WO2008015951A1

WO2008015951A1 - Display device

Info

Publication number: WO2008015951A1
Application number: PCT/JP2007/064636
Authority: WO
Inventors: Toshifumi Yokoyama; Kiminori Mizuuchi; Kazuhisa Yamamoto
Original assignee: Panasonic Corporation
Priority date: 2006-08-04
Filing date: 2007-07-26
Publication date: 2008-02-07

Abstract

A display device includes: a semiconductor laser for emitting an exciting laser beam; a resonator having a solid-state laser excited by input of the exciting laser beam for emitting laser and a first and a second mirror arranged so as to sandwich the solid-state laser; a wavelength conversion element arranged inside the resonator and converting the basic wave laser beam into a higher harmonic laser beam; an image display element for displaying an image by irradiation of the higher harmonic laser beam; and a laser drive unit for driving the semiconductor laser so as to lower the output of the higher harmonic laser beam at a cycle of frame cycle of the video signal applied to the image display element and multiplied by an integer. It is possible to realize a high luminance and a large screen by stabilizing the output of the laser beam applied to the image display element.

Description

Specification

Display device

Technical field

TECHNICAL FIELD [0001] The present invention relates to a display device equipped with an SHG laser using wavelength conversion.

Background art

[0002] A display device using a laser as a light source has been proposed! (See, for example, Patent Document 1). An example of a display device using a laser is shown in FIG. FIG. 21 is a view of a conventional display device 51 as viewed from above. The laser light output from the red light source 52, the green light source 53, and the blue light source 54 is guided to the transmissive liquid crystal panel 56 after the light quantity distribution is made uniform using the rod integrator 55. The laser light that has passed through the transmissive liquid crystal panel 56 is combined by a combining prism 57, is transmitted through an output lens 58, and is output as an image. Semiconductor lasers are used as the red light source 52 (oscillation wavelength around 640 nm) and the blue light source 54 (oscillation wavelength around 440 nm). As the green light source 53, an SHG (Second Harmonic Generation) laser using wavelength conversion is used. Each light source 52 54 is continuously lit to increase the luminance of the display device 51. The SHG laser is an internal cavity type SHG laser. Specifically, laser light output from the pump semiconductor laser (wavelength 808 nm) is absorbed by the solid-state laser, and laser light (fundamental wave) having a wavelength of 1064 nm is output from the solid-state laser. The fundamental wave output from the solid-state laser is input to the wavelength conversion element, and the wavelength conversion element outputs 532 nm laser light with a wavelength of 1/2, which is the second harmonic.

[0003] In the display device 51 described above, a light source having a limited oscillation wavelength spectrum such as a semiconductor laser or an SHG laser is used as a light source, so that the design of optical components is easier than in the case of using a lamp. Yes, the optical system can be miniaturized. Furthermore, power consumption can be reduced compared to display devices that use lamps.

[0004] However, in the conventional display device 51 described above, when an internal cavity type SHG laser used as the green light source 53 is continuously lit, the SHG laser Output fluctuation occurred, and the color balance of the video output from the display device 51 was disturbed. In order to suppress the output fluctuations of the harmonics output from the SHG laser, it is common to use a high-accuracy temperature control element or temperature control device, or insert a device such as an etalon into the resonator. However, there have been disadvantages such as increased power consumption and size as a light source device and increased cost. In addition, if a device such as an etalon is inserted in the resonator, the fundamental wave is attenuated, resulting in a problem that the output of the harmonics is reduced. Considering the use of internal cavity SHG lasers for consumer products, the above disadvantages are significant.

[0005] By the way, the SHG laser (one apparatus of solid-state laser) using the above-described solid-state laser and wavelength conversion element excites a solid-state laser crystal by laser light from a semiconductor laser light source to cause laser oscillation. It has features such as small size, light weight, long life, high electro-optic conversion efficiency, and stable operation, and is used in various industrial fields. In such a solid-state laser device, laser light from a semiconductor laser light source is incident on a solid-state laser crystal by a coupling lens system, and the solid-state laser crystal sandwiched between mirrors is excited to oscillate fundamental laser light. In general, the fundamental laser beam is made incident on the wavelength conversion element of the nonlinear optical medium to generate the second harmonic component of the incident light, which is then emitted to the outside through the mirror on the output side.

[0006] If such a solid-state laser device is used, high-output green light (G light) can be obtained. As a specific configuration example, for example, a semiconductor laser light source is used and Nd: YVO or the like is used.

4 is excited to cause laser oscillation of the solid laser crystal between the reflecting mirror and the output mirror. This laser oscillation produces a fundamental laser beam with a wavelength of 1064 nm. By making this fundamental laser beam incident on the wavelength conversion element, a second harmonic wave having a wavelength of 532 nm can be obtained. With such a configuration, high-output G light can be obtained, so that it can be applied to laser displays, projection-type liquid crystal displays, and the like, and is being actively developed.

[0007] For example, a solid-state laser device that has high output and high efficiency and can reduce speckle noise and an image display device using the solid-state laser device are disclosed (for example, see Patent Document 2). This solid-state laser device uses a one-dimensional transverse multimode laser as a laser light source. It has a light source for excitation, a solid-state laser crystal in the optical resonator, and a wavelength conversion element. The solid-state laser crystal is excited with an elliptical transverse mode pattern to obtain a linear beam. It is configured to output linear light by making a linear beam incident on a wavelength conversion element. This makes it possible to realize a high-power and high-efficiency solid-state laser device using an elliptical transverse mode pattern. In addition, speckle noise can be reduced by reducing coherence due to excitation in the transverse multimode. Further, since the wavelength conversion element is arranged in the optical resonator, the power density of the oscillation light confined inside the optical resonator can be increased, and wavelength conversion can be performed with high efficiency.

[0008] In Patent Document 2 described above, an example in which a solid-state laser device outputs a linear laser beam using a one-dimensional lateral multimode laser and is used in a projection type liquid crystal display device is shown. However, in this example, no countermeasures have been disclosed or suggested for damage caused by overheating of the solid-state laser crystal or the wavelength conversion element of the solid-state laser device. Therefore, solid laser crystals and wavelength conversion elements are damaged when irradiated with high-density laser light, and it is difficult to oscillate harmonic laser light stably for a long time! Have it!

[0009] On the other hand, a configuration is shown in which a transmission plate for shifting the optical path of one laser beam is disposed on the laser beam incident side of the wavelength conversion element in the optical resonator, and this transmission plate is vibrated. (For example, see Patent Document 3). When the wavelength conversion element in the optical resonator transmits laser light to generate harmonics and convert the wavelength, the optical path of the laser light is shifted by vibrating the transmission plate. As a result of the enlargement of the laser light passage region in the wavelength conversion element, the temperature rise can be mitigated.

[0010] In Patent Document 3 described above, the transmission region of the laser beam is expanded to prevent overheating by vibrating the transmission plate while maintaining the laser beam deflection direction and crystal orientation necessary for phase matching. According to this method, it is necessary to always vibrate the transmission plate while operating the solid-state laser device, which makes the device configuration complicated and difficult to reduce the cost. .

Furthermore, a solid-state laser crystal and a wavelength conversion element are arranged in an optical resonator composed of a reflection mirror and an output mirror, and the position of the wavelength conversion element is shifted in a direction perpendicular to the optical axis of the laser light. There is also shown a solid-state laser device having a configuration including a moving mechanism that moves the moving mechanism in conjunction with laser light irradiation (for example, see Patent Document 4). . With such a configuration, the entire surface of the wavelength conversion element can be used effectively, the life of the wavelength conversion element can be extended, and as a result, the life of the solid-state laser device can be extended.

In Patent Document 4 described above, the wavelength conversion element is electrically moved to prevent damage to the wavelength conversion element, and the entire surface of the wavelength conversion element can be used effectively. In this method as well, a mechanical movement mechanism must be provided in the same manner as described above, the device configuration becomes complicated, and cost reduction is difficult.

[0013] A combination of a solid-state laser device capable of outputting such high-output G light and a semiconductor laser device, and irradiating a laser beam from the back surface of the liquid crystal panel, and a liquid crystal display device such as a projection-type liquid crystal display device or a thin television It is also being considered for use in However, in order to use a laser light source for a backlight unit such as a thin television, a configuration having a uniform luminance distribution over a relatively large area must be realized. It is also important to suppress speckle noise.

When used as a light source of a backlight unit of a liquid crystal display device, it is required to realize an illumination light source that is thin and has a uniform luminance over a large area at a low cost. In order to use a solid-state laser device for such a backlight unit, it is preferable to set the laser beam output from the solid-state laser device to a multimode. However, the multi-mode configuration has not yet been realized, especially with laser light sources that emit G light (G light sources).

Patent Document 1: JP-A-6-208089

Patent Document 2: Japanese Unexamined Patent Publication No. 2006-100772

Patent Document 3: Japanese Patent Laid-Open No. 7-22686

Patent Document 4: Japanese Patent Application Laid-Open No. 2004-22946

Disclosure of the invention

[0015] An object of the present invention is to provide a display device capable of increasing the brightness and enlarging the screen by stabilizing the output of the laser light applied to the image display element. [0016] A display device according to one aspect of the present invention includes a semiconductor laser that emits excitation laser light and laser oscillation that is excited by incidence of the excitation laser light and emits fundamental laser light. A resonator having a solid-state laser and first and second mirrors arranged so as to sandwich the solid-state laser, and a wavelength that is arranged inside the resonator and converts the fundamental laser light into harmonic laser light The output of the harmonic laser light is reduced at a period that is an integral multiple of the frame period of the image signal applied to the conversion element, the image display element that displays an image by irradiation of the harmonic laser light, and the image display element. And a laser driving section for driving the semiconductor laser.

[0017] In the above display device, the longitudinal mode of the oscillation state of the harmonic laser beam is changed to the multimode due to the decrease in the output of the harmonic laser beam in the period that is an integral multiple of the frame rate of the video signal. For this reason, the output of the harmonic laser beam is stabilized, the disturbance of the color balance of the image due to the unstable output of the harmonic laser beam is suppressed, and a high-quality image can be displayed.

Brief Description of Drawings

FIG. 1 is a plan view showing a schematic configuration of a display device according to a first embodiment of the present invention.

2 is a side view showing a schematic configuration of an internal cavity type SHG laser mounted on the green light source of FIG.

FIG. 3A is a diagram showing a longitudinal mode spectrum of a fundamental wave when a pump laser diode is continuously turned on, and FIG. 3B is a diagram showing a state in which the longitudinal mode spectrum of FIG. 3A fluctuates due to disturbance. .

FIG. 4 is a diagram for explaining a method of driving a pump semiconductor laser.

[Fig.5] Fig. 5A shows the fluctuation of the harmonic output when the pump laser diode is continuously turned on, and Fig. 5B shows the fluctuation of the harmonic output when the pump laser diode is driven with a nozzle. FIG.

[FIG. 6] FIG. 6A is a diagram for explaining driving of the liquid crystal panel, FIG. 6B is a diagram for explaining a method for inserting the output drop time, and FIG. 6C is a diagram for explaining another method for inserting the output drop time. FIG.

[FIG. 7] FIG. 7A is a diagram showing a zeroth-order transverse mode, FIG. 7B is a diagram showing a first-order transverse mode, and FIG. 7C. FIG. 7D is a diagram showing a secondary transverse mode, FIG. 7D is a diagram showing a transverse mode when the output fluctuates, and FIG. 7E is a diagram showing a primary transverse mode (vertical transverse mode).

FIG. 8] is a plan view showing a schematic configuration of the display device according to the third embodiment of the present invention.

FIG. 9] A diagram illustrating a method for driving a pump semiconductor laser.

10] A side view showing a schematic configuration of the internal cavity type SHG laser according to the fourth embodiment of the present invention.

FIG. 11A is a diagram showing a conventional beam shape, and FIG. 11B is a graph showing the relationship between the amount of pump light and the G light output.

FIG. 12A is a diagram showing a beam shape at an inclination angle Θ = 0.2 °, and FIG. 12B is a graph showing a relationship between the light amount of pump light and the G light output.

FIG. 13A is a diagram showing a beam shape at an inclination angle Θ = 0.3 °, and FIG. 13B is a graph showing a relationship between the light amount of pump light and the G light output.

14] A graph showing the relationship between pump light intensity and G light output at an inclination angle of Θ = 0.4 °.

15] A graph showing the relationship between the pump light intensity and the G light output at an inclination angle θ = 0 · 5 °.

16] FIG. 16A is a perspective view showing a schematic configuration of the display device according to Embodiment 5 of the present invention, FIG. 16B is a plan view thereof, and FIG. 16C is cut along the 5-5 line in FIG. 16B. FIG.

17] FIG. 17A is a plan view showing a schematic configuration of the display apparatus according to Embodiment 6 of the present invention, and FIG. 17B is a cross-sectional view taken along line 6-6-6 in FIG. 17A.

18] FIG. 18A is a plan view showing a schematic configuration of the display apparatus according to Embodiment 7 of the present invention, and FIG. 18B is a cross-sectional view taken along line 7-7-7 in FIG. 18A.

19] FIG. 19A is a plan view showing a schematic configuration of the display apparatus according to Embodiment 8 of the present invention, and FIG. 19B is a cross-sectional view taken along line 8-8-8 in FIG. 19A.

FIG. 20] is a plan view showing a schematic configuration of the display apparatus according to the ninth embodiment of the present invention. FIG. 21 is a plan view showing a schematic configuration of a conventional display device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element and description may be abbreviate | omitted.

[0020] (Embodiment 1)

In the following embodiments, a configuration and a driving method of an internal cavity type SHG laser in a display device including an internal cavity type SHG laser will be mainly described. FIG. 1 is a top view of the display device 1 according to the first embodiment of the present invention.

[0021] In the display device 1 that is effective in the present embodiment, as shown in FIG.

2. The laser light output from the green light source 3 and the blue light source 4 is guided to the transmissive liquid crystal panels 6a to 6c after the light quantity distribution is made uniform using the rod integrator 5. The laser beams that have passed through the transmissive liquid crystal panels 6a to 6c are combined by the combining prism 7 and transmitted through the projection lens 8 to be output as an image. Semiconductor lasers were used for red light source 2 (oscillation wavelength around 640 nm) and blue light source 4 (oscillation wavelength around 440 nm). As the green light source 3, an internal cavity type SHG (Second Harmonic Generation) laser that uses wavelength conversion to output green light was used. The control circuit 9 controls each light source and the transmissive liquid crystal panel. Since a light source with high power consumption such as a lamp is not used, it can be driven by battery 21! /.

FIG. 2 is a schematic diagram showing a schematic configuration of an internal cavity type SHG laser mounted on the green light source 3 of FIG. As shown in FIG. 2, the internal resonator type SHG laser 10 used in the present embodiment includes a pump semiconductor laser 11, a rod lens 12, a VBG13, a ball lens 14, and a solid-state laser having an oscillation wavelength of about 808 nm. 15, a wavelength conversion element 16, and a concave mirror 17. The pump light 18 having a wavelength of about 808 nm emitted from the pump semiconductor laser 11 is collimated by the rod lens 12 and incident on the VBG 13. VBG is an abbreviation for Volume Bragg Grating and is a transmissive diffraction grating. The pump light incident on VBG13 is partially reflected and fed back to the pump semiconductor laser 11, and the oscillation wavelength of the pump semiconductor laser 11 is selected by VBG13. Locked to the specified wavelength (808 nm).

[0023] In this embodiment, the VBG13 force and the return light amount are set to 20%. The appropriate amount of light returned from VBG13 is about 10-30%. If it is 10% or less, the wavelength lock is weakened. Further, if it is 30% or more, there is a greater possibility of causing unstable operation due to an increase in the amount of light in the pump semiconductor laser 11 as well as a decrease in the amount of transmitted light. Since the oscillation wavelength of the pump semiconductor laser 11 hardly changes even if the temperature changes by using the VBG13, a highly accurate temperature control device for the pump semiconductor laser 11 is unnecessary. It has become. Since the solid-state laser 15 has high absorption efficiency near 808 nm, it is very important that the wavelength of the semiconductor laser 11 does not change. This has a great effect on cost reduction, power consumption and size reduction of the apparatus.

In this embodiment, VBG13 is used to lock the oscillation wavelength of pump semiconductor laser 11! /, But a bandpass filter manufactured using a dielectric multilayer film is also used. An effect is obtained. The semiconductor laser 11 itself may be a DFB laser or a DBR laser having a wavelength lock function. The pump light 18 that is wavelength-locked by the VBG 13 is condensed on the solid-state laser 15 by the ball lens 14. The solid laser 15 was YVO doped with 3% Nd. The solid state laser 15 is excited by the pump light 18,

Four

A fundamental wave 19 having a wavelength of 1064 nm is generated. The fundamental wave 19 resonates in a resonator formed by the solid-state laser 15 and the concave mirror 17. A part of the fundamental wave 19 is wavelength-converted by the wavelength conversion element 16 installed in the resonator and output to the outside as a harmonic 20 having a wavelength of 532 nm.

In the present embodiment, periodic polarization inversion is formed in Mg: LiNbO in the wavelength conversion element 16

Three

What was done was used. In the present embodiment, a reflection coat for the fundamental wave 19 is formed on the surface of the output side of the force wavelength conversion element 16 constituting the resonator using the concave mirror 17, and the wavelength conversion element 16 is connected to the solid-state laser 15. You may make it the structure (microchip type) to adjoin. The internal cavity type SHG laser 10 is an effective configuration for realizing a compact and high-power green light source. The internal resonator type SHG laser 10 is used for the first reason that pump semiconductor lasers 11 with an oscillation wavelength of around 808 nm are easily available. In addition, the wavelength of the fundamental wave 19 output from the solid-state laser 15 is stable, and the solid-state laser The second reason is that high-precision wavelength locking and temperature control are not required. In addition, since the fundamental wave power in the resonator is large, the length of the wavelength conversion element 16 can be shortened, and harmonics output with respect to temperature changes compared to other means (for example, a waveguide type SHG laser). Variation can be reduced. In order to obtain green light with a wavelength of around 532 nm, a means to directly convert semiconductor laser light with an oscillation wavelength of about 1064 ηm into green light with a wavelength of around 532 nm is also considered. It is difficult to produce a high-power semiconductor laser with an oscillation wavelength of about 1064 nm. In addition to this, it is often necessary to control the temperature of the semiconductor laser and the wavelength conversion element. It is also possible to obtain high-power 1064nm laser light using a fiber laser, but in addition to making it difficult to reduce the size of the light source, it is accompanied by an increase in the wavelength conversion element due to higher output. Therefore, highly accurate temperature control of the wavelength conversion element is necessary.

FIGS. 3A and 3B show an example of a longitudinal mode spectrum of the fundamental wave output from one solid-state laser when the pumping semiconductor laser is driven by continuous lighting. If high-precision temperature control is not performed on the light source, or if the fundamental wavelength is not controlled using an optical component such as an etalon, the longitudinal mode spectrum changes from the state of Fig. 3A to the state of Fig. 3B. Sometimes. This is thought to be because the heat distribution and oscillation mode in the solid-state laser fluctuate with time due to continuous lighting. When the longitudinal mode spectrum changes, the phase matching state of the wavelength conversion element changes, and the proportion of the fundamental wave that is wavelength converted also changes. As a result, the output of the green light that is output fluctuates. Internal resonator type SHG laser When a single light source is used as a display light source, the power fluctuation of the laser is fatal. When used in a consumer display, the laser is small and low-cost, and control is also possible. Is required. In addition, a device that can operate stably even when the ambient temperature changes is required.

[0027] Therefore, in the display device 1 according to the present embodiment, the output of the semiconductor laser 11 for pumps is reduced in order to reduce harmonic output fluctuations while suppressing high-precision temperature control and the increase in the number of parts. The internal cavity type SHG laser 10 is driven by inserting a certain time (hereinafter referred to as “output reduction time”) during which the SHG laser 10 is reduced. The method for inserting the output drop time and the effect thereof will be described with reference to FIGS. 4, 5A and B, and FIGS.

FIG. 4 shows a driving method of the pumping semiconductor laser 11 of FIG. Form of this implementation In this state, as shown in FIG. 4, the semiconductor laser 11 was driven with a period Tl = 8.33 ms (drive frequency 120 Hz) and an output decrease time T2 = lms. The driving here is a repetitive operation between the power P2 of the pump light 18 in the normal driving and the power P1 (P2> P1) of the pump light 18 in the output reduction time. Fig. 5A shows the fluctuation of the output of the SHG laser 10 when the pump semiconductor laser 11 is continuously turned on. Fig. 5B shows the output drop time into the output of the pump semiconductor laser 11 and It is a figure which shows the output fluctuation | variation of the SHG laser 10 at the time of carrying out a Rus drive. As shown in Fig. 5A, when pump semiconductor laser 11 is continuously lit, the output fluctuation of SHG laser 10 is about 42%. As shown in Fig. 5B, pump semiconductor laser 11 is turned off. As shown in the figure, the output fluctuation is reduced to 3.5% or less when the pulse is driven, and the output fluctuation is suppressed to 1 or less of 10 minutes by the insertion of the above-mentioned output drop time.

[0029] The above effect is realized by constantly converting the longitudinal mode spectrum of the fundamental wave 19 into a multimode by inserting the output reduction time. In the internal cavity type SHG laser 10, in the case of multimode oscillation in which multiple longitudinal modes of the fundamental wave 19 exist, the sum frequency between each longitudinal mode is generated simultaneously with the harmonic 20 corresponding to each longitudinal mode. . As a result, the longitudinal mode spectrum of the fundamental wave 19 always operates stably in a multi-mode state, and the output of the harmonic 20 output from the SHG laser 10 changes to the human eye. I don't feel like it is. Therefore, it can be used without any problem as a light source for a display device.

[0030] Here, if P2−P1> 0.2 W or more, the longitudinal mode spectrum of the fundamental wave 19 can be converted into a multimode. In addition, if PK Pth is used, the fundamental wave 19 is more surely converted into multimode, and at the same time, the green light that is the harmonic 20 is not generated, which is effective in improving the contrast of the display device described later. Here, Pth is the power of the minimum level of pump light 18 necessary for the solid-state laser 15 to oscillate. In addition, the multi-mode is likely to occur under the conditions of T1 <0.5 s and T2> l ms. Since the output fluctuation is greatly reduced by inserting the output drop time, the internal resonator type SHG laser 10 can be used as the light source for the display.

[0031] As described above, in order to stabilize the output of the internal cavity type SHG laser 10, It is necessary to insert an output drop time of lms or more into the semiconductor laser 11 for the amplifier. In terms of drive frequency, it must be 1kHz or less. As described above, since it can be driven at a low frequency of 1 kHz or less, measures such as loss, reflection, and noise in the electronic circuit for driving the semiconductor laser 11 are almost necessary.

In this embodiment, YVO doped with 3% of Nd is added to the solid-state laser 15.

4 Although it is used, the doping amount of Nd is preferably 2% to 3%. When the amount of doping is large, the output rise time S of the green light (harmonic 20) output when the output reduction time T2 is changed to the high output time T1 is shortened, so the effect on the video output can be reduced. When the doping amount of Nd is less than 2%, not only the above-mentioned rise time is long, but also the absorption efficiency of the pump light 18 is reduced, so that more pump light 18 is required to obtain a high output, so that the power consumption increases. There is a disadvantage of doing. Further, if it exceeds 3%, there is a demerit that it is difficult to produce a crystal of the solid-state laser 15.

Next, a driving method when the above-described internal resonator type SHG laser 10 is used as a display light source will be described. As described above, the internal resonator type SHG laser (green light source) 10 according to the present embodiment is a force that stabilizes the output by introducing a certain output reduction time S, for display When used as a light source, the timing for inserting the output drop time is important. In the present embodiment, a case where the internal resonator type SHG laser 10 is applied to a display device using a transmissive liquid crystal panel will be described.

[0034] In the display device 1 that is effective in the present embodiment, as shown in Figs. 1 and 2, the control circuit 9 controls the light sources 2 to 4 and the transmissive liquid crystal panels 6a to 6c. . The control circuit 9 is a green light source having a laser drive unit 92 that drives and controls the green light source 3 on which the SHG laser 10 is mounted, and a liquid crystal panel drive unit 93 that drives and controls the liquid crystal panel 6b corresponding to the green light source 3. Control unit 91a. The laser driving unit 92 controls the driving current applied to the semiconductor laser 11 of the SHG laser 10 mounted on the green light source 3, and executes the above-described output reduction time. The liquid crystal panel driving unit 93 drives the liquid crystal panel 6b by outputting a video signal to the green liquid crystal panel 6b corresponding to the light emission timing of the green light source 3. Of course, the control circuit 9 is connected to each of the red light source 2 and the blue light source 4. A corresponding red light source controller 91b and blue light source controller 91c are also provided.

FIG. 6A is a diagram for explaining driving of the liquid crystal panels 6a to 6c. As shown in Fig. 6A, the liquid crystal panels 6a to 6c are driven by a non-transparent (display) in which the transmittance of the liquid crystal panel is temporarily made zero between each frame of the video signal in order to reset the liquid crystal state. In general, the transmittance of the liquid crystal panels 6a to 6c is changed in accordance with the video signal while inserting the black state. Here, if the output drop time T3 of the drive current of the pump semiconductor laser 11 of the internal cavity type SHG laser 10 is set in accordance with the non-transparent time of the liquid crystal panel 6b as shown in FIG. It is possible to eliminate flicker on the display image. Furthermore, since the amount of green light transmitted through the liquid crystal panel 6b is reliably reduced, an improvement in contrast is realized. The output drop time T3 needs to be shorter than the non-transmission time of the liquid crystal panel. A reduction in light source driving power is realized with an improvement in contrast. Reducing light source drive power means reducing power consumption and heat generation. The heat generated by the light source is a major factor in downsizing the device. Usually, it is common to increase the size of a device for heat dissipation or to provide a device with high heat dissipation capability.In this embodiment, the amount of heat generation is suppressed by inserting the output reduction time. And heat dissipation is achieved with only a small fan. In this embodiment, the output decrease time T3 is inserted every other frame, but the output decrease time T3 may be inserted every integer multiple of one frame. For example, as shown in Fig. 6C, even if the output drop time T3 is inserted once every two frames, the output stability of the internal resonator type SHG laser 10 is maintained. If it is within the range, output stability is maintained. In this case, the brightness of the display device is improved. In this embodiment, the case of a transmissive liquid crystal panel has been described. However, when a reflective liquid crystal panel or an image conversion device such as a DMD is used, it can be optimized according to the driving method of each device. It is obvious that it is good.

[0036] Similarly to the insertion of the green light output reduction time, even if a red light source or a blue light source is provided with an output reduction time that matches the non-transmission time of the liquid crystal panel, the amount of light transmitted through the liquid crystal panel is reduced. Therefore, the amount of light transmitted through the exit lens is reduced. For this reason, there is an effect that black becomes clearer and the contrast of the image is improved. The amount of heat generated by the light source can be further suppressed, and the battery driving time can be extended by reducing power consumption. [0037] According to the present embodiment, it is possible to suppress output fluctuations of harmonics without inserting a device for high-precision temperature control and fundamental wave wavelength stabilization into the resonator. Furthermore, since temperature control devices and optical components are not used to stabilize the output, it is possible to reduce costs, reduce the size of the light source, reduce power consumption, and suppress heat generation. In particular, in a three-plate display device that uses one image conversion device (liquid crystal panel) for each RGB color as in this embodiment! The output stabilization of the type SHG laser can be realized.

[0038] (Embodiment 2)

Next, Embodiment 2 of the present invention will be described. In the first embodiment described above, the output from the SHG laser is stabilized by setting the oscillation state of the fundamental wave in the internal cavity type SHG laser to the multimode oscillation in which a plurality of longitudinal modes exist. On the other hand, in this embodiment, the output from the SHG laser is stabilized by setting the oscillation state of the fundamental wave to multimode oscillation in which a plurality of transverse modes exist. Hereinafter, control of the transverse mode of the internal cavity type SHG laser according to the present embodiment will be described. The display device which is effective in the present embodiment is the same as that in the first embodiment except for the state of the horizontal mode of green light described below.

In Embodiment 1 described above, the transverse mode of the output green light (harmonic) is a circular single mode (0th order) beam, as shown in FIG. 7A. On the other hand, in this embodiment, instead of the circular opening single beam mode beam shown in FIG. Specifically, as shown in Fig. 7B and Fig. 7C, the beam was output in the form of three (primary mode) or five (secondary mode). In this way, the output variation of green light, which is a higher harmonic, can be further reduced. Normally, the force S used in the single mode (0th order) beam in Fig. 7A becomes higher, and it becomes difficult to maintain the single mode. Specifically, the transverse mode may change from the state of FIG. 7A to the state of FIG. 7D. At this time, the output of green light may vary by more than 10%. The state of FIG. 7D is close to the combination of the state of FIG. 7A and the state of FIG. 7B. The first-order transverse mode state of Fig. 7B is more likely to occur at higher output than the 0th-order single mode shape of Fig. 7A. Figure that is next + primary horizontal mode It becomes a 7D state. In this embodiment, the angle of the concave mirror of the internal cavity type SHG laser is adjusted so that green light is output in the state shown in FIG. 7D (primary mode) in advance. In this case, the change in output is small because the transverse mode does not change. In the first-order transverse mode in Fig. 7B, the output fluctuation was suppressed to 3% or less. In FIGS. 7B and 7C, the horizontal / horizontal mode is changed to the multimode, but the vertical / horizontal mode may be changed to the multimode as shown in FIG. 7E. However, in vertical and horizontal modes, it is preferable to use multimode up to the secondary mode. This is because if the multimode is further advanced than the secondary mode, the output is reduced.

[0040] According to the present embodiment, it is possible to suppress output fluctuations of harmonics without inserting a device for high-precision temperature control and fundamental wave wavelength stabilization into the resonator. Furthermore, since temperature control devices and optical components are not used to stabilize the output, it is possible to reduce costs, reduce the size of the light source, reduce power consumption, and suppress heat generation.

[Embodiment 3]

Next, Embodiment 3 of the present invention will be described. In the present embodiment, a case where the image conversion device (liquid crystal panel) is a single display device will be described. In Embodiments 1 and 2 described above, an apparatus having three image conversion devices has been described. The display device which is effective in the present embodiment displays an image by driving one image conversion device. FIG. 8 shows an outline of the display device 31 according to the present embodiment.

[0042] The display device 31, which is effective in the present embodiment, includes a red light source 32, a green light source 33, and a blue light source 34. The red light source 32 and the blue light source 34 use semiconductor lasers. The green light source 33 is an internal cavity type SHG laser and has the same configuration as that used in Embodiment 1 above. The laser beams output from the color light sources 32 to 34 are reflected by the dichroic mirror 40, pass through the homogenizing optical system 35, and enter the polarization beam splitter 37. Thereafter, the light enters the image conversion device (liquid crystal panel) 36. In the present embodiment, the reflective liquid crystal panel 36 is used as the image conversion device. The laser light incident on the reflective liquid crystal panel 36 is reflected according to the video signal input to the reflective liquid crystal panel 36, passes through the exit lens 38, and is output as an image. Outputs of the light sources 32 to 34 are controlled by a control circuit 39. In addition, the power of this embodiment The spray device 31 is provided with a battery 41 so that the battery can be driven. Compared to a display device using three image conversion devices shown in the first embodiment, the single-panel type image conversion device of this embodiment is more suitable for downsizing the display device.

FIG. 9 shows a driving method of the internal resonator type SHG laser according to the present embodiment. Figure 9 shows how to drive the pump semiconductor laser in the SHG laser. In this embodiment, since only one image conversion device is used, the video output divides one frame into three colors of red, green, and blue, and sequentially turns on each color light source 32 to 34. Therefore, the green light is lit only for 1/3 period within one frame. The pump laser diode is also lit only for 1/3 of a frame. In other words, the output of the semiconductor laser of the SHG laser mounted on the green light source 33 inevitably decreases in the period 2/3 in one frame. Therefore, the output drop time T5 is always inserted in the drive of the internal cavity type SHG laser, and the green light output from the SHG laser is used rather than the three-plate display device described in the first embodiment. The output is inherently stable.

[0044] The output P1 of the pumping semiconductor laser at the output reduction time T5 when the green light source 33 is not lit must be surely smaller than the minimum level of pumping light power Pth at which the solid-state laser oscillates. This is because when P1 exceeds Pth, green light is output, and when green light is output while the other color light sources are lit, noise is generated. Therefore, P1 = 0. In this embodiment, for the purpose of further stabilizing the green light output, as shown in FIG. 9, the pump light output from the pump semiconductor laser when the green light source 33 is turned on is divided into two stages P3 and P4. It was driven by. P3 and P4 were set so that the average output of the green light output from the SHG laser would be the desired value. As described in Embodiment 1 above, in order to stabilize the green light output, which is a harmonic, it is important to change the longitudinal mode of the fundamental wave output from the solid-state laser to multimode. . If the pump light intensity is further changed within the lighting time of the pump semiconductor laser as in this embodiment, the fundamental mode of the longitudinal mode becomes more reliable. As in the first embodiment, if P4−P3> 0.2 W or more, it contributes to the multimode. In addition, if the output drop time T4> lms, the vertical mode is easily converted to the multimode. Like this embodiment It was realized that the fluctuation of the green light output was reduced to 3% or less by driving the pump semiconductor laser with ternary output.

[0045] In this embodiment, if the condition that gives a change in pump light power of 0.2W or more and an output reduction time of lms or more when the output of the pumping semiconductor laser is made ternary, the ternary value is obtained. It is obvious that a pump semiconductor laser may be driven by setting a large pump light power. Also in the internal resonator type SHG laser in the three-plate type display device of the first embodiment, a pump light power of three or more values may be set.

[0046] In this embodiment, when using a force transmission type liquid crystal panel described in the case of a reflection type liquid crystal panel or an image conversion device such as DMD! /, Each device is driven. It is obvious that the method should be optimized and used.

[0047] According to the present embodiment, it is possible to suppress harmonic output fluctuations without inserting a device for high-accuracy temperature control and fundamental wavelength stabilization into the resonator. . In addition, since temperature control devices and optical components are not used to stabilize the output, it is possible to reduce costs, reduce the size of the light source, and reduce power consumption.

[0048] As described above, according to the first to third embodiments of the present invention, harmonics can be used without high-precision temperature control or use of a temperature control device, or insertion of optical components into the resonator. It is possible to suppress output fluctuations. In addition, since no optical components are used to stabilize the output, it is possible to reduce costs, reduce the size of the light source, and reduce power consumption. Moreover, since the power consumption of the light source can be reduced and the amount of heat generated can be reduced by inserting the output reduction time, the driving time when the apparatus is driven by a battery can be extended and heat radiation is advantageous. In addition, the contrast of the video is improved by reducing the light source output during the non-display time of the image display device.

[0049] (Embodiment 4)

Next, a fourth embodiment of the present invention will be described. In the second embodiment, the output from the SHG laser is stabilized by setting the oscillation state of the fundamental wave in the internal resonator type SHG laser to multi-mode oscillation in which a plurality of transverse modes exist. The fourth embodiment focuses on a specific configuration for making the oscillation state of the fundamental wave in the internal cavity type SHG laser into multi-mode oscillation in which a plurality of transverse modes exist. It is a form. According to the present embodiment, the oscillation state of the fundamental wave can be changed to multi-mode oscillation in which a plurality of transverse modes exist with a simple configuration without providing a complicated mechanism such as a moving mechanism or a vibration mechanism. By doing so, we will realize an internal cavity type SHG laser with excellent thermal stability and high power output.

FIG. 10 is a configuration diagram of an internal resonator type SHG laser (solid laser device) according to the fourth exemplary embodiment of the present invention. The internal resonator type SHG laser 101, which is effective in the present embodiment, is disposed inside a semiconductor laser light source 110 that emits laser light 119 for a pump, an optical resonator 114, and an optical resonator 114. And an SHG element 118 that converts the wavelength of the wave laser beam 120. The optical resonator 114 includes a solid-state laser crystal 115 that is excited by the incidence of the laser beam 119 and oscillates the fundamental laser beam 120, and mirrors 116 and 117 that are arranged at positions sandwiching the solid-state laser crystal 115, respectively. is doing. One of the mirrors 116 and 117 is arranged with an inclination angle Θ set with respect to the optical axis 122 of the laser beam 119. Of course, both the mirrors 116 and 117 may be tilted at a predetermined tilt angle with respect to the optical axis of the laser beam 119. In the present embodiment, the mirror 117 provided on the side from which the harmonic laser beam 121 converted by the SHG element 118 is emitted is a concave mirror, and this concave mirror is connected to the optical axis 122 of the laser beam 119. The tilt angle Θ is set as above. Hereinafter, the mirror 117 is referred to as a concave mirror 117. Further, the semiconductor laser light source 110 has means for fixing the oscillation wavelength of the laser light 119.

In this embodiment, pump light having a transmission wavelength of 808 nm is incident as laser light 119 to generate a fundamental laser light 120 having a wavelength of 1064 nm, and the laser light 120 is generated by a SHG element 118 with a harmonic laser light having a wavelength of 532 nm. As an example, the configuration of an internal cavity type SHG laser 101 that emits as will be described. Therefore, the harmonic laser beam 121 is G light.

[0052] In the internal resonator type SHG laser 101 which is effective in the present embodiment, the laser beam 119 is emitted from the semiconductor laser light source 110 and enters the optical resonator 114 via the rod lens 111, the VBG 112 and the ball lens 113. Is done. A laser beam 119 having a wavelength of about 808 nm emitted from the semiconductor laser light source 110 is incident on the VBG 112 after the vertical component is collimated by the rod lens 111. The laser beam 119 incident on the VBG112 The part is reflected and fed back to the semiconductor laser light source 110. As a result, the oscillation wavelength of the semiconductor laser light source 110 is locked to the wavelength (808 nm) selected by the VBG 112. As described above, by using the VBG 112, the oscillation wavelength of the semiconductor laser light source 110 can be kept substantially constant even when the temperature changes, and the highly accurate temperature control of the semiconductor laser light source 110 can be eliminated.

In the present embodiment, a force S using VBG 112 for locking the oscillation wavelength of the semiconductor laser light source 110, and a bandpass filter constituted by a dielectric multilayer film may be used. Alternatively, the semiconductor laser light source 110 itself may be a DFB (Distributed FeedBack) laser or a DBR (Distributed Bragg Reflector) laser having a wavelength lock function.

The laser beam 119 whose wavelength is locked by the VBG 112 is condensed on the solid laser crystal 115 by the Bonore lens 113. Laser light 119 becomes pump light, solid laser crystal 115 is excited, and fundamental laser light 120 having a wavelength of 1064 nm is generated. The fundamental laser beam 120 resonates in the optical resonator 114 by reciprocating between the mirror 116 provided so as to sandwich the solid laser crystal 115 and the concave mirror 117 many times. Then, the SHG element 118 disposed in the optical resonator 114 converts a part of the fundamental laser beam 120 to a wavelength, and outputs the G laser beam having a wavelength of 532 nm, which is the harmonic laser beam 121, to the outside.

In the present embodiment, YV 2 O crystal doped with 3% of Nd is used as solid laser crystal 115. In addition, as the SHG element 118, a LiNbO substrate doped with Mg

A quasi-phase-matching type with periodically domain-inverted regions formed in 4 3 was used. The LiNbO substrate doped with Mg has a large nonlinear constant, and the thickness of the SHG element 118 can be reduced.

Three

Further, as described above, the fundamental wave laser beam 120 generated by the force by which the laser beam 119 that is pump light is incident on the optical resonator 114 is confined in the optical resonator 114, and the harmonic wave from the concave mirror 117 is higher. A dielectric multilayer film is formed on each end face of the mirror 116, the SHG element 118, and the concave mirror 117 formed on the surface of the solid-state laser crystal 115 so that the wave laser beam 121 is emitted.

In the internal resonator type SHG laser 101 of the present embodiment, the concave mirror 117 has a laser The light beam 119 is arranged with a predetermined inclination angle Θ with respect to the optical axis 122. In other words, as shown in Fig. 10, the angle between the perpendicular line 123 perpendicular to the bottom of the concave surface of the concave mirror 117 and the optical axis 122 of the laser beam 119 is set as Θ, and this tilt angle Θ is set in advance. The angle is By disposing the tilt angle Θ set in this way, the width of the passing region when the fundamental laser beam 120 or the like is transmitted through the solid-state laser crystal 115 and the SHG element 118 is widened. As a result, there is no locally overheated region, the steepness of the heat distribution is improved, and a relatively gentle heat distribution can be achieved. Therefore, the occurrence of damage to the solid-state laser crystal 115 and the SHG element 118 can be suppressed, and a high output can be maintained stably for a long time.

Further, in the internal resonator type SHG laser 101 which is effective in the present embodiment, the fundamental laser beam 120 is repeatedly reflected off the optical axis 122 in the optical resonator 114. For this reason, the electric field distribution in the optical resonator 114 changes, and the harmonic laser beam 121 output from the optical resonator 114 becomes multimode oscillation in which a plurality of transverse modes exist. Therefore, similarly to the second embodiment, when it is used as a light source of a backlight unit of a liquid crystal display device, it is thin and can easily realize a large area.

FIG. 11A to FIG. 15 are diagrams showing comparison data of G light output between the internal cavity type SHG laser 101 which is effective in the present embodiment and the conventional internal cavity type SHG laser. Figure 11A shows the tilt angle Θ = 0. Fig. 11B is a schematic diagram showing the beam shape of the G light output of a conventional internal cavity type SHG laser, and Fig. 11B shows the amount of laser light that is pump light (hereinafter sometimes referred to as "pump light") It is a graph which shows the relationship between G light output. FIG. 12A shows an inclination angle Θ = 0.2 in the internal resonator type SHG laser 101 of the present embodiment. FIG. 12B is a graph showing the relationship between the amount of pump light 119 and the G light output. FIG. 13A is a schematic diagram showing the beam shape in the case of the internal cavity type SHG laser 101 of the present embodiment when the tilt angle Θ is 0.3 °, and FIG. 13B is the light amount of the pump light 119 and the G light output. It is a graph which shows the relationship. Furthermore, Fig. 14 is a graph showing the relationship between the amount of pump light 119 and the G light output when the tilt angle Θ = 0.4 °, and Fig. 15 shows the case where the tilt angle Θ = 0.5 °. FIG. 6 is a graph showing the relationship between the amount of pump light 119 and the G light output. Note that the measurements in FIGS. In this example, the resonator length L of the optical resonator 114 is 10 mm, and the radius of curvature R of the concave mirror 117 is 2 Omm.

[0059] As shown in FIG. 11A, in the case of the tilt angle Θ = 0 ° (conventional internal resonator type SHG laser), the beam shape is circular and single mode. In addition, as shown in FIG. 11B, the G light output was saturated when the light amount of the pump light 119 was around 2.5 W, and its maximum value was 0.65 W. Further, in the light amount range until the light amount of the pump light 119 is saturated, a phenomenon that the point P where the G light output decreases despite the increase of the light amount of the pump light 119 occurs. The saturation of the G light output occurs when the pump light 119 has a light intensity of about 2.5 W, and the solid laser crystal 115 generates a large amount of heat. This is because the amount of light is saturated. The decrease in output at point P is caused by interference of G light, which is the harmonic laser beam 121, inside the optical resonator 114.

In contrast, in the internal resonator type SHG laser 101 of the present embodiment, the tilt angle

Since Θ is provided! /, The above phenomenon can be suppressed.

For example, if the inclination angle Θ = 0.1 ° of the concave mirror 117 is changed, the electric field distribution in the optical resonator 114 is changed, and the transverse mode is multiplied.

[0062] Further, when the tilt angle Θ = 0.2 ° of the concave mirror 117, a transverse mode having three beams is obtained as shown in Fig. 12A. At this time, the amount of pump light 119 where output saturation of the G light output occurs was 2.8 W, and the maximum value of the G light output was also 0.7 W. Furthermore, output fluctuation due to interference of G light, which is the harmonic laser light 121 inside the optical resonator 114, has also been suppressed. This is because the heat distribution inside the solid-state laser crystal 115 is broadened compared to the single mode shown in FIGS. 11A and 11B, and the region where local overheating occurs is eliminated due to the multiple transverse modes. This results in a gentle heat distribution as a whole. When the transverse mode is multi- pleted, it becomes difficult for G light interference to occur inside the optical resonator 114, so that it is also difficult for G light output fluctuations as shown at point P in FIG. 11B to occur. Even when Θ = 0.2 °, the G light output generation efficiency (slope efficiency) with respect to the amount of pump light 119 was almost the same as that in the single mode as shown in Fig. 11B. [0063] Further, when the tilt angle Θ = 0.3 °, as shown in Fig. 13A, a transverse mode having five beams was obtained. In this case, the amount of pump light 119 where output saturation of the G light output occurs can be increased to 3 W, as shown in Fig. 13B, but the maximum value of the G light output is 0.7 W, and Θ = 0. Same as 2 °. In addition, the slope efficiency was slightly lower than when Θ = 0.2 °. This is because the conversion efficiency of the SHG element 118 is slightly lowered because the cross-sectional area of the fundamental wave laser beam 120 passing through the SHG element 118 is enlarged. Even when the tilt angle was Θ = 0.3 °, no change in the G light output was observed.

Further, as shown in FIGS. 14 and 15, when the inclination angles Θ = 0.4 ° and 0.5 ° were measured, the slope efficiency gradually decreased, but the maximum value of the G light output As the power S to get 0.7W.

[0065] As can be seen from the above results, the maximum value of the G optical output is 0.665 W in the conventional internal resonator type SHG laser that outputs a single mode, whereas the internal resonator type SHG of this embodiment is With Laser 101, it could be increased to 0.7W. As a result of measuring the beam shape and the G light output with various tilt angles Θ, the oscillation state is maintained even if the tilt angle Θ is greater than 0.5 °, but the oscillation efficiency decreases. As a result, it was found that the G light output decreased. Accordingly, it has been found that the optimum range of the inclination angle Θ is preferably Θ = 0 .;! -0.5 °. Furthermore, by setting the range of Θ = 0.2 to 0.4 °, the multiple beam shapes are relatively uniform and the maximum G light output can be obtained stably. It turned out to be more preferred.

[0066] As a result of studying various shapes of the radius of curvature R of the concave mirror 117, it was found that it becomes difficult to make a multimode if it is larger than 50 mm. Therefore, it is desirable that the radius of curvature R be 50 mm or less. The lower limit value of the radius of curvature R may be set to an optimum value depending on the configuration of the optical resonator 114, that is, the design of the resonator length L and the like.

[Embodiment 5]

Next, a fifth embodiment of the present invention will be described. The present embodiment is an embodiment relating to a display device in which the internal resonator type SHG laser of the fourth embodiment is mounted as a green light source. FIGS. 16A to 16C show the internal resonator type SHG array of Embodiment 4 above. FIG. 16A is a schematic diagram illustrating a schematic configuration of the display apparatus according to the present embodiment using the same, FIG. 16A is a perspective view thereof, FIG. 16B is a plan view viewed from the image conversion device 131 side, and FIG. FIG. 16B is a cross-sectional view taken along line 5A-5A in FIG. 16B. In FIGS. 16A to 16C, in order to make it easy to understand the respective configurations, the forces are arranged separately. In the actual configuration, they are installed on a base plate (not shown) and fixed as a whole. .

[0068] As shown in FIGS. 16A to 16C, a display device 130 that is effective in the present embodiment basically has an image conversion device 131 and an illumination light source 140 for irradiating the image conversion device 131. And. The image conversion device 131 is composed of a liquid crystal display panel, and the illumination light source 140 is a backlight unit that irradiates the entire surface of the liquid crystal display panel 131 with illumination laser beams 144 and 145 emitted from the R light source, the G light source, and the B light source. Is configured. Hereinafter, the illumination light source 140 will be described as the backlight unit 140, and the image conversion device 131 will be described as the liquid crystal display panel 131. In the display device 130 shown in FIGS. 16A to 16C, the internal resonator type SHG laser 101 of the fourth embodiment is used as the G light source, and the semiconductor laser light source 141 is used as the R light source and the B light source.

[0069] First, the configuration of the backlight unit 140, which is an illumination light source, will be described. The knock light unit 140 includes a semiconductor laser light source 141 in which an R light source and a B light source are integrated, and an illumination laser in which R light and B light emitted from the semiconductor laser light source 141 are combined. A light guide plate 143 that emits light 144 from one main surface portion 143a. For the R light and B light, after being expanded to approximately the same size as the end face portion of the end face light guide plate 142 using a beam expander (not shown) provided in the semiconductor laser light source 141, the end face light guide plate The illumination laser beam 144 is incident on the end surface light guide plate 142 from the end surface portion of the 142. The semiconductor laser light source 141 of the present embodiment integrates a semiconductor laser light source that respectively emits R light and B light, and the R light and B light are combined and emitted as a single laser beam 144 for illumination. It is configured as follows.

[0070] The end face light guide plate 142 is provided with a semi-transmissive mirror 142a at a constant pitch, and a part of the illumination laser beam 144 having a certain spread is reflected by the semi-transmissive mirror 142a. Light is incident on the end surface 143c of the light guide plate 143, and the rest is incident on the next transflective mirror 142a. To do. Similarly, a part of the semi-transmissive mirror 142a is reflected and is incident on the end surface portion 143c of the light guide plate 143. Thereafter, the laser light 144 for illumination can be incident on the entire surface of the end surface portion 143c of the light guide plate 144 from the end surface light guide plate 142 by sequentially repeating this. The illumination laser beam 144 incident on the light guide plate 143 is reflected and scattered by the side surface portion and the other main surface portion 143b of the light guide plate 143, and the illumination laser beam 144 directed toward one main surface portion 143a is finally one main surface portion 143a. The light is emitted from the surface portion 143a.

On the other hand, the internal resonator type SHG laser 101 which is a G light source is disposed on the other end surface portion 143 d side facing the end surface portion 143 c of the light guide plate 143. In the present embodiment, three internal resonator type SHG lasers 101 are arranged on the other end surface portion 143d side, and these internal resonator type SHG lasers 101 cover the entire surface of the other end surface portion 143d of the light guide plate 143. G light, that is, illumination laser light 145 can be incident. Then, the illumination laser beam 145 incident on the light guide plate 143 is transmitted from the side surface portion of the light guide plate 143 and the other main surface portion 143b in the same manner as the illumination laser beam 144 obtained by combining the R light and the B light. The reflected and scattered light is directed toward one main surface portion 143a, and finally, the illumination laser beam 145 is emitted from the one main surface portion 143a. As a result, illumination laser beams 144 and 145 composed of R light, B light, and G light are emitted with uniform brightness from the entire surface of one main surface portion 143a of the light guide plate 143.

Next, the configuration of the liquid crystal display panel 131 will be described. The liquid crystal display panel 131 has a transmissive or transflective configuration, for example, a TFT active matrix configuration, and the display area includes a red pixel portion (R subpixel) R and a green pixel portion as shown in FIG. 16B. (G subpixel) A large number of pixels with G and blue pixel part (B subpixel) B as one pixel 135 are provided and driven by TFT. A liquid crystal 133 is provided between the two glass substrates 132 and 134, and a TFT for driving the liquid crystal 133 is formed on one of the glass substrates 132 and 134. . Further, polarizing plates 136 and 137 are provided on the respective surfaces of the glass substrates 1 32 and 134. As described above, the liquid crystal display panel 131 of the present embodiment has the same configuration as that conventionally used, and thus further description thereof is omitted.

[0073] The display device 130, which is effective in the present embodiment, is an internal resonator type SHG that is a G light source. Since the laser 101 is in the transverse mode and the multimode, the laser beam can be easily spread in the length direction of the other end surface portion 143d of the light guide plate 143. As a result, the configuration of the display device 130, in particular, the configuration of the backlight unit 140 can be simplified.

[0074] (Embodiment 6)

Next, Embodiment 6 of the present invention will be described. In the present embodiment, as in the fifth embodiment described above, the present embodiment is a form that works on a display device in which the internal resonator type SHG laser of the fourth embodiment is mounted as a green light source. FIGS. 17A and 17B are schematic diagrams showing a schematic configuration of a display apparatus that uses the internal cavity type SHG laser according to the above-described Embodiment 4 and that can be applied to the present embodiment. FIG. 17A shows an illumination. FIG. 17B is a plan view seen from the light source 151 side, and is a cross-sectional view taken along line 6A-6A in FIG. 17A. The display device 150 according to the present embodiment also includes an image conversion device 131 and an illumination light source 151 for irradiating the image conversion device 131 as a basic configuration. The image conversion device 131 includes a liquid crystal display panel, and the illumination light source 151 includes a backlight unit that irradiates the entire surface of the liquid crystal display panel with illumination laser light 162 emitted from the R light source, the G light source, and the B light source. Hereinafter, the power to explain that the illumination light source 151 is the backlight unit 151 and the image conversion device 131 is the liquid crystal display panel 131. Since the liquid crystal display panel 131 is the same as the display device 130 of the fifth embodiment, the description is omitted. To do. In the display device 150 shown in FIGS. 17A and B, the internal cavity type SHG laser of the above-described Embodiment 4 is used as the G light source, and the transverse mode laser light having three beams as shown in FIG. 12A. Is used. The R light source and the B light source use semiconductor laser light sources 152 and 153. The semiconductor laser light sources 152 and 153 are provided with a plurality of active layers, and like the internal resonator type SHG laser of the G light source, It is configured to emit three beams.

Next, the configuration of the backlight unit 151 used in the display device 150 will be described. The backlight unit 151 is disposed on the back side of the liquid crystal display panel 131, and its shape is substantially the same as the shape of the liquid crystal display panel 131. The R light, B light, and G light emitted from the semiconductor laser light sources 152 and 153 and the internal cavity type SHG laser 101 are combined by the dichroic mirror 154 to become the illumination laser light 162, which is reflected by the reflection mirror. Is incident on 155. The illumination laser light 162 reflected by the reflection mirror 155 is spread by the microlens array 156 and enters the light guide plate 161 for the conversion unit. The illumination laser beam 162 incident on the conversion unit light guide plate 161 is reflected and diffused by the outer peripheral surface and is incident on the optical path conversion unit 160. The traveling direction of the laser beam 162 is changed, and the first guide of the end surface incident type light guide plate 157 is converted. Incident on the optical plate 158. Then, the illumination laser light 162 is reflected and diffused in the first light guide plate 158 and enters the second light guide plate 159. The illumination laser light 162 is further diffused by the second light guide plate 159 to have a uniform luminance distribution over the entire surface, and then is emitted from the second light guide plate 159 to illuminate the liquid crystal display panel 131. Thereby, the liquid crystal display panel 131 is illuminated and an image is displayed.

[0076] In the display device that is effective in the present embodiment, the R light, B light, and G light emitted from the semiconductor laser light sources 152, 153 and the internal resonator type SHG laser 101 are transmitted from the light guide plate 161 for the converter. It has three beams each in a direction parallel to the surface. Therefore, it is possible to spread the illumination laser beam 162 with a simpler optical system than before and to make it incident on the entire surface of the light guide plate 161 for the conversion section, and to easily realize a large-screen display device. Furthermore, speckle noise can be effectively reduced.

[0077] (Embodiment 7)

Next, Embodiment 7 of the present invention will be described. In the present embodiment, as in the fifth and sixth embodiments described above, the present embodiment is a form that works on a display device in which the internal resonator type SHG laser of the fourth embodiment is mounted as a green light source. FIGS. 18A and 18B are schematic diagrams showing a schematic configuration of a display device according to the present embodiment using the internal cavity type SHG laser according to the fourth embodiment, and FIG. 18A shows an illumination light source 171. 18B is a cross-sectional view taken along the line 7A-7A in FIG. 18A. The display device 170 that is effective in the present embodiment also includes an image conversion device 131 and an illumination light source 171 for irradiating the image conversion device 131 as a basic configuration. The image conversion device 131 is composed of a liquid crystal display panel, and the illumination light source 171 is composed of a backlight unit that irradiates the entire surface of the liquid crystal display panel with illumination laser light 177 emitted from the R light source, G light source, and B light source. . Hereinafter, the illumination light source 171 is described as the backlight unit 171 and the image conversion device 131 is described as the liquid crystal display panel 131. Since 1 is the same as that described in the fifth embodiment, the description thereof is omitted.

[0078] In display device 170, which is effective in the present embodiment, as shown in Figs. 18A and B, the internal cavity type SHG laser of the above-described Embodiment 4 is used as the G light source, and the configuration shown in Fig. 12A is shown. A laser that emits a transverse mode laser beam having three beams is used. The R light source and the B light source use the power S that uses a semiconductor laser light source, and the R light source and the semiconductor laser light source that is the B light source are provided with a plurality of active layers. Like a laser, it is configured to emit three beams. In the display device 170 which is effective in the present embodiment, the R light source, the semiconductor laser light source that is the B light source, and the internal resonator type SHG laser that is the G light source are mounted on one mounting substrate (not shown). The R light, G light, and B light are all emitted from a relatively small area. Hereinafter, this is referred to as an integrated light source 172.

[0079] The R light, G light, and B light emitted from the integrated light source 172 are guided to the optical path conversion unit 173 disposed at each of the four corners of the corner end surface incident light guide plate 174, and the optical path is converted. Then, the light is incident on the first light guide plate 175 of the corner end face incident type light guide plate 174. As shown in FIG. 18A, the first light guide plate 175 of the corner end surface incident light guide plate 174 has four corners added to a curved surface shape, and the optical path conversion unit 173 is set to a shape along this curved surface shape. Has been. By doing so, the laser light can be emitted from the second light guide plate 176 by diffusing the laser light over the entire corner end face incident type light guide plate 174, and emitted.

Hereinafter, the configuration of the backlight unit 171 used in the display device 170 that is effective in the present embodiment will be described. The backlight unit 171 includes a first light guide plate 175 in which all corners of the four corners are processed into a curved shape, and a corner end surface including the second light guide plate 176 disposed in close contact with the first light guide plate 175. An incident light guide plate 174, an optical path conversion unit 173 arranged along the curved surface formed at the corner of the first light guide plate 175, an integrated light source 172 that makes laser light incident on the optical path conversion unit 173, and , Comprising. The backlight unit 171 is disposed on the back side of the liquid crystal display panel 131.

[0081] The R light, B light, and G light emitted from the integrated light source 172 are incident on the optical path conversion unit 173, and the traveling direction thereof is converted, so that the first light guide plate of the corner end face incident type light guide plate 174 is obtained. Incident on 175 The Then, R light, B light, and G light are reflected and diffused in the first light guide plate 175, enter the second light guide plate 176, and further diffused by the second light guide plate 176 to be uniform over the entire surface. After the luminance distribution is obtained, it is emitted as illumination laser light 177 to illuminate the liquid crystal display panel 131. As a result, the liquid crystal display panel 131 is illuminated and an image is displayed.

[0082] In the display device 170, which is effective in the present embodiment, the R light, the B light, and the G light emitted from the integrated light source 172 spread in the length direction of the curved surface of the optical path conversion unit 173, and therefore enter. The light can be guided over a wide area of the first light guide plate 175. In addition, since the integrated light source 172 and the optical path conversion unit 173 are provided at the four corners of the first light guide plate 175, a uniform luminance distribution can be realized by mixing these laser beams. As a result, since the liquid crystal display panel 131 can be illuminated by the illumination laser beam 177 having a uniform luminance distribution, the display device 170 that is bright and excellent in color reproducibility can be realized. Furthermore, speckle noise can be effectively reduced.

Note that, in the display device 170 that is effective in the present embodiment, the optical path conversion unit 173 and the integrated light source 172 are respectively arranged at the four corners of the first light guide plate 175. The invention is not limited to this. The optical path conversion unit 173 and the integrated light source 172 may be arranged at only one corner of the first light guide plate 175, or may be arranged at two corners, or arranged at three corners. It may be a configuration. Further, the solid-state laser device and the semiconductor laser light source that emits the R light, the B light, and the G light may be separated from the integrated light source 172. In this case, the optical path changer 173 is arranged at at least three corners, and the respective semiconductor laser light sources that emit R light and B light at each position and the internal cavity type SHG laser that emits G light. What is necessary is just to set it as the structure to arrange.

[Embodiment 8]

Next, an eighth embodiment of the present invention will be described. In the present embodiment, as in the fifth to seventh embodiments described above, the present embodiment is a form that works on a display device in which the internal resonator type SHG laser of the fourth embodiment is mounted as a green light source. FIGS. 19A and 19B are schematic views showing a schematic configuration of the display device according to the present embodiment using the internal cavity type SHG laser according to the _fourth embodiment, and FIG. 19A shows the illumination light source 181 side. FIG. 19B is a cross-sectional view taken along the line 8A-8A in FIG. 19A. In this embodiment As a basic configuration, the power display apparatus 180 includes an image conversion device 131 and an illumination light source 181 for irradiating the image conversion device 131. The image conversion device 131 includes a liquid crystal display panel, and the illumination light source 181 includes a backlight unit that irradiates the entire surface of the liquid crystal display panel with an illumination laser beam 185 emitted from the R light source, the G light source, and the B light source. Hereinafter, the power to explain that the illumination light source 181 is the backlight unit 181 and the image conversion device 131 is the liquid crystal display panel 131. The liquid crystal display panel 131 is the same as that described in the fifth embodiment. Description is omitted.

[0085] In display device 180, which is effective in the present embodiment, as shown in FIGS. 19A and 19B, the internal cavity type SHG laser of the above-described Embodiment 4 is used as the G light source, as shown in FIG. 12A. A laser that emits a transverse mode laser beam having three beams is used. The R light source and the B light source use the power S that uses a semiconductor laser light source, and the R light source and the semiconductor laser light source that is the B light source are provided with a plurality of active layers. Like a laser, it is configured to emit three beams. Also in the display device 180 which is effective in this embodiment, the semiconductor laser light source as the R light source and the B light source and the internal resonator type SHG laser as the G light source are on one mounting board (not shown). The integrated light source 172 is used, which is mounted closely so that R light, G light, and B light are emitted from a relatively small area. The integrated light source 172 is disposed at a position facing the curved surface portions 183a formed at the four corners of the first light guide plate 183 constituting the corner end face incident type light guide plate 182. Then, R light, G light, and B light emitted from the integrated light source 172 are incident on the first light guide plate 183 from the curved surface portion 183a. The R light, G light, and B light incident on the first light guide plate 183 are further diffused by the second light guide plate 184 and emitted as illumination laser light 185 to illuminate the liquid crystal display panel 131.

[0086] The configuration of the backlight unit 181 used in the display device 180 that focuses on the present embodiment will be described below. The backlight unit 181 includes a first light guide plate 183 and a second light guide plate 184 disposed in close contact with the first light guide plate 183 having curved surfaces 183a having concave shapes at all corners of the four corners. The corner end face incident type light guide plate 182 and the first light guide plate 183 are arranged at positions facing the curved surface portion 183a, and the laser light is incident on the first light guide plate 183 through the curved surface portion 183a. Or a light source 172 It becomes. The backlight unit 181 is disposed on the back side of the liquid crystal display panel 131.

[0087] The R light, B light, and G light emitted from the integrated light source 172 are incident on the first light guide plate 183 from the curved surface portion 183a of the first light guide plate 183. In this case, the R light source and the B light source use a semiconductor laser light source that emits three beams by providing a plurality of active layers, and the internal resonator type SHG laser of the G light source also emits three beams. Since it is configured to emit, when these laser beams are incident from the curved surface portion 183a, they are spread over the entire surface of the first light guide plate 183, and are reflected and diffused. Further, these laser beams are incident on the second light guide plate 184 and further diffused by the second light guide plate 184 to obtain a uniform luminance distribution over the entire surface, and then emitted as illumination laser light 185. The liquid crystal display panel 131 is illuminated. As a result, the liquid crystal display panel 131 is illuminated and an image is displayed.

[0088] In the display device 180 that is effective in the present embodiment, the R light, B light, and G light emitted from the integrated light source 172 are incident from the curved surface portion 183a of the first light guide plate 183. As a result of the change of the optical path due to refraction or the like due to 183a, the light can be guided over a wide area of the first light guide plate 183. In addition, since the integrated light source 172 is provided at the four corners of the first light guide plate 183, the laser light 185 for illumination having a more uniform luminance distribution can be emitted by mixing the laser light from these. As a result, since the liquid crystal display panel 131 can be illuminated by the illumination laser beam 185 having a uniform luminance distribution, the display device 180 that is bright and excellent in color reproducibility can be realized. Furthermore, the power S can effectively reduce speckle noise.

[0089] In the case of the display device 180 that is effective in the present embodiment, the curved portions 183a are provided at the respective corners of the four corners of the first light guide plate 183, and the integrated light source 172 is provided at a position facing the curved portions. However, the present invention is not limited to this. The curved surface portion 183a may be provided on only one corner of the first light guide plate 183, and one integrated light source 172 facing the curved surface portion 183a may be disposed. Alternatively, the curved surface portion 183a may be provided at the two corner portions, and the integrated light source 172 may be disposed at a position opposite to the curved surface portion 183a. Alternatively, the curved surface portion 183a may be provided at three corners, and the integrated light source 172 may be disposed at a position facing these. In addition, the integrated light source 172 emits R, B, and G light. The body laser light source and the internal cavity type SHG laser may be separated. In this case, a curved surface portion 183a is provided at at least three corners, and a semiconductor laser light source that emits R light and B light and an internal cavity type SHG laser that emits G light are respectively provided at positions facing these. If you have a configuration to arrange!

[0090] (Embodiment 9)

Next, Embodiment 9 of the present invention will be described. The present embodiment is a mode that works on a projection type display device in which the internal resonator type SHG laser of the fourth embodiment is mounted as a green light source. FIG. 20 is a schematic diagram showing a schematic configuration of the projection display apparatus according to the present embodiment using the internal resonator type SHG laser of the fourth embodiment.

As shown in FIG. 20, the projection type display apparatus 190 that focuses on the present embodiment includes an image conversion device 202, 203, and 204 and an illumination for irradiating the image conversion device 202, 203, and 204. The illumination light source includes an R light source 191, a G light source 192, and a B light source 193. The G light source 192 includes the internal cavity type SHG laser power of the fourth embodiment. The R light source 191 and the B light source 193 are semiconductor laser light sources, and have a configuration in which a plurality of active layers are provided so as to emit a plurality of beams in the same manner as the internal resonator type SHG laser of the G light source 192. Furthermore, in the projection display device 190 according to the present embodiment, the image conversion devices 202, 203, and 204 are composed of a transmissive liquid crystal display panel that is a kind of two-dimensional spatial modulation device, and constitute an illumination light source. The R light source 191, the G light source 192, and the B light source 193 are arranged corresponding to the laser light emitted from the light source 193. The image light transmitted through the transmissive liquid crystal display panel is combined by the combining prism 205 and then projected. It is configured to be Hereinafter, the image conversion devices 202, 203, and 204 will be described as transmissive liquid crystal display panels 202, 203, and 204.

A more specific configuration will be described in detail with reference to FIG. R light source 191, G light source

The laser light output from the 192 and B light sources 193 is made uniform in light quantity distribution using rod integrators 194, 195 and 196, respectively. The laser light emitted from the R light source 191 and the laser light emitted from the B light source 193 are guided to the reflection mirrors 200 and 201 through the lenses 197 and 199, respectively, and the optical paths are converted by the reflection mirrors 200 and 201, respectively. The transmissive liquid crystal display panel 202 204 is guided respectively. On the other hand, the laser light emitted from the G light source 192 is directly guided to the transmissive liquid crystal display panel 203 through the lens 198. The respective laser beams transmitted through the transmissive liquid crystal display panels 202 203 204 are combined by the combining prism 205, transmitted through the exit lens 206, and output as image light.

The light source control circuit 207 controls the light output of the R light source 191 G light source 192 and B light source 193. Then, the display device control circuit 208 drives each of the three transmissive liquid crystal display non-nores 202 203 204 based on the video display signal. That is, based on the video display signal, the transmissive liquid crystal display panel 202 that receives the laser light from the R light source 191 is driven corresponding to the red video signal, and the transmissive liquid crystal display panel that receives the laser light from the G light source 192. The display device control circuit 208 drives 203 corresponding to the green video signal, and the transmissive liquid crystal display panel 204 that receives one laser beam from the B light source 193 drives the blue video signal.

[0094] The display device control circuit 208 may also control the light source control circuit 207 as necessary. For example, control such as stopping the oscillation of the laser light of the R light source 191 G light source 192 and B light source 193 may be performed in response to black display. Alternatively, the output of the laser light from the R light source 191 G light source 192 or B light source 193 may be varied as necessary. By performing such control, display image quality can be improved and power consumption can be reduced. Note that the transmissive liquid crystal display panels 202 203 204 can use a configuration conventionally used in a transmissive liquid crystal display device, for example, a panel configuration provided with a polysilicon TFT driving circuit, and the description thereof will be omitted.

[0095] The projection type display device 190, which is effective in the present embodiment, is capable of displaying colors because the light of each RGB light source is monochromatic light and has good color purity! /, And using a laser light source! / The range can be expanded and a vivid image with high color purity can be displayed. In addition, the power consumption can be reduced compared to the case where a lamp is used as the light source. In addition, since a multi-beam internal resonator SHG laser and a semiconductor laser light source are used, the optical system can be simplified and a low-cost display device can be realized.

[0096] In the display device of the present embodiment, a laser light source that emits R light, G light, and B light is used. However, a laser light source that emits another color may be added. Further, the internal cavity type SHG laser of the present invention is not limited to the configuration of the display device of the present embodiment, and can be applied without particular limitation as long as it is used for illumination of a display device.

[0097] As described above, according to Embodiments 4 to 9 of the present invention, damage to the solid-state laser crystal and the wavelength conversion element can be prevented, and the internal cavity type SHG laser with a long life and high output can be obtained. One effect is achieved. In addition, this internal cavity type SHG laser has a multi-mode transverse mode! /. Therefore, when used as a light source for a backlight unit of a liquid crystal display device, the structure is simple, and power and manufacturing cost are reduced. If an image display device that can be made cheap is realized, it will have a great effect!

The present invention can be summarized from the above embodiments as follows. That is, a display device according to the present invention sandwiches a semiconductor laser that emits an excitation laser beam, a solid laser that is excited by the incidence of the excitation laser beam and oscillates and emits a fundamental laser beam, and the solid laser. A resonator having first and second mirrors arranged as described above, a wavelength conversion element that is arranged inside the resonator and converts the fundamental laser light into harmonic laser light, and the harmonic laser light The semiconductor laser is driven so that the output of the harmonic laser light decreases at an integer multiple of the frame period of the video signal applied to the image display element and the image signal applied to the image display element. A laser driving unit.

[0099] In the above display device, the longitudinal mode of the oscillation state of the harmonic laser beam is changed to the multimode due to the decrease in the output of the harmonic laser beam in the period that is an integral multiple of the frame rate of the video signal. For this reason, the output of the harmonic laser beam is stabilized, the disturbance of the color balance of the image due to the unstable output of the harmonic laser beam is suppressed, and a high-quality image can be displayed.

[0100] It is preferable that the period during which the output of the harmonic laser beam decreases is included in a period during which the image display element is in a non-display state between consecutive frames of the video signal.

[0101] In this case, the output of the harmonic laser light does not decrease during the image display, and the display image is not affected by the decrease in the output of the harmonic laser light. [0102] The period during which the output of the harmonic laser beam decreases is preferably 1 ms or more.

Yes

[0103] In this case, since the oscillation of the fundamental laser beam by the solid-state laser is reliably stopped, the force S can be realized more stably to achieve the multimode of the longitudinal mode of the harmonic laser beam oscillation state. .

[0104] The repetition frequency of the output reduction of the harmonic laser beam is preferably 2 Hz or more.

[0105] In this case, the oscillation of the fundamental laser beam by the solid-state laser is surely stopped, so the force S can be realized more stably to realize the multimode of the longitudinal mode of the oscillation state of the harmonic laser beam. .

[0106] The output of the semiconductor laser is modulated to a predetermined low output value during a second predetermined time T2 at intervals of the first predetermined time T1, and the first predetermined time T1 and the second predetermined time T2 are modulated. The given time T2 is preferably Tl <0.5s, T2> 1ms! /.

[0107] In this case, it is possible to stably realize the multimode of the longitudinal mode of the oscillation state of the harmonic laser beam without affecting the image display of the image display element by the irradiation of the harmonic laser beam.

[0108] The output of the semiconductor laser is alternately modulated between a first output value P1 and a second output value P2, and the first output value P1 and the second output value P2 are P2> Preferably, the relationship of P1 is satisfied, and the repetition frequency of modulation between the first output value P1 and the second output value P2 is 1 kHz or less.

In this case, there is no need for loss of the driving current for driving the semiconductor laser by the laser driving unit, generation of electromagnetic waves due to the driving current, countermeasures against noise due to the electromagnetic waves, etc., and the laser driving unit can be realized with a simple configuration.

[0110] It is preferable that the first output value P1 and the second output value P2 satisfy a relationship of P2-P1> 0.2 watts.

[0111] In this case, the longitudinal mode of the harmonic laser beam oscillation state can be more effectively realized.

[0112] The first output value P1 is less than or equal to the oscillation threshold excitation light power Pth of the solid-state laser. Preferably there is.

[0113] In this case, the generation of the harmonic laser light is surely stopped during the period in which the output of the harmonic laser light is reduced. For this reason, power consumption by the solid laser can be reduced by the amount of the stoppage.

[0114] The output of the semiconductor laser is alternately modulated between a third output value P3 and a fourth output value P4 so that an average output of the harmonic laser beam becomes a desired value, The output value P3 of 3 and the fourth output value P4 satisfy the relationship of P4> P3 force, P4—P3> 0.2 watts, and the output time T3 of the third output value P3 is T3> lms It is preferable that

[0115] In this case, it is possible to more effectively realize the longitudinal mode multimode of the oscillation state of one harmonic laser light while maintaining the average output of the harmonic laser light at a desired value.

[0116] The laser medium of the solid-state laser is an Nd: YVO crystal, and the Nd: YVO crystal

The Nd doping amount of 4 4 crystals is preferably 2 to 3%.

[0117] In this case, the output of the harmonic laser beam can be improved again in a shorter time. For this reason, the excitation laser beam required for raising the output of the harmonic laser beam is reduced, and as a result, the power consumption by the semiconductor laser can be reduced.

[0118] A red light source that emits red light, a red image display element that displays an image by irradiating the red light, a blue light source that emits blue light, and a blue that displays an image by irradiating the blue light And the harmonic laser light is green light, the image display element is a green image display element, and the video light is output during a period when the output of the green light is reduced. It is preferable that the green image display element is included in a non-display state between consecutive frames of signals.

[0119] In this case, since the output of green light decreases in accordance with the non-display state of the green image display element, it is possible to prevent flickering on the display image. Furthermore, since the amount of green light transmitted through the green image display element is surely reduced, the contrast is improved and the driving power by the laser driving unit is also reduced.

[0120] A red light source driving unit that drives the red light source so that the output of the red light decreases at a cycle that is an integral multiple of a frame rate of a video signal applied to the red image display element, and the blue image Period that is an integral multiple of the frame rate of the video signal applied to the display element A blue light source driving unit that drives the blue light source so that the output of the blue light is reduced, and a video signal applied to the red image display element during a period in which the output of the red light is reduced Of the video signal applied to the blue image display element is included in a period in which the red image display element is in a non-display state between successive frames of It is preferable that the blue image display element is included in a period during which the blue image display element is not displayed between successive frames.

[0121] In this case, the output of red light and blue light also decreases in accordance with the non-display state of each image display element, so that black in the non-display state becomes clearer and the contrast of the image is improved. The amount of heat generated by each light source can be further suppressed, and power consumption is reduced.

[0122] The apparatus further includes a red light source that emits red light and a blue light source that emits blue light, wherein the harmonic laser light is green light, and the image display element is one frame of the video signal. The image by the red light irradiation, the image by the blue light irradiation and the image by the green light irradiation are sequentially displayed in a frame, and the period during which the output of the green light is reduced is within one frame of the video signal. It is preferable that it is a period in which the red light and blue light are irradiated.

[0123] In this case, since the output of the green light is stopped during the period in which the red light and the blue light are irradiated, there is a period in which the output of the green light is surely reduced without performing a special drive by the laser driving unit. appear. For this reason, a laser drive part is realizable by simple structure.

[0124] The output of the semiconductor laser is between two output values so that the average output of the green light in a period in which the green light is irradiated in one frame of the video signal becomes a desired value. It is preferred that they are modulated alternately.

[0125] In this case, it is possible to more effectively realize the longitudinal mode of the green light oscillation state while maintaining the average output of the green light at a desired value.

[0126] The transverse mode of the oscillation state of the harmonic laser beam is preferably a multimode.

[0127] In this case, the output of the harmonic laser beam is more effectively stabilized by changing the transverse mode of the oscillation state of the harmonic laser beam to the multimode.

[0128] The order of the transverse mode is preferably 2nd order or less. [0129] In this case, the output of the harmonic laser beam is not reduced.

[0130] It is preferable that at least one of the first and second mirrors is disposed so as to form a predetermined inclination angle with respect to an optical axis of the fundamental laser beam.

[0131] In this case, the transverse mode of the oscillation state of the harmonic laser beam can be converted into a multimode more effectively. For this reason, the region through which the laser beam passes in the solid laser or the wavelength conversion element is expanded, and the region that generates heat is expanded accordingly. As a result, it is possible to prevent a region where the temperature is locally high, and to output the harmonic laser light stably with high output.

[0132] The first mirror is disposed on the semiconductor laser side of the solid-state laser, the second mirror is disposed on the wavelength conversion element side of the solid-state laser, and the second mirror is A concave mirror is preferred.

[0133] In this case, the transverse mode can be changed to a multimode without changing the arrangement configuration of the semiconductor laser, the solid-state laser, and the wavelength conversion element.

[0134] The radius of curvature of the concave mirror is preferably 50 mm or less.

In this case, the transverse mode can be changed to a multimode without changing the arrangement configuration of the semiconductor laser, the solid-state laser, and the wavelength conversion element.

[0136] The predetermined inclination angle is preferably in the range of 0.;! To 0.5 °.

[0137] In this case, the transverse mode can be changed to a multimode without changing the arrangement configuration of the semiconductor laser, the solid-state laser, and the wavelength conversion element.

[0138] The semiconductor laser has a fixing unit that fixes the oscillation wavelength of the excitation laser beam, and the oscillation wavelength of the semiconductor laser is fixed by the fixing unit to cause the temperature change of the semiconductor laser. It is preferable to suppress fluctuations in the oscillation wavelength of the semiconductor laser.

[0139] In this case, the oscillation wavelength of the semiconductor laser is kept substantially constant even when the temperature changes, so that it is not necessary to perform highly accurate temperature control on the semiconductor laser. An example of the fixed part is VBG, which is a transmissive diffraction grating. The laser beam emitted from the semiconductor laser is incident on the VBG, a part of which is reflected and fed back to the semiconductor laser, and is fixed at the wavelength selected by the oscillation wavelength force SVBG of the semiconductor laser. It is. Furthermore, there are DFB lasers and DBR lasers that have wavelength selectivity for semiconductor lasers, and you can use such lasers!

[0140] The transverse mode of the green light oscillation state is a multi-mode, and each of the red light source and the blue light source is a red and blue semiconductor laser, and each of the red and blue semiconductor lasers is a plurality of It is preferable that a plurality of laser beams are emitted by the stimulated emission of each of the plurality of active layers.

[0141] In this case, the horizontal mode of the green light oscillation state is changed to the multi-mode, and each of the red light and the blue light is a plurality of laser beams, so that the color reproduction range is wide and the image quality is good and the display is bright. An apparatus can be realized. In addition, as a display device, a two-dimensional spatial modulation element as an image display element, for example, a projection type display apparatus using an element in which a large number of micromirrors formed by MEMS technology are arranged, and a liquid crystal display panel are two-dimensional spatial modulation. There is a projection type display device used as an element, or a thin television configuration display device using a backlight unit and a liquid crystal display panel.

[0142] It is preferable to further include a backlight unit that receives laser light emitted from the red light source, blue light source, and green light source and irradiates the laser light from the back surface of the image display element.

[0143] In this case, even in the case of a large-screen display device such as a flat-screen TV, the color reproduction range can be expanded, and the image quality can be greatly improved. In addition, low power consumption can be realized as a whole.

[0144] The backlight unit portion includes at least one corner portion of four corners processed into a curved shape, and reflects and diffuses incident laser light to emit the first light guide plate, and the first light guide plate. A second light guide plate that is disposed in close contact with the light guide plate, reflects and diffuses laser light emitted from the first light guide plate, and emits the laser light to the image display element side; and the first light guide plate. And an optical path changing unit that is arranged along a curved surface formed at a corner, and that receives the laser light emitted from the red light source, the blue light source, and the green light source and emits the laser light to the first light guide plate. Is preferred.

[0145] In this case, a red light source, a green light source, and a blue light source are arranged on the surface of the first light guide plate. Therefore, the overall shape of the display device can be reduced, and the laser light emitted from the first light guide plate is further diffused by the second light guide plate to the image display element side. Can be emitted.

[0146] The backlight unit portion has a curved surface portion in which at least one corner portion of the four corners has a concave shape, and reflects and diffuses incident laser light to be emitted. And a second light guide plate that is disposed in close contact with the first light guide plate, reflects and diffuses one laser beam emitted from the first light guide plate, and emits the light to the image display element side. The red light source, the blue light source, and the green light source are arranged at positions facing the curved surface portion of the first light guide plate, and the laser light emitted from the red light source, the blue light source, and the green light source. Is preferably incident on the first light guide plate by being reflected by the curved surface portion.

[0147] In this case, laser light can be directly incident on the first light guide plate from the curved surface portion of the first light guide plate without providing an optical path conversion unit, so that a large screen can be obtained while simplifying the configuration of the optical system. The laser light emitted from the first light guide plate can be further diffused by the second light guide plate and emitted to the image display element side.

Industrial applicability

[0148] The display device which is effective in the present invention is useful as a projector.

Claims

The scope of the claims

[1] a semiconductor laser that emits excitation laser light;

A resonator having a solid-state laser that is excited by incidence of the excitation laser beam and oscillates and emits a fundamental laser beam, and first and second mirrors disposed so as to sandwich the solid-state laser;

A wavelength conversion element that is disposed inside the resonator and converts the fundamental laser beam into a harmonic laser beam;

An image display element that displays an image by irradiation of the harmonic laser beam, and the semiconductor so that the output of the harmonic laser beam decreases at a period that is an integral multiple of a frame period of a video signal applied to the image display element. A laser that drives the laser

A display device comprising:

[2] The period in which the output of the harmonic laser beam is reduced is included in a period in which the image display element is not displayed between consecutive frames of the video signal. Item 4. The display device according to Item 1.

[3] The display device according to claim 1 or 2, wherein a period during which the output of the harmonic laser beam is reduced is 1 ms or more.

[4] The display device according to claim 1 or 2, wherein a repetition frequency of the output decrease of the harmonic laser beam is 2 Hz or more.

[5] The output of the semiconductor laser is a second predetermined time T for each interval of the first predetermined time T1.

Between 2 and modulated to a predetermined low output value,

3. The display device according to claim 1, wherein the first predetermined time T1 and the second predetermined time T2 satisfy TK O.5s and T2> lms.

[6] The output of the semiconductor laser is alternately modulated between the first output value P1 and the second output value P2,

The first output value P1 and the second output value P2 satisfy the relationship P2> P1, and the repetition frequency of modulation between the first output value P1 and the second output value P2 is The display device according to claim 1, wherein the display device is 1 kHz or less.

7. The display device according to claim 6, wherein the first output value PI and the second output value P2 satisfy a relationship of P2−PI> 0.2 watts.

[8] The display device according to claim 6 or 7, wherein the first output value P1 is equal to or less than an oscillation threshold excitation light power Pth of the solid-state laser.

[9] The output of the semiconductor laser is alternately modulated between the third output value P3 and the fourth output value P4 so that the average output of the harmonic laser beam becomes a desired value,

The third output value P3 and the fourth output value P4 satisfy the relationship of P4> P3 force, P4-P3> 0.2 watts,

3. The display device according to claim 1, wherein an output time T3 of the third output value P3 is T3> lms.

[10] The laser medium of the solid-state laser is an Nd: YVO crystal,

Four

The Nd doping amount of the Nd: YVO crystal is 2 to 3%.

Four

The display device according to any one of the above.

[11] A red light source that emits red light, a red image display element that displays an image by irradiating the red light, a blue light source that emits blue light, and a blue that displays an image by irradiating the blue light An image display element for use,

The harmonic laser beam is green light, and the image display element is a green image display element,

2. The period in which the output of the green light decreases is included in a period in which the green image display element is in a non-display state between consecutive frames of the video signal. Display device.

[12] A red light source driving unit that drives the red light source so that an output of the red light decreases at a cycle that is an integral multiple of a frame rate of a video signal applied to the red image display element, and the blue image A blue light source drive unit that drives the blue light source so that the output of the blue light decreases at a cycle that is an integral multiple of the frame rate of the video signal applied to the display element,

During the period in which the output of the red light decreases, the red image display element is not displayed between successive frames of the video signal applied to the red image display element. Included in the period

The period during which the output of the blue light is reduced is included in a period in which the blue image display element is set in a non-display state between successive frames of the video signal applied to the blue image display element. The display device according to claim 11, wherein

[13] The apparatus further includes a red light source that emits red light and a blue light source that emits blue light, the harmonic laser light is green light, and the image display element is within one frame of the video signal. And sequentially displaying the image by irradiation with the red light, the image by irradiation with the blue light and the image by irradiation with the green light,

2. The display device according to claim 1, wherein the period during which the output of the green light decreases is a period during which the red light and blue light within one frame of the video signal are irradiated.

[14] The output of the semiconductor laser is between two output values so that the average output of the green light during a period in which the green light within one frame of the video signal is irradiated becomes a desired value. 14. The display device according to claim 13, wherein the display device is alternately modulated.

15. The display device according to claim 1, wherein the transverse mode of the oscillation state of the harmonic laser beam is a multimode.

16. The display device according to claim 15, wherein the order of the transverse mode is 2nd order or less.

[17] The at least one of the first and second mirrors is arranged so as to form a predetermined tilt angle with respect to an optical axis of the fundamental laser beam. A display device according to 1.

[18] The first mirror is disposed on the semiconductor laser side of the solid-state laser, and the second mirror is disposed on the wavelength conversion element side of the solid-state laser,

18. The display device according to claim 17, wherein the second mirror is a concave mirror.

19. The display device according to claim 18, wherein a radius of curvature of the concave mirror is 50 mm or less.

[20] The predetermined inclination angle is in a range of 0.;! To 0.5 °. Or the display apparatus of 19.

[21] The semiconductor laser has a fixing portion for fixing an oscillation wavelength of the excitation laser light,

21. The force according to any one of claims 1 to 20, wherein fluctuations in the oscillation wavelength of the semiconductor laser caused by temperature changes of the semiconductor laser are suppressed by fixing the oscillation wavelength of the semiconductor laser by the fixing portion. The display device according to 1 above.

[22] The transverse mode of the green light oscillation state is a multi-mode,

Each of the red light source and the blue light source is a red and blue semiconductor laser, and each of the red and blue semiconductor lasers has a plurality of active layers, and each of the plurality of active layers emits a plurality of stimulated emissions. The display device according to claim 11, wherein the display device emits laser light.

[23] The apparatus further comprises a backlight unit that receives laser light emitted from the red light source, blue light source, and green light source and irradiates the laser light from the back surface of the image display element. 23. A display device according to claim 22.

[24] The backlight unit section includes:

A first light guide plate in which at least one corner portion of the four corners is processed into a curved shape, and reflects and diffuses incident laser light; and

A second light guide plate that is disposed in close contact with the first light guide plate, reflects and diffuses laser light emitted from the first light guide plate, and emits the laser light to the image display element side;

Laser light emitted from the red light source, the blue light source, and the green light source is incident and emitted to the first light guide plate, arranged along a curved surface formed at the corner of the first light guide plate. With optical path changer

24. The display device according to claim 23, comprising:

[25] The backlight unit section includes:

A first light guide plate that has a concave curved surface at least one corner of the four corners, and reflects and diffuses incident laser light; and

A second light guide plate that is disposed in close contact with the first light guide plate and reflects and diffuses laser light emitted from the first light guide plate and emits the laser light to the image display element side; Have

The red light source, the blue light source, and the green light source are disposed at positions facing the curved surface portion of the first light guide plate,

24. The display device according to claim 23, wherein the laser light emitted from the red light source, the blue light source, and the green light source is incident on the first light guide plate by being reflected by the curved surface portion.