JP2008186888A - LIGHT SOURCE DEVICE, IMAGE DISPLAY DEVICE, PROJECTOR, MONITOR DEVICE, AND LIGHT SOURCE DEVICE DRIVING METHOD - Google Patents

Abstract

Provided are a light source device, an image display device, a projector, and a monitor device that can obtain stable laser light output and can improve the conversion efficiency of a wavelength conversion element.
The relationship between the heat capacities of the wavelength conversion element and the thermistor is started by starting temperature detection from the time when the temperature of the wavelength conversion element starts to stabilize after the start of pulse light emission (T _{1 to} T _{2 in} FIG. 3). In consideration of this, it is possible to prevent an error between the phase matching temperature of the wavelength conversion element and the actual temperature at the time of detection, and to reliably detect the phase matching temperature in consideration of the wavelength absorption of the wavelength conversion element.
[Selection] Figure 3

Description

  The present invention relates to a light source device, an image display device, a projector, a monitor device, and a light source device driving method.

  In recent years, coherent light sources have become indispensable in measurement fields such as image display devices, optical communication fields, medical fields, and microscopes. Various wavelengths of coherent light are used depending on the purpose. However, when a laser light source is used, light with a short wavelength such as blue light cannot be directly emitted with a sufficient amount of light. Therefore, infrared light is converted into blue light by being transmitted through a wavelength conversion element such as an SHG (Second Harmonic Generation) element that converts the fundamental wave into the second harmonic. In this way, the wavelength used for the laser light source can be increased by converting the wavelength of the light by wavelength conversion.

By the way, the wavelength conversion element has high temperature dependence, and it is necessary to control the temperature to a constant temperature in order to perform efficient wavelength conversion. Thus, for example, as shown in Patent Document 1, the harmonic output of the SHG element is detected, and voltage application or temperature control is performed on the SHG element so that the output of this harmonic becomes constant, thereby phase matching of the laser light source. An apparatus has been proposed that optimizes the conditions, and can obtain a stable second harmonic output without depending on the output intensity or the element structure.
JP-A-4-109226

  However, the following problems remain in the conventional laser light source. For example, the temperature control of the SHG element is performed corresponding to the output of the harmonic, but due to the heat capacity of the SHG element, it takes a certain amount of time to reach the temperature (assumed temperature) corresponding to the amount of heat supplied. Need. In other words, an error occurs between the optimum estimated temperature of the phase matching condition and the actual temperature at the time of detection, which causes a problem that a stable laser beam output cannot be obtained. In addition, the temperature control cannot be performed at high speed and high accuracy, and there is a problem that high improvement in conversion efficiency of the wavelength conversion element cannot be expected.

  Therefore, the present invention has been made to solve the above-described problems, and can provide a stable laser beam output and can improve the conversion efficiency of the wavelength conversion element, image It is an object to provide a display device, a projector, a monitor device, and a light source device driving method.

As a result of diligent efforts to achieve the above object, the present inventor has pulse-driven the light-emitting element that causes an error between the optimum estimated temperature of the phase matching condition and the actual temperature at the time of detection. In this case, since the wavelength conversion element absorbs infrared light and visible light, the light emission period of the light emitting element is such that the temperature of the wavelength conversion element rises due to light absorption, and the temperature of the light emission element decreases during the non-light emission period. I found it.
Therefore, the present invention provides the following means.

  The light source device of the present invention is a light emitting element that emits laser light, and converts light of a part of the laser light emitted from the light emitting element into light of a predetermined wavelength and converts the light to the predetermined wavelength. A wavelength conversion element that emits the emitted light; a temperature detection unit that detects the temperature of the wavelength conversion element; a temperature adjustment unit that adjusts the temperature of the wavelength conversion element; A control unit that controls the temperature adjustment unit so that the temperature of the wavelength conversion element becomes a predetermined temperature according to the temperature detected by the temperature detection unit, and the control unit outputs the light toward the light emitting element. A temperature detection signal synchronized with a pulse drive signal is output to the temperature detection unit, and the temperature adjustment unit is controlled according to the temperature detected by the temperature detection unit.

  In the light source device according to the present invention, when the laser light subjected to pulse drive control passes through the wavelength conversion element, the temperature of the wavelength conversion element changes depending on the output of the laser light incident on the wavelength conversion element. Therefore, by detecting the temperature of the wavelength conversion element in synchronization with the output of the laser light emitted from the light emitting element, when the laser light passes through the wavelength conversion element, the temperature optimum for phase matching (hereinafter referred to as phase matching). The temperature of the wavelength conversion element can be controlled to be constant so that the temperature of the wavelength conversion element becomes the phase matching temperature. In other words, even for pulsed lasers that are subject to rapid changes in the temperature of the wavelength conversion element, the temperature of the wavelength conversion element is accurately controlled to the phase matching temperature that takes into account the wavelength absorption, thereby stabilizing the laser. Light output can be obtained, and the conversion efficiency of the wavelength conversion element can be improved.

  Further, the light source device of the present invention is characterized in that the temperature detection unit starts temperature detection only a predetermined period before the time point when the light emitting element switches from the light emission period to the non-light emission period.

  In the light source device according to the present invention, the temperature detection is started only a predetermined period before the time point when the light emitting element switches from the light emission period to the non-light emission period, thereby ensuring the time necessary for the response of the temperature detection unit. Temperature detection can be reliably performed during light emission. Therefore, an error between the phase matching temperature of the wavelength conversion element 12 and the actual temperature at the time of detection can be prevented, and the phase matching temperature of the wavelength conversion element can be reliably detected.

  According to another aspect of the present invention, there is provided an image display device comprising: the light source device; and a scanning device that scans light emitted from the light source device to form an image.

  In the image display device according to the present invention, the light emitted from the light source device has high light conversion efficiency of the wavelength conversion element as described above. A bright image can be displayed also in the image display device.

  According to another aspect of the present invention, there is provided an image display device including the light source device and a light modulation device that modulates light emitted from the light source device in accordance with an image signal.

  In the image display device according to the present invention, the light emitted from the light source device enters the light modulation device. At this time, since the light emitted from the light source device has a high light conversion efficiency of the wavelength conversion element as described above, it is possible to display a bright image by providing the light source device in the image display device. Become.

  In the image display device of the present invention, the control unit outputs a plurality of pulse drive signals during one frame toward the light emitting element, and emits light by the plurality of pulse drive signals toward the temperature detection unit. A temperature detection signal for detecting temperature is output in the first light emission period of the laser beam to be output.

  In the image display device according to the present invention, the temperature of the wavelength conversion element is detected in the first light emission period among the plurality of pulse light emission during one frame, and the second and subsequent pulse light emission periods are based on the detected temperature. In addition, the wavelength conversion element can be quickly controlled to the phase matching temperature.

  In the image display device of the present invention, the control unit outputs a plurality of pulse drive signals during one frame toward the light emitting element, and emits light by the plurality of pulse drive signals toward the temperature detection unit. A temperature detection signal for detecting the temperature in the last light emission period of the laser beam to be output is output.

  In the image display device according to the present invention, the temperature of the wavelength conversion element is detected in the last light emission period among a plurality of pulsed emission during one frame, so that a more stable temperature of the wavelength conversion element can be detected.

  The image display device of the present invention is characterized in that the light source device can emit light in different wavelength ranges in time sequence.

  In the image display device according to the present invention, since the light source device emits light in different wavelength ranges in time sequence (time division) (so-called color sequential method, color sequential method, etc.), one light Color display is possible without using a color filter by simply using a modulation device.

  In the image display device of the present invention, the temperature detection unit detects the temperature in both an irradiation period and an irradiation suspension period of the light emitting element that emits light in a predetermined wavelength range.

  In the image display device according to the present invention, the temperature change due to the wavelength absorption of the wavelength conversion element during light emission can be detected by detecting the temperature of both the irradiation period and the irradiation suspension period of the light emitting element. Even when the intensity is changed, the temperature change due to the wavelength absorption can be estimated, and the wavelength conversion element can be quickly adjusted to the phase matching temperature.

  Further, the image display device of the present invention is characterized in that the temperature detection unit detects a temperature during an irradiation suspension period of the light emitting element.

  In the image display device according to the present invention, by detecting the temperature of the wavelength conversion element during the irradiation pause period of the light emitting element, the actual temperature of the wavelength conversion element during the irradiation pause period of the light emitting element can be detected. Therefore, the phase matching temperature of the wavelength conversion element during light emission can be controlled based on the detected temperature.

  According to another aspect of the invention, there is provided a projector including the image display device and a projection device that projects an image formed by the image display device.

  In the projector according to the present invention, since the light emitted from the light source device has high light conversion efficiency of the wavelength conversion element as described above, the subject is irradiated with bright light. Therefore, the subject can be clearly imaged by the imaging means.

  According to another aspect of the present invention, there is provided a monitor apparatus comprising: the light source apparatus described above; and an imaging unit that captures an image of a subject using light emitted from the light source apparatus.

  In the monitor device according to the present invention, the light emitted from the light source device irradiates the subject, and the subject is imaged by the imaging means. At this time, since the light emitted from the light source device has high light conversion efficiency of the wavelength conversion element as described above, the subject is irradiated with bright light. Therefore, the subject can be clearly imaged by the imaging means.

  Further, the driving method of the light source device of the present invention includes a light emitting element that emits laser light, and converts light of a part of the laser light emitted from the light emitting element into light of a predetermined wavelength, A wavelength conversion element that emits light converted to a predetermined wavelength, a temperature detection unit that detects the temperature of the wavelength conversion element, a temperature adjustment unit that adjusts the temperature of the wavelength conversion element, and a pulse drive of the light emitting element And using a light source device including a control unit that controls the heating unit so that the temperature of the wavelength conversion element becomes a predetermined temperature according to the temperature detected by the temperature detection unit, A temperature detection signal synchronized with a pulse drive signal output toward the light emitting element is output to the temperature detection unit, and the temperature adjustment unit is controlled according to the temperature detected by the temperature detection unit. .

  In the driving method of the light source device according to the present invention, the phase matching when the laser light passes through the wavelength conversion element is detected by detecting the temperature of the wavelength conversion element in synchronization with the output of the laser light emitted from the light emitting element. The temperature can be detected, and the temperature of the wavelength conversion element can be controlled to be constant so that the temperature of the wavelength conversion element becomes the phase matching temperature. In other words, stable laser light output can be obtained by controlling the temperature of the wavelength conversion element to the phase matching temperature with high accuracy even for laser light that is subjected to pulse drive control where the temperature change of the wavelength conversion element is severe. It is possible to improve the conversion efficiency of the wavelength conversion element.

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

(First embodiment)
(Light source device)
A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram of a light source device.
As shown in FIG. 1, a light source device 10 according to the present invention includes a semiconductor laser chip (light emitting element) 11 that emits infrared light, and a wavelength conversion element 12 that converts the wavelength of light emitted from the semiconductor laser chip 11. And a wavelength selection element 13 that transmits light converted by the wavelength conversion element 12 and selects and reflects light having a wavelength that has not been converted.

  The semiconductor laser chip 11 is provided with a laser drive unit (driver) 14 that emits pulses of the laser light emitted from the semiconductor laser chip 11. High conversion efficiency can be obtained by pulsing laser light. On one surface 12a of the wavelength conversion element 12, a heat diffusion plate 15 in contact with one surface is provided. A heater (temperature adjustment unit) 18 is provided on the surface 15b of the heat diffusion plate 15 opposite to the surface 15a with which the wavelength conversion element 12 contacts. The heat diffusing plate 15 spreads the heat of the heater 18 over the entire wavelength conversion element 12 and makes the temperature in the direction in which the laser light of the wavelength conversion element 12 travels uniform. That is, the entire wavelength conversion element 12 can be heated by the heat generated in the heater 18 via the thermal diffusion plate 15. In addition, as a temperature adjustment part, you may comprise the wavelength conversion element 12 from the Peltier device etc. which can be heated and cooled.

  A thermistor (temperature detection unit) Th is provided on the other surface 12 b of the wavelength conversion element 12. The thermistor Th is for detecting the temperature of the wavelength conversion element 12, and in the present embodiment, a contact type thermistor whose resistance value changes according to the temperature is used as the temperature detection unit. The wavelength conversion element 12 may be provided with a plurality of thermistors having different heat capacities.

  A control unit 20 is connected to the laser drive unit 14, the thermistor Th, and the heater 18. The control unit 20 controls the light emission timing of the laser driving unit 14, the temperature detection timing of the thermistor Th, and the heating timing of the heater 18 in synchronization with each other.

  The wavelength selection element 13 selects the laser beam W1 (a broken line shown in FIG. 1) W1 emitted from the wavelength conversion element 12 and reflects it toward the semiconductor laser chip 11 to reflect the outside of the semiconductor laser chip 11. It functions as a resonator mirror and transmits the converted laser beam (two-dot chain line shown in FIG. 1) W2. As the wavelength selection element 13, an optical element such as a volume hologram can be used.

  The fundamental wave light (solid line shown in FIG. 1) W3 emitted from the semiconductor laser chip 11 is repeatedly reflected and amplified between the semiconductor laser chip 11 and the wavelength selection element 13, and then is converted into a laser beam W2 as a wavelength. The light is emitted from the selection element 13. The wavelength selection element 13 transmits light of various wavelengths, but only light of a predetermined wavelength is amplified. The intensity of the amplified light is significantly higher than the intensity of light of other wavelengths. Therefore, the light W2 that has passed through the wavelength selection element 13 can be regarded as light having a substantially single wavelength. The wavelength of the light W2 is substantially the same as the wavelength selected by the wavelength selection element 13, that is, the wavelength of the light W1 reflected by the wavelength selection element 13. Since the wavelength selection element 13 reflects a part (about 98 to 99%) of light having a predetermined selection wavelength, the remaining light (about 1 to 2%) is used as output light.

  The wavelength selection element 13 selects only the laser light W1 that has not been converted to a predetermined wavelength by the wavelength conversion element 12, reflects it toward the semiconductor laser chip 11, and transmits the other laser light. . 1 is the central axis O of the laser light emitted from the semiconductor laser chip 11.

Here, FIG. 2 shows the relationship between the optical output of the laser light emitted from the semiconductor laser chip 11 and the temperature of the wavelength conversion element 12. In FIG. 2, the horizontal axis indicates time, the vertical axis indicates the optical output (solid line in FIG. 2) on the main axis, and the temperature of the wavelength conversion element (broken line in FIG. 2) on the second axis.
As shown in FIG. 2, when the laser light pulsed from the semiconductor laser chip 11 passes through the wavelength conversion element 12, the temperature change of the wavelength conversion element 12 is caused by the wavelength absorption of the laser light in the wavelength conversion element 12. Arise.

  Specifically, as shown in state A in FIG. 2, when the laser light is incident on the wavelength conversion element 12, the temperature of the wavelength conversion element 12 is increased by absorbing the wavelength of the laser light. Then, as in the B state, the temperature of the wavelength conversion element 12 stabilizes after a while after the laser beam is incident. This is because a time difference is produced between the incidence of laser light and the temperature change of the wavelength conversion element 12 due to the heat capacity of the wavelength conversion element 12. Then, as in the C state, after the laser beam is stopped, the temperature is decreased, and when the laser beam is incident on the wavelength conversion element 12 again by the next pulse, the temperature is increased. That is, it can be seen that the temperature change of the wavelength conversion element 12 repeats the temperature change cycle corresponding to the pulsed emission of the laser light incident on the wavelength conversion element 12.

Next, the control of the control unit 20 will be described based on FIG. FIG. 3 is a timing chart of laser light pulsed from the semiconductor laser chip 11 and temperature detection of the wavelength conversion element 12.
First, the control unit 20 sends an output signal to the laser driving unit 14. Specifically, a rectangular pulse drive signal is sent to the laser drive unit 14. Upon receiving the drive signal, the laser drive unit 14 outputs a pulsed current based on the drive signal to the semiconductor laser chip 11, and accordingly, as shown in FIG. 3, T _{1 to} T ₃ (in FIG. 2). (Corresponding to A to B), the laser light is pulsed from the semiconductor laser chip 11.

Subsequently, the control unit 20 outputs a temperature detection signal synchronized with the drive signal of the laser drive unit 14 to the thermistor Th, and the thermistor Th detects the temperature of the wavelength conversion element 12 according to the temperature detection signal. As for the timing of temperature detection, temperature detection is started from the time (predetermined period) necessary for the response of the thermistor Th from the time (T _{3 in} FIG. ₃ ) when the semiconductor laser chip 11 switches from the light emission period to the non-light emission period. Specifically, as described above, since there is a time difference between the incidence of the laser beam and the temperature change of the wavelength conversion element 12, the pulse emission start is considered in consideration of the responsiveness due to the heat capacity of the thermistor Th (FIG. 3). After the middle T ₁ ), a temperature detection start signal is sent to the thermistor Th before the time when the temperature of the wavelength conversion element 12 starts to stabilize (T _{2 in} FIG. 3).

Then, the thermistor Th by flash stop of the laser beam begins to detect with a margin so as to stabilize, at the same time to end the light emission stop of the laser beam (between in Figure 3 T _3). In this way, the temperature detection is performed in the light emission period of the laser beam while sufficiently satisfying the heat capacity conditions of the wavelength conversion element 12 and the thermistor Th. The temperature of the wavelength conversion element 12 at this time is a phase matching temperature of the wavelength conversion element 12, that is, a temperature at which the conversion efficiency of the wavelength conversion element 12 is good.

  Then, the heater 18 is controlled in accordance with the temperature detected by the thermistor Th. Specifically, the control unit 20 performs feedback during the next pulse emission period based on the phase matching temperature obtained by detecting the temperature of the thermistor Th, and the temperature when the laser light is incident on the wavelength conversion element 12 is determined. The heater 18 is controlled so as to be stable within the phase matching temperature range in consideration of the wavelength absorption in the wavelength conversion element 12. This cycle is repeated every pulse emission period. Thereby, the conversion efficiency of a laser beam can be improved. In this embodiment, all the laser beams are emitted as pulses. However, it is not necessary to emit all the pulses as pulses, and temperature detection is performed every pulse emission period, but the phase matching temperature is determined. Thus, it is not necessary to detect every pulse emission period.

  The light source device 10 according to the present embodiment includes a control unit 20 that is connected to the laser driving unit 14, the thermistor Th, and the heater 18, and that controls the laser driving unit 14, the thermistor Th, and the heater 18 in synchronization with each other. did. According to this configuration, when the pulsed laser light passes through the wavelength conversion element 12, the temperature of the wavelength conversion element 12 changes depending on the output of the laser light incident on the wavelength conversion element 12. Therefore, by detecting the temperature of the wavelength conversion element 12 in synchronization with the output of the laser light emitted from the semiconductor laser chip 11, the phase matching temperature of the wavelength conversion element 12 is reliably detected, and the wavelength conversion element 12 The temperature of the wavelength conversion element 12 can be controlled so that the temperature becomes the phase matching temperature. That is, a stable laser can be obtained by accurately controlling the temperature of the wavelength conversion element 12 to a phase matching temperature that takes into account the wavelength absorption even for laser light that is emitted in a pulsed state where the temperature change of the wavelength conversion element 12 is severe. Light output can be obtained, and the conversion efficiency of the wavelength conversion element 12 can be improved.

Further, the temperature detection timing is determined from the time when the temperature of the wavelength conversion element 12 starts to stabilize after the start of pulse light emission (T _{1 to} T _{2 in} FIG. 3) after considering the relationship of the heat capacity of the thermistor Th. By starting the above, it is possible to reliably detect the temperature at the time of laser emission while securing the time required for the response of the wavelength conversion element 12. Therefore, an error between the phase matching temperature of the wavelength conversion element 12 and the actual temperature at the time of detection can be prevented, and the phase matching temperature of the wavelength conversion element 12 can be reliably detected.

Further, as shown in FIG. 4, the temperature detection timing is started from the time (T _{2 in} FIG. 4) when the temperature of the wavelength conversion element 12 starts to stabilize most before the time required for the response of the thermistor Th. It is also possible to detect in the period in which the temperature of the wavelength conversion element 12 is most stable (corresponding to T _{2 to} T _{3 in} FIG. 4 and B in FIG. 2). Thereby, in addition to producing the above-described effects, the temperature detection time can be shortened in consideration of the relationship between the heat capacities of the wavelength conversion element 12 and the thermistor Th. It can be used effectively.

(projector)
Next, a liquid crystal projector including the light source device 10 will be described with reference to FIG. FIG. 4 is a schematic configuration diagram of the projector (image display device) of the present embodiment. In FIG. 4, the casing constituting the projector 100 is omitted for simplification.

  In the projector 100, as the red laser light source (light source device) 10R, the green laser light source (light source device) 10G, and the blue laser light source (light source device) 10B that emit red light, green light, and blue light, the above-described light source device 10 is used. Use.

  In addition, the projector 100 emits light from the liquid crystal light valves (light modulation devices) 104R, 104G, and 104B that modulate laser light emitted from the laser light sources 10R, 10G, and 10B, and the liquid crystal light valves 104R, 104G, and 104B, respectively. A cross dichroic prism 106 that synthesizes light and guides it to the projection lens 107, and a projection lens (projection device) 107 that enlarges and projects an image formed by the liquid crystal light valves 104R, 104G, and 104B onto the screen 110 are provided. .

  Furthermore, in order to make the illuminance distribution of the laser light emitted from the laser light sources 10R, 10G, and 10B uniform, the projector 100 makes the uniformizing optical systems 102R and 102G downstream of the laser light sources 10R, 10G, and 10B. , 102B are provided, and the liquid crystal light valves 104R, 104G, 104B are illuminated by light having a uniform illuminance distribution. For example, the uniformizing optical systems 102R, 102G, and 102B are configured by, for example, a hologram 102a and a field lens 102b.

  The three color lights modulated by the respective liquid crystal light valves 104R, 104G, and 104B are incident on the cross dichroic prism 106. This prism is formed by bonding four right-angle prisms, and a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light are arranged in a cross shape on the inner surface thereof. These dielectric multilayer films combine the three color lights to form light representing a color image. The synthesized light is projected onto the screen 110 by the projection lens 107, which is a projection optical system, and an enlarged image is displayed.

  According to the projector 100 described above, the laser beams emitted from the laser light sources 10R, 10G, and 10B are incident on the liquid crystal light valves 104R, 104G, and 104B. Then, the images formed by the liquid crystal light valves 104R, 104G, and 104B are projected by the projection lens 107. At this time, since the laser light emitted from the laser light sources 10R, 10G, and 10B has high light conversion efficiency of the wavelength conversion element 12 as described above, the laser light sources 10R, 10G, and 10B are provided in the projector 100. Thus, a bright image can be displayed.

(Second Embodiment)
Next, based on FIG. 6, a second embodiment according to the present invention will be described mainly with reference to FIGS.
In the present embodiment, a configuration example of a color sequential projector including the light source device 10 according to the present invention will be described.
The projector 1 according to this embodiment is a digital light processing (hereinafter, abbreviated as DLP, registered trademark of Texas Instruments) system using a DMD (reflection type light modulation device) as a light modulation device. It is a projector. In the projector 1, the red laser light source (light source device) 10R that emits red light, green light, and blue light, the green laser light source (light source device) 10G, and the blue laser light source (light source device) 10B are described in the first embodiment. The light source device 10 of the form is used.

FIG. 6 is a schematic configuration diagram of the projector according to the present embodiment. FIG. 7 is a timing chart showing the pulse waveform of the laser light source. In FIG. 6, the casing constituting the projector 1 is omitted for simplification.
As shown in FIG. 6, the projector 1 of this embodiment includes an illumination device 2, a DMD 3, and a projection lens 4. The illumination device 2 emits light that illuminates the DMD 3. The DMD 3 modulates incident light by deflecting the optical path of incident light when reflecting light incident from the illumination device 2. The projection lens 4 is a lens for projecting the laser light modulated by the DMD 3 onto the screen 40.

  The illumination device 2 includes a light source unit 8, an optical fiber 39, a rod integrator 30, and a magnifying lens 31. The light source unit 8 includes a plurality of laser light sources (light source devices) 10R, 10G, and 10B that each emit light of different wavelength ranges, that is, light of different colors. In the present embodiment, the plurality of laser light sources 10R, 10G, and 10B emit red light (R light), green light (G light), and blue light (B light), respectively. The wavelength range of each color light is, for example, 580 to 780 nm for R light, 480 to 580 nm for G light, and 380 to 480 nm for B light. However, the division of the wavelength range is only an example, and the present invention is not limited to this.

  In the light source unit 8, a plurality of laser light sources 10R, 10G, and 10B are collectively arranged, and a cooling device 33 for cooling the plurality of laser light sources 10R, 10G, and 10B is provided in the plurality of laser light sources 10R, 10G, and 10B. It is arranged close to. As the cooling device 33, various types of cooling devices such as a water cooling type and an air cooling type can be used regardless of the cooling method.

  An optical multiplexer 34 that combines the color lights emitted from the plurality of laser light sources 10R, 10G, and 10B is provided, and the plurality of color lights are combined by the optical multiplexer 34. The optical multiplexer 34 has a built-in speckle canceller (not shown), and the speckle canceller suppresses the generation of speckle when combining highly coherent laser beams.

  One end of an optical fiber 39 is connected to the output end of the optical multiplexer 34, and the rod integrator 30 is connected to the other end of the optical fiber 39. A magnifying lens 31 is disposed on the light exit side of the rod integrator 30. With the above configuration, the color lights emitted from the plurality of laser light sources 10R, 10G, and 10B are combined by the optical multiplexer 34 and then incident on the rod integrator 30 through one optical fiber 39. Each color light is converted into a rectangular shape so as to match the shape of the light incident surface of the DMD 3 at the same time as the illuminance is made uniform by the rod integrator 30 and then transmitted to the light incident surface of the DMD 3 by the magnifying lens 31. .

  The DMD 3 is a reflection type light modulation element provided with a micro mirror 36 at a position corresponding to each pixel, and the luminance of the emitted light (reflected light) is changed by driving the micro mirror 36 with an electrostatic force or the like to change the reflection angle. Modulate. The DMD 3 has a feature that a light shielding portion such as a signal line and a driving transistor is formed below the micromirror 36, so that an aperture ratio (a ratio of a region where light can be used in a unit pixel region) is large and moire is not conspicuous. Have.

  In the DMD 3, the micromirrors 36 constituting the pixels are individually displaced according to the modulation signal to control the light reflection direction. In other words, the DMD 3 controls the time of each state by switching between a state in which light is incident on the projection lens 4 (hereinafter referred to as an ON state) and a state in which light is not incident (hereinafter referred to as an OFF state). The luminance modulation is performed. Therefore, the DMD 3 performs binary control of the ON state and the OFF state. When viewed from the light incident through the projection lens 4 from the outside of the apparatus, the light of the reflected light when all the micromirrors 36 are in the ON state. A lighting device 2 is disposed on the road.

  The illuminating device 2 in the present embodiment is configured such that the three laser light sources 10R, 10G, and 10B emit R light, G light, and B light sequentially in time. That is, as shown in FIG. 7, one frame period is divided into three, and each 1/3 frame (one subframe) period is sequentially emitted as an irradiation period of R light, G light, and B light. Furthermore, R light, G light, and B light are emitted as rectangular pulses (for example, four rectangular pulses) during each irradiation period. Each color light is irradiated to the DMD 3 through the optical multiplexer 34, the optical fiber 39, the rod integrator 30, and the magnifying lens 31. Therefore, each micromirror 16 is driven based on the drive signal so that the DMD 3 also generates an image corresponding to each color light every 1/3 frame period. As described above, the projector 1 according to this embodiment is a so-called color sequential projector.

  When the light from the illuminating device 2 is irradiated onto the DMD 3, the micromirror 36 corresponding to each pixel of the DMD 3 is directed in different directions so that the pixel is turned on or off. Light reflected by the micromirror 36 a in the ON state is incident on the projection lens 4, and light reflected by the micromirror 36 b in the OFF state is not incident on the projection lens 4. That is, when the ON state pixel is in the bright state and the OFF state pixel is in the dark state, the DMD 3 controls each color light in the 1/3 frame period by controlling the bright state and the dark state for each pixel according to the drive signal. Generated image. Then, the image generated on the DMD 3 is projected on the screen 40 by the projection lens 4. The user can see a full-color image by the integration effect of the image for each color light on the retina.

Next, control of the control unit 20 in the second embodiment will be described. FIG. 8 is a diagram showing a timing chart of light emission pulses and temperature detection. The light emission pulse in FIG. 8 indicates a light emission pulse of 1/3 frame in any one color among the pulse light emission of each color shown in FIG.
As shown in FIG. 8, the temperature of the wavelength conversion element 12 is detected at the time of the first pulse emission within the irradiation period (T _{1 to} T _{3 in} FIG. 8). In the same manner as the detection method of the first embodiment, this detection method starts from the time when the semiconductor laser chip 11 switches from the light emission period to the non-light emission period in consideration of the responsiveness due to the heat capacities of the wavelength conversion element 12 and the thermistor Th. Temperature detection is performed only before the time required for the response of the thermistor Th (T _{2 to} T _{3 in} FIG. 8).

  Then, the detected temperature becomes the phase matching temperature of the wavelength conversion element 12, and feedback is performed at the time of the second and subsequent pulse emission based on this phase matching temperature, and the temperature of the wavelength conversion element 12 falls within the phase matching temperature region. The heater 18 is controlled to be stable. Thereby, it can control rapidly to the phase matching temperature of the wavelength conversion element 12 which considered the part for wavelength absorption. Note that the temperature detection timing may be performed in a pulse emission period transmitted at the end of each irradiation period. That is, since the temperature of the wavelength conversion element 12 is stable during the pulse emission period transmitted at the end of each irradiation period, the wavelength conversion element 12 is used in the irradiation period of the next frame based on the temperature detected at this time. Is fed back so that the temperature is at this temperature. Thereby, the temperature of the wavelength conversion element 12 can be controlled to be more stable.

  According to the present embodiment, since the laser light sources 10R, 10G, and 10B are color sequential systems that sequentially emit light in different wavelength ranges without using a color filter by using only one light modulation device, Color display is possible. At this time, the same effect as that of the light source device 10 of the first embodiment is obtained, and the light conversion efficiency of the wavelength conversion element 12 is high. Therefore, by providing the laser light sources 10R, 10G, and 10B in the projector 1, a bright image can be obtained. Can be displayed. Note that the color sequential method is not limited to the projector using the DMD method, and the color sequential method is also possible for a projector using a light valve such as a reflective liquid crystal light valve or a transmissive liquid crystal light valve.

(Third embodiment)
Next, based on FIG. 9, a third embodiment of the present invention will be described mainly with reference to FIGS. FIG. 9 is a diagram showing a timing chart of light emission pulses and temperature detection in the third embodiment. In addition, the light emission pulse of FIG. 9 has shown the 2 frame period in arbitrary 1 color among the pulse light emission of each color shown in FIG.
This embodiment is a color sequential projector similar to the second embodiment, and controls temperature control in the control unit 20 of the laser light source (light source device) 10 based on the temperature change amount of the wavelength conversion element 12. It is different in point. In the following description, when it is not necessary to distinguish the three laser light sources 10R, 10G, and 10B, the laser light source 10 is collectively referred to, and the configuration of the laser light source 10 is described in the first and second embodiments. Since it is the same as that of FIG.

As shown in FIG. 9, first, in the first pulse emission period (T _{1 to} T _{3 in} FIG. 8) in the irradiation period, the pulse emission of the semiconductor laser chip 11 is performed in the same manner as in the first and second embodiments. During the period, the temperature when the temperature of the wavelength conversion element 12 is stabilized is detected. The temperature detected at this time is the phase matching temperature of the wavelength conversion element 12 and is the maximum value when the laser beam is absorbed by the wavelength conversion element 12.

  Here, in the color sequential projector, since one frame is divided into irradiation periods every 1/3 frame and each color is emitted sequentially, other than the laser light source that emits light (for example, the laser light source 10R). Two-color laser light sources (for example, laser light sources 10G and 10B) are in an irradiation pause state. Therefore, compared with the projector 100 of 1st Embodiment, the non-light emission period of each laser light source 10R, 10G, 10B is long, and the temperature change of the wavelength conversion element 12 becomes more intense.

Therefore, the temperature of the wavelength conversion element 12 is also detected during the laser beam irradiation suspension period. Specifically, after the last pulse emission within the irradiation period is stopped, the temperature of the wavelength conversion element 12 is lowered and stabilized, that is, after the pulse emission stops, the first pulse in the next irradiation period. The temperature is detected immediately before (T _{6 in} FIG. 10) is injected (T _{4 to} T _{5 in} FIG. 10). The temperature of the wavelength conversion element 12 detected at this time is the actual temperature of the wavelength conversion element 12 during the irradiation suspension period of the semiconductor laser chip 11, and is the minimum value of the temperature of the wavelength conversion element 12. That is, the amount of change in the temperature of the wavelength conversion element 12 can be detected by detecting the maximum value of the laser light irradiation period and the minimum value of the irradiation pause period. Note that the temperature detection in the irradiation suspension period may be made to emit a pulse in the next irradiation period at the same time as the temperature detection in the irradiation suspension period is finished (that is, T ₅ = T ₆ ).

  Then, based on the amount of change, a signal is sent from the control unit 20 to the heater 18 to control the temperature of the wavelength conversion element 12 so as to be surely within the phase matching temperature region when the laser beam is incident. As a result, the wavelength conversion element 12 can be stably controlled even in a color sequential projector having an irradiation suspension period.

  According to the present embodiment, the same effect as that of the first embodiment is obtained, and the temperature of the wavelength conversion element 12 is detected during both the laser light irradiation period and the irradiation suspension period, whereby the laser in the wavelength conversion element 12 is detected. The amount of change in temperature due to light wavelength absorption can be detected. For this reason, even in the color sequential projector 1 in which the temperature change is severe, the irradiation suspension period exists, so that the laser beam can be reliably controlled within the phase matching temperature region when entering the wavelength conversion element 12. Furthermore, even when the intensity of the pulse output is changed, or in various combinations of light emission patterns, the temperature change due to the wavelength absorption in the wavelength conversion element 12 is estimated, and the wavelength conversion element 12 is quickly adjusted to the phase matching temperature. Therefore, the conversion efficiency of laser light can be improved.

(Fourth embodiment)
Next, based on FIG. 10, 4th Embodiment of this invention is described mainly referring FIG. FIG. 10 is a diagram illustrating a timing chart of light emission pulses and temperature detection in the fourth embodiment. In addition, the light emission pulse of FIG. 10 has shown between two frames in arbitrary 1 color among the pulse light emission of each color shown in FIG.
The present embodiment is different from the second and third embodiments in that the temperature control of the wavelength conversion element 12 is performed using only the temperature detection during the irradiation suspension period. First, the temperature of the wavelength conversion element 12 during the irradiation suspension period is detected by the same method as in the fourth embodiment (T _{4 to} T _{5 in} FIG. 10). Then, using a LUT (look up table) corresponding to the absorption amount of the wavelength conversion element 12 in advance, the temperature detected during the irradiation pause period is associated with the LUT so that the optimum phase matching temperature can be obtained for the laser light irradiation period. The heater 18 is controlled.

  According to the present embodiment, the same effects as those of the first embodiment can be obtained, and the LUT is made to correspond to the actual temperature of the wavelength conversion element 12, thereby adjusting the optimum phase matching temperature in the laser light irradiation period. Therefore, the conversion efficiency of the laser beam in the wavelength conversion element 12 can be improved.

  The light source device 10 of the first to fourth embodiments is also applied to a scanning image display device. An example of such an image display device is shown in FIG. The image display device 200 illustrated in FIG. 11 includes the light source device 10 according to the first embodiment, the MEMS mirror (scanning device) 202 that scans the light emitted from the light source device 10 toward the screen 210, and the light source device 10. A condensing lens 203 that condenses the emitted light on the MEMS mirror 202 is provided. The light emitted from the light source device 10 is guided to scan the screen 210 in the horizontal direction and the vertical direction by moving the MEMS mirror 202. In the case of displaying a color image, a plurality of emitters constituting the semiconductor laser chip 11 may be configured by a combination of emitters having red, green, and blue peak wavelengths.

(Fifth embodiment)
Next, a fifth embodiment according to the present invention will be described with reference to FIG.
In the present embodiment, a configuration example of a monitor device 300 including the light source device 10 of the first embodiment will be described. FIG. 12 is a diagram illustrating a schematic configuration of the monitor device. The monitor device 300 includes a device main body 310 and an optical transmission unit 320. The apparatus main body 310 includes the light source device 10 of the first embodiment.

  The light transmission unit 320 includes two light guides 321 and 322 on the light sending side and the light receiving side. Each of the light guides 321 and 322 is a bundle of a large number of optical fibers, and can send laser light to a distant place. The light source device 10 is disposed on the incident side of the light guide 321 on the light transmission side, and the diffusion plate 323 is disposed on the emission side thereof. The laser light emitted from the light source device 10 is transmitted to the diffusion plate 323 provided at the tip of the light transmission unit 320 through the light guide 321 and is diffused by the diffusion plate 323 to irradiate the subject.

  An imaging lens 324 is also provided at the tip of the light transmission unit 320, and reflected light from the subject can be received by the imaging lens 324. The received reflected light travels through the light guide 322 on the receiving side and is sent to a camera 311 as an imaging means provided in the apparatus main body 310. As a result, an image based on the reflected light obtained by irradiating the subject with the laser light emitted from the light source device 10 can be captured by the camera 311.

  According to the monitor device 300 configured as described above, the subject can be irradiated by the high-output light source device 10, so that the brightness of the captured image obtained by the camera 311 can be increased.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the temperature detection timing during the pulse emission period may be changed as appropriate.

It is a front view which shows the light source device which concerns on embodiment of this invention. It is a graph which shows the relationship between the pulse output of the laser beam of the light source device of FIG. 1, and the temperature of a wavelength conversion element. It is a figure which shows the timing chart of the pulse light emission of the light source device of FIG. 1, and temperature detection. It is a figure which shows the timing chart of other embodiment of FIG. 1 is a plan view showing a projector according to a first embodiment of the invention. It is a top view which shows the projector which concerns on 2nd Embodiment of this invention. It is a timing chart which shows the drive waveform of the pulse light emission of a projector. It is a figure which shows the timing chart of the light emission pulse of the light source device of 2nd Embodiment of this invention, and temperature detection. It is a figure which shows the timing chart of the light emission pulse of the light source device of 3rd Embodiment of this invention, and temperature detection. It is a figure which shows the timing chart of the light emission pulse and temperature detection of the light source device of 4th Embodiment of this invention. It is a top view which shows the image display apparatus which concerns on embodiment of this invention. It is a top view which shows the monitor apparatus which concerns on 5th Embodiment of this invention.

Explanation of symbols

  Th ... thermistor, 10 ... light source device, 12 ... wavelength conversion element, 18 ... heater (temperature adjustment unit), 20 ... control unit, 1,100 ... projector, 104R, 104G, 104B ... liquid crystal light valve (light modulation device) 107 ... Projection lens (projection device) 202 ... MEMS mirror (scanning device) 300 ... Monitor device 311 ... Camera

Claims (12)

A light emitting element for emitting laser light;
Of the laser light emitted from the light emitting element, a wavelength conversion element that converts light having a predetermined wavelength into light having a predetermined wavelength and emits light converted to the predetermined wavelength;
A temperature detector for detecting the temperature of the wavelength conversion element;
A temperature adjusting unit for adjusting the temperature of the wavelength conversion element;
A pulse drive control of the light emitting element, and a control unit that controls the temperature adjustment unit so that the temperature of the wavelength conversion element becomes a predetermined temperature according to the temperature detected by the temperature detection unit,
The control unit outputs a temperature detection signal synchronized with a pulse drive signal output toward the light emitting element to the temperature detection unit, and controls the temperature adjustment unit according to the temperature detected by the temperature detection unit. A light source device characterized by the above.   2. The light source device according to claim 1, wherein the temperature detection unit starts temperature detection a predetermined period before a time point when the light emitting element switches from a light emission period to a non-light emission period. The light source device according to claim 1 or 2,
An image display device comprising: a scanning device that scans light emitted from the light source device to form an image. The light source device according to claim 1 or 2,
An image display device comprising: a light modulation device that modulates light emitted from the light source device according to an image signal.   The control unit outputs a plurality of pulse drive signals during one frame toward the light emitting element, and at an initial emission period of laser light emitted by the plurality of pulse drive signals toward the temperature detection unit. 5. The image display device according to claim 3, wherein a temperature detection signal for detecting temperature is output.   The control unit outputs a plurality of pulse drive signals during one frame toward the light emitting element, and at the last light emission period of the laser light emitted by the plurality of pulse drive signals toward the temperature detection unit. 5. The image display device according to claim 3, wherein a temperature detection signal for detecting temperature is output.   The image display device according to any one of claims 3 to 6, wherein the light source device can emit light in different wavelength ranges sequentially in time.   The image display device according to claim 7, wherein the temperature detection unit detects the temperature in both an irradiation period and an irradiation suspension period of the light emitting element that emits light in a predetermined wavelength range.   The image display device according to claim 7, wherein the temperature detection unit detects a temperature during an irradiation suspension period of the light emitting element. An image display device according to any one of claims 3 to 9,
A projector comprising: a projection device that projects an image formed by the image display device. The light source device according to claim 1 or 2,
A monitor device comprising: imaging means for imaging a subject by light emitted from the light source device. A light emitting element for emitting laser light;
Of the laser light emitted from the light emitting element, a wavelength conversion element that converts light having a predetermined wavelength into light having a predetermined wavelength and emits light converted to the predetermined wavelength;
A temperature detector for detecting the temperature of the wavelength conversion element;
A temperature adjusting unit for adjusting the temperature of the wavelength conversion element;
A light source device comprising: a control unit that performs pulse drive control of the light emitting element and controls the temperature adjusting unit so that the temperature of the wavelength conversion element becomes a predetermined temperature according to the temperature detected by the temperature detecting unit Use
The control unit outputs a temperature detection signal synchronized with a pulse drive signal output toward the light emitting element to the temperature detection unit, and controls the temperature adjustment unit according to the temperature detected by the temperature detection unit. A method for driving a light source device.

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