JP6557983B2 - projector - Google Patents

Description

  The present invention relates to a lighting device and a projector.

  2. Description of the Related Art An illumination device is known that includes a solid-state light source such as a semiconductor laser and a phosphor layer that generates fluorescence by using light emitted from the solid-state light source as excitation light. For example, in the following Patent Document 1, a semiconductor laser light source, a light separation element, a phosphor, a first reflection element, a quarter phase plate, a diffusion plate, and a second reflection element are included. A light source device is disclosed.

  In this light source device, the excitation light emitted from the semiconductor laser light source enters the light separation element and is separated into two lights by the light separation element having polarization separation characteristics. One of the lights separated by the light separation element is irradiated to the phosphor as excitation light, and fluorescence is emitted. The fluorescence is reflected toward the light separation element by the first reflection element, and is emitted to the outside through the light separation element. The other light out of the light separated by the light separation element is adjusted in the polarization state by the ¼ phase difference plate, diffused by the diffusion plate while maintaining the polarization direction, and by the second reflection element. The light is reflected toward the light separation element through the ¼ phase difference plate and is emitted to the outside through the light separation element.

JP 2013-250494 A

  In the light source device of Patent Document 1, among the light emitted from the solid light source, the light emitted outside without being irradiated on the phosphor layer is for the purpose of making the illuminance distribution uniform and eliminating speckle noise. It is diffused by the diffusion plate. In order to use diffused light with high efficiency, for example, right circularly polarized light needs to be converted to left circularly polarized light when diffusely reflected by the diffuser and reflector. However, when the light diffusion angle by the diffusion plate is increased, the polarization holding ratio is lowered. When the polarization holding ratio decreases, the amount of light emitted to the outside via the light separation element decreases. That is, the utilization efficiency of diffused light is reduced. Therefore, the diffusion angle is set to 13 ° or less in order to make the polarization holding ratio 95% or more. However, light diffusion is insufficient at this level, and the effect of making the illuminance distribution uniform and the effect of improving speckle noise cannot be obtained sufficiently.

Further, the configuration for setting the diffusion angle of the diffusion plate to 13 ° or less is not specifically described. If the diffusion angle of the diffusion plate is too small, there is a problem that unevenness of color occurs due to an increase in the difference between the diffusion angle of blue light and the diffusion angle of yellow light. Therefore, it is necessary to appropriately set the diffusion angle of the diffuse reflection element.

  One aspect of the present invention has been made to solve at least one of the above-described problems, and can achieve uniform illumination distribution and improvement of speckle noise while suppressing a decrease in light utilization efficiency. Another object is to provide a lighting device. Another object is to realize a projector with high display quality by including the illumination device.

  In order to achieve the above object, an illumination device according to one aspect of the present invention includes a light source device that emits third light including a first component in a first polarization state, and the third light is incident. The polarization separation element, the phase difference element on which the first component is incident via the polarization separation element, and a concavo-convex structure including a plurality of curved surfaces, and the polarization state is changed by transmitting through the phase difference element A diffuse reflection element on which the first component is incident, and the first component reflected by the diffuse reflection element and transmitted through the phase difference element is different from the first polarization state. The fourth component having two polarization states is configured to be emitted through the polarization separation element.

  According to said structure, the 1st component contained in the 3rd light inject | emitted from the light source device injects into a diffuse reflection element via a polarization separation element and a phase difference element, and is diffusing by a diffuse reflection element After being reflected, the light is again emitted from the illumination device via the phase difference element and the polarization separation element. Since the diffuse reflection element has a concavo-convex structure including a plurality of curved surfaces, when the first component is reflected by the diffuse reflection element, disturbance of the polarization state is suppressed and the diffusion angle is increased. be able to. Thereby, it is possible to realize an illuminating device capable of making the illuminance distribution uniform and improving speckle noise while suppressing a decrease in the utilization efficiency of the first component.

In the illumination device according to one aspect of the present invention, the plurality of curved surfaces may be randomly arranged in a plan view.
According to this configuration, the effect of uniformizing the illuminance distribution and the effect of improving speckle noise can be further enhanced as compared with the case where a plurality of curved surfaces are regularly arranged.

In the illumination device according to one aspect of the present invention, the diffuse reflection element may have the concavo-convex structure on a surface on which the first component is incident, and the concavo-convex structure may have reflectivity.
According to this configuration, for example, unlike the case of reflection on the surface opposite to the surface on which the first component is incident, light loss due to the diffuse reflection element is small, and the light use efficiency can be increased.

In the illumination device according to one aspect of the present invention, a metal reflective film may be provided on the surface of the uneven structure.
According to this configuration, the reflection characteristics are less likely to deteriorate even when the incident angle of light changes, compared to the case where a reflective film made of a dielectric multilayer film is used, for example. As a result, light loss due to the diffuse reflection element is reduced, and the light use efficiency can be increased.

  In the illumination device according to one aspect of the present invention, in the uneven structure, the light amount of the fourth component emitted through the polarization separation element replaces the diffuse reflection element with a reflection element having a flat reflection surface. It may be configured to be 75% or more of the amount of light obtained in the case of.

  The inventors examined the correlation between the shape of the concavo-convex structure and the light utilization efficiency by changing the shape of the concavo-convex structure of the diffuse reflection element. In this specification, the light use efficiency is defined as the amount of light of the fourth component emitted through the polarization separation element and the reflection element having a flat reflection surface (that is, the linearly polarized light incident vertically). It means the ratio of the amount of light obtained when it is replaced with a reflective element whose polarization state is maintained at 100%. According to the examination results of the present inventors, in the region where the ratio value is 75% or more, the ratio value changes gently with respect to the change in the shape of the concavo-convex structure, while the ratio value is less than 75%. It was found that the ratio value suddenly changed in the region of. In the illumination device according to one aspect of the present invention, the uneven structure is obtained when the light amount of the fourth component emitted through the polarization separation element replaces the diffuse reflection element with a reflection element having a flat reflection surface. Since it is comprised so that it may become 75% or more of the light quantity obtained, light utilization efficiency can be maintained within an appropriate range.

  In the illumination device according to one aspect of the present invention, the third light includes a second component of the second polarization state, and the polarization separation element has a wavelength different from the wavelength of the third light. A phosphor layer on which the second component from the light source device that is transmitted regardless of the polarization state and reflected by the polarization separation element is incident, and a surface on which the second component of the phosphor layer is incident And a reflection part that reflects light generated by the phosphor layer, and may be further provided.

  According to the above configuration, the second component contained in the third light is reflected by the polarization separation element and enters the fluorescent layer to excite the phosphor. The light generated by the phosphor layer and the light diffusely reflected by the diffuse reflection element are combined by the polarization separation element, and then the combined light is emitted from the illumination device. In this way, illumination light in which fluorescent light and diffused light are combined is obtained.

  In the illumination device according to one aspect of the present invention, the third light includes a second component of the second polarization state, and the polarization separation element has a wavelength different from the wavelength of the third light. A phosphor layer on which the second component from the light source device that reflects light regardless of the polarization state and transmits the polarization separation element is incident, and a surface on which the second component of the phosphor layer is incident And a reflection part that reflects light generated by the phosphor layer, and may be further provided.

  According to said structure, the 2nd component contained in 3rd light permeate | transmits a polarized light separation element, injects into a fluorescence layer, and excites a fluorescent substance. The light generated by the phosphor layer and the light diffusely reflected by the diffuse reflection element are combined by the polarization separation element, and then the combined light is emitted from the illumination device. In this way, illumination light in which fluorescent light and diffused light are combined is obtained.

In the illumination device according to one aspect of the present invention, when the color unevenness in the illuminated area when the diffuse reflection element is replaced with the reflection element is set as the reference color unevenness, the uneven structure has the color unevenness as the reference color. You may be comprised so that it may become 90% or less of nonuniformity.
According to the examination results of the present inventors, if the color unevenness in the illuminated area is 90% or less of the color unevenness obtained when the diffuse reflection element is replaced with a reflective element having a flat reflecting surface, the color unevenness is obtained. Was almost unrecognizable. Details will be described later.

In the illumination device according to one aspect of the present invention, the uneven structure may be configured such that the color unevenness is 50% or less of the reference color unevenness. In this case, the aspect ratio of the concavo-convex structure is preferably 0.002 or more.
According to the examination results of the present inventors, it has been found that when the above conditions are satisfied, a state with little color unevenness can be stably maintained. Details will be described later.

In the illumination device according to one aspect of the present invention, the diffuse reflection element may be rotatable in a plane intersecting a central axis of the first component incident on the diffuse reflection element.
According to this configuration, since the irradiation position of the first component on the diffuse reflection element changes with time, damage to the diffuse reflection element due to irradiation with the first component can be reduced. In addition, since the concavo-convex structure located on the optical path of the first component changes with time, the effect of uniformizing the illuminance distribution and the effect of improving speckle noise can be further enhanced.

In the illumination device according to one aspect of the present invention, the uneven structure may have a shape that does not cause multiple reflection.
According to this configuration, the polarization holding ratio in the diffuse reflection element can be more reliably increased.

A projector according to an aspect of the present invention includes an illumination device according to an aspect of the present invention, a light modulation device that forms image light by modulating light emitted from the illumination device according to image information, A projection optical system for projecting image light.
According to this configuration, a projector with high display quality can be realized by including the illumination device according to one aspect of the present invention.

1 is a diagram illustrating a schematic configuration of a projector according to a first embodiment of the invention. It is a top view which shows schematic structure of the illuminating device of 1st Embodiment. (A)-(c) It is sectional drawing which shows the structural example of a diffused reflection board. It is a top view of a diffuse reflection board. It is a schematic block diagram of the projector of 2nd Embodiment of this invention. It is a schematic block diagram which shows the illuminating device of 2nd Embodiment. It is sectional drawing which shows the diffuse reflection element of embodiment. It is a graph which shows the relationship between the aspect-ratio of a diffuse reflection element, and light quantity ratio. It is a graph which shows the relationship between the aspect-ratio of a diffuse reflection element, and a color nonuniformity relative ratio. It is the graph which compared the color nonuniformity by the presence or absence of the randomness of the aspect ratio of an uneven structure. It is a schematic block diagram of the illuminating device of 3rd Embodiment of this invention.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The projector according to the present embodiment is an example of a liquid crystal projector including an illumination device using a semiconductor laser.
In the drawings used in the following description, in order to make the characteristics easy to see, a part of the drawings may be shown in an enlarged manner, and the dimensional ratios and the like of each component are not always the same as actual.

[projector]
First, an example of the projector 1 shown in FIG. 1 will be described.
FIG. 1 is a plan view showing a schematic configuration of the projector 1.

  The projector 1 according to the present embodiment is a projection type image display device that displays a color video (image) on a screen (projection surface) SCR. The projector 1 uses three light modulation devices corresponding to each color light of red light LR, green light LG, and blue light LB. The projector 1 uses a semiconductor laser (laser light source) from which light with high luminance and high output can be obtained as a light source of an illumination device.

  Specifically, as shown in FIG. 1, the projector 1 includes an illumination device 2, a uniform illumination optical system 40, a color separation optical system 3, a light modulation device 4R, a light modulation device 4G, and a light modulation device 4B. A synthesis optical system 5 and a projection optical system 6 are roughly provided.

  The illumination device 2 emits illumination light WL toward the uniform illumination optical system 40. As the lighting device 2, a lighting device to which one embodiment of the present invention described later is applied is used.

  The uniform illumination optical system 40 includes an integrator optical system 31, a polarization conversion element 32, and a superimposing optical system 33. The uniform illumination optical system 40 uniformizes the intensity distribution of the illumination light WL emitted from the illumination device 2 in the illuminated area. The illumination light WL emitted from the uniform illumination optical system 40 enters the color separation optical system 3.

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

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

  The first total reflection mirror 8a is disposed in the optical path of the red light LR, and reflects the red light LR transmitted through the first dichroic mirror 7a toward the light modulation device 4R. On the other hand, the second total reflection mirror 8b and the third total reflection mirror 8c are arranged in the optical path of the blue light LB, and direct the blue light LB transmitted through the second dichroic mirror 7b toward the light modulation device 4B. reflect. It is not necessary to arrange a total reflection mirror in the optical path of the green light LG, and the green light LG is reflected toward the light modulation device 4G by the second dichroic mirror 7b.

  The first relay lens 9a and the second relay lens 9b are arranged on the light emission side of the second dichroic mirror 7b in the optical path of the blue light LB. The first relay lens 9a and the second relay lens 9b function to compensate for the optical loss of the blue light LB caused by the optical path length of the blue light LB being longer than the optical path lengths of the red light LR and the green light LG. have.

  The light modulation device 4R modulates the red light LR according to image information while allowing the red light LR to pass therethrough, thereby forming red image light. The light modulation device 4G modulates the green light LG according to the image information while allowing the green light LG to pass through, thereby forming green image light. The light modulation device 4B modulates the blue light LB according to the image information while passing the blue light LB to form blue image light.

  For example, a transmissive liquid crystal panel is used for the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. A polarizing plate (not shown) is disposed on each of the incident side and the emission side of each liquid crystal panel.

  A field lens 10R, a field lens 10G, and a field lens 10B are disposed on the incident side of the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, respectively. The field lens 10R, the field lens 10G, and the field lens 10B are for parallelizing the red light LR, the green light LG, and the blue light LB incident on the respective light modulation devices 4R, 4G, and 4B. It is.

  The combining optical system 5 receives image light from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. The combining optical system 5 combines the incident image light and emits the combined image light toward the projection optical system 6. For example, a cross dichroic prism is used for the combining optical system 5.

  The projection optical system 6 is composed of a projection lens group. The projection optical system 6 enlarges and projects the image light combined by the combining optical system 5 toward the screen SCR. Thereby, an enlarged color video (image) is displayed on the screen SCR.

[Lighting device]
Next, a specific embodiment of a lighting device to which one aspect of the present invention used for the lighting device 2 is applied will be described.

The illumination device 20A shown in FIG. 2 will be described.
FIG. 2 is a plan view showing a schematic configuration of the illumination device 20A.

As shown in FIG. 2, the illumination device 20A includes an array light source 21A, a collimator optical system 22, an afocal optical system 23, a homogenizer optical system 24, an optical element 25A including a polarization separation element 50A, a first Pickup optical system 26, fluorescent light emitting element 27, phase difference plate 28, second pickup optical system 29, and diffuse reflection element 30 are roughly provided.
The diffuse reflection element 30 of the present embodiment corresponds to the diffuse reflection element in the claims. The polarization separation element 50A of the present embodiment corresponds to the polarization separation element in the claims. The retardation plate 28 of the present embodiment corresponds to the retardation element in the claims.

  Array light source (light source device) 21A, collimator optical system 22, afocal optical system 23, homogenizer optical system 24, optical element 25A, phase difference plate 28, second pickup optical system 29, and diffusion The reflective elements 30 are sequentially arranged on the optical axis ax1. The fluorescent light emitting element 27, the first pickup optical system 26, and the optical element 25A are sequentially arranged on the optical axis ax2. The optical axis ax1 and the optical axis ax2 are in the same plane and are in a positional relationship orthogonal to each other.

  The array light source 21A corresponds to the light source device in the present invention. The array light source 21A includes a first semiconductor laser 211 that is a first light source and a second semiconductor laser 212 that is a second light source. The plurality of first semiconductor lasers 211 and the plurality of second semiconductor lasers 212 are arranged in an array in the same plane orthogonal to the optical axis ax1.

  The first semiconductor laser 211 emits blue light BL ′ that is first light in the first wavelength band. The first light corresponds to the first component in the claims. The first semiconductor laser 211 emits laser light having a peak wavelength of 460 nm, for example, as blue light BL ′. The second semiconductor laser 212 is a laser light source for excitation light that emits excitation light BL that is second light in the second wavelength band. The second light corresponds to the second component in the claims. The second semiconductor laser 212 emits laser light having a peak wavelength of 446 nm, for example, as the excitation light BL.

  The excitation light BL and the blue light BL ′ are emitted from the array light source 21A toward the polarization separation element 50A.

  Excitation light BL and blue light BL ′ emitted from the array light source 21 </ b> A enter the collimator optical system 22. The collimator optical system 22 converts the excitation light BL and the blue light BL ′ emitted from the array light source 21 </ b> A into parallel light beams. The collimator optical system 22 is composed of, for example, a plurality of collimator lenses 22a arranged in an array. The plurality of collimator lenses 22a are arranged corresponding to the plurality of first semiconductor lasers 211 and the plurality of second semiconductor lasers 212, respectively.

  Each excitation light BL and blue light BL ′ converted into a parallel light beam by passing through the collimator optical system 22 is incident on the afocal optical system 23. The afocal optical system 23 adjusts the beam diameters of the excitation light BL and the blue light BL ′. The afocal optical system 23 includes, for example, an afocal lens 23a and an afocal lens 23b.

  Excitation light BL and blue light BL ′ whose beam diameters are adjusted by passing through the afocal optical system 23 are incident on the homogenizer optical system 24. The homogenizer optical system 24 converts the light intensity distribution of the excitation light BL and the blue light BL ′ into a uniform state (so-called top hat distribution). The homogenizer optical system 24 includes, for example, a multi-lens array 24a and a multi-lens array 24b.

  The excitation light BL and the blue light BL ′ that have been converted to a uniform light intensity distribution by the homogenizer optical system 24 are incident on the optical element 25A. The optical element 25A is composed of, for example, a dichroic prism having wavelength selectivity. The dichroic prism has an inclined surface K that forms an angle of 45 ° with the optical axis ax1. The inclined surface K forms an angle of 45 ° with respect to the optical axis ax2. The optical element 25A is arranged so that the intersection of the optical axes ax1 and ax2 orthogonal to each other coincides with the optical center of the inclined surface K. The optical element 25A is not limited to a prism shape such as a dichroic prism, and a parallel plate dichroic mirror may be used.

  On the inclined surface K, a polarization separation element 50A having wavelength selectivity is provided. The polarization separation element 50A converts the excitation light BL and the blue light BL ′ into the S polarization component (one polarization component or the second polarization state component) and the P polarization component (the other polarization component or the first polarization component) for the polarization separation element 50A. The polarization separation function is separated into components of the polarization state). Specifically, the polarization separation element 50A reflects the S-polarized component of the excitation light BL and the S-polarized component of the blue light BL ′, and transmits the P-polarized component of the excitation light BL and the P-polarized component of the blue light BL ′.

  In addition, the polarization separation element 50A has a color separation function that transmits fluorescent light YL having different wavelength bands between excitation light BL and blue light BL ′, which will be described later, regardless of the polarization state.

  Here, the excitation light BL and the blue light BL ′ are coherent linearly polarized light. Further, the excitation light BL and the blue light BL 'have different polarization directions when entering the polarization separation element 50A.

  Specifically, the polarization direction of the excitation light BL coincides with the polarization direction of one polarization component (for example, S polarization component) reflected by the polarization separation element 50A. On the other hand, the polarization direction of the blue light BL ′ coincides with the polarization direction of the other polarization component (for example, P polarization component) transmitted by the polarization separation element 50A. Thus, when entering the polarization separation element 50A, the polarization direction of the excitation light BL and the polarization direction of the blue light BL 'are orthogonal to each other. In order to realize this configuration, the polarization direction when the blue light BL ′ is emitted from the first semiconductor laser 211 is orthogonal to the polarization direction when the excitation light BL is emitted from the second semiconductor laser 212. Thus, the first semiconductor laser 211 and the second semiconductor laser 212 may be disposed.

  Accordingly, the excitation light BL incident on the polarization separation element 50A is reflected toward the fluorescent light emitting element 27 as S-polarized excitation light BLs because the polarization direction of the excitation light BL coincides with the S-polarization component. On the other hand, the blue light BL ′ incident on the polarization separation element 50 </ b> A is transmitted toward the diffuse reflection element 30 as the P-polarized blue light BLp ′ because the polarization direction coincides with the P-polarized light component.

  Here, a case where the polarization direction of the excitation light BL is the same as the polarization direction of the blue light BL ′ when entering the polarization separation element 50 </ b> A will be considered. In this case, since the blue light BL ′ is P-polarized light, the excitation light BL is also P-polarized light. In order for the polarization separation element 50A to reflect the P-polarized excitation light BL, the polarization separation element 50A has a polarization separation function with respect to the blue light BL ′ having a peak wavelength of 460 nm, and the excitation light BL having a peak wavelength of 446 nm. On the other hand, it must not have a polarization separation function. However, it is difficult to manufacture a polarization separation element having such characteristics.

  On the other hand, in the present embodiment, the excitation light BL is S-polarized light, and the blue light BL ′ is P-polarized light. In this case, the polarization separation element 50A may have a polarization separation function not only for the blue light BL ′ having a peak wavelength of 460 nm but also for the excitation light BL having a peak wavelength of 446 nm. For this reason, it is easy to manufacture the polarization separation element.

  The S-polarized excitation light BLs emitted from the polarization separation element 50 </ b> A is incident on the first pickup optical system 26. The first pickup optical system 26 focuses the excitation light BLs toward the phosphor layer 34 of the fluorescent light emitting element 27. The first pickup optical system 26 includes, for example, a pickup lens 26a and a pickup lens 26b.

  The excitation light BLs emitted from the first pickup optical system 26 enters the fluorescent light emitting element 27. The fluorescent light emitting element 27 includes a phosphor layer 34, a substrate 35 that supports the phosphor layer 34, and a fixing member 36 that fixes the phosphor layer 34 to the substrate 35.

  The fluorescent light emitting element 27 is provided between the side surface of the phosphor layer 34 and the substrate 35 in a state where the surface of the phosphor layer 34 opposite to the side on which the excitation light BLs is incident is in contact with the substrate 35. The phosphor layer 34 is fixedly supported on the substrate 35 by the fixing member 36.

  The phosphor layer 34 includes a phosphor that is excited by absorbing the excitation light BLs having a wavelength of 446 nm. The phosphor excited by the excitation light BLs generates fluorescent light (yellow light) YL having a peak wavelength in a wavelength range of 500 to 700 nm, for example.

  For the phosphor layer 34, it is preferable to use a layer excellent in heat resistance and surface processability. As such a phosphor layer 34, for example, a phosphor layer in which phosphor particles are dispersed in an inorganic binder such as alumina, a phosphor layer in which phosphor particles are sintered without using a binder, and the like are preferably used. be able to.

A reflective portion 37 is provided on the side of the phosphor layer 34 opposite to the side on which the excitation light BLs is incident. The reflection unit 37 has a function of reflecting a part of the fluorescent light YL among the fluorescent light YL generated by the phosphor layer 34.
The reflection part 37 of this embodiment corresponds to the reflection part in the claims.

  It is preferable that the reflection part 37 consists of a specular reflection surface. In the fluorescent light emitting element 27, the fluorescent light YL generated in the fluorescent material layer 34 is specularly reflected by the reflecting portion 37, whereby the fluorescent light YL can be efficiently emitted from the fluorescent material layer 34.

  Specifically, the reflecting portion 37 can be configured by providing a reflecting film 37a on the surface of the phosphor layer 34 opposite to the side on which the excitation light BLs is incident. In this case, the surface of the reflective film 37a facing the phosphor layer 34 is a specular reflection surface. The reflection part 37 may be configured such that the substrate 35 is made of a base material having light reflection characteristics. In this case, the reflective film 37a is omitted, and the surface of the substrate 35 facing the phosphor layer 34 is made into a mirror surface, so that this surface can be used as a mirror reflection surface.

  For the fixing member 36, it is preferable to use an inorganic adhesive having light reflection characteristics. In this case, the light leaking from the side surface of the phosphor layer 34 can be reflected into the phosphor layer 34 by the inorganic adhesive having light reflection characteristics. Thereby, the light extraction efficiency of the fluorescent light YL generated by the phosphor layer 34 can be further increased.

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

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

  Since the fluorescent light YL emitted from the phosphor layer 34 is non-polarized light whose polarization direction is not uniform, after passing through the first pickup optical system 26, it enters the polarization separation element 50A while remaining in a non-polarized state. . The fluorescent light YL is transmitted from the polarization separation element 50A toward the integrator optical system 31.

  The P-polarized blue light BLp ′ emitted from the polarization separation element 50 </ b> A enters the phase difference plate 28. The phase difference plate 28 is composed of a ¼ wavelength plate (λ / 4 plate) disposed in the optical path between the polarization separation element 50 </ b> A and the diffuse reflection element 30. Accordingly, the P-polarized blue light BLp ′ emitted from the polarization separation element 50A is converted into circularly-polarized blue light BLc ′ by transmitting through the phase difference plate 28, and then is transmitted to the second pickup optical system 29. Incident.

  The second pickup optical system 29 collects the blue light BLc ′ toward the diffuse reflection element 30. The second pickup optical system 29 includes, for example, a pickup lens 29a and a pickup lens 29b.

  The diffuse reflection element 30 diffuses and reflects the blue light BLc ′ emitted from the second pickup optical system 29 toward the polarization separation element 50A. Among them, as the diffuse reflection element 30, it is preferable to use an element that causes Lambert reflection of the blue light BLc ′ incident on the diffuse reflection element 30.

  The diffuse reflection element 30 includes a diffuse reflection plate 30A and a drive source 30M such as a motor for rotating the diffuse reflection plate 30A. The rotation axis of the drive source 30M is disposed substantially parallel to the optical axis ax1. Accordingly, the diffuse reflector 30A is configured to be rotatable within a plane that intersects the central axis of the blue light BLc 'incident on the diffuse reflector 30A. The diffuse reflection plate 30A is formed, for example, in a circular shape when viewed from the direction of the rotation axis.

FIG. 3A is a cross-sectional view of the diffuse reflector 30A.
For example, the diffuse reflector 30 </ b> A shown in FIG. 3A includes a base material 43 and a reflective film 44. The base material 43 is comprised with arbitrary materials, such as glass, for example.

  Of the two surfaces of the base material 43, a concavo-convex structure 43a including a plurality of randomly arranged curved surfaces is provided on the surface on which the blue light BLc 'is incident. In the present embodiment, the concavo-convex structure 43a is composed of a plurality of recesses, and each recess is formed in a substantially spherical shape. The depth of the recess is, for example, about 1/4 of the diameter of the entire spherical surface.

  As shown in FIG. 4, the plurality of recesses are randomly arranged when the diffusive reflector 30 </ b> A is viewed from the light incident direction. 4 indicates the center of each recess, and the centers C of the plurality of recesses are randomly arranged.

  The reflection film 44 is a metal reflection film formed of a metal having a high light reflectance such as silver or aluminum. The reflective film 44 is formed along the shape of the concavo-convex structure 43a, and the surface of the reflective film 44 also has a substantially spherical shape. Since the reflective film 44 is formed on the surface of the uneven structure 43a, the uneven structure 43a has reflectivity. When the blue light BLc ′ is incident on the formation surface of the reflection film 44 of the diffuse reflection plate 30A, the blue light BLc ′ is emitted by one reflection, and multiple reflection does not occur. Thereby, disturbance of the polarization state when the blue light BLc ′ is reflected by the diffuse reflector 30A is suppressed.

  The reflection film 44 is not limited to a metal reflection film, and for example, a dielectric multilayer film can be used. However, when a metal reflection film is used as the reflection film 44, the reflection characteristics are less likely to deteriorate even if the incident angle of light changes, compared to the case where a reflection film made of a dielectric multilayer film is used. As a result, light loss due to the diffusive reflector 30A is reduced, and the light use efficiency can be increased.

When manufacturing the diffuse reflection plate 30A, first, an etching prevention film such as chromium is formed on one surface of a substrate such as glass.
Next, a plurality of holes are formed in the etching prevention film by laser processing or the like. At this time, in the laser processing machine, the coordinates of the formation position are set so that the positions of the plurality of holes to be formed are randomly arranged. As a result, a plurality of randomly arranged holes are formed in the etching prevention film.

Next, using the etching prevention film as a mask, one surface of the substrate is etched by, for example, wet etching. At this time, the wet etching conditions are adjusted to be isotropic etching. When etching is performed in this manner, the etching solution penetrates from the hole portion of the etching preventing film, and a recess is formed at a position corresponding to the hole. Since the etching is isotropic etching, the etching proceeds isotropically with the hole as a center, and as a result, the cross-sectional shape of the recess becomes substantially spherical.
Next, a metal film such as silver or aluminum is formed on one surface of the base material on which the concavo-convex structure is formed by a sputtering method, a vapor deposition method, or the like.
With the above method, the diffuse reflector 30A is completed.

3B and 3C are cross-sectional views of other examples of the diffuse reflector (diffuse reflector 30B and diffuse reflector 30C). Instead of the diffuse reflector 30A, a diffuse reflector 30B or a diffuse reflector 30C may be used.
In the diffuse reflector 30B shown in FIG. 3B, the base material 45 is formed of a metal such as silver or aluminum. Of the two surfaces of the base material 45, a concavo-convex structure 45a including a plurality of randomly arranged curved surfaces is provided on the surface on which the blue light BLc ′ is incident. The shape of the uneven structure 45a is the same as the shape of the uneven structure 43a in FIG. In this configuration, since the substrate 45 itself has light reflectivity, it is not necessary to form a metal film on the substrate 45.

  A diffuse reflection plate 30 </ b> C illustrated in FIG. 3C includes a base material 46 and a reflection film 47. The base material 46 is made of an arbitrary material such as glass. Of the two surfaces of the base material 46, a concavo-convex structure 46a including a plurality of randomly arranged curved surfaces is provided on the surface on which the blue light BLc 'is incident. The shape of the uneven structure 46a is the same as the shape of the uneven structure 43a in FIG. A reflective film 47 made of a metal such as silver or aluminum is formed on the surface opposite to the surface on which the blue light BLc ′ is incident, of the two surfaces of the substrate 46.

  Any of the diffuse reflectors shown in FIGS. 3A to 3C may be used as the diffuse reflector of the present embodiment. However, from the viewpoint that the loss of light is small, the surface on which the blue light BLc ′ is incident is light-reflecting like the diffuse reflector 30A in FIG. 3A or the diffuse reflector 30B in FIG. Those having properties are preferred. This is because there is a possibility of light loss when the blue light BLc ′ is incident on the base material 46 as in the diffusing reflection plate 30 </ b> C of FIG.

  3A to 3C include a plurality of concave portions arranged at random, but may include a plurality of concave portions arranged regularly. However, when a plurality of concave portions are regularly arranged, a diffraction phenomenon may occur, but an effect of suppressing a decrease in the utilization efficiency of the first light can be obtained.

  In the illuminating device 20A, by using such a diffuse reflection element 30, it is possible to diffusely reflect the blue light BLc 'and obtain the blue light BLc' having a substantially uniform illuminance distribution.

  As shown in FIG. 2, the blue light BLc ′ diffusely reflected by the diffuse reflection element 30 passes through the second pickup optical system 29 again and enters the phase difference plate 28 to be converted into blue light BLs ′. The The blue light BLs' is incident on the polarization separation element 50A. As described above, the blue light BLc ′ before entering the diffuse reflection element 30 is circularly polarized light. If the polarization state of the blue light BLc ′ is not disturbed at all by the diffuse reflection element 30, the blue light BLs ′ is S-polarized light and does not include the P-polarized component. Even if the polarization state of the blue light BLc ′ is disturbed to some extent by the diffuse reflection element 30, the main component of the blue light BLs ′ is the S-polarized component. The S-polarized component of the blue light BLs ′ is reflected by the polarization separation element 50A. The S-polarized component of the blue light BLs ′ reflected by the polarization separation element 50A corresponds to the fourth component in the claims.

  As a result, the blue light BLs ′ is emitted from the illumination device 20A as the illumination light WL together with the fluorescent light YL transmitted through the polarization separation element 50A. That is, the blue light BLs ′ and the fluorescent light YL are emitted in the same direction from the polarization separation element 50A. Thereby, illumination light (white light) WL obtained by combining the blue light BLs ′ and the fluorescent light (yellow light) YL is obtained.

  The illumination light WL emitted from the illumination device 20A enters the integrator optical system 31. The integrator optical system 31 is for making the luminance distribution (illuminance distribution) uniform. The integrator optical system 31 includes, for example, a lens array 31a and a lens array 31b. The lens arrays 31a and 31b are made up of a plurality of microlenses arranged in an array.

  The illumination light WL that has passed through the integrator optical system 31 enters the polarization conversion element 32. The polarization conversion element 32 aligns the polarization direction of the illumination light WL. The polarization conversion element 32 includes, for example, a polarization separation film and a phase difference plate. The polarization conversion element 32 aligns the polarization direction of the fluorescent light YL whose polarization direction is not uniform and the polarization direction of the S-polarized blue light BLs ′, so that the other polarization component is changed to one polarization component (for example, a P polarization component). Is converted into an S-polarized component.

  The illumination light WL whose polarization direction is aligned by passing through the polarization conversion element 32 enters the superimposing optical system 33. The superimposing optical system 33 superimposes the illumination light WL emitted from the polarization conversion element 32. The superimposing optical system 33 is composed of, for example, a superimposing lens. The illuminance distribution in the illuminated area is made uniform by the integrator optical system 31 and the superimposing optical system 33.

  In the illuminating device 20A having the above-described configuration, since the diffuse reflector 30A has an uneven structure including a plurality of randomly arranged curved surfaces, the blue light BLc ′ is reflected by the diffuse reflector 30A. In this case, disturbance of the polarization state is suppressed, and the diffusion angle can be increased.

  If the polarization state of the blue light BLc ′ is greatly disturbed by the diffuse reflector 30A, the P-polarized component contained in the blue light BLs ′ increases, and the component reflected by the polarization separation element 50A decreases. However, according to the present invention, since the P-polarized component contained in the blue light BLs ′ can be reduced, it is possible to suppress a decrease in the amount of the blue light BLs ′ emitted from the illumination device 20A. As a result, it is possible to realize an illuminating device 20A capable of making the illuminance distribution uniform and improving speckle noise while suppressing a decrease in the utilization efficiency of the first light.

  In particular, in the case of the present embodiment, since the diffuse reflection element 30 includes the diffuse reflection plate 30A that is rotatable, the irradiation position of the blue light BLc ′ on the diffuse reflection element 30 changes with time. Therefore, it is possible to reduce damage to the diffuse reflector 30A due to the irradiation with the blue light BLc '. In addition, since the concavo-convex structure located on the optical path of the blue light BLc ′ changes with time, the effect of uniformizing the illuminance distribution and the effect of improving speckle noise can be further enhanced.

  In the illuminating device 20A, the fluorescent light YL generated by exciting the phosphor layer 34 with the excitation light BLs, and the blue light BLs ′ obtained by diffusing and reflecting the blue light BLp ′ with the diffuse reflection element 30. Can be used to obtain illumination light WL excellent in color purity and color reproducibility.

  That is, the blue light BL ′ having a peak wavelength of 460 nm is blue light having higher visibility than the excitation light BL having a peak wavelength of 446 nm. In addition, a wider color gamut can be obtained when light having a peak wavelength of 460 nm is used than when light having a peak wavelength of 446 nm is used. That is, light having a peak wavelength of 460 nm is more suitable for forming a color image than light having a peak wavelength of 446 nm. Therefore, when the illumination light WL is obtained using the blue light BL ′ having a peak wavelength of 460 nm and the fluorescent light YL, the illumination light WL is obtained using the excitation light BL and the fluorescent light YL having a peak wavelength of 446 nm. It is possible to improve the color gamut (color reproduction range) of the illumination light WL than the case.

  Further, the second semiconductor laser 212 that emits the excitation light BL is generally less expensive than the first semiconductor laser 211 that emits the blue light BL ′. Accordingly, in the illumination device 20A, the second semiconductor laser 212 that emits laser light having a peak wavelength of 446 nm is used as the laser light source for excitation light, and the laser light having a peak wavelength of 460 nm is emitted to the laser light source for blue light. By using the first semiconductor laser 211, it is possible to improve the color gamut at a lower cost.

  As described above, according to the projector 1 including such an illumination device 20A, it is possible to perform display with excellent image quality while reducing the size and weight of the device.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS.

  The projector 1b according to this embodiment includes a lighting device 2b. The basic configuration of the projector 1b is the same as that of the projector 1 of the first embodiment, but the configuration of the illumination device 2b is different from the configuration of the illumination device 2 of the projector 1. Constituent elements common to the projector 1 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

(projector)
FIG. 5 is a plan view showing a schematic configuration of the projector 1b according to the present embodiment.
As shown in FIG. 5, the projector 1b includes an illumination device 2b, a color separation optical system 3, a light modulation device 4R, a light modulation device 4G and a light modulation device 4B, a synthesis optical system 5, and a projection optical system 6. It is equipped with.

(Lighting device)
Next, the illuminating device 2b which concerns on this embodiment is demonstrated.
FIG. 6 is a schematic configuration diagram illustrating the illumination device according to the second embodiment.
As shown in FIG. 6, the illumination device 2b includes an array light source 21B, a collimator optical system 22, an afocal optical system 23, a phase difference plate 28a, a homogenizer optical system 24, a polarization separation element 50A, 1 pickup optical system 26, fluorescent light emitting element 27, phase difference element 28b, second pickup optical system 29, diffuse reflection element 30e, and uniform illumination optical system 40 are included. The array light source 21B, the collimator optical system 22, the afocal optical system 23, the phase difference plate 28a, and the homogenizer optical system 24 constitute a light source device 25. The light source device 25 emits third light including a P-polarized component for the polarization separation element 50A and an S-polarization component for the polarization separation element 50A. The P-polarized component contained in the third light corresponds to the first component in the first polarization state in the claims. The S polarization component included in the third light corresponds to the second component in the second polarization state in the claims. In the present embodiment, the third light is elliptically polarized light or circularly polarized light, but the third light may be light in which P-polarized light and S-polarized light are mixed.

  The light source device 25, the polarization separation element 50A, the phase difference element 28b, the second pickup optical system 29, and the diffuse reflection element 30e are disposed on the optical axis ax1. On the other hand, the fluorescent light emitting element 27, the first pickup optical system 26, the polarization separation element 50A, and the uniform illumination optical system 40 are disposed on the optical axis ax2. The optical axis ax1 and the optical axis ax2 are in the same plane and are orthogonal to each other.

  The array light source 21B includes a plurality of semiconductor lasers 211. The semiconductor laser 211 emits a light beam BL ′ made of linearly polarized blue light. As will be described later, a part of the light beam BL 'is separated by the polarization separation element 50A to become excitation light of the phosphor layer. The other part of the light beam BL 'is separated by the polarization separation element 50A, and becomes blue light for image display through the diffuse reflection element.

  The light beam BL ′ emitted from the array light source 21 </ b> B enters the collimator optical system 22. The light beam BL ′ that has passed through the collimator optical system 22 enters the afocal optical system 23.

  The light beam BL 'that has passed through the afocal optical system 23 passes through the phase difference plate 28a and is converted into circularly polarized light. The light beam BL ′ that has passed through the phase difference plate 28 a is incident on the homogenizer optical system 24.

The light beam BL ′ emitted from the light source device 25 enters the polarization separation element 50A. The polarization separation element 50A separates the circularly polarized light beam BL ′ into an S-polarized component light beam BM _Se and a P-polarized component light beam BMp for the polarization separation element 50A. The light beam BM _Se of the S polarization component is reflected by the polarization separation element 50A, travels toward the fluorescent light emitting element 27, and is used as excitation light. The P-polarized component light beam BMp passes through the polarization separation element 50A and travels toward the diffuse reflection element 30e. Further, the polarization separation element 50A has a wavelength selectivity that transmits the fluorescent light YL having a wavelength band different from that of the blue light regardless of the polarization state.

The light beam BM _Se reflected by the polarization beam splitting element 50A enters the first pickup optical system 26.

The phosphor layer 34 includes a phosphor that is excited by, for example, excitation light (light beam BM _Se ) having a wavelength of 460 nm. The phosphor generates fluorescent light (yellow light) YL having a peak wavelength in a wavelength range of 500 to 700 nm, for example. The S-polarized light beam BM _Se that is the second component reflected by the polarization separation element 50A is incident on the phosphor layer 34.

  The fluorescent light YL emitted from the phosphor layer 34 is non-polarized light whose polarization direction is not uniform. The fluorescent light YL enters the polarization separation element 50 after passing through the first pickup optical system 26. Since the polarization separation element 50 has a characteristic of transmitting the fluorescence light YL regardless of the polarization state, the fluorescence light YL passes through the polarization separation element 50 and proceeds toward the integrator optical system 31.

On the other hand, the light beam BM _P of P polarized light passed through the polarization separation element 50A is incident on the phase difference element 28b. The phase difference element 28b is composed of a quarter-wave plate disposed in the optical path between the polarization separation element 50A and the diffuse reflection element 30e. Therefore, the light beam BM _P of P-polarized light emitted from the polarization separation element 50A is converted into a light beam BM _C circularly polarized light by the phase difference element 28b. In the present embodiment, the light beam BM _C is right circularly polarized light. Thereafter, the light beam BM _C is incident on the second pick-up optical system 29.

The second pickup optical system 29, a light beam BM _C toward the diffuse reflection element 30e is condensed.

Diffuse reflective element 30e diffuses reflects the light beam BM _C emitted from the second pick-up optical system 29 to the polarization separation element 50A. Similar to the diffuse reflection element 30 in the first embodiment, the diffuse reflection element 30 e has a concavo-convex structure 143 including a plurality of curved surfaces. The first component whose polarization state has been changed by passing through the phase difference element 28b is incident on the diffuse reflection element 30e.

The following describes the case where the light beam BM _C incident on the diffuse reflection element 30e is converted into light beam BM C _'of the left circularly polarized light.
The light beam BM _C ′ is again incident on the phase difference element 28b, thereby being converted into an S-polarized light beam BM _Sd . Thereafter, the light beam BM _Sd enters the polarization separation element 50A. In the present embodiment, since the light beam BM _C ′ is left circularly polarized light, the light beam BM _Sd corresponds to the fourth component of the second polarization state in the claims. In other words, the first component reflected by the diffuse reflection element 30e and transmitted through the phase difference element 28b does not include the component of the first polarization state. However, depending on the shape of the concavo-convex structure 143 it may not be reflected in the light beam BM _C incident on the diffuse reflection element 30e is a full left-circularly polarized light. In this case, the first component reflected by the diffuse reflection element 30e and transmitted through the phase difference element 28b includes some components of the first polarization state.

The S-polarized light beam BM _Sd is reflected by the polarization separation element 50 </ b> A and travels toward the integrator optical system 31. In this way, white illumination light WL obtained by combining the light beam BM _Sd that is blue light and the fluorescent light YL that is yellow light is obtained.

Incidentally, in order to increase the utilization efficiency of the light emitted from the array light source 21B, it is preferable that the light beam BM _Sd is incident on the polarization separation element 50A as linearly polarized light that is S-polarized light. When the light beam BMc ′ is elliptically polarized light, the light beam BMc ′ remains elliptically polarized light even if it passes through the phase difference element 28b. Since the light beam BM _Sd incident on the polarization separation element 50A is elliptically polarized light, it includes a P-polarized component that is not reflected by the polarization separation element 50A. Therefore, the light amount of the light beam BM _Sd reflected by the polarization separation element 50A is reduced. When the light beam BMc ′ is left circularly polarized light, the light beam BMc ′ is converted into linearly polarized light that is S-polarized light by the phase difference element 28b, so that the light amount of the light beam BMsd reflected by the polarization separation element 50A becomes maximum. .

Here, it is assumed that light enters the diffuse reflection element 30e perpendicularly. In order for the diffuse reflection element 30e to convert the right circularly polarized light beam BMc into the left circularly polarized light beam BMc ′, the diffuse reflection element 30e reflects the incident linearly polarized light while maintaining its polarization state. Must have. When the polarization state is not maintained, the light beam BMc ′ becomes elliptically polarized light. Accordingly, the higher the proportion of the linearly polarized light that is maintained by the diffuse reflection element 30e, the greater the amount of light beam BM _Sd reflected by the polarization separation element 50A. As a result, more components are used as the illumination light WL, and the light use efficiency can be increased.

As a specific means for maintaining the polarization state, the aspect ratio of the concavo-convex structure of the diffuse reflection element 30e may be adjusted within an appropriate range.
FIG. 7 is a cross-sectional view showing the diffuse reflection element 30e of this embodiment.
As shown in FIG. 7, the diffuse reflection element 30 e includes a base material 141 and a reflective film 142 provided on one surface 141 a of the base material 141. On one surface of the base material 141, a concavo-convex structure 143 in which concave portions 143a and convex portions 143b are alternately provided is formed. The reflective film 142 is made of a metal material having a high reflectance such as silver or aluminum. Although the material of the base material 141 is not specifically limited, It is preferable that it is a material with high heat resistance. The reflective film 142 is formed with a predetermined film thickness that reflects the shape of the concavo-convex structure 143 of the substrate 141. In addition, the base material 141 may be comprised with the material which has light reflectivity, and the reflective film does not need to be provided separately in that case.

  A distance between two adjacent convex portions 143b (or a distance between two adjacent concave portions 143a) is defined as a pitch P, and a distance from the lowermost portion of the concave portion 143a to the uppermost portion of the convex portion 143b is defined as the depth D of the concave portion 143a. The aspect ratio of the concavo-convex structure 143 is defined as D / P.

  Here, the inventors examined the relationship between the aspect ratio of the concavo-convex structure 143 and the light utilization efficiency. Specifically, diffuse reflection elements 30e having different aspect ratios of the concavo-convex structure 143 were actually created, and the amount of light emitted through the polarization separation element 50A was measured. The amount of light obtained when the diffuse reflection element 30e was replaced with a specular reflection element having a flat reflection surface was used as the reference light amount. And the ratio of the light quantity obtained using the diffuse reflection element 30e and the reference light quantity was calculated. In the specular reflection element, the incident light is specularly reflected only once by the reflection element, so that the polarization state of the vertically polarized linearly polarized light is maintained at 100%. Therefore, when the diffuse reflection element is replaced with a specular reflection element, the light utilization efficiency is maximized.

FIG. 8 is a graph showing the relationship between the aspect ratio and the light amount ratio of the diffuse reflection element.
The horizontal axis in FIG. 8 is the aspect ratio, and the vertical axis in FIG. 8 is the light amount ratio (%). Two graphs A and B show two types of experimental results in which the configuration of the optical system on the optical path of the light incident on the diffuse reflector is changed and the intensity distribution of the light incident on the diffuse reflector is different. Yes.
Note that an aspect ratio of zero corresponds to the use of a specular reflection element. Therefore, when the aspect ratio is zero, the polarization state of the linearly polarized light that is incident vertically is maintained at 100%, so that the light amount ratio is 100%.

  As shown in FIG. 8, as a tendency common to the two types of optical systems, a region having a light amount ratio of 75% or more (a region having an aspect ratio of 0.35 or less in the optical system A, and an aspect ratio of 0.1 in the optical system B). In the region of 25 or less), the light amount ratio tends to gradually decrease as the aspect ratio increases. On the other hand, in the area where the light quantity ratio is less than 75% (the area where the aspect ratio is larger than 0.35 in the optical system A and the area where the aspect ratio is larger than 0.25 in the optical system B), the aspect ratio increases. Along with this, the light quantity ratio tends to decrease rapidly. This is because the concave portion is shallow in a region where the aspect ratio is relatively small, so that the number of times incident light is reflected in the concave portion is small, and the ratio of maintaining the polarization state is large. On the other hand, in the region where the aspect ratio is relatively large, the concave portion is deep, and therefore the ratio of incident light that is multiply reflected within the concave portion increases, and the proportion of light that maintains the polarization state decreases. The Thus, it is preferable that multiple reflections do not occur.

  From the above experimental results, it was proved that the light utilization efficiency can be increased to some extent by setting the aspect ratio of the concavo-convex structure so that the above-mentioned light quantity ratio shows a value of 75% or more. However, as shown in FIG. 8, the range of the aspect ratio for showing a light amount ratio of 75% or more differs depending on the optical system used.

  As described above, from the viewpoint of improving the light utilization efficiency, it is preferable that the aspect ratio of the concavo-convex structure is as small as possible. However, if the aspect ratio of the concavo-convex structure is too small, another problem arises.

  The diffusion angle distribution of the diffused light has a correlation with the aspect ratio of the concavo-convex structure. When the aspect ratio of the concavo-convex structure is small, the diffusion angle distribution becomes small accordingly. In general, the light distribution is different between the fluorescence emitted from the phosphor layer and the diffused light emitted from the diffusion layer. Specifically, the diffusion angle distribution of diffused light is smaller than the diffusion angle distribution of fluorescence. Therefore, in the illumination device of the present embodiment, if the aspect ratio of the concavo-convex structure is too small, the diffusion angle distribution of blue light becomes too small, and the difference from the diffusion angle distribution of yellow light emitted from the fluorescent light emitting element is large. There is a problem that uneven color occurs.

Therefore, the present inventors examined the relationship between the aspect ratio of the concavo-convex structure and the color unevenness.
Specifically, diffuse reflection elements with various aspect ratios of the concavo-convex structure are actually created and incorporated in the projector of this embodiment, and the light emitted from the illumination device is projected onto the screen, resulting in uneven color of the projected image. Was measured. As a method for measuring color unevenness, a zoom lens is set to a wide range, and a deviation value (Δu′v ′) from a black body locus is measured at 13 measurement points on a screen (illuminated area) using a color illuminance meter. did. The larger the deviation value Δu′v ′ from the black body locus, the greater the color unevenness.

  FIG. 9 is a graph showing the relationship between the aspect ratio of the diffuse reflection element and the relative color unevenness ratio. The horizontal axis is the aspect ratio, and the vertical axis is the color unevenness relative ratio (%). Here, the deviation value Δu′v ′ when the diffuse reflection element 30 e is replaced with a specular reflection element is defined as reference color unevenness. The color unevenness relative ratio is a ratio of the deviation value (color unevenness) Δu′v ′ when the diffuse reflection element having a predetermined aspect ratio is used to the reference color unevenness. Color unevenness is less likely to be recognized when the color unevenness relative ratio is smaller.

  As shown in FIG. 9, in an area where the color unevenness relative ratio exceeds 50%, in other words, in an area where the aspect ratio is less than 0.002, the color unevenness relative ratio increases from 100% as the aspect ratio increases. It shows a tendency to decrease rapidly. On the other hand, in the area where the color unevenness relative ratio is 50% or less, in other words, in the area where the aspect ratio is 0.002 or more, even if the aspect ratio is increased, the color unevenness relative ratio does not change greatly. , Tend to be substantially constant at a value of about 50%.

In addition, the present inventors actually performed a visual evaluation of the projected image on the screen and performed a sensitivity evaluation of color unevenness. The results are shown in [Table 1] below.
In [Table 1], two types of experimental results in which the intensity distribution of incident light is made different by changing the configuration of the optical system (optical system A and optical system B) on the optical path of the light incident on the diffuse reflection element. Is shown. Note that “◯” in Table 1 indicates that color unevenness is not visually recognized. “Δ” indicates that although the color unevenness is visually recognized, the color unevenness is so slight as not to be noticed. “X” indicates that color unevenness is a concern.

  As is apparent from [Table 1], it was found that when the relative ratio of color unevenness was 50%, the color unevenness was not visually recognized. When the color unevenness relative ratio was 90%, it was found that although the color unevenness was visually recognized depending on the optical system, the level was not particularly problematic for image display. On the other hand, it was found that when the relative ratio of color unevenness was 100%, the color unevenness was a concern and the image display was hindered.

  From the results of FIG. 9 and Table 1, it was found that the color unevenness can be reduced to a level where there is no practical problem by setting the aspect ratio of the concavo-convex structure so that the color unevenness relative ratio shows a value of 90% or less. . Furthermore, it was found that the color unevenness is reduced to the maximum level by setting the aspect ratio of the concavo-convex structure so that the color unevenness relative ratio shows a value of 50% or less. The aspect ratio at which the color unevenness relative ratio was 90% was 0.0075, and the aspect ratio at which the color unevenness relative ratio was 50% was 0.0027.

  As described above, in order to suppress the uneven color distribution by balancing the diffusion angle distribution of the diffused light and the fluorescent light while improving the light utilization efficiency of the blue light obtained from the diffuse reflection element, the polarization separation element is used. The diffuse light reflecting element so that the ratio of the amount of light emitted through the light source and the reference light amount is 75% or more, and the color unevenness relative ratio is 90% or less, more preferably 50% or less. The aspect ratio of the concavo-convex structure may be controlled.

  By the way, in order to control the light quantity ratio and the color unevenness relative ratio within a predetermined range, it is preferable that the uneven structure of the diffuse reflection element is regular. That is, it is preferable that the pitch P of the concavo-convex structure or the depth D of the concave portion is designed to be constant. However, even if the pitch P of the concavo-convex structure of the diffuse reflection element and the depth D of the concave part of the diffuse reflection element that are actually completed vary due to factors in the manufacturing process of the diffuse reflection element, the diffuser reflection element can be used without any problem in the illumination device of this embodiment. it can. Or you may design so that the pitch P of a concavo-convex structure or the depth D of a recessed part may become random.

  The present inventors produced diffuse reflection elements having a regular uneven structure and diffuse reflection elements having a random uneven structure, and evaluated light utilization efficiency and color unevenness. Specifically, a diffuse reflection element having a constant aspect ratio of 0.05 and a diffuse reflection element having an aspect ratio randomly varied around 0.05 were used.

  The light utilization efficiency (light quantity ratio in FIG. 8) was 96% in all cases.

  FIG. 10 shows the result of measuring the deviation value (Δu′v ′) with the projector zoom lens set to the wide setting or the tele setting.

  As shown in FIG. 10, the difference of the deviation value Δu′v ′ depending on the presence or absence of the randomness of the concavo-convex structure was about 0.001 in both the wide setting and the tele setting. The difference of the deviation value Δu′v ′ of about 0.001 is a level that can be ignored for visually observed color unevenness.

  From the above, it was confirmed that the pitch P of the concavo-convex structure of the diffuse reflection element and the depth D of the concave portion may be constant or random. The aspect ratio in the case where the pitch P and the depth D of the recesses are random can be considered as an average value of the pitch P and the depth D of the recesses at a plurality of locations. What is necessary is just to determine suitably the parameter of a recessed part or a convex part at the time of calculating an average value.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
The basic configuration of the illumination device of the present embodiment is the same as that of the illumination device of the second embodiment, but the positional relationship between the diffuse reflection element and the fluorescent light emitting element is different from that of the second embodiment.
FIG. 11 is a schematic configuration diagram of a lighting apparatus according to the third embodiment.
In FIG. 11, the same code | symbol is attached | subjected to the same component as the illuminating device 2b in 2nd Embodiment, and description is abbreviate | omitted.

  The polarization separation element of this embodiment is different from the polarization separation element of the second embodiment in that it has a characteristic of reflecting fluorescent light having a wavelength band different from that of blue light regardless of its polarization state. With such a difference in the characteristics of the polarization separation element, in the illumination device of this embodiment, the positional relationship between the diffuse reflection element and the fluorescent light emitting element is replaced with that in the second embodiment.

  As shown in FIG. 11, in the illumination device 52 of the present embodiment, the light source device 25, the polarization separation element 53, the first pickup optical system 26, and the fluorescent light emitting element 27 are arranged on the optical axis ax1. Has been.

  The diffuse reflection element 30e, the second pickup optical system 29, the phase difference plate 28b, the polarization separation element 53, the integrator optical system 31, the polarization conversion element 32, and the superposition optical system 33 are on the optical axis ax2. Is arranged. Also in this embodiment, the diffuse reflection element 30e has an uneven structure, and the aspect ratio of the uneven structure is set in the same manner as in the second embodiment.

The projector of this embodiment, the light beam BM _S of S-polarized light is reflected by the polarization beam splitter 53 and travels toward the retardation element 28b. The light beam BM _S emitted from the polarization separating element 53 is converted into light beam BM _C of right-handed circularly polarized light by the phase difference element 28b. Thereafter, the light beam BM _C is incident on the diffuse reflection element 30e via the second pickup system 29. Diffuse reflective element 30e is a light beam BM _C which enters into a BM C _'of the left circularly polarized light is diffused reflected toward the polarization separation element 53. Also in the present embodiment, the case where the light beam BM _C ′ emitted from the diffuse reflection element 30e is left circularly polarized light will be described.

The light beam BM _C ′ diffusely reflected by the diffuse reflection element 30e is incident on the phase difference element 28b again, thereby being converted into a P-polarized light beam BM _Pd . Thereafter, the P-polarized light beam BM _Pd passes through the polarization separation element 53 and proceeds toward the integrator optical system 31. On the other hand, the P-polarized component light beam BMp passes through the polarization separation element 53 and travels toward the fluorescent light emitting element 27 as excitation light.

  Also in the present embodiment, the same effect as that of the first embodiment can be obtained in that the color unevenness can be suppressed while improving the light use efficiency of the blue light obtained from the diffuse reflection element 30e.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the diffusive reflector used in the above embodiment, the concavo-convex structure is configured by a plurality of concave portions having a curved surface, but may be configured by a plurality of convex portions having a curved surface. That is, you may use the diffuse reflection board which the uneven | corrugated shape reversed with respect to the diffuse reflection board shown in FIG. Moreover, the concavo-convex structure may be composed of a plurality of concave portions made of a curved surface and a plurality of convex portions made of a curved surface.

  In the first embodiment, the first wavelength band is different from the second wavelength band. However, the first wavelength band may coincide with the second wavelength band.

  In the illuminating device of each embodiment, a quarter-wave plate is used as a phase difference element provided between the polarization separation element and the diffuse reflection element, but the phase difference of the phase difference element is not necessarily limited to a quarter wavelength. It is not necessary to make any changes. In addition, the shape, number, arrangement, material, and the like of various components of the illumination device and the projector are not limited to the above-described embodiment, and can be changed as appropriate.

  In each embodiment, the diffuse reflection element may be fixed, or may be configured to be rotatable as in the first embodiment.

  In each embodiment, although the example which mounted the light source device by this invention in the projector using a liquid crystal light valve was shown, it is not restricted to this. You may mount in the projector using a digital micromirror device as a light modulation apparatus.

  In each embodiment, although the example which mounted the light source device by this invention in the projector was shown, it is not restricted to this. The light source device according to the present invention can also be applied to lighting fixtures, automobile headlights, and the like.

  DESCRIPTION OF SYMBOLS 1,1b ... Projector, 2, 2b, 20A, 52 ... Illumination device, 4R, 4G, 4B ... Light modulation device, 6 ... Projection optical system, 21A ... Array light source (light source device), 21B ... Array light source, 25 ... Light source Device, 28, 28b ... Phase difference element, 30, 30e ... Diffuse reflection element, 34 ... Phosphor layer, 37 ... Reflection part, 43a, 45a, 46a, 143 ... Uneven structure, 44, 47 ... Reflection film, 50A, 53 ... polarization separation element, 211 ... first semiconductor laser (first light source), 212 ... second semiconductor laser (second light source).

Claims (9)

An illumination device that emits illumination light;
A light modulation device that forms image light by modulating the illumination light according to image information;
A projection optical system for projecting the image light,
The lighting device includes:
A light source device for emitting laser light;
A first phase difference element on which the laser beam is incident;
The laser light emitted from the first phase difference element is divided into a first component having a first polarization state and a second component having a second polarization state different from the first polarization state. A polarized light separating element to separate;
A second phase difference element that is incident on the first component via the polarization separation element and changes a polarization state of the first component;
A diffusive reflecting element having a concavo-convex structure including a plurality of curved surfaces, and diffusively reflecting the first component transmitted through the second phase difference element;
A phosphor layer that is incident on the second component via the polarization separation element and is excited by the second component to emit light in a wavelength band different from the wavelength band of the laser light; and
The first component reflected by the diffuse reflection element is incident on the second phase difference element and converted into a light beam having the second polarization state,
The projector, wherein the light emitted from the phosphor layer and the light beam are emitted as the illumination light via the polarization separation element.   The projector according to claim 1, wherein the plurality of curved surfaces are randomly arranged in a plan view. The diffuse reflection element includes a base material made of metal,
The projector according to claim 1, wherein the concavo-convex structure is provided on a surface of the base material on a side on which the first component is incident. The diffuse reflection element includes a base material made of glass,
The concavo-convex structure is provided on the surface of the base on which the first component is incident,
The projector according to claim 1, wherein a metal reflective film is provided on a surface of the concavo-convex structure along the shape of the concavo-convex structure. In the uneven structure, the amount of the light beam having the second polarization state in which the first component reflected by the diffuse reflection element enters the second phase difference element and is converted is diffused and reflected. The projector according to claim 1, wherein the projector is configured to be 75% or more of the light amount obtained when the element is replaced with a reflection element having a flat reflection surface. In the lighting device,
The polarization separation element transmits light in a wavelength band different from the wavelength band of the laser light regardless of the polarization state,
6. The phosphor layer according to claim 1, further comprising a reflecting portion that is provided on a side opposite to a surface on which the second component of the phosphor layer is incident and reflects light emitted from the phosphor layer. The projector according to any one of the above. In the lighting device,
The polarization separation element reflects light in a wavelength band different from the wavelength band of the laser light regardless of the polarization state,
6. The phosphor layer according to claim 1, further comprising a reflecting portion that is provided on a side opposite to a surface on which the second component of the phosphor layer is incident and reflects light emitted from the phosphor layer. The projector according to any one of the above.   The projector according to claim 1, wherein an aspect ratio of the concavo-convex structure is 0.002 or more.   9. The diffuse reflection element can be rotated in a plane intersecting a central axis of the first component incident on the diffuse reflection element. Projector.