JP2008112623A - Light source device and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of a speckle pattern caused when projecting an image using light output from a light source device. <P>SOLUTION: Radiated light 300 radiated from a semiconductor laser device 20b enters into and penetrates through a triangular prism 240 and enters into a half mirror 250. A part of the radiated light 300 which entered into the half mirror 250 is reflected and the residue penetrates through the half mirror 250 and enters into a light guide part 150. The penetrating light 302 is reflected by a reflection surfaces 410, 420 and 430 to circulate in the light guide part 150 and enters into the half mirror 250 again. A part of the penetrating light 302 which entered into the half mirror 250 penetrates through the half mirror 250, and the residue circulates in the light guide part 150 and enters into the half mirror 250 again. Thus, the light having the optical path difference longer than the coherent length and various optical path difference differing according to the number of times of circulation in the light guide part, thereby suppressing generation of a speckle pattern. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a light source device and a projector including the light source device.

  2. Description of the Related Art Projectors that display images by irradiating spatial light modulation devices such as light valves and digital mirror devices (DMD) with illumination light from a light source device are used. The projector includes a front projection type projector that projects from the front of the screen and a rear projection type projector that projects from the rear of the screen.

  For example, a front projection type projector and a rear projection type projector use a laser light source as a light source device. The laser light source has an advantage of higher energy efficiency and color reproducibility than the lamp light source.

JP 7-297111 A Japanese Patent Laid-Open No. 60-230629 JP 2000-199872 A JP 2001-296503 A Japanese National Patent Publication No. 5-196869

  However, when the phases of the light beams emitted from the light source device are aligned as in the case of a laser light source, neighboring light beams interfere with each other when projected onto the screen, so that interference fringes called speckle patterns are formed in the space in front of the screen. And spots appear. The viewer sees a double image of the screen surface and the speckle pattern, and tries to focus on each of the screen surface and the speckle pattern. The problem of increased fatigue can occur.

  The above-mentioned problems often occur particularly with laser beams having the same phase, but may also occur with a lamp light source such as an ultrahigh pressure mercury lamp. Therefore, in a projector using a light source device, it is desired to suppress the generation of speckle patterns.

  The present application has been made in view of such a problem, and an object thereof is to suppress generation of a speckle pattern generated when an image is projected by light output from a light source device.

In order to solve at least a part of the problems described above, a first aspect of the present invention provides a light source device. The light source device of the first aspect is
A light emitting means for emitting light;
A branching means for reflecting a part of the incident light and transmitting the rest,
A light guiding means for circulating incident light incident through the branching means and making the light incident on the branching means again.
The branching unit outputs a part of incident light which is emitted from the light emitting unit and enters through the light guiding unit as first reflected light toward the irradiation surface, and the rest is the first transmitted light. The incident surface is incident on the light guide means, and a part of the incident light from the light guide means is incident again on the light guide means as second reflected light, and the remaining light is incident on the irradiation surface as second transmitted light. The output is output to

  According to the above-described aspect, a part of the light emitted from the light emitting means can be reflected, and the other part can be circulated in the light guiding means to output the reflected light and the circulated light. A plurality of types of light having different optical path lengths can be output toward the same irradiation surface. Therefore, according to the sequel apparatus of the above-mentioned aspect, light with low coherence can be output, and speckle patterns generated when light is irradiated onto the irradiation surface can be reduced.

In the light source device of the first aspect,
The light guiding unit may be configured such that an optical path length until incident light from the branching unit again enters the branching unit is equal to or longer than a coherent distance of light emitted from the light emitting unit. .

  According to the above-described aspect, an optical path longer than the coherence distance of the emitted light can be given to the incident light to the light guide unit. Therefore, also in the above-described aspect, the light source device can output a plurality of types of light having an optical path difference equal to or greater than the coherence distance, and can reduce speckle patterns generated when the irradiation surface is irradiated.

In the light source device of the first aspect,
The light guiding means may have a plurality of reflecting surfaces, and circulate the incident light by reflecting the light with the plurality of reflecting surfaces.

  According to the above-described aspect, since light can be circulated inside the light guide unit by repeating reflection, a plurality of types of light having different optical path lengths can be output with a simple configuration. Accordingly, it is possible to output light with low coherence and suppress the generation of speckle patterns.

In the light source device of the first aspect,
The light guide means includes four triangular prisms whose bottom surface is a right triangle, and of the four triangular prisms, the side surface including the hypotenuse of the bottom surface of the three triangular prisms is the reflective surface. And the side surface including the hypotenuse of the bottom surface of the remaining one of the four triangular prisms is disposed to face the light emitting means.
The branching unit may be arranged so as to contact a side surface including a hypotenuse of the bottom surface of the remaining one triangular prism.

  Since the triangular prism can be easily prepared, according to the above aspect, the light source device can be manufactured easily and at low cost.

In the light source device of the first aspect,
The triangular prism is formed of a member that has a refractive index substantially the same as the refractive index of the member that transmits light and is in contact with the branching unit between the branching unit and the light emitting unit. You may provide the 1st permeation | transmission member.

  According to the above-described aspect, the triangular prism can be disposed on one side of the branching unit, and the transmission member having substantially the same refractive index as that of the triangular prism can be disposed on the other side. Therefore, since the incident angle of the incident light to the branching unit and the incident angle of the incident light from the branching unit to the light guiding unit can be made substantially the same angle, the light can be circulated stably in the light guiding unit. . Therefore, the light source device of the above-described aspect can output light with low coherence toward the irradiation target surface, and can suppress generation of speckle patterns.

In the light source device of the first aspect,
The first transmitting member may be a triangular prism having substantially the same shape and size as the four triangular prisms, and may be disposed so that a side surface including a hypotenuse of a bottom surface is in contact with the branching unit.

  According to the light source device of the above-described aspect, the triangular prism of the light guiding unit and the triangular prism as the first transmission member are substantially the same type of triangular prism, and the same surface of each triangular prism is in contact with both sides of the branching unit. Can be arranged as follows. Therefore, according to the above-described aspect, it is possible to easily manufacture a light source device that can output light with low coherence toward the irradiation target surface.

In the light source device of the first aspect,
An arbitrary first triangular prism of the four triangular prisms and a second triangular prism adjacent to the first triangular prism include a first side surface including opposite sides of a right triangle on the bottom surface of the first triangular prism. And a side surface including the opposite side of a right triangle on the bottom surface of the second triangular prism, the first triangular prism, and the second triangular prism adjacent to the first triangular prism, Different third triangular prisms include a second side surface including a right triangle adjacent to the bottom surface of the first triangular prism, and a side surface including a right triangle adjacent side to the bottom surface of the third triangular prism. And the apexes between the opposite sides of the right triangles on the bottom surfaces of all the triangular prisms and the adjacent sides may coincide with each other.

  According to the above-described aspect, each triangular prism constituting the light guide means is joined to the adjacent triangular prism on the side surface including the opposite side of the bottom surface, so that the stability of the structure of the light guide means can be improved. Moreover, according to the above-mentioned aspect, since the light guide means can be formed by joining the side surfaces of the respective triangular prisms, the light guide means can be easily manufactured. Moreover, the side surface including the side which is not the hypotenuse of the triangular prism can be used as a reflection surface inside the light guide means. Therefore, by using the light source device of the above aspect, the generation of stray light in the light guide means can be suppressed, and the light use efficiency can be improved.

In the light source device of the first aspect,
The shape of the bottom surface of each triangular prism may be a right-angled isosceles triangle.

  According to the above aspect, the stability of the structure of the light guide means can be improved. In addition, by using a triangular prism having a bottom surface in the shape of a right isosceles triangle, light output to the irradiation surface after circulating in the light guide means and output to the irradiation surface without circulating in the light guide means Since light can be output at substantially the same angle, it is possible to suppress a decrease in light utilization efficiency.

In the light source device of the first aspect,
Arbitrary first triangular prism among the four triangular prisms, a second triangular prism adjacent to the first triangular prism, an adjacent first triangular prism, and the first triangular prism A first triangular prism having a third triangular prism different from the prism, and a fourth triangular prism adjacent to the third triangular prism and different from the second triangular prism. , The second triangular prism, the third triangular prism, and the fourth triangular prism include at least an interval between the first triangular prism and the second triangular prism, and the third triangular prism and the The intervals between the fourth triangular prisms may be substantially equal.

  According to the light source device of the above aspect, a gap can be formed between the first triangular prism and the second triangular prism, and between the third triangular prism and the fourth triangular prism, and the distance of the gap is adjusted. Thereby, the optical path length of the light circulating in the light guide means can be arbitrarily adjusted.

In the light source device of the first aspect,
A second transmitting member that is disposed between the first triangular prism and the second triangular prism and between the third triangular prism and the fourth triangular prism and that transmits light; Good.

  According to the light source device of the above-described aspect, it is possible to dispose a transmission member in the gap between the first triangular prism and the second triangular prism and between the third triangular prism and the fourth triangular prism. Therefore, the stability of the structure of the light guide means can be improved, and an arbitrary optical path difference can be given to the optical path length of the incident light with respect to the first reflected light.

In the light source device of the first aspect,
The second transmission member may include a rod integrator.

  According to the light source device of the above aspect, even when the reflection angle of the reflected light reflected by the reflecting surface of the triangular prism deviates from a desired angle, the reflected light is reflected in the rod integrator and adjacent to the triangular prism. Is incident on. Therefore, according to the above aspect, the optical path length of the incident light can be arbitrarily set while suppressing the loss of the incident light.

In the light source device of the first aspect,
At least one refractive index variable element that is arranged in an optical path inside the light guide means of the emitted light and whose refractive index changes according to a change in a predetermined condition;
And a condition changing means for changing the predetermined condition.

  The optical path length of the light passing through the light guide means changes according to the change in the refractive index of the refractive index variable element arranged inside the light guide means. Therefore, according to the light source device of the above-described aspect, since light having various optical path lengths can be output from the same surface, light with low coherence can be output.

In the light source device of the first aspect,
The predetermined condition may include at least one of a magnetic field and an electric field at a portion where the refractive index variable element is disposed, and a temperature and stress applied to the refractive index variable element.

  According to the light source device of the above aspect, since the refractive index can be easily changed, light with low coherence can be easily output.

  As a second aspect, a projector is provided. The projector according to the second aspect includes the light source device according to any one of the first aspect.

  According to the projector of the above-described aspect, since an image can be formed using the combined light obtained by combining light of a plurality of types of optical path lengths and projected onto the screen, generation of speckle noise can be reduced. Therefore, the discomfort of the viewer who views the image projected on the screen can be eliminated, and the viewer's fatigue can be reduced.

  In the present invention, the various aspects described above can be appropriately combined or partially omitted.

A1. System configuration:
In the first embodiment, a front projection type projector will be described. FIG. 1 is an explanatory diagram illustrating a schematic configuration of a front projection type projector 10 in the first embodiment. The front projection type projector 10 uses a semiconductor laser device 20a that emits red light, a semiconductor laser device 20b that emits blue light, a semiconductor laser device 20c that emits green light, and a liquid crystal panel dedicated to each color. And is projected onto a screen 50 as shown in FIG. Hereinafter, in the first embodiment, the front projection type projector 10 is simply referred to as the projector 10.

  As shown in FIG. 1, the projector 10 includes a semiconductor laser device 20, an optical circulation unit 100, integrator lenses 21 a to 21 c (illumination optical system), light valves 37 to 39, a dichroic prism 40, and a projection lens 41. Hereinafter, in the first embodiment, the semiconductor laser device 20a and the optical circulation unit 100 are collectively referred to as the light source device 11. Similarly, the laser device 20b and the light circulation unit 100 are collectively referred to as a light source device 11, and the semiconductor laser light source 20c and the light circulation unit 100 are collectively referred to as a light source device 11.

  Each of the semiconductor laser devices 20a to 20c includes a second harmonic generation element and a resonator (not shown), and converts light from a light source (not shown) into “laser light” using the second harmonic generation element and the resonator. And output. The semiconductor laser devices 20 a to 20 c output laser beams having the same wavelength and phase for each semiconductor laser device, and function as a light source for the projector 10. For example, the semiconductor laser device 20a outputs red laser light having a wavelength of about 650 nm, the semiconductor laser device 20b outputs green laser light having a wavelength of about 540 nm, and the semiconductor laser device 20c is blue having a wavelength of about 430 nm. Outputs laser light.

  The semiconductor laser devices 20a to 20c are also provided with a high-frequency superposition mechanism (not shown). The high-frequency superposition mechanism performs optical modulation by applying a high-frequency signal from the outside to the bias current of the laser diode. It is known that laser beams having the same phase have higher coherence than lamp light sources, but light that has passed through a predetermined optical path difference does not interfere with each other. An optical path difference that does not cause interference is called “coherent length”. Although the coherent length of laser light is several meters or more, the coherent length can be shortened to several millimeters by performing modulation using a high-frequency superposition mechanism.

  The optical circulation unit 100 circulates incident light inside and outputs it as light having an optical path length corresponding to the number of circulations. Therefore, the light output from the optical circulation unit 100 includes light having a plurality of types of optical path lengths, and the combined light of the output light becomes light with low coherence. By using the combined light with low coherence output in this way, the interference of light can be suppressed, so that the generation of speckle patterns can be reduced and the viewer's fatigue and discomfort can be reduced. The optical circulation unit 100 will be described in detail later.

  The integrator lens 21 superimposes incident irradiation light to average out luminance unevenness, and reduces the light amount difference between the end portion and the center portion of the screen. By arranging the integrator lens 21, a bright image can be projected on the entire screen.

  The light valves 37 to 39 are formed using high-temperature polysilicon (HTPS: High Temperature Poly-Silicon) TFTs. It has an active matrix drive type transmissive liquid crystal panel and a polarizing plate. The light valves 37 to 39 draw an image by controlling incident light.

  The dichroic prism 40 has a rectangular parallelepiped structure by combining four triangular prisms, and forms an image by combining the red laser light, the green laser light, and the blue laser light that have passed through the light valves 37 to 39. And projected onto the projection lens 41.

  The projection lens 41 projects the image projected from the dichroic prism 40 onto the screen 50.

  As described above, the projector 10 causes the light emitted from the semiconductor laser devices 20 a to 20 c to enter the light valves dedicated to the respective colors to form an image, and then synthesize and project the image onto the screen 50. The viewer visually recognizes the image projected on the screen 50.

A2. Detailed configuration of the optical circulation unit:
The detailed configuration of the optical circulation unit will be described with reference to FIG. 2 and FIG. It is explanatory drawing which illustrates the detailed structure of the optical circulation unit 100 in 1st Example. FIG. 3 is an explanatory diagram for explaining the assembly of the optical circulation unit 100 in the first embodiment. As shown in FIG. 2, the light circulation unit 100 includes a light guide unit 150 including a triangular prism 200, 210, 220, 230, a half mirror 250, and a triangular prism 240.

  Each of the triangular prisms 200 to 230 forming the light guide unit 150 is a triangular prism having three rectangular surfaces and two triangular surfaces. Hereinafter, the triangular surface is referred to as a bottom surface, and the rectangular surface is referred to as a side surface. Each of the triangular prisms 200 to 230 has a bottom surface that is a right isosceles triangle, has substantially the same size and shape, and is formed of a member that transmits light. In the first embodiment, each triangular prism is made of glass. The side surfaces including the hypotenuses of isosceles triangles that form the bottom surfaces of the triangular prisms 210, 220, and 230 function as reflecting surfaces 410, 420, and 430, respectively. In this specification, the descriptions “almost ~” and “about ~” are included in the range of error due to deterioration due to manufacturing process or use, and the range of error is, for example, about ± 5%. Indicates that there is no effect on the function and effect.

  The half mirror 250 is formed of a silver thin film deposited on the side surface including the oblique side of the bottom surface of the triangular prism 200. The half mirror 250 reflects part of the incident light and transmits the other part of the incident light. In the first embodiment, the reflectance: transmittance is about “1: 1”. That is, the half mirror 250 reflects about 50% of the incident light on the half mirror 250 and transmits about 50% of the incident light. The remaining incident light that is neither reflected nor transmitted is scattered or absorbed by the half mirror 250.

  The half mirror 250 has an angle of about 45 degrees with respect to a plane perpendicular to the light emitted from the semiconductor laser device 20b, and an angle of about 45 degrees with respect to the light receiving surface of the integrator lens 21. Is arranged. By doing so, it is possible to improve the irradiation efficiency per unit area of the integrator lens 21 of the light emitted from the semiconductor laser device 20b and output toward the integrator lens 21 via the half mirror 250.

  The triangular prism 240 is formed of the same medium (that is, has the same refractive index) as the triangular prism 200, and is disposed between the half mirror 250 and the semiconductor laser device 20b so as to be in contact with the half mirror 250. . With this configuration, the incident angle of light incident on the half mirror 250 and the incident angle of light incident on the triangular prism 200 from the half mirror 250 can be made substantially the same. Therefore, light can be incident on the triangular prism 200 at a desired incident angle, and light can be circulated stably in the light circulation unit 100.

  Here, the assembly of the optical circulation unit 100 will be described with reference to FIG. FIG. 3 is an exploded plan view of the light circulation unit 100 as viewed from the bottom side of the triangular prism. As shown in FIG. 3, the triangular prisms 200 to 230 are integrally formed by bonding a side surface including the opposite side of the right triangle forming the bottom surface and a side surface including the adjacent side of the bottom surface of the adjacent triangular prism. ing. Specifically, for example, one opposite side 201 of the triangular prism 200 is bonded to a side surface including the adjacent side 212 of the triangular prism 210, and the adjacent side 202 of the triangular prism 200 is opposite to the triangular prism 210. It is bonded to the side surface including the opposite side 232 of the adjacent triangular prism 230.

  The silver thin film 250 functioning as the half mirror 250 is deposited on the side surface including the hypotenuse 203 on the bottom surface of the triangular prism 200.

  The triangular prism 240 is bonded to the half mirror 250 on the side surface including the oblique side 243 of the triangular prism 240 so that the side surface including the oblique side 203 of the triangular prism 200 and the side surface including the oblique side 243 of the triangular prism 240 overlap.

  In the first embodiment, the triangular prisms or the triangular prism and the half mirror 250 are joined together by an adhesive having a refractive index lower than that of the triangular prism. In this way, the incident angle of light to the adhesive and the incident angle of light from the adhesive to the triangular prism are substantially the same, so that the light incident on the optical circulation unit 100 is stabilized in the optical circulation unit 100. Can be circulated. Moreover, the side surface including the side which is not the hypotenuse of the triangular prism can be used as a reflection surface inside the light guide means. Therefore, generation | occurrence | production of the stray light in a light guide part can be suppressed, and the utilization efficiency of light can be improved.

  Returning to FIG. 2, the light circulation in the light circulation unit 100 will be described. In this embodiment, as shown in FIG. 2, the lengths of the opposite sides and the adjacent sides of the triangular prisms 200 to 240 are “L”. In this embodiment, the refractive index of the triangular prisms 200 to 240 is represented as “n”.

  As shown in FIG. 2, the emitted light 300 emitted from the semiconductor laser device 20 b is incident substantially perpendicular to the side surface of the triangular prism 240, passes through the triangular prism 240, and enters the half mirror 250.

  About 50% of the emitted light 300 (broken line) incident on the half mirror 250 is reflected (reflected light 301: broken line) and is incident on the integrator lens 21, and the remaining 50% of the emitted light 300 passes through the half mirror 250. The light passes through (transmitted light 302: one-dot chain line) and enters the triangular prism 200.

  The transmitted light 302 is reflected by the reflecting surface 410 of the triangular prism 210 and enters the triangular prism 220. Generally, the critical angle of the boundary surface between glass and air, which is a medium forming the triangular prism, is about 41 °, and light incident on the boundary surface between glass and air at an angle larger than the critical angle is totally reflected. The As shown in FIG. 2, the transmitted light 302 is incident on the triangular prism 210 substantially perpendicular to the side surface including the opposite side of the triangular prism 210, so that the transmitted light 302 is incident on the reflecting surface 410 at an incident angle of about 45 °. To do. Therefore, the transmitted light 302 is totally reflected by the reflecting surface 410 and enters the reflecting surface 420 of the triangular prism 220, and is totally reflected by the reflecting surface 420 of the triangular prism 220 and the reflecting surface 430 of the triangular prism 230 in the same manner as the reflecting surface 410. The light is reflected, circulates in the light guide unit 150, and enters the half mirror 250 again from the inside of the light guide unit 150.

  About 50% of the transmitted light 302 incident on the half mirror 250 is transmitted through the half mirror 250 (transmitted light 303: one-dot chain line) and enters the integrator lens 21, and the remaining approximately 50% of the transmitted light 302 is formed by the triangular prism 210. Are reflected toward the reflecting surface 410 (reflected light 304: two-dot chain line). Similar to the transmitted light 302, the reflected light 304 is totally reflected by the reflection surfaces 410, 420, and 430, circulates in the light guide unit 150, and enters the half mirror 250 again.

  About 50% of the reflected light 304 incident on the half mirror 250 passes through the half mirror 250 (transmitted light 305: two-dot chain line) and enters the integrator lens 21, and the remaining about 50% of the reflected light 304 is a triangular prism. The light is reflected toward the reflection surface 410 of 210 (reflected light 306: fine chain line). Similar to the reflected light 304, the reflected light 306 circulates in the light guide unit 150 and enters the half mirror 250 again, and is reflected and transmitted. Thereafter, similarly, the light reflected by the half mirror 250 and incident on the light guide unit 150 circulates in the light guide unit 150 and is reflected and transmitted by the half mirror 250.

  As shown in FIG. 2, the optical path length of one circulation in the light guide unit 150 is “d”. The optical path length “d” can be expressed as approximately “2L * n”. In the first embodiment, the light guide unit 150 is formed so that the optical path length “d” is longer than the coherent length. That is, the optical circulation unit 100 outputs a plurality of types of light having optical path differences equal to or greater than the coherent length from the same surface (half mirror 250) to the same irradiation surface (integrator lens 21). Specifically, the optical path length of the transmitted light 303 is longer by the optical path difference “d” than the optical path length of the reflected light 301, and the optical path length of the transmitted light 305 is “2d” (ie, the optical path difference of the reflected light 301 is larger). The optical path difference “d”) is longer than the optical path length of the transmitted light 303.

  A plurality of types of light (reflected light 301, transmitted light 303, 305) incident on the integrator lens 21 are combined by the integrator lens 21 so that the variation in the amount of light within the irradiation surface is flat and incident on the light valve 38. To do. Since the reflected light 301 and the transmitted light 303 and 305 incident on the integrator lens 21 are light having an optical path difference equal to or greater than the coherent length, the combined light of the reflected light 301 and the transmitted lights 303 and 305 synthesized by the integrator lens 21. Becomes light with low coherence.

  The projector 10 projects an image on the screen using the light having low coherence recombined in this way.

  According to the projector 10 of the first embodiment described above, the highly coherent laser light emitted from the semiconductor laser device is branched by the optical circulation unit 100 into a plurality of lights having an optical path difference equal to or greater than the coherent length, and the integrator Laser light with low coherence can be output by being superimposed by the lens 21. Conventionally, sound and vibration are generated because a method such as vibrating the screen to reduce the speckle pattern has been generated. However, according to the projector 10 of the first embodiment, laser light with low coherence is emitted. Since the image can be projected onto the screen by using it, the generation of speckle patterns can be reduced while reducing the generation of sound and vibration. Accordingly, the screen viewer can comfortably appreciate the image projected on the screen, and can reduce the viewer's discomfort and increase the viewer's fatigue.

  Further, according to the projector 10 of the first embodiment, since the light guide unit 150 can be formed by bonding triangular prisms, the light guide unit can be formed easily and at low cost.

B. Second embodiment:
In the second embodiment, an optical circulation unit provided with a refractive index variable element whose refractive index changes according to a change in a predetermined condition in the light guide unit will be described.

B1. Detailed configuration of the optical circulation unit:
FIG. 4 is an explanatory diagram for explaining a light source device according to the second embodiment. The light source device 11a of the second embodiment is as shown in FIG. An optical circulation unit 110 and a semiconductor laser device 20b including a light guide unit 150, a half mirror 250, a refractive index varying unit 500 are provided. The light guide unit 150 includes four triangular prisms 200, 210, 220, and 230, as in the first embodiment. The triangular prisms 200, 210, 220, 230, 240, the half mirror 250, and the semiconductor laser device 20b have the same functions and configurations as those of the first embodiment, and thus the description thereof is omitted.

  The refractive index varying means 500 includes a refractive index varying element 510 and electrode sheets 520 and 530. As shown in FIG. 4, the refractive index variable element 510 is disposed between the side surfaces of the triangular prism 200 and the triangular prism 230. The electrode sheets 520 and 530 are disposed on both sides of the refractive index variable element 510.

  The refractive index variable element is an element whose refractive index changes according to a change in a predetermined condition. Examples of the predetermined condition include an electric field or a magnetic field in which the refractive index variable element is placed, temperature and stress applied to the refractive index variable element. The refractive index variable element is a material whose refractive index changes due to the change of the electron spin polarization or electron orbital motion due to the magneto-optic effect due to the change of the magnetic field, or the molecular orientation due to the electro-optic effect due to the change of the electric field. It can be formed using a substance that changes and changes its refractive index. The refractive index variable element can be formed using a material whose refractive index changes by changing the density of ions and electrons when stress is applied, for example.

  In this embodiment, the refractive index variable element 510 is a liquid crystal layer which is formed in a thin film shape and whose refractive index changes due to a change in electric field. In the refractive index variable element 510, the orientation of the liquid crystal molecules constituting the refractive index variable element changes due to the change in the electric field at the position where the refractive index variable element 510 is arranged, and the refractive index changes. Therefore, the refractive index of the refractive index variable element 510 can be changed by applying a voltage between the electrode sheets 520 and 530.

  The optical path length of light passing through the refractive index variable element 510 can be expressed as “d1 × n ′” where the layer thickness of the refractive index variable element 510 is “d1” and the refractive index n ′. That is, the optical path length of the light passing through the refractive index variable element 510 can be set flexibly by changing the refractive index n ′.

  According to the light source device of the second embodiment described above, since the refractive index of the refractive index variable element can be changed by changing the electric field by applying a voltage between the electrode sheets, the light passing through the light guide portion can be changed. The optical path length can be variously changed at a desired timing. Therefore, a plurality of types of light having different optical path lengths can be output from the optical circulation unit 110. Therefore, by using a projector including the light source device of the second embodiment, the generation of speckle patterns is suppressed, and viewer discomfort and viewer fatigue can be reduced.

  In addition, according to the optical circulation unit of the second embodiment described above, the coherent length is increased by increasing the refractive index of the refractive index variable element 510. A short distance, that is, the optical circulation unit can be miniaturized.

C. Third embodiment:
In the third embodiment, a light source device having an optical circulation unit in which a rod integrator is disposed between adjacent triangular prisms will be described.

C1. Detailed configuration of the optical circulation unit:
FIG. 5 is an explanatory diagram illustrating the light source device in the third embodiment. FIG. 5 is a plan view of the light source device 11b from the bottom surface side of the light circulation unit 120. FIG. As shown in FIG. 5, the light source device 11b includes an optical circulation unit 120 including a light guide unit 150a, a half mirror 250, and a triangular prism 240, and a semiconductor laser device 20b. The light guide unit 150 a includes triangular prisms 200 to 230 and rod integrators 600 and 601. Since the semiconductor laser device 20b, the triangular prisms 200 to 240, and the half mirror 250 have the same functions and structures as those of the first embodiment, description thereof is omitted.

  As shown in FIG. 5, in the light guide unit 150 a, the rod integrator 600 is disposed between the triangular prism 210 and the triangular prism 220, and the rod integrator 610 is disposed between the triangular prism 230 and the triangular prism 200. . The rod integrators 600 and 610 are formed of the same medium as the triangular prism. In this embodiment, both the triangular prism and the rod integrator are made of transparent glass.

  In the present embodiment, the distance between the triangular prism 210 and the triangular prism 220, in other words, the distance between the opposing side surfaces, that is, the length of the rod integrator 600, and the distance between the triangular prism 230 and the triangular prism 200, in other words. The distance between the opposing side surfaces of the triangular prism 230 and the triangular prism 200 (the length of the rod integrator 610) is substantially equal. In addition, the optical path length of the light that circulates once through the light guide unit 150a is expressed as “d2”. In this embodiment, the optical path length “d2” is configured to be longer than the coherent length.

  As shown in FIG. 5, in the emitted light emitted from the semiconductor laser device 20b, about 50% of the emitted light 700 is reflected by the half mirror 250 toward an integrator lens (not shown) (reflected light 701), and the emitted light is emitted. About 50% of 700 passes through the half mirror 250 and enters the light guide unit 150a (transmitted light 702). The transmitted light 702 is reflected by the reflecting surface 410 of the triangular prism 210, passes through the rod integrator 600, is reflected by the reflecting surface 420 of the triangular prism 220, and the reflecting surface 430 of the triangular prism 230, passes through the rod integrator 610, and is again a half mirror. Incident at 250. About 50% of the transmitted light 702 incident on the half mirror 250 is transmitted through the half mirror 250 toward the integrator lens (not shown) (transmitted light 703), and about 50% is reflected by the half mirror 250 (reflected light 704) again. It circulates through the light guide 150a.

  The transmitted light 703 has an optical path length “d2” longer than the reflected light 701. Therefore, a plurality of types of light having optical path differences equal to or greater than the coherent length are output from the half mirror 250 toward the integrator lens (not shown).

  According to the light source device of the third embodiment described above, the optical path length can be easily extended by arranging the rod integrator between the triangular prisms. Further, according to the light source device of the third embodiment, the optical path length can be extended by arranging the rod integrator in a direction substantially perpendicular to the traveling direction of the light emitted from the semiconductor laser device 20b. For this reason, the light source device of the third embodiment has an optical path length equal to or greater than the coherent length, similar to the light guide unit in which four triangular prisms are bonded, and is large in the traveling direction of the light emitted from the semiconductor laser device 20b. This can be made smaller than the light guide unit in which four triangular prisms are bonded.

  Further, according to the light source device of the third embodiment described above, the reflected light 705 is generated from the light guide unit as shown in FIG. 5 due to deterioration or damage of the reflection surfaces 410 to 430 of the half mirror 250 and the triangular prisms. Even when traveling outward, the reflected light 705 can be reflected by the rod integrator and advanced toward the next triangular prism. Therefore, loss of light can be suppressed.

D. Fourth embodiment:
In the fourth embodiment, a light source device including an optical circulation unit having a light guide unit constituted by four triangular prisms arranged at a predetermined distance will be described.

D1. Detailed configuration of the optical circulation unit:
FIG. 6 is an explanatory diagram illustrating the light source device 11c of the fourth embodiment. FIG. 6 is a plan view from the bottom side of the light source device 11c. As shown in FIG. 6, the light source device 11c includes an optical circulation unit 130 and a semiconductor laser device 20b. The optical circulation unit 130 includes a light guide unit 150b including four triangular prisms 200 to 230, a half mirror 250, and a triangular prism 240. The optical circulation unit 130 includes a triangular prism 200 and a triangular prism 210, a triangular prism 210 and a triangular prism 220, a triangular prism 220 and a triangular prism 230, and a triangular prism 230 and a triangular prism 200. It is comprised so that it may have the space | gap 800-830 in between. Each of the triangular prisms 200 to 230 is arranged such that the distance between the gap 800 and the gap 820 is substantially equal and the distance between the gap 810 and the gap 830 is substantially equal.

  As shown in FIG. 6, about 50% of the emitted light 710 emitted from the semiconductor laser device 20b is reflected by the half mirror 250 toward an integrator lens (not shown) (reflected light 711), and the emitted light is emitted. About 50% of 700 passes through the half mirror 250 and enters the light guide portion 150b (transmitted light 712). The transmitted light 712 passes through the gap 800 and is reflected by the reflecting surface 410 of the triangular prism 210, passes through the gap 810, and is reflected by the reflecting surface 420 of the triangular prism 220. The transmitted light 712 passes through the gap 820 and is reflected by the reflecting surface 430 of the triangular prism 230, passes through the gap 830, and enters the half mirror 250 again. About 50% of the transmitted light 712 incident on the half mirror 250 is transmitted through the half mirror 250 toward an integrator lens (not shown) (transmitted light 713), and about 50% is reflected by the half mirror 250 (reflected light 714) again. It circulates through the light guide 150b. Thereafter, circulation in the light guide unit and reflection and transmission by the half mirror 250 are repeated, and light having different optical path lengths is output from the half mirror 250.

  The transmitted light 713 has an optical path length “d3” longer than the reflected light 711. In the present embodiment, the light guide unit 150b is configured such that the optical path length “d3” is longer than the coherent length. Therefore, a plurality of types of light having optical path differences equal to or greater than the coherent length are output from the half mirror 250 toward the integrator lens (not shown).

  According to the fourth embodiment described above, the optical path length of the light passing through the light guide can be flexibly set by adjusting the arrangement of the plurality of triangular prisms.

E. Variation:
(1) In the first to fourth embodiments described above, the light guide unit is configured using a plurality of triangular prisms. For example, as shown in FIG. 7, the light guide unit is configured using an optical fiber. May be formed.

  FIG. 7 is an explanatory diagram illustrating a schematic configuration of a light source device according to a modification. The modified light source device 11 d includes a semiconductor laser device 20 b and an optical circulation unit 140. The optical circulation unit 140 includes a light guide unit 150c including a triangular prism 200 and an optical fiber 900, a half mirror 250, and a triangular prism 240.

  The optical fiber 900 is formed in a thin fiber shape with quartz glass or plastic, and has a double structure in which the periphery of the core at the center is covered with a clad. Since the optical fiber 900 is formed so that the core has a higher refractive index than the clad, the incident light to the optical fiber 900 is totally reflected at the boundary between the core and the clad and confined in the core. Propagate in the state. The optical fiber 900 is formed so that the optical path length of the light passing through the optical fiber 900 is at least longer than the coherent length of the emitted light emitted from the semiconductor laser device 20b.

  As shown in FIG. 7, about 50% of the emitted light emitted from the semiconductor laser device 20b is reflected by the half mirror 250 toward an integrator lens (not shown) (reflected light 951), and about 50% of the emitted light 950 is obtained. Transmits through the half mirror 250 and enters the light guide portion 150c (transmitted light 952). The transmitted light 952 propagates while being totally reflected in the optical fiber 900 and enters the half mirror 250 again. About 50% of the transmitted light 952 incident on the half mirror 250 is transmitted through the half mirror 250 toward an integrator lens (not shown) (transmitted light 953), and about 50% of the transmitted light 952 is reflected by the half mirror 250 (reflected light). 954) The light guide 150c is circulated again. In this manner, the light source device 11d repeats reflection and transmission at the half mirror 250 and circulation in the light guide unit 150c with respect to incident light, and outputs light having different optical path lengths toward an integrator lens (not shown). .

  According to the above-described modification, light can be circulated with a simple configuration by using an optical fiber. Therefore, according to the light source device of the modified example, since it is possible to output a plurality of types of light having optical path differences that are equal to or greater than the coherent length, the generation of speckle patterns can be suppressed.

(2) In the first embodiment described above, the light source device is employed in a projector having a configuration called a three-plate system using three spatial modulators (light valves), but two light sources using two spatial modulators are used. You may employ | adopt for the projector of the structure called the board system and the single board system using one spatial modulator. When the light source device described above is employed in a two-plate type or single-plate type projector, it can be configured by using a dichroic mirror, a reflection lens, or the like as appropriate.

(3) In each of the above-described embodiments, the half mirror 250 with the transmittance adjusted to about 50% and the reflectance adjusted to about 50% is used. For example, the transmittance and the reflectance are arbitrarily adjusted. A partial reflection mirror may be used.

(4) In each of the embodiments described above, the optical circulation unit is configured so that a plurality of types of light output from the light source device have optical path differences that are equal to or greater than the coherent length. The types of light may not have an optical path difference equal to or greater than the coherent length. If a plurality of types of light output from the light source device have different optical path lengths, the generation of speckle patterns is reduced.

(5) In each of the above-described embodiments, the light guide is formed using a triangular prism. However, for example, the light guide may be formed using a prismatic transparent member.

(6) In the second embodiment described above, the refractive index variable element 510 is disposed between the triangular prism 230 and the triangular prism 200. For example, as shown in FIG. It may be arranged at a position (refractive index variable elements 511, 512, 513). A plurality of refractive index variable elements may be arranged. In this way, the refractive index can be set flexibly.

  As mentioned above, although the various Example of this invention was described, this invention is not limited to these Examples, A various structure can be taken in the range which does not deviate from the meaning.

FIG. 2 is an explanatory diagram illustrating a schematic configuration of a front projection type projector according to a first embodiment. Explanatory drawing explaining the optical circulation unit of 1st Example. Explanatory drawing explaining the assembly | attachment of the optical circulation unit in 1st Example. Explanatory drawing which illustrates the light source device in 2nd Example. Explanatory drawing which illustrates the light source device in 3rd Example. Explanatory drawing which illustrates the light source device in 4th Example. Explanatory drawing which illustrates schematic structure of the light source device in a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector 11 ... Light source device 11a ... Light source device 11b ... Light source device 11c ... Light source device 11d ... Light source device 20 ... Semiconductor laser device 20a-20c ... Semiconductor laser device ... Semiconductor laser device 21a-21c ... Integrator lens 37-39 ... Light Bulb 40 ... Dichroic prism 41 ... Projection lens 50 ... Screen 100, 110, 120, 130, 140 ... Light circulation unit 150 ... Light guide part 150a-150c ... Light guide part 200, 210, 220, 230, 240 ... Triangular prism 250 ... Half mirror 410, 420, 430 ... Reflecting surface 500 ... Refractive index variable means 510 ... Refractive index variable element 520, 530 ... Electrode sheet 600, 610 ... Rod integrator 800, 810, 820, 830 ... Air gap 900 ... Optical fiber

Claims (14)

A light source device,
A light emitting means for emitting light;
A branching means for reflecting a part of the incident light and transmitting the rest,
A light guiding means for circulating incident light incident through the branching means and making the light incident on the branching means again.
The branching unit outputs a part of incident light which is emitted from the light emitting unit and enters through the light guiding unit as first reflected light toward the irradiation surface, and the rest is the first transmitted light. The incident surface is incident on the light guide means, and a part of the incident light from the light guide means is incident again on the light guide means as second reflected light, and the remaining light is incident on the irradiation surface as second transmitted light. Light source device that outputs to The light source device according to claim 1,
The light guide means is configured such that an optical path length until the incident light from the branching means enters the branching means again is equal to or longer than a coherent distance of light emitted from the light emitting means. apparatus. The light source device according to claim 1,
The light guide device has a plurality of reflecting surfaces, and circulates the incident light by reflecting the light with the plurality of reflecting surfaces. The light source device according to claim 3,
The light guide means includes four triangular prisms whose bottom surface is a right triangle, and of the four triangular prisms, the side surface including the hypotenuse of the bottom surface of the three triangular prisms is the reflective surface. And the side surface including the hypotenuse of the bottom surface of the remaining one of the four triangular prisms is disposed to face the light emitting means.
The light source device, wherein the branching unit is disposed so as to contact a side surface including a hypotenuse of the bottom surface of the remaining one triangular prism. The light source device according to claim 4, further comprising:
The triangular prism is formed of a member that has substantially the same refractive index as that of the member forming the prism and transmits light, and is disposed between the branching unit and the light emitting unit so as to be in contact with the branching unit. A light source device comprising a first transmission member. The light source device according to claim 5,
The light source device, wherein the first transmission member is a triangular prism having substantially the same shape and size as the four triangular prisms, and a side surface including a hypotenuse of a bottom surface is disposed in contact with the branching unit. The light source device according to claim 4,
An arbitrary first triangular prism of the four triangular prisms and a second triangular prism adjacent to the first triangular prism include a first side surface including opposite sides of a right triangle on the bottom surface of the first triangular prism. And a side surface including the opposite side of a right triangle on the bottom surface of the second triangular prism, the first triangular prism, and the second triangular prism adjacent to the first triangular prism, Different third triangular prisms include a second side surface including a right triangle adjacent to the bottom surface of the first triangular prism, and a side surface including a right triangle adjacent side to the bottom surface of the third triangular prism. And arranged so that the vertices between the opposite sides of the right triangles on the bottom surfaces of all the triangular prisms and the adjacent sides coincide with each other. The light source device according to claim 7,
The light source device in which the shape of the bottom surface of each triangular prism is a right-angled isosceles triangle. The light source device according to claim 4,
Arbitrary first triangular prism among the four triangular prisms, a second triangular prism adjacent to the first triangular prism, an adjacent first triangular prism, and the first triangular prism A first triangular prism having a third triangular prism different from the prism, and a fourth triangular prism adjacent to the third triangular prism and different from the second triangular prism. , The second triangular prism, the third triangular prism, and the fourth triangular prism include at least an interval between the first triangular prism and the second triangular prism, and the third triangular prism and the The light source device is arranged so that the interval between the fourth triangular prisms is substantially equal. The light source device according to claim 9, further comprising:
A light source including a second transmission member that is disposed between the first triangular prism and the second triangular prism and between the third triangular prism and the fourth triangular prism and transmits light. apparatus. The light source device according to claim 9,
The second transmissive member is a light source device including a rod integrator. The light source device according to claim 1, further comprising:
At least one refractive index variable element that is arranged in an optical path inside the light guide means of the emitted light and whose refractive index changes according to a change in a predetermined condition;
A light source device comprising: condition changing means for changing the predetermined condition. The light source device according to claim 11,
The light source device, wherein the predetermined condition includes at least one of a magnetic field and an electric field at a portion where the refractive index variable element is disposed, and a temperature and stress applied to the refractive index variable element.   A projector comprising the light source device according to claim 1.

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