JP2008129315A - Light source apparatus and image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of speckle noise generated in the projection of an image by light output from a light source apparatus. <P>SOLUTION: In a resonator 120, incident laser light W10 from a light emitting element 110a is resonated at a steady state. When turning back light beams W2 and W4 having a different phase from the resonated light in the resonator 120 are made incident on the resonator 120, the steady state is broken due to the difference in the phases and a fluctuation of laser light is created in the resonator. As a result, the resonance becomes instable and a mode hop occurs in which the oscillation mode of the laser light in the resonator 120 varies. When the mode hop occurs, the laser light becomes instable in the resonator 120 and the laser light is oscillated at various wavelengths. As a result, laser light beams having various wavelengths are output from the resonator 120, various speckle patterns appear as time elapses, and the generation of the speckle pattern recognized as noise by an observer is suppressed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  A projector that irradiates a spatial light modulation device such as a light valve or a digital mirror device (DMD) with illumination light of a light source device and displays an image on a screen is used. For example, a laser light source is used as the light source device. Laser light sources have the advantage of higher energy efficiency and color reproducibility than lamp light sources.

JP 2004-144936 A JP 2004-503923 A

  However, when the phases of the light beams emitted from the light source device are aligned, such as a laser light source, interference occurs during projection onto the screen, so that interference fringes and spots called speckle patterns appear in the space in front of the screen. . Interference fringes and spots are generally called speckle noise. The viewer sees a double image of the screen surface and speckle noise, and tries to focus on each of the screen surface and speckle noise. 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, suppression of the generation of speckle noise is desired in an image display device using a light source device.

  The present application has been made in view of such problems, and an object thereof is to suppress the generation of speckle noise that occurs 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 laser light source that outputs laser light using a light emitting element and a resonator that oscillates light output from the light emitting element;
Return light generating means for returning a part of the laser light as return light into the resonator of the laser light source, and
The gist is to change the wavelength of the laser light emitted from the laser light source by the return light.

  According to the above-described aspect, the light output from the laser light source can be returned again into the laser light source, thereby generating a so-called mode hop in which the oscillation mode of the laser light changes, so that a plurality of wavelengths from the laser light source can be generated. Can output light. Therefore, a plurality of speckle patterns are generated and the speckle patterns are overlapped and averaged, so that speckle noise can be reduced.

In the light source device of the first aspect,
The return light generation means may be an optical element that is disposed on the optical path of the laser light and reflects a part of the incident laser light as the return light to the resonator and allows the rest to pass. Good.

  According to the above-described aspect, the mode hop can be generated by arranging the optical element having the reflection surface on the optical path of the laser light. Therefore, speckle noise can be reduced with a simple configuration.

In the light source device of the first aspect,
The optical element may be a plane mirror having a through hole for allowing light output from the laser light source to pass therethrough.

  According to the above-described aspect, part of the laser light output from the laser device passes through the through hole, and the rest is reflected by the plane mirror. Therefore, mode hops can be generated with a simple configuration, and the types of wavelengths output from the light source device can be increased. As a result, speckle noise can be reduced.

In the light source device of the first aspect,
The optical element may be a concave mirror in which a through hole for allowing light output from the laser light source to pass therethrough is formed.

  Since the light reflected by the concave mirror is reflected toward the inside of the resonator at an angle different from the incident angle, according to the above aspect, the laser beam loss is suppressed in the case of a laser having a large beam divergence angle. Mode hops can occur.

In the light source device of the first aspect,
In the optical element, a reflection film functioning as the reflection surface is formed on a part of an incident surface on which the laser light is incident, and a part of the laser light incident on the optical element is reflected by the reflection film. The remainder of the incident laser beam may be transmitted.

  According to the above aspect, by forming a reflective film on the conventionally used optical element, it is possible to reflect a part of the incident laser light and return it to the resonator, and to transmit the remaining laser light. it can. Therefore, speckle noise can be reduced at low cost.

In the light source device of the first aspect,
The optical element may have a structure in which an angle of the reflection surface with respect to a traveling direction of the laser light incident on the optical element can be changed.

  According to the above aspect, the amount of light incident on the optical element can be changed according to the amount of change in the angle of the reflecting surface. Therefore, the amount of light returned to the resonator as return light can be adjusted by changing the angle of the reflecting surface, and the occurrence of mode hops can be controlled.

In the light source device of the first aspect,
A detection means for detecting the intensity of the irradiation laser beam output from the laser light source and irradiating the irradiation object;
The optical element may change the angle according to the detected intensity.

  According to the above aspect, the generation of the mode hop can be controlled in accordance with the detected intensity of the laser light. Therefore, speckle noise can be reduced while suppressing a decrease in light intensity due to mode hops.

In the light source device having the first configuration,
The optical element may include at least one of a MEMS mirror and a galvanometer mirror.

  Since the MEMS mirror and the galvanometer mirror operate in response to the application of an electric signal, according to the above-described aspect, the angle of the optical element can be easily changed, and the amount of return light can be arbitrarily controlled.

In the light source device of the first aspect,
The laser light source has a plurality of light emitting elements and resonators corresponding to the plurality of light emitting elements,
The optical element may be arranged to reflect light output from at least one light emitting element among the plurality of light emitting elements as the return light.

  According to the above aspect, only the laser light output from the specific light emitting element is returned to the laser light source as return light, and the laser light output from the other light emitting elements is applied to the irradiation object without going through the return light generating means. Is output. Therefore, since the laser light output from a certain light emitting device is stably output continuously, instability of the output intensity of the laser generated at the time of mode hopping can be reduced, and the decrease in laser intensity can be suppressed.

  A second aspect of the present invention provides an image display device having a light source device. The gist of the image display device of the second aspect is that it comprises the light source device of the first aspect.

  According to the above-described aspect, since the image can be displayed using the laser beam with suppressed coherence, the generation of speckle noise can be reduced. Therefore, the discomfort felt by the viewer can be suppressed, and the viewer's fatigue can be reduced.

  In the present invention, the various aspects described above can be applied by appropriately combining or omitting some of them.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on examples with appropriate reference to the drawings.
A. First embodiment:
A1. System configuration:
A projector as an image display apparatus in the first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory diagram illustrating the schematic configuration of the image display apparatus according to the first embodiment. FIG. 2 is an explanatory diagram illustrating the detailed configuration of the light source device according to the first embodiment.

  As shown in FIG. 1, the projector 1000 includes light source devices 10, 20, 30, a uniformizing optical element 50, a light valve 60, a dichroic prism 70, and a projection lens 80. The light source device 10 includes a semiconductor laser device 100a and a return light generation optical element 200. The light source device 20 includes a semiconductor laser device 100b and a return light generation optical element 200. The light source device 30 includes a semiconductor laser device 100c and a return light generating optical element 200.

  Each of the semiconductor laser devices 100a, 100b, and 100c functions as a light source of the projector 1000. For example, the semiconductor laser device 100a outputs a red laser beam having a wavelength of about 650 nm, the semiconductor laser device 100b outputs a green laser beam having a wavelength of about 540 nm, and the semiconductor laser device 100c has a blue color having a wavelength of about 430 nm. Outputs laser light. Since laser light is absorbed by various devices, the amount of light output from the semiconductor laser device and the amount of light used for image projection are slightly different.

  The return light generating optical element 200 reflects a part of the incident laser light toward the output semiconductor laser device and outputs the remaining light toward the uniformizing optical element 50. Hereinafter, the laser light returned to the semiconductor laser devices 100a to 100c by the return light generating optical element is referred to as “return light”.

  The uniformizing optical element 50 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 uniformizing optical element 50, a bright image can be projected on the entire screen. In this embodiment, a diffractive optical element is used as the uniformizing optical element 50.

  The light valve 60 is formed using high temperature polysilicon (HTPS: High Temperature Poly-Silicon), and is an active matrix drive type transmissive liquid crystal panel. The light valve 60 draws an image by controlling incident light.

  The dichroic prism 70 has a configuration in which four triangular prisms are combined to form a rectangular parallelepiped. The dichroic prism 70 combines the red laser light, the green laser light, and the blue laser light that have passed through the light valve 60 to form an image, and project the image. Project to the lens 80.

  The projection lens 80 projects the image projected from the dichroic prism 70 onto the screen 90.

  As described above, the projector 1000 causes the light emitted from the semiconductor laser devices 100 a to 100 c to enter the respective light valves 60 to form an image, and then combines the emitted light and projects it onto the screen 90. The viewer visually recognizes the image projected on the screen 90.

A2. Detailed configuration of light source device:
With reference to FIG. 2, the detailed configuration of the light source devices 10, 20, and 30 in the first embodiment will be described by taking the light source device 10 as an example. The light source device 10 includes a semiconductor laser device 100c as a laser light source and a return light generating optical element 200.

  As shown in FIG. 2, the semiconductor laser device 100a includes a light emitting element 110a and a resonator 120.

  The light emitting element 110a is a semiconductor laser that emits laser light. The light emitting element 110a outputs laser light having a wavelength of about 650 nm. The light emitting element of the light source device 20 outputs laser light having a wavelength of about 540 nm, and the light emitting element of the light source device 30 outputs light having a wavelength of about 430 nm. However, these wavelengths are merely examples.

  The resonator 120 includes a pair of mirrors 121 and 122 that reflect a part of incident light. These mirrors 121 and 122 are provided so as to sandwich the light emitting unit 111 therebetween. The resonator 120 is configured such that the distance between the resonator mirrors 121 and 122 is an integral multiple of a half wavelength of a predetermined wavelength, and resonates and amplifies light having a predetermined wavelength between the resonator mirrors. To do. Specifically, the mirror 122 provided on the light emission side of the light emitting unit 111 transmits a part (about 98 to 99%) of light having a predetermined wavelength in the incident laser light to the mirror 121 on the light emitting element 110a side. And part of the remaining laser light is transmitted. The mirror 121 on the light emitting element 110 a side reflects the light reflected by the mirror 122 provided on the light emitting side of the light emitting unit 111 toward the mirror 122. As described above, light having a predetermined wavelength among the light incident on the resonator 120 is repeatedly reflected and amplified by the mirrors 121 and 122. Since the intensity of the amplified laser light is significantly higher than the intensity of light of other wavelengths, it passes through the resonator mirror 122 toward the return light generating optical element 200. The laser light W2 that has been amplified and transmitted through the resonator mirror 122 can be regarded as light having a substantially single wavelength.

  The return light generating optical element 200 is formed in a substantially central portion with a reflective surface 202 having one surface formed in a concave shape and deposited with a reflective film made of a dielectric multilayer film or metal (for example, silver). It is constituted by a concave mirror having a through hole 201. Hereinafter, in the first example, the return light generating optical element 200 is referred to as a concave mirror 200. The laser light incident on the through-hole 201 of the concave mirror 200 passes through the concave mirror 200 and is output toward the uniformizing optical element 50. The reflecting surface 202 of the concave mirror 200 reflects incident laser light from the semiconductor laser devices 100a to 100c toward the output semiconductor laser devices 100a to 100c, respectively. For example, the laser beam output from the semiconductor laser device 100a is returned to the semiconductor laser device 100a again.

  The movement of the laser light of the light source device 10 will be described. Of the laser light amplified by the resonator 120 and output toward the concave mirror 200, the laser light (laser light W <b> 3) that has entered the through-hole 201 of the concave mirror 200 passes through the concave mirror 200 to the uniformizing optical element 50. Proceed toward. On the other hand, among the laser beams output toward the concave mirror 200, the laser beams (laser beams W1 and W5) incident on the reflecting surface 202 of the concave mirror 200 are reflected and returned as the return beams W2 and W4 again to the resonator of the laser device 100a. 120 is incident.

  When the return lights W2 and W4 having different phases from the light resonated in the resonator 120 enter the resonator 120, the steady state is broken due to the phase shift, and the laser light in the resonator is fluctuated. . As a result, the resonance state becomes unstable, and a mode hop in which the oscillation mode of the laser beam of the resonator 120 changes occurs. When the mode hop occurs, the state of the laser beam in the resonator 120 becomes unstable, and the laser beam oscillates at various wavelengths. As a result, laser light having various wavelengths is output from the resonator 120. That is, the wavelength of the laser light emitted from the semiconductor laser device 100a is changed by the return lights W2 and W4.

  In general, it is known that a small amount of return light is generated due to various factors. However, in this embodiment, by installing a configuration for positively generating return light in the light source device, As the amount increases, return light is continuously generated.

  A part of the laser light output from the resonator 120 is reflected by the concave mirror 200 and enters the resonator 120 again as return light. Therefore, the laser light in the resonator 120 is in a state in which mode hops are continuously generated, and laser light of various wavelengths is continuously output from the resonator 120, and the laser light penetrating through the output laser light. The light incident on the hole 201 passes through the concave mirror 200 and travels toward the homogenizing optical element 50.

  In FIG. 2, for convenience of explanation, the laser beams W1, W3, W5, W6, W7, etc. output from the resonator are shown in parallel, but the laser beams output from the semiconductor laser device are elliptical. Has the property of spreading. Therefore, a collimator lens (not shown) that converts incident light into parallel light and outputs it is disposed between the light source device and the uniformizing means 50.

  According to the light source device of the first embodiment described above, mode hops can be continuously generated in the semiconductor laser device. With the mode hop, the wavelength width of the laser light output from the semiconductor laser widens, in other words, light of various wavelengths is output from the semiconductor laser device, and various speckle patterns appear over time. In general, when the same speckle pattern appears continuously, the viewer determines that the speckle pattern is noise, but when the appearing speckle pattern changes over time, the viewer will It is known that the speckle pattern is unlikely to be determined as noise due to the afterimage effect. Therefore, according to the light source device of the present invention, it is possible to suppress the generation of speckle patterns that are judged as noise by the viewer.

B. Second embodiment:
B1. Light source device schematic configuration:
In the second embodiment, a collimating lens disposed on the optical path of the laser light output from the semiconductor laser device is used as the return light generating optical element. FIG. 3 is an explanatory diagram illustrating the light source device 11 in the second embodiment. The light source device 11 includes a semiconductor laser device 100a and a collimating lens 210 that functions as a return light generating optical element. Since the semiconductor laser device 100a is the same as that of the first embodiment, the description thereof is omitted.

  The collimating lens 210 is an optical element that outputs incident light as parallel light. In this embodiment, the collimating lens 210 has a dielectric multilayer film functioning as the reflecting surface 222 or a reflecting film made of metal (for example, silver) or the like deposited on a part of the incident surface.

  The reflecting surface 212 of the collimating lens 210 reflects incident laser light from the semiconductor laser device toward the output semiconductor laser device. For example, the laser beam output from the semiconductor laser device 100a is returned to the semiconductor laser device 100a again.

  The operation of the light source device 11 will be described. Of the laser beams output from the semiconductor laser device 100a toward the collimator lens 210, the laser beams (laser beams W1 and W5) incident on the reflecting surface 212 of the collimator lens 210 are reflected and returned again as return beams W2 and W4. The light enters the laser device 100a. On the other hand, among the laser beams output toward the collimating lens 210, the laser beams (laser beams W3, W6, W7) incident on the region other than the reflecting surface 212 are transmitted through the collimating lens 210 and are made uniform. Proceed toward.

  In the semiconductor laser device 100a, a mode hop occurs due to the incidence of the return lights W2, W4. As a result, laser beams having various wavelengths are output from the resonator 120. A part of the light output from the semiconductor laser device 100a is reflected by the collimator lens 210 and is incident on the semiconductor laser device 100a again as return light. Accordingly, the semiconductor laser device is in a state where mode hops are continuously generated, and laser light of various wavelengths is continuously output from the semiconductor laser device 100a.

  According to the second embodiment, since repeated mode hops occur over time, the generation of speckle noise can be suppressed. Further, since a function for generating return light can be added to the collimating lens, it is not necessary to newly install a member as the return light generation optical element. Therefore, the light source device can be reduced in size.

C. Third embodiment:
In the third embodiment, a MEMS mirror is used as the return light generating optical element.

C1. Image display device schematic configuration:
FIG. 4 is an explanatory diagram illustrating the schematic configuration of the projector in the third embodiment. FIG. 5 is an explanatory diagram illustrating the detailed configuration of the light source device according to the third embodiment.

  As shown in FIG. 4, the projector 2000 includes light source devices 12, 22, and 32, and a homogenizing optical element 50, a light valve 60, a dichroic prism 70, and a projection lens 80 similar to those in the first embodiment. The light source device 12 includes a semiconductor laser device 100a, a return light generation optical element 220a, and a sensor 150a. The light source device 22 includes a semiconductor laser device 100b, a return light generation optical element 220b, and a sensor 150b. The light source device 32 includes a semiconductor laser device 100c, a return light generating optical element 220c, and a sensor 150c.

  In the third embodiment, the return light generating optical elements 220a, 220b, and 220c are MEMS (Micro Electro Mechanical Systems) mirrors. Hereinafter, the return light generating optical elements 220a, 220b, and 220c are referred to as MEMS 220a, 220b, and 220c.

  Each of the MEMS 220a, 220b, and 220c includes a semiconductor integrated circuit and a reflection mirror that are integrally formed. The reflection mirror is disposed on a surface on which incident light from the MEMS semiconductor laser device 100a is incident, and reflects about 99% of the incident light. Each of the MEMSs 220a, 220b, and 220c changes the angle of the reflecting mirror with respect to the traveling direction of incident light from the semiconductor laser device in accordance with an electric signal given to the semiconductor integrated circuit that each MEMS 220a, 220b, and 220c has. For example, in the MEMS 220a, the incident angle of the laser light output from the semiconductor laser device 100a to the MEMS 220a increases from 0 degree in accordance with an electrical signal given to the semiconductor integrated circuit (as indicated by an arrow X in FIG. 5). )Operate. The laser light incident on the reflection mirrors of the MEMS 220a, 220b, and 220c is reflected and incident on the output semiconductor laser device as return light.

  The movement of the laser light in the light source device 12 will be described. A part of the laser light output from the semiconductor laser device 100a is incident on the reflection mirror of the MEMS (laser light W20), reflected, and again incident on the resonator 120 of the semiconductor laser device 100a as return light W21. Therefore, a mode hop occurs in the semiconductor laser device 100a, and light having a plurality of wavelengths oscillates. As a result, laser light having various wavelengths is output from the semiconductor laser device 100a.

  FIG. 6 is an explanatory diagram illustrating functional blocks related to the light source device of the projector 2000 according to the third embodiment. As shown in FIG. 6, the projector 2000 includes light source devices 12, 22, 32 and a control unit 160. The light source device 12 includes a semiconductor integrated circuit 221a and a sensor 150a of the MEMS 220a, the light source device 22 includes a semiconductor integrated circuit 221b and a sensor 150b of the MEMS 220b, and the light source device 32 includes a semiconductor integrated circuit 221c and a sensor 150c of the MEMS 220c. .

  The sensors 150a, 150b, and 150c detect the intensity of the laser beam output from the light source device in which each sensor is installed, and notify the controller 160 of the detected intensity. As shown in FIG. 5, the light intensity of the laser light is detected by disposing the sensor 150 a in the vicinity of the homogenizing optical element 50 and detecting the light intensity of the scattered light W30 incident from the homogenizing optical element 50. There is a correlation between the light intensity of the laser light output from the light source device and the scattered light W30. Therefore, as described above, by detecting the light intensity of the scattered light, the light intensity of the laser light can be measured without arranging a sensor on the optical path of the laser light output from the light source device.

  The controller 160 sends an electrical signal to the semiconductor integrated circuit 221a of the MEMS 220a every 1/60 sec according to the detected value of the light intensity of the output laser beam received from the sensor 150a.

  The semiconductor integrated circuit 221a changes the angle of the mirror in accordance with the electrical signal sent from the control unit 160, like a MEMS 220a 'indicated by a broken line in FIG.

  Generally, in a semiconductor laser device, when a mode hop occurs, the output wavelength varies, and the light intensity of the output laser beam, that is, the output decreases. Since the degree of reduction varies depending on each light source device, the color balance of the image projected on the screen is reduced in a projector such as this embodiment that outputs laser light of a different color for each light source device. Therefore, the control unit 160 controls one or more MEMSs among the MEMSs of the light source devices 12, 23, 33 based on the light intensity of the output laser light received from each of the three light source devices 12, 23, 33. The balance of the light intensity of the laser light output from the three light source devices is adjusted. Specifically, for example, the detection value from the sensor 150c of the light source device 32 that outputs blue laser light is the detection value from the sensor 150a of the light source device 12 that outputs red laser light, and the light source device 22 that outputs green laser light. If the blue laser light intensity is lower than the red laser light and the green laser light, the semiconductor integrated circuit 221c of the MEMS 220c of the light source device 32 that outputs the blue laser light is electrically connected. A signal is sent to adjust the angle of the MEMS 220c. By doing so, the laser light W26 output from the resonator 120 of the light source device 32 can reduce the amount of light reflected by the MEMS 220c, so that the occurrence of mode hops in the light source device 32 can be suppressed. Therefore, the light intensity of the blue laser light output from the light source device 32 can be increased.

  According to the light source device of the third embodiment described above, the amount of the return light can be controlled by using the MEMS having a movable reflecting surface angle with respect to the incident light as the return light generating element. Therefore, it is possible to control the generation of mode hops in a semiconductor laser device that is fixedly installed and always generates return light. Therefore, the balance of the intensity of the laser light output from each light source device can be adjusted while reducing the occurrence of speckle noise, and the color balance of the image projected on the screen can be improved.

  In the third embodiment described above, the MEMS is controlled in accordance with the detection value of the sensor. However, for example, the state of the MEMS 220a and the state of the MEMS 220a 'may be repeated at regular intervals.

D. Fourth embodiment:
In the fourth embodiment, an array semiconductor laser device 500 is used as a laser light source. In the fourth example, as in the third example, MEMS is used as the return light generating optical element.

  FIG. 7 is an explanatory diagram illustrating a schematic configuration of the light source device 13 according to the fourth embodiment. The light source device 13 includes an array semiconductor laser device 500, a MEMS 230a, and a resonator mirror 550.

  The array semiconductor laser device 500 includes six light emitting elements (semiconductor lasers) 520 to 525 that emit laser light, resonator mirrors 530 to 535, and a support portion 510 that supports the light emitting elements 520 to 526.

  The light emitting elements 520 to 526 output laser beams having substantially the same peak wavelength. The peak wavelengths of the laser beams output from the light emitting elements 520 to 526 do not have to be completely coincident, and there may be some variation. Generally, it differs by about several nanometers due to a manufacturing error of the light emitting element.

  The resonator mirror 550 has a reflective film made of a dielectric multilayer film, metal (for example, silver) or the like deposited on a glass material, reflects a part of incident light, and directs a part toward the homogenizing optical element 50. Through.

  The laser light W50 output from the light emitting element 520 is oscillated between the resonator mirror 550 and the resonator mirror 530. Similarly, the laser beam W51 output from the light emitting element 521 is oscillated between the resonator mirror 550 and the resonator mirror 531, and the laser beam W52 output from the light emitting element 522 is combined with the resonator mirror 550 and the resonator. The laser beam W53 oscillated between the mirror 532 and output from the light emitting element 523 is oscillated between the resonator mirror 550 and the resonator mirror 533. The laser light amplified by the oscillation passes through the resonator mirror 550 toward the uniformizing optical element 50. Since the laser light output from the light emitting elements 520 to 523 does not receive the return light generated by the MEMS 230a, it always stably outputs laser light having substantially the same wavelength peak.

  The MEMS 230a is parallel to the state in which the laser light output from the light emitting element 524 can be incident on the resonator mirror 535 of the light emitting element 525 by reflection of the mirror and the traveling direction of the laser light output from the light emitting element 524. The angle is adjusted with respect to the traveling direction of the laser light output from the light emitting element 524 so that the state becomes a state (state B). Specifically, the MEMS 230a operates so as to change from the state A to the state B and from the state B to the state A (arrow Y in FIG. 7) in units of 1 millisecond. Note that 1 millisecond is merely an example and is not limited thereto.

  Since the MEMS 230a is always operating, when the MEMS 230a is in the state B, a part of the light output from the light emitting element 525 is not reflected by the MEMS 230a and oscillates between the resonator mirror 550 and the resonator mirror 535. (Laser beam W57). Here, when the laser beam W54 output from the light emitting element 524 is reflected by the MEMS 230a and enters the resonator mirror 535 as the return beam W55, the laser beam oscillated between the resonator mirror 535 and the resonator mirror 550 is converted into the laser beam. Therefore, laser beams having different phases (return light W55) are incident. As a result, mode hops occur in the laser light oscillated between the resonator mirror 550 and the resonator mirror 535, and light of various wavelengths is transmitted through the resonator mirror 550. Therefore, the array semiconductor laser device 500 stably outputs laser beams having various wavelengths together with laser beams W50 to 53 having substantially the same wavelength peak.

  According to the light source device of the fourth embodiment described above, mode hops can be generated only for the laser light output from the specific light emitting element, so that the entire laser of the laser light output from the light source device 13 is generated. While suppressing the decrease in strength, it is possible to reduce the generation of speckle noise.

  The light source device of the fourth embodiment always drives the MEMS in units of 1 millisecond. For example, as in the third embodiment, the light intensity of the laser light output from each light source device using the sensor is changed. The MEMS may be detected and the MEMS may be controlled according to the detected light intensity.

E. Example 5:
In the fifth embodiment, a plane mirror is used as the return light generating optical element.

E1. Light source device schematic configuration:
FIG. 8 is an explanatory diagram illustrating the schematic configuration of the light source device according to the fifth embodiment. The light source device 14 includes a light emitting element 110a, a resonator 120, and a plane mirror 240 that functions as a return light generating element. Since the light emitting element 110a and the resonator 120 are the same as those in the first embodiment, description thereof is omitted.

  The plane mirror 240 is a glass material in which a reflection film made of a dielectric multilayer film, metal (for example, silver) or the like is deposited on the surface on the resonator 120 side. In FIG. 8, among the laser beams oscillated and output by the resonator 120, the laser beam (laser beam W <b> 3) that has entered the through-hole 201 of the plane mirror 240 passes through the plane mirror 240 toward the uniformizing optical element 50. move on. On the other hand, among the laser beams output toward the plane mirror 240, the laser beams W1 and W5 incident on the plane mirror 240 are reflected and enter the resonator 120 again as return beams W2 and W4.

  In the resonator 120, since the return light W2 and the return light W4 having different phases are incident on the laser light incident from the light emitting element 110a, the oscillation state becomes unstable and a mode hop occurs. Therefore, laser light with various wavelengths is output from the resonator 120.

  Part of the light output from the resonator 120 is reflected by the plane mirror 240 and enters the resonator 120 again as return light. Therefore, the laser light in the resonator 120 is in a state where mode hops are continuously generated, and light of various wavelengths is continuously output from the resonator 120.

  According to the light source device of the fifth embodiment described above, it is possible to repeatedly generate mode hops, and thus it is possible to suppress the generation of speckle noise.

F. Modification (1) A pair of reflecting mirrors may be used as the return light generating optical element. FIG. 9 is an explanatory view illustrating a light source device in a complementary modification. The light source device 15 of this modification includes the same semiconductor laser device 100a as in the first embodiment and a pair of reflecting mirrors 250 and 251 as return light generating optical elements.

  The reflection mirrors 250 and 251 are mirrors having a high reflectance of about 99%, and are installed at a predetermined angle with respect to the light emitting surface of the light emitting element 110a. The predetermined angle is an angle at which the laser beam output from the resonator 120 can enter the resonator 120 again after being reflected by the reflection mirrors 250 and 251. By installing in this way, W1 and W4 incident on the reflection mirrors 250 and 251 can be made incident again on the resonator 120 as return lights W2 and W4, and the laser light oscillated in the resonator 120 is reflected. Mode hops can occur.

  According to this modification, the generation of speckle noise can be reduced with a simple configuration.

(2) In each of the above-described embodiments, each light emitting element outputs laser light having a wavelength of red light, laser light having a wavelength of green light, and laser light having a wavelength of blue light. The element outputs light having a wavelength of about twice as much as each color light, and a second harmonic generation element (SHG: Second Harmonic Generation) may be disposed between the light emitting element and the resonator or in the resonator. . FIG. 10 is an explanatory diagram illustrating the light source device in the present modification. The light source device 16 of this modification is obtained by adding a second harmonic generation element 600 to the light source device 10 of the first embodiment. In addition, the light emitting element 110a 'according to the present modification outputs light having a wavelength that is approximately twice the wavelength of red light.

  The second harmonic generation element 600 is a non-linear optical element that converts incident light into almost half the wavelength. Light output from the light emitting element 110 a ′ and traveling toward the resonator 120 passes through the second harmonic generation element 600, and is converted into light having a half wavelength. The wavelength conversion efficiency by the second harmonic generation element 600 has a non-linear characteristic. For example, the higher the intensity of the laser light incident on the second harmonic generation element 600, the higher the conversion efficiency. Further, the conversion efficiency of the second harmonic generation element 600 is about 40 to 50%.

  The resonator 120 is disposed between the second harmonic generation element 600 and the concave mirror 200 that is a return light generation optical element. Since the conversion efficiency of the second harmonic generation element 600 is about 40 to 50% as described above, the resonator 120 is disposed between the second harmonic generation element 600 and the concave mirror 200 to thereby provide a light source device. The light intensity of the laser beam output from 16 can be improved.

(3) In the projector described in the above-described embodiments, an image is displayed using a liquid crystal light valve. However, for example, an image may be displayed using a digital micromirror device (DMD). . FIG. 11 is an explanatory diagram illustrating a schematic configuration of a projector in the present modification. The projector 3000 according to this modification includes light source devices 10, 20, and 30 similar to those in the first embodiment, dichroic mirrors 810 and 811, and a digital micromirror device (DMD) 820.

  The light source devices 10, 20, and 30 are the same as in the first embodiment. Accordingly, laser light of various wavelengths is output from each light source device.

  The dichroic mirrors 810 and 811 are mirrors in which a glass substrate is coated with a film that reflects a specific wavelength range and transmits only light having a specific wavelength. The dichroic mirrors 810 and 811 function as filters for separating incident light into three primary colors of a red component, a green component, and a blue component. In this modification, the dichroic mirror 810 transmits the red component and reflects the green component. The dichroic mirror 811 reflects the red component and the green component and transmits the blue component.

  The DMD 820 is one type of MEMS device, and is a display element in which a large number of micro mirror surfaces (micro mirrors) are arranged in a plane.

  As shown in this modification, even in a projector using a DMD, generation of speckle noise can be suppressed by using a light source device having a return light generation device.

(4) In the above-described embodiment, the projector is described as an example of the image display device. However, for example, the projector may be configured as an illumination device or a monitor device including the above-described light source device.

  Although various embodiments of the present invention have been described above, it is needless to say that the present invention is not limited to these embodiments and can take various configurations without departing from the spirit of the present invention.

Explanatory drawing which illustrates about schematic structure of the image display apparatus in 1st Example. Explanatory drawing which illustrates about the detailed structure of the light source device in 1st Example. Explanatory drawing which illustrates the light source device in 2nd Example. Explanatory drawing which illustrates about schematic structure of the projector in 3rd Example. Explanatory drawing which illustrates about the detailed structure of the light source device in 3rd Example. Explanatory drawing which illustrates the functional block regarding the light source device of the projector in 3rd Example. Explanatory drawing which illustrates schematic structure of the light source device in 4th Example. Explanatory drawing which illustrates schematic structure of the light source device in 5th Example. Explanatory drawing which illustrates the light source device in a modification. Explanatory drawing which illustrates the light source device in a modification. Explanatory drawing which illustrates schematic structure of the projector in a modification.

Explanation of symbols

10, 11, 12, 13, 14, 15, 16 ... light source device 20, 22 ... light source device 30, 32 ... light source device 50 ... uniformizing optical element 60 ... light valve 70 ... dichroic prism 80 ... projection lens 90 ... screen 100a ... Semiconductor laser device 100b ... Semiconductor laser device 100c ... Semiconductor laser device 110a ... Light emitting element 120 ... Resonator 121 ... Mirror 122 ... Mirror 150a ... Sensor 150b ... Sensor 150c ... Sensor 160 ... Controller 200 ... Return light generating optical element 200 ... Concave mirror 201 ... through hole 202 ... reflecting surface 210 ... collimating lens 212 ... reflecting surfaces 220a, 220b, 220c ... light generating optical elements 221a, 221b, 221c ... semiconductor integrated circuit 222 ... reflecting surface 240 ... reflecting mirror 240 ... planar mirror 500 ... array Semiconductor Laser device 510 ... support section 520, 521, 522, 523, 524, 525 ... light emitting element 530, 531, 532, 533, 534, 535 ... resonator mirror 600 ... second harmonic generation element 810 ... dichroic mirror 811 ... dichroic Mirror 1000, 2000, 3000 ... Projector

Claims (10)

A light source device,
A laser light source comprising: a light emitting element; and a resonator that oscillates the light output from the light emitting element; and a laser light source that outputs laser light using the light emitting element and the resonator;
Return light generating means for returning a part of the laser light as return light to the resonator, and
A light source device that changes the wavelength of laser light emitted from the laser light source by the return light. The light source device according to claim 1,
The return light generating means is an optical element that is disposed on the optical path of the laser light, and is an optical element that reflects a part of the incident laser light as the return light to the resonator and passes the rest. apparatus. The light source device according to claim 2,
The light source device, wherein the optical element is a plane mirror having a through hole for allowing light output from the laser light source to pass therethrough. The light source device according to claim 2,
The optical element is a light source device that is a concave mirror in which a through hole for allowing light output from the laser light source to pass therethrough is formed. The light source device according to claim 2,
The optical element has a reflection region that functions as the reflection surface, and a transmission region that transmits a part of the incident laser light,
A part of the incident laser light is reflected by the reflection film, and the rest of the incident laser light is transmitted through the transmission region. The light source device according to claim 2,
The optical element is a light source device having a structure in which an angle of the reflection surface with respect to a traveling direction of the laser light incident on the optical element can be changed. The light source device according to claim 5, further comprising:
A detection means for detecting the intensity of the irradiation laser beam output from the laser light source and irradiating the irradiation object;
The optical element is a light source device that changes the angle according to the detected intensity. The light source device according to claim 5,
The optical element includes a light source device including at least one of a MEMS mirror and a galvanometer mirror. The light source device according to claim 5,
The laser light source has a plurality of light emitting elements,
The optical element is a light source device arranged to reflect light output from at least one of the plurality of light emitting elements as the return light.   An image display device comprising the light source device according to claim 1.

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