projector

Abstract

To provide a projector that can reduce the occurrence of a trouble due to insects when used outdoors.SOLUTION: A projector of the present invention comprises: an image light generation unit that modulates light emitted from a light source device to generate image light; a projection optical device 21 that projects the image light; a polarization switching element 22 that is arranged on a light emission side of the image light generation unit and switches a polarization state of the image light emitted from the image light generation unit; and a control unit 24 that controls the polarization switching element. The control unit controls the polarization switching element so as to switch the polarization state of the image light at a predetermined interval.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a projector. [Background technology]

[0002] In recent years, projectors have been increasingly used for outdoor applications such as projection mapping, signage, etc. For example, Patent Document 1 listed below discloses a projector intended for outdoor use. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-266190 A Summary of the Invention [Problem to be solved by the invention]

[0004] When projecting an image outdoors using the projector described in the above document, phototactic insects fly in and gather on the projector equipment and the projected image. This can increase the risk of malfunction due to insects entering the projector through the air intake, reduce the display quality due to insects adhering to the lens, and cause viewers to feel uncomfortable due to insects gathering on the projected image. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a projector comprising: an image light generation unit that modulates light emitted from a light source device to generate image light; a projection optical device that projects the image light; a polarization switching element that is arranged on the light emission side of the image light generation unit and switches the polarization state of the image light emitted from the image light generation unit; and a control unit that controls the polarization switching element, wherein the control unit controls the polarization switching element so as to switch the polarization state of the image light at predetermined intervals. [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a projector according to a first embodiment. [Diagram 2] FIG. 4 is a diagram showing a first driving state of the polarization switching element. [Diagram 3] FIG. 13 is a diagram showing a second driving state of the polarization switching element. [Figure 4] 1 is a graph showing the relationship between voltage and polarization change rate in a polarization switching element. [Diagram 5] FIG. 11 is a diagram showing a schematic configuration of a projector according to a second embodiment. [Figure 6] FIG. 13 is a diagram showing a second driving state of the polarization switching element. [Figure 7A] 1 is a graph showing the relationship between voltage and polarization change rate in a polarization switching element. [Figure 7B] 13 is a graph showing the relationship between voltage and polarization change rate in a comparative example. [Figure 8] FIG. 13 is a diagram showing a schematic configuration of a projector according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following drawings, the scale and angle of each member are different from the actual scale and angle in order to make each member large enough to be recognizable.

[0008] (First embodiment) An example of a projector according to this embodiment will be described. FIG. 1 is a diagram showing a schematic configuration of a projector according to this embodiment. 1, the projector 1 of this embodiment includes an image light generating unit 20, a projection optical device 21, a polarization switching element 22, a phase difference element 23, and a control unit 24. The projector 1 is a projection type image display device that displays a color image on a screen SCR.

[0009] The image light generation unit 20 generates image light SL by modulating the light from the light source device 2. The image light generation unit 20 includes the light source device 2, a color separation optical system 3, a light modulation device 4R, a light modulation device 4G, a light modulation device 4B, and a composite prism 5.

[0010] Although not shown, the light source device 2 includes, for example, a laser light source and a wavelength conversion element. The light source device 2 collects blue laser light emitted from the laser light source as excitation light using a collecting lens, causes the light to enter a wavelength conversion element containing a phosphor, and emits white illumination light WL consisting of blue laser light and yellow fluorescence. Note that the light source device 2 is not limited to a configuration using a laser light source and a wavelength conversion element, and may be configured to use, for example, a laser light source alone, or an LED or a discharge type light source lamp.

[0011] The color separation optical system 3 separates the white illumination light WL from the light source device 2 into red light LR, green light LG, and blue light LB. The color separation optical system 3 includes a first dichroic mirror 7a, a second dichroic mirror 7b, a first total reflection mirror 8a, a second total reflection mirror 8b, a third total reflection mirror 8c, and a first relay lens 9a and a second relay lens 9b.

[0012] The first dichroic mirror 7a separates the illumination light WL from the light source device 2 into red light LR and the other light, green light LG and blue light LB. The first dichroic mirror 7a transmits the separated red light LR and reflects the other light. The second dichroic mirror 7b reflects the green light LG and transmits the blue light LB.

[0013] The first total reflection mirror 8a reflects the red light LR toward the optical modulation device 4R. The second total reflection mirror 8b and the third total reflection mirror 8c guide the blue light LB to the optical modulation device 4B. The green light LG is reflected from the second dichroic mirror 7b toward the optical modulation device 4G.

[0014] The first relay lens 9a is disposed after the second dichroic mirror 7b in the optical path of the blue light LB. The second relay lens 9b is disposed after the second total reflection mirror 8b in the optical path of the blue light LB.

[0015] The optical modulation device (first optical modulation device) 4B modulates blue light LB separated from the illumination light WL emitted from the light source device 2 according to image information to form blue modulated light (first light) IB having a blue wavelength band. The optical modulation device (second optical modulation device) 4G modulates green light LG separated from the illumination light WL emitted from the light source device 2 according to image information to form green modulated light (second light) IG having a green wavelength band. The optical modulation device (third optical modulation device) 4R modulates red light LR separated from the illumination light WL emitted from the light source device 2 according to image information to form red modulated light (third light) IR having a red wavelength band. In this embodiment, the blue wavelength band corresponds to, for example, 440 to 490 nm, the green wavelength band corresponds to, for example, 500 to 560 nm, and the red wavelength band corresponds to, for example, 610 to 750 nm.

[0016] In this embodiment, for example, a transmissive liquid crystal panel is used for the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B. Furthermore, a polarizing plate (not shown) is arranged on the light entrance side and the light exit side of the liquid crystal panel, and is configured to pass only linearly polarized light in a specific direction.

[0017] Field lenses 10R, 10G, and 10B are disposed on the incident sides of the optical modulation device 4R, the optical modulation device 4G, and the optical modulation device 4B, respectively. The field lenses 10R, 10G, and 10B collimate the main rays of the red light LR, the green light LG, and the blue light LB incident on the optical modulation device 4R, the optical modulation device 4G, and the optical modulation device 4B, respectively.

[0018] The combining prism 5 combines the lights emitted from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, and emits full-color image light toward the projection optical device 21. The combining prism 5 is, for example, a cross dichroic prism.

[0019] The projection optical device 21 of this embodiment is composed of a plurality of lenses. The projection optical device 21 enlarges and projects the image light SL combined by the combining prism 5 toward the screen SCR. The image light SL includes blue modulated light IB, green modulated light IG, and red modulated light IR emitted from the light modulation device 4R, the light modulation device 4G, and the light modulation device 4B, respectively.

[0020] The polarization switching element 22 is disposed on the light exit side of the image light generation unit 20, i.e., the light exit side of the composite prism 5. In this embodiment, the polarization switching element 22 is disposed on the light exit side of the projection optical device 21. As described later, the polarization switching element 22 switches the polarization state of the image light SL at predetermined intervals. In this embodiment, the polarization switching element 22 is formed of, for example, a liquid crystal panel driven in VA mode. The control unit 24 controls the driving of the polarization switching element 22.

[0021] Here, the blue modulated light IB, the green modulated light IG, and the red modulated light IR are linearly polarized light corresponding to the transmission axes of polarizing plates (not shown) provided on the light exit sides of the optical modulation devices 4B, 4G, and 4R, respectively. The blue modulated light IB and the red modulated light IR have different polarization directions with respect to the separation film of the composite prism 5, from the green modulated light IG. In the case of this embodiment, the blue modulated light IB and the red modulated light IR are transverse waves with respect to the separation film of the combining prism 5, and the green modulated light IG is a longitudinal wave with respect to the separation film of the combining prism 5.

[0022] Therefore, the polarization directions of the blue modulated light IB, the green modulated light IG, and the red modulated light IR constituting the image light SL are not aligned when emitted from the image light generation unit 20. Specifically, the polarization direction of the green modulated light IG differs by 90° from the polarization directions of the blue modulated light IB and the red modulated light IR.

[0023] In the projector 1 of the present embodiment, a phase difference element 23 is provided on the light path of the image light SL emitted from the image light generation unit 20, on the light incident side of the polarization switching element 22. That is, the phase difference element 23 is provided on the light path between the composite prism 5 and the polarization switching element 22. The phase difference element 23 selectively changes the phase of light in one of the blue, green, and red wavelength bands. In this embodiment, the phase difference element 23 imparts a phase difference of 180° to the light in the green wavelength band of the green modulated light IG, and does not impart a phase difference to the blue modulated light IB and the red modulated light IR, which are wavelength bands other than the green wavelength band. In this way, the phase difference element 23 is composed of, for example, a half-wave plate having wavelength selectivity.

[0024] As described above, the phase difference element 23 imparts a phase difference of 180° only to the green modulated light IG of the image light SL. As a result, the polarization direction of the green modulated light IG is rotated by 90°, and the polarization directions of the green modulated light IG, the blue modulated light IB, and the red modulated light IR are aligned. In this manner, in the projector 1 of the present embodiment, the phase difference element 23 disposed on the light incident side of the polarization switching element 22 can align the polarization directions of the blue modulated light IB, the green modulated light IG, and the red modulated light IR that constitute the image light SL in one direction.

[0025] As described above, the blue modulated light IB, green modulated light IG and red modulated light IR constituting the image light SL are incident on the polarization switching element 22 with the same polarization direction, i.e., as linearly polarized light. Hereinafter, the image light SL converted into linearly polarized light by the phase difference element 23 and incident on the polarization switching element 22 will be referred to as "image light SL1." In this embodiment, the image light SL1 is assumed to be incident on the polarization switching element 22 as linearly polarized light that becomes a transverse wave with respect to the horizontal plane.

[0026] 2 and 3 are diagrams conceptually explaining the polarization switching operation by the polarization switching element 22. FIG. Fig. 2 is a diagram showing a first driving state of the polarization switching element 22. Fig. 3 is a diagram showing a second driving state of the polarization switching element 22. For simplicity of explanation, it is assumed that when the polarization switching element 22 is in the first driving state, no phase difference is imparted to the image light SL1, and when the polarization switching element 22 is in the second driving state, a phase difference of 180° is imparted to the image light SL1.

[0027] 2, when the polarization switching element 22 is in the first drive state, no phase difference is applied to the image light SL1. Therefore, when the polarization switching element 22 is in the first drive state, the rate of change in the polarization state of the image light SL1 emitted from the polarization switching element 22 (hereinafter simply referred to as the "polarization change rate") is 0%. Here, a polarization change rate of 0% means, for example, that light incident on the polarization switching element 22 as a transverse wave is emitted from the polarization switching element 22 as a transverse wave. That is, when the polarization switching element 22 is in the first drive state, the image light SL1 is emitted from the polarization switching element 22 as a transverse wave SLs.

[0028] On the other hand, when the control unit 24 switches the polarization switching element 22 to the second drive state, a phase difference of 180° is applied to the image light SL1, as shown in Fig. 3. Therefore, when the polarization switching element 22 is in the second drive state, the polarization change rate of the image light SL1 is 100%. Here, a polarization change rate of 100% means, for example, that light incident on the polarization switching element 22 as a transverse wave is emitted from the polarization switching element 22 as a longitudinal wave with respect to the horizontal plane. That is, when the polarization switching element 22 is in the second driving state, the image light SL1 is emitted from the polarization switching element 22 as a longitudinal wave SLp.

[0029] Note that the longitudinal wave SLp and the transverse wave SLs in the image light SL1 have an inverse relationship with respect to the polarization direction with respect to the separation film of the composite prism 5, which is perpendicular to the horizontal plane. That is, the longitudinal wave SLp is a transverse wave with respect to the separation film of the composite prism 5, and the transverse wave SLs is a longitudinal wave with respect to the separation film of the composite prism 5.

[0030] In this embodiment, the control unit 24 controls the polarization switching element 22 to switch between the first driving state and the second driving state at a predetermined interval. The control unit 24 switches the driving state of the polarization switching element 22 at a frequency of 1 to 20 Hz. This allows the polarization state of the image light SL1 emitted from the polarization switching element 22 to be switched between a transverse wave SLs and a longitudinal wave SLp at a predetermined interval.

[0031] Here, to a person who cannot see polarized light, the transverse waves SLs and longitudinal waves SLp in the image light SL1, which are alternately emitted at a predetermined interval, are seen as a normal image. On the other hand, it is known that insects can visually recognize longitudinal waves and transverse waves as light and dark. For example, when an insect visually recognizes the light of the transverse waves SLs as a dark area and the light of the longitudinal waves SLp as a bright area, the insect visually recognizes the transverse waves SLs or the longitudinal waves SLp in the image light SL1 alternately emitted at a predetermined interval as blinking light. Since insects dislike and avoid blinking light, the image light SL1 emitted from the polarization switching element 22 can have an insect repellent effect. Examples of insects having such characteristics include insects with phototaxis, such as Diptera (midges) and Lepidoptera (moths).

[0032] Incidentally, in the above explanation with reference to Figures 2 and 3, for the sake of simplicity, it has been assumed that when the driving state of the polarization switching element 22 is switched, the polarization change rate of the polarization switching element 22 switches between 0% and 100%.

[0033] However, the VA mode liquid crystal panel constituting the polarization switching element 22 may have a characteristic that the polarization change rate varies depending on the wavelength band of the incident light, as described later. Hereinafter, a method for enhancing the insect repellent effect described above when the polarization switching element 22 has a characteristic in which the polarization change rate varies depending on the wavelength band of the incident light will be specifically described.

[0034] Fig. 4 is a graph showing the relationship between voltage and polarization change rate in a VA mode liquid crystal panel constituting polarization switching element 22. In Fig. 4, the horizontal axis shows the voltage (unit: V) applied to the liquid crystal panel, and the vertical axis shows the polarization change rate (unit: %) of light emitted from the liquid crystal panel when voltage is applied. Fig. 4 also shows the relationship between voltage and polarization change rate for light in the blue wavelength band, green wavelength band, and red wavelength band.

[0035] 4 is equivalent to the relationship between voltage and transmittance when polarizing plates are arranged in a crossed Nicol configuration on the light entrance side and light exit side of the VA mode liquid crystal panel that constitutes the polarization switching element 22. For example, a polarization change rate of 100% corresponds to a transmittance of 100% when the polarization switching element 22 is used as a transmissive panel, and a polarization change rate of 0% corresponds to a transmittance of 0%.

[0036] As described above, the control unit 24 of this embodiment controls the polarization switching element 22 to switch between the first driving state and the second driving state. In the first driving state, the control unit 24 controls the polarization switching element 22 to apply the first voltage V1, and in the second driving state, the control unit 24 controls the polarization switching element 22 to apply the second voltage V2. As shown in Fig. 4, for example, the first voltage V1 is set to 0V, and the second voltage V2 is set to 2.8V.

[0037] In the first driving state in which the first voltage V1 is applied, the polarization switching element 22 does not impart a phase difference to the incident light, and therefore the polarization change rate of the polarization switching element 22 is 0%. At this time, as shown in FIG. 2, the image light SL1 is emitted from the polarization switching element 22 as a transverse wave SLs.

[0038] Here, in the first driving state in which the first voltage V1 is applied, the polarization change rate of the polarization switching element 22 is 0% regardless of the wavelength band of the incident light. Therefore, when the first voltage V1 is applied, there is no difference in the phase difference of the image light SL1 transmitted through the polarization switching element 22 for each wavelength band. Therefore, the image light SL1, which is a transverse wave SLs, is visually recognized by insects as a dark area with no difference in brightness regardless of the wavelength band.

[0039] 4, when the applied voltage is higher than 2 V, the polarization switching element 22 has a different polarization change rate depending on the wavelength band of the incident light. When the second voltage V2 is set to 2.8 V, the polarization change rate for light in the blue wavelength band is 100%, but the polarization change rate for light in the green wavelength band is about 80%, which is lower than 100%, and the polarization change rate for light in the red wavelength band is even lower, closer to 70%.

[0040] As described above, the image light SL1 is light that includes blue modulated light IB, green modulated light IG, and red modulated light IR, so that the polarization change rate of the polarization switching element 22 in the second driving state for the blue component (blue modulated light IB) contained in the image light SL1 is 100%. That is, the blue component (blue modulated light IB) contained in the image light SL1 is given a phase difference of 180° by transmitting through the polarization switching element 22 in the second driving state. Therefore, the blue component (blue modulated light IB) contained in the image light SL1 is emitted from the polarization switching element 22 as a longitudinal wave.

[0041] In contrast, in the polarization switching element 22 in the second driving state, the polarization change rate for the green component (green modulated light IG) and the red component (red modulated light IR) of the image light SL1 is lower than 100%. Therefore, when the green component (green modulated light IG) and the red component (red modulated light IR) contained in the image light SL1 are transmitted through the polarization switching element 22 in the second driving state, the phase difference given to them becomes smaller than 180°. As a result, the green component (green modulated light IG) and the red component (red modulated light IR) contained in the image light SL1 are emitted from the polarization switching element 22 as elliptically polarized light rather than as a longitudinal wave.

[0042] Here, compared with the blue component (blue modulated light IB) converted from a transverse wave to a longitudinal wave, the green component (green modulated light IG) and red component (red modulated light IR) converted from a transverse wave to an elliptically polarized light have a smaller degree of change in polarization state, which may reduce the contrast ratio due to the flashing of light from the image light SL1 perceived by insects.

[0043] In general, insects are known to have a higher visibility to blue light than to green and red light. The present inventors have focused on the difference in visibility to colored light of insects. In the present embodiment, the control unit 24 controls the polarization switching element 22 so that the polarization change rate for the blue modulated light IB is greater than the polarization change rates for the green modulated light IG and the red modulated light IR.

[0044] Specifically, in this embodiment, the second voltage V2 applied in the second driving state is set to 2.8V, so that the polarization change rate for the blue modulated light IB is made larger than the polarization change rates for the green modulated light IG and the red modulated light IR. This allows the polarization state of the blue component, which has the highest visibility to insects, to be preferentially set to 100%, thereby converting the polarization state of the blue component from a transverse wave to a longitudinal wave. Therefore, when the driving state of the polarization switching element 22 is switched, the degree of change in the polarization state of the blue component can be maximized. Therefore, since it becomes relatively difficult for insects to perceive blinking light caused by green and red components, they are able to mainly perceive blinking light caused by the blue component, which has the highest visual sensitivity. Therefore, according to this embodiment, even if a liquid crystal panel having a property in which the polarization change rate varies depending on the wavelength band of the incident light is used as the polarization switching element 22, the image light SL1 can be visually recognized by insects as a strong flashing light, thereby sufficiently enhancing the repellent effect.

[0045] The effects of this embodiment will be described below. The projector 1 of this embodiment includes an image light generation unit 20 that modulates light emitted from the light source device 2 to generate image light SL1, a projection optical device 21 that projects the image light SL1, a polarization switching element 22 that is arranged on the light emission side of the image light generation unit 20 and switches the polarization state of the image light SL1 emitted from the image light generation unit 20, and a control unit 24 that controls the polarization switching element 22, and the control unit 24 controls the polarization switching element 22 so as to switch the polarization state of the image light SL at predetermined intervals.

[0046] According to this embodiment, the polarization state of the image light SL1 is switched to a transverse wave SLs or a longitudinal wave SLp at a predetermined interval and then emitted, so that the image light SL can be visually recognized by insects as blinking light. Since insects having phototaxis dislike and avoid blinking light, the image light SL1 emitted from the polarization switching element 22 can have an insect repellent effect. Therefore, according to this embodiment, it is possible to reduce the occurrence of problems caused by insects when used outdoors.

[0047] In this embodiment, the image light generation unit 20 includes an optical modulation device 4B that modulates the light from the light source device 2 in accordance with image information to generate blue modulated light IB, an optical modulation device 4G that modulates the light from the light source device 2 in accordance with image information to generate green modulated light IG, an optical modulation device 4R that modulates the light from the light source device 2 in accordance with image information to generate red modulated light IR, and a combining prism 5 that combines the blue modulated light IB, the green modulated light IG, and the red modulated light IR to generate image light SL1.

[0048] According to this configuration, the illumination light WL from the light source device 2 can be modulated to generate full-color image light SL1.

[0049] In this embodiment, a phase difference element 23 is provided on the optical path between the composite prism 5 and the polarization switching element 22, and selectively changes the phase of light in one of the blue wavelength band, the green wavelength band, and the red wavelength band.

[0050] According to this configuration, the image light SL1 can be converted into linearly polarized light and made incident on the polarization switching element 22.

[0051] In this embodiment, the polarization switching element 22 has a property that the polarization change rate of the image light SL1 varies depending on the wavelength band of the incident light, and the control unit 24 controls the polarization switching element 22 so that the polarization change rate for the blue modulated light IB is greater than the polarization change rates for the green modulated light IG and the red modulated light IR.

[0052] This configuration maximizes the degree of change in the polarization state of the blue component, which has the highest visibility to insects. This allows insects to recognize the blinking of blue light, which has the highest visibility, even when the contrast ratio of the blinking light of the green and red components is relatively low, so that a high repelling effect can be obtained even when a liquid crystal panel with a characteristic that the polarization change rate differs depending on the wavelength band of the incident light is used.

[0053] In the present embodiment, the frequency at which the control unit 24 switches the polarization state of the image light SL1 is 1 to 20 Hz. According to this configuration, the blinking light can be efficiently recognized by insects, and an insect repellent effect can be effectively obtained.

[0054] In this embodiment, the polarization switching element 22 is composed of a liquid crystal panel. In this case, the insect repellent effect can be obtained by simply and reliably switching the polarization state of the image light SL1.

[0055] In this embodiment, the polarization switching element 22 is disposed on the light exit side of the projection optical device 21 . According to this configuration, the polarization switching element 22 is attached to the light exit side of the projection optical device 21, i.e., to the outside of the projection optical device 21. In this case, the projector of the present invention can be realized by attaching a polarization switching element to the outside of the projection optical device of an existing projector device. Therefore, the configuration of the projector of the present invention can be realized without significantly changing the configuration of a conventional projector device, and as a result, the cost of the projector 1 of this embodiment can be reduced.

[0056] Furthermore, according to the projector 1 of this embodiment, since insects are less likely to gather around the projector 1, it is possible to reduce the risk of failure due to insects getting inside the projector, and to suppress the deterioration of cooling performance due to clogging of the filter provided at the intake port of the cooling mechanism. Therefore, it is possible to reduce the risk of adversely affecting the display quality and reliability. It is also possible to prevent the deterioration of the display quality and reduce maintenance costs such as filter replacement.

[0057] Furthermore, according to the projector 1 of this embodiment, since insects are less likely to gather around the projector 1, it is possible to suppress degradation of display quality caused by insects attaching to the projection optical device 21.

[0058] Furthermore, according to the projector 1 of this embodiment, insects are less likely to gather around the projected image, which makes it less likely that visual discomfort will be caused, and reduces the risk of compromising the original purpose of the projector, such as allowing spectators and passersby to view projection mapping or signage.

[0059] Insects can also cause allergies and other health problems. In contrast, the projector 1 of this embodiment makes it difficult for insects to gather around the projected image, reducing the health risks to users, including the operator and viewers, and providing a safer and more comfortable visual communication environment.

[0060] Second embodiment An example of a projector according to the second embodiment will be described below. Note that the same reference numerals are used to designate the same components as those in the above embodiment, and detailed descriptions thereof will be omitted. FIG. 5 is a diagram showing a schematic configuration of a projector according to this embodiment. As shown in FIG. 5, the projector 101 of this embodiment includes an image light generating section 120, a projection optical device 21, a polarization switching element 122, a polarizing plate 25, and a control section .

[0061] The image light generation section 120 of this embodiment includes a light source device 2, a color wheel 30, and a light modulation device . White illumination light WL emitted from light source device 2 is incident on color wheel 30. Color wheel 30 is formed in a disk shape with a rotation axis O at the center of the disk. A drive device 30M such as an electric motor is connected to the rotation axis O of color wheel 30, and color wheel 30 is rotated in the circumferential direction by drive device M. Color wheel 30 is provided with color filters such as thin-film interference filters that transmit red, green, and blue color light along the circumferential direction. The red, green, and blue color lights are emitted from color wheel 30 in a time-division manner.

[0062] The red, green, and blue color lights emitted from the color wheel 30 in a time-division manner are incident on the light modulation device 40. The light modulation device 40 of this embodiment is a micromirror type light modulation device, and for example, a DMD (Digital Micromirror Device) is used. The DMD has a configuration in which multiple micromirrors are arranged in a matrix. The DMD switches the tilt direction of multiple micromirrors to quickly switch the reflection direction of the incident light between a direction in which the light enters the projection optical device 21 and a direction in which the light does not enter the projection optical device 21. In this way, the image light generation unit 120 of this embodiment sequentially modulates the illumination light WL emitted from the light source device 2, and generates the image light SL3 by emitting the blue modulated light IB1, the green modulated light IG1, and the red modulated light IR1 in a time-division manner. Hereinafter, the blue modulated light IB1, the green modulated light IG1, and the red modulated light IR1 may be collectively referred to simply as "modulated light IB1, IG1, IR1".

[0063] The polarizing plate 25 is provided on the optical path between the light source device 2 of the image light generating section 120 and the polarization switching element 122. In the case of this embodiment, the polarizing plate 25 is disposed on the light exit side of the projection optical device 21.

[0064] In this embodiment, each of the modulated lights IB1, IG1, and IR1 constituting the image light SL3 emitted from the image light generation unit 120 is unpolarized. Each of the modulated lights IB1, IG1, and IR1 is converted into a transverse wave (linearly polarized light) with respect to the horizontal plane by transmitting through the polarizing plate 25. Each of the modulated lights IB1, IG1, and IR1 transmitted through the polarizing plate 25 is incident on the polarization switching element 122. Hereinafter, the light generated by each of the modulated lights IB1, IG1, and IR1 transmitted through the polarizing plate 25 and emitted in a time-division manner will be referred to as "image light SL4." The image light SL4 is incident on the polarization switching element 122 as linearly polarized light.

[0065] The polarization switching element 122 is disposed on the light exit side of the image light generation section 120. In this embodiment, the polarization switching element 122 is disposed on the light exit side of the projection optical device 21. The polarization switching element 122 switches the polarization state of the image light SL4 at a predetermined interval. In this embodiment, the polarization switching element 122 is configured with, for example, a liquid crystal panel that operates in TN mode. The polarization switching element 122 is driven by the control unit 24 so as to switch between a first driving state and a second driving state.

[0066] First, to simplify the explanation, when the polarization switching element 122 is in the first driving state, a phase difference of 180° is imparted to the image light SL4, and when the polarization switching element 122 is in the second driving state, no phase difference is imparted to the image light SL4.

[0067] 5, when the polarization switching element 122 is in the first drive state, a phase difference of 180° is applied to the image light SL4. Therefore, when the polarization switching element 122 is in the first drive state, the image light SL4 is emitted from the polarization switching element 122 as a longitudinal wave SLp1 relative to the horizontal plane.

[0068] FIG. 6 is a diagram showing the second driving state of the polarization switching element 122. As shown in FIG. On the other hand, when the control unit 24 switches the polarization switching element 122 to the second drive state, no phase difference is applied to the image light SL4, as shown in Fig. 6. Therefore, when the polarization switching element 122 is in the second drive state, the image light SL4 is emitted from the polarization switching element 122 as a transverse wave SLs1 with respect to the horizontal plane.

[0069] In this embodiment, the control unit 24 switches the driving state of the polarization switching element 122 at a frequency of 1 to 20 Hz. This makes it possible to switch the polarization state of each color light constituting the image light SL4 emitted in a time-division manner from the polarization switching element 122 between a longitudinal wave SLp1 and a transverse wave SLs1 at predetermined intervals. This allows insects to see the image light SL4 with different polarization states alternately emitted at a predetermined interval as blinking light, thereby achieving an insect repellent effect.

[0070] 5 and 6, for simplicity's sake, it has been assumed that the polarization change rate in the polarization switching element 122 switches between 0% and 100% when the driving state of the polarization switching element 122 is switched. However, the TN mode liquid crystal panel constituting the polarization switching element 122 of this embodiment may have characteristics in which the polarization change rate differs depending on the wavelength band of the incident light, as described later.

[0071] Hereinafter, a method for further enhancing the insect repellent effect described above when the polarization switching element 122 has a different polarization change rate depending on the wavelength band of the incident light will be described.

[0072] Fig. 7A is a graph showing the relationship between voltage and polarization change rate in a TN mode liquid crystal panel that constitutes polarization switching element 122. Fig. 7B is a graph showing the relationship between voltage and polarization change rate in another TN mode liquid crystal panel as a comparative example.

[0073] 7A and 7B, the horizontal axis indicates the voltage (unit: V) applied to the liquid crystal panel, and the vertical axis indicates the polarization change rate (unit: %) of light emitted from the liquid crystal panel when a voltage is applied. Also, Fig. 7A and Fig. 7B show the relationship between the voltage and the polarization change rate for light in the blue wavelength band, green wavelength band, and red wavelength band, respectively.

[0074] In this embodiment, the control unit 24 controls the polarization switching element 122 to apply 1.0 V as the first voltage V1 in the first driving state, and 4.5 V as the second voltage V2 in the second driving state, as shown in FIG. 7A.

[0075] In the case of this embodiment, in the second driving state in which the second voltage V2 is applied, the polarization switching element 122 does not impart a phase difference to the incident light, so the polarization change rate of the polarization switching element 122 is 0%. At this time, the image light SL4 is emitted from the polarization switching element 122 as a transverse wave SLs1.

[0076] Here, in the second driving state in which the second voltage V2 is applied, the polarization change rate of the polarization switching element 122 is 0% regardless of the wavelength band of the incident light. Therefore, when the second voltage V2 is applied, there is no difference in phase difference between wavelength bands of the image light SL4 transmitted through the polarization switching element 122. Therefore, the image light SL4, which is the transverse wave SLs1, is visually recognized by the insect as a dark area with no difference in brightness regardless of the wavelength band.

[0077] On the other hand, as shown in Fig. 7A, in the first driving state in which the first voltage V1 lower than the second voltage V2 is applied, the polarization switching element 122 has a different polarization change rate depending on the wavelength band of the incident light. When the first voltage V1 is 1.0 V, the polarization change rate for light in the blue wavelength band is approximately 100%, but the polarization change rate for light in the green wavelength band is lower than 100%, and the polarization change rate for light in the red wavelength band is even lower. In other words, the polarization switching element 122 does not have a polarization change rate of 100% for light in the green and red wavelength bands.

[0078] In this embodiment, the polarization switching element 122 in the first driving state has a polarization change rate of approximately 100% for light in the blue wavelength band (blue modulated light IB), which is part of the image light SL4. That is, a phase difference of 180° is imparted to the light in the blue wavelength band of the image light SL4 (blue modulated light IB) when it passes through the polarization switching element 122. Therefore, the light in the blue wavelength band of the image light SL4 is emitted from the polarization switching element 122 as a longitudinal wave.

[0079] On the other hand, the polarization switching element 122 in the first driving state has a polarization change rate lower than 100% for the light in the green wavelength band (green modulated light IG) and the light in the red wavelength band (red modulated light IR) of the image light SL4. Therefore, the phase difference given to the light in the green wavelength band (green modulated light IG) and the light in the red wavelength band (red modulated light IR) is smaller than 180°. Therefore, the green component (green modulated light IG) and the red component (red modulated light IR) are emitted from the polarization switching element 122 as elliptically polarized light.

[0080] As described above, insects have a higher visibility to light in the blue wavelength band than to light in the green or red wavelength bands. The inventors focused on the difference in visibility of insects depending on the color of light, and used a liquid crystal panel for the polarization switching element 122 of this embodiment in which the cell thickness or refractive index difference Δn of the liquid crystal panel was selected so that the polarization change rate for light in the blue wavelength band was larger than the polarization change rate for light in the green or red wavelength bands.

[0081] In the liquid crystal panel of the comparative example shown in FIG. 7B, the polarization change rate for light in the green wavelength band is the highest, so the insect repellent effect is lower than that of the liquid crystal panel used in the polarization switching element 122 of this embodiment. In the liquid crystal panel of the comparative example shown in FIG. 7B, for example, a convex portion where the polarization change rate of the blue component is the highest occurs near an applied voltage of 1.8 V due to the Morgan condition. Therefore, it is also possible to use an applied voltage of around 1.8 V as the first driving state. However, in this case, the difference between the polarization change rate of light in the green wavelength band and the polarization change rate of light in the red wavelength band increases, making it difficult to obtain a sufficient insect repellent effect. In contrast, the panel characteristics of the polarization switching element 122 of this embodiment shown in FIG. 7A are such that the polarization change rate for light in the blue wavelength band is the highest, as described above, and the difference in the polarization change rate between the green wavelength band and the red wavelength band is small, making it more preferable as a liquid crystal panel that provides an insect repellent effect.

[0082] As described above, according to the projector 101 of this embodiment, since it is equipped with the polarization switching element 122 composed of a liquid crystal panel having the above-mentioned characteristics, it is possible to effectively increase the contrast ratio when the image light visible to insects is blinking, thereby further enhancing the insect repellent effect.

[0083] The present invention has been described above based on the above-mentioned embodiment, but the present invention is not limited to the above-mentioned embodiment and can be embodied in various forms without departing from the spirit of the present invention.

[0084] For example, in both of the above embodiments, the polarization switching elements 22, 122 are provided in the rear stage of the projection optical device 21, but the present invention is not limited to this. For example, as shown in Fig. 8, in the configuration of the projector 1 of the first embodiment, the polarization switching element 22 and the phase difference element 23 may be disposed in the front stage (light entrance side) of the projection optical device 21. Similarly, in the configuration of the projector 101 of the second embodiment, the polarization switching element 122 and the polarizing plate 25 may be disposed in the front stage (light entrance side) of the projection optical device 21.

[0085] In the above embodiment, the VA and TN modes are taken as examples of the drive modes of the liquid crystal panels constituting the polarization switching elements 22 and 122. However, for example, when a luminous flux response is required, the OCB mode may be used. In the above embodiment, the values ​​of the first voltage V1 and the second voltage V2 applied to the polarization switching elements 22 and 122 are not particularly limited, and can be appropriately changed to optimal values ​​depending on the characteristics of the liquid crystal panel used in the polarization switching elements. In addition, in the above embodiment, an example was given of a case in which the polarization state of the image light is controlled by two voltage values ​​that switch between longitudinal waves and transverse waves, but it is also possible to adopt a form in which the polarization state of the image light is switched between three or more voltage values ​​including circular polarization. In addition, in the above embodiment, an example was given of the image light generation unit 20, 120 generating full-color image light using illumination light WL from the light source device 2, but an image light generation unit that generates single-color image light of any one of blue, green, and red may also be used.

[0086] In addition, in the second embodiment, an example was given of a case in which the polarization state of the image light SL4 is converted into a transverse wave with respect to the horizontal plane using the polarizing plate 25, but the polarization state of the image light SL4 may also be converted into a longitudinal wave with respect to the horizontal plane and made incident on the polarization switching element 122.

[0087] A projector according to an aspect of the invention may have the following configuration. A projector according to one embodiment of the present invention comprises an image light generation unit that modulates light emitted from a light source device to generate image light, a projection optical device that projects the image light, a polarization switching element that is arranged on the light emission side of the image light generation unit and switches the polarization state of the image light emitted from the image light generation unit, and a control unit that controls the polarization switching element, wherein the control unit controls the polarization switching element so as to switch the polarization state of the image light at predetermined intervals.

[0088] In one embodiment of the projector of the present invention, the image light generation section may be configured to include a first light modulation device that modulates light from the light source device in accordance with image information to generate first light having a blue wavelength band, a second light modulation device that modulates light from the light source device in accordance with image information to generate second light having a green wavelength band, a third light modulation device that modulates light from the light source device in accordance with image information to generate third light having a red wavelength band, and a combining prism that combines the first light, second light, and third light to generate image light.

[0089] In one embodiment of the projector of the present invention, the projector may be configured to include a phase difference element that is provided on the optical path between the composite prism and the polarization switching element and selectively changes the phase of light in one of the blue wavelength band, the green wavelength band, and the red wavelength band.

[0090] In one embodiment of the projector of the present invention, the polarization switching element may have a property in which the polarization change rate of the image light varies depending on the wavelength band of the incident light, and the control unit may be configured to control the polarization switching element so that the polarization change rate for the first light is greater than the polarization change rates for the second light and the third light.

[0091] In one embodiment of the projector of the present invention, the image light generation section may be configured to generate image light by modulating light from the light source device in accordance with image information and emitting a first light having a blue wavelength band, a second light having a green wavelength band, and a third light having a red wavelength band in a time-division manner.

[0092] The projector according to one aspect of the invention may be configured to further include a polarizing plate provided on the optical path between the light source device of the image light generating section and the polarization switching element.

[0093] In the projector according to one aspect of the invention, the control unit may switch the polarization state of the image light at a frequency of 1 to 20 Hz.

[0094] In the projector according to one aspect of the invention, the polarization switching element may be configured as a liquid crystal panel.

[0095] In the projector according to one aspect of the invention, the polarization switching element may be arranged on the light exit side of the projection optical device. [Explanation of symbols]

[0096] 1,101...projector, 2...light source device, 4B...light modulation device (first light modulation device), 4G...light modulation device (second light modulation device), 4R...light modulation device (third light modulation device), 5...combining prism, 20,120...image light generation unit, 21...projection optical device, 22,122...polarization switching element, 23...phase difference element, 24...control unit, 25...polarizing plate, 40...light modulation device, IB...blue modulated light (first light), IG...green modulated light (second light), IR...red modulated light (third light), SL, SL1, SL3, SL4...image light.

Claims

1. an image light generating unit that generates image light by modulating light emitted from a light source device; a projection optical device that projects the image light; a polarization switching element disposed on a light exit side of the image light generation unit and configured to switch a polarization state of the image light exited from the image light generation unit; A control unit that controls the polarization switching element, the image light includes a first light having a blue wavelength band, a second light having a green wavelength band, and a third light having a red wavelength band; the control unit controls the polarization switching element so as to switch the polarization state of the image light at predetermined intervals; the polarization switching element has a characteristic that a polarization change rate for the image light varies depending on a wavelength band of the incident light, the control unit controls a voltage applied to the polarization switching element so that the polarization change rate for the first light is greater than the polarization change rates for the second light and the third light. A projector characterized by:

2. The image light generation unit includes: a first light modulation device that modulates light from the light source device in accordance with image information to generate the first light; a second light modulation device that modulates the light from the light source device in accordance with image information to generate the second light; a third light modulation device that modulates the light from the light source device in accordance with image information to generate the third light; a synthesis prism that synthesizes the first light, the second light, and the third light to generate the image light, 2. The projector according to claim 1,

3. A phase difference element is provided on an optical path between the synthetic prism and the polarization switching element, and selectively changes the phase of light in any one of the blue wavelength band, the green wavelength band, and the red wavelength band.

3. The projector according to claim 2.

4. the image light generation unit modulates light from the light source device in accordance with image information, and emits the first light, the second light, and the third light in a time-division manner to generate the image light.

2. The projector according to claim 1,

5. a polarizing plate provided on an optical path between the light source device of the image light generating unit and the polarization switching element; 5. The projector according to claim 4.

6. The frequency at which the control unit switches the polarization state of the image light is 1 to 20 Hz. The projector according to any one of claims 1 to 5.

7. The polarization switching element is composed of a liquid crystal panel. The projector according to any one of claims 1 to 6.

8. The polarization switching element is disposed on the light exit side of the projection optical device. The projector according to any one of claims 1 to 7.

9. An image light generating unit that generates image light by modulating light emitted from a light source device; a projection optical device that projects the image light; a polarization switching element disposed on a light exit side of the image light generation unit and configured to switch a polarization state of the image light exited from the image light generation unit; A control unit that controls the polarization switching element, the control unit controls the polarization switching element so as to switch the polarization state of the image light at predetermined intervals; The frequency at which the control unit switches the polarization state of the image light is 1 to 20 Hz. A projector characterized by:

Images