be referred to as the light separation means. Also, hereafter, the sensor 26 may be referred to as the light intensity measuring means.

[0062] Next, the blue optical system of the light source device 10a will be described. The blue optical system of the light source device 10a is composed of a plurality of laser diode light sources 20, a plurality of collimator lenses 21 corresponding to the plurality of laser diode light sources 20, a convex lens 22, a diffuser plate 23, a concave lens 24, a dichroic mirror 16a, a separated dichroic mirror 25a, and a convex lens 27.

[0063] Light emitted from each of the multiple laser diode light sources 20 is collimated by a collimator lens 21 corresponding to each laser diode light source 20 and incident on a subsequent convex lens 22. The light from the laser diode light sources 20 that is incident on the convex lens 22 is focused to reduce the beam width and incident on a subsequent diffuser plate 23. The light that is incident on the diffuser plate 23 and diffused is incident on a subsequent concave lens 24 and is made into a parallel beam. The light made into a parallel beam by the concave lens 24 is incident on a dichroic mirror 16a that is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0064] Since the dichroic mirror 16a transmits light in the blue wavelength range, the light from the laser diode light source 20 that is incident on the dichroic mirror 16a passes straight through the dichroic mirror 16a. The light from the laser diode light source 20 that has passed through the dichroic mirror 16a is incident on the decoupling dichroic mirror 25a. Since the decoupling dichroic mirror 25a transmits light in the blue wavelength range, the light from the laser diode light source 20 that is incident on the decoupling dichroic mirror 25a passes straight through the decoupling dichroic mirror 25a. The light from the laser diode light source 20 that has passed through the decoupling dichroic mirror 25a is incident on the convex lens 27 and is focused near the opening of the rod integrator 28.

[0065] The integrator illumination system of the light source device 10a is composed of a rod integrator 28. The rod integrator 28 emits uniform light as blue light, green light, and red light, which are focused near the opening of the rod integrator 28 by a convex lens 27, undergo multiple reflections inside the rod integrator 28.

[0066] Hereinafter, a phosphor layer that emits fluorescence (second fluorescence in this embodiment) excited by light in a specific wavelength range from fluorescence (first fluorescence in this embodiment) that has been wavelength-converted by another phosphor layer, such as phosphor layer 102, may be referred to as the second phosphor layer. Below the second phosphor layer, in other words, on the substrate 100a side, a phosphor layer that corresponds to the other phosphor layer and emits fluorescence (first fluorescence in this embodiment) in a different wavelength range excited by excitation light from the laser diode light source 11 may be referred to as the first phosphor layer. The first phosphor layer may be, for example, phosphor layer 101.

[0067] Furthermore, as described above, the phosphor wheel 19a is an example of a wavelength conversion element, which is an element that converts the wavelength of light from the laser diode light source 11.

[0068] In the light source device 10a according to Embodiment 1, the excitation light from the laser diode light source 11 is wavelength-converted in the phosphor layer 101, and the first fluorescence is emitted from the phosphor layer 101. Then, the phosphor layer 102 is excited by light in a certain wavelength range of the first fluorescence, and this light is wavelength-converted to the second fluorescence. The second fluorescence emitted from the phosphor layer 102 is then guided to the sensor 26 by the separation dichroic mirror 25a. The sensor 26 measures the light intensity of the second fluorescence. As explained with reference to Figure 4, the conversion efficiency of the phosphor layer 102 begins to decrease at a lower temperature than the conversion efficiency of the phosphor layer 101. Therefore, by detecting the change in the light intensity of the second fluorescence, or more precisely, the decrease in light intensity, using the sensor 26, it is possible to detect the temperature rise of the phosphor layer 102, and by extension, the phosphor layer 101 and the phosphor wheel 19a. Detection of the decrease in light intensity may be performed, for example, as follows. For example, the light source device 10a may include a determination unit (not shown) that stores a certain value for light intensity as a threshold. The determination unit may determine whether the light intensity measured by the sensor 26 is less than the certain value. If the determination unit determines that the light intensity measured by the sensor 26 is less than the certain value, it may further determine that the light intensity has decreased. This allows for the detection of a decrease in light intensity. Hereinafter, the determination unit may be referred to as the determination means.

[0069] Furthermore, with the configuration of this embodiment, it is possible to detect the temperature rise of the phosphor wheel 19a earlier compared to the case where the phosphor layer 102 is not provided on the phosphor wheel 19a. As a result, the light source device 10a can perform temperature suppression control to suppress the temperature rise of the phosphor wheel 19a. Examples of processes to suppress the temperature rise of the phosphor wheel 19a include adjusting the irradiation intensity of the excitation light from the laser diode light source 11, adjusting the rotation speed of the motor 120, and adjusting the intensity of a cooling fan (not shown). The light source device 10a may include a control unit (not shown). For example, the control unit may perform temperature suppression control to suppress the temperature rise of the phosphor wheel 19a when a determination unit (not shown) determines, based on the amount of light measured by the sensor 26, that the amount of light is less than a certain value. As an example, the control unit may be able to control the irradiation intensity of the excitation light from the laser diode light source 11. This suppresses the occurrence of problems related to the efficiency reduction and reliability of the light source device 10a. Furthermore, the second fluorescence may be, for example, infrared light, and may be light that is not used as image light in a projection-type image display device having a light source device 10a. This allows light that is not used as image light to be utilized for purposes such as suppressing the temperature rise of the phosphor wheel.

[0070] As described above, the light source device according to this embodiment (for example, light source device 10a) comprises a light source (for example, laser diode light source 11), a wavelength conversion element (for example, phosphor wheel 19a) having a first phosphor layer (for example, phosphor layer 101) comprising a first phosphor that wavelength-converts excitation light from the light source to a first fluorescence, and a second phosphor layer (for example, phosphor layer 102) comprising a second phosphor that wavelength-converts excitation light or a part of the first fluorescence to a second fluorescence, wherein the ratio of the amount of light of the first fluorescence at a second temperature higher than the first temperature to the amount of light of the first fluorescence at a first temperature of the first phosphor contained in the first phosphor layer is greater than the ratio of the amount of light of the second fluorescence at a second temperature to the amount of light of the second fluorescence at a first temperature of the second phosphor contained in the second phosphor layer.

[0071] In this configuration, the first phosphor layer can wavelength-convert excitation light into first fluorescence. The second phosphor layer can wavelength-convert excitation light or a portion of the first fluorescence into second fluorescence. The wavelength conversion element can emit light containing both the first and second fluorescence. Here, the ratio of the amount of light emitted by the first fluorescence at a second temperature (higher than the first temperature) to the amount of light emitted by the first phosphor in the first phosphor layer at a first temperature is greater than the ratio of the amount of light emitted by the second fluorescence at a second temperature to the amount of light emitted by the second phosphor in the second phosphor layer at a first temperature. In other words, the temperature at which the wavelength conversion efficiency of the second phosphor layer begins to decrease is lower than the temperature at which the wavelength conversion efficiency of the first phosphor layer begins to decrease. Therefore, the light source device can suppress the temperature rise of the first phosphor layer before the conversion efficiency of the first phosphor layer decreases significantly.

[0072] Furthermore, the light source device according to this embodiment further comprises: an optical separation means arranged in the optical path of light from the wavelength conversion element for separating the second fluorescence from the light from the wavelength conversion element; an optical intensity measuring means for measuring the amount of light of the second fluorescence separated by the optical separation means; and a determination means for determining whether the amount of light of the second fluorescence measured by the optical intensity measuring means is less than a certain value. With this configuration, the optical separation means of the light source device can separate the second fluorescence from the light from the wavelength conversion element. The optical intensity measuring means of the light source device can measure the amount of light of the separated second fluorescence. The determination means of the light source device can determine whether the amount of light of the second fluorescence measured by the optical intensity measuring means is less than a certain value. As a result, the light source device can detect when a decrease in the efficiency of wavelength conversion of the second phosphor layer occurs.

[0073] Furthermore, the light source device according to this embodiment further includes a control unit that performs temperature suppression control to suppress the temperature rise of the wavelength conversion element when the determination means determines that the amount of light from the second fluorescence measured by the light intensity measuring means is less than a certain value. With this configuration, when the determination means determines that the amount of light from the second fluorescence measured by the light intensity measuring means is less than a certain value, that is, when the determination means detects a decrease in the conversion efficiency of the second phosphor layer, the control unit of the light source device can suppress the temperature rise of the first phosphor layer and the wavelength conversion element by performing temperature suppression control, such as controlling the irradiation intensity of the excitation light.

[0074] Furthermore, in the light source device according to this embodiment, the second phosphor layer is provided on the first phosphor layer and is positioned on the side where the excitation light from the light source is incident on the wavelength conversion element. With this configuration, for example, the second phosphor layer can allow the excitation light to pass through without wavelength conversion. In this case, for example, the excitation light is wavelength-converted to the first fluorescence in the first phosphor layer. Then, the second phosphor layer wavelength-converts the excitation light or a portion of the first fluorescence to the second fluorescence, and the second fluorescence can be emitted from the wavelength conversion element.

[0075] Furthermore, in the light source device according to this embodiment, the thickness of the second phosphor layer (for example, thickness t2) is thinner than the thickness of the first phosphor layer (for example, thickness t1). With this configuration, the temperature rise of the second phosphor layer is suppressed, and consequently, the temperature rise of wavelength conversion elements such as phosphor wheels is suppressed.

[0076] Furthermore, in the light source device according to this embodiment, the second fluorescence is not used as image light. With this configuration, the second fluorescence, which is not used as image light, can be utilized to detect the temperature rise of the wavelength conversion element.

[0077] <Modification 1 of Embodiment 1> Figure 5 is a cross-sectional view showing a cross-section of the phosphor wheel 19a-1 according to Modification 1 of Embodiment 1. The phosphor wheel 19a-1 according to Modification 1 of Embodiment 1 differs from the phosphor wheel 19a according to Embodiment 1 in the arrangement of the phosphor layers 101 and 102, but is otherwise common to the original configuration. The explanation will focus on the changes from the phosphor wheel 19a according to Embodiment 1. Note that the phosphor wheel 19a-1 may be applied in place of a phosphor wheel in other embodiments and modifications in which the phosphor layer 102 is provided on top of the phosphor layer 101.

[0078] As shown in Figure 5, in the phosphor wheel 19a-1, the phosphor layer 102 is provided below the phosphor layer 101. Specifically, the phosphor layer 102 is provided between the phosphor layer 101 and the reflective layer 110. That is, the phosphor layer 101 is positioned on the incident side of the phosphor wheel 19a-1 to the excitation light from the laser diode light source 11 and is the uppermost layer forming the surface. In the modified example 1 of Embodiment 1, the phosphor layer 102 is in contact with the phosphor layer 101 and the reflective layer 110.

[0079] In the manufacture of the phosphor wheel 19a-1, the phosphor layer 102 and the phosphor layer 101 may be laminated in order on the reflective layer 110.

[0080] The following describes the behavior of light in multiple phosphor layers.

[0081] The excitation light from the laser diode light source 11 first enters the phosphor layer 101, which is stacked on top of the phosphor layer 102. The light from the laser diode light source 11 that enters the phosphor layer 101 is wavelength-converted and emitted from the phosphor layer 101 as yellow fluorescence, which is a mixture of green and red light. Due to complete diffusion, the wavelength-converted yellow (green and red) fluorescence is emitted both towards the substrate 100a and towards the phosphor layer 102.

[0082] The fluorescence emitted from the substrate 100a then enters the phosphor layer 102. Of the yellow first fluorescence incident on the phosphor layer 102, light in the wavelength range between green and red, for example, is wavelength-converted to second fluorescence in the phosphor layer 102. On the other hand, light in other wavelength ranges of the first fluorescence incident on the phosphor layer 102 passes directly through the phosphor layer 102, is reflected by the reflective layer 110, changes direction of propagation, passes through phosphor layers 102 and 101, and is emitted from phosphor layer 101.

[0083] The second fluorescence emitted from the phosphor layer 102 is emitted both towards the substrate 100a and the phosphor layer 101 due to complete diffusion. The second fluorescence emitted towards the phosphor layer 101 passes through the phosphor layer 101 and is emitted from the phosphor layer 101. The second fluorescence emitted towards the substrate 100a is reflected by the reflective layer 110, enters the phosphor layer 102 again, passes through phosphor layers 102 and 101, and is emitted from the phosphor layer 101. Note that the phosphor layer 101 is not easily excited by the second fluorescence, and is not excited by the second fluorescence.

[0084] Light that has been wavelength-converted by the phosphor layer 101 and emitted to the surface side is emitted from the phosphor layer 101. Light that has not been wavelength-converted by either the phosphor layer 101 or the phosphor layer 102 may be reflected by the reflective layer 1110, transmitted through the phosphor layers 102 and 101 and emitted from the phosphor layer 101, or it may be wavelength-converted when it is re-incident to the phosphor layer 101.

[0085] By placing the phosphor layer 101 on top of the phosphor layer 102, the excitation light from the laser diode light source 11 reaches the phosphor layer 101 first. Compared to the case where the phosphor layer 102 is placed on top of the phosphor layer 101, the excitation of the phosphor layer 102 by the excitation light from the laser diode light source 11 can be suppressed. As a result, more excitation light reaches the phosphor layer 101 and undergoes wavelength conversion there. Consequently, the wavelength conversion efficiency of the excitation light in the phosphor wheel 19a-1 is improved.

[0086] Furthermore, similar to the phosphor wheel 19a according to Embodiment 1, it is desirable that the thickness t2 of the phosphor layer 102 is thinner than the thickness t1 of the phosphor layer 101. This configuration makes it possible to suppress the temperature rise of the phosphor layer 102.

[0087] <Embodiment 2> Figure 6 is a schematic diagram showing an example of the configuration of the light source device 10b according to Embodiment 2.

[0088] The light source device 10b is configured to continuously emit blue, green, and red light. The light source device 10b is a light source device suitable for projection-type image display devices that use a three-panel liquid crystal panel, which will be described later.

[0089] The light source device 10b comprises an excitation light optical system, a fluorescence illumination system, a fluorescence separation illumination system, a blue light optical system, and an integrator illumination system.

[0090] The excitation light optical system of the light source device 10b is composed of a plurality of laser diode light sources 11, a plurality of collimator lenses 12 corresponding to each of the plurality of laser diode light sources 11, a convex lens 13, a diffuser plate 14, a concave lens 15, a λ / 2 phase difference plate 30, a separation dichroic mirror 25b, a dichroic mirror with polarization separation function 31, a convex lens 17, and a convex lens 18. λ represents the wavelength of light.

[0091] The fluorescent illumination system of the light source device 10b is composed of a phosphor wheel 19b, a convex lens 18, a convex lens 17, a dichroic mirror 31 with polarization separation function, and a separation dichroic mirror 25b.

[0092] The fluorescence separation illumination system of the light source device 10b is composed of a convex lens 18, a convex lens 17, a dichroic mirror 31 with polarization separation function, a separation dichroic mirror 25b, and a sensor 26.

[0093] The blue optical system of the light source device 10b is composed of a plurality of laser diode light sources 11, a plurality of collimator lenses 12 corresponding to each of the plurality of laser diode light sources 11, a convex lens 13, a diffuser plate 14, a concave lens 15, a λ / 2 phase difference plate 30, a separation dichroic mirror 25b, a dichroic mirror with polarization separation function 31, a λ / 4 phase difference plate 32, and a total reflection mirror 33.

[0094] The integrator illumination system of the light source device 10b is composed of a pair of fly-eye integrators 34 and a Polarization Beam Splitter (hereinafter referred to as "PBS") array 35.

[0095] The excitation light optical system of the light source device 10b differs from the excitation light optical system of the light source device 10a according to Embodiment 1 in the following respects. In the excitation light optical system of the light source device 10b, a λ / 2 phase difference plate 30 is provided between the concave lens 15 and the separating dichroic mirror 25b. In addition, in the excitation light optical system of the light source device 10b, the blue light emitted from the multiple laser diode light sources 11 is arranged so that the polarization directions are aligned. The dichroic mirror 31 with polarization separation function transmits P-polarized light and reflects S-polarized light from the blue wavelength range of light from the laser diode light sources 11, and transmits green and red light from the fluorescence from the phosphor wheel 19b, while reflecting the second fluorescence. In the description of Embodiment 2, parts that overlap with the description of Embodiment 1 may be omitted or simplified.

[0096] As described above, the light emitted from each of the multiple laser diode light sources 11, whose polarization directions are aligned, is made into parallel light by reducing the beam width through the collimator lens 12, convex lens 13, diffuser plate 14, and concave lens 15 corresponding to each light source, and then incident on the subsequent λ / 2 phase difference plate 30.

[0097] The λ / 2 phase difference plate 30 is held rotatably around the optical axis by a holding mechanism (not shown). The λ / 2 phase difference plate 30 also has the function of delaying the phase of the polarization vibration direction in the slow axis direction by λ / 2, corresponding to the wavelength of light from the laser diode light source 11, and can rotate the polarization direction of the light from the laser diode light source 11. By changing the rotation direction of the λ / 2 phase difference plate 30, the ratio of P-polarized light transmitted through the dichroic mirror 31 with polarization separation function to S-polarized light reflected can be changed, and ultimately it is possible to optimize the ratio of blue, green, and red light emitted from the light source device 10b.

[0098] Light from the laser diode light source 11, whose polarization direction is optimized by the λ / 2 phase difference plate 30, is incident on the separation dichroic mirror 25b. The separation dichroic mirror 25b has the characteristic of transmitting light in the blue wavelength range from the laser diode light source 11 and reflecting the second fluorescence from the fluorescence excited by the light from the laser diode light source 11 and wavelength converted in the phosphor wheel 19b. The light from the laser diode light source 11 that is incident on the separation dichroic mirror 25b passes through the separation dichroic mirror 25b as is and is incident on the dichroic mirror 31 with polarization separation function.

[0099] The dichroic mirror 31 with polarization separation function transmits P-polarized light from the blue wavelength range of the laser diode light source 11, reflects S-polarized light, transmits green and red light from the fluorescence excited by the light from the laser diode light source 11 and wavelength-converted in the phosphor wheel 19b, and reflects the second fluorescence. Of the light from the laser diode light source 11 incident on the dichroic mirror 31 with polarization separation function, S-polarized light is reflected and incident on the subsequent convex lens 17. The S-polarized light from the laser diode light source 11 incident on the convex lens 17 is focused onto the phosphor layer of the phosphor wheel 19b. The behavior of P-polarized light from the laser diode light source 11 incident on the dichroic mirror 31 with polarization separation function will be described later in the explanation of the blue optical system.

[0100] The phosphor wheel 19b of the light source device 10b in Embodiment 2 has the same configuration, function, and light behavior as the phosphor wheel 19a of the light source device 10a in Embodiment 1, so its description is omitted here. First fluorescence and second fluorescence are emitted from the phosphor wheel 19b.

[0101] The first and second fluorescence, emitted after wavelength conversion by the phosphor wheel 19b, pass through the convex lenses 18 and 17 to become parallel light, and are incident on a dichroic mirror 31 with polarization separation function, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0102] The fluorescence incident on the dichroic mirror 31 with polarization separation function, that is, the green light and red light of the first and second fluorescence, passes directly through the dichroic mirror 31 with polarization separation function and is incident on the integrator illumination system described later.

[0103] Furthermore, of the fluorescence incident on the dichroic mirror 31 with polarization separation function, the second fluorescence is reflected by the dichroic mirror 31 with polarization separation function, its direction of propagation is changed by 90 degrees, and it is incident on the separation dichroic mirror 25b.

[0104] In the fluorescence separation illumination system, the second fluorescence incident on the separation dichroic mirror 25b is reflected by the separation dichroic mirror 25b, changes its direction of travel by 90 degrees, and then incident on the sensor 26. The sensor 26 is provided with a circuit (not shown), which allows the sensor 26 to measure the light intensity of the second fluorescence.

[0105] The blue optical system of the light source device 10b, consisting of multiple laser diode light sources 11, multiple collimator lenses 12, a convex lens 13, a diffuser plate 14, a concave lens 15, a λ / 2 phase difference plate 30, a decoupling dichroic mirror 25b, and a dichroic mirror 31 with polarization separation function, is shared with the excitation light optical system.

[0106] This section describes the behavior of P-polarized light from the laser diode light source 11 that has passed through the dichroic mirror 31 with polarization separation function. The P-polarized light from the laser diode light source 11 that has passed through the dichroic mirror 31 with polarization separation function is incident on the subsequent λ / 4 phase difference plate 32.

[0107] The λ / 4 phase difference plate 32 has the function of delaying the phase of the polarization vibration direction in the slow phase axis direction by λ / 4, corresponding to the wavelength of light from the laser diode light source 11. The slow phase axis of the λ / 4 phase difference plate 32 is positioned rotated 45 degrees around the optical axis with respect to the vibration direction of P-polarized light from the laser diode light source 11 that has passed through the dichroic mirror 31 with polarization separation function. As a result, the P-polarized light from the laser diode light source 11 is changed to circularly polarized light.

[0108] The light, which has become circularly polarized after passing through the λ / 4 phase difference plate 32, is incident on the subsequent total internal reflection mirror 33, is reflected, changes direction by 180 degrees, and is then incident on the λ / 4 phase difference plate 32 again.

[0109] The circularly polarized light that is again incident on the λ / 4 phase difference plate 32 has its phase in the direction of polarization vibration delayed by λ / 4, which changes it from circularly polarized to S-polarized, and it is then incident on the dichroic mirror 31 with polarization separation function again.

[0110] S-polarized light incident on the dichroic mirror 31 with polarization separation function is reflected, changes its direction of propagation by 90 degrees, and then incident on the integrator illumination system described later.

[0111] Next, we will explain the behavior of the green and red light from the phosphor wheel 19b of the fluorescent lighting system and the blue light from the laser diode light source 11 of the blue optical system in the integrator lighting system of the light source device 10b after they are emitted from the dichroic mirror 31 with polarization separation function.

[0112] The green and red light from the phosphor wheel 19b of the fluorescent illumination system and the blue light from the laser diode light source 11 of the blue optical system are homogenized by a pair of fly-eye integrators 34, and the polarization direction of the light in all wavelength ranges is unified by the PBS array 35 before emission.

[0113] Thus, even with a light source device 10b that is configured to constantly emit blue, green, and red light, the configuration for separating the second fluorescence can be applied.

[0114] In the light source device 10b according to Embodiment 2, the excitation light from the laser diode light source 11 is wavelength-converted in the phosphor layer 101, and the first fluorescence is emitted from the phosphor layer 101. Then, the phosphor layer 102 is excited by light in a certain wavelength range of the first fluorescence, and this light is wavelength-converted to the second fluorescence. The second fluorescence emitted from the phosphor layer 102 is then guided to the sensor 26 by a dichroic mirror 31 with polarization separation function and a separation dichroic mirror 25b. The sensor 26 measures the amount of light from the second fluorescence. With the configuration of this embodiment, it is possible to detect the temperature rise of the phosphor wheel 19b earlier compared to the case where the phosphor layer 102 is not provided on the phosphor wheel 19b. As a result, the light source device 10b can perform processing to suppress the temperature rise of the phosphor wheel 19b. This suppresses the occurrence of efficiency reduction and reliability problems of the light source device 10b.

[0115] <Embodiment 3> Figure 7 is a schematic diagram showing an example of the configuration of the light source device 10c according to Embodiment 3.

[0116] The light source device 10c includes an optical system in which light emitted from the laser diode light source 11 loops, and is configured to emit light of different wavelengths such as blue, green, and red in a time series. The light source device 10c is a light source device suitable for projection-type image display devices that use a single-panel DMD, which will be described later.

[0117] The light source device 10c comprises an excitation light optical system, a blue loop optical system, a fluorescence illumination system, a fluorescence separation illumination system, and a time-series integrator illumination system.

[0118] The excitation light optical system of the light source device 10c consists of multiple laser diode light sources 11, multiple collimator lenses 12, a convex lens 13, a diffuser plate 14, a concave lens 15, a dichroic mirror 16c, a convex lens 17, and a convex lens 18.

[0119] The blue loop optical system of the light source device 10c consists of a phosphor wheel 19c, a convex lens 50, a convex lens 51, a total reflection mirror 52, a convex lens 53, a total reflection mirror 54, a convex lens 55, a total reflection mirror 56, a convex lens 57, a dichroic mirror 16c, a separated dichroic mirror 25c, and a convex lens 27.

[0120] The fluorescent illumination system of the light source device 10c consists of a convex lens 18, a convex lens 17, a dichroic mirror 16c, a separated dichroic mirror 25c, and a convex lens 27.

[0121] The fluorescent separation illumination system of the light source device 10c consists of a separation dichroic mirror 25c and a sensor 26.

[0122] The time-series integrator illumination system of the light source device 10c consists of a color wheel 40c and a rod integrator 28.

[0123] First, the excitation light optics of the light source device 10c will be described. The blue wavelength excitation light emitted from each of the multiple laser diode light sources 11 is collimated by multiple collimator lenses 12, each of which is provided in relation to each of the multiple laser diode light sources 11. The collimated blue light is incident on a subsequent convex lens 13, where its beam width is reduced, and then incident on a subsequent diffuser plate 14, where it is diffused, improving the uniformity of the light. The blue light that has been incident on the diffuser plate 14 and diffused is incident on a subsequent concave lens 15, where it is made into a parallel beam. The blue light made into a parallel beam by the concave lens 15 is incident on a dichroic mirror 16c, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0124] The dichroic mirror 16c reflects excitation light in the blue wavelength range from the laser diode light source 11, and transmits fluorescence emitted by the phosphor wheel 19c, described later, after wavelength conversion of the excitation light from the laser diode light source 11.

[0125] Light from the laser diode light source 11, incident on the dichroic mirror 16c, changes its direction of propagation by 90 degrees and is incident on the convex lens 17. The light from the laser diode light source 11, incident on the convex lens 17, is focused by the optical system of the convex lens 17 and the subsequent convex lens 18, and is concentrated on the phosphor layer on the phosphor wheel 19c.

[0126] Next, the phosphor wheel 19c according to Embodiment 3 will be described with reference to Figures 3, 8, and 9. Figure 8 is a front view showing an example of the configuration of the phosphor wheel 19c according to Embodiment 3. The cross-section AA of the phosphor wheel 19c is the same as the cross-sectional view shown in Figure 3, provided that the substrate 100a shown in Figure 3 is replaced with the substrate 100c.

[0127] The phosphor wheel 19c is composed of a substrate 100c to which the motor 120 is attached, a plurality of phosphor layers, a reflective layer 110, and an opening 130.

[0128] The reflective layer 110 is provided on one side of the substrate 100c in an annular shape at the same distance from the center of rotation of the substrate 100c. However, two openings 130 are provided in a part of the annulus. Therefore, more precisely, the reflective layer 110 is provided in a substantially fan shape that forms a part of the annulus.

[0129] On the reflective layer 110, phosphor layers are provided in divided regions. In the example shown in Figure 8, three types of phosphor layers 101, 102, and 103 are provided on the reflective layer 110. The multiple phosphor layers are arranged in a roughly fan-shaped form, similar to the reflective layer 110, forming part of a ring.

[0130] The substrate 100c may be made of a material such as aluminum, which has excellent heat dissipation properties. The substrate 100c is not limited to aluminum and may be made of other metals. Furthermore, the substrate 100c may be a transmissive substrate such as glass or sapphire, or a transmissive substrate such as glass or sapphire with a reflective region provided. In the case of a transmissive substrate 100, the substrate itself may be configured to transmit light without providing any openings.

[0131] The characteristics of the phosphor layer 101 and the phosphor layer 102 were described in the description of Embodiment 1, so they will not be described here.

[0132] The phosphor layer 103 will be described with reference to Figure 9. Figure 9 is a cross-sectional view showing the BB cross section of the phosphor wheel 19c according to Embodiment 3.

[0133] The phosphor layer 103 is a mixed layer in which a phosphor that emits green fluorescence, excited by blue light from the laser diode light source 11 and wavelength-converted, is filled into a heat-resistant resin such as silicone or silsesquioxane. Specific examples of phosphors include ruthenium (Lu) and aluminum (Al) composite oxide phosphors, LuAG, and Lu ３ AL ５ O １２ These are some examples. Hereinafter, the fluorescence emitted when the phosphor layer 103 wavelength-converts the excitation light from the laser diode light source 11 may be referred to as third fluorescence.

[0134] The phosphor layers 101, 102, and 103 may be composed of sintered phosphor particles forming a part of a ring shape, or they may be a combination of sintered particles and mixed layers.

[0135] In this explanation, a configuration in which a phosphor layer 102 is provided on top of a phosphor layer 101 is used as an example, but the explanation is not limited to this. For example, a phosphor layer that emits a second fluorescence, excited by light in the wavelength range between green and red, among the third fluorescence emitted from the phosphor layer 103, may be provided on top of the phosphor layer 103. Alternatively, phosphor layers capable of emitting a second fluorescence may be provided on both the phosphor layer 101 and the phosphor layer 103. Furthermore, the phosphor layer provided on top of the phosphor layer 103 may emit fluorescence in wavelength ranges different from those of the first, second, and third fluorescence.

[0136] Furthermore, as shown in Modification 1 of Embodiment 1, the phosphor layer 102 may be provided between the phosphor layer 101 and the reflective layer 110. Alternatively, the phosphor layer 102 may be a mixed layer in which the phosphor contained in the phosphor layer 101 and the phosphor contained in the phosphor layer 102 are mixed and filled into a heat-resistant resin such as silicone or silsesquioxane.

[0137] The fluorescence emitted after wavelength conversion in the phosphor layer 102 is not used as the light emitted by the light source device 10c. Since the temperature of the phosphor layer increases as the thickness of the phosphor layer increases, it is desirable that the thickness t2 of the phosphor layer 102 is thinner than the thickness t1 of the phosphor layer 101.

[0138] The reflective layer 110 is a mixed layer in which high-reflectivity particles are filled into a heat-resistant resin such as silicone or silsesquioxane. The particles filled into the reflective layer 110 are not limited to high-reflectivity particles; high-thermal-conductivity particles may also be included, and the reflective layer 110 may be a mixed layer that has improved thermal conductivity as well as reflectivity.

[0139] The multiple phosphor layers, reflective layer 110, and opening 130 are arranged to form a ring at the same distance (on the same radius) from the rotation center of the substrate 100c of the phosphor wheel 19c. Figure 8 shows an example in which the opening 130 and multiple phosphor layers are arranged in pairs, but the arrangement is not limited to this. Also, Figure 8 shows an example in which the angles between the paired openings 130 and phosphor layers are the same (for example, the angles between the opening 130 and the phosphor layer 103 are the same for both), but the angles may be different.

[0140] Light from the laser diode light source 11, guided by the excitation light optical system, is focused into an aperture 130 and a region of multiple phosphor layers formed on the same radius from the rotation center of the phosphor wheel 19c. Because the phosphor wheel 19c is rotating, the light guided to the phosphor wheel 19c is focused sequentially into the aperture 130 and the multiple phosphor layers. The behavior of light in the aperture 130 and the multiple phosphor layers will be described below.

[0141] First, the light from the laser diode light source 11, which is focused into the aperture 130, passes through the aperture 130 and is guided into the blue loop optical system. The behavior of light in the blue loop optical system will be described later.

[0142] The behavior of the light focused on the phosphor layer 102 was described in the description of Embodiment 1, so it will not be described here.

[0143] Referring to Figure 9, the behavior of light focused on the phosphor layer 103 will be explained. As shown in Figure 9, a reflective layer 110 is formed on the substrate 100c, and a phosphor layer 103 is formed on the reflective layer 110.

[0144] Light from the laser diode light source 11 first enters the phosphor layer 103 from the positive z-axis direction. The phosphor layer 103 is excited by the light from the laser diode light source 11, converts the excitation light to a different wavelength, and emits green fluorescence. Due to complete diffusion, the green fluorescence is emitted on both the substrate 100c side and the surface side (positive z-axis direction).

[0145] Light from the laser diode light source 11 that has not undergone wavelength conversion and fluorescence that has undergone wavelength conversion by the phosphor layer 103 and is emitted towards the substrate 100c are reflected by the reflective layer 110 formed between the substrate 100c and the phosphor layer 103, changing their direction of propagation and being emitted towards the phosphor layer 103 (positive z-axis direction).

[0146] Of the light from the laser diode light source 11 reflected by the reflective layer 110, some passes through the phosphor layer 103 without wavelength conversion, while the remainder is wavelength converted in the phosphor layer 103 and emitted from the phosphor layer 103 as green fluorescence. Due to complete diffusion, the green fluorescence is also emitted towards the reflective layer 110, but as described above, it is emitted again towards the phosphor layer 103. Fluorescence incident on the phosphor layer 103 passes through it and is emitted from the surface of the phosphor layer 103. The subsequent behavior of the third fluorescence emitted from the phosphor layer 103 will be described later, together with the second fluorescence emitted from the phosphor layer 102.

[0147] The structure and behavior of the phosphor layer 101 are the same as those of the phosphor layer 103, except that it wavelength-converts the light from the laser diode light source 11 into yellow fluorescence including green and red; therefore, a detailed explanation will be omitted.

[0148] Returning to Figure 7, we will explain the behavior of light in the blue loop optical system after it has passed through the aperture 130 of the phosphor wheel 19c.

[0149] The blue loop optical system consists of a relay optical system comprising two convex lenses (convex lens 50, convex lens 51) immediately behind the phosphor wheel 19c, three total reflection mirrors (total reflection mirror 52, total reflection mirror 54, total reflection mirror 56) and three convex lenses (convex lens 53, convex lens 55, convex lens 57), a dichroic mirror 16c shared with the excitation light optical system described above, a separate dichroic mirror 25c, and a convex lens 27.

[0150] Light from the laser diode light source 11 that has passed through the aperture 130 of the phosphor wheel 19c is made into parallel light by passing through two convex lenses (convex lens 50, convex lens 51) immediately after the phosphor wheel 19c. The parallelized light has its direction of propagation changed by a relay optical system consisting of three total reflection mirrors and three convex lenses, and is incident on the dichroic mirror 16c from a direction 180 degrees opposite to the direction in which the light from the laser diode light source 11 enters the excitation light optical system, that is, from the negative x-axis direction.

[0151] As described above, the dichroic mirror 16c has the characteristic of reflecting blue wavelength light from the laser diode light source 11 and transmitting fluorescence from the phosphor wheel 19c. Therefore, the light from the laser diode light source 11 that has passed through the opening 130 of the phosphor wheel 19c is reflected by the dichroic mirror 16c and changes its direction of travel toward the direction of the separated dichroic mirror 25c (positive z-axis direction).

[0152] The separated dichroic mirror 25c has the characteristic of reflecting the second fluorescence from the fluorescence emitted by the phosphor wheel 19c after wavelength conversion of the excitation light from the laser diode light source 11, while transmitting the other light. Specifically, the light other than the second fluorescence is the blue light from the laser diode light source 11, and the green and red light from the fluorescence emitted by the phosphor wheel 19c.

[0153] The light from the laser diode light source 11, after passing through the separated dichroic mirror 25c, passes through the subsequent convex lens 27 and is focused onto the color wheel 40c.

[0154] The behavior of light from the laser diode light source 11 after it is incident on the color wheel 40c will be described later in the explanation of the time-series integrator illumination system.

[0155] Next, the behavior of fluorescence emitted from the phosphor wheel 19c in a fluorescent lighting system will be explained with reference to Figure 7.

[0156] The fluorescent illumination system consists of two convex lenses (convex lens 18 and convex lens 17) directly in front of the phosphor wheel 19c, a dichroic mirror 16c, a decoupling dichroic mirror 25c, and a convex lens 27. The fluorescent illumination system shares the two convex lenses directly in front of the phosphor wheel 19c and the dichroic mirror 16c with the excitation light optical system, and the dichroic mirror 16c, decoupling dichroic mirror 25c, and convex lens 27 with the blue loop optical system.

[0157] From the phosphor layer 101 of the phosphor wheel 19c, yellow (green and red) fluorescence and light from the laser diode light source 11 that has not been wavelength-converted are emitted. From the phosphor layer 102 of the phosphor wheel 19c, yellow (green and red) fluorescence, secondary fluorescence, and light from the laser diode light source 11 that has not been wavelength-converted are emitted. From the phosphor layer 103 of the phosphor wheel 19c, green fluorescence and light from the laser diode light source 11 that has not been wavelength-converted are emitted. These lights are emitted from the phosphor wheel 19c in a time series. The light emitted from the phosphor wheel 19c is incident on two convex lenses (convex lens 18, convex lens 17) and is made into parallel light. The parallelized light is then incident on the dichroic mirror 16c.

[0158] The dichroic mirror 16c has the characteristic of reflecting blue wavelength light from the laser diode light source 11 and transmitting fluorescence emitted from the phosphor wheel 19c. Therefore, of the fluorescence emitted from the phosphor wheel 19c and the light from the laser diode light source 11 that has not undergone wavelength conversion, only the fluorescence passes through the dichroic mirror 16c and proceeds to the separation dichroic mirror 25c.

[0159] As described above, the separation dichroic mirror 25c has the property of reflecting the second fluorescence from the fluorescence emitted from the phosphor wheel 19c and transmitting the other light.

[0160] Therefore, of the fluorescence from the phosphor wheel 19c, the light other than the second fluorescence, specifically the green light and the red light, passes through the separating dichroic mirror 25c, then through the subsequent convex lens 27, and is focused onto the color wheel 40c.

[0161] The fluorescence behavior after incidence onto the color wheel 40c will be described later in the explanation of the time-series integrator illumination system.

[0162] The behavior of the second fluorescence, which is reflected and separated by the separation dichroic mirror 25c of the fluorescent illumination system, in the fluorescence separation illumination system will be described. The fluorescence separation illumination system consists of a separation dichroic mirror 25c and a sensor 26. The second fluorescence, which is reflected and separated by the separation dichroic mirror 25c, is incident on the subsequent sensor 26. The sensor 26 is provided with a circuit (not shown), which allows the sensor 26 to measure the light intensity of the second fluorescence.

[0163] Next, the behavior in the time-series integrator illumination system after light from the laser diode light source 11 from the blue loop optical system, i.e., blue light, and fluorescence from the fluorescence illumination system, i.e., green light and red light, are incident on the color wheel 40c will be described with reference to Figures 8 and 10. Figure 10 is a front view showing an example of the configuration of the color wheel 40c according to Embodiment 1.

[0164] The time-series integrator illumination system consists of a color wheel 40c and a rod integrator 28.

[0165] The color wheel 40c is constructed by attaching multiple regions having predetermined properties, for example, by applying a dielectric multilayer film to the surface of a transparent substrate, to a holding portion 200 provided on the motor 206. The transparent substrate may be made of, for example, a glass plate or a sapphire substrate.

[0166] Each region of the color wheel 40c is configured in a roughly fan-shaped form. Region 201 has the property of transmitting light in the blue, green, and red wavelength ranges. Region 202 has the property of reflecting light in the red wavelength range and transmitting light in wavelength ranges other than the red wavelength range. Region 203 has the property of transmitting light in the blue, green, and red wavelength ranges. Region 204 has the property of reflecting light in the green wavelength range and transmitting light in wavelength ranges other than the green wavelength range.

[0167] A synchronization circuit (not shown) synchronizes the rotational positions of the color wheel 40c and the phosphor wheel 19c. The phosphor wheel 19c shown in Figure 8 and the color wheel 40c shown in Figure 10 are shown in their synchronized positions. Hereafter, the phosphor wheel 19c shown in Figure 8 and the color wheel 40c shown in Figure 10 will be described assuming that they rotate clockwise.

[0168] In the color wheel 40c, region 201, a part of region 202, and a part of region 204 are located at the position corresponding to the opening 130 of the phosphor wheel 19c. As described above, regions 201, 202, and 204 of the color wheel 40c have the characteristic of transmitting light in the blue wavelength range. Therefore, the blue light from the laser diode light source 11 that has passed through the opening 130 of the phosphor wheel 19c passes through the color wheel 40c as is and is incident on the rod integrator 28.

[0169] In the color wheel 40c, region 202 is located at the position corresponding to the phosphor layer 103 of the phosphor wheel 19c. As described above, region 202 of the color wheel 40c has the characteristic of reflecting light in the red wavelength range and transmitting light in wavelength ranges other than the red wavelength range. Therefore, the green light excited and wavelength-converted in the phosphor layer 103 is transmitted through the color wheel 40c as is.

[0170] In the color wheel 40c, region 203 is located at the position corresponding to the phosphor layer 101 of the phosphor wheel 19c. As described above, region 203 of the color wheel 40c has the property of transmitting light in the respective wavelength ranges of blue, green, and red. Therefore, yellow light, which includes green and red, excited and wavelength-converted in the phosphor layer 101, passes through the color wheel 40c as is.

[0171] In the color wheel 40c, region 204 is located at the position corresponding to the phosphor layer 102 of the phosphor wheel 19c. As described above, region 204 of the color wheel 40c has the characteristic of reflecting light in the green wavelength range and transmitting light in wavelength ranges other than the green wavelength range. Here, since phosphor layer 101 is formed below phosphor layer 102, green light, red light, and secondary fluorescence are emitted from phosphor layer 102. Then, green light and red light, excluding the secondary fluorescence removed by the separation dichroic mirror 25c, reach the color wheel 40c. Therefore, in region 204, light in the green wavelength range is reflected and light in the red wavelength range is transmitted.

[0172] In this way, the light emitted from the color wheel 40c in a time series according to the positions of the phosphor wheel 19c and the color wheel 40c is incident on the rod integrator 28. The rod integrator 28 emits uniform light through multiple reflections within the rod integrator 28.

[0173] As described above, each region of the color wheel 40c passes through the optical path sequentially as the color wheel 40c rotates. Each region of the color wheel 40c transmits or reflects light of a specific wavelength range that is incident on it, specifically blue light, green light, or red light. In other words, the color wheel 40c is an example of a wavelength-selective element, particularly a time-division wavelength-selective element.

[0174] In the light source device 10c according to Embodiment 3, the excitation light from the laser diode light source 11 is wavelength-converted in the phosphor layer 101, and the first fluorescence is emitted from the phosphor layer 101. Then, the phosphor layer 102 is excited by light in a certain wavelength range of the first fluorescence, and this light is wavelength-converted to the second fluorescence. The second fluorescence emitted from the phosphor layer 102 is then guided to the sensor 26 by the separation dichroic mirror 25c. The sensor 26 measures the amount of light from the second fluorescence. With the configuration of this embodiment, it is possible to detect the temperature rise of the phosphor wheel 19c earlier compared to the case where the phosphor layer 102 is not provided on the phosphor wheel 19c. As a result, the light source device 10c can perform processing to suppress the temperature rise of the phosphor wheel 19c. This suppresses the occurrence of problems related to the efficiency reduction and reliability of the light source device 10c.

[0175] <Embodiment 4> Figure 11 is a schematic diagram showing an example of the configuration of the light source device 10d according to Embodiment 4.

[0176] The components in the configuration example shown in Figure 11 are the same as the components in the configuration example of the light source device 10c according to Embodiment 3 shown in Figure 7. However, in Embodiment 3, the separated dichroic mirror 25c and the sensor 26 were arranged between the dichroic mirror 16c and the convex lens 27 directly in front of the rod integrator 28. In contrast, in Embodiment 4, the separated dichroic mirror 25d and the sensor 26 are arranged between the concave lens 15 of the excitation light optical system and the dichroic mirror 16d. The light source device 10d includes an optical system in which light emitted from the laser diode light source 11 loops, and is configured to emit light of different wavelength ranges such as blue, green, and red in a time series. The light source device 10d is a light source device suitable for projection-type image display devices using a single-panel DMD, which will be described later.

[0177] Furthermore, the separated dichroic mirror 25d transmits light in the blue wavelength range, which is light from the laser diode light source 11. The separated dichroic mirror 25d also has the property of reflecting the second fluorescence emitted from the phosphor layer 102 of the phosphor wheel 19c. Moreover, the properties of the separated dichroic mirror 25d for light in wavelength ranges different from both the blue wavelength range and the second fluorescence wavelength range, specifically green wavelength light and red wavelength light, are not limited to transmission or reflection.

[0178] Furthermore, the dichroic mirror 16d has the characteristic of reflecting light in the blue wavelength range, which is light from the laser diode light source 11, and transmitting light in the green wavelength range and light in the red wavelength range of the fluorescence emitted from the phosphor wheel 19c. In addition, the dichroic mirror 16d has the characteristic of reflecting the second fluorescence of the fluorescence emitted from the phosphor wheel 19c.

[0179] In the following description of Embodiment 4, we will explain the differences from Embodiment 3, and may omit detailed explanations of overlapping parts.

[0180] The excitation light optical system of the light source device 10d consists of a plurality of laser diode light sources 11, a plurality of collimator lenses 12, a convex lens 13, a diffuser plate 14, a concave lens 15, a separating dichroic mirror 25d, a dichroic mirror 16d, a convex lens 17, and a convex lens 18.

[0181] The behavior of the blue wavelength light emitted from the laser diode light source 11 until it is emitted from the concave lens 15 is the same as in Embodiment 3, so a detailed explanation is omitted here.

[0182] The light, which has been parallelized by the concave lens 15, is incident on the separated dichroic mirror 25d, which is positioned at an angle of approximately 45 degrees with respect to the optical axis. The separated dichroic mirror 25d has the characteristic of transmitting light in the blue wavelength range, which is light from the laser diode light source 11. Therefore, the separated dichroic mirror 25d transmits the light from the laser diode light source 11 as is.

[0183] Light from the laser diode light source 11, having passed through the separated dichroic mirror 25d, is incident on a dichroic mirror 16d, which is positioned at an angle of approximately 45 degrees with respect to the optical axis. The dichroic mirror 16d has the characteristic of reflecting light in the blue wavelength range, which is light from the laser diode light source 11. Therefore, the light from the laser diode light source 11 changes its direction of travel by 90 degrees and is incident on the subsequent convex lens 17. The behavior of the light after it is incident on the convex lens 17 is the same as in Embodiment 3, so a detailed explanation is omitted here.

[0184] In the phosphor wheel 19c, similar to Embodiment 3, light in each wavelength range is emitted from the opening 130, the phosphor layer 101, the phosphor layer 103, and the layer in which the phosphor layer 101 and the phosphor layer 102 are stacked.

[0185] The blue loop optical system after light from the laser diode light source 11 has passed through the aperture 130 of the phosphor wheel 19c will now be described. The blue loop optical system of the light source device 10c included a separate dichroic mirror 25c. On the other hand, the blue loop optical system of the light source device 10d does not include a separate dichroic mirror 25d. Furthermore, the dichroic mirror 16d of the light source device 10d has the characteristic of reflecting blue wavelength light from the laser diode light source 11, transmitting green and red light from the fluorescence emitted from the phosphor wheel 19c, and reflecting the second fluorescence.

[0186] Light passing through the aperture 130 of the phosphor wheel 19c is parallelized by two convex lenses (convex lens 50, convex lens 51). The parallelized light then changes direction in a relay optical system consisting of three total reflection mirrors (total reflection mirror 52, total reflection mirror 54, total reflection mirror 56) and three convex lenses (convex lens 53, convex lens 55, convex lens 57), and is incident on the dichroic mirror 16d from a direction 180 degrees opposite to the direction in which light enters from the laser diode light source 11 in the excitation light optical system, that is, from the negative x-axis direction.

[0187] As described above, the dichroic mirror 16d has the characteristic of reflecting light in the blue wavelength range, which is light from the laser diode light source 11. Therefore, light incident on the dichroic mirror 16d is reflected, changes its direction of propagation by 90 degrees, passes through the convex lens 27, and is focused onto the color wheel 40c.

[0188] Next, the fluorescent illumination system of the light source device 10d will be described. The fluorescent illumination system of the light source device 10d differs from the fluorescent illumination system of the light source device 10c according to Embodiment 3 in the following two points. That is, the fluorescent illumination system of the light source device 10c includes a separated dichroic mirror 25c, but the fluorescent illumination system of the light source device 10d does not include a separated dichroic mirror 25d. Also, the characteristics of the dichroic mirror 16d differ from those of the dichroic mirror 16c.

[0189] The green fluorescence (third fluorescence) and the yellow fluorescence (first fluorescence) containing green and red, emitted after wavelength conversion in the respective regions of the phosphor layer 101 and phosphor layer 103, are parallelized by passing through the convex lenses 18 and 17 and incident on the dichroic mirror 16d. The dichroic mirror 16d has the characteristic of transmitting the first fluorescence and reflecting the second fluorescence among the fluorescence emitted from the phosphor wheel 19c. Therefore, the first fluorescence and the third fluorescence pass directly through the dichroic mirror 16d, incident on the subsequent convex lens 27, and are further focused on the subsequent color wheel 40c.

[0190] Since the phosphor layer 102 is laminated on top of the phosphor layer 101, it emits yellow (green and red) fluorescence (first fluorescence) and second fluorescence. These fluorescence emitted from the phosphor layer 102 are parallelized by passing through the convex lenses 18 and 17 and then incident on the dichroic mirror 16d. The dichroic mirror 16d has the property of transmitting the first fluorescence and reflecting the second fluorescence. Therefore, of the fluorescence emitted from the phosphor layer 102 and incident on the dichroic mirror 16d, the yellow fluorescence containing green and red light, i.e., the first fluorescence, passes through as is, but the second fluorescence is reflected, changing its direction of propagation by 90 degrees towards the laser diode light source 11 (positive x-axis direction). The yellow (green and red) fluorescence that has passed through the dichroic mirror 16d is incident on the subsequent convex lens 27 and then focused on the subsequent color wheel 40c. The behavior of the second fluorescence reflected by the dichroic mirror 16d will be described later in the following explanation of the fluorescence separation illumination system of the light source device 10d.

[0191] The fluorescent separation illumination system of the light source device 10d consists of a convex lens 18, a convex lens 17, a dichroic mirror 16d, a separation dichroic mirror 25d, and a sensor 26. In Embodiment 4, the arrangement of the separation dichroic mirror 25d and the sensor 26 differs from the arrangement of the separation dichroic mirror 25c and the sensor 26 in Embodiment 3. Also, in Embodiment 4, the characteristics of the dichroic mirror 16d and the separation dichroic mirror 25d differ from the characteristics of the dichroic mirror 16c and the separation dichroic mirror 25c in Embodiment 3.

[0192] As described in the explanation of the fluorescent illumination system of the light source device 10d, the second fluorescence emitted from the phosphor wheel 19c is reflected by the dichroic mirror 16d, changes direction of travel toward the separating dichroic mirror 25d, and enters the separating dichroic mirror 25d. The separating dichroic mirror 25d has the characteristic of transmitting light in the blue wavelength range, which is light from the laser diode light source 11, and reflecting the second fluorescence emitted from the phosphor layer 102 of the phosphor wheel 19c. Therefore, the second fluorescence that enters the separating dichroic mirror 25d is reflected, changes direction of travel by 90 degrees, and enters the sensor 26. The sensor 26 is provided with a circuit (not shown), which allows the sensor 26 to measure the amount of light of the second fluorescence.

[0193] A description of the time-series integrator illumination system of the light source device 10d will be omitted. This is because the behavior of the light beyond the color wheel 40c, which is guided to the color wheel 40c by the blue loop optical system and the fluorescent illumination system of the light source device 10d, is the same as in Embodiment 3.

[0194] In the light source device 10d according to Embodiment 4, the excitation light from the laser diode light source 11 is wavelength-converted in the phosphor layer 101, and the first fluorescence is emitted from the phosphor layer 101. Then, the phosphor layer 102 is excited by light in a certain wavelength range of the first fluorescence, and this light is wavelength-converted to the second fluorescence. The second fluorescence emitted from the phosphor layer 102 is then guided to the sensor 26 by the separation dichroic mirror 25d. The sensor 26 measures the amount of light from the second fluorescence. With the configuration of this embodiment, it is possible to detect the temperature rise of the phosphor wheel 19c earlier compared to the case where the phosphor layer 102 is not provided on the phosphor wheel 19c. As a result, the light source device 10d can perform processing to suppress the temperature rise of the phosphor wheel 19c. This suppresses the occurrence of efficiency reduction and reliability problems of the light source device 10d.

[0195] <Embodiment 5> Figure 12 is a schematic diagram showing an example of the configuration of the light source device 10e according to Embodiment 5.

[0196] The light source device 10e does not include an optical system that loops the light from the laser diode light source 11. The light source device 10e is configured to emit light of different wavelength ranges, such as blue, green, and red, in a time series. The light source device 10e is a light source device suitable for projection-type image display devices that use a single-panel DMD, which will be described later. The light source device 10e is composed of a plurality of laser diode light sources 11, collimator lenses 12 corresponding to each of the plurality of laser diode light sources 11, a composite mirror 60 with a blue light reflection region, a convex lens 13, a diffuser plate 14, a concave lens 15, a dichroic mirror 61 with a blue light reflection region, a convex lens 27, a color wheel 40e, a convex lens 17, a convex lens 18, a phosphor wheel 19e, a sensor 26, and a rod integrator 28.

[0197] First, the excitation light optical system of the light source device 10e will be described. The excitation light optical system of the light source device 10e is composed of a plurality of laser diode light sources 11, a collimator lens 12 corresponding to each of the plurality of laser diode light sources 11, a composite mirror 60 with a blue light reflection region, a convex lens 13, a diffuser plate 14, a concave lens 15, a dichroic mirror 61 with a blue light reflection region, a convex lens 27, a color wheel 40e, a convex lens 17, and a convex lens 18.

[0198] Light emitted from each of the multiple laser diode light sources 11 is collimated by a collimator lens 12 corresponding to each laser diode light source 11. The set of laser diode light source 11 and collimator lens 12 is positioned in locations corresponding to the reflection region and transmission region of the composite mirror 60 with a blue light reflection region. The transmission region of the composite mirror 60 with a blue light reflection region is located on the surface of the composite mirror 60 with a blue light reflection region to which light from the laser diode light source 11 from the positive x-axis direction is incident. The reflection region of the composite mirror 60 with a blue light reflection region is located on the surface of the composite mirror 60 with a blue light reflection region to which light from the laser diode light source 11 from the positive z-axis direction is incident.

[0199] Light from the laser diode light source 11 and collimator lens 12 corresponding to the reflection region of the composite mirror 60 with a blue light reflection region (i.e., the laser diode light source 11 and collimator lens 12 located in the positive z-axis direction relative to the composite mirror 60 with a blue light reflection region) is reflected by the composite mirror 60 with a blue light reflection region and travels with a 90-degree change in direction. Light from the laser diode light source 11 and collimator lens 12 corresponding to the transmission region of the composite mirror 60 with a blue light reflection region (i.e., the laser diode light source 11 and collimator lens 12 located in the positive x-axis direction relative to the composite mirror 60 with a blue light reflection region) is transmitted through the composite mirror 60 with a blue light reflection region as is. As a result, light from multiple laser diode light sources 11 is combined by the composite mirror 60 with a blue light reflection region and incident on the subsequent convex lens 13.

[0200] Light from the laser diode light source 11, incident on the convex lens 13, is focused, reducing the beam width, and then incident on the subsequent diffuser plate 14. The light diffused by the diffuser plate 14 is then incident on the subsequent concave lens 15, where it is made into a parallel beam. The light made into a parallel beam by the concave lens is then incident on a dichroic mirror 61 with a blue light reflecting region, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0201] The dichroic mirror 61 with a blue light reflective region transmits light from the laser diode light source 11. Furthermore, the dichroic mirror 61 with a blue light reflective region reflects the second fluorescence emitted from the phosphor wheel 19e after the light from the laser diode light source 11 has undergone wavelength conversion by the phosphor wheel 19e (described later), and transmits light in the green wavelength range and light in the red wavelength range. On the surface of the dichroic mirror 61 with a blue light reflective region, a blue light reflective region 62 is provided only in the region where the light from the laser diode light source 11 is incident immediately after passing through the concave lens 15. This region is made of a dielectric multilayer film that reflects blue light and transmits light in other wavelength ranges. The components of the light source device 10e are arranged and formed such that the blue light reflected by the color wheel 40e (described later) is incident on the region of the dichroic mirror 61 with a blue light reflective region where the blue light reflective region 62 is not provided.

[0202] Light in the blue wavelength range from the laser diode light source 11, which is parallelized by the concave lens 15 and incident on the blue light reflection region 62 of the dichroic mirror 61 with a blue light reflection region, is reflected, its direction of propagation is changed by 90 degrees, and it is incident on the subsequent convex lens 27, and then focused on the subsequent color wheel 40e.

[0203] Figure 13 is a front view showing an example of the configuration of the color wheel 40e according to Embodiment 5.

[0204] The color wheel 40e is constructed by attaching a holding part 300 provided on the motor 306 to a transparent substrate, where multiple regions having predetermined properties are formed by, for example, applying a dielectric multilayer film to the surface of the transparent substrate. The transparent substrate may be made of, for example, a glass plate or a sapphire substrate.

[0205] Each region of the color wheel 40e is configured in a roughly fan-shaped form. Region 301 has the property of passing through light in the blue, green, and red wavelength ranges. Region 302 has the property of reflecting light in the blue and red wavelength ranges and transmitting light in the green wavelength range. Region 303 has the property of reflecting light in the blue wavelength range and transmitting light in the green and red wavelength ranges. Region 304 has the property of reflecting light in the blue and green wavelength ranges and transmitting light in the red wavelength range.

[0206] The behavior of blue light from the laser diode light source 11 will be described below. The light from the laser diode light source 11 that enters region 301 of the color wheel 40e passes through the color wheel 40e and enters the subsequent rod integrator 28. The behavior of the light after it leaves the color wheel 40e will be described later in the explanation of the time-series integrator illumination system of the light source device 10e.

[0207] Light from the laser diode light source 11 that is incident on region 302, region 303, or region 304 of the color wheel 40e is reflected, changes direction by 180 degrees, and is incident on the convex lens 27 again.

[0208] The blue wavelength light from the laser diode light source 11, which is again incident on the convex lens 27, is made into parallel light and incident on the portion of the dichroic mirror 61 with a blue light reflection region other than the blue light reflection region 62.

[0209] The portion of the dichroic mirror 61 with a blue light reflective region other than the blue light reflective region 62 reflects the second fluorescence from the fluorescence emitted from the phosphor wheel 19e after the wavelength conversion of light from the laser diode light source 11 by the phosphor wheel 19e. Furthermore, the portion of the dichroic mirror 61 with a blue light reflective region other than the blue light reflective region 62 transmits the fluorescence other than the second fluorescence emitted from the phosphor wheel 19e and the blue wavelength light from the laser diode light source 11. Therefore, the blue wavelength light from the laser diode light source 11 that is incident on the portion of the dichroic mirror 61 with a blue light reflective region other than the blue light reflective region 62 passes directly through the dichroic mirror 61 with a blue light reflective region 61 and is incident on the convex lens 17.

[0210] Light in the blue wavelength range from the laser diode light source 11, which is incident on the convex lens 17, is focused by a combined optical system consisting of the convex lens 17 and the subsequent convex lens 18, and is concentrated onto the phosphor layer of the phosphor wheel 19e, which will be described later.

[0211] Referring to Figure 14, the phosphor wheel 19e according to Embodiment 5 will be described. Figure 14 is a front view showing an example of the configuration of the phosphor wheel 19e according to Embodiment 5. Note that the cross-section AA of the phosphor wheel 19e is the same as the cross-sectional view shown in Figure 3, provided that substrate 100a shown in Figure 3 is replaced with substrate 100e. Also, the cross-section BB of the phosphor wheel 19e is the same as the cross-sectional view shown in Figure 9, provided that substrate 100c shown in Figure 9 is replaced with substrate 100e.

[0212] Unlike the phosphor wheel 19c according to Embodiments 3 and 4 shown in Figure 8, the substrate 100e of the phosphor wheel 19e does not have an opening. On the substrate 100e, there is a substantially fan-shaped reflective layer 110, a phosphor layer 101, a phosphor layer 103, and a layer formed by stacking phosphor layer 101 and phosphor layer 102, which constitute a part of a ring at the same distance (on the same radius) from the rotation center of the substrate 100e. Each phosphor layer emits light in each wavelength range as fluorescence, as described in Embodiment 3. Here, the reflective layer 110 is shown as being formed as part of a ring, but it may be formed continuously to form a ring, and although an example is shown where there is a gap between phosphor layer 101 and phosphor layer 102 and phosphor layer 103 to form a substantially fan shape that is part of a ring, they may be connected to form a ring.

[0213] In Embodiments 3 and 4, the phosphor wheel 19c shown in Figure 8 and the color wheel 40c shown in Figure 10 were synchronized by a synchronization circuit (not shown). Similarly, in Embodiment 5, the phosphor wheel 19e shown in Figure 14 and the color wheel 40e shown in Figure 13 were synchronized by a synchronization circuit (not shown). The phosphor wheel 19e shown in Figure 14 and the color wheel 40e shown in Figure 13 are shown in the synchronized position.

[0214] Next, the fluorescent illumination system of the light source device 10e will be described. The fluorescent illumination system consists of a convex lens 18, a convex lens 17, a dichroic mirror 61 with a blue light reflection region, and a convex lens 27, and all components of the fluorescent illumination system are shared with the excitation light optical system.

[0215] The fluorescence emitted from each phosphor layer of the phosphor wheel 19e, specifically the first and second fluorescence, is incident on two convex lenses 18 and 17, where it is parallelized. The parallelized fluorescence is then incident on a dichroic mirror 61 with a blue light reflection region.

[0216] As described above, the dichroic mirror 61 with a blue light reflective region transmits light from the laser diode light source 11, reflects light in the wavelength range of the second fluorescence emitted from the phosphor wheel 19e, and transmits light in the wavelength range of the other fluorescence. The dichroic mirror 61 with a blue light reflective region is provided with a blue light reflective region 62 formed of a dielectric multilayer film that reflects only blue wavelength light from the laser diode light source 11 and transmits light in other wavelength ranges.

[0217] Of the fluorescence from the phosphor wheel 19e that is incident on the dichroic mirror 61 with a blue light reflective region, the second fluorescence is reflected, changes direction by 90 degrees, and enters the sensor 26. Of the fluorescence from the phosphor wheel 19e other than the second fluorescence that is incident on the dichroic mirror 61 with a blue light reflective region, that is, light in the green wavelength range and light in the red wavelength range pass through the dichroic mirror 61 with a blue light reflective region, enters the subsequent convex lens 27, and is further focused on the subsequent color wheel 40e.

[0218] The fluorescent separation illumination system of the light source device 10e consists of a dichroic mirror 61 with a blue light reflection area and a sensor 26.

[0219] As described above, the second fluorescence from the phosphor wheel 19e, which is incident on the dichroic mirror 61 with a blue light reflecting region, is reflected, changes direction of travel by 90 degrees, and is incident on the sensor 26. The sensor 26 is provided with a circuit (not shown), which allows the sensor 26 to measure the amount of light from the second fluorescence.

[0220] Next, we will describe the behavior of light in the time-series integrator illumination system of the light source device 10e. More specifically, we will describe the behavior of light with different wavelengths over time that is guided to the color wheel 40e by the excitation light optical system and the fluorescence illumination system of the light source device 10e. The characteristics of each region of the color wheel 40e have been explained with reference to Figure 13, so we will omit the explanation here.

[0221] As described in the explanation of the behavior of light in the excitation light optical system of the light source device 10e, the light from the laser diode light source 11 incident on region 301 of the color wheel 40e passes straight through the color wheel 40e.

[0222] The phosphor layer 103 of the phosphor wheel 19e corresponds to the region 302 of the color wheel 40e. Green fluorescence is emitted from the phosphor layer 103 of the phosphor wheel 19e, which is excited and wavelength-converted by blue wavelength light from the laser diode light source 11. The green fluorescence is focused onto the color wheel 40e by the fluorescence illumination system. The green fluorescence from the phosphor wheel 19e that enters region 302 of the color wheel passes through the color wheel 40e and enters the subsequent rod integrator 28.

[0223] The phosphor layer 101 of the phosphor wheel 19e corresponds to the region 303 of the color wheel 40e. From the phosphor layer 101 of the phosphor wheel 19e, yellow (green and red) fluorescence is emitted, which is excited and wavelength-converted by blue wavelength light from the laser diode light source 11. The yellow (green and red) fluorescence is focused onto the color wheel 40e by the fluorescence illumination system. The yellow (green and red) fluorescence from the phosphor wheel 19e that enters region 303 of the color wheel passes through the color wheel 40e and enters the subsequent rod integrator 28.

[0224] The phosphor layer 102 of the phosphor wheel 19e corresponds to the region 304 of the color wheel 40e. From the phosphor layer 102 of the phosphor wheel 19e, yellow (green and red) fluorescence, which is excited and wavelength-converted by blue wavelength light from the laser diode light source 11, and secondary fluorescence are emitted. The fluorescence separation illumination system and the fluorescence illumination system focus the yellow (green and red) fluorescence of the yellow (green and red) fluorescence and secondary fluorescence onto the color wheel 40e. Of the yellow (green and red) fluorescence from the phosphor wheel 19e that is incident on region 304 of the color wheel, the light in the green wavelength range is reflected and travels in the direction of the convex lens 27 (negative z-axis direction), and the light in the red wavelength range is incident on the subsequent rod integrator 28.

[0225] In this way, the light emitted from the color wheel 40e in a time series according to the positions of the phosphor wheel 19e and the color wheel 40e is incident on the rod integrator 28. The rod integrator 28 emits uniform light through multiple reflections within the rod integrator 28.

[0226] In the light source device 10e according to Embodiment 5, the excitation light from the laser diode light source 11 is wavelength-converted in the phosphor layer 101, and the first fluorescence is emitted from the phosphor layer 101. Then, the phosphor layer 102 is excited by light in a certain wavelength range of the first fluorescence, and this light is wavelength-converted to the second fluorescence. The second fluorescence emitted from the phosphor layer 102 is then guided to the sensor 26 by the dichroic mirror 61 with a blue light reflecting region. The sensor 26 measures the amount of light from the second fluorescence. With the configuration of this embodiment, it is possible to detect the temperature rise of the phosphor wheel 19e earlier compared to the case where the phosphor layer 102 is not provided on the phosphor wheel 19e. As a result, the light source device 10e can perform processing to suppress the temperature rise of the phosphor wheel 19e. This suppresses the occurrence of problems related to the efficiency reduction and reliability of the light source device 10e.

[0227] [Projection-type Image Display Device] Next, a projection-type image display device 400a having a light source device 10a according to Embodiment 1 will be described with reference to Figure 15. Figure 15 is a schematic diagram showing an example configuration of a projection-type image display device 400a including a light source device 10a according to Embodiment 1. The projection-type image display device 400a uses a three-panel DMD (DMD509, DMD510, and DMD511).

[0228] The projection-type image display device 400a comprises a light source device 10a, a convex lens 501, a convex lens 502, a convex lens 503, a total internal reflection prism 507, a dichroic prism (described later), three DMDs (DMD 509, DMD 510, and DMD 511), and a projection lens 508.

[0229] The configuration and behavior of the light source device 10a will be omitted, and the behavior of the blue light, green light, and red light emitted from the rod integrator 28 will be described.

[0230] The optical system consisting of convex lens 501, convex lens 502, convex lens 503, total internal reflection prism 507, dichroic prism (described later), and three DMDs (DMD 509, DMD 510, and DMD 511) is sometimes referred to as the relay lens optical system of the projection-type image display device 400a. The three convex lenses 501, 502, and 503 are sometimes collectively referred to as the relay lens. The relay lens may be designed so that light of different wavelengths, i.e., blue light, green light, and red light, emitted from the aperture of the rod integrator 28 of the light source device 10a, is guided to each of the three DMDs described later.

[0231] The total internal reflection prism 507 is composed of two prisms with a small gap 512 in between. Light emitted from the relay lens and incident on the total internal reflection prism 507 is reflected by the small gap 512 at an angle greater than the total internal reflection angle, changing the direction of light propagation and guiding it to the dichroic prism.

[0232] The dichroic prism is composed of three glass blocks 504, 505, and 506. A small gap 514 is provided between the first glass block 504 and the second glass block 506 from the light incident side. Furthermore, the total internal reflection prism 507 and the dichroic prism are arranged so that a small gap 513 is provided between them.

[0233] The behavior of blue, red, and green light emitted from the total internal reflection prism 507 will be explained in order.

[0234] Blue light emitted from the total internal reflection prism 507 and incident on the first glass block 504 of the dichroic prism is reflected by a dichroic reflective layer (not shown) formed between the glass block 504 and the second glass block 506 of the dichroic prism, which has the property of reflecting blue light. The reflected blue light is then incident on a minute gap 513 provided between the first glass block 504 of the dichroic prism and the total internal reflection prism 507 at an angle greater than the total internal reflection angle, reflected, changes direction of propagation, and is guided to the blue light DMD 509 positioned on the surface of the glass block 504. The dichroic reflective layer may be made of, for example, a dielectric multilayer film.

[0235] Red light emitted from the total internal reflection prism 507 and incident on the first glass block 504 of the dichroic prism passes through the dichroic reflective layer that reflects blue light between the glass block 504 and the second glass block 506 of the dichroic prism, and is incident on the second glass block 506. The red light incident on the second glass block 506 is reflected by a dichroic reflective layer (not shown) that has the property of reflecting red light and is provided between the glass block 506 and the third glass block 505 of the dichroic prism. The reflected red light is incident on the minute gap 514 between the glass block 504 and the glass block 506 at an angle greater than the total internal reflection angle, is reflected again, changes direction of propagation, and is guided to the red DMD 511 positioned on the surface of the glass block 506.

[0236] Green light emitted from the total internal reflection prism 507 and incident on the first glass block 504 of the dichroic prism passes through the dichroic reflective layer that reflects blue light between glass block 504 and the second glass block 506 of the dichroic prism, and incident on the second glass block 506. The green light incident on the second glass block 506 passes through the dichroic reflective layer that reflects red light, which is provided between glass block 506 and the third glass block 505 of the dichroic prism, and incident on the third glass block 505. The green light incident on glass block 505 is guided to the green DMD 510 positioned on the surface of glass block 505.

[0237] Each DMD (DMD509, DMD510, and DMD511) for blue, green, and red light is composed of multiple micro-mirrors corresponding to pixels. An image circuit (not shown) changes the tilt direction of each of the micro-mirrors in each DMD in response to the image signal, thereby changing the direction of light propagation. The red, blue, and green light, whose direction of propagation has been changed by each DMD, is then incident on a dichroic prism.

[0238] The projection optical system of the projection-type image display device 400a consists of three DMDs (DMD 509, DMD 510, and DMD 511), a dichroic prism composed of glass blocks 504, 505, and 506, a total internal reflection prism 507, and a projection lens 508. The behavior of green light, red light, and blue light, whose direction of propagation is changed according to the video signal by each DMD for green, red, and blue light, will be described in order below.

[0239] The green light emitted from the green DMD 510 and incident on the glass block 505 passes through the dichroic reflective layer that reflects red light, which is provided between the glass block 505 and the glass block 506. The green light then passes through the minute gap 514 provided between the glass block 504 and the glass block 506 by being incident at an angle less than or equal to the angle of total internal reflection. The green light then passes through the dichroic reflective layer that reflects blue light, which is provided between the glass block 504 and the glass block 506, and is incident on the glass block 504. The green light incident on the glass block 504 passes through the minute gap 513 between the glass block 504 and the total internal reflection prism 507 by being incident at an angle less than or equal to the angle of total internal reflection, and is incident on the total internal reflection prism 507.

[0240] Red light emitted from the red DMD 511 and incident on the glass block 506 is reflected when it is incident on the minute gap 514 provided between glass block 504 and glass block 506 at an angle greater than or equal to the total internal reflection angle. The reflected red light changes direction of travel towards the dichroic reflective layer that reflects red light, provided between glass block 505 and glass block 506. Red light incident on the dichroic reflective layer that reflects red light is reflected and changes direction of travel towards the minute gap 514 provided between glass block 504 and glass block 506. Then, the red light passes through the minute gap 514 provided between glass block 504 and glass block 506 by being incident on at an angle less than or equal to the total internal reflection angle. The red light further passes through the dichroic reflective layer that reflects blue light, provided between glass block 504 and glass block 506, and is incident on glass block 504. The red light incident on the glass block 504 passes through the minute gap 513 between the glass block 504 and the total internal reflection prism 507 at an angle less than or equal to the total internal reflection angle, and then enters the total internal reflection prism 507.

[0241] The blue light emitted from the blue-emitting DMD 509 and incident on the glass block 504 is reflected when it is incident on the minute gap 513 between the glass block 504 and the total internal reflection prism 507 at an angle greater than or equal to the total internal reflection angle. The reflected blue light changes its direction of travel towards the dichroic reflective layer that reflects blue light, which is provided between the glass block 504 and the glass block 506, and continues to travel. The blue light then incident on the dichroic reflective layer that reflects blue light, which is provided between the glass block 504 and the glass block 506, is reflected, and is transmitted through the minute gap 513 between the glass block 504 and the total internal reflection prism 507 at an angle less than or equal to the total internal reflection angle, and then incident on the total internal reflection prism 507.

[0242] Blue, red, and green light incident on the total internal reflection prism 507 pass straight through the prism 507 by entering the minute gap 512 of the prism 507 at an angle less than or equal to the total internal reflection angle. The light of each color emitted from the total internal reflection prism 507 enters the projection lens 508 and is then projected onto a screen (not shown).

[0243] Thus, the projection-type image display device 400a may be configured to include a light source device (light source device 10a in the example of Figure 15) that has the effect of suppressing the temperature rise of the phosphor wheel (phosphor wheel 19a in the example of Figure 15) by detecting the temperature rise of the phosphor wheel at an early stage. This makes it possible to suppress the occurrence of efficiency degradation and reliability problems in the projection-type image display device 400a as well.

[0244] Next, a projection-type image display device 400b having a light source device 10b according to Embodiment 2 will be described with reference to Figure 16. Figure 16 is a schematic diagram showing an example configuration of a projection-type image display device 400b including a light source device 10b according to Embodiment 2. The projection-type image display device 400b uses a three-panel liquid crystal panel (liquid crystal panel 605, liquid crystal panel 610, and liquid crystal panel 618).

[0245] The projection-type image display device 400b consists of a light source device 10b, a red illumination system, a green illumination system, a blue illumination system, three sets of liquid crystal panels equipped with polarizing plates, and a projection optical system.

[0246] The configuration and behavior of the light source device 10b will be omitted, and the behavior of the blue light, green light, and red light emitted from the PBS array 35 will be described.

[0247] The red illumination system of the projection-type image display device 400b comprises a convex lens 601, a dichroic mirror 602, a total reflection mirror 603, and a convex lens 604. The red illumination system is designed so that the red light emitted from the PBS array 35 of the light source device 10b is superimposed onto the red liquid crystal panel 605, which will be described later, by the two convex lenses.

[0248] Red light emitted from the light source device 10b and passing through the convex lens 601 is incident on a dichroic mirror 602, which is positioned at an angle of approximately 45 degrees to the optical axis. The dichroic mirror 602 has the characteristic of reflecting light in the red wavelength range and transmitting light in the green wavelength range and blue wavelength range. The red light incident on the dichroic mirror 602 is reflected by the dichroic mirror 602, changes its direction of travel by 90 degrees, and is incident on the subsequent total reflection mirror 603. The red light is reflected by the total reflection mirror 603, changes its direction of travel by 90 degrees, and is incident on the convex lens 604. The red light then passes through the polarizing plate 606, which will be described later, and is superimposed onto the red liquid crystal panel 605.

[0249] The green illumination system of the projection-type image display device 400b comprises a convex lens 601, a dichroic mirror 602, a dichroic mirror 608, and a convex lens 609. The green illumination system is designed so that the green light emitted from the PBS array 35 of the light source device 10b is superimposed onto the green liquid crystal panel 610, which will be described later, by the two convex lenses. The convex lens 601 and the dichroic mirror 602 of the green illumination system are also shared with the red illumination system.

[0250] Green light emitted from the light source device 10b and passing through the convex lens 601 is incident on a dichroic mirror 602, which is positioned at an angle of approximately 45 degrees with respect to the optical axis. The dichroic mirror 602 has the characteristic of reflecting light in the red wavelength range and transmitting light in the green wavelength range and light in the blue wavelength range. The green light incident on the dichroic mirror 602 passes straight through the dichroic mirror 602 and is incident on a subsequent dichroic mirror 608, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0251] The dichroic mirror 608 has the property of reflecting light in the green wavelength range and transmitting light in the blue wavelength range. Green light incident on the dichroic mirror 608 is reflected, changes its direction of propagation by 90 degrees, and then incident on the convex lens 609. The green light then passes through the polarizing plate 611, which will be described later, and is superimposed onto the green liquid crystal panel 610.

[0252] The blue illumination system of the projection-type image display device 400b comprises a convex lens 601, a dichroic mirror 602, a dichroic mirror 608, a convex lens 613, a total reflection mirror 614, a convex lens 615, a total reflection mirror 616, and a convex lens 617. The blue illumination system is designed so that the blue light emitted from the PBS array 35 of the light source device 10b is superimposed onto the blue liquid crystal panel 618, which will be described later, by the convex lens 601 and a relay system composed of three convex lenses. In addition, the convex lens 601, dichroic mirror 602, and dichroic mirror 608 of the blue illumination system are shared with the green illumination system.

[0253] The blue light emitted from the light source device 10b and passing through the convex lens 601 is incident on a dichroic mirror 602, which is positioned at an angle of approximately 45 degrees with respect to the optical axis. The dichroic mirror 602 has the characteristic of reflecting light in the red wavelength range and transmitting light in the green wavelength range and blue wavelength range. The blue light incident on the dichroic mirror 602 passes straight through the dichroic mirror 602 and is incident on a subsequent dichroic mirror 608, which is positioned at an angle of approximately 45 degrees with respect to the optical axis.

[0254] The dichroic mirror 608 has the property of reflecting light in the green wavelength range and transmitting light in the blue wavelength range. Blue light incident on the dichroic mirror 608 passes straight through the dichroic mirror 608 and is incident on the subsequent convex lens 613.

[0255] The blue light is relayed and its direction of travel is changed by three convex lenses (convex lens 613, convex lens 615, and convex lens 617) and two total reflection mirrors (total reflection mirror 614 and total reflection mirror 616). The blue light then passes through a polarizing plate 619, which will be described later, and is superimposed onto the blue liquid crystal panel 618.

[0256] Each of the red liquid crystal panel 605, green liquid crystal panel 610, and blue liquid crystal panel 618 is provided with polarizing plates on both the light-incident and light-emitting sides. The red liquid crystal panel 605 has a polarizing plate 606 on the light-incident side and a polarizing plate 607 on the light-emitting side. The green liquid crystal panel 610 has a polarizing plate 611 on the light-incident side and a polarizing plate 612 on the light-emitting side. The blue liquid crystal panel 618 has a polarizing plate 619 on the light-incident side and a polarizing plate 620 on the light-emitting side. Since the behavior of each color liquid crystal panel is similar, the following explanation will describe the light incident on the liquid crystal panel without limiting it to a specific color.

[0257] The red, green, and blue light, whose polarization directions are unified by the PBS array 35 of the light source device 10b, are incident on the polarizing plates positioned on the incident side of each liquid crystal panel without changing the polarization direction in each of the red, green, and blue illumination systems. Since the polarization direction of the light emitted from the PBS array 35 matches the polarization direction transmitted through the polarizing plates, the light from the light source device 10b emitted from the PBS array 35 passes through the polarizing plates.

[0258] The liquid crystal panel, using an image circuit (not shown), changes the polarization direction of a minute area corresponding to a pixel in response to the image signal, and emits light incident on the liquid crystal panel. The light emitted from the liquid crystal panel passes through a polarizing plate located on the output side of the liquid crystal panel, and is emitted as image light of each pixel with different intensities corresponding to the image signal.

[0259] The projection optical system of the projection-type image display device 400b comprises three sets of liquid crystal panels, each equipped with a polarizing plate on the light incident side and the light exit side, a cross-cube prism 621, and a projection lens 622.

[0260] As shown in Figure 16, the four faces of the cross-cube prism 621 are each facing a red liquid crystal panel 605 equipped with a polarizer, a green liquid crystal panel 610 equipped with a polarizer, a blue liquid crystal panel 618 equipped with a polarizer, and a projection lens 622, respectively. In the example in Figure 16, the green liquid crystal panel 610 is positioned directly facing the projection lens 622. The cross-cube prism 621 also has a dichroic mirror reflective layer that reflects red light and transmits green and blue light, and a dichroic mirror reflective layer that reflects blue light and transmits green and red light.

[0261] The red light emitted from the red liquid crystal panel 605 enters a dichroic mirror reflective layer located inside the cross-cube prism 621, which reflects red light and transmits green and blue light, and is reflected. The reflected red light changes direction by 90 degrees and is emitted from the cross-cube prism 621, entering the projection lens 622.

[0262] The blue light emitted from the blue liquid crystal panel 618 enters a dichroic mirror reflective layer located inside the cross-cube prism 621, which reflects blue light and transmits green and red light, and is reflected. The reflected blue light changes direction by 90 degrees and is emitted from the cross-cube prism 621, entering the projection lens 622.

[0263] The green light emitted from the green liquid crystal panel 610 passes through a dichroic mirror reflective layer inside the cross cube prism 621 that reflects red light and transmits green and blue light, and another dichroic mirror reflective layer that reflects blue light and transmits green and red light. The green light is then emitted from the cross cube prism 621 and incident on the projection lens 622.

[0264] The red, green, and blue light combined by the cross-cube prism 621 are then incident on the projection lens 622 and projected onto a screen (not shown).

[0265] In the example shown in Figure 16, a relay system is used in a blue lighting system; however, a configuration in which a relay system is used in a green lighting system or a red lighting system is also acceptable.

[0266] Thus, the projection-type image display device 400b may be configured to include a light source device (light source device 10b in the example of Figure 16) that has the effect of suppressing the temperature rise of the phosphor wheel (phosphor wheel 19b in the example of Figure 16) by detecting the temperature rise of the phosphor wheel at an early stage. This makes it possible to suppress the occurrence of efficiency degradation and reliability problems in the projection-type image display device 400b as well.

[0267] Next, a projection-type image display device 400c having a light source device 10c according to Embodiment 3 will be described with reference to Figure 17. Figure 17 is a schematic diagram showing an example configuration of a projection-type image display device 400c including a light source device 10c according to Embodiment 3. The projection-type image display device 400c uses a single-board DMD (DMD704). Note that the projection-type image display device 400c may also have a light source device 10d according to Embodiment 4 or a light source device 10e according to Embodiment 5 instead of the light source device 10c according to Embodiment 3. Here, an example in which the projection-type image display device 400c has a light source device 10c will be described.

[0268] The projection-type image display device 400c comprises a light source device 10c, a convex lens 701, a convex lens 702, a convex lens 703, a DMD 704, a total internal reflection prism 706, and a projection lens 707.

[0269] The configuration and behavior of the light source device 10c will be omitted, and the behavior of the light emitted from the rod integrator 28, whose wavelength changes over time, will be described.

[0270] The optical system consisting of convex lenses 701, 702, 703, DMD 704, and total internal reflection prism 706 is sometimes referred to as the relay lens optical system of the projection-type image display device 400c. Furthermore, the three convex lenses 701, 702, and 703 are sometimes collectively referred to as the relay lens. The relay lens may be designed so that light with different wavelengths over time, emitted from the aperture of the rod integrator 28 of the light source device 10c, is guided to the DMD 704, which will be described later.

[0271] The total internal reflection prism 706 is composed of two prisms with a small gap 705 in between. Light emitted from the relay lens and incident on the total internal reflection prism 706 is reflected by the small gap 705 at an angle greater than the total internal reflection angle, changing the direction of light propagation and guiding it to the DMD 704.

[0272] The DMD 704 is composed of multiple minute mirrors corresponding to pixels, and a video circuit (not shown) changes the tilt direction of each of the multiple minute mirrors in accordance with the video signal, thereby changing the direction of light propagation. The light from the light source device 10c, whose wavelength range changes over time and whose direction of propagation has been changed by the DMD 704, is incident on the total internal reflection prism 706 as video light.

[0273] The projection optical system of the projection-type image display device 400c consists of a DMD 704, a total internal reflection prism 706, and a projection lens 707. Image light, whose wavelength range changes over time, is emitted from the DMD 704 and enters the total internal reflection prism 706. Here, the image light enters the minute gap 705 at an angle less than or equal to the total internal reflection angle, thereby passing through the total internal reflection prism 706 without changing the direction of light propagation. The image light then exits the total internal reflection prism 706, enters the projection lens 707, and is subsequently projected onto a screen (not shown).

[0274] Thus, the projection-type image display device 400c may be configured to include a light source device (light source device 10c in the example of Figure 17) that has the effect of suppressing the temperature rise of the phosphor wheel (phosphor wheel 19c in the example of Figure 17) by detecting the temperature rise of the phosphor wheel at an early stage. This makes it possible to suppress the occurrence of efficiency degradation and reliability problems in the projection-type image display device 400c as well.

[0275] (Summary of Embodiments) The following technologies are disclosed based on the descriptions of the various embodiments above. The components etc. in the above embodiments are examples, but are not limited to these.

[0276] (Technical 1) A light source device (for example, a light source device 10a) comprises a light source (for example, a laser diode light source 11), a wavelength conversion element (for example, a phosphor wheel 19a) having a first phosphor layer (for example, a phosphor layer 101) comprising a first phosphor that wavelength-converts excitation light from the light source to a first fluorescence, and a second phosphor layer (for example, a phosphor layer 102) comprising a second phosphor that wavelength-converts excitation light or a part of the first fluorescence to a second fluorescence, wherein the ratio of the amount of light of the first fluorescence at a second temperature higher than the first temperature to the amount of light of the first fluorescence at a first temperature of the first phosphor contained in the first phosphor layer is greater than the ratio of the amount of light of the second fluorescence at a second temperature to the amount of light of the second fluorescence at a first temperature of the second phosphor contained in the second phosphor layer.

[0277] As a result, the first phosphor layer can wavelength-convert excitation light into first fluorescence. The second phosphor layer can wavelength-convert excitation light or a portion of the first fluorescence into second fluorescence. The wavelength conversion element can emit light containing both the first and second fluorescence. Here, the ratio of the amount of light emitted by the first phosphor in the first phosphor layer at a second temperature (higher than the first temperature) to the amount of light emitted by the first fluorescence at a first temperature is greater than the ratio of the amount of light emitted by the second phosphor in the second phosphor layer at a second temperature to the amount of light emitted by the second fluorescence at a first temperature. In other words, the temperature at which the wavelength conversion efficiency of the second phosphor layer begins to decrease is lower than the temperature at which the wavelength conversion efficiency of the first phosphor layer begins to decrease. Therefore, the light source device can, for example, quickly detect a decrease in the conversion efficiency of the second phosphor layer before the conversion efficiency of the first phosphor layer decreases significantly, and can further perform processing to suppress the temperature rise of the first phosphor layer.

[0278] (Technology 2) The light source device described in Technology 1 comprises: an optical separation means arranged on the optical path of light from a wavelength conversion element for separating a second fluorescence from light from a wavelength conversion element; an optical intensity measuring means for measuring the amount of light of the second fluorescence separated by the optical separation means; and a determination means for determining whether the amount of light of the second fluorescence measured by the optical intensity measuring means is less than a certain value.

[0279] As a result, the light separation means of the light source device can separate the second fluorescence from the light emitted by the wavelength conversion element. The light intensity measuring means of the light source device can measure the light intensity of the separated second fluorescence. The determination means of the light source device can determine whether the light intensity of the second fluorescence measured by the light intensity measuring means is less than a certain value. As a result, the light source device can detect if a decrease in the efficiency of wavelength conversion of the second phosphor layer occurs.

[0280] (Technology 3) The light source device described in Technology 2 includes a control unit that performs temperature suppression control to suppress the temperature rise of the wavelength conversion element when the determination means determines that the amount of second fluorescence light measured by the light intensity measuring means is less than a certain value.

[0281] As a result, when the control unit of the light source device determines that the amount of light from the second fluorescence measured by the light intensity measuring means is less than a certain value, that is, when the determination means detects a decrease in the conversion efficiency of the second phosphor layer, it can suppress the temperature rise of the first phosphor layer and the wavelength conversion element by performing temperature suppression control, such as controlling the irradiation intensity of the excitation light.

[0282] (Technology 4) In the light source device described in any one of Techniques 1 to 3, the second phosphor layer is provided on the first phosphor layer and is positioned on the side of the wavelength conversion element where the excitation light from the light source is incident.

[0283] This allows, for example, the second phosphor layer to pass the excitation light directly without wavelength conversion. In this case, for example, the excitation light is wavelength-converted to the first fluorescence in the first phosphor layer. Then, the second phosphor layer wavelength-converts the excitation light or a portion of the first fluorescence to the second fluorescence, and the second fluorescence can be emitted from the wavelength conversion element.

[0284] (Technology 5) In the light source device described in any one of Techniques 1 to 4, the thickness of the second phosphor layer (e.g., thickness t2) is thinner than the thickness of the first phosphor layer (e.g., thickness t1).

[0285] This suppresses the temperature rise of the second phosphor layer, and consequently, the temperature rise of wavelength conversion elements such as phosphor wheels.

[0286] (Technology 6) In the light source device described in any one of Techniques 1 to 5, the second fluorescence is not used as image light.

[0287] This allows the second fluorescence, which is not used as image light, to be utilized for detecting temperature rise in the wavelength conversion element.

[0288] (Technical 7) A projection-type image display device (for example, a projection-type image display device 400a) has a light source device as described in any one of Technical 1 to 6.

[0289] As a result, the projection-type image display device can achieve the same effects as those described in Technology 1, Technology 2, Technology 3, Technology 4, Technology 5, or Technology 6.

[0290] Although various embodiments have been described above with reference to the drawings, it goes without saying that this disclosure is not limited to these examples. It will be clear to those skilled in the art that various modifications, alterations, substitutions, additions, deletions, and equivalents can occur within the scope of the claims, and these will naturally fall within the technical scope of this disclosure. Furthermore, the components of the various embodiments described above can be combined arbitrarily without departing from the spirit of the invention.

[0291] For example, a light source device according to one embodiment of the present disclosure may include a wavelength conversion element different from that of a phosphor wheel instead of a phosphor wheel. Also, a light source device according to Embodiment 3, Embodiment 4, or Embodiment 5 may include a wavelength selection element different from that of a color wheel instead of a color wheel.

[0292] This disclosure is useful as a light source device and a projection-type image display device.

[0293] 10a, 10b, 10c, 10d, 10e Light source device 11, 20 Laser diode light source 12, 21 Collimator lens 13, 17, 18, 22, 27, 50, 51, 53, 55, 57, 501, 502, 503, 601, 604, 609, 613, 615, 617, 701, 702, 703 Convex lens 14, 23 Diffuser plate 15, 24 Concave lens 16a, 16b, 16c, 16d, 602, 608 Dichroic mirror 19a, 19b, 19c, 19e Phosphor wheel 25a, 25b, 25c, 25d Separation dichroic mirror 26 Sensor 28 Rod integrator 30 λ / 2 phase difference plate 31 Dichroic mirror with polarization separation function 32 λ / 4 phase difference plate 34 Fly-eye integrator 35 PBS array 40c, 40e Color wheel 52, 54, 56, 33, 603, 614, 616 Total reflection mirror 60 Composite mirror with blue light reflection region 61 Dichroic mirror with blue light reflection region 62 Blue light reflection region 100a, 100c, 100e Substrate 101, 102, 103 Phosphor layer 110 Reflective layer 120, 206, 306 Motor 130 Aperture 200 Holding part 201, 202, 203, 204, 301, 302, 303, 304 Region 300 Holding part 400a, 400b, 400c Projection type image display device 509, 510, 511, 704 DMD 512, 513, 514, 705 Microgap 507, 706 Total Internal Reflection Prism 508, 622, 707 Projection Lens 504, 505, 506 Glass Block 605 Red LCD Panel 606, 607, 611, 612, 619, 620 Polarizing Plate 610 Green LCD Panel 618 Blue LCD Panel 621 Cross-Cube Prism

Claims

1. A light source device comprising: a light source; a wavelength conversion element having a first phosphor layer comprising a first phosphor that wavelength-converts excitation light from the light source into first fluorescence; and a second phosphor layer comprising a second phosphor that wavelength-converts the excitation light or a portion of the first fluorescence into second fluorescence, wherein the ratio of the amount of light of the first fluorescence at a second temperature higher than the first temperature to the amount of light of the first fluorescence at a first temperature of the first phosphor contained in the first phosphor layer is greater than the ratio of the amount of light of the second fluorescence at a second temperature to the amount of light of the second fluorescence at a first temperature of the second phosphor contained in the second phosphor layer.

2. The light source device according to claim 1, comprising: an optical separation means disposed on the optical path of light from the wavelength conversion element for separating the second fluorescence from the light from the wavelength conversion element; an optical intensity measuring means for measuring the amount of light of the second fluorescence separated by the optical separation means; and a determination means for determining whether the amount of light of the second fluorescence measured by the optical intensity measuring means is less than a certain value.

3. The light source device according to claim 2, further comprising a control unit that performs temperature suppression control to suppress the temperature rise of the wavelength conversion element when the determination means determines that the amount of light of the second fluorescence measured by the light intensity measuring means is less than the constant value.

4. The light source device according to claim 1, wherein the second phosphor layer is provided on the first phosphor layer and is positioned on the side of the wavelength conversion element where the excitation light from the light source is incident.

5. The light source device according to claim 1, wherein the first phosphor layer is provided on the second phosphor layer and is positioned on the side of the wavelength conversion element where the excitation light from the light source is incident.

6. The light source device according to claim 1, wherein the thickness of the second phosphor layer is thinner than the thickness of the first phosphor layer.

7. A projection-type image display device having a light source device according to any one of claims 1 to 6.

8. The projection-type image display device according to claim 7, wherein the light emitted from the light source or the wavelength conversion element, other than the second fluorescence light, is used as image light.

Images