Projection display device

Abstract

A projection display device according to the present embodiment includes a light source (101) which emits laser light for use in projection of an image and has a non-display function to stop light emission of the light source (101) to temporarily hide the projection of the image. The projection display device comprises: a light source temperature sensor (172) which detects the temperature of the light source (101); a light source heater (171) which heats the light source (101); a control unit (12) which controls the operations of at least the light source (101) and the light source heater (171); and a changeover switch (165) which gives instructions to execute or cancel the non-display function. When the changeover switch (165) has given instructions to execute the non-display function, the control unit (12) stops light emission of the light source (101), acquires the temperature detected by the light source temperature sensor (172), and controls the light source heater (171) so that the light source (101) maintains the acquired temperature.

Description

projection display device

[0001] The present disclosure relates to a projection display device that has a function of turning off a light source to temporarily hide a projected image.

[0002] Generally, a projection display device using a reflective liquid crystal display element is known (see, for example, Patent Document 1). In this type of projection display device, for example, a blue laser light source irradiates a phosphor with blue laser light to generate white light, and this white light is then decomposed into red, blue, and green light, and each of these color lights is modulated by a reflective liquid crystal display element, and an image is enlarged and projected onto a screen.

[0003] Japanese Patent Application Laid-Open No. 2005-227485

[0004] This type of projection display device is equipped with a hide function that temporarily hides the projected image. This configuration allows the projection surface to be rendered completely black by turning off the laser light source, which is highly effective for, for example, projecting a night sky in a planetarium or blending multiple images.

[0005] On the other hand, in order to maintain good image performance in a projection display device, it is important to maintain the temperature of not only the liquid crystal display element but also the light source within a certain range. In conventional configurations, when the non-display function is executed, the light source is temporarily turned off, causing the temperature of the light source to drop. Therefore, when the non-display function is released, the output of the light source becomes unstable until the light source is heated to a predetermined temperature, which can lead to problems such as the inability to quickly project a good image.

[0006] In view of the above-described problems, the present disclosure has an object to provide a projection display device that can quickly project a good image when the non-display function is released.

[0007] A projection display device according to one aspect of this embodiment has a light source that emits laser light used to project an image, and is equipped with a non-display function that temporarily hides the projection of an image by stopping the light source from emitting light, and is equipped with a light source temperature sensor that detects the temperature of the light source, a light source heating unit that heats the light source, a control unit that controls the operation of at least the light source and the light source heating unit, and a switch that instructs the execution or cancellation of the non-display function, and when the switch instructs the execution of the non-display function, the control unit stops the light source from emitting light, acquires the temperature detected by the light source temperature sensor, and controls the light source heating unit so that the light source maintains the acquired temperature.

[0008] Furthermore, a projection display device according to one aspect of this embodiment has a light source that emits laser light used to project an image, and is equipped with a non-display function that temporarily hides the projection of an image by stopping the light source from emitting light, and is equipped with a light source heating unit that heats the light source, an information acquisition unit that acquires information regarding the relationship between the output of the light source and the temperature of the light source, and the relationship between the output of the light source heating unit and the temperature of the light source, a control unit that controls the operation of at least the light source and the light source heating unit, and a switch that instructs the execution or cancellation of the non-display function, and when the switch instructs the execution of the non-display function, the control unit stops the light source from emitting light, estimates the temperature of the light source corresponding to the output of the light source based on the information acquired by the information acquisition unit, and controls the light source heating unit to an output corresponding to the estimated temperature.

[0009] According to this embodiment, the operation of the light source heating unit maintains the temperature of the light source at the temperature when the non-display function is executed, so that a good image can be quickly projected when the non-display function is deactivated.

[0010] FIG. 1 is a schematic diagram of a display device according to a first embodiment. FIG. 2 is a schematic block diagram of a control unit according to the first embodiment. FIG. 3 is a flowchart showing the procedure of operation of the control unit according to the first embodiment. FIG. 4 is a schematic diagram of a display device according to a second embodiment. FIG. 5 is a schematic block diagram of a control unit according to the second embodiment. FIG. 6 is a flowchart showing the procedure of operation of the control unit according to the second embodiment.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiments described below.

[0012] First Embodiment FIG. 1 is a schematic diagram of a projection display device according to a first embodiment. The projection display device generates white light by irradiating a phosphor with visible light (e.g., blue laser light), decomposes the white light into red, blue, and green light, and then modulates and combines these light components to display an image. As shown in FIG. 1 , the projection display device 100 includes a display mechanism 10 and a control unit 12. The display mechanism 10 includes a light source 101, a phosphor 103, polarizing plates 105R, 105G, and 105B, a first display element 106R, a second display element 106G, a third display element 106B, a color synthesis prism 108, a projection lens 109, a λ / 4 plate 110, dichroic mirrors 120-122, reflecting mirrors 130-132, lenses 140-146, and a polarization conversion element 150. The first display element 106R, the second display element 106G, and the third display element 106B are reflective liquid crystal display elements that have, for example, a configuration in which a liquid crystal layer is sandwiched between a silicon substrate and a glass substrate, and are provided corresponding to each color described below.

[0013] The dichroic mirrors 120 to 122 have the property of separating incident light by reflection and transmission, with the separation wavelengths serving as separation boundaries. The dichroic mirrors 120 to 122 can be fabricated by forming, for example, a dielectric multilayer film on a predetermined region of a transparent material such as a glass plate or a prism. The optical properties can be set according to the material and film thickness of the dielectric material that makes up the dielectric multilayer film.

[0014] The light source 101 emits illumination light in the visible wavelength band. In this embodiment, the light source 101 is a blue laser light source configured with a blue laser element, and emits blue illumination light in the wavelength band of, for example, 450 (nm) or more and 495 (nm) or less.

[0015] In this embodiment, light source 101 has three (plural) groups of blue laser light sources, namely, first blue laser light source 101α, second blue laser light source 101β, and third blue laser light source 101γ, each with a different oscillation wavelength. The oscillation wavelengths of these groups, first blue laser light source 101α to third blue laser light source 101γ, are set to differ from each other by at least 10 nm. Specifically, the oscillation wavelength of first blue laser light source 101α is set to 445 nm, the oscillation wavelength of second blue laser light source 101β is set to 455 nm, and the oscillation wavelength of third blue laser light source 101γ is set to 465 nm.

[0016] Generally, when a short-wavelength blue laser light source is used as a single-wavelength light source, unevenness in the thickness (cell thickness) of the liquid crystal display element can cause fringes (interference fringes) that separate bright and dark regions, and these fringes can be superimposed on the displayed image. This requires strict control of the thickness of the liquid crystal display element. In contrast, as described above, this embodiment is configured to include three groups of first blue laser light source 101α to third blue laser light source 101γ, each with an oscillation wavelength that differs by at least 10 nm. This reduces fringes, particularly in blue images, because the fringe spacing and peak-to-valley positions change depending on the oscillation wavelength. This allows for relaxation of thickness control standards for liquid crystal display elements.

[0017] The oscillation wavelengths of first blue laser light source 101α to third blue laser light source 101γ described above are merely examples and can be changed as appropriate as long as they are included in the blue wavelength band. The difference in the oscillation wavelengths of the blue laser light sources can be changed as appropriate within a range of, for example, 10 nm to 20 nm. Furthermore, the number of groups of blue laser light sources is not limited to three, as long as there are multiple groups.

[0018] Blue illumination light from light source 101 is irradiated onto dichroic mirror 120. Dichroic mirror 120 has the property of reflecting blue illumination light and transmitting yellow illumination light. In this embodiment, dichroic mirror 120 includes dichroic mirrors 120α, 120β, and 120γ arranged corresponding to first blue laser light source 101α to third blue laser light source 101γ.

[0019] The blue illumination light emitted from first blue laser light source 101α to third blue laser light source 101γ is reflected by dichroic mirrors 120α to 120γ, and then collected by lens 140 to be irradiated onto phosphor 103. Phosphor 103 has a fluorescent layer and a reflective surface. The fluorescent layer generates yellow illumination light containing red and green band components with intensities corresponding to the energy intensities of the blue illumination light irradiated from first blue laser light source 101α to third blue laser light source 101γ. The reflective surface reflects the blue illumination light that has passed through the fluorescent layer and the yellow illumination light generated by the fluorescent layer.

[0020] Dichroic mirrors 120α, 120β, and 120γ are formed to have an area smaller than the beam width of the reflected light (diffused light) from phosphor 103. Furthermore, these dichroic mirrors 120α to 120γ are oriented so that the polarization direction of the laser light relative to dichroic mirrors 120α, 120β, and 120γ is s-polarized. Therefore, dichroic mirrors 120α to 120γ have the property of reflecting s-polarized light and transmitting p-polarized light of the blue illumination light incident on them, while transmitting yellow illumination light regardless of the polarization direction.

[0021] Therefore, yellow illumination light (fluorescent light) containing red and green components due to wavelength excitation by phosphor 103 and blue illumination light that is not fluorescent are mixed together and re-enter dichroic mirrors 120α to 120γ. The yellow illumination light containing red and green components, which is fluorescent light, passes through dichroic mirrors 120α to 120γ and is emitted in its entirety. On the other hand, when the blue illumination light is reflected (diffused) by phosphor 103, it becomes randomly polarized light, a mixture of multiple polarized light components. Therefore, of the components of blue illumination light that strike dichroic mirrors 120α to 120γ, the p-polarized component passes through dichroic mirrors 120α to 120γ and is emitted, while the s-polarized component is reflected by dichroic mirrors 120α to 120γ and returns to first blue laser light source 101α to third blue laser light source 101γ.

[0022] The blue illumination light and yellow illumination light that have passed through the dichroic mirrors 120α to 120γ are reflected by the reflecting mirror 130 and enter the lens 141. The lenses 141 and 142 are, for example, fly-eye lenses, and a λ / 4 plate 110 is disposed between these lenses 141 and 142. The blue illumination light and yellow illumination light that have been reflected by the reflecting mirror 130 have their illumination distribution homogenized by the lenses 141, λ / 4 plate 110, and 142, and are then entered into the polarization conversion element 150. The polarization conversion element 150 includes, for example, a polarizing beam splitter and a retardation plate. The polarizing beam splitter reflects either s-polarized light or p-polarized light and transmits the other. In the example of FIG. 1, the polarizing beam splitter reflects s-polarized light and transmits p-polarized light. The retardation plate converts either s-polarized light or p-polarized light into the other. In the example of FIG. 1, the retardation plate converts s-polarized light to p-polarized light. The polarization conversion element 150 converts each illumination light into p-polarized light.

[0023] The illumination light beams converted into p-polarized light by the polarization conversion element 150 are irradiated onto the dichroic mirror 121 via a lens 143. The lens 143 is, for example, a condenser lens.

[0024] The dichroic mirror 121 separates the incident blue illumination light BL from the yellow illumination light YL. The yellow illumination light YL separated by the dichroic mirror 121 is reflected by the reflecting mirror 131 and enters the dichroic mirror 122.

[0025] The dichroic mirror 122 separates the incident yellow illumination light YL into red illumination light RL containing a red band component and green illumination light GL containing a green band component, using a wavelength intermediate between the red light band and the green light band as a separation boundary. Specifically, the dichroic mirror 122 reflects the green band component of the incident yellow illumination light YL to emit the green illumination light GL, and transmits the red band component of the incident yellow illumination light YL to emit the red illumination light RL. The red illumination light RL is, for example, light in a wavelength band of 620 (nm) to 750 (nm), and the green illumination light GL is, for example, light in a wavelength band of 495 (nm) to 570 (nm).

[0026] The red illumination light RL separated by the dichroic mirror 122 is irradiated onto the polarizing plate 105R via a lens 144. The green illumination light GL separated by the dichroic mirror 122 is irradiated onto the polarizing plate 105G via a lens 145. The blue illumination light BL separated by the dichroic mirror 121 is reflected by a reflecting mirror 132 and irradiated onto the polarizing plate 105B via a lens 146.

[0027] The polarizing plates 105R, 105G, and 105B have the property of reflecting either s-polarized light or p-polarized light and transmitting the other. The example in Fig. 1 shows a state in which the polarizing plates 105R, 105G, and 105B reflect s-polarized light and transmit p-polarized light. The polarizing plates 105R, 105G, and 105B are also referred to as reflective polarizing plates. The polarizing plates 105R, 105G, and 105B are, for example, wire grid polarizing plates.

[0028] The red illumination light RL, which is p-polarized light, passes through the polarizing plate 105R and is irradiated onto the first display element 106R. The green illumination light GL, which is p-polarized light, passes through the polarizing plate 105G and is irradiated onto the second display element 106G. The blue illumination light BL, which is p-polarized light, passes through the polarizing plate 105B and is irradiated onto the third display element 106B.

[0029] The first display element 106R optically modulates p-polarized red illumination light RL based on red component image data to generate s-polarized red image light RM. The second display element 106G optically modulates p-polarized green illumination light GL based on green component image data to generate s-polarized green image light GM. The third display element 106B optically modulates p-polarized blue illumination light BL based on blue component image data to generate s-polarized blue image light BM. That is, the first display element 106R functions as a red image light modulation element, the second display element 106G functions as a green image light modulation element, and the third display element 106B functions as a blue image light modulation element.

[0030] Red image light RM, which is s-polarized light and generated by first display element 106R, is reflected by polarizing plate 105R and is irradiated onto color synthesis prism 108. Green image light GM, which is s-polarized light and generated by second display element 106G, is reflected by polarizing plate 105G and is irradiated onto color synthesis prism 108. Blue image light BM, which is s-polarized light and generated by third display element 106B, is reflected by polarizing plate 105B and is irradiated onto color synthesis prism 108.

[0031] The color synthesis prism 108 reflects the red image light RM and the blue image light BM, transmits the green image light GM, and irradiates each image light onto a projection lens 109 .

[0032] The red image light RM, green image light GM, and blue image light BM are projected onto a screen or the like (not shown) via a projection lens 109. A visible light image is displayed by the red image light RM, green image light GM, and blue image light BM.

[0033] The projection display device 100 of this embodiment is equipped with a non-display function (also referred to as a hide function or image mute function) that temporarily hides or completely blacks out the projected image. This type of non-display function not only stops the operation of the display elements 106R, 106G, and 106B of each color or causes a completely black display, but also, if the light source 101 uses a device capable of instantaneous on / off, such as an LD (laser diode) or LED (light-emitting diode), stops (turns off) the light from the light source 101 to reproduce pitch black on the projection surface (e.g., a screen). This is highly effective, for example, for projecting a night sky in a planetarium or for blending multiple overlapping images. The non-display function can be activated or deactivated by operating a selector switch 165 (described later) provided on the projection display device itself.

[0034] Furthermore, the projection display device 100 of this embodiment allows a user to select between a normal operation mode and a non-display mode (hide mode) as an operating mode. Here, when the non-display mode is selected and an instruction to execute the non-display function is received, the projection display device 100 stops the operation of the display elements 106R, 106G, and 106B of each color or sets them to an all-black display, and also stops (turns off) the light source 101 from emitting light, temporarily hiding the projected image until an instruction to deactivate the non-display function is received. Also, when the normal operation mode is selected (the non-display mode is not selected), and an instruction to execute the non-display function is received, the projection display device 100 continues to emit light from the light source 101, stops the operation of the display elements 106R, 106G, and 106B of each color or sets them to an all-black display, temporarily hiding the projected image until an instruction to deactivate the non-display function is received. In this embodiment, a configuration in which the non-display mode is selected, i.e., a configuration in which the light source 101 stops (turns off) emitting light when an instruction to execute the non-display function is received, is described.

[0035] As described above, when the non-display mode is selected and execution of the non-display function is instructed (hereinafter simply referred to as execution of the non-display function), the projection display device 100 stops the operation of the display elements 106R, 106G, and 106B of each color or displays them all black, and also stops (turns off) the light source 101 to temporarily hide the projected image. In this case, temporarily stopping the display elements 106R, 106G, and 106B and the light source 101 reduces the temperatures of the display elements 106R, 106G, and 106B and the light source 101. Therefore, even if the non-display function is disabled, the outputs of the display elements 106R, 106G, and 106B and the light source 101 may become unstable until the display elements 106R, 106G, and 106B and the light source 101 are heated to the predetermined temperatures before being stopped, which may result in a malfunction such as an inability to quickly project a good image.

[0036] In this embodiment, as shown in FIG. 1 , the display mechanism 10 includes an element heater (element heating unit) 161 disposed via a heat sink 160 on the back surface (the surface opposite to the side irradiated with each illumination light) of each of the display elements 106R, 106G, and 106B of each color, and an element temperature sensor 162 provided on the heat sink 160. The heat sink 160 is a plate-like member formed of a metal with high thermal conductivity, such as aluminum, and has a certain thickness. The heat sink 160 is formed larger than the back surface of each display element, and the entire back surface is in contact with the heat sink 160.

[0037] The element heater 161 heats each of the display elements 106R, 106G, and 106B via the heat sink 160, and may be, for example, a plate-shaped ceramic heater. The element heater 161 is disposed on the heat sink 160, thereby heating the entire heat sink 160 and uniformly heating each of the display elements 106R, 106G, and 106B. The element temperature sensor 162 is attached to the heat sink 160 and can indirectly detect the temperatures of the display elements 106R, 106G, and 106B by measuring the temperature of the heat sink 160. Each of the display elements 106R, 106G, and 106B may include a bandgap element temperature sensor (not shown) in its element circuit, and the bandgap element temperature sensor may be used to directly measure the temperatures of the display elements 106R, 106G, and 106B.

[0038] The display mechanism 10 also includes light source heaters (light source heating units) 171 disposed on the back surfaces of the first blue laser light source 101α, the second blue laser light source 101β, and the third blue laser light source 101γ via heat sinks 170, and a light source temperature sensor 172 provided on the heat sinks 170. The heat sinks 170 are plate-shaped members made of a metal with high thermal conductivity, such as aluminum, and have a certain thickness. The heat sinks 170 are formed larger than the back surfaces of the laser light sources, and the entire back surfaces are in contact with the heat sinks 170.

[0039] The light source heater 171 heats each of the laser light sources 101α, 101β, and 101γ via the heat sink 170, and may be, for example, a plate-shaped ceramic heater. By being disposed on the heat sink 170, the light source heater 171 can heat the entire heat sink 170, and thereby uniformly heat each of the laser light sources 101α, 101β, and 101γ. The light source temperature sensor 172 is attached to the heat sink 170, and by measuring the temperature of the heat sink 170, the temperature of each of the laser light sources 101α, 101β, and 101γ can be indirectly detected. In this embodiment, the display mechanism 10 is configured such that each laser light source 101α, 101β, and 101γ is provided with its own heat sink 170 and light source heater 171, but it may also be configured such that a common heat sink is provided for each laser light source 101α, 101β, and 101γ, and a common light source heater is arranged on this heat sink.

[0040] Next, the control unit 12 will be described. FIG. 2 is a schematic block diagram of the control unit according to this embodiment. As shown in FIG. 2, the control unit 12 includes a light source temperature acquisition unit 21, an element temperature acquisition unit 22, a light source heating control unit 23, an element heating control unit 24, a fan control unit 25, a light source control unit 26, an element control unit 27, and a function instruction reception unit 28. The light source heating control unit 23, the element heating control unit 24, the fan control unit 25, the light source control unit 26, and the element control unit 27 may be configured as integrated circuits, which are hardware, or may be configured as a central processing unit (CPU) and memory, which are the arithmetic device of a computer, and a computer program (software) stored in the memory is executed by the CPU. Note that in this embodiment, only the parts related to the operation control of each unit when the non-display function is executed or canceled will be described, and other parts will not be described.

[0041] The light source temperature acquisition unit 21 acquires temperature data of each of the laser light sources 101α, 101β, and 101γ detected by the light source temperature sensor 172. The light source temperature acquisition unit 21 outputs the acquired temperature data of each of the laser light sources 101α, 101β, and 101γ to the light source heating control unit 23 and the fan control unit 25.

[0042] The element temperature acquisition unit 22 acquires temperature data of each of the display elements 106R, 106G, and 106B detected by the element temperature sensor 162. The element temperature acquisition unit 22 outputs the acquired temperature data of each of the display elements 106R, 106G, and 106B to the element heating control unit 24 and the fan control unit 25.

[0043] The light source heating control unit 23 controls the operation of the light source heaters 171 provided in each of the laser light sources 101α, 101β, and 101γ based on the temperature data of each of the laser light sources 101α, 101β, and 101γ input from the light source temperature acquisition unit 21. Specifically, the light source heating control unit 23 sets the temperature data of each of the laser light sources 101α, 101β, and 101γ immediately before the non-display function is executed as a first light source temperature, and controls the operation of driving each of the light source heaters 171 to heat each of the laser light sources 101α, 101β, and 101γ so that each of the laser light sources 101α, 101β, and 101γ maintains this first light source temperature. That is, for example, when the detected temperature of the first blue laser light source 101α is lower than the set first light source temperature, the light source heating control unit 23 turns on (operates) the light source heater 171 to heat the first blue laser light source 101α. This control activates the light source heater 171, so that each of the laser light sources 101α, 101β, and 101γ can be uniformly heated to an appropriate temperature via the heat sink 170, even when the non-display function is being executed (the light source 101 is stopped). Furthermore, the light source heating control unit 23 controls the light source heater 171 to turn off (stop) when the temperature data input from the light source temperature acquisition unit 21 reaches a second light source temperature that is higher than the first light source temperature. This second light source temperature is set to a temperature that is a predetermined temperature (e.g., 5°C to 10°C) higher than the first light source temperature. In this configuration, each of the laser light sources 101α, 101β, and 101γ is sufficiently heated to an appropriate temperature, so the light source heater 171 is turned off to avoid excessive heating.

[0044] The element heating control unit 24 controls the operation of the element heaters 161 provided in each of the display elements 106R, 106G, and 106B based on the temperature data of each of the display elements 106R, 106G, and 106B input from the element temperature acquisition unit 22. Specifically, the element heating control unit 24 sets the temperature data of each of the display elements 106R, 106G, and 106B immediately before the non-display function is executed as a first element temperature, and controls the operation of driving each element heater 161 to heat each of the display elements 106R, 106G, and 106B so that each of the display elements 106R, 106G, and 106B maintains this first element temperature. That is, for example, when the detected temperature of the first display element 106R is lower than the set first element temperature, the element heating control unit 24 controls the element heater 161 to be turned on to heat the first display element 106R. This control activates the element heater 161, allowing each display element 106R, 106G, and 106B to be uniformly heated to an appropriate temperature via the heat sink 160, even when the non-display function is being executed (i.e., the display elements are stopped). Alternatively, a target temperature may be set in advance for each display element 106R, 106G, and 106B, and the element heating control unit 24 may control each element heater 161 to maintain the target temperature at all times, regardless of whether the non-display function is being executed. Furthermore, the element heating control unit 24 controls the element heater 161 to turn off when the temperature data input from the element temperature acquisition unit 22 reaches a second element temperature, which is higher than the first element temperature. This second element temperature is set to a temperature that is a predetermined temperature (e.g., 1°C to 2°C) higher than the first element temperature. In this configuration, each display element 106R, 106G, and 106B is sufficiently heated to an appropriate temperature, and the element heater 161 is turned off to avoid excessive heating.

[0045] The fan control unit 25 controls the operation of the fan 164 based on temperature data input from the light source temperature acquisition unit 21 or the element temperature acquisition unit 22. The fan 164 is provided, for example, in a housing (not shown) that houses the display mechanism 10 and blows air onto the light source and element heat sinks 170 and 160 to cool the display mechanism 10 (particularly the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B). The fan control unit 25 controls the operation of the fan 164 when the temperature data input from the light source temperature acquisition unit 21 or the element temperature acquisition unit 22 reaches, for example, the higher of the second light source temperature and the second element temperature. This prevents the temperatures of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B from rising excessively. In addition, fans for cooling the laser light sources 101α, 101β, 101γ and the display elements 106R, 106G, 106B may be provided inside the housing (not shown), and each fan may be operated when the temperature data input from the light source temperature acquisition unit 21 or the element temperature acquisition unit 22 reaches the second light source temperature and the second element temperature, respectively.

[0046] The function instruction receiving unit 28 receives an instruction regarding the non-display function based on the operation of the selector switch 165. Specifically, the function instruction receiving unit 28 receives an instruction to execute or cancel the non-display function. The function instruction receiving unit 28 outputs the received instruction regarding the non-display function to the light source control unit 26 and the element control unit 27.

[0047] The light source control unit 26 controls the operation of the light source 101 based on an instruction related to the non-display function input from the function instruction receiving unit 28. Specifically, when the light source control unit 26 receives an instruction to execute the non-display function from the function instruction receiving unit 28 via operation of the selector switch 165, it controls the light sources 101 (laser light sources 101α, 101β, 101γ) to stop emitting light (turn off). Furthermore, when the light source control unit 26 receives an instruction to cancel the non-display function from the function instruction receiving unit 28 via operation of the selector switch 165, it controls the light sources 101 (laser light sources 101α, 101β, 101γ) to emit light (turn on).

[0048] The element control unit 27 controls the operation of each of the display elements 106R, 106G, and 106B based on an instruction related to the non-display function input from the function instruction receiving unit 28. Specifically, when the element control unit 27 receives an instruction to execute the non-display function from the function instruction receiving unit 28 via operation of the selector switch 165, it controls the operation of each of the display elements 106R, 106G, and 106B to stop or to display all black. Furthermore, when the element control unit 27 receives an instruction to cancel the non-display function from the function instruction receiving unit 28 via operation of the selector switch 165, it controls the operation of each of the display elements 106R, 106G, and 106B again.

[0049] Next, the control operation of each unit in the control unit will be described. FIG. 3 is a flowchart showing the procedure of the operation of the control unit according to this embodiment. In this flowchart, it is assumed that the projection display device 100 is currently projecting an image and the above-described non-display mode (hide mode) is selected. As shown in FIG. 3, the control unit 12 determines whether or not an instruction to execute the non-display function has been issued by the selector switch 165 (step S11). More specifically, the control unit 12 determines whether or not an instruction to execute the non-display function has been accepted by the function instruction accepting unit 28 via the selector switch 165. If it is determined that the instruction to execute the non-display function has not been issued by the selector switch 165 (step S11; No), the control unit 12 ends the process.

[0050] On the other hand, if the selector switch 165 has instructed to execute the non-display function (step S11; Yes), the control unit 12 acquires the temperature data detected by the light source temperature sensor 172 and the element temperature sensor 162 (step S12). More specifically, immediately before the execution of the non-display function is instructed, the control unit 12 causes the light source temperature acquisition unit 21 to acquire the temperature data of each of the laser light sources 101α, 101β, and 101γ detected by the light source temperature sensor 172, and causes the element temperature acquisition unit 22 to acquire the temperature data of each of the display elements 106R, 106G, and 106B detected by the element temperature sensor 162.

[0051] Next, the control unit 12 stops the operation of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B (step S13). More specifically, when the function instruction receiving unit 28 receives an instruction to execute the non-display function, the control unit 12 controls the light source control unit 26 to stop (turn off) the light emission of the laser light sources 101α, 101β, and 101γ, and controls the element control unit 27 to stop the operation of the display elements 106R, 106G, and 106B or to display them in all black. As a result, the projection display device 100 executes the non-display function, which temporarily hides image projection.

[0052] Next, the control unit 12 operates the light source heater 171 and the element heater 161 to maintain the temperatures of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B (step S14). More specifically, the control unit 12 sets the temperatures of the laser light sources 101α, 101β, and 101γ immediately before the non-display function is executed as first light source temperatures, and controls the light source heating control unit 23 to drive the light source heaters 171 to heat the laser light sources 101α, 101β, and 101γ so that the laser light sources 101α, 101β, and 101γ maintain the first light source temperatures. In this case, when the temperatures of the laser light sources 101α, 101β, and 101γ reach second light source temperatures that are higher than the first light source temperatures, the control unit 12 controls the light source heating control unit 23 to turn off (stop) the light source heater 171. This makes it possible to prevent the laser light sources 101α, 101β, and 101γ from being excessively heated.

[0053] Furthermore, the control unit 12 sets the temperature of each of the display elements 106R, 106G, and 106B immediately before the non-display function is executed as a first element temperature, and controls the element heating control unit 24 to drive each element heater 161 to heat each of the display elements 106R, 106G, and 106B so that each of the display elements 106R, 106G, and 106B maintains this first element temperature. In this case, when each of the temperatures of the display elements 106R, 106G, and 106B reaches a second element temperature that is higher than the first element temperature, the control unit 12 controls the element heating control unit 24 to turn off (stop) the element heater 161. This makes it possible to prevent each of the display elements 106R, 106G, and 106B from being overheated.

[0054] Furthermore, when the temperatures of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B reach, for example, the higher of the second light source temperature and the second element temperature, the control unit 12 performs control to operate the fan 164. This allows the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B to be cooled and prevented from being overheated.

[0055] Next, the control unit 12 determines whether or not an instruction to disable the non-display function has been issued by the changeover switch 165 (step S15). More specifically, the control unit 12 determines whether or not an instruction to disable the non-display function has been accepted by the function instruction accepting unit 28 via the changeover switch 165. If it is determined that an instruction to disable the non-display function has not been issued by the changeover switch 165 (step S15; No), the control unit 12 returns the process to step S14.

[0056] On the other hand, if the changeover switch 165 has instructed to disable the non-display function (step S15; Yes), the control unit 12 resumes the operation of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B (step S16). More specifically, when the function instruction receiving unit 28 receives an instruction to disable the non-display function, the control unit 12 resumes the operation of turning on (emitting light from) the laser light sources 101α, 101β, and 101γ via the light source control unit 26. The control unit 12 also resumes the operation of turning on the display elements 106R, 106G, and 106B via the element control unit 27. As a result, the non-display function that temporarily disables image projection is canceled in the projection display device 100, and image projection resumes. At this time, the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B are maintained at the first light source temperature and the first element temperature, respectively, by the light source heater 171 and the element heater 161. Therefore, when the non-display function is released, the output of the laser light sources 101α, 101β, and 101 can be stabilized, and further, the colors emitted by the display elements 106R, 106G, and 106B can be stabilized, allowing for prompt projection of a good image.

[0057] Next, the control unit 12 stops the operation of the light source heater 171 and the element heater 161 (step S17). More specifically, since the operation of each of the laser light sources 101α, 101β, and 101γ and each of the display elements 106R, 106G, and 106B has resumed, there is no need for further heating, and therefore the light source heating control unit 23 and the element heating control unit 24 stop the operation of the light source heater 171 and the element heater 161. This completes the series of processes.

[0058] As described above, the projection display device 100 according to this embodiment has the laser light sources 101α, 101β, and 101γ that emit laser light used to project an image, and has a non-display function that temporarily hides the projection of an image by stopping the emission of each of the laser light sources 101α, 101β, and 101γ, and includes a light source temperature sensor 172 that detects the temperature of each of the laser light sources 101α, 101β, and 101γ, a light source heater 171 that heats each of the laser light sources 101α, 101β, and 101γ, and a light source heater 171 that heats at least each of the laser light sources. The projection optical system includes a control unit 12 that controls the operation of laser light sources 101α, 101β, and 101γ and light source heater 171, and a selector switch 165 that instructs execution or cancellation of a non-display function, and when execution of the non-display function is instructed by selector switch 165, the control unit 12 stops the emission of each of the laser light sources 101α, 101β, and 101γ, acquires the temperature detected by light source temperature sensor 172, and controls light source heater 171 so that each of the laser light sources 101α, 101β, and 101γ maintains the acquired temperature. With this configuration, when the non-display function is canceled, the temperature of each of the laser light sources 101α, 101β, and 101 is maintained, so that the output of each of the laser light sources 101α, 101β, and 101 can be stabilized, and a good image can be quickly projected.

[0059] In the projection display device 100 according to this embodiment, when the changeover switch 165 is used to instruct cancellation of the non-display function, the control unit 12 starts the emission of light from each of the laser light sources 101α, 101β, and 101γ, and stops the heating operation of the light source heater 171. According to this configuration, the start of emission of light from the laser light sources 101α, 101β, and 101γ makes it possible to maintain the temperatures of the laser light sources 101α, 101β, and 101γ without heating with the light source heater 171, thereby enabling prompt projection of a good image.

[0060] The projection display device 100 according to this embodiment includes display elements 106R, 106G, and 106B, which are arranged to correspond to red, green, and blue, respectively, and which irradiate laser light to generate image light corresponding to each color, element heaters 161 for heating each of the display elements 106R, 106G, and 106B, and element temperature sensors 162 for detecting the temperatures of each of the display elements 106R, 106G, and 106B. When execution of the non-display function is instructed by the selector switch 165, the control unit 12 stops the operation of each of the display elements 106R, 106G, and 106B, acquires the temperatures detected by the element temperature sensor 162, and controls the element heater 161 so that the temperatures of each of the display elements 106R, 106G, and 106B are maintained at the acquired temperatures. When release of the non-display function is instructed by the selector switch 165, the control unit 12 starts the operation of each of the display elements 106R, 106G, and 106B, and stops the heating operation of the element heater 161. According to this configuration, when the non-display function is released, the temperature of each display element 106R, 106G, 106B is maintained, so that the color emitted by each display element 106R, 106G, 106B can be stabilized, and a good image can be quickly projected.

[0061] Second Embodiment Next, a second embodiment will be described. FIG. 4 is a schematic diagram of a projection display device according to the second embodiment. FIG. 5 is a schematic block diagram of a control unit according to the second embodiment. Components of a projection display device 100A according to the second embodiment that are identical to those in the first embodiment are designated by the same reference numerals, and their description will be omitted. As shown in FIG. 4, the projection display device 100A includes a display mechanism 10A and a control unit 12A. In the second embodiment, as shown in FIG. 4, the display mechanism 10A includes light source heaters (light source heating units) 171 disposed on the rear surfaces of the laser light sources 101α, 101β, and 101γ via heat sinks 170, respectively. However, unlike the first embodiment, no light source temperature sensor is provided. Meanwhile, the display mechanism 10A includes an environmental temperature sensor 175 that detects the ambient temperature within the display mechanism 10A. The environmental temperature sensor 175 is provided, for example, within a housing (not shown) that houses the display mechanism 10A and detects the air temperature within the housing.

[0062] As shown in FIG. 5 , the control unit 12A includes an element temperature acquisition unit 22, a light source heating control unit 23, an element heating control unit 24, a fan control unit 25, a light source control unit 26, an element control unit 27, a function instruction reception unit 28, an environmental temperature acquisition unit 29, an information acquisition unit 30, and a light source temperature estimation unit 31. The light source heating control unit 23, the element heating control unit 24, the fan control unit 25, the light source control unit 26, the element control unit 27, and the light source temperature estimation unit 31 may be configured as integrated circuits, which are hardware, or may be configured as a central processing unit (CPU) and memory, which are the arithmetic unit of a computer, and a computer program (software) stored in the memory is executed by the CPU. Note that in this embodiment, only the parts related to the operation control of each unit when the non-display function is executed or canceled will be described, and other parts will not be described. Furthermore, the same components as those in the first embodiment will be designated by the same reference numerals and will not be described again.

[0063] As described above, the light source control unit 26 controls the operation of each of the laser light sources 101α, 101β, and 101γ based on instructions related to the non-display function input from the function instruction receiving unit 28. When the light source control unit 26 receives an instruction to execute the non-display function from the function instruction receiving unit 28, it stops the emission of each of the laser light sources 101α, 101β, and 101γ. At this time, the light source control unit 26 reads out the output values ​​of each of the laser light sources 101α, 101β, and 101γ immediately before executing the non-display function, and outputs these output values ​​to the light source temperature estimator 31.

[0064] The environmental temperature acquisition unit 29 acquires temperature data of the environmental temperature (air temperature) inside the housing of the display mechanism 10A detected by the environmental temperature sensor 175. The environmental temperature acquisition unit 29 outputs the acquired temperature data to the light source temperature estimation unit 31.

[0065] The information acquisition unit 30 acquires information regarding the relationship between the output values ​​(outputs) of the laser light sources 101α, 101β, and 101γ and the temperatures of the laser light sources 101α, 101β, and 101γ, and the relationship between the output value (output) of the light source heater 171 and the temperatures of the laser light sources 101α, 101β, and 101γ, from the storage unit 166. Specifically, the storage unit 166 stores information regarding the temperatures of the laser light sources 101α, 101β, and 101γ when the laser light sources 101α, 101β, and 101γ are caused to emit light at predetermined output values, which information has been obtained through prior experiments or the like. In this case, the storage unit 166 stores information (e.g., table data) regarding the temperatures of the laser light sources 101α, 101β, and 101γ corresponding to changes in the environmental temperature and the output values ​​when the environmental temperature and the output values ​​are changed, respectively. Therefore, when each laser light source 101α, 101β, and 101γ is made to emit light at a predetermined output value under a predetermined ambient temperature, the information acquisition unit 30 can acquire information regarding the temperature of each laser light source 101α, 101β, and 101γ corresponding to this ambient temperature and output value.

[0066] The memory unit 166 also stores information about the temperatures of the laser light sources 101α, 101β, and 101γ when the light source heater 171 is operated at a predetermined output value with the laser light sources 101α, 101β, and 101γ turned off, based on prior experiments or the like. In this case, the memory unit 166 stores information (e.g., table data) about the temperatures of the laser light sources 101α, 101β, and 101γ corresponding to changes in the ambient temperature and the output value of the light source heater 171 when the ambient temperature and the output value of the light source heater 171 are changed. Therefore, when the light source heater 171 is operated at a predetermined output value under a predetermined ambient temperature, the information acquisition unit 30 can acquire information about the temperatures of the laser light sources 101α, 101β, and 101γ (the temperatures to which the laser light sources 101α, 101β, and 101γ rise when heated) corresponding to the ambient temperature and the output value. The information acquisition unit 30 outputs the acquired information to the light source temperature estimation unit 31.

[0067] The light source temperature estimation unit 31 estimates the temperatures of the laser light sources 101α, 101β, and 101γ corresponding to the output values ​​of the laser light sources 101α, 101β, and 101γ based on the information acquired by the information acquisition unit 30. Specifically, from the output values ​​of the laser light sources 101α, 101β, and 101γ and the environmental temperature immediately before the non-display function is executed that are input from the light source control unit 26, the light source temperature estimation unit 31 reads information on the temperatures of the laser light sources 101α, 101β, and 101γ corresponding to these output values ​​and environmental temperature, and estimates this temperature as the temperature of the laser light sources 101α, 101β, and 101γ immediately before the non-display function is executed.

[0068] The light source heating control unit 23 controls the light source heaters 171 to output values ​​of the light source heaters 171 that correspond to the estimated temperatures of the laser light sources 101α, 101β, and 101γ based on the information acquired by the information acquisition unit 30. As a result, the laser light sources 101α, 101β, and 101γ are heated by the light source heaters 171, and are maintained at the temperatures immediately before the non-display function was executed, even after the non-display function is executed.

[0069] Next, the control operation of each unit in the control unit 12A will be described. FIG. 6 is a flowchart showing the procedure of the operation of the control unit according to this embodiment. In this flowchart, it is also assumed that the projection display device 100A is currently projecting an image and that the above-described non-display mode (hide mode) is selected. As shown in FIG. 6, the control unit 12A determines whether or not execution of the non-display function has been instructed by the selector switch 165 (step S21). More specifically, the control unit 12A determines whether or not an instruction to execute the non-display function has been received via the selector switch 165 by the function instruction receiving unit 28. If execution of the non-display function has not been instructed by the selector switch 165 (step S21; No), the control unit 12A terminates the process.

[0070] On the other hand, if the selector switch 165 has instructed execution of the non-display function (step S21; Yes), the control unit 12A acquires the temperature data detected by each of the element temperature sensors 162 (step S22). More specifically, the control unit 12A causes the element temperature acquisition unit 22 to acquire the temperature data of each of the display elements 106R, 106G, and 106B detected by the element temperature sensor 162 immediately before the instruction to execute the non-display function is given.

[0071] Next, the control unit 12A estimates the temperatures of the light sources corresponding to the output values ​​of the light sources based on the information stored in the storage unit 166 (step S23). More specifically, the control unit 12A uses the information acquisition unit 30 to acquire information regarding the relationship between the output values ​​of each of the laser light sources 101α, 101β, and 101γ and the temperatures of the laser light sources 101α, 101β, and 101γ, and the relationship between the output value (output) of the light source heater 171 and the temperatures of each of the laser light sources 101α, 101β, and 101γ, from the storage unit 166. Then, the control unit 12A uses the light source temperature estimation unit 31 to estimate the temperatures of the laser light sources 101α, 101β, and 101γ corresponding to (equivalent to) the output values ​​of each of the laser light sources 101α, 101β, and 101γ based on the information acquired by the information acquisition unit 30. Specifically, the light source temperature estimation unit 31 reads information regarding the temperature of each laser light source 101α, 101β, 101γ corresponding to the output value and environmental temperature of each laser light source 101α, 101β, 101γ immediately before executing the non-display function, which are input from the light source control unit 26, and estimates this temperature as the temperature of each laser light source 101α, 101β, 101γ immediately before executing the non-display function.

[0072] Next, the control unit 12A stops the operation of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B (step S24). More specifically, when the function instruction receiving unit 28 receives an instruction to execute the non-display function, the control unit 12 controls the light source control unit 26 to stop (turn off) the light emission of the laser light sources 101α, 101β, and 101γ, and controls the element control unit 27 to stop the operation of the display elements 106R, 106G, and 106B or to display them in all black. As a result, the projection display device 100 executes the non-display function, which temporarily hides image projection.

[0073] Next, the control unit 12A operates the element heater 161 to maintain the temperature of each display element 106R, 106G, and 106B (step S25). More specifically, the control unit 12A sets the temperature of each display element 106R, 106G, and 106B immediately before the non-display function is executed as a first element temperature, and controls the element heating control unit 24 to drive each element heater 161 to heat each display element 106R, 106G, and 106B so that each display element 106R, 106G, and 106B maintains this first element temperature. In this case, when the temperature of each display element 106R, 106G, and 106B reaches a second element temperature higher than the first element temperature, the control unit 12 controls the element heating control unit 24 to turn off (stop) the element heater 161. This prevents the display elements 106R, 106G, and 106B from being overheated.

[0074] Next, the control unit 12A drives the light source heater with an output corresponding to the estimated light source temperature based on the information stored in the storage unit 166 (step S26). As described above, the control unit 12A uses the information acquisition unit 30 to acquire information regarding the relationship between the output values ​​of each laser light source 101α, 101β, and 101γ and the temperatures of the laser light sources 101α, 101β, and 101γ, and the relationship between the output value (output) of the light source heater 171 and the temperatures of each laser light source 101α, 101β, and 101γ from the storage unit 166. Then, based on the information acquired by the information acquisition unit 30, the control unit 12A controls the light source heater 171 to an output value of the light source heater 171 that corresponds to the estimated temperature of each laser light source 101α, 101β, and 101γ. As a result, the laser light sources 101α, 101β, and 101γ are heated by the light source heater 171, and are maintained at the temperature immediately before the non-display function is executed, even after the non-display function is executed.

[0075] Next, the control unit 12A determines whether or not an instruction to cancel the non-display function has been issued by the changeover switch 165 (step S27). More specifically, the control unit 12A determines whether or not an instruction to cancel the non-display function has been accepted by the function instruction accepting unit 28 via the changeover switch 165. If it is determined that an instruction to cancel the non-display function has not been issued by the changeover switch 165 (step S27; No), the control unit 12A returns the process to step S25.

[0076] On the other hand, if the changeover switch 165 has instructed to disable the non-display function (step S27; Yes), the control unit 12A resumes the operation of the laser light sources 101α, 101β, and 101γ and the display elements 106R, 106G, and 106B (step S28). More specifically, when the function instruction receiving unit 28 receives an instruction to disable the non-display function, the control unit 12A resumes the operation of turning on (emitting light from) the laser light sources 101α, 101β, and 101γ via the light source control unit 26. The control unit 12A also resumes the operation of turning on the display elements 106R, 106G, and 106B via the element control unit 27. As a result, the non-display function that temporarily disables image projection is canceled in the projection display device 100A, and image projection resumes. At this time, the laser light sources 101α, 101β, 101γ and the display elements 106R, 106G, 106B are maintained at the temperature (e.g., the first element temperature) immediately before the non-display function is executed by the light source heater 171 and the element heater 161. Therefore, when the non-display function is released, the output of the laser light sources 101α, 101β, 101 can be stabilized, and further, the color emitted by the display elements 106R, 106G, 106B can be stabilized, allowing a good image to be projected quickly.

[0077] Next, the control unit 12 stops the operation of the light source heater 171 and the element heater 161 (step S29). More specifically, since the operation of each of the laser light sources 101α, 101β, and 101γ and each of the display elements 106R, 106G, and 106B has resumed, there is no need for further heating, and therefore the light source heating control unit 23 and the element heating control unit 24 stop the operation of the light source heater 171 and the element heater 161. This completes the series of processes.

[0078] The projection display device 100A according to this embodiment has laser light sources 101α, 101β, and 101γ that emit laser light used to project an image, and has a non-display function that temporarily hides the projection of an image by stopping the emission of each of the laser light sources 101α, 101β, and 101γ. The projection display device 100A also has a light source heater 171 that heats each of the laser light sources 101α, 101β, and 101γ, and an information acquisition device that acquires information regarding the relationship between the output value of each of the laser light sources 101α, 101β, and 101γ and the temperature of the laser light source 101α, 101β, and 101γ, and the relationship between the output value of the light source heater 171 and the temperature of each of the laser light sources 101α, 101β, and 101γ. The information acquisition unit 30 includes a control unit 12A that controls the operation of at least each of the laser light sources 101α, 101β, 101γ and the light source heater 171, and a changeover switch 165 that instructs the execution or cancellation of a non-display function. When the changeover switch 165 instructs the execution of the non-display function, the control unit 12 stops the emission of each of the laser light sources 101α, 101β, 101γ, and estimates the temperatures of the laser light sources 101α, 101β, 101γ corresponding to the output values ​​of each of the laser light sources 101α, 101β, 101γ based on the information acquired by the information acquisition unit 30, and controls the light source heater 171 to an output value corresponding to the estimated temperature. According to this configuration, each laser light source 101α, 101β, 101γ can be maintained at the temperature just before the non-display function is executed by the light source heater 171, so when the non-display function is released, the output of each laser light source 101α, 101β, 101γ can be stabilized, allowing a good image to be projected quickly.

[0079] Although the present embodiment has been described above, the present embodiment is not limited to the content of this embodiment. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiment.

[0080] The projection display device of this embodiment can be used as a projection display device using, for example, a reflective liquid crystal display element.

[0081] 10, 10A Display mechanism 12, 12A Control unit 21 Light source temperature acquisition unit 22 Element temperature acquisition unit 23 Light source heating control unit 24 Element heating control unit 25 Fan control unit 26 Light source control unit 27 Element control unit 28 Function instruction reception unit 29 Environmental temperature acquisition unit 30 Information acquisition unit 31 Light source temperature estimation unit 100, 100A Projection display device 101 Light source 101α First blue laser light source 101β Second blue laser light source 101γ Third blue laser light source 106R First display element (liquid crystal display element corresponding to red) 106G Second display element (liquid crystal display element corresponding to green) 106B Third display element (liquid crystal display element corresponding to blue) 160, 170 Heat sink 161 Element heater (element heating unit) 162 Element temperature sensor 164 Fan 165 Changeover switch (switch) 166 Memory unit 171 Light source heater (light source heating unit) 172 Light source temperature sensor

Claims

1. A projection display device having a light source that emits laser light used to project an image, and a non-display function that temporarily hides the projection of the image by stopping the light emission of the light source, comprising: a light source temperature sensor that detects the temperature of the light source; a light source heating unit that heats the light source; a control unit that controls the operation of at least the light source and the light source heating unit; and a switch that instructs the execution or cancellation of the non-display function, wherein when execution of the non-display function is instructed by the switch, the control unit stops the light emission of the light source, obtains the temperature detected by the light source temperature sensor, and controls the light source heating unit so that the light source maintains the obtained temperature.

2. A projection display device having a light source that emits laser light used to project an image, and a non-display function that temporarily hides the projection of the image by stopping the emission of the light source, comprising: a light source heating unit that heats the light source; an information acquisition unit that acquires information regarding the relationship between the output of the light source and the temperature of the light source, and the relationship between the output of the light source heating unit and the temperature of the light source; a control unit that controls the operation of at least the light source and the light source heating unit; and a switch that instructs the execution or cancellation of the non-display function, wherein when execution of the non-display function is instructed by the switch, the control unit stops the emission of the light source, estimates the temperature of the light source corresponding to the output of the light source based on the information acquired by the information acquisition unit, and controls the light source heating unit to an output corresponding to the estimated temperature.

3. A projection display device as claimed in claim 1 or 2, wherein when the switch instructs the cancellation of the non-display function, the control unit starts emitting light from the light source and stops the heating operation of the light source heating unit.

4. A projection display device as described in claim 1 or 2, comprising liquid crystal display elements arranged corresponding to red, green, and blue, respectively, and irradiating the laser light to generate image light corresponding to each color, an element heating unit for heating the liquid crystal display elements, and an element temperature sensor for detecting the temperature of the liquid crystal display elements, wherein when the switch is instructed to execute the non-display function, the control unit stops the operation of the liquid crystal display elements or displays all black, obtains the temperature detected by the element temperature sensor, and controls the element heating unit so that each temperature of the liquid crystal display elements maintains the respectively obtained temperature, and when the switch is instructed to cancel the non-display function, starts the operation of the liquid crystal display elements and stops the heating operation of the element heating unit.

Images