JP2008107521A - Light source device, illuminating device and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device capable of reducing speckle and supplying high-quality coherent light. <P>SOLUTION: The light source device is equipped with: a light source part 11 supplying light which is the coherent light and which includes a first polarized light component having a first vibration direction; a polarizing beam splitter 12 which is a polarized light separation part transmitting the light of the first polarized light component and reflecting the light of a second polarized light component having a second vibrating direction nearly orthogonal to the first vibrating direction, thereby separating the first polarized light component and the second polarized light component; and a first mirror 13, a second mirror 14 and a third mirror 15 which are reflection parts provided in the optical path of light from the polarized light separation part and reflecting the light from the polarized light separation part, thereby making it incident on the polarized light separation part. The reflection parts make an optical path difference between the light transmitted through the polarized light separation part out of the light made incident on the polarized light separation part from the reflection parts and the light transmitted through the polarized light separation part out of the light reflected by the polarized light separation part and further made incident on the polarized light separation part through the reflection parts. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source device, an illumination device, and an image display device, and more particularly to a technology of a light source device used for an image display device.

  When a laser beam, which is coherent light, is irradiated onto a diffusion surface, an interference pattern called a speckle pattern in which bright spots and dark spots are randomly distributed may appear. The speckle pattern is generated when light diffused at each point on the diffusion surface interferes randomly. When a speckle pattern is recognized when an image is displayed, a glimmering flickering feeling is given to the observer, which adversely affects image viewing. In addition, a liquid crystal display device used for an image display device performs modulation by converting a polarization state of incident light. When a liquid crystal display device is used, the light from the light source unit can be efficiently used by converting the light from the light source unit into linearly polarized light having a specific vibration direction and supplying the converted light. In order to reduce speckles and efficiently supply linearly polarized light in a specific vibration direction, for example, Patent Document 1 proposes a technique using a combination of an optical fiber and a polarizing beam splitter.

JP 2000-89160 A

  According to the technique of Patent Document 1, the light that has entered the optical fiber via the polarizing beam splitter propagates through the optical fiber and then enters the polarizing beam splitter again. By propagating light while repeating reflection in the optical fiber, it is possible to emit light having different optical path lengths. Speckle can be reduced by emitting light having different optical path lengths. Further, by making the light from the optical fiber enter the polarization beam splitter, it becomes possible to supply linearly polarized light in a specific vibration direction. If the reflection of the laser beam is repeated in the optical fiber, the wavefront of the laser beam will be messy. When the light is incident on the optical fiber, the laser light condensed at substantially one point is spread over the entire cross section of the optical fiber by propagating through the optical fiber. When light is emitted from a surface having a certain area, the parallelism when the light is collimated by an illumination optical system or the like is lower than when light is emitted from substantially one point. As the parallelism of light decreases, it becomes difficult to efficiently supply illumination light to the illumination target. In particular, speckle can be effectively reduced as the number of times light is propagated in the optical fiber, while the quality of laser light is significantly deteriorated. The present invention has been made in view of the above-described problems, and an object thereof is to provide a light source device, an illumination device, and an image display device that can reduce speckles and supply high-quality coherent light. To do.

  In order to solve the above-described problems and achieve the object, according to the present invention, a light source unit that supplies coherent light including light having a first polarization component having a first vibration direction, and first polarization Polarization separation that separates the first polarization component and the second polarization component by transmitting the component light and reflecting the light of the second polarization component having the second vibration direction substantially orthogonal to the first vibration direction And a reflection unit that is provided in the optical path of the light from the polarization separation unit and is incident on the polarization separation unit by reflecting the light from the polarization separation unit, and the reflection unit separates the polarization from the reflection unit. The light path difference between the light that has passed through the polarization splitting unit and the light that has been reflected by the polarization splitting unit and has entered the polarization splitting unit through the reflecting unit is transmitted through the polarization splitting unit. It is possible to provide a light source device that is characterized by being generated.

  The light of the first polarization component incident on the polarization separation unit from the reflection unit is transmitted through the polarization separation unit. The light of the second polarization component that has entered the polarization separation unit from the reflection unit is reflected by the polarization separation unit and travels in the direction of the reflection unit. And the light of the 1st polarization component among the light which entered the polarization separation part again from the reflection part permeate | transmits a polarization separation part. The light of the second polarization component reflected by the polarization separation unit further repeats the above circulation. Speckle can be reduced by emitting light having different optical path lengths. By using the polarization separation unit, it is possible to emit light of the first polarization component that is linearly polarized light in a specific vibration direction. By using the reflection unit provided in the optical path of the light from the polarization separation unit, the disturbance of the wavefront can be reduced, and high-quality coherent light can be supplied. Thereby, a speckle can be reduced and the light source device for supplying high quality coherent light can be obtained.

  Further, as a preferred aspect of the present invention, the reflection part reflects at the polarization separation part, and further passes through the reflection part and enters the polarization separation part, so that the optical path length is equal to or longer than the coherent length of the coherent light. It is desirable to be arranged as follows. With this configuration, there is an optical path difference equivalent to or greater than the coherent length between the light transmitted through the polarization separation unit and the light reflected by the polarization separation unit, further passing through the reflection unit, and then transmitted through the polarization separation unit. Cause it to occur. Thereby, speckle can be reduced effectively.

  Further, as a preferred aspect of the present invention, the reflection unit includes an optical path of light that has been transmitted from the reflection unit to the polarization separation unit and transmitted through the polarization separation unit, and is reflected by the polarization separation unit and further separated through the reflection unit. It is desirable that the light path of the light incident on the part and transmitted through the polarization separation part is substantially matched. As a result, high-quality coherent light with little spread of light can be supplied. Since the spread of light can be reduced, the reflecting part and the polarization separating part can be made small.

  Moreover, as a preferable aspect of the present invention, the reflection unit includes a first reflection unit that reflects light from the polarization separation unit, a second reflection unit that reflects light from the first reflection unit, and a second reflection unit. It is desirable to have the 3rd reflection part which reflects the light of. Thereby, it can be made to inject into a polarization separation part by reflecting the light from a polarization separation part. In addition, by adjusting the positions and inclinations of the first reflection unit, the second reflection unit, the third reflection unit, and the polarization separation unit, the optical paths of the light transmitted through the polarization separation unit can be made substantially coincident.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a polarizing element that is provided in the optical path of the light from the polarization separation unit and changes the polarization state of the light from the polarization separation unit. The polarization separation unit emits linearly polarized light. By appropriately changing the polarization state of the light by the polarizing element, it becomes possible to circulate a lot of light from the polarization separation unit to the reflection unit. The more light that is circulated from the polarization separation unit to the reflection unit, the more light that has passed through different optical path differences can be emitted. Thereby, speckle can be reduced effectively.

  Moreover, as a preferable aspect of the present invention, it is desirable that the polarizing element includes a wave plate. By applying a phase difference using a wave plate, the polarization state of light can be changed.

  Moreover, as a preferable aspect of the present invention, it is desirable that the reflecting portion includes a mirror. Thereby, the light from the polarization separation unit can be reflected with a simple configuration.

  Moreover, as a preferable aspect of the present invention, it is desirable that the reflecting portion includes a prism. Thereby, the light from a polarization separation part can be reflected. Further, when total reflection of the prism is used, light loss can be reduced.

  Moreover, as a preferable aspect of the present invention, it is desirable to have an optical element that transmits light from the light source unit, and the polarization separation unit and the reflection unit are preferably formed in the optical element. Thereby, it is possible to reduce the loss of light due to passing through the polarization separation unit and the reflection unit. Further, since the precise position adjustment of the polarization separation unit and the reflection unit can be eliminated in exchange for the formation of the optical element, the light source device can be easily manufactured.

  Moreover, as a preferable aspect of the present invention, it is desirable to have a low refractive index layer having a refractive index smaller than that of the optical element. The low refractive index layer guides light in a desired direction by totally reflecting light traveling between the reflecting portions or between the reflecting portion and the polarization separating portion. Thereby, it is possible to reduce the loss of light due to passing through the polarization separation unit and the reflection unit.

  Furthermore, according to the present invention, it is possible to provide an illuminating device including the light source device described above and a uniformizing optical system that makes the intensity distribution of the light flux from the light source device uniform. By providing the light source device described above, speckle can be reduced and high-quality coherent light can be supplied. Thereby, the speckle can be reduced and the illuminating device for supplying high quality coherent light can be obtained.

  Furthermore, according to the present invention, it is possible to provide an image display device that displays an image using light from the light source device. By providing the light source device described above, speckle can be reduced and high-quality coherent light can be supplied. Thereby, an image display apparatus capable of displaying a high-quality and bright image by reducing speckles can be obtained.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 shows a schematic configuration of a light source device 10 according to Embodiment 1 of the present invention. The light source device 10 includes a light source unit 11. The light source unit 11 supplies laser light that is coherent light. The laser beam supplied from the light source unit 11 is, for example, p-polarized light. The p-polarized light is light of the first polarization component having the first vibration direction. As the light source unit 11, a semiconductor laser, a semiconductor laser pumped solid state (DPSS) laser, a solid laser, a liquid laser, a gas laser, or the like can be used. The light source unit 11 may use a wavelength conversion element that converts the wavelength of the laser light, for example, a second-harmonic generation (SHG) element.

  The polarization beam splitter 12 is provided at a position where the laser light from the light source unit 11 enters. The polarization beam splitter 12 is a polarization separation unit that separates the p-polarized component and the s-polarized component by transmitting the p-polarized light and reflecting the s-polarized light. The s-polarized light is light of a second polarization component having a second vibration direction that is substantially orthogonal to the first vibration direction. The polarization beam splitter 12 is configured, for example, by coating a parallel flat plate such as glass with a dielectric multilayer film. The polarization beam splitter 12 is disposed so as to be inclined at an angle of approximately 45 degrees with respect to both the incident light from the light source unit 11 and the incident light from the third mirror 15. The polarization beam splitter 12 may use a wire grid instead of the dielectric multilayer film.

  The first mirror 13, the second mirror 14, and the third mirror 15 are provided in the optical path of the light from the polarization beam splitter 12. The first mirror 13, the second mirror 14, and the third mirror 15 are reflecting portions that enter the polarizing beam splitter 12 by reflecting light from the polarizing beam splitter 12. The first mirror 13 is provided at a position where the laser light from the light source unit 11 transmitted through the polarization beam splitter 12 enters. The first mirror 13 is a mirror that reflects the light from the polarization beam splitter 12 and is a first reflection unit.

  The second mirror 14 is provided at a position where the light reflected by the first mirror 13 enters. The second mirror 14 is a mirror that reflects the light from the first mirror 13 and is a second reflecting portion. The third mirror 15 is provided at a position where the light reflected by the second mirror 14 enters. The third mirror 15 is a mirror that reflects the light from the second mirror 14 in the direction of the polarization beam splitter 12, and is a third reflection unit. The first mirror 13, the second mirror 14, and the third mirror 15 bend incident light by 90 degrees by reflection.

  The first mirror 13, the second mirror 14, and the third mirror 15 are configured by coating parallel flat plates with a highly reflective member, such as a metal film or a dielectric multilayer film. By using the mirrors 13, 14, and 15, the light from the polarization beam splitter 12 can be reflected with a simple configuration. Each of the first mirror 13, the second mirror 14, and the third mirror 15 has a reflection characteristic that has a high reflectance with respect to the wavelength of the laser light from the light source unit 11, for example, a reflectance close to 100%. It is desirable to do. Thereby, the loss of light due to the reflection at the first mirror 13, the second mirror 14, and the third mirror 15 can be reduced. The polarization beam splitter 12, the first mirror 13, the third mirror 15 and the second mirror 14 are all arranged at the same interval d1. The polarization beam splitter 12, the third mirror 15, the first mirror 13, and the second mirror 14 are all arranged at the same interval d2. The magnitude relationship between the intervals d1 and d2 is arbitrary.

  Since the light L1 from the light source unit 11 is p-polarized light, it passes through the polarization beam splitter 12. The light L1 transmitted through the polarizing beam splitter 12 is sequentially reflected by the first mirror 13, the second mirror 14, and the third mirror 15, and then enters the polarizing beam splitter 12. The light L <b> 1 changes from p-polarized light, which is linearly polarized light, to elliptically-polarized light due to reflection by the first mirror 13, the second mirror 14, and the third mirror 15. Of the light incident on the polarizing beam splitter 12 from the third mirror 15, the p-polarized light L <b> 3 passes through the polarizing beam splitter 12 and is emitted from the light source device 10.

  Of the light incident on the polarization beam splitter 12 from the third mirror 15, the s-polarized light is reflected by the polarization beam splitter 12, and the optical path is bent by approximately 90 degrees. When the optical path is bent by approximately 90 degrees, the light L2 reflected by the polarization beam splitter 12 travels in the direction of the first mirror 13. The light L <b> 2 is sequentially reflected by the first mirror 13, the second mirror 14, and the third mirror 15, and then enters the polarization beam splitter 12 again. Of the light incident on the polarizing beam splitter 12 from the third mirror 15, the p-polarized light L <b> 4 passes through the polarizing beam splitter 12 and is emitted from the light source device 10. Of the light incident on the polarizing beam splitter 12, s-polarized light is reflected by the polarizing beam splitter 12, and the above-described circulation is repeated.

  The light L2 that is reflected by the polarizing beam splitter 12 and then enters the polarizing beam splitter 12 via the first mirror 13, the second mirror 14, and the third mirror 15 passes through an optical path having a length of 2 × (d1 + d2). Become. The coherent length of the laser light from the light source unit 11 is substantially the same as 2 × (d1 + d2). The first mirror 13, the second mirror 14, and the third mirror 15 are optical paths that are reflected by the polarization beam splitter 12 and then enter the polarization beam splitter 12 through the first mirror 13, the second mirror 14, and the third mirror 15. The length is arranged to be equal to the coherent length. With this configuration, an optical path difference equivalent to the coherent length is generated between the p-polarized light L3 separated from the light L1 and the p-polarized light L4 separated from the light L2.

  The incident positions of the polarization beam splitter 12, the first mirror 13, the second mirror 14, and the third mirror 15 substantially coincide with the four corners of the rectangular shape. The polarization beam splitter 12, the first mirror 13, the second mirror 14, and the third mirror 15 are all at an angle of approximately 45 degrees with respect to the incident light. When laser light having high directivity is emitted from the light source unit 11, the divergence of the laser light while passing through the polarization beam splitter 12, the first mirror 13, the second mirror 14, and the third mirror 15 can be reduced as much as possible. .

  By reducing the divergence of the laser light, the optical path of the p-polarized light L3 emitted from the light source device 10 can be made substantially coincident with the optical path of the p-polarized light L4. In this way, by adjusting the positions and tilts of the first mirror 13, the second mirror 14, the third mirror 15, and the polarization beam splitter 12, the optical paths of the p-polarized light L3 and L4 transmitted through the polarization beam splitter 12 are substantially matched. Can be made. As a result, it is possible to supply high-quality laser light with less light spread. Since the spread of light can be reduced, the small mirrors 13, 14, 15 and the polarization beam splitter 12 can be used.

  The light source device 10 can emit p-polarized light that is linearly polarized light in a specific vibration direction by using the polarization beam splitter 12. The light source device 10 can effectively reduce speckle by emitting light L3 and L4 having an optical path difference corresponding to the coherent length. By using the first mirror 13, the second mirror 14, and the third mirror 15 provided in the optical path of the light from the polarization beam splitter 12, the disturbance of the wave front can be reduced, and high-quality laser light can be supplied. It becomes. Thereby, there is an effect that speckle can be reduced and high-quality coherent light can be supplied.

  The first mirror 13, the second mirror 14, and the third mirror 15 are optical paths that are reflected by the polarization beam splitter 12 and then enter the polarization beam splitter 12 through the first mirror 13, the second mirror 14, and the third mirror 15. The arrangement is not limited to the case where the length is equal to the coherent length. Such an optical path length may be a coherent length or more. In this case, speckle can be more effectively reduced. Further, the optical path difference may be equal to or less than the coherent length. It is possible to generate an optical path difference of a coherent length or more between the light transmitted through the polarizing beam splitter 12 and the light that has passed through the polarizing beam splitter 12, the first mirror 13, the second mirror 14, and the third mirror 15 a plurality of times. If so, speckle can be reduced.

  FIG. 2 shows a schematic configuration of a light source device 20 according to a modification of the present embodiment. In the light source device 20 of this modification, the polarization beam splitter 12, the first mirror 13, the second mirror 14, and the third mirror 15 are arranged in the same manner as the light source device 10 described above. In the light source device 10 described above, the light source unit 11 is disposed on the straight line on which the polarizing beam splitter 12 and the first mirror 13 are disposed. On the other hand, the light source device 20 of the present modification includes the polarizing beam splitter 12 and The light source unit 11 is arranged on the extension of the straight line on which the third mirror 15 is arranged.

  The light L1 transmitted through the polarizing beam splitter 12 is sequentially reflected by the third mirror 15, the second mirror 14, and the first mirror 13, and then enters the polarizing beam splitter 12. The light L2 reflected by the polarization beam splitter 12 is sequentially reflected by the third mirror 15, the second mirror 14, and the first mirror 13, and then enters the polarization beam splitter 12 again. Also in this modification, speckle can be reduced and high-quality coherent light can be supplied. The polarization beam splitter 12 may transmit s-polarized light and reflect p-polarized light. In this case, the light source device emits s-polarized light. As the light source part 11, what supplies s polarized light can be used. Since the light source device of the present invention can supply linearly polarized light in a specific vibration direction, it is useful when used in combination with a liquid crystal display device.

  FIG. 3 shows a schematic configuration of the light source device 30 according to the second embodiment of the present invention. The light source device 30 of the present embodiment has a ¼ wavelength plate 31. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The quarter-wave plate 31 is a wave plate that generates a phase difference of 90 degrees (π / 2) between the p-polarized component and the s-polarized component, and the polarization state of the light from the polarizing beam splitter 12 is linear. It is a polarizing element that changes from polarized light to circularly polarized light. The quarter wave plate 31 is provided in the optical path of the light from the polarizing beam splitter 12 and between the polarizing beam splitter 12 and the first mirror 13.

  The quarter wavelength plate 31 is disposed so that the lights L1 and L2 from the polarization beam splitter 12 are incident substantially vertically. The quarter-wave plate 31 is arranged such that the optical axis forms 45 degrees with respect to the polarization axis of p-polarized light that is linearly polarized light. Light L <b> 1 from the light source unit 11 passes through the polarization beam splitter 12 and then enters the quarter-wave plate 31. The light L1 is converted from p-polarized light to circularly-polarized light by passing through the quarter-wave plate 31. The light L1 converted into circularly polarized light by the quarter wavelength plate 31 is sequentially reflected by the first mirror 13, the second mirror 14, and the third mirror 15, and then enters the polarizing beam splitter 12. Of the light L 1 that has entered the polarization beam splitter 12, the p-polarized light L 3 is transmitted through the polarization beam splitter 12 and emitted from the light source device 30.

  Of the light L1 incident on the polarization beam splitter 12, the s-polarized light is reflected by the polarization beam splitter 12. The light L2 reflected by the polarizing beam splitter 12 is converted from s-polarized light to circularly-polarized light by passing through the quarter-wave plate 31. The light L2 converted into circularly polarized light by the quarter wavelength plate 31 is sequentially reflected by the first mirror 13, the second mirror 14, and the third mirror 15, and then enters the polarization beam splitter 12. Of the light L2 incident on the polarization beam splitter 12, the p-polarized light L 4 is transmitted through the polarization beam splitter 12 and emitted from the light source device 30. Of the light incident on the polarizing beam splitter 12, s-polarized light is reflected by the polarizing beam splitter 12, and the above-described circulation is repeated.

  By converting linearly polarized light into circularly polarized light by the quarter wavelength plate 31, the p-polarized light that occupies approximately half of the light L1 is transmitted to the polarization beam splitter 12, and the s-polarized light that occupies approximately half of the light L1 is the first. Proceed in the direction of the mirror 13. As a result, the light passing through the polarization beam splitter 12 after passing through each mirror 13, 14, 15 only once can be reduced, and the light circulated from the polarization beam splitter 12 to each mirror 13, 14, 15 can be increased. The more light that is circulated from the polarization beam splitter 12 to each of the mirrors 13, 14, 15, the more light that has passed through different optical path differences can be emitted. Thereby, speckle can be reduced effectively.

  The quarter wave plate 31 is not limited to being disposed in the optical path between the polarization beam splitter 12 and the first mirror 13. It is only necessary to be provided in the optical path of the light from the polarizing beam splitter 12, and it is provided at any position in the optical path from the first mirror 13 to the polarizing beam splitter 12 via the second mirror 14 and the third mirror 15. It is also good. Further, in this embodiment, it is only necessary that the polarization state of the light from the polarization beam splitter 12 can be changed, and the configuration may be changed as appropriate.

  The quarter wave plate 31 is not limited to the case where the optical axis is arranged at 45 degrees with respect to the polarization axis of linearly polarized light. A configuration may be adopted in which the linearly polarized light is converted into elliptically polarized light by arranging the ¼ wavelength plate 31 so that the optical axis forms an angle other than 45 degrees with respect to the polarization axis of the linearly polarized light, for example, 30 degrees. The wave plate is not limited to the case where the quarter wave plate 31 is used. For example, a ½ wavelength plate may be used. The half-wave plate is arranged so that the optical axis is 45 degrees with respect to the polarization axis of the linearly polarized light, thereby changing the vibration direction of the linearly polarized light. Even when a half-wave plate is used, linearly polarized light is elliptically polarized by placing the half-wave plate so that the optical axis is at an angle other than 45 degrees, for example, 30 degrees, with respect to the polarization axis of the linearly polarized light. It can be set as the structure converted into.

  The polarizing element only needs to be able to change the polarization state of the light from the polarizing beam splitter 12, and is not limited to a configuration including a wave plate. For example, the polarizing element may include a liquid crystal element. The liquid crystal element changes the phase of light according to the alignment state of liquid crystal molecules. The liquid crystal element changes the polarization state of the light from the polarization beam splitter 12 according to the alignment state of the liquid crystal molecules. Unlike a liquid crystal display device used in a spatial light modulator described later, a liquid crystal element used as a polarizing element does not need a polarizing plate for emitting only specific linearly polarized light.

  The liquid crystal element can easily change the alignment state of liquid crystal molecules by controlling the voltage. In addition, by adopting a configuration in which voltage application can be controlled for each of the divided cells, the alignment state of the liquid crystal molecules can be changed for each region of the liquid crystal element. As described above, when the liquid crystal element is used, the polarization state of the light from the polarization beam splitter 12 can be easily and randomly changed, and speckle can be further reduced.

  FIG. 4 shows a schematic configuration of a light source device 40 according to Embodiment 3 of the present invention. The light source device 40 of this embodiment includes prisms 42, 43, and 44 provided in place of the mirror. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The polarization beam splitter 41 is configured by bonding two right-angle prisms. A dielectric multilayer film 45 is coated between the two right-angle prisms.

  The polarization beam splitter 41 is a polarization separation unit that separates the p-polarized component and the s-polarized component by transmitting the p-polarized light and reflecting the s-polarized light. The incident surface and the exit surface of the polarization beam splitter 41 may be coated with an antireflection film (AR coating). As in the first embodiment, a plate-shaped polarizing beam splitter 12 (see FIG. 1) may be used. Moreover, in the said Example 1, you may use the polarization beam splitter similar to a present Example.

  The first prism 42, the second prism 43, and the third prism 44 are all right-angle prisms. The first prism 42, the second prism 43, and the third prism 44 can be configured using, for example, a glass member or a quartz member. Each of the prisms 42, 43, and 44 bends the optical path of the incident light by approximately 90 degrees by totally reflecting the incident light on the slope facing the right-angled portion of the right-angle prism. The first prism 42 is a prism that reflects light from the polarization beam splitter 41, and is a first reflecting portion. The first prism 42 bends light from the polarization beam splitter 41 by approximately 90 degrees by total reflection. The second prism 43 is a prism that reflects the light from the first prism 42 and is a second reflecting portion. The second prism 43 bends light from the first prism 42 by approximately 90 degrees by total reflection.

  The third prism 44 is a prism that reflects the light from the second prism 43 and is a third reflecting portion. The third prism 44 bends the light from the second prism 43 by about 90 degrees by total reflection. The incident surface and the exit surface of each prism 42, 43, 44 may be coated with an AR coat. Of the light incident on the polarization beam splitter 41 from the third prism 44, the s-polarized light is reflected by the dielectric multilayer film 45 and travels in the direction of the first prism 42. The first prism 42, the second prism 43, and the third prism 44 are optical paths that are reflected by the polarization beam splitter 41 and enter the polarization beam splitter 41 through the first prism 42, the second prism 43, and the third prism 44. The length is arranged to be equal to the coherent length.

  Also in this embodiment, speckles can be reduced and high-quality coherent light can be supplied. By adopting a configuration in which light is totally reflected in each of the prisms 42, 43, and 44, light loss can be reduced. Further, it is possible to dispense with the deposition of the reflective film. In addition, each prism 42, 43, 44 is not restricted to the structure which totally reflects incident light. Each prism 42, 43, 44 may be configured to reflect incident light using a reflective film formed on a slope.

  FIG. 5 shows a schematic configuration of the light source device 50 according to the first modification of the present embodiment. The optical element 51 transmits light from the light source unit 11. The optical element 51 can be configured using, for example, a glass member or a quartz member. The optical element 51 is a structure having an octagonal shape that is formed by cutting a rectangular portion of a rectangular parallelepiped shape. A right-angle prism 52 is bonded to the slope of the octagonal shape near the light source unit 11. A dielectric multilayer film 45 is coated between the optical element 51 and the right-angle prism 52. The portion of the optical element 51 provided with the dielectric multilayer film 45 and the right-angle prism 52 correspond to the polarizing beam splitter 41 (see FIG. 4).

  The portion of the optical element 51 where the first slope 53 adjacent to the slope where the dielectric multilayer film 45 is provided corresponds to the first prism 42 (see FIG. 4). The portion of the optical element 51 where the second slope 54 adjacent to the first slope 53 is provided corresponds to the second prism 43 described above. The portion of the optical element 51 where the third slope 55 adjacent to the second slope 53 is provided corresponds to the third prism 44 described above. The first inclined surface 53, the second inclined surface 54, and the third inclined surface 55 bend the optical path of the incident light by approximately 90 degrees by totally reflecting the incident light.

  The first inclined surface 53 is a first reflecting portion that reflects light from the dielectric multilayer film 45. The first slope 53 bends light from the dielectric multilayer film 45 by approximately 90 degrees by total reflection. The second slope 54 is a second reflector that reflects light from the first slope 53. The second slope 54 bends light from the first slope 53 by approximately 90 degrees by total reflection. The third slope 55 is a third reflecting portion that reflects light from the second slope 54. The third slope 55 bends light from the second slope 54 by approximately 90 degrees by total reflection. Thus, the optical element 51 is formed with the polarization separation unit and the reflection unit.

  Also in the case of this modification, the speckle can be reduced by emitting light of different optical path differences one after another. Note that the optical element 51 may be configured to reflect incident light using a reflective film formed on the first slope 53, the second slope 54, and the third slope 55. In this modification, in addition to the formation of the optical element 51, it is possible to eliminate the need for precise position adjustment of the polarization separation unit, the first reflection unit, the second reflection unit, and the third reflection unit. There are advantages you can do. Further, by adopting a configuration in which light is circulated in the optical element 51, the number of times light is allowed to pass at the interface between each configuration and air can be reduced. For this reason, it is also possible to reduce the loss of light caused by passing light at the interface between each component and air.

  The optical element is not limited to a structure having an octagonal shape. It is sufficient if light can be circulated using reflection at the interface of the optical element. For example, the light source device 57 shown in FIG. 6 includes a hexagonal optical element 58. The progress of light in the optical element 58 is the same as in the case of the optical element 51 (see FIG. 5). Also in this case, speckle can be reduced.

  FIG. 7 shows a schematic configuration of a light source device 60 according to the second modification of the present embodiment. The light source device 60 includes a low refractive index layer 61 provided between the first optical element 62 and the second optical element 63. The first optical element 62 and the second optical element 63 are optical elements that transmit light from the light source unit 11. The first optical element 62 and the second optical element 63 have a shape that bisects the optical element 58 (see FIG. 6). The first optical element 62 has a dielectric multilayer film 45 and a third inclined surface 55. The second optical element 63 has a first slope 53 and a second slope 54. The low refractive index layer 61 has a refractive index smaller than that of the first optical element 62 and the second optical element 63.

  The light traveling from the dielectric multilayer film 45 toward the first slope 53 passes through the low refractive index layer 61 from the first optical element 62 side and then enters the first slope 53 on the second optical element 63 side. The light traveling in the direction from the second inclined surface 54 to the third inclined surface 55 passes through the low refractive index layer 61 from the second optical element 63 side and then enters the third inclined surface 55 on the first optical element 62 side.

  For example, it is assumed that a part of the light reflected by the first slope 53 travels toward the third slope 55 as indicated by a broken line in the figure. The light traveling toward the third slope 55 travels in the direction of the second slope 54 due to total reflection at the low refractive index layer 61. In addition, the light traveling from the third inclined surface 55 toward the first inclined surface 53 is also advanced toward the dielectric multilayer film 45 by total reflection at the low refractive index layer 61. As described above, by providing the low refractive index layer 61, light can be accurately advanced in the order of the dielectric multilayer film 45, the first slope 53, the second slope 54, the third slope 55, and the dielectric multilayer film 45. Is possible. By causing the light to travel accurately, it is possible to reduce light loss due to passing through the polarization separation unit and the reflection unit.

  In the case of the configuration of the light source device 60, light having a relatively large incident angle enters the low refractive index layer 61. Therefore, even if the difference between the refractive indexes of the optical elements 62 and 63 and the refractive index of the low refractive index layer 61 is relatively small, for example, a difference of about 0.2, the total reflection condition can be sufficiently satisfied. . For example, when the refractive index of the optical elements 62 and 63 is 1.5, the low refractive index layer 61 can be constituted by a member having a refractive index of about 1.3, for example, a transparent adhesive. By using the low refractive index layer 61 made of a transparent adhesive, the first optical element 62 and the second optical element 63 can be bonded and the light can be totally reflected. The low refractive index layer 61 may be any solid, liquid, or gas as long as the light traveling in the optical elements 62 and 63 can be efficiently totally reflected. For example, an air layer formed by providing a gap between the first optical element 62 and the second optical element 63 may be used as the low refractive index layer.

  FIG. 8 shows a schematic configuration of a projector 70 that is an image display apparatus according to Embodiment 4 of the present invention. The projector 70 is a front projection type projector that views light by supplying light to the screen 75 and observing light reflected by the screen 75. The projector 70 has a lighting device 72. The illumination device 72 has a light source device 71. The projector 70 displays an image using light from the light source device 71.

  FIG. 9 shows a schematic configuration of the illumination device 72. FIG. 10 shows a schematic configuration of the light source device 71. The light source device 71 has the same configuration as the light source device 57 (see FIG. 6). The light source unit 76 of the light source device 71 has a plurality of laser light sources. The light source unit 76 includes a laser light source that supplies red (R) laser light, a laser light source that supplies green (G) light, and a laser light source that supplies blue (B) light in parallel. The laser light source supplies laser light that is coherent light. The light source unit 76 is not limited to the case where five laser light sources are arranged in parallel in one direction, and five or more or five or less laser light sources may be arranged in an array. In the light source devices of the above embodiments, a plurality of laser light sources may be arranged in an array.

  The light from the light source device 71 is converged by the first lens 77 and the second lens 78 and then enters the diffractive optical element 79. The first lens 77 and the second lens 78 are a convex lens and a concave lens, respectively. The diffractive optical element 79 is a homogenizing optical system that diffracts the laser light to make the intensity distribution of the light beam from the light source device 71 uniform. The diffractive optical element 79 shapes and enlarges the illumination area of the laser light according to the rectangular shape of the spatial light modulator 73. As the diffractive optical element 79, for example, a computer generated hologram (CGH) can be used. The illuminating device 72 is constituted by each part from the light source device 71 to the diffractive optical element 79.

  By converging the light by the first lens 77 and the second lens 78, the diffractive optical element 79 can be reduced in size. By reducing the size of the diffractive optical element 79, the angle range of light incident on the spatial light modulator 73 from the diffractive optical element 79 can be reduced, and light loss can be reduced. The illumination device 72 is not limited to the configuration in which the first lens 77 and the second lens 78 are provided, and may be changed as appropriate.

  Returning to FIG. 8, the illumination device 72 sequentially supplies R light, G light, and B light. The spatial light modulator 73 is a transmissive liquid crystal display device that modulates sequentially supplied color lights according to an image signal. As the transmissive liquid crystal display device, for example, a high temperature polysilicon TFT liquid crystal panel (HTPS) can be used. The light modulated by the spatial light modulator 73 is projected onto the screen 75 by the projection lens 74. By using the light source device 71, speckle can be reduced and high-quality laser light can be supplied. This produces an effect that a high-quality and bright image can be displayed by reducing speckles.

  FIG. 11 shows a schematic configuration of the illumination device 80 according to the first modification of the present embodiment. The illumination device 80 of this modification can be applied to the projector 70 described above. The illumination device 80 of this modification has a fly-eye lens 81. The fly-eye lens 81 is a uniformizing optical system that uniformizes the intensity distribution of the light beam from the light source device 71. The fly-eye lens 81 has lens elements 82 arranged in an array in the two-dimensional direction. The fly-eye lens 81 makes the intensity distribution of the light beam uniform by superimposing the light from each lens element 82 on the spatial light modulator 73. Each lens element 82 is substantially similar to the rectangular shape of the spatial light modulator 73. With this configuration, the fly-eye lens 81 shapes and enlarges the illumination area of the laser light in accordance with the rectangular shape of the spatial light modulator 73. Also in the case of this modification, a high-quality and bright image can be displayed by reducing speckles.

  FIG. 12 shows a schematic configuration of the illumination device 90 according to the second modification of the present embodiment. The illumination device 90 of this modification can be applied to the projector 70 described above. The lighting device 90 of this modification includes a rod integrator 92. The rod integrator 92 is a homogenizing optical system that makes the intensity distribution of the light beam from the light source device 71 uniform. The condensing lens 91 condenses the light from the light source device 71 on the incident surface of the rod integrator 92. The rod integrator 92 can be configured using a rectangular parallelepiped glass member or quartz member. The light incident on the rod integrator 92 propagates inside the rod integrator 92 while repeating total reflection at the interface of the rod integrator 92.

  By repeating the reflection in the rod integrator 92, the intensity distribution of the light flux is made substantially uniform on the exit surface of the rod integrator 92. The exit surface of the rod integrator 92 is substantially similar to the rectangular shape of the spatial light modulator 73. By using the rod integrator 92, the uniform intensity distribution and the rectangular transformation are performed at the same time. The illumination lens 93 enlarges the light from the rod integrator 92 and makes it incident on the spatial light modulator 73. Also in the case of this modification, a high-quality and bright image can be displayed by reducing speckles. The rod integrator 92 can emit light whose traveling direction is controlled as compared with the case where an optical fiber is used. As the rod integrator, a hollow structure rod integrator configured using a highly reflective member may be used.

  The projector may be configured to use a plurality of transmissive liquid crystal display devices. For example, when three transmissive liquid crystal display devices are used, the projector can be configured to include lighting devices for R light, G light, and B light. Further, the spatial light modulator is not limited to a transmissive liquid crystal display device, and a reflective liquid crystal display device (Liquid Crystal On Silicon: LCOS) may be used. The projector may be a so-called rear projector that supplies laser light to one surface of the screen and observes an image by observing light emitted from the other surface of the screen.

  FIG. 13 shows a schematic configuration of a liquid crystal display 100 which is an image display device according to the third modification of the present embodiment. The liquid crystal display 100 displays an image using light from the light source device 71. Light from the light source device 71 enters the light guide plate 101. The light guide plate 101 is a uniformizing optical system that makes the intensity distribution of the light flux from the light source device 71 uniform and travels in the direction of the display panel 102. The display panel 102 is a transmissive liquid crystal display device that displays an image by transmitting light from the light guide plate 101. Also in the case of this modification, a high-quality and bright image can be displayed by reducing speckles.

  As described above, the light source device according to the present invention is suitable for displaying an image using coherent light.

The figure which shows schematic structure of the light source device which concerns on Example 1 of this invention. FIG. 6 is a diagram illustrating a schematic configuration of a light source device according to a modification of the first embodiment. The figure which shows schematic structure of the light source device which concerns on Example 2 of this invention. The figure which shows schematic structure of the light source device which concerns on Example 3 of this invention. FIG. 10 is a diagram illustrating a schematic configuration of a light source device according to a first modification of the third embodiment. The figure explaining a structure provided with a hexagonal optical element. FIG. 10 is a diagram illustrating a schematic configuration of a light source device according to a second modification of the third embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a projector according to a fourth embodiment of the invention. The figure which shows schematic structure of an illuminating device. The figure which shows schematic structure of a light source device. FIG. 10 is a diagram illustrating a schematic configuration of a lighting device according to a first modification of the fourth embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a lighting device according to a second modification of the fourth embodiment. FIG. 10 is a diagram illustrating a schematic configuration of a liquid crystal display according to a third modification of the fourth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Light source device, 11 Light source part, 12 Polarization beam splitter, 13 1st mirror, 14 2nd mirror, 15 3rd mirror, 20 Light source device, 30 Light source device, 31 1/4 wavelength plate, 40 Light source device, 41 Polarized beam Splitter, 42 First prism, 43 Second prism, 44 Third prism, 50 Light source device, 51 Optical element, 52 Right angle prism, 53 First slope, 54 Second slope, 55 Third slope, 57 Light source device, 58 Optical Element, 60 light source device, 61 low refractive index layer, 62 first optical element, 63 second optical element, 70 projector, 71 light source device, 72 illumination device, 73 spatial light modulator, 74 projection lens, 75 screen, 76 light source Part, 77 first lens, 78 second lens, 79 diffractive optical element, 80 illumination device, 81 fly eye lens 82 lens elements, 90 lighting apparatus, 91 a condenser lens, 92 a rod integrator, 93 illumination lens, 100 a liquid crystal display, 101 light guide plate, 102 display panel

Claims (12)

A light source unit that supplies coherent light and includes light including a first polarization component having a first vibration direction;
The first polarized component and the second polarized light are transmitted by transmitting the first polarized component light and reflecting the second polarized component light having a second vibration direction substantially orthogonal to the first vibration direction. A polarization separation unit that separates components;
A reflection unit that is provided in an optical path of light from the polarization separation unit, and that is incident on the polarization separation unit by reflecting light from the polarization separation unit;
The reflection unit includes light that has passed through the polarization separation unit out of light incident on the polarization separation unit from the reflection unit, and light that has been reflected by the polarization separation unit and further incident on the polarization separation unit through the reflection unit. A light path device that generates an optical path difference with the light transmitted through the polarization separation unit.   The reflection unit is arranged so that an optical path length from the reflection by the polarization separation unit to the incidence to the polarization separation unit through the reflection unit is equal to or longer than the coherent length of the coherent light. The light source device according to claim 1.   The reflection unit reflects the light that has passed through the polarization separation unit out of the light incident on the polarization separation unit from the reflection unit, and is reflected by the polarization separation unit and then enters the polarization separation unit through the reflection unit. 3. The light source device according to claim 1, wherein an optical path of light transmitted through the polarization separation unit is substantially matched with the light that has been transmitted.   The reflection unit includes a first reflection unit that reflects light from the polarization separation unit, a second reflection unit that reflects light from the first reflection unit, and a second reflection unit that reflects light from the second reflection unit. The light source device according to any one of claims 1 to 3, further comprising three reflecting portions.   5. The light source according to claim 1, further comprising: a polarizing element that is provided in an optical path of light from the polarization separation unit and changes a polarization state of light from the polarization separation unit. apparatus.   The light source device according to claim 5, wherein the polarizing element includes a wave plate.   The light source device according to claim 1, wherein the reflection unit includes a mirror.   The light source device according to claim 1, wherein the reflection unit includes a prism. An optical element that transmits light from the light source unit;
The light source device according to claim 1, wherein the polarization separation unit and the reflection unit are formed in the optical element.   The light source device according to claim 9, further comprising a low refractive index layer having a refractive index smaller than that of the optical element. The light source device according to any one of claims 1 to 10,
And a homogenizing optical system for homogenizing the intensity distribution of the luminous flux from the light source device.   An image display device that displays an image using light from the light source device according to claim 1.

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