JP2010097743A - Light source device, and image display device provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light source device, capable of efficiently extracting generated light, and an image display device provided with the same. <P>SOLUTION: The light source device 1 includes a microwave generation part 2 which emits microwave; a light emission part 3 which emits light by the microwave 100a emitted from the microwave generation part 2; and a focusing part 4 which focuses the microwave emitted from the generation part 2 to the light emission part 3. The focusing part 4 includes a concave reflecting member 81 which reflects the microwave emitted from the generation part 2, and a convex reflecting member 82 which reflects the microwave reflected by the reflecting member 81 so as to be focused on the light emission part 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, projectors are used as video projection devices in various fields such as for presentations at conferences and home theaters at home. As a light source device used for such a projector, a discharge lamp having electrodes such as a halogen lamp, a metal halide lamp, and a high-pressure mercury lamp is mainly used (for example, see Patent Document 1). However, in the light source device using electrodes such as the above-described discharge lamp, the wear and deformation of the tip of the electrode progress due to secular change with continuous use, and the arc spot moves during discharge and an arc jump occurs. It became easy and discharge became unstable. As a result, a phenomenon called illuminance fluctuation (flicker) has occurred in the projected image on the screen. In addition, there is a phenomenon that the electrode material adheres to the inner wall of the arc tube due to evaporation of the electrode material, and a phenomenon that the inner wall of the arc tube becomes cloudy and devitrified due to a partial temperature rise of the arc tube. It has occurred. Due to these phenomena, the light source device using electrodes has a problem that the lamp life is reduced.

On the other hand, an electrodeless lamp has been proposed that excites a discharge substance by radiating a high-frequency wave such as a microwave to an object (light emitting unit) in which the discharge substance is confined (see, for example, Patent Document 2). In such an excitation type lamp, in order to use it as a point light source, a configuration that radiates high frequency in a concentrated manner is important.
JP 2006-210363 A JP 2007-194011 A

  However, the prior art disclosed in Patent Document 2 may cause a part of the generated light to be reflected in the reverse direction, and provide a new configuration that can extract the generated light more efficiently. It was desired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a light source device capable of efficiently extracting generated light and an image display device including the same.

  In order to solve the above-described problems, a light source device of the present invention includes a microwave generator that emits microwaves, a light-emitting unit that emits light by the microwaves emitted from the microwave generator, and the microwave generator A converging unit that focuses the microwave radiated from the light emitting unit, the converging unit reflecting the microwave radiated from the microwave generating unit, and the concave reflecting member And a convex reflection member that reflects the microwave reflected at the light emitting portion so as to be focused on the light emitting portion.

  According to the light source device of the present invention, the microwave can be focused on the light emitting unit by the concave reflecting member and the convex reflecting member. Therefore, it is possible to cause the light emitting portion to emit light satisfactorily by the focused microwave and to efficiently extract the generated light.

In the light source device, it is preferable that the concave reflecting member and the convex reflecting member are each made of a conductive material.
According to this configuration, the light emitting unit can emit light satisfactorily by causing the concave reflection member and the convex reflection member to reliably reflect the microwave without leakage.

In the light source device, the microwave generator includes a microwave radiating unit that radiates the microwave. When the wavelength of the microwave is λ, the length of the microwave radiating unit is nλ / Preferably, 4 (n is a positive integer).
Thus, by setting the length of the microwave radiating portion, the microwave can be favorably generated by the microwave generating portion.

Further, in the light source device, the light emitting unit includes a light emitting tube in which a light emitting substance that emits light by the microwave is enclosed, and the light emitting tube includes a light emitting region having a spherical shape with an inner diameter of approximately 1 mm to 2 mm. Is preferred.
According to this configuration, the arc tube can emit light in a light emitting region having a spherical shape with an inner diameter of approximately 1 mm to 2 mm, and approaches a so-called point light source. Can be emitted.

In the light source device, the arc tube is preferably formed of quartz, transparent sapphire, or translucent ceramic.
As described above, the arc tube is formed of any one of quartz, transparent sapphire, and translucent ceramic, whereby the light transmittance and heat resistance of the arc tube can be improved.

In the light source device, the light emitting unit preferably further includes a reflector unit that emits light emitted from the arc tube in a substantially constant direction.
According to this configuration, the light emitted from the arc tube can be efficiently emitted in a substantially constant direction by the reflector portion.

  An image display device according to the present invention is formed by the light source device described above, a light modulation unit that modulates a light beam emitted from the light source device according to input image information to form an optical image, and the light modulation unit. A projection unit for projecting the optical image.

  According to the image display device of the present invention, since the light source device having high light use efficiency is provided as described above, an image display device excellent in contrast and brightness can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

FIG. 1 is a schematic diagram showing a configuration of a light source device according to the present embodiment. The light source device shown in FIG. 1 has a schematic cross-sectional structure. FIG. 2 is a block diagram of the microwave generator.
As shown in FIG. 1, the light source device 1 includes a microwave generating unit 2 that emits microwaves, a light emitting unit 3 that emits light by microwaves emitted from the microwave generating unit 2, and the microwave generating unit. And a focusing unit 4 that focuses the microwaves radiated from 2 onto the light emitting unit 3.

  As shown in FIG. 2, the microwave generator 2 includes a solid-state high-frequency oscillator 110 that outputs a high-frequency signal, and a waveguide unit 120 that emits the high-frequency signal output from the solid-state high-frequency oscillator 110 as a microwave. It is configured.

  The solid-state high-frequency oscillator 110 includes a power source 111, a diamond SAW oscillator 202 as a surface acoustic wave (SAW) oscillator 201, which is a solid-state high-frequency oscillator 200, and a first amplifier 112 as an amplifier. Is done. The waveguide unit 120 includes an antenna (microwave radiation unit) 121 and an isolator 122 as a safety device.

  The power supply 111 supplies power to the diamond SAW oscillator 202 and the first amplifier 112. In this embodiment, a diamond SAW oscillator 202 is used as the surface acoustic wave oscillator 201 that is the solid-state high-frequency oscillator 200. The subsequent stage of the diamond SAW oscillator 202 is connected to the previous stage of the first amplifier 112. The high-frequency signal output from the diamond SAW oscillator 202 is output after being amplified by the first amplifier 112. The high-frequency signal output from the first amplifier 112 becomes a high-frequency signal output from the solid-state high-frequency oscillator 110. In the present embodiment, the high frequency signal in the 2.45 GHz band amplified to a high frequency output level that excites the luminescent substance enclosed in the arc tube 510 to emit light is output from the solid-state high-frequency oscillator 110. In this embodiment, since the diamond SAW oscillator 202 is used as the surface acoustic wave oscillator 201, the diamond SAW resonator 310 is used as the surface acoustic wave resonator 300 described later.

  The waveguide unit 120 guides a high-frequency signal output from the solid-state high-frequency oscillation unit 110 and radiates it as a microwave 100a. The waveguide unit 120 includes an antenna 121 that radiates the microwave 100a and an isolator 122 as a countermeasure against reflected waves. ing. In the present embodiment, the antenna 121 is configured by the axis of the coaxial cable 42 that is a transmission path of the microwave from the solid-state high-frequency oscillator 110 as shown in FIG.

  Further, the length of the antenna 121 is set to a value defined by the following equation. Here, the length of the antenna 121 is defined by the protruding amount of the axis of the coaxial cable 42. Specifically, when the wavelength of the microwave is λ, the length of the antenna 121 satisfies nλ / 4 (n is a positive integer). In this embodiment, when n = 1, λ = 12.2 cm (2.45 Hz), so the length of the antenna 121 is set to about 3 cm. By setting the length of the antenna 121 to such a value, the microwave generator 2 can radiate the microwave satisfactorily.

  Each coaxial cable 42 is composed of an inner conductor, an outer conductor covering the inner conductor, and a dielectric (insulator) interposed between the inner conductor and the outer conductor. Further, by maintaining the characteristic impedance of the coaxial cable at, for example, 50Ω, microwaves can be generated efficiently without causing loss in signal transmission.

  The isolator 122 is installed between the antenna 121 and the subsequent stage of the first amplifier 112 of the solid-state high-frequency oscillator 110. Therefore, as a result of radiating the microwave 100a from the antenna 121, the reflected waves from the concave reflecting member 81, the convex reflecting member 82, the arc tube 510 and the like that are the object are prevented from returning to the solid high-frequency oscillator 110, The failure of the first amplifier 112 is prevented.

FIG. 3 is a block diagram showing a schematic configuration of the solid-state high-frequency oscillator constituting the solid-state high-frequency oscillation unit 110.
A solid-state high-frequency oscillator 200 (in this embodiment, a diamond SAW oscillator 202 as a surface acoustic wave oscillator 201) includes a phase shift circuit 210, a diamond SAW resonator 310 as a surface acoustic wave resonator 300, a second amplifier 220, and power distribution. The loop circuit 240 is configured by the power generator 230, and the buffer circuit 250 is connected to one output side of the power distributor 230. The phase shift circuit 210 receives a control voltage from the power supply 111 and varies the phase of the loop circuit 240. These blocks are all matched and connected to a certain characteristic impedance, for example, 50 ohms. The diamond SAW resonator 310 can be connected to the input side of the second amplifier 220 so that an input voltage at which the second amplifier 220 is saturated is supplied.

  Thereby, it is possible to directly oscillate a high frequency signal in the GHz band using the diamond SAW resonator 310. Further, the output power of the second amplifier 220 can be output from the power distributor 230 to the outside via the buffer circuit 250 while maintaining matching. Also, with this circuit configuration, it is possible to continue the continuous oscillation state while minimizing the power applied to the diamond SAW resonator 310. Further, the phase shift circuit 210 can apply frequency modulation to the high-frequency signal, and the microwave frequency can be variably adjusted with respect to the arc tube 510. In this embodiment, the diamond SAW resonator 310 outputs a 2.45 GHz band high frequency signal. Further, the phase shift circuit 210 may not be used, and in that case, the solid-state high-frequency oscillator 200 becomes a fixed oscillator that oscillates at a frequency uniquely determined by the characteristics of the diamond SAW resonator 310.

  The light emitting unit 3 includes an arc tube 510, a reflector unit 530, and a support unit 540. The arc tube 510 is made of quartz glass. The arc tube 510 has a substantially spherical shape, and a light emitting region 511 having a spherical shape with an inner diameter of about 1 mm filled with a light emitting substance that emits light by microwaves is formed therein. The inner diameter of the light emitting region 511 is preferably about 1 mm to 2 mm. The arc tube 510 has an electrodeless structure in which no electrode is provided inside the light emitting region 511.

  The reflector unit 530 includes a first reflector 530A and a second reflector 530B. The first reflector 530A is for emitting light emitted from the arc tube 510 in a substantially constant direction. The second reflector 530B is for reflecting the light radiated to the front side of the arc tube 510 to the first reflector 530A. The first and second reflectors 530A and 530B are each formed of quartz glass. The first reflector 530A is formed with a hole 531 into which a first support part 541 described later can be fitted, and the microwave generated in the microwave generating part 2 is guided through the hole 531. It has become.

  Further, the first and second reflectors 530A and 530B are arranged so as to face each other so as to sandwich the arc tube 510 (so that light beam reflecting surfaces 531A and 531B described later face each other). Further, on the inner surface side of the first and second reflectors 530A and 530B, light beam reflecting surfaces 531A and 531B having a parabolic curvature corresponding to the outer surface shape of the arc tube 510 are formed, respectively. These light flux reflecting surfaces 531A and 531B are formed of a reflective film (for example, a dielectric multilayer film) that reflects the light flux.

The support part 540 includes a first support part 541 and a second support part 542. These first and second support portions 541 and 542 are each formed of quartz glass.
The first support portion 541 has one end supporting and fixing the arc tube 510 and the other end supporting and fixing to the first reflector 530A. The second support portion 542 has one end supporting and fixing the arc tube 510 and the other end supporting and fixing the second reflector 530B. Thereby, the arc tube 510 is supported in a predetermined positional relationship with respect to the reflector portion 530. With such a configuration, the reflector 530 can efficiently extract light emitted from the arc tube 510 in a substantially constant direction. The microwave generated by the microwave generating unit 2 is transmitted through the first support unit 541 made of quartz glass and is incident on the arc tube 510.

  In the present embodiment, quartz glass is used as a material for forming the arc tube 510, but a material such as transparent sapphire or translucent ceramic may be used. Thereby, the light transmittance and heat resistance of the arc tube 510 can be improved. Further, in this embodiment, mercury, a rare gas, and a small amount of halogen are encapsulated as the luminescent substance enclosed in the light emitting region 511 of the arc tube 510. For example, neon, argon, krypton, xenon, halogen, etc. A rare gas or a metal or a metal compound such as mercury or sodium may be enclosed together with these gases.

  The light source device 1 according to the present embodiment includes a converging unit 4 that focuses the microwave radiated from the microwave generating unit 2 (antenna 121) onto the light emitting unit 3. The converging unit 4 includes a concave reflecting member 81 that reflects the microwave radiated from the microwave generating unit 2 and a convex reflecting member that reflects the microwave reflected by the concave reflecting member 81 so as to converge the light emitting unit 3. 82.

  The concave reflecting member 81 is made of a conductive material, and has a reflecting surface 81a that is concave and has a parabolic curved surface. The concave reflecting member 81 is arranged so that the reflecting surface 81a faces the antenna 121. The concave reflecting member 81 has a hole 83 formed in a substantially central portion thereof, and the first support portion 541 is fitted into the hole 83 so that the first reflector 530A has one surface side (the opposite side of the light beam reflecting surface 531A). ) Is supported. The reflecting surface 81a of the concave reflecting member 81 is configured to be able to focus the microwave on the convex reflecting member 82 described later.

  The convex reflection member 82 is made of a conductive material, and has a reflective surface 82a that is convex and has a parabolic curved surface. Further, the convex reflecting member 82 is coaxially held in a state of facing the concave reflecting member 81. The convex reflection member 82 is supported by, for example, a first support portion 541 that supports the concave reflection member 81. The convex reflecting member 82 can focus the microwave on the arc tube 510 through the hole 83 formed in the concave reflecting member 81, and the reflecting surface 82 a has a substantially central portion of the arc tube 510. It is configured to be in focus. With such a configuration, the converging unit 4 reflects the microwave radiated from the antenna 121 in the order of the concave reflecting member 81 and the convex reflecting member 82 in order, and can be favorably focused on the arc tube 510. Therefore, the light emitting part 3 can be generated satisfactorily by the focused microwave and the generated light can be extracted efficiently. The convex reflecting member 82 may be formed so as to be embedded in the first support portion 541 made of quartz glass.

  Note that the light source device 1 reliably prevents the microwave from leaking to the outside between the microwave generation unit 2 and the reflector unit 530 by using a case member (not shown). Covers part 4.

  Subsequently, the operation of the light source device 1 will be described including the traveling direction of the microwave and the light flux. The microwave generator 2 generates a high-frequency signal and radiates the microwave 100a toward the concave reflecting member 81 constituting the converging unit 4 as a microwave 100a (indicated by a broken arrow in the drawing). The emitted microwave 100 a is a substantially plane wave and is reflected toward the convex reflecting member 82 by the reflecting surface 81 a of the concave reflecting member 81. The microwave 100a that has reached the convex reflection member 82 is further reflected by the reflection surface 82a. The reflected microwave 100 a is focused on the central portion of the arc tube 510. At this time, the light emitting substance enclosed in the light emitting region 511 is excited (and ionized) in the central region 512, which is a substantially central region of the light emitting region 511, by the microwave 100a converged on the central portion, thereby emitting plasma. As a result, the entire light emitting region 511 emits light.

  When the light emitting region 511 of the arc tube 510 emits light, a light beam 500a (indicated by the solid line arrow in the drawing) is emitted to the outside of the arc tube 510. A part of the emitted light beam 500a (light emitted to the front side of the arc tube 510) reaches the light beam reflecting surface 531B of the second reflector 530B and is reflected. In the present embodiment, the light beam reflected by the light beam reflecting surface 531B is directed to the first reflector 530A. Further, the remaining part of the light beam 500a (light emitted in a direction different from that of the second reflector 530B) reaches the light beam reflecting surface 531A of the first reflector 530A and is reflected. The light beam 500b reflected by the light beam reflecting surface 531A of the first reflector 530A becomes a parallel light beam substantially parallel to the illumination optical axis L (illustrated by a one-dot chain line).

  As described above, the light source device 1 according to this embodiment can focus the microwave on the light emitting unit 3 by the focusing unit 4 including the concave reflecting member 81 and the convex reflecting member 82. Therefore, it is possible to efficiently extract light generated by causing the light emitting unit 3 to emit light well with the focused microwave.

(projector)
Next, a projector (image display device) incorporating the light source device configured as described above will be described. FIG. 4 is a schematic diagram showing the structure of the components in the optical system of the projector.

  A projector 100 shown in FIG. 4 includes the light source device 1, and an illumination optical system 130 for uniformly illuminating the image forming area of the liquid crystal panel by uniformizing the illuminance distribution of the emitted light emitted from the light source device 1. And the light beam W emitted from the illumination optical system 130 is separated into red, green, and blue color light beams R, G, and B, and the red light beam R and the green light beam G respectively correspond to a liquid crystal panel (light modulation unit). The color light separating optical system 140 for guiding the light beam, the relay optical system 150 for guiding the blue light beam B having a long optical path to the corresponding liquid crystal panel among the color light beams separated by the color light separating optical system 140, and image information given to each color light beam Liquid crystal panels 160a, 160b, and 160c as light modulating devices that are modulated according to the above (referred to as 160 unless otherwise specified), and a crossbar that combines the modulated color light beams. A black dichroic prism 170, and a projection lens 190 for enlarging and projecting the synthesized light beam onto the projection surface 180.

  In addition to the light source device 1, the illumination optical system 130 includes a first lens array 131, a second lens array 132, a polarization conversion element 133, and a superimposing lens 134, and emits light emitted from the light source device 1. The first lens array 131 divides the light beam into a plurality of partial light beams, and each of the partial light beams is incident on the superimposing lens 134 via the second lens array 132 and the polarization conversion element 133. The superimposing lens 134 irradiates the liquid crystal panel 160 so that the liquid crystal panel 160 is uniformly illuminated by superimposing illumination.

  The color light separating optical system 140 includes a blue-green reflecting dichroic mirror 141, a green reflecting dichroic mirror 142, and a reflecting mirror 143. The blue-green reflecting dichroic mirror 141 transmits the red light component of the illumination light from the illumination optical system 130 and reflects the blue light component and the green component. The transmitted red light beam R is reflected by the reflecting mirror 43 and reaches the liquid crystal panel 160a. On the other hand, of the blue light beam B and the green light beam G reflected by the blue-green reflecting dichroic mirror 141, the green light beam G is reflected by the green reflecting dichroic mirror 142 and reaches the liquid crystal panel 160b. On the other hand, the blue light beam B passes through the green reflecting dichroic mirror 142 and enters the relay optical system 150.

  The relay optical system 150 is provided in an optical path that guides the blue light beam B to the corresponding liquid crystal panel 160c, and guides the blue light beam B to the liquid crystal panel 160c while maintaining its intensity. The first relay lens 151, the second relay lens 152, the condenser lens 153, and the reflecting mirrors 154 and 155 are provided.

  The three liquid crystal panels 160 have a function as light modulation means for modulating each color light according to given image information (image signal) and forming an image of each color component. This corresponds to a so-called electric light source device. Note that polarizing plates (not shown) are provided on the incident side and the outgoing side of these three liquid crystal panels 160, and only predetermined polarized light passes through the incident side polarizing plates of the liquid crystal panel 160 and is modulated.

  The modulated three color lights enter the cross dichroic prism 170 and are combined, and the combined light is projected onto the projection surface 180 by the projection lens 190 (projection unit).

  In the projector 100 configured as described above, since the light source device 1 according to the present invention is used, it is possible to provide a highly reliable projector with high light utilization efficiency and excellent contrast and brightness.

  The preferred embodiments according to the present invention have been described above with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to such examples, and the above embodiments may be combined. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

  In the present embodiment, the concave reflecting member 81 and the convex reflecting member 82 are arranged coaxially, but the present invention is not limited to this. For example, the position of the convex reflection member 82 can be changed by appropriately adjusting the curvature of the reflection surface 81 a of the concave reflection member 81. Thereby, the hole 83 for radiating the microwave reflected by the reflecting surface 82 a of the convex reflecting member 82 toward the arc tube 510 can be eliminated from the concave reflecting member 81.

  Further, the projector 100 in the above embodiment uses a liquid crystal panel as the light modulation unit. However, the present invention is not limited to this. In general, any device that modulates incident light in accordance with image information may be used, and a micromirror light modulator or the like may be used. For example, a DMD (Digital Micromirror Device) (registered trademark) can be used as the micromirror light modulator. In the case of using a micromirror type light modulation device, an incident polarizing plate, an emitting polarizing plate, etc. can be dispensed with, and a polarization conversion element can also be dispensed with.

  The light source device 1 in the above embodiment is used in a transmissive liquid crystal projector 100. However, the present invention is not limited to this, and the same effect can be obtained even when used in a projector that employs a liquid crystal on silicon (LCOS) system that is a reflective liquid crystal system.

  The light modulation unit in the above embodiment may be a three-plate system using three liquid crystal panels or a single-plate system using one liquid crystal panel. When the single plate method is used, a color separation optical system, a color synthesis optical system, and the like of the illumination optical system can be omitted.

  The light source device 1 in the above embodiment is applied to a front type projector that projects an optical image onto a screen installed outside. However, the present invention is not limited to this, and the present invention can also be applied to a rear type projector that has a screen inside the projector and projects an optical image on the screen.

  The projector 100 in the above embodiment may be provided with a voltage adjustment unit, and the amplification degree of the amplifier 29 of the solid-state high-frequency oscillation unit 20 may be variable. With such a configuration, since the output power of the microwave can be varied, the luminance of the light beam emitted from the arc tube 510 can be varied. Therefore, the brightness of the image light projected from the projector 100 can be adjusted according to the image scene by adjusting the amplification degree according to the image scene to be projected (for example, a bright scene or a dark scene). it can.

  In the light source device 1 in the above embodiment, the solid-state high-frequency oscillation unit 20 outputs a high-frequency signal in the 2.45 GHz band and radiates it from the antenna 121 as a microwave. However, the present invention is not limited to this, and by appropriately changing the configuration of the surface acoustic wave resonator, various high-frequency signals can be output and emitted as microwaves, so that the arc tube 510 can emit light. In this way, it is also possible to radiate microwaves that match the type of light-emitting substance sealed in the light-emitting tube 510 and the light emission condition (light emission color condition).

  The light source device 1 in the above embodiment is applied as a light source of a projector. However, the present invention is not limited to this, and the small and light source device may be applied to other optical devices. Moreover, it can be suitably applied to lighting equipment such as aviation, ships, vehicles, and indoor lighting equipment.

It is a schematic diagram which shows the structure of a light source device. It is a block diagram of a microwave generation part. It is a block diagram which shows schematic structure of a solid-state high frequency oscillator. It is a schematic diagram which shows the structure of the structure part in the optical system of a projector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source device, 2 ... Microwave generation part, 3 ... Light emission part, 4 ... Focusing part, 81 ... Concave reflection member, 82 ... Convex reflection member, 100 ... Projector (image display apparatus), 100a ... Microwave, 121 ... Antenna (microwave radiation part), 190 ... projection lens (projection part), 510 ... arc tube, 511 ... light emitting area, 530 ... reflector part

Claims (7)

A microwave generator that emits microwaves;
A light emitting unit that emits light by the microwave emitted from the microwave generating unit;
A focusing unit that focuses the microwave emitted from the microwave generation unit on the light emitting unit, and
The converging unit includes a concave reflecting member that reflects the microwave emitted from the microwave generating unit, and a convex reflecting member that reflects the microwave reflected by the concave reflecting member so as to converge the light emitting unit. And a light source device.   The light source device according to claim 1, wherein each of the concave reflection member and the convex reflection member is made of a conductive material. The microwave generation unit includes a microwave radiation unit that radiates the microwave,
When the wavelength of the microwave is λ,
3. The light source device according to claim 1, wherein a length of the microwave radiation unit is defined by nλ / 4 (n is a positive integer). The light emitting unit includes an arc tube in which a luminescent material that emits light by the microwave is enclosed,
The light source device according to any one of claims 1 to 3, wherein the arc tube includes a light emitting region having a spherical shape with an inner diameter of approximately 1 mm to 2 mm.   The light source device according to claim 4, wherein the arc tube is formed of any one of quartz, transparent sapphire, and translucent ceramic.   The light source device according to claim 4, wherein the light emitting unit further includes a reflector unit that emits light emitted from the arc tube in a substantially constant direction. The light source device according to any one of claims 1 to 6,
A light modulator that modulates a light beam emitted from the light source device according to input image information to form an optical image;
A projection unit that projects the optical image formed by the light modulation unit.

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