Light source device and image projection device

Abstract

To provide a wavelength conversion plate, a light source device, and an image projector that can increase the usage efficiency of light.SOLUTION: In a wavelength conversion plate having a conversion region in which a wavelength conversion member for generating a different color from that of an excitation light in reception of the excitation light is arranged and a reflection region which reflects the excitation light on a base surface, the reflection region has a transmission diffusion surface for diffusing the excitation light, a transmission layer, and a reflection surface. The transmission diffusion surface is located closer to the side where the excitation light enters than the surface of the wavelength conversion member on the side of the base surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention ,light The present invention relates to a source device and an image projection device. [Background technology]

[0002] Projectors (image projection devices) that enlarge and project various images are widely used today. A projector is a device that focuses light emitted from a light source onto a spatial light modulation element (image display element) such as a DMD (Digital Mirror Device) or a liquid crystal display element, and displays the emitted light (reflected light) from the spatial light modulation element modulated based on a video signal as a color image on a screen.

[0003] To project color images, at least three primary color illumination sources are required. While it is possible to generate all of these light sources using laser light sources, this is not desirable because the luminous efficiency of green and red lasers is lower than that of blue lasers. For this reason, the mainstream method is to irradiate a phosphor with a blue laser as excitation light, and generate red and green light from the fluorescent light that is wavelength-converted by the phosphor. On the other hand, since blue light can be used as excitation light directly, a lighting device technology is already known in which a portion of a phosphor substrate coated with phosphor is used as a reflective area, and the reflective area and the phosphor are sequentially switched to generate blue light and fluorescent light in a time-sequential manner.

[0004] Patent Document 1 discloses a technology in which a diffuse reflection surface that diffuses and reflects (diffusely reflects) light is provided on the surface of a metal substrate on which phosphors of a fluorescent wheel are arranged, and the light emission of a light source and an excitation light source is controlled in synchronization with the position of the diffuse reflection surface of the phosphor relative to the irradiation position of the excitation light. Patent Document 2 discloses a technology in which a light scattering layer in which minute scatterers are dispersed in a material is provided on a substrate. Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the diffusion structure on the reflection surface provided on the conventional wavelength conversion plate, the light-emitting position of the phosphor (the surface of the phosphor on which the excitation light is irradiated, as viewed from the side on which the excitation light is incident) and the diffusion position (the position of the transmission diffusion surface through which the excitation light first passes, as viewed from the side on which the excitation light is incident) are different, which means that the light utilization efficiency cannot be optimized for the fluorescence and the blue light, which is the excitation light source, and therefore the utilization efficiency cannot be improved.

[0006] In addition, with conventional technology, the fluorescence from the phosphor surface travels inside the phosphor, slightly blurring the illumination size of the excitation light irradiated on the phosphor surface, resulting in a fluorescence emission size that is larger than the illumination size of the excitation light. This results in a difference between the fluorescence emission size and the emission size of the excitation light at the excitation light transmission / diffusion surface. In other words, with conventional technology, there was a problem in that the optical system that captures both the fluorescence and the blue light from the excitation light source could not be optimized to achieve both, making it difficult to improve utilization efficiency.

[0007] The present invention has been made in view of the above, and is capable of improving the light utilization efficiency. Light The present invention aims to provide a source device and an image projection device. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object, the present invention provides: A light source device including a light source that emits excitation light, a wavelength conversion plate, and a focusing optical system that focuses the excitation light on the wavelength conversion plate, wherein the wavelength conversion plate The substrate surface has a conversion region in which a wavelength conversion member that receives excitation light and generates a color different from the color of the excitation light is arranged, and a reflection region that reflects the excitation light. death, the reflective area includes a transmissive diffusion surface that diffuses the excitation light, a transmissive layer, and a reflective surface; a distance between the base surface and the transmission-diffusion surface is greater than a thickness of the wavelength conversion member; the excitation light is incident on the transmission-diffusion surface, the transmission layer, and the reflection surface in this order; the wavelength conversion plate is moved by a movement mechanism; and the direction in which the excitation light is incident on the conversion region and the reflection region is at an angle of 45 degrees or more and 135 degrees or less with respect to the movement direction of the wavelength conversion plate. It is characterized by: [Effects of the Invention]

[0009] According to the present invention, the light source size of the excitation light that is irradiated onto the transmissive diffusion surface and becomes a secondary light source on the transmissive diffusion surface can be made closer to the emission size that spreads in the conversion region, thereby achieving the effect of increasing the utilization efficiency of the light wavelength-converted in the conversion region and the light captured by the excitation light. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a projector according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the light source unit. [Figure 3] FIG. 3 is a diagram illustrating an example of the configuration of a wavelength conversion element. [Figure 4] FIG. 4 is a diagram showing an example of reflection in a wavelength conversion element. [Figure 5] FIG. 5 is a conceptual diagram showing how light travels in a conventional wavelength conversion element. [Figure 6] FIG. 6 is a conceptual diagram showing how light travels in the wavelength conversion element of this embodiment. [Figure 7] FIG. 7 is a diagram showing a cross section of a wavelength conversion element according to a modified example. [Figure 8] FIG. 8 is a developed cross-sectional view of the wavelength conversion element according to the second embodiment. [Figure 9] FIG. 9 is a diagram showing the range of incident directions of excitation light according to the third embodiment. [Figure 10] FIG. 10 is an enlarged view showing the irradiation position of the excitation light. DETAILED DESCRIPTION OF THE INVENTION

[0011] Please refer to the attached drawings below. ,light An embodiment of the source device and the image projection device will now be described in detail.

[0012] (First embodiment) FIG. 1 is a schematic diagram showing the configuration of a projector 1 according to the first embodiment.

[0013] The projector (image projection device) 1 has a housing 10, a light source device 20, a light homogenizing element 30, an illumination optical system 40, an image forming element (image display element) 50, a projection optical system 60, a control device 80, and a color wheel 90.

[0014] The housing 10 houses a light source device 20, a light uniformizing element 30, an illumination optical system 40, an image forming element 50, a projection optical system 60, a control device 80, and a color wheel 90.

[0015] The light source device 20 emits light containing wavelengths corresponding to the respective colors of RGB, for example. The light source device 20 has a light source unit 20A, a light source unit 20B, and a light path combining element 20C, which is a combining unit. The light source unit 20A and the light source unit 20B have the same structure and emit light beams of a predetermined shape. The internal configurations of the light source unit 20A and the light source unit 20B will be described in detail later. The light beams emitted from the light source unit 20A and the light source unit 20B are deflected by the light path combining element 20C, respectively, and enter the incident side surface of the light uniformizing element 30. In this embodiment, a prism is shown as an example of the light path combining element 20C, but the present invention is not limited to this.

[0016] As shown in FIG. 1, in the projector 1, the light beams emitted from the light source unit 20A and the light source unit 20B in the opposing direction are reflected and deflected by two reflecting units (light path combining element 20C in FIG. 1) that are at an angle of approximately 90 degrees to each other, and are reflected in the same direction, and the respective focused light beams are combined by being adjacent to each other or partially overlapping, and then incident on the light uniformizing element 30 at the same time.

[0017] In this embodiment, the light source device 20 is shown as an example using two light source units 20A and 20B, but this is not limited to this, and the light source device 20 may be configured to use two or more light source units, for example, four light source units, and combine them.

[0018] The light uniformizing element 30 uniformizes the light emitted from the light source device 20 by mixing it. More specifically, the light uniformizing element 30 receives a light beam incident from its incident side, propagates it through its interior while repeatedly reflecting it, and emits it from its exit surface. The light uniformizing element 30 forms a uniform surface light source on its exit surface by internally reflecting the light beam incident from its incident side multiple times. Examples of the light uniformizing element 30 include a light tunnel with a hollow interior and four mirrors on the inner surface, a rod integrator formed into a rectangular pillar made of a transparent material such as glass, and a fly's eye lens. For example, when a light tunnel is used as the light uniformizing element 30, the aspect ratio of the light tunnel is approximately the same as that of the image forming element 50, and the shape of the exit of the light tunnel is projected onto the surface of the image forming element 50, thereby enabling efficient illumination of the surface of the image forming element 50 without waste.

[0019] The illumination optical system 40 substantially uniformly illuminates the image forming element 50 with the light homogenized by the light homogenizing element 30. The illumination optical system 40 has, for example, one or more lenses and one or more reflecting surfaces.

[0020] The image forming element 50 has a light valve such as a digital micromirror device (DMD), a transmissive liquid crystal panel, a reflective liquid crystal panel, etc. The image forming element 50 forms an image by modulating the light illuminated by the illumination optical system 40 (light from the light source optical system of the light source device 20).

[0021] The control device 80 switches the surface of the image forming element 50 pixel by pixel by reflecting or transmitting the illumination light irradiated onto the image forming element 50 according to the input image, and guides the light to the projection optical system 60 .

[0022] The projection optical system 60 enlarges and projects the image formed by the image forming element 50 onto a screen (projection surface) 70. The projection optical system 60 has, for example, one or more lenses. The projection optical system 60 has a conjugate relationship such that the image on the surface of the image forming element 50 is focused as an enlarged image at a desired position on the screen (projection surface) 70, so that the spatially modulated image is enlarged and projected onto the surface of the image forming element 50.

[0023] In addition, a color wheel 90 is provided at the light exit of the light uniforming element 30, and has the function of switching color filters to extract at least blue, green, and red light components. The color wheel 90 synchronizes the rotation of the wavelength conversion elements 26 (see FIG. 2, etc.) used in each of the light source units 20A and 20B with its own rotation to synchronously drive the color filter switching, and displays images on the surface of the image forming element 50 according to the switching timing, thereby displaying monochromatic images sequentially. Such switching time is faster than the response speed of the human eye, so the images are perceived as color images.

[0024] Fig. 2 is a schematic diagram showing the configuration of the light source unit 20A. The light source unit 20B has a similar configuration. Fig. 2(a) shows the state when blue laser light (first colored light) is generated, and Fig. 2(b) shows the state when fluorescent light (second colored light) is generated.

[0025] The light source section 20A (20B) has, arranged in order in the propagation direction of light, laser light sources (excitation light sources) 21, collimator lenses 22 provided corresponding to each light source, a first lens group 23, a dichroic mirror 24, a second lens group 25, a wavelength conversion element 26 which is a wavelength conversion plate, and a third lens group 27. For example, the components of the light source device 20 excluding the laser light source 21 constitute a "light source optical system." The light source section 20A (20B) has the above-mentioned components arranged in the propagation order of the excitation light emitted from the laser light source 21.

[0026] The laser light source 21 has a plurality of light sources (light emitting points). So-called laser diodes are used as the laser light source 21. In FIG. 2, six light sources are drawn aligned in the vertical direction, but in reality, the six light sources are aligned in four rows in the direction perpendicular to the plane of the paper (depth direction), resulting in a two-dimensional arrangement of 6 × 4 = 24 light sources. Each light source of the laser light source 21 emits, for example, light in the blue band (blue laser light) with a center wavelength of 440 nm to 465 nm in emission intensity as excitation light for exciting the phosphor included in the wavelength conversion element 26.

[0027] The blue laser light (first color light) emitted from each light source of the laser light source 21 is linearly polarized light with a fixed polarization state, and is arranged to be S-polarized with respect to the dichroic mirror 24. The blue laser light emitted from each light source of the laser light source 21 is coherent light. Furthermore, the excitation light emitted from each light source of the laser light source 21 may be light of a wavelength that can excite the phosphor included in the wavelength conversion element 26, and is not limited to light in the blue band.

[0028] Although the laser light source 21 uses a plurality of light sources in this example, it may use a single laser light source. Also, the laser light source 21 may use light source units arranged in an array on a substrate, but is not limited to this.

[0029] There are provided 24 collimator lenses 22 corresponding to the 24 light sources of the laser light source 21. Each collimator lens 22 adjusts the excitation light emitted from each light source of the laser light source 21 to become approximately parallel light. The number of collimator lenses 22 only needs to correspond to the number of light sources of the laser light source 21, and can be increased or decreased according to an increase or decrease in the number of light sources of the laser light source 21.

[0030] The excitation light emitted from the laser light sources 21 is converted into approximately parallel light by the collimator lenses 22 corresponding to each light source of the laser light sources 21. The approximately parallel excitation light is reduced by the first lens group 23 and converted into a thin beam, and is guided to the dichroic mirror 24.

[0031] The dichroic mirror 24 is a parallel-flat glass plate. The dichroic mirror 24 has a coating on the incident surface that reflects S-polarized light (first polarization component) in the wavelength band of the excitation light guided from the first lens group 23 and transmits P-polarized light (second polarization component) in the wavelength band of the excitation light guided from the first lens group 23 and the fluorescent light (second color light) from the wavelength conversion element 26.

[0032] The dichroic mirror 24 has its center shifted with respect to the optical axis of the second lens group 25, and the excitation light is incident on the wavelength conversion element 26 at an angle with respect to the normal to the wavelength conversion element 26.

[0033] In this embodiment, a flat dichroic mirror 24 is used, but a prism type can also be used. In this embodiment, the dichroic mirror 24 reflects S-polarized light in the wavelength band of the excitation light and transmits P-polarized light, but conversely, it may reflect P-polarized light in the wavelength band of the excitation light and transmit S-polarized light.

[0034] As shown in Fig. 2(a), the excitation light reflected by the dichroic mirror 24 is guided to the wavelength conversion element 26 by the second lens group 25, which is a focusing optical system, and a desired focused spot is formed on the wavelength conversion element 26. The excitation light reflected by the blue reflection region A3 (see Fig. 3) of the wavelength conversion element 26 passes through the second lens group 25 again, passes through the opposite side of the optical axis of the second lens group 25 from the dichroic mirror 24, transmits through the third lens group 27, is deflected by the light path combining element 20C, and enters the light uniformizing element 30. The light uniformizing element 30 uniformizes the incident light.

[0035] As shown in FIG. 2(b), when excitation light is incident on the phosphor regions (yellow phosphor region A1 and green phosphor region A2: see FIG. 3) of the wavelength conversion element 26, the phosphor regions (yellow phosphor region A1 and green phosphor region A2) receive the excitation light and emit wavelength-converted fluorescence 360 ​​degrees around the fluorescent molecules. The fluorescence emitted from the phosphor regions of the wavelength conversion element 26 contains a yellow or green component. The excitation light reflected by the surface (substrate surface) of the substrate 26a (see FIG. 3) of the wavelength conversion element 26 passes through the phosphor regions (yellow phosphor region A1 and green phosphor region A2) again and emits fluorescence with a Lambertian distribution on the surface side of the phosphor regions (yellow phosphor region A1 and green phosphor region A2). The fluorescence emitted from the phosphor regions (yellow phosphor region A1 and green phosphor region A2) of the wavelength conversion element 26 is guided to the light uniformizing element 30 via the light path combining element 20C (omitted in FIG. 2). More specifically, the fluorescent light is converted into approximately parallel light by the second lens group 25, refracted by the third lens group 27 so as to be focused near the light uniformizing element 30, deflected by the light path combining element 20C, and incident on the light uniformizing element 30.

[0036] FIG. 3 is a diagram showing an example of the configuration of the wavelength conversion element 26. As shown in FIG.

[0037] Fig. 3(a) is a plan view of the wavelength conversion element 26. As shown in Fig. 3(a), the wavelength conversion element 26 according to this embodiment is disk-shaped. The wavelength conversion element 26 is a wavelength conversion plate in which three segments, namely, a yellow phosphor region (first wavelength conversion region) A1 which is a conversion region including a wavelength conversion member (phosphor) 26f, a green phosphor region (second wavelength conversion region) A2 which is a conversion region including a wavelength conversion member (phosphor) 26g, and a blue reflection region A3 which reflects light emitted from the laser light source (excitation light source) 21 (in other words, a non-conversion region which emits light received from the laser light source (excitation light source) 21 without converting the wavelength of the light), are formed in strips around the periphery of the disk-shaped plate at desired angles.

[0038] The yellow phosphor region A1 is formed of, for example, yellow phosphor 26f that receives blue laser light as excitation light and emits fluorescence in a yellow wavelength band, and the green phosphor region A2 is formed of, for example, green phosphor 26g that receives blue laser light as excitation light and emits fluorescence in a green wavelength band.

[0039] In this embodiment, two types of phosphors, the yellow phosphor region A1 and the green phosphor region A2, are used, but the present invention is not limited to this. For example, only the yellow phosphor region A1 may be used, or a red phosphor region may be further added.

[0040] The color wheel 90 is equipped with color filters that extract desired color components from the phosphor. By sequentially switching the color filters, the color wheel 90 extracts the required color components, such as green and red components, from the fluorescent light in a time-division manner. To switch the color filters sequentially in this way, a segment is provided for each color filter, and the segments are rotated by a rotary motor to sequentially switch the desired color filters.

[0041] The disk-shaped wavelength conversion element 26 is rotated by a drive unit controlled by the control device 80, thereby being able to move periodically and sequentially between the yellow phosphor region A1, the green phosphor region A2, and the blue reflective region A3. The drive unit, which is the movement mechanism, is usually preferably a rotary motor M. As wavelength conversion element 26 is rotated by the drive unit, the yellow phosphor region A1, the green phosphor region A2, and the blue reflective region A3 are switched at the light-focusing spot, which is the position where light is irradiated from the laser light source (excitation light source) 21, and light of different wavelengths is emitted in a time-division manner.

[0042] In addition, the light source unit 20A (20B) places a light absorbing or reflecting member on the wheel of the wavelength conversion element 26 or on the member that supports and rotates the wheel, and detects it with a photocoupler, etc., to make the rotation speeds of the two wavelength conversion elements 26 the same.

[0043] Fig. 3(b) is a cross-sectional view taken along line A-A' in Fig. 3(a). As shown in Fig. 3(b), the wavelength conversion element 26 includes a transparent flat plate 26c, which is a transparent flat member, on a disk-shaped substrate 26a via an adhesive layer 26b in the blue reflection region A3. As described above, the laser light source 21 emits, as excitation light, light in the blue band (blue laser light) having a center wavelength of 440 nm to 465 nm in emission intensity.

[0044] 3(b), flat plate 26c constituting blue reflection region A3 includes a transmission-diffusion surface 261 that diffuses the excitation light, a transmission layer 262 that transmits the excitation light, and a reflection surface 263 that reflects the excitation light. One surface of flat plate 26c is transmission-diffusion surface 261, and the other surface facing transmission-diffusion surface 261 is reflection surface 263. Flat plate 26c is formed from a BK7 glass plate, quartz glass with high thermal conductivity, sapphire, synthetic glass, or the like.

[0045] The transmissive diffusing surface 261 of the flat plate 26c is formed by roughening the glass surface. For example, techniques that produce a frosted glass appearance, such as sandblasting or etching with a solvent, can be used for roughening. The transmissive diffusing surface 261 of the flat plate 26c may also be formed using tiny prisms or microlenses. Note that the transmissive diffusing surface here refers to a surface that does not deflect light in a fixed direction at the interface, but rather spreads the light beam to a certain extent as it passes through.

[0046] The reflecting surface 263 of the flat plate 26c may be formed by a conventional method for forming a normal mirror. For example, a thin film of a metal such as aluminum may be formed on the flat plate 26c by vapor deposition or sputtering. Alternatively, a reflective film that increases the reflectance in the wavelength range of the excitation light may be formed on the flat plate 26c. Since the reflective film is a thin film, its thickness can be almost ignored. Specifically, a dielectric multilayer film, for which mass production methods have been established, may be formed on the flat plate 26c.

[0047] As shown in FIG. 3(b), when the blue laser light passes through the transmissive diffusion surface 261 of the flat plate 26c, the light beam diverges at a certain angle from the main light ray. As shown in FIG. 3(b), the diverged light beam passes through the flat plate 26c and reaches the reflective surface 263 opposite the transmissive diffusion surface 261. The light beam that has passed through the flat plate 26c is specularly reflected by the reflective surface 263, reaches the incident surface (the transmissive diffusion surface 261) again, and then diverges at a certain angle before exiting the flat plate 26c. The flat plate 26c is designed so that the light beam diverges at a slight angle from the transmissive diffusion surface 261 upon exiting. The divergence angle is preferably several degrees, ranging from several degrees to 10 degrees, and is at most approximately 20 degrees. The blue laser light basically passes through the transmissive diffusion surface 261 of the flat plate 26c twice. Therefore, the light beam reflected by the reflecting surface 263 of the flat plate 26c is diffused at an angle approximately twice the diffusion angle of the transmissive diffusing surface 261 before being emitted. Therefore, the transmissive diffusing surface 261 of the flat plate 26c only needs to be configured to have a diffusion angle that is approximately half the desired diffusion angle of the reflected light. Therefore, when it is desired to diffuse light by a desired angle, it is sufficient to configure the transmissive diffusing surface 261 with a diffusion angle that is approximately half that angle, which makes it easier to form the transmissive diffusing surface 261.

[0048] As a result, the blue laser light incident on the reflecting surface 263 of the flat plate 26c at a certain angle passes through the transmitting diffusion surface 261, which has a slight diffusion angle, twice, thereby being optimized to have the desired luminous flux spread.

[0049] Here, we explain the necessity of diffusing the excitation light, which is blue laser light. To realize a projector 1 with practical brightness, a brightness of several thousand lumens is required. To achieve this, the excitation light must have a power of at least several tens of watts. A laser light source 21 in the blue wavelength band is a promising light source with a power of several tens of watts. A so-called laser diode is used as the laser light source 21. While laser diodes are effective light sources capable of producing high output, their light tends to propagate in a straight line and exhibits high coherence, which can easily cause glare, or speckle, in the projected image. To resolve this issue, the laser light passes through a diffusing member, which reduces the directivity and coherence. While a diffuser plate is typically placed in the optical path of the laser light to reduce speckle, this embodiment reduces speckle by placing a transmissive diffusing surface 261 in the optical path of the light focused on the phosphor (close to the focal point).

[0050] As shown in Figure 3(b), the position of the transmitting diffusion surface 261 of the flat plate 26c that is closest from the direction of incidence of the blue laser light becomes the emission position of the blue light source reflected from the reflecting surface 263 of the flat plate 26c, and is taken in and used by the optical system at the subsequent stage.

[0051] Here, Fig. 4 is a diagram showing an example of reflection in wavelength conversion element 26. Fig. 4(a) shows how blue laser light enters blue reflection region A3, Fig. 4(b) shows how blue laser light is diffusely reflected by blue reflection region A3, and Fig. 4(c) shows how blue laser light enters phosphor regions (yellow phosphor region A1 and green phosphor region A2) and emits fluorescence.

[0052] 4(a) and 4(b), when blue laser light is incident on the blue reflection region A3 of the wavelength conversion element 26 from an oblique direction, the spot size (excitation light irradiation region) of the blue laser light formed on the transmission diffusion surface 261 is diffused by the transmission diffusion surface 261 of the flat plate 26c and is reflected by the reflection surface 263 of the flat plate 26c. As a result, the diffused light spreads, and the light beam reflected by the reflection surface 263 of the flat plate 26c is again incident on the transmission diffusion surface 261 from the back side and passes through the transmission diffusion surface 261 for the second time, and the converged spot on the transmission diffusion surface 261 becomes larger than when it was incident and is emitted.

[0053] On the other hand, as shown in FIG. 4(c), when the wavelength conversion element 26 is rotated and blue laser light is incident obliquely on the phosphor regions (yellow phosphor region A1 and green phosphor region A2) of the wavelength conversion element 26 shown in cross section C-C' of FIG. 3(a), the blue laser light acts as excitation light. Note that the wavelength conversion element 26 has the phosphor regions (yellow phosphor region A1 and green phosphor region A2) formed on the reflecting surface 26d of the base 26a. In this case, the surfaces of the phosphors 26f and 26g in the phosphor regions (yellow phosphor region A1 and green phosphor region A2) slightly expand to emit fluorescence. In this way, the emission size on the transmitting / diffusing surface 261 where excitation light is emitted from the blue reflecting region A3 approaches or becomes equal to the light source size of the fluorescence expanded in the phosphor regions (yellow phosphor region A1 and green phosphor region A2).

[0054] If such a configuration is not adopted, the spot size of the focused spot will be small and will become diffused light, and it will appear as if blue light is being emitted on the transmissive diffusion surface 261, so that the small emission size will be taken into the light uniformizing element 30 and illuminate the panel. In this case, an illumination optical system designed with priority given to the fluorescent emission size will encounter the problem of not being able to uniformize the small blue emission size.

[0055] Returning to the explanation of Figure 3, Figure 3(c) is an expanded view of the cross section taken along line B-B' in Figure 3(a). As shown in Figure 3(c), the blue reflection region A3 is composed of a transmission diffusion surface 261 that diffuses the excitation light, a transmission layer 262, and a reflection surface 263.

[0056] The wavelength conversion element 26 has a yellow phosphor region A1, a green phosphor region A2, and a blue-reflecting region A3 formed continuously in an annular shape. Because they are formed continuously in an annular shape, the yellow phosphor region A1, the green phosphor region A2, and the blue-reflecting region A3 are adjacent to each other. That is, as shown in FIG. 3(c), when a cross section B-B' along the arc is developed, the green phosphor region A2 is followed by the blue-reflecting region A3 and the yellow phosphor region A1. Because the yellow phosphor region A1, the green phosphor region A2, and the blue-reflecting region A3 are continuous in this way, the time it takes for the focused spot to cross the boundary between the two regions can be minimized. This makes it possible to reduce light loss due to the so-called spoke time.

[0057] As shown in FIG. 3(c), the transmission-diffusing surface 261 of the blue reflection region A3 is located closer to the excitation light incident side than the surfaces of the phosphors 26f and 26g that constitute the wavelength conversion member phosphor regions (yellow phosphor region A1 and green phosphor region A2) on the base surface 26a side. More specifically, in the example shown in FIG. 3(c), the height of the blue reflection region A3 is higher than the heights of the yellow phosphor region A1 and the green phosphor region A2. That is, the position of the transmission-diffusing surface 261 formed in the blue reflection region A3 is closer to the surfaces of the yellow phosphor region A1 and the green phosphor region A2 when viewed from the excitation light source incident side. In other words, this is equivalent to the distance between the base 26a and the transmission-diffusing surface 261 of the flat plate 26c being a finite value. Here, "high" refers to a relative positional relationship.

[0058] Generally, the yellow phosphor region A1 and the green phosphor region A2 of the wavelength conversion element 26 are coated on the surface of the substrate 26a with a finite thickness. Since the yellow phosphor region A1 and the green phosphor region A2 formed on the substrate 26a have a finite thickness, they will inevitably be separated from the surface of the substrate 26a.

[0059] Also, when determining the positional relationship between the surface side of the blue reflection region A3 and the substrate 26a, it is agreed that the position of the transmission diffusion surface 261 of the flat plate 26c is formed at a finite distance on the surface side of the wavelength conversion element 26.

[0060] As shown in FIG. 3(c), in the present embodiment, when the thickness of the yellow phosphor region A1 and the green phosphor region A2 is k and the height of the transmission diffusion surface 261 of the flat plate 26c of the blue reflection region A3 from the surface of the substrate 26a is h, the height of the transmission diffusion surface 261 of the flat plate 26c of the blue reflection region A3 is determined so as to satisfy the following relationship. k < h < 2k Note that when h becomes 2k, it corresponds to a height that is twice the thickness of the yellow phosphor region A1 and the green phosphor region A2.

[0061] Note that when the height h of the transmission diffusion surface 261 of the flat plate 26c of the blue reflection region A3 from the surface of the substrate 26a is twice or more the thickness of the yellow phosphor region A1 and the green phosphor region A2, it becomes almost equal to the efficiency in the state where h is 0, and the effect decreases. That is, in order to increase the efficiency compared to the prior art, by setting the height h of the transmission diffusion surface 261 of the flat plate 26c of the blue reflection region A3 from the surface of the substrate 26a within the range of k < h < 2k, the light utilization efficiency will increase at each stage.

[0062] Ideally, the heights of the surfaces of the yellow phosphor region A1 and the green phosphor region A2 and the transmitting / diffusing surface 261 of the flat plate 26c of the blue reflective region A3 are the same (the same distance from the second lens group 25), i.e., h = k. However, because the yellow phosphor region A1 and the green phosphor region A2 and the blue reflective region A3 are separate members, strictly speaking, some level difference occurs during the process of manufacturing the wavelength conversion element 26. In this embodiment, the allowable range of the level difference is specified.

[0063] The transmission-diffusion surface 261 of the flat plate 26c in the blue reflection region A3 diffuses the blue laser light, which serves as the excitation light, and becomes a light source serving as a secondary light source. Meanwhile, the yellow phosphor region A1 and the green phosphor region A2 convert the blue excitation light to a longer wavelength. That is, the wavelength acting on the transmission-diffusion surface 261 of the flat plate 26c in the blue reflection region A3 is shorter than the wavelength emitted as fluorescence from the yellow phosphor region A1 and the green phosphor region A2, and some chromatic aberration occurs. A shorter wavelength can shorten the back focus, thereby improving the light collection efficiency.

[0064] For example, the transmissive diffusing surface 261 of the flat plate 26c in the blue reflective region A3 is at a height of about 0.3 mm (300 μm) from the surface of the base 26a, and the thickness of the yellow phosphor region A1 and the green phosphor region A2 is about 0.2 mm (200 μm).

[0065] Next, the effects of this embodiment will be described.

[0066] Here, FIG. 5 is a conceptual diagram showing how light travels in a conventional wavelength conversion element, and FIG. 6 is a conceptual diagram showing how light travels in the wavelength conversion element 26 of this embodiment.

[0067] Ideally, the surfaces of the phosphor regions (yellow phosphor region A1 and green phosphor region A2) and the entrance of light homogenizing element 30, such as a light tunnel, should be in an optically conjugate relationship. In other words, the distance between the phosphor regions (yellow phosphor region A1 and green phosphor region A2) and the light-collecting element formed by second lens group 25 and third lens group 27 is determined and set so that the focused spot of excitation light is positioned at its smallest on the surfaces of the phosphor regions.

[0068] Since the size of the fluorescence light source depends on the size of the focused spot, the position of the wavelength conversion element 26 determines the size of the fluorescence light source. In other words, to utilize fluorescence more efficiently, it is desirable to have a smaller focused spot. Therefore, the wavelength conversion element 26 is positioned so that the excitation light forms as small a focused spot as possible through the optical system. Typically, the focused spot size of the excitation light is about several mm, and in some cases it may be 1 mm or even smaller.

[0069] As shown in Fig. 5, in the conventional technology, the diffusion surface is spaced apart from the light-collecting element formed by the second lens group 25 and the third lens group 27 by the thickness of the phosphor layer in the phosphor regions (yellow phosphor region A1 and green phosphor region A2). As shown in Fig. 5, when the phosphor regions (yellow phosphor region A1 and green phosphor region A2) are irradiated with excitation light and emit fluorescence, the fluorescence emission point becomes an object point (position A). Light diverging from the object point (position A) is collected by the second lens group 25 and then collected near the entrance of the light uniformizing element 30 by the third lens group 27. In other words, the surfaces of the phosphor regions (yellow phosphor region A1 and green phosphor region A2) and the entrance of the light uniformizing element 30 are arranged in an optically conjugate relationship.

[0070] As shown in Fig. 5, when the conventional wavelength conversion element is rotated and the excitation light is reflected from the diffusing surface, the diffusing surface is separated from the light-collecting element formed by the second lens group 25 and the third lens group 27 (position B). In this state, the conjugate position of position B is located before the entrance of the light uniformizing element 30, as shown in Fig. 5. In this state, the blue laser light reflected back from the diffusing surface reaches the entrance of the light uniformizing element 30 as a divergent beam, and a considerable amount of light is not captured by the light uniformizing element 30, resulting in a decrease in light utilization efficiency.

[0071] In contrast, as shown in Figure 6, when the wavelength conversion element 26 of this embodiment is adopted, by approximately aligning the positions of the surfaces of the phosphor regions (yellow phosphor region A1 and green phosphor region A2) and the transmissive diffusion surface 261 of the flat plate 26c of the blue reflection region A3, it is possible to align the optical conjugate position with the entrance of the light homogenizing element 30, and an optimal positional relationship can be maintained for both fluorescent light and blue light, thereby reducing light loss.

[0072] Thus, according to this embodiment, the transmission diffusion surface 261 of the blue reflection region A3 is positioned higher than the surface including the back surface of the phosphor regions (yellow phosphor region A1 and green phosphor region A2) which are wavelength conversion members, and therefore the light source size of the excitation light that becomes a secondary light source on the transmission diffusion surface 261 when irradiated with excitation light on the transmission diffusion surface 261 can be made closer to the emission size that spreads in the conversion region, and the utilization efficiency of the light wavelength-converted in the conversion region and the light taken in by the excitation light can be made equivalent.

[0073] Also, the transmissive diffusing surface 261 of the blue reflection region A3 is positioned closer to the incident side of the excitation light than the surfaces of the phosphor regions (the yellow phosphor region A1 and the green phosphor region A2). By doing so, the transmissive diffusing surface 261 can be made closer to the surfaces of the phosphor regions (the yellow phosphor region A1 and the green phosphor region A2). As a result, both the wavelength-converted light and the reflected light of the excitation light can be effectively utilized as illumination light without a reduction in efficiency. More specifically, the transmissive diffusing surface 261 diffuses the blue light, which is the excitation light, and the transmissive diffusing surface 261 serves as a secondary light source and a light-emitting source. On the other hand, fluorescence is converted to a longer wavelength than the blue excitation light. That is, the wavelength acting on the transmissive diffusing surface 261 and the wavelength emitted as fluorescence have a chromatic aberration because the wavelength acting on the transmissive diffusing surface 261 is shorter. Since a shorter wavelength can shorten the back focus, the light collection efficiency can be increased.

[0074] That is, according to the projector 1 of the present embodiment, the blue light directly outputs and uses the blue of the laser diode light source as it is, but by passing through the transmissive diffusing surface 261 of the blue reflection region A3 twice, it is possible to ensure uniformity and at the same time mitigate the reduction of the laser light speckle, and a high-quality projected image can be obtained.

[0075] In the present embodiment, when the thickness of the yellow phosphor region A1 and the green phosphor region A2 is k and the height of the transmissive diffusing surface 261 of the flat plate 26c of the blue reflection region A3 from the surface of the base 26a is h, the height of the transmissive diffusing surface 261 of the flat plate 26c of the blue reflection region A3 is determined so as to satisfy the following relationship. k < h < 2k However, it is not limited to this, and 0 < h < 2k may be used. In the prior art, the transmissive diffusing surface 261 was separated from the surface of the phosphor layer by the thickness of the phosphor layer as seen from the condenser lens. That is, it was at the position where h = 0. By bringing the transmissive diffusing surface 261 closer to the condenser lens than this state, that is, by setting h > 0, the light utilization efficiency of the wavelength-converted light (fluorescence) and the illumination device using the excitation light as blue light can be increased by approaching the fluorescent surface and focusing.

[0076] Further, the transmissive diffusing surface 261 of the flat plate 26c in the blue reflection region A3 may be made to coincide with the positions of the surfaces of the yellow phosphor region A1 and the green phosphor region A2 when viewed from the side where the excitation light is incident. That is, when the thickness of the yellow phosphor region A1 and the green phosphor region A2 is k, and the height of the transmissive diffusing surface 261 of the flat plate 26c in the blue reflection region A3 from the surface of the base 26a is h, the height of the transmissive diffusing surface 261 of the flat plate 26c in the blue reflection region A3 may be determined so as to satisfy the following relationship. k = h The distance (back focus) from the second lens group 25 for taking in fluorescence and diffused light is extremely close. On the other hand, when the wavelength conversion element 26 is rotated, the surface of the second lens group 25 moves rapidly on the wavelength conversion element 26 while maintaining a slight gap. Therefore, by eliminating the step on the wavelength conversion element 26, it is possible to prevent the wind noise and physical obstacles.

[0077] Note that the transmissive diffusing surface `261` does not necessarily have to be arbitrarily separated from the base `26a`. If there is an ideal focal position, usually, considering robustness, as a normal optical design, it is designed to be optimal at the ideal focal position. For example, in the prior art, when optimized at the position of the fluorescent surface, the transmissive diffusing surface `261` is set so that the light collection efficiency of the reflected light at the transmissive diffusing surface `261` can be ensured at a distance of +k deeper (by the thickness of the yellow phosphor region A1 and the green phosphor region A2) as viewed from the condenser lens. Without special design, usually, conversely, even if the focus is moved -k forward, the performance is often substantially equivalent to the original position separated by a distance of +k (characteristics regarding focus shift are usually targeted). Even without special ingenuity in design, if the technical idea of the present invention is used, if the transmissive diffusing surface `261` is set to be within Δk (smaller than ±k) from the fluorescent surface, it can be said that at least the efficiency is improved compared to the prior art. Therefore, by setting the height of the transmissive diffusing surface `261` to 0 < h < 2k, it will be located inside the relative deviation of ±k from the height of the fluorescent surface, so the efficiency is higher than the position where h = 0.

[0078] (Modification example) Next, a modification example will be described.

[0079] 7A and 7B are cross-sectional views of a wavelength conversion element 26 according to a modified example, in which Fig. 7A is a cross-sectional view of the blue reflection region A3, and Fig. 7B is a cross-sectional view of the phosphor regions (yellow phosphor region A1 and green phosphor region A2).

[0080] As shown in Fig. 7, wavelength conversion element 26 of the modified example has a circular or arc-shaped groove 26e along the outer periphery of base 26a. In wavelength conversion element 26, yellow phosphor region A1, green phosphor region A2, and blue reflective region A3 are formed in groove 26e formed in base 26a. As shown in Fig. 7, the bottom surface of groove 26e, which is in contact with yellow phosphor region A1, green phosphor region A2, and blue reflective region A3, forms the surface of base 26a, and transmissive diffusing surface 261 of flat plate 26c is positioned at a finite distance from the bottom surface of groove 26e.

[0081] (Second embodiment) Next, a second embodiment will be described.

[0082] The second embodiment differs from the first embodiment in that light transmitted through flat plate 26c in blue reflection region A3 is reflected by the surface of base 26a in wavelength conversion element 26. In the following description of the second embodiment, the same parts as those in the first embodiment will be omitted, and only the parts that differ from the first embodiment will be described.

[0083] Here, Fig. 8 is a developed view of a cross section of the wavelength conversion element 26 according to the second embodiment. Fig. 3(b) only shows the state of diffusion on the outermost surface, but the actual behavior of light is as shown in Fig. 6, in which the light spreads from the main ray by a diffusion angle on the transmitting and diffusing surface 261 of the flat plate 26c in the blue reflection region A3, is reflected by the reflecting surface 263 of the flat plate 26c, and is diffused again when traveling in the opposite direction on the transmitting and diffusing surface 261.

[0084] 8, in the wavelength conversion element 26 according to this embodiment, the surface of the flat plate 26c is a transmissive diffusion surface 261, and the other surface opposite to the transmissive diffusion surface 261 is a transmissive surface, and light is reflected by the surface of the base 26a. The surface of the flat plate 26c opposite to the transmissive diffusion surface 261 is attached to the surface of the base 26a, which is a reflective surface 26d, via a transparent adhesive layer 26b.

[0085] In wavelength conversion element 26, phosphor regions (yellow phosphor region A1 and green phosphor region A2) are formed on reflective surface 26d of base 26a, and reflective surface 26d can be continuously formed as a reflective surface for excitation light (blue light). In other words, no reflective layer is required on flat plate 26c, and wavelength conversion element 26 can be configured at low cost.

[0086] In order to obtain a practical illumination output, an output of several tens of watts is usually required from the blue laser light source. Since the spot light of several tens of watts is concentrated and passes through the transmission-diffusion surface 261 of the flat plate 26c, the flat plate 26c must be heat-resistant to some extent. Therefore, it is sufficient that the flat plate 26c is thermally connected to at least a member with high thermal conductivity, such as metal. In other words, by connecting the flat plate 26c to the base 26a via the adhesive layer 26b, the heat received by the irradiation can be dissipated, and a highly reliable wavelength conversion element 26 can be provided.

[0087] In each embodiment, the wavelength conversion element 26, which is a wavelength conversion plate, is provided in the projector (image projection device) 1, but the present invention is not limited to this and can be widely applied to devices that temporally mix fluorescent light and a blue excitation light source to obtain a white color. For example, the wavelength conversion element 26, which is a wavelength conversion plate, can also be applied to lighting devices such as searchlights and spotlights.

[0088] (Third embodiment) Next, a third embodiment will be described.

[0089] The third embodiment differs from the first and second embodiments in that the range of the incident direction of the excitation light is specified. In the following description of the third embodiment, the description of the same parts as the first and second embodiments will be omitted, and only the parts that differ from the first and second embodiments will be described.

[0090] If excitation light is incident along the direction of rotation (movement direction) of the conversion region (yellow phosphor region (first wavelength conversion region) A1, green phosphor region (second wavelength conversion region) A2) and the reflection region (blue reflection region A3), there is a problem that the beam spreads in the movement direction. Therefore, in this embodiment, the excitation light emitted from the laser light source 21 is incident from a range of 45° to 135° with respect to the movement direction (rotation direction) of the wavelength conversion element 26.

[0091] 9 is a diagram showing the range of incident directions of excitation light according to the third embodiment. The dashed arrow P shown in FIG. 9 is a tangent to the driving (rotation direction) of the wavelength conversion element 26. The excitation light emitted from the laser light source 21 is incident in a direction of 45° to 135° (can be from either the upper or lower side) with respect to the direction along the tangent shown in FIG.

[0092] Fig. 10 is an enlarged view showing the irradiation position of the excitation light. The excitation light emitted from the laser light source 21 is incident from the range (45° to 135°) indicated by the two arrows Q shown in Fig. 10. The ellipse shown in Fig. 10 indicates the focused spot of the excitation light. As shown in Fig. 10, the spot light spreads in the direction perpendicular to the movement direction of the conversion regions (yellow phosphor region (first wavelength conversion region) A1, green phosphor region (second wavelength conversion region) A2).

[0093] Here, we will explain the case where excitation light emitted from the laser light source 21 is incident in a direction of 0° to 45° or 135° to 180° as shown in Fig. 10. In this case, the focused spot of the excitation light becomes an ellipse with the major axis in that direction, and the beam spread direction becomes longer, resulting in color mixing and reduced light utilization efficiency. The spread of light is as explained in Figs. 3 and 4.

[0094] As described above, according to this embodiment, beam spread occurs due to the conversion regions (yellow phosphor region (first wavelength conversion region) A1, green phosphor region (second wavelength conversion region) A2), but since the incident direction of the excitation light into the reflection region is set to be between 45 degrees and 135 degrees, spread at the boundary between the reflection region and the conversion region can be minimized. In particular, when the incident direction of the excitation light into the reflection region is set to approximately 90 degrees, spread in the movement direction is minimized, so spread in the spoke portion can be suppressed and a more efficient illumination optical system can be obtained.

[0095] Although the above-described embodiments show preferred examples of the present invention, the present invention is not limited to those examples.

[0096] In particular, the specific shapes and numerical values ​​of each part illustrated in each of the above-mentioned embodiments are merely examples of the embodiments that may be implemented when carrying out the present invention, and the technical scope of the present invention should not be interpreted in a limited manner based on these.

[0097] As described above, the present invention is not limited to the details explained in the above-described embodiments, and can be modified as appropriate within the scope of the gist thereof. [Explanation of symbols]

[0098] 1. Image projection device 20 Light source device 21 Light source 25 Condensing optical system 26 Wavelength conversion plate 26a Foundation 26c Transparent flat plate member 26d reflective surface 30 Light uniformizing element 50 Image display element 60 Projection optical system 261 Transmissive Diffusive Surface 262 Transparent layer 263 Reflective surface A1,A2 transformation domain A3 reflective area M Moving mechanism [Prior art documents] [Patent documents]

[0099] [Patent Document 1] Patent No. 6305009 [Patent Document 2] Japanese Patent Application Publication No. 2017-181602

Claims

1. A light source device comprising: a light source that emits excitation light; a wavelength conversion plate; and a focusing optical system that focuses the excitation light on the wavelength conversion plate, the wavelength conversion plate has, on a base surface, a conversion region in which a wavelength conversion member is arranged that receives excitation light and generates a color different from the color of the excitation light, and a reflective region that reflects the excitation light; the reflective area includes a transmission diffusion surface that diffuses the excitation light, a transmission layer that transmits the excitation light, and a reflection surface that reflects the excitation light, a distance between the base surface and the transmission-diffusion surface is greater than a thickness of the wavelength conversion member; the excitation light is incident on the transmissive diffusing surface, the transmissive layer, and the reflective surface in this order; the wavelength conversion plate is moved by a moving mechanism; a direction in which the excitation light is incident on the conversion region and the reflection region is set to be 45 degrees or more and 135 degrees or less with respect to a moving direction of the wavelength conversion plate; A light source device characterized by:

2. When the thickness of the wavelength conversion member is k and the distance between the base surface and the transmission diffusion surface is h, the position of the transmission diffusion surface is determined so as to satisfy the following relationship: k<h<2k 2. The light source device according to claim 1.

3. the reflective area comprises a transparent flat plate member; the transmission diffusion surface is provided on one surface of the transparent flat plate member, the other surface of the transparent flat plate member facing the transmission-diffusion surface is in contact with the base surface, or the other surface facing the transmission-diffusion surface is thermally coupled to the base surface via an adhesive layer; 3. The light source device according to claim 1, wherein the light source device is a light source unit.

4. the other surface of the transparent flat plate member opposite the transmission-diffusion surface reflects the excitation light; 4. The light source device according to claim 3, wherein:

5. the other surface of the transparent flat plate member opposite the transmission-diffusion surface transmits the excitation light; 4. The light source device according to claim 3.

6. the excitation light emitted by the light source is blue light; the wavelength conversion plate receives the blue light and converts it into a wavelength having at least a green light component and a red light component; 2. The light source device according to claim 1.

7. a direction in which the excitation light is incident on the conversion region and the reflection region is set to be approximately 90 degrees with respect to a moving direction of the wavelength conversion plate; 2. The light source device according to claim 1.

8. The light source device according to any one of claims 1 to 7; a light uniformizing element that uniformizes the light incident from the light source device and emits the uniform light; an image display element that modulates the light from the light uniformizing element to form an image; a projection optical system that enlarges and projects the image onto a projection surface; An image projection device comprising:

Images