JP2008135838A - Light source device and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device and an image display device that are kept low-cost with simple constitution, can suppress glossiness of emitted light and improve reliability. <P>SOLUTION: The optical path difference between light traveling along a first optical path A1 which is an optical path of light emitted by a laser light source 11 to pass through an external resonator 14 and travel to an optical element 15 and light traveling along a second optical path B3 which is an optical path of light emitted by the laser light source 11. reflected by the external resonator 14 to pass through a separation unit 12, and reflected by a reflecting unit 17 to travel to the optical element 15 is larger than a distance such that interference between laser light beams is reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source device and an image display device including the same.

In recent projection type image display apparatuses, a discharge lamp such as an ultrahigh pressure mercury lamp is generally used as a light source. However, such a discharge lamp has problems such as a relatively short life, difficulty in instantaneous lighting, a narrow color reproduction range, and ultraviolet light emitted from the lamp may deteriorate the liquid crystal light bulb. Therefore, a projection type image display apparatus using a laser light source that emits monochromatic light instead of such a discharge lamp has been proposed. A laser light source as described in Patent Documents 1 to 3 can be used for such a projection type image display device. However, the laser light source does not have the above-described problems, but has a defect that it has coherence. Therefore, a laser illumination device in which the coherence of laser light is reduced has been proposed (see, for example, Patent Document 4).
The laser display device described in Patent Document 1 includes red, green, and blue semiconductor lasers, a plurality of collimator lenses that collimate laser light emitted from the semiconductor lasers, and light that is collimated by the collimator lenses. And a spatial light modulator that modulates the light emitted from each microlens. The light that has passed through each spatial light modulator is combined by a dichroic mirror and displayed on a screen by a projector lens. In this laser display device, the microlens can be rotated about the optical axis, and the speckle noise of the laser light irradiating the spatial light modulator is reduced or eliminated by rotating the microlens. It has become.
JP 59-128525 A Japanese Patent Laid-Open No. 7-86668 US Pat. No. 5,762,227 JP 2003-31872 A

  However, in the laser display device described in Patent Document 1, since the microlens is rotated in order to reduce speckle, mechanical parts such as a rotational drive system are required, and the cost increases. Further, noise associated with the rotation of the rotation drive system is generated, or the rotation drive system deteriorates due to long-term use, resulting in a decrease in reliability.

  The present invention has been made to solve the above-described problem, and is a light source device capable of reducing the cost with a simple configuration, suppressing occurrence of glare of emitted light, and improving reliability. An object of the present invention is to provide an image display device.

In order to achieve the above object, the present invention provides the following means.
The light source device of the present invention includes a laser light source, a wavelength conversion element that converts the wavelength of light emitted from the laser light source into a predetermined wavelength, and converts the light emitted from the wavelength conversion element into the predetermined wavelength. An external resonator that transmits the reflected light, reflects the light that has not been converted to the predetermined wavelength, and returns the light toward the laser light source, and uses the light emitted from the external resonator to change the optical element. A light source device that illuminates the light modulation device via the laser light source and is disposed between the laser light source and the wavelength conversion element, and is directed toward the laser light source among the light reflected by the external resonator In the optical path, the light converted to the predetermined wavelength by passing through the wavelength conversion element is reflected and guided to a position different from the laser light source, and the light that has not been converted to the predetermined wavelength A separation unit that transmits light toward the laser light source; and a reflection unit that reflects light reflected by the separation unit toward the optical element. The optical element is emitted from the laser light source and passes through the external resonator. A light traveling in a first optical path, which is an optical path of light traveling toward the optical path, and an optical path of light emitted from the laser light source, reflected by the external resonator, reflected by the reflective section via the separation section, and directed toward the optical element An optical path difference with light traveling in a second optical path is not less than a distance at which interference between the laser beams is reduced.

  In the light source device according to the present invention, the light emitted from the laser light source passes through the wavelength conversion element. Of the light emitted from the wavelength conversion element, the light converted into light of a predetermined wavelength passes through the external resonator and enters the optical element. On the other hand, of the light emitted from the wavelength conversion element, the light that has not been converted to the predetermined wavelength is reflected by the external resonator, returned to the laser light source, and passes through the wavelength conversion element again. A part of the light is converted into a predetermined wavelength. In the present invention, in the light reflected by the external resonator, the light converted to a predetermined wavelength by passing through the wavelength conversion element in the optical path toward the laser light source is separated in the separation unit. Reflected and guided to a position different from the laser light source. Further, the light is then incident on the optical element by being reflected by the reflecting portion.

Furthermore, in the present invention, light emitted from the light source, travels through the first optical path that passes through the external resonator and travels toward the optical element, and light travels through the second optical path that is reflected by the external resonator and the separation unit and travels toward the optical element. Is equal to or longer than the distance at which the interference between the laser beams is reduced, the coherence between the light traveling on the first optical path and the light traveling on the second optical path can be reduced. Therefore, in the present invention, since a rotational drive system is not used as in the prior art, the configuration is simple, so that the cost can be reduced and the occurrence of glare of emitted light can be suppressed. Furthermore, since the present invention does not deteriorate even when used for a long period of time, it is possible to improve the reliability.
Further, since the laser light traveling in the second optical path is light reflected by the external resonator, the speckle pattern is different from the light traveling in the first optical path. Therefore, glare of light emitted from the optical element can be further suppressed.

  The light source device of the present invention includes a first branching unit that splits the light traveling in the first optical path into a third optical path and a fourth optical path, and the light traveling in the second optical path as a fifth optical path and a sixth optical path. A second branching portion for branching into the optical path, an optical path difference between the light traveling in the third optical path and the laser light traveling in the fourth optical path, and the laser light traveling in the fifth optical path and the sixth optical path It is preferable that the optical path difference with the laser light traveling through the distance is greater than or equal to the distance at which interference between the laser lights is reduced.

  In the light source device according to the present invention, the light transmitted through the external resonator is branched into the third optical path and the fourth optical path by the first branching unit. Further, the light reflected by the separating unit and reflected by the reflecting unit is branched into the fifth optical path and the sixth optical path by the second branching unit. At this time, by setting the distance to be longer than the distance at which the interference between the laser beams is reduced, the coherency between the light traveling in the first optical path and the light traveling in the second optical path is reduced, so that interference is further increased. The light with reduced properties is incident on the optical element. Therefore, glare of light emitted from the optical element can be suppressed.

  The light source device of the present invention includes a laser light source, a wavelength conversion element that converts the wavelength of light emitted from the laser light source into a predetermined wavelength, and converts the light emitted from the wavelength conversion element into the predetermined wavelength. An external resonator that transmits the reflected light, reflects the light that has not been converted to the predetermined wavelength, and returns the light toward the laser light source, and the optical element uses the light emitted from the external resonator. A light source device that illuminates the light modulation device via the laser light source, the light source device disposed between the laser light source and the wavelength conversion element, and of the light reflected by the external resonator toward the laser light source In the optical path to go, the light converted to the predetermined wavelength by passing through the wavelength conversion element is reflected and guided to a position different from the laser light source, and the light that has not been converted to the predetermined wavelength A separation unit that transmits light toward the laser light source, a reflection unit that reflects light reflected by the separation unit toward the optical element, and a laser beam that is emitted from the laser light source and passes through the external resonator. A first optical path that is an optical path of light that travels, or a second light that is an optical path of light that is emitted from the laser light source, reflected by the external resonator, reflected by the reflective section via the separation section, and travels toward the optical element An optical member having a refractive index different from that of air provided on the road is provided.

  In the light source device according to the present invention, in the light source device according to the present invention, the light emitted from the laser light source passes through the wavelength conversion element. Of the light emitted from the wavelength conversion element, the light converted into light of a predetermined wavelength passes through the external resonator and enters the optical element. On the other hand, of the light emitted from the wavelength conversion element, the light that has not been converted to the predetermined wavelength is reflected by the external resonator, returned to the laser light source, and passes through the wavelength conversion element again. A part of the light is converted into a predetermined wavelength. In the present invention, in the light reflected by the external resonator, the light converted to a predetermined wavelength by passing through the wavelength conversion element in the optical path toward the laser light source is separated in the separation unit. Reflected and guided to a position different from the laser light source. Further, the light is then incident on the optical element by being reflected by the reflecting portion.

  Furthermore, in the present invention, for example, by using glass as the optical member, the optical path length of the portion where the optical member is arranged in the optical path length of the laser light traveling in the first optical path or the second optical path is refracted by the optical member. It will be doubled. Accordingly, an optical path difference is generated between the optical path length of the laser light traveling in the first optical path and the optical path length of the laser light traveling in the second optical path, so that the coherence between the laser lights is reduced. Thereby, it is possible to suppress the occurrence of glare of light emitted from the optical element. That is, the optical member makes it possible to obtain a long optical path length with a short distance for the optical path length of the laser light traveling in the first optical path or the second optical path. Therefore, in the present invention, since the optical path length of the light traveling in the first optical path or the second optical path can be increased without increasing the size of the entire apparatus, it is possible to reduce the size of the entire apparatus. .

In the light source device of the present invention, it is preferable that the optical member is a phase changing unit that temporally changes the phase of light traveling in the first optical path or the second optical path.
In the light source device according to the present invention, the light traveling in the first optical path or the second optical path is transmitted through the phase changing means. At this time, since the phase of the light emitted from the phase changing means changes with time, the speckle pattern changes with time, so that the light emitted from the optical element is integrated over time by the afterimage effect. As a result, the coherence is lowered, and as a result, the light is reduced in glare. Therefore, with a simple structure, the occurrence of glare in the emitted light is suppressed, and since a rotational drive system is not used as in the prior art, the present invention does not deteriorate even when used for a long time, improving reliability. It becomes possible to make it.

Further, the light source device of the present invention may be a refractive index changing unit that temporally changes a refractive index of light traveling in the first optical path or the second optical path, instead of the optical member being a phase changing unit. good.
In the light source device according to the present invention, the light traveling in the first optical path or the second optical path is transmitted through the refractive index changing means. At this time, since the refractive index of the light emitted from the refractive index changing means changes, the optical path length of the portion where the optical member is disposed is double the refractive index of the optical member. Therefore, since the optical path difference between the first optical path and the second optical path can be changed with time, the optical path difference is not made longer than the coherence length, and glare due to coherence is made difficult to perceive with a short optical path difference. Is possible.

An image display device according to the present invention includes the above light source device, a light modulation device that modulates light emitted from the light source device in accordance with an image signal, and a projection device that projects light modulated by the light modulation device. It is characterized by providing.
In the image display device according to the present invention, the light emitted from the light source device enters the light modulation device. Then, the image modulated by the light modulation device is projected by the projection device. At this time, since the light emitted from the light source device is light with suppressed generation of speckle patterns as described above, a good image can be displayed.

  Embodiments of a light source device and an image display device according to the present invention will be described below with reference to the drawings. In the following drawings, the scale of each member is appropriately changed in order to make each member a recognizable size.

[First Embodiment]
The light source device 10 according to the present embodiment converts the wavelength of light emitted from the laser light source 11 and illuminates the liquid crystal light valve (light modulation device) 20 via a rod integrator (optical element) 15. Specifically, as shown in FIG. 1, the light source device 10 includes a laser light source 11 that emits monochromatic light, a wavelength conversion element 13 that converts the wavelength of laser light emitted from the laser light source 11, and a laser light source 11. Of the laser light emitted from the dichroic mirror (separating unit) 12 and the wavelength conversion element 13 disposed between the wavelength conversion element 13 and the wavelength conversion element 13, and transmits the other light. An external resonator 14, a reflection mirror (reflection part) 17 that reflects the laser light reflected by the dichroic mirror 12 to the rod integrator 15, and a λ / 2 plate (polarization) disposed between the reflection mirror 17 and the rod integrator 15. Conversion means: phase difference plate) 18.

In the present embodiment, the wavelength of light emitted from the laser light source 11 is 920 nm for a blue laser light source device that emits blue laser light, 1060 nm for a green laser light source device that emits green laser light, and red. In the case of a red laser light source device that emits a laser beam of 1240 nm, the wavelength is 1240 nm. However, this wavelength is only an example. As the laser light source 11, for example, a single semiconductor laser or an array of a plurality of semiconductor lasers can be used.
The laser light source 11 emits linearly polarized light, and in the present embodiment, as indicated by an arrow in FIG. 1, it emits P-polarized laser light.

A wavelength conversion element (SHG: Second Harmonic Generation) 13 is an optical element that converts incident light into a predetermined wavelength. In the case of the present embodiment, light emitted from the laser light source 11 and directed to the external resonator 14 is converted into light having substantially a half wavelength by passing through the wavelength conversion element 13. That is, in the case of a blue laser light source device, light (920 nm) emitted from the laser light source is converted into blue light of 460 nm by the wavelength conversion element. Similarly, in the case of a green laser light source device, the light emitted from the laser light source (1060 nm) is 530 nm green light, and in the case of the red laser light source device, the light emitted from the laser light source (1240 nm) is 620 nm red. Converted to light. However, the conversion efficiency of the wavelength conversion element 13 is about 40 to 50%. That is, not all of the light emitted from the laser light source 11 is converted into a laser beam having about half the wavelength. Therefore, the laser light emitted from the wavelength conversion element 13 is a mixture of laser light converted to a predetermined wavelength and laser light that has not been converted. The wavelength conversion efficiency by the wavelength conversion element 13 has non-linear characteristics. For example, the higher the intensity of the laser light incident on the wavelength conversion element, the higher the conversion efficiency. An optical path from the laser light source 11 to the external resonator 14 is defined as an outward path OW.
Here, a plate-shaped waveguide type is used as the wavelength conversion element 13. When such a waveguide type wavelength conversion element 13 is employed, the thickness of the wavelength conversion element 13 is thin, so that it is easy to create a periodic polarization inversion structure, to easily increase the wavelength conversion efficiency, and to reduce the manufacturing cost. it can.

The external resonator 14 transmits laser light converted to a predetermined wavelength (in the present embodiment, approximately half of the wavelength) out of the laser light emitted from the wavelength conversion element 13, and is not converted to the predetermined wavelength. The reflected laser beam is reflected back toward the wavelength conversion element 13. In the present embodiment, the external resonator 14 selectively reflects only light that has not been converted to a predetermined wavelength by the wavelength conversion element 13 out of the light emitted from the wavelength conversion element 13 with a high efficiency of about 99%. It has the characteristics to do. The light converted to a predetermined wavelength (920 nm for a blue laser light source, 530 nm for a green laser light source, 620 nm for a red laser light source) by the wavelength conversion element 13 passes through the external resonator 14.
The laser beam that has passed through the external resonator 14 enters the rod integrator 15 as it is. In this way, the optical path of the laser light that passes through the external resonator 14 and travels toward the rod integrator 15 is defined as a first optical path A1. In the present embodiment, the first optical path A1 indicates the central axis of the laser beam that passes through the external resonator 14 and travels toward the rod integrator 15.

  On the other hand, light that has not been converted to a predetermined wavelength by the wavelength conversion element 13 (light having a wavelength of 920 nm for a blue laser light source, 530 nm for a green laser light source, and 620 nm for a red laser light source) 14 is reflected. Then, it passes through the wavelength conversion element 13 again and returns to the laser light source 11. In this way, the optical path from the external resonator 14 toward the laser light source 11 is defined as a return path HW. In a general laser light source device, such light is returned to the laser light source 11 as it is. However, there is also light that is converted into a predetermined wavelength by the wavelength conversion element 13 in the process of returning from the external resonator 14 toward the laser light source 11. The “predetermined wavelength” here is the same wavelength as the light transmitted through the external resonator 14 (that is, 460 nm for a blue laser light source device, 530 nm for a green laser light source device, and a red laser light source device). In the case of 620 nm). The dichroic mirror 12 prevents the laser light converted to a predetermined wavelength in the return path from returning to the laser light source 11 as it is. Specifically, the dichroic mirror 12 is disposed between the laser light source 11 and the wavelength conversion element 13, and of the laser light reflected by the external resonator 14, the optical path toward the laser light source 11 (return path HW). , The laser beam converted to the predetermined wavelength by passing through the wavelength conversion element 13 is reflected and guided to a position different from the laser light source 11, and the laser light that has not been converted to the predetermined wavelength is directed to the laser light source 11. It is made to pass through. The reflection surface of the dichroic mirror 12 is arranged so that light on the return path HW is incident at 45 degrees. Therefore, the laser beam converted to a predetermined wavelength in the return path HW is bent 90 degrees by the dichroic mirror 12.

The light that has not been converted to the predetermined wavelength in the return path HW passes through the dichroic mirror 12 and is returned to the laser light source 11 as it is. Thus, the light returned to the laser light source 11 is partially absorbed by the laser light source 11 and becomes heat, but most of the light is used as energy of the laser light source 11 or reflected by the laser light source 11. It is effectively used by being emitted from the laser light source again.
The reflection mirror 17 reflects the laser beam having a predetermined wavelength reflected by the dichroic mirror 12 toward the rod integrator 15. The reflection surface of the reflection mirror 17 is arranged so that the laser beam reflected by the dichroic mirror 12 is incident at an angle θ1.

  The optical path of the laser light emitted from the laser light source 11 and reflected by the external resonator 14 and transmitted through the wavelength conversion element 13 and directed to the reflection mirror 17 via the dichroic mirror 12 is defined as a first return path B1. Further, the optical path of the laser beam reflected by the reflection mirror 17 and traveling toward the rod integrator 15 is defined as a second return path B2. At this time, since the laser light emitted from the laser light source 11 resonates between the laser light source 11 and the external resonator 14, the optical path length between the dichroic mirror 12 and the external resonator 14 in the first return path B1 is It does not contribute to the first return path B1. In the present embodiment, the first return path B1 indicates the central axis of the laser light reflected by the dichroic mirror 12 and directed to the reflection mirror 17, and the second return path B3 is reflected by the reflection mirror 17. The central axis of the laser beam toward the rod integrator 15 is shown.

The distance L1 between the dichroic mirror 12 and the reflection mirror 17 is about 5 mm. Therefore, the optical path difference between the optical path length of the forward path A1 and the optical path length of the return path B3 (second optical path: B1 + B2) that is the sum of the optical path lengths of the first return path B1 and the second return path B2 is the distance L1 (5 mm). Become.
This optical path difference L1 (5 mm) is a distance for reducing interference between the laser light traveling on the forward path A1 and the laser light traveling on the return path B3.

  The rod integrator 15 makes the in-plane illuminance distribution of the laser light substantially uniform at the emission end face. The laser light traveling on the first forward path A1 and the laser light traveling on the second backward path B2 are incident on the rod integrator 15 and reflected therein. Then, on the exit end face of the rod integrator 15, the illumination light is emitted as illumination light with a substantially uniform in-plane illuminance distribution. The liquid crystal light valve 20 is illuminated by the laser light having a uniform in-plane illuminance distribution.

In the light source device 10 according to the present embodiment, the optical path difference between the laser light emitted from the laser light source 11 and traveling on the forward path A1 and the laser light traveling on the return path B3 is a distance L1 at which interference between the laser lights is reduced. Therefore, it becomes possible to reduce the coherence between the laser beam traveling on the forward path A1 and the light traveling on the return path B3. Therefore, since the structure is simple, the cost is suppressed, the occurrence of glare (scintillation, speckle) of emitted light is suppressed, and a rotational drive system is not used as in the prior art. Since deterioration does not occur even when used, reliability can be improved. Further, since the laser light traveling on the return path B3 is laser light reflected by the external resonator 14, the speckle pattern differs from the laser light traveling on the forward path A1. Therefore, glare of light emitted from the rod integrator 15 can be further suppressed.
Although the distance L1 between the dichroic mirror 12 and the reflection mirror 17 is about 5 mm, if it is 5 mm or more, interference between the laser light traveling in the forward path A1 and the laser light traveling in the backward path B3 can be reduced. it can. That is, in this embodiment, since the speckle pattern of the laser light emitted from the laser light source 11 and the laser light reflected by the external resonator 14 are different, the coherence length of the laser light source 11 is several cm to several m. Even if the optical path difference between the forward path A1 and the return path B3 is about 5 mm, the interference can be reduced. If the optical path length of the forward path A1 and the optical path length of the return path B3 can be made longer, the distance L1 is made longer than the coherence length of the laser light source 11, thereby ensuring glare of the light emitted from the rod integrator 15. It becomes possible to reduce it.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described with reference to FIG. In each embodiment described below, portions having the same configuration as those of the light source device 10 according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
The light source device 30 according to the present embodiment is different from the first embodiment in that the laser light traveling on the forward path A1 and the laser light traveling on the return path B2 are branched.

In the light source device 30, a half mirror (first branch portion) 32 that branches the laser light traveling in the forward path A <b> 1 is provided between the rod integrator 31 and the external resonator 14. The half mirror 32 is a member that divides green laser light transmitted through the external resonator 14 into reflected light and transmitted light at a predetermined ratio. That is, the laser light traveling in the forward path A1 by the half mirror 32 is transmitted through the half mirror 32, the first forward path (third optical path) C1, and the second forward path (fourth optical path) C2 that reflects the half mirror 32. Branches to.
Further, the light source device 30 includes a reflection mirror 33 that reflects the laser light traveling on the second forward path C <b> 2 reflected by the half mirror 32 to the rod integrator 31.

Further, between the rod integrator 31 and the reflection mirror 17, a half mirror (second branch portion) 37 that branches the laser light traveling in the second return path B2 is provided. The half mirror 37 is a member that divides the green laser light reflected by the reflection mirror 17 into reflected light and transmitted light at a predetermined ratio. That is, the laser light traveling in the second return path B2 by the half mirror 37 is transmitted through the half mirror 37, the first return path (fifth optical path) D1, and the second return path (sixth optical path) D2 reflected by the half mirror 37. Branches to and.
Furthermore, the light source device 30 includes a reflection mirror 38 that reflects the laser light traveling on the second return path D <b> 2 reflected by the half mirror 37 to the rod integrator 31.

The distance L2 between the half mirror 32 and the reflection mirror 33 and the distance L3 between the half mirror 37 and the reflection mirror 38 are 5 mm, respectively. Thus, the optical path difference between the optical path length of the first forward path C1 and the optical path length of the second forward path C2 is the distance L2. Similarly, the optical path difference between the optical path length of the first return path D1 and the optical path length of the second return path D2 is a distance L3.
This distance L2 is a distance that reduces interference between the laser light traveling on the first forward path C1 and the laser light traveling on the second forward path C2. Similarly, the distance L3 is a distance at which interference between the laser light traveling on the first return path D1 and the laser light traveling on the second return path D2 is reduced.

  The light source device 30 according to the present embodiment has the same effects as the light source device 10 of the first embodiment. Furthermore, in the light source device 30 according to the present embodiment, the laser light traveling on the first forward path C1 and the laser light traveling on the second forward path C2, and the laser light traveling on the first backward path D1 and the second backward path D2 are transmitted. Since the distance between the traveling laser beams is reduced, the interference of the laser beams incident on the rod integrator 31 can be further reduced. Therefore, the laser light emitted from the rod integrator 31 is light with reduced glare.

[Third Embodiment]
Next, a third embodiment according to the present invention will be described with reference to FIGS.
The light source device 40 according to the present embodiment is different from the first embodiment in that a glass (optical member) 41 is provided in the first return path B1.
The glass 41 has a refractive index n, and a dimension along the optical axis P is d. Accordingly, since the optical path length of the glass 41 is nd, the optical path length of the laser light transmitted through the glass 41 in the first return path B1 is double the refractive index of the glass 41. The glass 41 is preferably made of a material having a high refractive index, and for example, a high refractive index glass material for spectacle lens use is used.
Further, the refractive index n and the dimension d (the optical path length nd of the glass 41) of the glass 41 are such that the optical path difference between the laser light traveling on the forward path A1 and the laser light traveling on the return path B3 reduces interference between the laser lights. It is set to be a distance. The refractive index n and the dimension d are preferably set so that the optical path difference between the optical path length of the forward path A1 and the optical path length of the return path B3 is longer than the coherence length of the laser light source 11.

  The light source device 40 according to the present embodiment has the same effects as the light source device 10 of the first embodiment. Furthermore, in the light source device 40 according to the present embodiment, an effective optical path equivalent to increasing the physical distance of the first return path B1 while shortening the physical distance of the first return path B1 by the glass 41. It is possible to obtain a length. Therefore, since the optical path length of the light traveling in the return path B3 can be increased without increasing the size of the entire device, it is possible to reduce the size of the entire device.

[Modification of Third Embodiment]
In the present embodiment, the glass 41 is provided in the first return path B1, but as shown in FIG. 4, a light source device 45 in which the glass 41 is provided in the second return path B2 may be used. In this configuration, the distance of the first return path B1 can be shortened, so that the dichroic mirror 12 and the reflection mirror 17 can be arranged close to each other. Therefore, the entire apparatus can be reduced in size.
Further, since the distance between the laser light traveling in the forward path A1 and the laser light traveling in the second return path B2 is narrower than that of the light source device 40 of the above embodiment, the opening of the rod integrator 46 used in the light source device 45 is made small. can do. That is, since the rod integrator 46 that is smaller than the rod integrator 15 is sufficient, an inexpensive rod integrator 46 can be used. That is, it is possible to provide the light source device 45 with reduced cost.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described with reference to FIGS.
The light source device 50 according to the present embodiment is different from the first embodiment in that a liquid crystal element (phase changing means) 51 is provided in the first return path B1.

  As shown in FIG. 5, the liquid crystal element 51 has a configuration in which a liquid crystal layer 51c is sandwiched between a first electrode 51a and a second electrode 51b. The first and second electrodes 51 a and 51 b are connected to the drive circuit 55. The drive circuit 55 controls the voltage applied to the liquid crystal element 51 and temporally changes the polarization plane of light emitted from the liquid crystal element 51. Specifically, the liquid crystal layer 51c uses a liquid crystal element 51 in which a TN (Twisted Nematic) mode liquid crystal is sealed. When the output from the drive circuit 55 is 20 V, the phase of the laser light incident on the liquid crystal element 51 is modulated and is incident on the incident surface 15 a of the rod integrator 15.

When the output from the drive circuit 55 is 0 V, the laser light incident on the liquid crystal element 51 is transmitted through the liquid crystal element 51, so that the phase of the laser light is not modulated and is incident on the reflection mirror 17.
The switching frequency between the voltages 0V and 20V output from the drive circuit 55 is set to a frequency higher than the flicker frequency that can be detected by humans, for example, 30 Hz or more, preferably 60 Hz or more. Furthermore, the voltage change is preferably a random waveform (for example, a waveform generated from noise) rather than a waveform having a regular period. In this way, by using a random waveform, the random speckle pattern is time-integrated by the afterimage effect, so that it is possible to further suppress glare of the laser light emitted from the rod integrator 15.

Next, a method for illuminating the liquid crystal light valve 20 using the light source device 50 of the present embodiment having the above configuration will be described.
The laser light emitted from the laser light source 11 is incident on the rod integrator 15 with the green laser light whose wavelength is converted by the wavelength conversion element 13 as in the first embodiment.
On the other hand, the laser light reflected by the external resonator 14 and converted to green by passing through the wavelength conversion element 13 again is reflected by the dichroic mirror 12 and enters the liquid crystal element 51. When the applied voltage in the drive circuit 55 is 20 V, the phase of the laser light emitted from the liquid crystal element 51 does not change and enters the rod integrator 15. Further, when the applied voltage in the drive circuit 55 is 0 V, the phase of the laser light incident on the liquid crystal element 51 is modulated and incident on the rod integrator 15.
Here, when the applied voltage is 0V and when the applied voltage is 20V, the speckle patterns of the laser light emitted from the liquid crystal element 51 are different as shown in FIG. In the rod integrator 15, the speckle pattern is reduced because the speckle pattern when the applied voltage is 0 V and the speckle integrated when the applied voltage is 20 V are detected by the overlapping and overlapping eyes of the observer. Looks like.

  The light source device 50 according to the present embodiment has the same effects as the light source device 10 of the first embodiment. Furthermore, since the light source device 50 according to the present embodiment does not use a rotational drive system as in the prior art, the present invention does not deteriorate even when used for a long period of time, so that the reliability can be improved.

  In the present embodiment, the liquid crystal element 51 is provided in the first return path B1, but the liquid crystal element 51 may be provided in the second return path B2 as in the light source device 45 shown in FIG. 4 of the third embodiment. Even in this configuration, since the distance of the first return path B1 can be shortened, the entire apparatus can be reduced in size. Further, since a rod integrator having a smaller opening than the rod integrator 15 may be used, an inexpensive rod integrator 15 can be used.

Further, the optical member may be a refractive index changing means for changing the refractive index of the laser light traveling in the forward path A1 or the return path B3 with time. As the refractive index changing means, for example, PLZT (lead lanthanum zirconate titanate) that is an oxide ceramic containing lead (Pd), lanthanum (La), zircon (Zr), and titanium (Ti) may be used. PLZT is a material having an electro-optic effect (EO effect). When an electric field is applied to these crystals and ceramics, the refractive index changes. In this way, by changing the refractive index of PLZT, it is possible to give an optical path difference in time between the laser light traveling on the forward path A1 and the laser light traveling on the return path B3.
Therefore, since the optical path difference between the forward path A1 and the return path B3 can be temporally changed, it is possible to make it difficult to visually perceive glare due to coherence with a short optical path difference without making the optical path difference longer than the coherence length. It becomes.
In this embodiment, a TN mode liquid crystal is used, but a vertical mode liquid crystal may be used.

[Fifth Embodiment]
Next, a fifth embodiment according to the present invention will be described with reference to FIG.
In the present embodiment, a projector (image display device) 500 including the light source device 10 of the first embodiment will be described.

FIG. 7 is an explanatory diagram of a projector 500 including the light source device of the above embodiment.
The projector 500 includes light source devices 10R, 10G, and 10B, liquid crystal light valves 522, 523, and 524, a cross dichroic prism 525, and a projection lens (projection device) 526.

The projector 500 in FIG. 7 uses the light source device of the first embodiment as the green light source device 10G and the blue light source device 10B. The red light source device 10R includes only a laser light source, and emits laser light having a wavelength of 620 nm emitted from the laser light source without performing wavelength conversion. Note that the configurations and the like of the green light source device 10G and the blue light source device 10B have been described in the first embodiment, and thus detailed description thereof is omitted.
Further, rod integrators (optical elements: equalizing means) 15R, 15G, and 15B are provided in the subsequent stage (downstream side of the optical path) of the respective light source devices 10R, 10G, and 10B. Since these are the same as the rod integrator 15 described in the first embodiment, a detailed description thereof will be omitted.

  The light beam from the red light source device 10R is made uniform by the rod integrator 15R, then passes through the transmission lens 535R, is reflected by the reflection mirror 517, and enters the red light liquid crystal light valve 20R. Further, the light flux from the green light source device 10G is made uniform by the rod integrator 15G, then passes through the transfer lens 535G and enters the green light liquid crystal light valve 20G. The light beam from the blue light source device 10B is made uniform by the rod integrator 15B, then passes through the transmission lens 535B, is reflected by the reflection mirror 516, and enters the blue light liquid crystal light valve 20B. The transmission lenses 535R, G, and B are all for transmitting the image of the exit end face of the rod integrator 15R, G, and B to the image forming area of the liquid crystal light valve. In the present embodiment, the liquid crystal light valve is uniformly illuminated by the action of the rod integrators 15R, G, B and the transfer lenses 535R, G, B. The shape of the exit end face of the rod integrator 15R, G, B is the same as the image forming area of the liquid crystal light valve 20R, G, B, and the rod integrator 15R, G, B is the liquid crystal light valve 20R, G, B. The lenses 535R, G, and B can be omitted when they are arranged close to each other. In FIG. 7, the transmission lenses 535R, G, and B are illustrated as lenses having substantially the same shape, but the functions of the transmission lenses 535R, G, and B are the light sources 10R, G, and B and the liquid crystal light valves 20R, G. , B are optimized in accordance with the distance, etc., and therefore do not necessarily have the same shape.

Polarizers (not shown) are arranged on the incident side and the emission side of each liquid crystal light valve 20R, G, B. Of the light beams from the light source devices 10R, 10G, and 10B, only linearly polarized light in a predetermined direction passes through the incident side polarizing plate and enters each liquid crystal light valve. Since the laser light is basically light having a uniform polarization state (linearly polarized light), the incident-side polarizing plate can be omitted. However, there is a possibility that the polarization state is somewhat disturbed when passing through the optical elements such as the rod integrators 15R, G, B and the reflection mirrors 516, 517 before reaching the liquid crystal light valves 20R, G, B from the light source. There is. Therefore, it is possible to improve the contrast of the image by providing the incident side polarizing plate and aligning the polarization state.
Also, a polarization conversion means (not shown) is provided in front of the incident side polarizing plate or instead of the incident side polarizing plate so that the light incident on the liquid crystal light valves 20R, 20G, 20B is aligned with linearly polarized light. Also good. In this case, when the polarization conversion means is provided in front of the incident side polarizing plate, it is possible to reduce light loss due to light being absorbed or reflected by the incident side polarizing plate. Therefore, the light use efficiency can be improved. When a polarization conversion means is provided instead of the incident side polarizing plate, the contrast of the image can be improved as in the case of the incident side polarizing plate.

  The three color lights modulated by the liquid crystal light valves 20R, 20G, and 20B are incident on the cross dichroic prism 525. This prism is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged in a cross shape on the inner surface thereof. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the projection screen 527 by the projection lens 526 which is a projection optical system, and an enlarged image is displayed.

In the projector 500 of the present embodiment described above, the light emitted from the green light source device 10G and the blue light source device 10B is light in which the generation of speckle patterns is suppressed. The occurrence of interference fringes of the laser light projected onto the lens is also suppressed. Therefore, a good image can be displayed on the projection screen 527.
In the projector according to this embodiment, the green and blue light source devices 10G and B using the light source device 10 according to the first embodiment have been described. However, the red light source device 10R is also used as the light source device according to the first embodiment. 10 can be employed. Moreover, it is also possible to use the light source device of 2nd-4th embodiment (a modification is included) about light source device 10R, G, B. FIG.
Moreover, the light source device of 1st-4th embodiment (a modification is included) should just be applied to at least one among the light source devices 10R, G, and B. Furthermore, it is also possible to employ light source devices of different embodiments for each of the light source devices 10R, 10G, and B.

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 each of the above embodiments, the rod integrators 15, 31, and 46 are used as the optical elements. However, the present invention is not limited to this, and an optical fiber, a fly array lens, or the like may be used.
In the third and fourth embodiments, the glass 41 and the liquid crystal element 51 are provided in the return path B3. However, the difference between the laser light path between the laser light traveling in the forward path A1 and the light traveling in the return path B3 is provided in the forward path A1. May be greater than or equal to the distance at which interference between laser beams is reduced.
The optical element may be a transparent piezoelectric element. Also in this case, an optical path difference between the laser light traveling on the forward path A1 and the laser light traveling on the return path B3 occurs, so that the coherence of the laser light can be reduced.

Further, in each of the above embodiments, the rod integrator 15 or the like is used as the uniformizing means, but the present invention is not limited to this, and an optical fiber, a fly array lens, or the like may be used. Moreover, the optical element disposed between the light source device 10 and the like and the light modulation device 20 and the like is not limited to the uniformizing means, and may be another optical element such as a lens or a prism. In the above embodiment, the number of optical elements arranged between the light source device 10 and the like and the light modulation device 20 and the like is one (only uniformizing means), but two or more optical elements are arranged. You may make it do.
In the above-described embodiment, an example in which a transmissive liquid crystal light valve is used as the light modulation device has been described. However, the present invention can also be applied to a modulation device other than the liquid crystal light valve. Further, although there are a transmission type and a reflection type in the light modulation device, the present invention is applicable to any type.
Furthermore, in the fifth embodiment, an example of a projector using three light modulation devices has been described, but the present invention is also applicable to a projector using one, two, or four or more light modulation devices. Can do. As a projector, there are a front type that projects an image from the direction of observing the projection surface and a rear type that projects an image from the side opposite to the direction of observing the projection surface. It is also applicable to types.
In the fifth embodiment, the projector is described as an example of the image display device. However, the light source device of the present invention can be applied to an image display device other than the projector.

It is a top view which shows the light source device which concerns on 1st Embodiment of this invention. It is a top view which shows the light source device which concerns on 2nd Embodiment of this invention. It is a top view which shows the light source device which concerns on 3rd Embodiment of this invention. It is a top view which shows the modification of the light source device which concerns on 3rd Embodiment of this invention. It is a top view which shows the light source device which concerns on 4th Embodiment of this invention. It is a figure which shows the speckle pattern of the light inject | emitted from the liquid crystal element of the light source device of FIG. It is a top view which shows the image display apparatus provided with the light source device of this invention.

Explanation of symbols

  A1... Outward path (first optical path), B3... Return path (second optical path), C1... First outbound path (third optical path), C2... Second outbound path (fourth optical path), D1. , D2 ... second return path (sixth optical path), 10, 30, 40, 45, 50 ... light source device, 11, 11G, 11B ... laser light source, 12 ... dichroic mirror (separation unit), 13 ... wavelength conversion element, 14 ... external resonator, 15, 15R, 15G, 15B ... rod integrator (optical element), 17 ... reflecting mirror (reflecting part), 20 ... liquid crystal light valve (light modulation device), 26 ... rotating part (rotating means), 31 ... liquid crystal element (polarization rotating element: polarization conversion means), 32 ... half mirror (first branch part), 37 ... half mirror (second branch part), 41 ... retardation film (phase difference plate: polarization conversion means) 500 ... Projector (image display device), 526 ... Morphism lens (projection device)

Claims (6)

A laser light source;
A wavelength conversion element that converts the wavelength of light emitted from the laser light source into a predetermined wavelength;
An external resonator that transmits light that has been converted to the predetermined wavelength out of light emitted from the wavelength conversion element, reflects light that has not been converted to the predetermined wavelength, and returns the light toward the laser light source; With
A light source device that illuminates a light modulation device via an optical element with light emitted from the external resonator,
The light source is disposed between the laser light source and the wavelength conversion element, and passes through the wavelength conversion element in an optical path toward the laser light source among the light reflected by the external resonator. A separation unit that reflects the light converted into the wavelength of the laser and guides the light to a position different from the laser light source, and transmits the light that has not been converted into the predetermined wavelength toward the laser light source;
A reflection unit that reflects the light reflected by the separation unit toward the optical element;
Light that is emitted from the laser light source, passes through the external resonator, travels through a first optical path that is an optical path toward the optical element, and is emitted from the laser light source and reflected by the external resonator and passes through the separation unit. The light source device is characterized in that an optical path difference with light traveling on a second optical path which is an optical path of light reflected at the reflecting portion and traveling toward the optical element is equal to or greater than a distance at which interference between the laser beams is reduced. . A first branching section for branching light traveling in the first optical path into a third optical path and a fourth optical path;
A second branching part for branching light traveling in the second optical path into a fifth optical path and a sixth optical path;
The optical path difference between the light traveling on the third optical path and the laser light traveling on the fourth optical path, and the optical path difference between the laser light traveling on the fifth optical path and the laser light traveling on the sixth optical path are respectively lasers. The light source device according to claim 1, wherein the light source device is at least a distance at which interference between lights is reduced. A laser light source;
A wavelength conversion element that converts the wavelength of light emitted from the laser light source into a predetermined wavelength;
An external resonator that transmits light that has been converted to the predetermined wavelength out of light emitted from the wavelength conversion element, reflects light that has not been converted to the predetermined wavelength, and returns the light toward the laser light source; With
A light source device that illuminates a light modulation device via an optical element with light emitted from the external resonator,
The light source is disposed between the laser light source and the wavelength conversion element, and passes through the wavelength conversion element in an optical path toward the laser light source among the light reflected by the external resonator. A separation unit that reflects the light converted into the wavelength of the laser and guides the light to a position different from the laser light source, and transmits the light that has not been converted into the predetermined wavelength toward the laser light source;
A reflection unit that reflects the light reflected by the separation unit toward the optical element;
A first optical path, which is an optical path of light emitted from the laser light source and passing through the external resonator and traveling toward the optical element, or reflected from the laser light source and reflected by the external resonator and reflected through the separation unit A light source device comprising: an optical member having a refractive index different from that of air provided on a second optical path, which is an optical path of light that is reflected by the unit and travels toward the optical element.   The light source device according to claim 3, wherein the optical member is a phase changing unit that temporally changes the phase of light traveling in the first optical path or the second optical path.   The light source device according to claim 3, wherein the optical member is a refractive index changing unit that temporally changes a refractive index of light traveling in the first optical path or the second optical path. The light source device according to any one of claims 1 to 5,
A light modulation device that modulates light emitted from the light source device in accordance with an image signal;
An image display device comprising: a projection device that projects light modulated by the light modulation device.

Images