Projector

Abstract

To suppress deterioration in hue and reduction in brightness due to reduction in rotation efficiency particularly in a red band when using an optical path shifting device.SOLUTION: The projector includes a first liquid crystal panel configured to modulate light in a first wavelength band to generate first image light, a second liquid crystal panel configured to modulate light in a second wavelength band having a center wavelength longer than a center wavelength of the first wavelength band to generate second image light, a light combining element configured to combine the first image light and the second image light to generate combined image light, a projection optical system configured to project the combined image light, and an optical shift device configured to shift an optical path of at least one of the first image light, the second image light, and the combined image light. A thickness of a liquid crystal layer of the second liquid crystal panel is larger than a thickness of a liquid crystal layer of the first liquid crystal panel, and a frame rate of the first liquid crystal panel is larger than a frame rate of the second liquid crystal panel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses an optical path shift device including a glass plate into which light enters a rectangular optical region in a planar view, a first actuator that displaces the glass plate around a first axis that passes through the center of the optical region in a planar view and forms an angle of less than 90° with a first side of the optical region, and a second actuator that displaces the glass plate around a second axis that passes through the center of the optical region and is perpendicular to the first axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-82000 Summary of the Invention [Problem to be solved by the invention]

[0004] When using the light path shift device described in Patent Document 1, it is preferable that the liquid crystal have a fast response speed. One way to increase the response speed of the liquid crystal is to reduce the thickness of the liquid crystal layer. However, reducing the thickness of the liquid crystal layer shifts the peak wavelength at which the rotation efficiency of the liquid crystal is maximized to the shorter wavelength side. As a result, the rotation efficiency in the red wavelength band in particular decreases, leading to a deterioration in color (excessively high color deviation) and a decrease in brightness. [Means for solving the problem]

[0005] One embodiment of the projector of the present invention comprises a first liquid crystal panel that modulates light in a first wavelength band to generate first image light, a second liquid crystal panel that modulates light in a second wavelength band having a center wavelength longer than the center wavelength of the first wavelength band to generate second image light, a light combining element that combines the first image light and the second image light to generate combined image light, a projection optical system that projects the combined image light, and an optical shift device that shifts the optical path of at least one of the first image light, the second image light, and the combined image light, wherein the thickness of the liquid crystal layer of the second liquid crystal panel is greater than the thickness of the liquid crystal layer of the first liquid crystal panel, and the frame rate of the first liquid crystal panel is greater than the frame rate of the second liquid crystal panel. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a projector 1 according to a first embodiment. [Figure 2] 2 is a diagram showing a glass plate 24a of a two-axis shift device 24 as viewed from a dichroic prism 23. FIG. [Figure 3] FIG. 10 is a diagram showing how the positions on the XY plane of pixels PX included in the composite image light LC change in accordance with the rotation of the glass plate 24a. [Figure 4] 4 is a timing chart showing the operation of the projector 1 of the first embodiment. [Figure 5] FIG. 10 is a diagram showing a configuration of an optical shift device 50B according to a second embodiment. [Figure 6] FIG. 2 is a diagram showing a glass plate 26a of a uniaxial shift device 26 as viewed from a liquid crystal panel 22R. [Figure 7] FIG. 10 is a diagram showing how the position on the XY plane of the pixel PXr included in the red image light LR changes in accordance with the rotation of the glass plate 26a. [Figure 8] FIG. 10 is a diagram showing how the position on the XY plane of pixel PXg included in green image light LG and the position on the XY plane of pixel PXb included in blue image light LB change in response to the rotation of glass plate 24a. [Figure 9]10 is a timing chart showing the operation of the projector according to the second embodiment. [Figure 10] 10 is a timing chart showing a modified example of the operation of the projector of the second embodiment. [Figure 11] FIG. 10 is a diagram showing a configuration of an optical shift device 50C according to a third embodiment. [Figure 12] FIG. 2 is a diagram showing a glass plate 27a of a uniaxial shift device 27 as viewed from a liquid crystal panel 22R. [Figure 13] FIG. 10 is a diagram showing how the position on the XY plane of a pixel PXr included in red image light LR changes in response to the rotation of a glass plate 27a. [Figure 14] 10 is a timing chart showing the operation of a projector according to a third embodiment. [Figure 15] FIG. 10 is a diagram showing a configuration of an optical shift device 50D according to a fourth embodiment. [Figure 16] 10 is a timing chart showing the operation of a projector according to a fourth embodiment. [Figure 17] FIG. 10 is a diagram showing a configuration of an optical shift device 50E according to a fifth embodiment. [Figure 18] 10 is a timing chart showing the operation of a projector according to a fifth embodiment. [Figure 19] FIG. 13 is a diagram showing a configuration of an optical shift device 50F according to a sixth embodiment. [Figure 20] 13 is a timing chart showing the operation of a projector according to a sixth embodiment. [Figure 21] FIG. 10 is a diagram showing a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each component may be different from the actual scale in order to make each component large enough to be recognizable.

[0008] [First embodiment] FIG. 1 is a diagram showing a schematic configuration of a projector 1 according to a first embodiment. As shown in FIG. 1, the projector 1 includes an optical device 10 and a control device 30. The control device 30 controls the optical device 10 based on a video signal supplied from a video supply device (not shown). The optical device 10 projects composite image light LC corresponding to an image based on the video signal onto a projection screen SC. The video supply device is, for example, a personal computer, a tablet terminal, or a DVD (Digital Versatile Disc) player.

[0009] The optical device 10 includes a light source 11, two dichroic mirrors 12 and 13, three reflecting mirrors 14, 15 and 16, five relay lenses 17, 18, 19, 20 and 21, three liquid crystal panels 22R, 22G and 22B, a dichroic prism 23, an optical shift device 50A, and a projection optical system 25.

[0010] The light source 11 emits white light L0 to the dichroic mirror 12. The light source 11 is, for example, a halogen lamp, a mercury lamp, a light emitting diode, or a laser light source.

[0011] The dichroic mirror 12 separates the white light L0 into a first color light L1 and a second color light L2. For example, the first color light L1 is red light, and the second color light L2 is a mixed color of green and blue. The dichroic mirror 12 outputs the first color light L1 to the reflecting mirror 14 and the second color light L2 to the dichroic mirror 13.

[0012] The dichroic mirror 13 separates the second color light L2 into a third color light L3 and a fourth color light L4. For example, the third color light L3 is green light, and the fourth color light L4 is blue light. The dichroic mirror 13 outputs the third color light L3 to a relay lens 18 and the fourth color light L4 to a relay lens 19.

[0013] The first color light L1 emitted from the dichroic mirror 12 is incident on the liquid crystal panel 22R via the reflecting mirror 14 and the relay lens 17. The third color light L3 emitted from the dichroic mirror 13 is incident on the liquid crystal panel 22G via the relay lens 18. The fourth color light L4 emitted from the dichroic mirror 13 is incident on the liquid crystal panel 22B via the relay lens 19, the reflecting mirror 15, the relay lens 20, the reflecting mirror 16, and the relay lens 21.

[0014] The liquid crystal panels 22R, 22G, and 22B function as light modulation devices in the projector 1. For example, the liquid crystal panels 22R, 22G, and 22B are active-drive liquid crystal panels having a plurality of pixels arranged in a matrix. The control device 30 controls the transmittance of the pixels of each of the liquid crystal panels 22R, 22G, and 22B based on a video signal.

[0015] The liquid crystal panel 22G modulates the green third color light L3 to generate green image light LG. The liquid crystal panel 22G is an example of a first liquid crystal panel that modulates light in a first wavelength band to generate first image light. That is, in this embodiment, the green third color light L3 is an example of light in the first wavelength band, and the green image light LG is an example of the first image light.

[0016] The liquid crystal panel 22R modulates the first red color light L1 to generate red image light LR. The liquid crystal panel 22R is an example of a second liquid crystal panel that modulates light of a second wavelength band having a longer center wavelength than the center wavelength of the first wavelength band to generate second image light. That is, in this embodiment, the first red color light L1 is an example of light of the second wavelength band, and the red image light LR is an example of second image light.

[0017] The liquid crystal panel 22B modulates the fourth blue color light L4 to generate blue image light LB. The liquid crystal panel 22B is an example of a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light. That is, in this embodiment, the fourth blue color light L4 is an example of light in the third wavelength band, and the blue image light LB is an example of the third image light.

[0018] In this embodiment, the thickness of the liquid crystal layer of the liquid crystal panel 22R is greater than that of the liquid crystal panel 22G. Specifically, the thickness of the liquid crystal layer of the liquid crystal panel 22R is such that the peak wavelength at which the rotation efficiency of the liquid crystal panel 22R is maximized is included in the wavelength band of the first red colored light L1. Furthermore, the thickness of the liquid crystal layer of the liquid crystal panel 22G is such that the peak wavelength at which the rotation efficiency of the liquid crystal panel 22G is maximized is included in the wavelength band of the third green colored light L3.

[0019] The rotation efficiency is the rate at which linearly polarized light incident on the liquid crystal layer is converted into linearly polarized light perpendicular to the original linearly polarized light. Rotation efficiency is also sometimes referred to as polarization conversion efficiency. As the thickness of the liquid crystal layer decreases, the peak wavelength at which the rotation efficiency is maximized shifts toward shorter wavelengths. The red wavelength band is located on the longer wavelength side than the green wavelength band. Therefore, if the liquid crystal layer thickness of the liquid crystal panel 22R is set to a thickness at which the peak wavelength at which the rotation efficiency of the liquid crystal panel 22R is maximized falls within the red wavelength band, and the liquid crystal layer thickness of the liquid crystal panel 22G is set to a thickness at which the peak wavelength at which the rotation efficiency of the liquid crystal panel 22G is maximized falls within the green wavelength band, the liquid crystal layer thickness of the liquid crystal panel 22R will be greater than that of the liquid crystal panel 22G.

[0020] In this embodiment, the thickness of the liquid crystal layer of the liquid crystal panel 22B is smaller than that of the liquid crystal panel 22G. Specifically, the thickness of the liquid crystal layer of the liquid crystal panel 22B is such that the peak wavelength at which the rotation efficiency of the liquid crystal panel 22B is maximized is included in the wavelength band of the fourth blue colored light L4. The blue wavelength band is shorter than the green wavelength band. Therefore, if the thickness of the liquid crystal layer of the liquid crystal panel 22B is such that the peak wavelength at which the rotation efficiency of the liquid crystal panel 22B is maximized is included in the blue wavelength band, the thickness of the liquid crystal layer of the liquid crystal panel 22B will be smaller than that of the liquid crystal panel 22G.

[0021] The dichroic prism 23 generates a composite image light LC by combining the red image light LR emitted from the liquid crystal panel 22R, the green image light LG emitted from the liquid crystal panel 22G, and the blue image light LB emitted from the liquid crystal panel 22B. The dichroic prism 23 is an example of a light combining element.

[0022] The optical shift device 50A shifts the optical path of at least one of the red image light LR, the green image light LG, and the combined image light LC. The optical shift device 50A in this embodiment includes a two-axis shift device 24 that shifts the optical path of the combined image light LC output from the dichroic prism 23 along two axes. The two-axis shift device 24 is disposed between the dichroic prism 23 and the projection optical system 25.

[0023] The two-axis shift device 24 has a glass plate 24a, which is a translucent optical member that transmits the composite image light LC. The two-axis shift device 24 changes the orientation of the glass plate 24a, thereby shifting the optical path of the composite image light LC by utilizing refraction of light. The composite image light LC emitted from the dichroic prism 23 enters the projection optical system 25 via the two-axis shift device 24. The projection optical system 25 enlarges and projects the composite image light LC onto the projection screen SC. By projecting the composite image light LC onto the projection screen SC, an image based on a video signal is displayed on the projection screen SC.

[0024] 2 is a diagram showing the glass plate 24a of the two-axis shift device 24 as seen from the dichroic prism 23. As shown in FIG. 2, the combined image light LC emitted from the dichroic prism 23 passes through the glass plate 24a. In FIG. 2, the X axis is the horizontal axis of the combined image light LC, and the Y axis is the vertical axis of the combined image light LC. The X axis corresponds to the horizontal axis of the liquid crystal panels 22R, 22G, and 22B, and the Y axis corresponds to the vertical axis of the liquid crystal panels 22R, 22G, and 22B.

[0025] The direction indicated by each arrow along the X-axis and Y-axis is the + direction, and the direction opposite to the + direction is the - direction. In the following explanation, the +X direction may be referred to as the right or right side, and the -X direction as the left or left side. The +Y direction may be referred to as the up or upper side, and the -Y direction as the down or lower side.

[0026] 2, in the two-axis shift device 24, the glass plate 24a is disposed so as to be rotatable around a first axis J1 and a second axis J2. The first axis J1 is perpendicular to the central axis C1 of the composite image light LC and is tilted at 45 degrees counterclockwise with respect to the X-axis. The second axis J2 is perpendicular to the central axis C1 of the composite image light LC and is tilted at 90 degrees with respect to the first axis J1.

[0027] 2, the two-axis shift device 24 has a first actuator 24b that rotates the glass plate 24a about a first axis J1 and a second actuator 24c that rotates the glass plate 24a about a second axis J2. The operations of the first actuator 24b and the second actuator 24c are controlled by a control device 30.

[0028] In the following description, the rotation angle around the first axis J1 will be referred to as the first rotation angle θ1, and the rotation angle around the second axis J2 will be referred to as the second rotation angle θ2. Fig. 2 shows the state of the glass plate 24a when both the first rotation angle θ1 and the second rotation angle θ2 are 0 degrees. When both the first rotation angle θ1 and the second rotation angle θ2 are 0 degrees, the glass plate 24a is parallel to the XY plane and perpendicular to the central axis C1 of the composite image light LC.

[0029] In the following description, the state of the glass plate 24a when both the first rotation angle θ1 and the second rotation angle θ2 are 0 degrees is referred to as the reference state. When the glass plate 24a in this reference state rotates around the first axis J1 in the direction indicated by arrow D1, the first rotation angle θ1 becomes a positive value. On the other hand, when the glass plate 24a in the reference state rotates around the first axis J1 in the direction opposite to the direction indicated by arrow D1, the first rotation angle θ1 becomes a negative value. When the glass plate 24a in the reference state rotates around the second axis J2 in the direction indicated by arrow D2, the second rotation angle θ2 becomes a positive value. On the other hand, when the glass plate 24a in the reference state rotates around the second axis J2 in the direction opposite to the direction indicated by arrow D2, the second rotation angle θ2 becomes a negative value.

[0030] 3 is a diagram showing how the position on the XY plane of pixel PX included in the composite image light LC changes in response to the rotation of the glass plate 24a. When the glass plate 24a is in the reference state, that is, when both the first rotation angle θ1 and the second rotation angle θ2 are 0 degrees, the position of pixel PX is defined as the reference position P0 of pixel PX. Note that, as an example, the position of pixel PX is the position of the center point of pixel PX.

[0031] When the first rotation angle θ1 is a positive first angle a1 and the second rotation angle θ2 is 0 degrees, the pixel PX is positioned at a first position P1, which is shifted half a pixel to the upper left from the reference position P0. When the first rotation angle θ1 is 0 degrees and the second rotation angle θ2 is a positive third angle b1, the pixel PX is positioned at a second position P2, which is shifted half a pixel to the upper right from the reference position P0. When the first rotation angle θ1 is a negative second angle a2 and the second rotation angle θ2 is 0 degrees, the pixel PX is positioned at a third position P3, which is shifted half a pixel to the lower right from the reference position P0. When the first rotation angle θ1 is 0 degrees and the second rotation angle θ2 is a negative fourth angle b2, the pixel PX is positioned at a fourth position P4, which is shifted half a pixel to the lower left from the reference position P0.

[0032] The specific configuration of the two-axis shift device 24 that shifts the optical path of the composite image light LC along two axes in this manner is publicly known as described in Japanese Patent Application Laid-Open No. 2022-82000. Therefore, in this specification, a description of the specific configuration of the two-axis shift device 24 will be omitted.

[0033] Figure 4 is a timing chart showing the temporal correspondence between the position of the pixel PX included in the composite image light LC, the first rotation angle θ1, the second rotation angle θ2, the drive timing of the liquid crystal panels 22R, 22G and 22B, and the rotation efficiency of the liquid crystal panels 22R, 22G and 22B.

[0034] In Figure 4, "position (R)" indicates the position of the pixel PX included in the composite image light LC. "Drive timing (R)" indicates the drive timing of the liquid crystal panel 22R. "Drive timing (GB)" indicates the drive timing of the liquid crystal panels 22G and 22B. "Er" indicates the rotation efficiency of the liquid crystal panel 22R. "Eg" indicates the rotation efficiency of the liquid crystal panel 22G. "Eb" indicates the rotation efficiency of the liquid crystal panel 22B.

[0035] 4, during the period from time t0 to time t1, the control device 30 controls the first actuator 24b to change the first rotation angle θ1 of the glass plate 24a from 0 degrees to a positive first angle a1. Furthermore, during the period from time t0 to time t1, the control device 30 controls the second actuator 24c to change the second rotation angle θ2 of the glass plate 24a from a negative fourth angle b2 to 0 degrees. As a result, during the period from time t0 to time t1, the pixel PX included in the composite image light LC shifts from the fourth position P4 toward the first position P1.

[0036] When the first rotation angle θ1 reaches the positive first angle a1 at time t1, the control device 30 controls the first actuator 24b to maintain the first rotation angle θ1 at the positive first angle a1 during the period from time t1 to time t2. Furthermore, when the second rotation angle θ2 reaches 0 degrees at time t1, the control device 30 controls the second actuator 24c to maintain the second rotation angle θ2 at 0 degrees during the period from time t1 to time t2. As a result, the positions of the pixels PX included in the composite image light LC are maintained at the first positions P1 during the period from time t1 to time t2.

[0037] During the period from time t2 to time t3, the control device 30 controls the first actuator 24b to change the first rotation angle θ1 of the glass plate 24a from the positive first angle a1 to 0 degrees. Furthermore, during the period from time t2 to time t3, the control device 30 controls the second actuator 24c to change the second rotation angle θ2 of the glass plate 24a from 0 degrees to the positive third angle b1. As a result, during the period from time t2 to time t3, the pixel PX included in the composite image light LC shifts from the first position P1 toward the second position P2.

[0038] When the first rotation angle θ1 reaches 0 degrees at time t3, the control device 30 controls the first actuator 24b to maintain the first rotation angle θ1 at 0 degrees during the period from time t3 to time t4. Furthermore, when the second rotation angle θ2 reaches the positive third angle b1 at time t3, the control device 30 controls the second actuator 24c to maintain the second rotation angle θ2 at the positive third angle b1 during the period from time t3 to time t4. As a result, the positions of the pixels PX included in the composite image light LC are maintained at the second positions P2 during the period from time t3 to time t4.

[0039] During the period from time t4 to time t5, the control device 30 controls the first actuator 24b to change the first rotation angle θ1 of the glass plate 24a from 0 degrees to a negative second angle a2. Furthermore, during the period from time t4 to time t5, the control device 30 controls the second actuator 24c to change the second rotation angle θ2 of the glass plate 24a from a positive third angle b1 to 0 degrees. As a result, during the period from time t4 to time t5, the pixel PX included in the composite image light LC shifts from the second position P2 toward the third position P3.

[0040] When the first rotation angle θ1 reaches the negative second angle a2 at time t5, the control device 30 controls the first actuator 24b to maintain the first rotation angle θ1 at the negative second angle a2 during the period from time t5 to time t6. Furthermore, when the second rotation angle θ2 reaches 0 degrees at time t5, the control device 30 controls the second actuator 24c to maintain the second rotation angle θ2 at 0 degrees during the period from time t5 to time t6. As a result, the positions of the pixels PX included in the composite image light LC are maintained at the third positions P3 during the period from time t5 to time t6.

[0041] During the period from time t6 to time t7, the control device 30 controls the first actuator 24b to change the first rotation angle θ1 of the glass plate 24a from the negative second angle a2 to 0 degrees. Furthermore, during the period from time t6 to time t7, the control device 30 controls the second actuator 24c to change the second rotation angle θ2 of the glass plate 24a from 0 degrees to the negative fourth angle b2. As a result, during the period from time t6 to time t7, the pixel PX included in the composite image light LC shifts from the third position P3 toward the fourth position P4.

[0042] When the first rotation angle θ1 reaches 0 degrees at time t7, the control device 30 controls the first actuator 24b to maintain the first rotation angle θ1 at 0 degrees from time t7 to time t8. Furthermore, when the second rotation angle θ2 reaches the negative fourth angle b2 at time t7, the control device 30 controls the second actuator 24c to maintain the second rotation angle θ2 at the negative fourth angle b2 from time t7 to time t8. As a result, the position of the pixel PX included in the composite image light LC is maintained at the fourth position P4 from time t7 to time t8.

[0043] After time t8, the control device 30 repeats the operations performed during the period from time t0 to time t8. For example, during the period from time t8 to time t9, the control device 30 controls the first actuator 24b to change the first rotation angle θ1 of the glass plate 24a from 0 degrees to a positive first angle a1. Furthermore, during the period from time t8 to time t9, the control device 30 controls the second actuator 24c to change the second rotation angle θ2 of the glass plate 24a from a negative fourth angle b2 to 0 degrees. As a result, during the period from time t8 to time t9, the pixel PX included in the composite image light LC shifts from the fourth position P4 toward the first position P1.

[0044] The period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector 1. The frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector 1. The frame rate of the liquid crystal panels 22G and 22B is twice the frame rate of the liquid crystal panel 22R. In other words, the frame rate of the liquid crystal panels 22G and 22B is four times the frame rate of the video signal.

[0045] The control device 30 controls the drive timing of the liquid crystal panels 22G and 22B so that the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm and the rotation efficiency Eb of the liquid crystal panel 22B becomes the maximum value Ebm during the period when the pixel PX included in the composite image light LC is located at the first position P1, the second position P2, the third position P3, and the fourth position P4.

[0046] For example, during a first period from time t0 to time t2, the control device 30 applies a voltage corresponding to an image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the first period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the first period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0047] During a second period from time t2 to time t4, the control device 30 applies a voltage corresponding to the image to be displayed at the second position P2 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the second period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the second position P2 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the second period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the second position P2 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0048] During a third period from time t4 to time t6, the control device 30 applies a voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the third period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the third period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0049] During a fourth period from time t6 to time t8, the control device 30 applies a voltage corresponding to the image to be displayed at the fourth position P4 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the fourth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the fourth position P4 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the fourth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the fourth position P4 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0050] As described above, by the control device 30 controlling the drive timing of the liquid crystal panels 22G and 22B, during the period when the pixels PX included in the composite image light LC are located at the first position P1, the second position P2, the third position P3, and the fourth position P4, the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm, and the rotation efficiency Eb of the liquid crystal panel 22B becomes the maximum value Ebm.

[0051] On the other hand, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during the period when the pixel PX included in the composite image light LC is located at the first position P1 and the third position P3.

[0052] For example, during a fifth period from the center time (not shown) of the fourth period of the previous frame to the center time of the second period of the current frame, the control device 30 applies a voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R. Specifically, during the first half of the fifth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R. During the second half of the fifth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R.

[0053] During a sixth period from the center of the second period to the center of the fourth period, the control device 30 applies a voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R. Specifically, during the first half of the sixth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R. During the second half of the sixth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R.

[0054] As described above, the control device 30 controls the drive timing of the liquid crystal panel 22R, so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during the period when the pixel PX included in the composite image light LC is located at the first position P1 and the third position P3.

[0055] The thinner the liquid crystal layer, the faster the response speed of the liquid crystal layer. Therefore, the time from the start of application of the positive polarity voltage until the rotation efficiency reaches its maximum value is shorter for liquid crystal panels 22G and 22B than for liquid crystal panel 22R. Furthermore, the time from the end of application of the negative polarity voltage until the rotation efficiency reaches its minimum value is also shorter for liquid crystal panels 22G and 22B than for liquid crystal panel 22R.

[0056] 4, during the period when the pixel PX included in the composite image light LC is located at the second position P2 and the fourth position P4, the increasing region and the decreasing region of the rotation efficiency Er of the liquid crystal panel 22R overlap. Therefore, during the period when the pixel PX included in the composite image light LC is located at the second position P2 and the fourth position P4, the red image is not turned off, but it is considered that no significant color breakup from red to cyan occurs.

[0057] As described above, the projector 1 of the first embodiment includes the liquid crystal panel 22G that modulates the green third color light L3 to generate the green image light LG, the liquid crystal panel 22R that modulates the red first color light L1 to generate the red image light LR, the dichroic prism 23 that combines the green image light LG and the red image light LR to generate the combined image light LC, the projection optical system 25 that projects the combined image light LC, and the optical shift device 50A that shifts the optical path of at least one of the green image light LG, the red image light LR, and the combined image light LC. The thickness of the liquid crystal layer of the liquid crystal panel 22R is greater than the thickness of the liquid crystal layer of the liquid crystal panel 22G. The frame rate of the liquid crystal panel 22G is greater than the frame rate of the liquid crystal panel 22R.

[0058] When using the light path shift device 50A described above, it is preferable that the liquid crystal have a fast response speed. One way to increase the response speed of the liquid crystal is to reduce the thickness of the liquid crystal layer. However, reducing the thickness of the liquid crystal layer shifts the peak wavelength at which the rotation efficiency of the liquid crystal is maximized to the shorter wavelength side. As a result, the rotation efficiency in the red wavelength band in particular decreases, leading to a deterioration in color (excessively high color deviation) and a decrease in brightness.

[0059] To solve the problems caused by using the light path shift device 50A, the first embodiment employs a configuration in which the thickness of the liquid crystal layer of the liquid crystal panel 22R is greater than that of the liquid crystal panel 22G. This configuration prevents a decrease in the rotation efficiency of the liquid crystal panel 22R, which modulates the first red color light L1 to generate the red image light LR. Meanwhile, because the thickness of the liquid crystal layer of the liquid crystal panel 22R is greater than that of the liquid crystal panel 22G, the response speed of the liquid crystal panel 22R is slower than that of the liquid crystal panel 22G. In contrast, the first embodiment employs a configuration in which the frame rate of the liquid crystal panel 22G is greater than that of the liquid crystal panel 22R. In other words, because the frame rate of the liquid crystal panel 22R is slower than that of the liquid crystal panel 22G, a slow response speed of the liquid crystal panel 22R does not pose a problem. As described above, according to the first embodiment, when the light path shift device 50A is used, it is possible to prevent deterioration in color tone and brightness due to a decrease in the rotation efficiency, particularly in the red wavelength band. This effect can also be obtained in the second to sixth embodiments described below.

[0060] In the projector 1 of the first embodiment, the optical shift device 50A includes a two-axis shift device 24 that shifts the optical path of the composite image light LC along two axes, and the frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector 1, and the frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. According to the first embodiment, when the optical shift device 50A includes a two-axis shift device 24 that shifts the optical path of the composite image light LC along two axes, it is possible to suppress deterioration in color tone and brightness due to a decrease in the rotation efficiency, particularly in the red wavelength band.

[0061] The projector 1 of the first embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, and a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate combined image light LC, and the frame rate of the liquid crystal panel 22B is twice the frame rate of the liquid crystal panel 22R. According to this first embodiment, when the projector 1 further includes the liquid crystal panel 22B, it is possible to achieve high definition images projected from the projector 1 while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0062] [Second embodiment] Next, a second embodiment of the present disclosure will be described. The projector of the second embodiment differs from the projector 1 of the first embodiment in that it includes an optical shift device 50B that is different from the optical shift device 50A described in the first embodiment. Therefore, the second embodiment will be described below while focusing on the optical shift device 50B, which is a difference from the first embodiment.

[0063] 5 is a diagram showing the configuration of an optical shift device 50B in the second embodiment. As shown in FIG. 5, the optical shift device 50B includes a one-axis shift device 26, a first two-axis shift device 24G, and a second two-axis shift device 24B.

[0064] The uniaxial shift device 26 is disposed between the liquid crystal panel 22R and the dichroic prism 23. The uniaxial shift device 26 shifts the optical path of the red image light LR emitted from the liquid crystal panel 22R along one axis.

[0065] The uniaxial shift device 26 has a glass plate 26a, which is a translucent optical member that transmits the red image light LR. The uniaxial shift device 26 shifts the optical path of the red image light LR by changing the orientation of the glass plate 26a and utilizing refraction of light. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic prism 23 via the uniaxial shift device 26.

[0066] The first two-axis shift device 24G is disposed between the liquid crystal panel 22G and the dichroic prism 23. The first two-axis shift device 24G shifts the optical path of the green image light LG emitted from the liquid crystal panel 22G along two axes. The configuration of the first two-axis shift device 24G is the same as the configuration of the two-axis shift device 24 described in the first embodiment. That is, the first two-axis shift device 24G has a glass plate 24a that transmits the green image light LG. The first two-axis shift device 24G shifts the optical path of the green image light LG by utilizing the refraction of light by changing the orientation of the glass plate 24a. The green image light LG emitted from the liquid crystal panel 22G enters the dichroic prism 23 via the first two-axis shift device 24G.

[0067] The second two-axis shift device 24B is disposed between the liquid crystal panel 22B and the dichroic prism 23. The second two-axis shift device 24B shifts the optical path of the blue image light LB emitted from the liquid crystal panel 22B along two axes. The configuration of the second two-axis shift device 24B is the same as the configuration of the two-axis shift device 24 described in the first embodiment. That is, the second two-axis shift device 24B has a glass plate 24a that transmits the blue image light LB. The second two-axis shift device 24B shifts the optical path of the blue image light LB by utilizing the refraction of light by changing the orientation of the glass plate 24a. The blue image light LB emitted from the liquid crystal panel 22B enters the dichroic prism 23 via the second two-axis shift device 24B.

[0068] The dichroic prism 23 combines the red image light LR incident through the single-axis shift device 26, the green image light LG incident through the first two-axis shift device 24G, and the blue image light LB incident through the second two-axis shift device 24B to generate combined image light LC.

[0069] Fig. 6 is a diagram showing the glass plate 26a of the uniaxial shift device 26 as seen from the liquid crystal panel 22R. As shown in Fig. 6, the red image light LR emitted from the liquid crystal panel 22R passes through the glass plate 26a. In the uniaxial shift device 26, the glass plate 26a is disposed so as to be rotatable around a third axis J3. The third axis J3 is perpendicular to the central axis C2 of the red image light LR and is tilted at an angle of 45 degrees counterclockwise with respect to the X-axis.

[0070] As shown in FIG. 6, the single-axis shift device 26 has a third actuator 26b that rotates the glass plate 26a around a third axis J3. The operation of the third actuator 26b is controlled by the control device 30. In the following description, the rotation angle around the third axis J3 is referred to as the third rotation angle θ3. FIG. 6 shows the state of the glass plate 26a when the third rotation angle θ3 is 0 degrees. When the third rotation angle θ3 is 0 degrees, the glass plate 26a is parallel to the XY plane and perpendicular to the central axis C2 of the red image light LR.

[0071] In the following description, the state of the glass plate 26a when the third rotation angle θ3 is 0 degrees is referred to as the reference state. When the glass plate 26a in this reference state rotates around the third axis J3 in the direction indicated by arrow D3, the third rotation angle θ3 becomes a positive value. On the other hand, when the glass plate 26a in the reference state rotates around the third axis J3 in the direction opposite to the direction indicated by arrow D3, the third rotation angle θ3 becomes a negative value.

[0072] 7 is a diagram showing how the position on the XY plane of pixel PXr included in red image light LR changes in response to the rotation of glass plate 26a. When glass plate 26a is in the reference state, that is, when the third rotation angle θ3 is 0 degrees, the position of pixel PXr is defined as the reference position P0 of pixel PXr. Note that, as an example, the position of pixel PXr is the position of the center point of pixel PXr.

[0073] When the third rotation angle θ3 is a positive fifth angle c1, the position of pixel PXr is a first position P1, which is shifted half a pixel to the upper left from the reference position P0. When the third rotation angle θ3 is a negative sixth angle c2, the position of pixel PXr is a third position P3, which is shifted half a pixel to the lower right from the reference position P0.

[0074] The specific configuration of the uniaxial shift device 26 that shifts the optical path of the red image light LR along one axis in this manner is publicly known as described in JP 2018-54974 A. Therefore, in this specification, a description of the specific configuration of the uniaxial shift device 26 will be omitted.

[0075] 8 is a diagram showing how the position on the XY plane of pixel PXg included in green image light LG and the position on the XY plane of pixel PXb included in blue image light LB change according to the rotation of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B. The positions of pixels PXg and PXb when both the first rotation angle θ1 and the second rotation angle θ2 are 0 degrees are defined as the reference position P0 of pixel PX.

[0076] When the first rotation angle θ1 is a positive first angle a1 and the second rotation angle θ2 is 0 degrees, the pixels PXg and PXb are positioned at a first position P1, which is shifted half a pixel to the upper left from the reference position P0. When the first rotation angle θ1 is 0 degrees and the second rotation angle θ2 is a positive third angle b1, the pixels PXg and PXb are positioned at a second position P2, which is shifted half a pixel to the upper right from the reference position P0. When the first rotation angle θ1 is a negative second angle a2 and the second rotation angle θ2 is 0 degrees, the pixels PXg and PXb are positioned at a third position P3, which is shifted half a pixel to the lower right from the reference position P0. When the first rotation angle θ1 is 0 degrees and the second rotation angle θ2 is a negative fourth angle b2, the pixels PXg and PXb are positioned at a fourth position P4, which is shifted half a pixel to the lower left from the reference position P0.

[0077] Figure 9 is a timing chart showing the temporal correspondence between the positions of pixels PXr, PXg, and PXb, the first rotation angle θ1, the second rotation angle θ2, the third rotation angle θ3, the drive timing of liquid crystal panels 22R, 22G, and 22B, and the rotation efficiency of liquid crystal panels 22R, 22G, and 22B.

[0078] In Figure 9, "position (R)" indicates the position of pixel PXr included in red image light LR. "position (GB)" indicates the position of pixel PXg included in green image light LG and the position of pixel PXb included in blue image light LB. "Drive timing (R)" indicates the drive timing of liquid crystal panel 22R. "Drive timing (GB)" indicates the drive timing of liquid crystal panels 22G and 22B. "Er" indicates the rotation efficiency of liquid crystal panel 22R. "Eg" indicates the rotation efficiency of liquid crystal panel 22G. "Eb" indicates the rotation efficiency of liquid crystal panel 22B.

[0079] From time t0 to time t1, the control device 30 controls the first actuator 24b of the first biaxial shift device 24G to change the first rotation angle θ1 of the glass plate 24a of the first biaxial shift device 24G from 0 degrees to a positive first angle a1. Also, from time t0 to time t1, the control device 30 controls the second actuator 24c of the first biaxial shift device 24G to change the second rotation angle θ2 of the glass plate 24a of the first biaxial shift device 24G from a negative fourth angle b2 to 0 degrees. From time t0 to time t1, the control device 30 controls the second biaxial shift device 24B in the same manner as the first biaxial shift device 24G. As a result, from time t0 to time t1, the pixel PXg included in the green image light LG and the pixel PXb included in the blue image light LB shift from the fourth position P4 toward the first position P1.

[0080] At time t1, when the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G reaches the positive first angle a1, the control device 30 controls the first actuator 24b of the first two-axis shift device 24G to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G at the positive first angle a1 from time t1 to time t2. Also, at time t1, when the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G reaches 0 degrees, the control device 30 controls the second actuator 24c of the first two-axis shift device 24G to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G at 0 degrees from time t1 to time t2. During the period from time t1 to time t2, the control device 30 controls the second two-axis shift device 24B in the same manner as the first two-axis shift device 24G. As a result, during the period from time t1 to time t2, the position of the pixel PXg included in the green image light LG and the position of the pixel PXb included in the blue image light LB are maintained at the first position P1.

[0081] From time t2 to time t3, the control device 30 controls the first actuator 24b of the first two-axis shift device 24G to change the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G from a positive first angle a1 to 0 degrees. Also, from time t2 to time t3, the control device 30 controls the second actuator 24c of the first two-axis shift device 24G to change the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G from 0 degrees to a positive third angle b1. From time t2 to time t3, the control device 30 controls the second two-axis shift device 24B in the same way as the first two-axis shift device 24G. As a result, from time t2 to time t3, the pixel PXg included in the green image light LG and the pixel PXb included in the blue image light LB shift from the first position P1 toward the second position P2.

[0082] At time t3, when the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G reaches 0 degrees, the control device 30 controls the first actuator 24b of the first two-axis shift device 24G to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G at 0 degrees from time t3 to time t4. Also, at time t3, when the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G reaches the positive third angle b1, the control device 30 controls the second actuator 24c of the first two-axis shift device 24G to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G at the positive third angle b1 from time t3 to time t4. During the period from time t3 to time t4, the control device 30 controls the second two-axis shift device 24B in the same manner as the first two-axis shift device 24G. As a result, during the period from time t3 to time t4, the position of the pixel PXg included in the green image light LG and the position of the pixel PXb included in the blue image light LB are maintained at the second position P2.

[0083] From time t4 to time t5, the control device 30 controls the first actuator 24b of the first biaxial shift device 24G to change the first rotation angle θ1 of the glass plate 24a of the first biaxial shift device 24G from 0 degrees to a negative second angle a2. Also, from time t4 to time t5, the control device 30 controls the second actuator 24c of the first biaxial shift device 24G to change the second rotation angle θ2 of the glass plate 24a of the first biaxial shift device 24G from a positive third angle b1 to 0 degrees. From time t4 to time t5, the control device 30 controls the second biaxial shift device 24B in the same manner as the first biaxial shift device 24G. As a result, from time t4 to time t5, the pixel PXg included in the green image light LG and the pixel PXb included in the blue image light LB shift from the second position P2 toward the third position P3.

[0084] At time t5, when the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G reaches the negative second angle a2, the control device 30 controls the first actuator 24b of the first two-axis shift device 24G to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G at the negative second angle a2 from time t5 to time t6. Also, at time t5, when the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G reaches 0 degrees, the control device 30 controls the second actuator 24c of the first two-axis shift device 24G to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G at 0 degrees from time t5 to time t6. During the period from time t5 to time t6, the control device 30 controls the second two-axis shift device 24B in the same manner as the first two-axis shift device 24G. As a result, during the period from time t5 to time t6, the position of the pixel PXg included in the green image light LG and the position of the pixel PXb included in the blue image light LB are maintained at the third position P3.

[0085] From time t6 to time t7, the control device 30 controls the first actuator 24b of the first biaxial shift device 24G to change the first rotation angle θ1 of the glass plate 24a of the first biaxial shift device 24G from the negative second angle a2 to 0 degrees. Also, from time t6 to time t7, the control device 30 controls the second actuator 24c of the first biaxial shift device 24G to change the second rotation angle θ2 of the glass plate 24a of the first biaxial shift device 24G from 0 degrees to the negative fourth angle b2. From time t6 to time t7, the control device 30 controls the second biaxial shift device 24B in the same manner as the first biaxial shift device 24G. As a result, from time t6 to time t7, the pixel PXg included in the green image light LG and the pixel PXb included in the blue image light LB shift from the third position P3 toward the fourth position P4.

[0086] At time t7, when the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G reaches 0 degrees, the control device 30 controls the first actuator 24b of the first two-axis shift device 24G to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G at 0 degrees from time t7 to time t8. Also, at time t7, when the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G reaches the negative fourth angle b2, the control device 30 controls the second actuator 24c of the first two-axis shift device 24G to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G at the negative fourth angle b2 from time t7 to time t8. During the period from time t7 to time t8, the control device 30 controls the second two-axis shift device 24B in the same manner as the first two-axis shift device 24G. As a result, during the period from time t7 to time t8, the position of the pixel PXg included in the green image light LG and the position of the pixel PXb included in the blue image light LB are at the fourth position P4.

[0087] In the period from time t0 to time t1, the control device 30 controls the third actuator 26b of the uniaxial shift device 26 to change the third rotation angle θ3 of the glass plate 26a of the uniaxial shift device 26 from the negative sixth angle c2 to the positive fifth angle c1. As a result, the pixel PXr included in the red image light LR shifts from the third position P3 toward the first position P1.

[0088] When the third rotation angle θ3 reaches the positive fifth angle c1 at time t1, the control device 30 controls the third actuator 26b of the uniaxial shift device 26 to maintain the third rotation angle θ3 of the glass plate 26a of the uniaxial shift device 26 at the positive fifth angle c1 during the period from time t1 to time t4. As a result, the position of the pixel PXr included in the red image light LR is maintained at the first position P1 during the period from time t1 to time t4.

[0089] In the period from time t4 to time t5, the control device 30 controls the third actuator 26b of the uniaxial shift device 26 to change the third rotation angle θ3 of the glass plate 26a of the uniaxial shift device 26 from the positive fifth angle c1 to the negative sixth angle c2. As a result, the pixel PXr included in the red image light LR shifts from the first position P1 toward the third position P3.

[0090] When the third rotation angle θ3 reaches the negative sixth angle c2 at time t5, the control device 30 controls the third actuator 26b of the uniaxial shift device 26 to maintain the third rotation angle θ3 of the glass plate 26a of the uniaxial shift device 26 at the negative sixth angle c2 during the period from time t5 to time t8. As a result, during the period from time t5 to time t8, the position of the pixel PXr included in the red image light LR emitted from the uniaxial shift device 26 is maintained at the third position P3.

[0091] After time t8, the control device 30 repeats the operations performed during the period from time t0 to time t8. For example, during the period from time t8 to time t9, the control device 30 changes the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from 0 degrees to a positive first angle a1. During the period from time t8 to time t9, the control device 30 changes the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from a negative fourth angle b2 to 0 degrees. During the period from time t8 to time t9, the control device 30 changes the third rotation angle θ3 of the glass plate 26a of the single-axis shift device 26 from a negative sixth angle c2 to a positive fifth angle c1.

[0092] In Figure 9, the period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector of the second embodiment. The frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector of the second embodiment. The frame rates of the liquid crystal panels 22G and 22B are twice the frame rate of the liquid crystal panel 22R. In other words, the frame rates of the liquid crystal panels 22G and 22B are four times the frame rate of the video signal.

[0093] The control device 30 controls the drive timings of the liquid crystal panels 22G and 22B so that the rotation efficiency Eg of the liquid crystal panel 22G reaches a maximum value Egm and the rotation efficiency Eb of the liquid crystal panel 22B reaches a maximum value Ebm during the periods when the pixel PXg included in the green image light LG and the pixel PXb included in the blue image light LB are located at the first position P1, the second position P2, the third position P3, and the fourth position P4. The drive timings of the liquid crystal panels 22G and 22B in the second embodiment are the same as those in the first embodiment, and therefore will not be described here.

[0094] On the other hand, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during the period when the pixel PXr included in the red image light LR is located at the first position P1 and the third position P3.

[0095] During a seventh period from time t0 to time t4, the control device 30 applies a voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R. Specifically, during the first half of the seventh period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R. During the second half of the seventh period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22R.

[0096] During an eighth period from time t4 to time t8, the control device 30 applies a voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R. Specifically, during the first half of the eighth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R. During the second half of the eighth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22R.

[0097] As described above, the control device 30 controls the drive timing of the liquid crystal panel 22R, so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during the period when the pixel PXr contained in the red image light LR is located at the first position P1 and the third position P3.

[0098] 9, in the second embodiment, the increasing and decreasing regions of the rotation efficiency Er of the liquid crystal panel 22R overlap during a period when the pixel PXr included in the red image light LR moves to the next position, such as the period from time t4 to time t5. Therefore, as in the first embodiment, although the red image is not turned off during this period, it is considered that significant color breakup from red to cyan does not occur.

[0099] As described above, in the projector of the second embodiment, the optical shift device 50B includes a first two-axis shift device 24G that shifts the optical path of the green image light LG along two axes and a single-axis shift device 26 that shifts the optical path of the red image light LR along one axis, and the frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector of the second embodiment, and the frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. According to the second embodiment, when the optical shift device 50B includes a first two-axis shift device 24G that shifts the optical path of the green image light LG along two axes and a single-axis shift device 26 that shifts the optical path of the red image light LR along one axis, it is possible to suppress deterioration in color tone and brightness due to a decrease in the rotation efficiency, particularly in the red wavelength band.

[0100] The projector of the second embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate combined image light LC, the optical shift device 50B further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, and the frame rate of the liquid crystal panel 22B is twice that of the liquid crystal panel 22R. According to the second embodiment, when the projector further includes a liquid crystal panel 22B and the optical shift device 50B further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0101] 10, in the second embodiment, the control device 30 may control the third rotation angle θ3 and the drive timing of the liquid crystal panel 22R so that the center time of the period in which the pixel PXr is held at the first position P1 coincides with the center time of the period in which the pixels PXg and PXb are held at the first position P1. The control device 30 may also control the third rotation angle θ3 and the drive timing of the liquid crystal panel 22R so that the center time of the period in which the pixel PXr is held at the third position P3 coincides with the center time of the period in which the pixels PXg and PXb are held at the third position P3.

[0102] [Third embodiment] Next, a third embodiment of the present disclosure will be described. The projector of the third embodiment differs from the projector 1 of the first embodiment in that it includes an optical shift device 50C that is different from the optical shift device 50A described in the first embodiment. Therefore, hereinafter, the third embodiment will be described while focusing on the optical shift device 50C, which is a difference from the first embodiment.

[0103] Fig. 11 is a diagram showing the configuration of an optical shift device 50C in the third embodiment. As shown in Fig. 11, the optical shift device 50C includes a two-axis shift device 24, a one-axis shift device 27, a first dummy glass 28G, and a second dummy glass 28B.

[0104] The uniaxial shift device 27 is disposed between the liquid crystal panel 22R and the dichroic prism 23. The uniaxial shift device 27 shifts the optical path of the red image light LR emitted from the liquid crystal panel 22R along one axis.

[0105] The uniaxial shift device 27 has a glass plate 27a, which is a translucent optical member that transmits the red image light LR. The uniaxial shift device 27 changes the orientation of the glass plate 27a to shift the optical path of the red image light LR by utilizing refraction of light. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic prism 23 via the uniaxial shift device 27.

[0106] The first dummy glass 28G is disposed between the liquid crystal panel 22G and the dichroic prism 23. The green image light LG emitted from the liquid crystal panel 22G is incident on the dichroic prism 23 via the first dummy glass 28G.

[0107] The second dummy glass 28B is disposed between the liquid crystal panel 22B and the dichroic prism 23. The blue image light LB emitted from the liquid crystal panel 22B enters the dichroic prism 23 via the second dummy glass 28B.

[0108] The dichroic prism 23 combines the red image light LR incident through the uniaxial shift device 27, the green image light LG incident through the first dummy glass 28G, and the blue image light LB incident through the second dummy glass 28B to generate combined image light LC.

[0109] The two-axis shift device 24 is disposed between the dichroic prism 23 and the projection optical system 25. The two-axis shift device 24 shifts, along two axes, the optical path of the composite image light LC emitted from the dichroic prism 23. The configuration of the two-axis shift device 24 is the same as that of the first embodiment, and therefore description thereof will be omitted.

[0110] Fig. 12 is a diagram showing the glass plate 27a of the uniaxial shift device 27 as seen from the liquid crystal panel 22R. As shown in Fig. 12, the red image light LR emitted from the liquid crystal panel 22R passes through the glass plate 27a. In the uniaxial shift device 27, the glass plate 27a is disposed so as to be rotatable around a fourth axis J4. The fourth axis J4 is perpendicular to the central axis C3 of the red image light LR and is tilted at 45 degrees clockwise with respect to the X-axis.

[0111] As shown in FIG. 12, the single-axis shift device 27 has a fourth actuator 27b that rotates the glass plate 27a around a fourth axis J4. The operation of the fourth actuator 27b is controlled by the control device 30. In the following description, the rotation angle around the fourth axis J4 is referred to as a fourth rotation angle θ4. FIG. 12 shows the state of the glass plate 27a when the fourth rotation angle θ4 is 0 degrees. When the fourth rotation angle θ4 is 0 degrees, the glass plate 27a is parallel to the XY plane and perpendicular to the central axis C3 of the red image light LR.

[0112] In the following description, the state of the glass plate 27a when the fourth rotation angle θ4 is 0 degrees is referred to as the reference state. When the glass plate 27a in this reference state rotates around the fourth axis J4 in the direction indicated by arrow D4, the fourth rotation angle θ4 becomes a positive value. On the other hand, when the glass plate 27a in the reference state rotates around the fourth axis J4 in the direction opposite to the direction indicated by arrow D4, the fourth rotation angle θ4 becomes a negative value.

[0113] 13 is a diagram showing how the position on the XY plane of pixel PXr included in red image light LR changes in response to the rotation of glass plate 27a. When glass plate 27a is in the reference state, that is, when the fourth rotation angle θ4 is 0 degrees, the position of pixel PXr is defined as the reference position P0 of pixel PXr. Note that, as an example, the position of pixel PXr is the position of the center point of pixel PXr.

[0114] When the fourth rotation angle θ4 is a positive seventh angle d1, the position of pixel PXr is a second position P2, which is shifted half a pixel to the upper right from the reference position P0. When the fourth rotation angle θ4 is a negative eighth angle d2, the position of pixel PXr is a fourth position P4, which is shifted half a pixel to the lower left from the reference position P0.

[0115] Figure 14 is a timing chart showing the temporal correspondence between the positions of pixels PXr, PXg, and PXb contained in the composite image light LC, the first rotation angle θ1, the second rotation angle θ2, the fourth rotation angle θ4, the drive timing of liquid crystal panels 22R, 22G, and 22B, and the rotation efficiency of liquid crystal panels 22R, 22G, and 22B.

[0116] In Figure 14, "position (R)" indicates the position of pixel PXr included in the composite image light LC. "position (GB)" indicates the positions of pixels PXg and PXb included in the composite image light LC. "Drive timing (R)" indicates the drive timing of liquid crystal panel 22R. "Drive timing (GB)" indicates the drive timing of liquid crystal panels 22G and 22B. "Er" indicates the rotation efficiency of liquid crystal panel 22R. "Eg" indicates the rotation efficiency of liquid crystal panel 22G. "Eb" indicates the rotation efficiency of liquid crystal panel 22B.

[0117] During the period from time t0 to time t1, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to change the first rotation angle θ1 of the glass plate 24a from 0 degrees to a positive first angle a1. Also, during the period from time t0 to time t1, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to change the second rotation angle θ2 of the glass plate 24a from a negative fourth angle b2 to 0 degrees. Also, during the period from time t0 to time t1, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to change the fourth rotation angle θ4 of the glass plate 27a from a positive seventh angle d1 to 0 degrees.

[0118] When the first rotation angle θ1 reaches the positive first angle a1 at time t1, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to maintain the first rotation angle θ1 at the positive first angle a1 from time t1 to time t2. When the second rotation angle θ2 reaches 0 degrees at time t1, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to maintain the second rotation angle θ2 at 0 degrees from time t1 to time t2. When the fourth rotation angle θ4 reaches 0 degrees at time t1, the control device 30 controls the fourth actuator 27b of the one-axis shift device 27 to maintain the fourth rotation angle θ4 at 0 degrees from time t1 to time t2. As a result, the positions of the pixels PXr, PXg, and PXb included in the composite image light LC emitted from the two-axis shift device 24 are maintained at the first position P1 from time t1 to time t2.

[0119] During the period from time t2 to time t3, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to change the first rotation angle θ1 of the glass plate 24a from the positive first angle a1 to 0 degrees. Also, during the period from time t2 to time t3, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to change the second rotation angle θ2 of the glass plate 24a from 0 degrees to the positive third angle b1. Also, during the period from time t2 to time t3, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to change the fourth rotation angle θ4 of the glass plate 27a from 0 degrees to the negative eighth angle d2.

[0120] When the first rotation angle θ1 reaches 0 degrees at time t3, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to maintain the first rotation angle θ1 at 0 degrees from time t3 to time t4. When the second rotation angle θ2 reaches the positive third angle b1 at time t3, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to maintain the second rotation angle θ2 at the positive third angle b1 from time t3 to time t4. When the fourth rotation angle θ4 reaches the negative eighth angle d2 at time t3, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to maintain the fourth rotation angle θ4 at the negative eighth angle d2 from time t3 to time t4. As a result, during the period from time t3 to time t4, the positions of the pixels PXg and PXb included in the composite image light LC output from the two-axis shift device 24 are maintained at the second position P2. On the other hand, during the period from time t3 to time t4, the position of the pixel PXr included in the composite image light LC output from the two-axis shift device 24 is set to the reference position P0 because the shift to the second position P2 is canceled by the one-axis shift device 27.

[0121] During the period from time t4 to time t5, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to change the first rotation angle θ1 of the glass plate 24a from 0 degrees to the negative second angle a2. Also, during the period from time t4 to time t5, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to change the second rotation angle θ2 of the glass plate 24a from the positive third angle b1 to 0 degrees. Also, during the period from time t4 to time t5, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to change the fourth rotation angle θ4 of the glass plate 27a from the negative eighth angle d2 to 0 degrees.

[0122] When the first rotation angle θ1 reaches the negative second angle a2 at time t5, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to maintain the first rotation angle θ1 at the negative second angle a2 from time t5 to time t6. When the second rotation angle θ2 reaches 0 degrees at time t5, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to maintain the second rotation angle θ2 at 0 degrees from time t5 to time t6. When the fourth rotation angle θ4 reaches 0 degrees at time t5, the control device 30 controls the fourth actuator 27b of the one-axis shift device 27 to maintain the fourth rotation angle θ4 at 0 degrees from time t5 to time t6. As a result, the positions of the pixels PXr, PXg, and PXb included in the composite image light LC emitted from the two-axis shift device 24 are maintained at the third position P3 from time t5 to time t6.

[0123] During the period from time t6 to time t7, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to change the first rotation angle θ1 of the glass plate 24a from the negative second angle a2 to 0 degrees. Also, during the period from time t6 to time t7, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to change the second rotation angle θ2 of the glass plate 24a from 0 degrees to the negative fourth angle b2. Also, during the period from time t6 to time t7, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to change the fourth rotation angle θ4 of the glass plate 27a from 0 degrees to the positive seventh angle d1.

[0124] When the first rotation angle θ1 reaches 0 degrees at time t7, the control device 30 controls the first actuator 24b of the two-axis shift device 24 to maintain the first rotation angle θ1 at 0 degrees from time t7 to time t8. When the second rotation angle θ2 reaches the negative fourth angle b2 at time t7, the control device 30 controls the second actuator 24c of the two-axis shift device 24 to maintain the second rotation angle θ2 at the negative fourth angle b2 from time t7 to time t8. When the fourth rotation angle θ4 reaches the positive seventh angle d1 at time t7, the control device 30 controls the fourth actuator 27b of the single-axis shift device 27 to maintain the fourth rotation angle θ4 at the positive seventh angle d1 from time t7 to time t8. As a result, during the period from time t7 to time t8, the positions of the pixels PXg and PXb included in the composite image light LC output from the two-axis shift device 24 are maintained at the fourth position P4. On the other hand, during the period from time t7 to time t8, the position of the pixel PXr included in the composite image light LC output from the two-axis shift device 24 is set to the reference position P0 because the shift to the fourth position P4 is canceled by the one-axis shift device 27.

[0125] After time t8, the control device 30 repeats the operations performed during the period from time t0 to time t8. For example, during the period from time t8 to time t9, the control device 30 changes the first rotation angle θ1 of the glass plate 24a of the two-axis shift device 24 from 0 degrees to a positive first angle a1. During the period from time t8 to time t9, the control device 30 changes the second rotation angle θ2 of the glass plate 24a of the two-axis shift device 24 from a negative fourth angle b2 to 0 degrees. During the period from time t8 to time t9, the control device 30 changes the fourth rotation angle θ4 of the glass plate 27a of the single-axis shift device 27 from a positive seventh angle d1 to 0 degrees.

[0126] In Fig. 14, the period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector of the third embodiment. The frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector of the third embodiment. The frame rates of the liquid crystal panels 22G and 22B are twice the frame rate of the liquid crystal panel 22R. In other words, the frame rates of the liquid crystal panels 22G and 22B are four times the frame rate of the video signal.

[0127] The control device 30 controls the drive timing of the liquid crystal panels 22G and 22B so that the rotation efficiency Eg of the liquid crystal panel 22G reaches the maximum value Egm and the rotation efficiency Eb of the liquid crystal panel 22B reaches the maximum value Ebm during the periods when the pixels PXg and PXb included in the composite image light LC are located at the first position P1, the second position P2, the third position P3, and the fourth position P4. The drive timing of the liquid crystal panels 22G and 22B in the third embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0128] Meanwhile, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during the period when the pixel PXr included in the composite image light LC is located at the first position P1 and the third position P3. The drive timing of the liquid crystal panel 22R in the third embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0129] 14, during the period when pixel PXr included in the composite image light LC is located at reference position P0, the increasing region and the decreasing region of rotation efficiency Er of liquid crystal panel 22R overlap. Therefore, during the period when pixel PXr included in the composite image light LC is located at reference position P0, the red image does not go out, but it is thought that no significant color breakup from red to cyan occurs.

[0130] As described above, in the projector of the third embodiment, the optical shift device 50C includes a two-axis shift device 24 that shifts the optical path of the composite image light LC along two axes and a one-axis shift device 27 that shifts the optical path of the red image light LR along one axis, and the frame rate of the liquid crystal panel 22R is twice the frame rate of the video signal supplied to the projector of the third embodiment, and the frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. According to the third embodiment, when the optical shift device 50C includes a two-axis shift device 24 that shifts the optical path of the composite image light LC along two axes and a one-axis shift device 27 that shifts the optical path of the red image light LR along one axis, it is possible to suppress deterioration in color tone and brightness due to a decrease in the rotation efficiency, particularly in the red wavelength band.

[0131] The projector of the third embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, and a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate combined image light LC, and the frame rate of the liquid crystal panel 22B is twice the frame rate of the liquid crystal panel 22R. According to the third embodiment, when the projector further includes the liquid crystal panel 22B, it is possible to realize high-definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0132] [Fourth embodiment] Next, a fourth embodiment of the present disclosure will be described. The projector of the fourth embodiment differs from the projector 1 of the first embodiment in that it includes an optical shift device 50D that is different from the optical shift device 50A described in the first embodiment. Therefore, the fourth embodiment will be described below while focusing on the optical shift device 50D, which is a difference from the first embodiment.

[0133] Fig. 15 is a diagram showing the configuration of an optical shift device 50D in the fourth embodiment. As shown in Fig. 15, the optical shift device 50D includes a first uniaxial shift device 26G, a second uniaxial shift device 26B, and a third dummy glass 28R.

[0134] The third dummy glass 28R is disposed between the liquid crystal panel 22R and the dichroic prism 23. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic prism 23 via the third dummy glass 28R.

[0135] The first uniaxial shift device 26G is disposed between the liquid crystal panel 22G and the dichroic prism 23. The first uniaxial shift device 26G shifts the optical path of the green image light LG emitted from the liquid crystal panel 22G along one axis.

[0136] The first uniaxial shift device 26G has a glass plate 26a, which is a translucent optical member that transmits the green image light LG. The first uniaxial shift device 26G shifts the optical path of the green image light LG by changing the orientation of the glass plate 26a and utilizing refraction of light. The green image light LG emitted from the liquid crystal panel 22G is incident on the dichroic prism 23 via the first uniaxial shift device 26G. The configuration of the first uniaxial shift device 26G is the same as that of the uniaxial shift device 26 described in the second embodiment, and therefore a description thereof will be omitted.

[0137] The second uniaxial shift device 26B is disposed between the liquid crystal panel 22B and the dichroic prism 23. The second uniaxial shift device 26B shifts, along one axis, the optical path of the blue image light LB emitted from the liquid crystal panel 22B.

[0138] The second uniaxial shift device 26B has a glass plate 26a, which is a translucent optical member that transmits the blue image light LB. The second uniaxial shift device 26B shifts the optical path of the blue image light LB by changing the orientation of the glass plate 26a and utilizing refraction of light. The blue image light LB emitted from the liquid crystal panel 22B is incident on the dichroic prism 23 via the second uniaxial shift device 26B. The configuration of the second uniaxial shift device 26B is the same as that of the uniaxial shift device 26 described in the second embodiment, and therefore a description thereof will be omitted.

[0139] The dichroic prism 23 combines the red image light LR incident through the third dummy glass 28R, the green image light LG incident through the first uniaxial shift device 26G, and the blue image light LB incident through the second uniaxial shift device 26B to generate combined image light LC.

[0140] Figure 16 is a timing chart showing the temporal correspondence between the positions of pixels PXr, PXg, and PXb contained in the composite image light LC, the third rotation angle θ3, the drive timing of liquid crystal panels 22R, 22G, and 22B, and the rotation efficiency of liquid crystal panels 22R, 22G, and 22B.

[0141] In Figure 16, "position (R)" indicates the position of pixel PXr included in the composite image light LC. "position (GB)" indicates the positions of pixels PXg and PXb included in the composite image light LC. "Drive timing (R)" indicates the drive timing of liquid crystal panel 22R. "Drive timing (GB)" indicates the drive timing of liquid crystal panels 22G and 22B. "Er" indicates the rotation efficiency of liquid crystal panel 22R. "Eg" indicates the rotation efficiency of liquid crystal panel 22G. "Eb" indicates the rotation efficiency of liquid crystal panel 22B.

[0142] During the period from time t0 to time t1, the control device 30 controls the third actuators 26b of the first single-axis shift device 26G and the second single-axis shift device 26B to change the third rotation angle θ3 of the glass plates 26a of the first single-axis shift device 26G and the second single-axis shift device 26B from the negative sixth angle c2 to the positive fifth angle c1. As a result, during the period from time t0 to time t1, the pixels PXg and PXb included in the composite image light LC shift from the third position P3 toward the first position P1.

[0143] When the third rotation angle θ3 reaches the positive fifth angle c1 at time t1, the control device 30 controls the third actuators 26b of the first single-axis shift device 26G and the second single-axis shift device 26B to maintain the third rotation angle θ3 of the glass plates 26a of the first single-axis shift device 26G and the second single-axis shift device 26B at the positive fifth angle c1 during the period from time t1 to time t4. As a result, the positions of the pixels PXg and PXb included in the composite image light LC are maintained at the first position P1 during the period from time t1 to time t4.

[0144] During the period from time t4 to time t5, the control device 30 controls the third actuators 26b of the first single-axis shift device 26G and the second single-axis shift device 26B to change the third rotation angle θ3 of the glass plates 26a of the first single-axis shift device 26G and the second single-axis shift device 26B from the positive fifth angle c1 to the negative sixth angle c2. As a result, during the period from time t4 to time t5, the pixels PXg and PXb included in the composite image light LC shift from the first position P1 toward the third position P3.

[0145] When the third rotation angle θ3 reaches the negative sixth angle c2 at time t5, the control device 30 controls the third actuators 26b of the first single-axis shift device 26G and the second single-axis shift device 26B to maintain the third rotation angle θ3 of the glass plates 26a of the first single-axis shift device 26G and the second single-axis shift device 26B at the negative sixth angle c2 during the period from time t5 to time t8. As a result, the positions of the pixels PXg and PXb included in the composite image light LC are maintained at the third position P3 during the period from time t5 to time t8.

[0146] In this embodiment, the optical path of the red image light LR emitted from the liquid crystal panel 22R is not shifted, so that the position of the pixel PXr included in the composite image light LC is the reference position P0 during the entire frame period including the period from time t0 to time t8.

[0147] In Figure 16, the period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector of the fourth embodiment. The frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the fourth embodiment. The frame rates of the liquid crystal panels 22G and 22B are twice the frame rate of the liquid crystal panel 22R. In other words, the frame rates of the liquid crystal panels 22G and 22B are twice the frame rate of the video signal.

[0148] The control device 30 controls the drive timing of the liquid crystal panels 22G and 22B so that the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm and the rotation efficiency Eb of the liquid crystal panel 22B becomes the maximum value Ebm during the period when the pixels PXg and PXb included in the composite image light LC are located at the first position P1 and the third position P3.

[0149] During a ninth period from time t0 to time t4, the control device 30 applies a voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the ninth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the ninth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0150] During a tenth period from time t4 to time t8, the control device 30 applies a voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B. Specifically, during the first half of the tenth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B. During the second half of the tenth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layers of the liquid crystal panels 22G and 22B.

[0151] As described above, by the control device 30 controlling the drive timing of the liquid crystal panels 22G and 22B, during the period when the pixels PXg and PXb contained in the composite image light LC are located at the first position P1 and the third position P3, the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm, and the rotation efficiency Eb of the liquid crystal panel 22B becomes the maximum value Ebm.

[0152] Meanwhile, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R reaches the maximum value Erm during one frame period. For example, during one frame from time t0 to time t8, the control device 30 applies a voltage corresponding to an image to be displayed at the reference position P0 to the liquid crystal layer of the liquid crystal panel 22R. Specifically, during the first half of one frame, the control device 30 applies a positive voltage corresponding to the image to be displayed at the reference position P0 to the liquid crystal layer of the liquid crystal panel 22R. During the second half of one frame, the control device 30 applies a negative voltage corresponding to the image to be displayed at the reference position P0 to the liquid crystal layer of the liquid crystal panel 22R.

[0153] As described above, in the projector of the fourth embodiment, the optical shift device 50D includes a first uniaxial shift device 26G that shifts the optical path of the green image light LG along one axis, the frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the fourth embodiment, and the frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. According to the fourth embodiment, when the optical shift device 50D includes the first uniaxial shift device 26G that shifts the optical path of the green image light LG along one axis, it is possible to suppress deterioration of color tone and brightness caused by a decrease in the rotation efficiency of the red wavelength band in particular.

[0154] The projector of the fourth embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate combined image light LC, and the optical shift device 50D further includes a second uniaxial shift device 26B that shifts the optical path of the blue image light LB along one axis, and the frame rate of the liquid crystal panel 22B is twice that of the liquid crystal panel 22R. According to the fourth embodiment, when the projector further includes a liquid crystal panel 22B and the optical shift device 50D further includes a second single-axis shift device 26B that shifts the optical path of the blue image light LB along one axis, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0155] [Fifth embodiment] Next, a fifth embodiment of the present disclosure will be described. The projector of the fifth embodiment differs from the projector 1 of the first embodiment in that it includes an optical shift device 50E that is different from the optical shift device 50A described in the first embodiment. Therefore, the fifth embodiment will be described below while focusing on the optical shift device 50E, which is a difference from the first embodiment.

[0156] Fig. 17 is a diagram showing the configuration of an optical shift device 50E in the fifth embodiment. As shown in Fig. 17, the optical shift device 50E includes a first two-axis shift device 24G, a second two-axis shift device 24B, and a third dummy glass 28R.

[0157] The third dummy glass 28R is disposed between the liquid crystal panel 22R and the dichroic prism 23. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic prism 23 via the third dummy glass 28R.

[0158] The first two-axis shift device 24G is disposed between the liquid crystal panel 22G and the dichroic prism 23. The first two-axis shift device 24G shifts the optical path of the green image light LG emitted from the liquid crystal panel 22G along two axes.

[0159] The first two-axis shift device 24G has a glass plate 24a, which is a translucent optical member that transmits the green image light LG. The first two-axis shift device 24G shifts the optical path of the green image light LG by changing the orientation of the glass plate 24a and utilizing refraction of light. The green image light LG emitted from the liquid crystal panel 22G is incident on the dichroic prism 23 via the first two-axis shift device 24G. The configuration of the first two-axis shift device 24G is the same as that of the two-axis shift device 24 described in the first embodiment, so a description thereof will be omitted.

[0160] The second two-axis shift device 24B is disposed between the liquid crystal panel 22B and the dichroic prism 23. The second two-axis shift device 24B shifts the optical path of the blue image light LB emitted from the liquid crystal panel 22B along two axes.

[0161] The second two-axis shift device 24B has a glass plate 24a, which is a translucent optical member that transmits the blue image light LB. The second two-axis shift device 24B shifts the optical path of the blue image light LB by changing the orientation of the glass plate 24a and utilizing refraction of light. The blue image light LB emitted from the liquid crystal panel 22B is incident on the dichroic prism 23 via the second two-axis shift device 24B. The configuration of the second two-axis shift device 24B is the same as that of the two-axis shift device 24 described in the first embodiment, so a description thereof will be omitted.

[0162] The dichroic prism 23 combines the red image light LR incident through the third dummy glass 28R, the green image light LG incident through the first two-axis shift device 24G, and the blue image light LB incident through the second two-axis shift device 24B to generate combined image light LC.

[0163] Figure 18 is a timing chart showing the temporal correspondence between the positions of pixels PXr, PXg, and PXb contained in the composite image light LC, the first rotation angle θ1, the second rotation angle θ2, the drive timing of liquid crystal panels 22R, 22G, and 22B, and the rotation efficiency of liquid crystal panels 22R, 22G, and 22B.

[0164] In Figure 18, "position (R)" indicates the position of pixel PXr included in the composite image light LC. "position (GB)" indicates the positions of pixels PXg and PXb included in the composite image light LC. "Drive timing (R)" indicates the drive timing of liquid crystal panel 22R. "Drive timing (GB)" indicates the drive timing of liquid crystal panels 22G and 22B. "Er" indicates the rotation efficiency of liquid crystal panel 22R. "Eg" indicates the rotation efficiency of liquid crystal panel 22G. "Eb" indicates the rotation efficiency of liquid crystal panel 22B.

[0165] During the period from time t0 to time t1, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from 0 degrees to a positive first angle a1. Furthermore, during the period from time t0 to time t1, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from a negative fourth angle b2 to 0 degrees. As a result, during the period from time t0 to time t1, the pixels PXg and PXb included in the composite image light LC shift from the fourth position P4 toward the first position P1.

[0166] When the first rotation angle θ1 reaches the positive first angle a1 at time t1, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at the positive first angle a1 from time t1 to time t2. When the second rotation angle θ2 reaches 0 degrees at time t1, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at 0 degrees from time t1 to time t2. As a result, during the period from time t1 to time t2, the positions of the pixels PXg and PXb included in the combined image light LC are maintained at the first position P1.

[0167] During the period from time t2 to time t3, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from a positive first angle a1 to 0 degrees. Furthermore, during the period from time t2 to time t3, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from 0 degrees to a positive third angle b1. As a result, during the period from time t2 to time t3, the pixels PXg and PXb included in the composite image light LC shift from the first position P1 toward the second position P2.

[0168] When the first rotation angle θ1 reaches 0 degrees at time t3, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at 0 degrees from time t3 to time t4. When the second rotation angle θ2 reaches the positive third angle b1 at time t3, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at the positive third angle b1 from time t3 to time t4. As a result, during the period from time t3 to time t4, the positions of the pixels PXg and PXb included in the combined image light LC are maintained at the second position P2.

[0169] During the period from time t4 to time t5, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from 0 degrees to a negative second angle a2. Furthermore, during the period from time t4 to time t5, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from a positive third angle b1 to 0 degrees. As a result, during the period from time t4 to time t5, the pixels PXg and PXb included in the composite image light LC shift from the second position P2 toward the third position P3.

[0170] When the first rotation angle θ1 reaches the negative second angle a2 at time t5, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at the negative second angle a2 from time t5 to time t6. When the second rotation angle θ2 reaches 0 degrees at time t5, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at 0 degrees from time t5 to time t6. As a result, during the period from time t5 to time t6, the positions of the pixels PXg and PXb included in the combined image light LC are maintained at the third position P3.

[0171] During the period from time t6 to time t7, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from the negative second angle a2 to 0 degrees. Furthermore, during the period from time t6 to time t7, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B from 0 degrees to the negative fourth angle b2. As a result, during the period from time t6 to time t7, the pixels PXg and PXb included in the composite image light LC shift from the third position P3 toward the fourth position P4.

[0172] When the first rotation angle θ1 reaches 0 degrees at time t7, the control device 30 controls the first actuators 24b of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at 0 degrees from time t7 to time t8. When the second rotation angle θ2 reaches the negative fourth angle b2 at time t7, the control device 30 controls the second actuators 24c of the first two-axis shift device 24G and the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the first two-axis shift device 24G and the second two-axis shift device 24B at the negative fourth angle b2 from time t7 to time t8. As a result, during the period from time t7 to time t8, the positions of the pixels PXg and PXb included in the combined image light LC are maintained at the fourth position P4.

[0173] In this embodiment, the optical path of the red image light LR emitted from the liquid crystal panel 22R is not shifted, so that the position of the pixel PXr included in the composite image light LC is the reference position P0 during the entire frame period including the period from time t0 to time t8.

[0174] In Figure 18, the period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector of the fifth embodiment. The frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the fifth embodiment. The frame rate of the liquid crystal panels 22G and 22B is four times the frame rate of the liquid crystal panel 22R. In other words, the frame rate of the liquid crystal panels 22G and 22B is four times the frame rate of the video signal.

[0175] The control device 30 controls the drive timing of the liquid crystal panels 22G and 22B so that the rotation efficiency Eg of the liquid crystal panel 22G reaches the maximum value Egm and the rotation efficiency Eb of the liquid crystal panel 22B reaches the maximum value Ebm during the periods when the pixels PXg and PXb included in the composite image light LC are located at the first position P1, the second position P2, the third position P3, and the fourth position P4. The drive timing of the liquid crystal panels 22G and 22B in the fifth embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0176] Meanwhile, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during one frame period. The drive timing of the liquid crystal panel 22R in the fifth embodiment is the same as that in the fourth embodiment, and therefore a description thereof will be omitted.

[0177] As described above, in the projector of the fifth embodiment, the optical shift device 50E includes a first two-axis shift device 24G that shifts the optical path of the green image light LG along two axes, the frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the fifth embodiment, and the frame rate of the liquid crystal panel 22G is four times the frame rate of the liquid crystal panel 22R. According to the fifth embodiment, when the optical shift device 50E includes the first two-axis shift device 24G that shifts the optical path of the green image light LG along two axes, it is possible to suppress deterioration of color tone and brightness due to a decrease in the rotation efficiency, particularly in the red wavelength band.

[0178] The projector of the fifth embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate combined image light LC, the optical shift device 50E further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, and the frame rate of the liquid crystal panel 22B is four times that of the liquid crystal panel 22R. According to the fifth embodiment, when the projector further includes a liquid crystal panel 22B and the optical shift device 50E further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0179] [Sixth embodiment] Next, a sixth embodiment of the present disclosure will be described. The projector of the sixth embodiment differs from the projector 1 of the first embodiment in that it includes an optical shift device 50F that is different from the optical shift device 50A described in the first embodiment. Therefore, the sixth embodiment will be described below while focusing on the optical shift device 50F, which is a difference from the first embodiment.

[0180] Fig. 19 is a diagram showing the configuration of an optical shift device 50F in the sixth embodiment. As shown in Fig. 19, the optical shift device 50F includes a first one-axis shift device 26G, a second two-axis shift device 24B, and a third dummy glass 28R.

[0181] The third dummy glass 28R is disposed between the liquid crystal panel 22R and the dichroic prism 23. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic prism 23 via the third dummy glass 28R.

[0182] The first uniaxial shift device 26G is disposed between the liquid crystal panel 22G and the dichroic prism 23. The first uniaxial shift device 26G shifts the optical path of the green image light LG emitted from the liquid crystal panel 22G along one axis.

[0183] The first uniaxial shift device 26G has a glass plate 26a, which is a translucent optical member that transmits the green image light LG. The first uniaxial shift device 26G shifts the optical path of the green image light LG by changing the orientation of the glass plate 26a and utilizing refraction of light. The green image light LG emitted from the liquid crystal panel 22G is incident on the dichroic prism 23 via the first uniaxial shift device 26G. The configuration of the first uniaxial shift device 26G is the same as that of the uniaxial shift device 26 described in the second embodiment, and therefore a description thereof will be omitted.

[0184] The second two-axis shift device 24B is disposed between the liquid crystal panel 22B and the dichroic prism 23. The second two-axis shift device 24B shifts the optical path of the blue image light LB emitted from the liquid crystal panel 22B along two axes.

[0185] The second two-axis shift device 24B has a glass plate 24a, which is a translucent optical member that transmits the blue image light LB. The second two-axis shift device 24B shifts the optical path of the blue image light LB by changing the orientation of the glass plate 24a and utilizing refraction of light. The blue image light LB emitted from the liquid crystal panel 22B is incident on the dichroic prism 23 via the second two-axis shift device 24B. The configuration of the second two-axis shift device 24B is the same as that of the two-axis shift device 24 described in the first embodiment, so a description thereof will be omitted.

[0186] The dichroic prism 23 combines the red image light LR incident through the third dummy glass 28R, the green image light LG incident through the first uniaxial shift device 26G, and the blue image light LB incident through the second biaxial shift device 24B to generate combined image light LC.

[0187] Figure 20 is a timing chart showing the temporal correspondence between the positions of pixels PXr, PXg, and PXb contained in the composite image light LC, the first rotation angle θ1, the second rotation angle θ2, the third rotation angle θ3, the drive timing of liquid crystal panels 22R, 22G, and 22B, and the rotation efficiency of liquid crystal panels 22R, 22G, and 22B.

[0188] In Figure 20, "position (R)" indicates the position of pixel PXr included in the composite image light LC. "position (G)" indicates the position of pixel PXg included in the composite image light LC. "position (B)" indicates the position of pixel PXb included in the composite image light LC. "Drive timing (R)" indicates the drive timing of liquid crystal panel 22R. "Drive timing (G)" indicates the drive timing of liquid crystal panel 22G. "Drive timing (B)" indicates the drive timing of liquid crystal panel 22B. "Er" indicates the rotation efficiency of liquid crystal panel 22R. "Eg" indicates the rotation efficiency of liquid crystal panel 22G. "Eb" indicates the rotation efficiency of liquid crystal panel 22B.

[0189] During the period from time t0 to time t1, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B from 0 degrees to a positive first angle a1. Also, during the period from time t0 to time t1, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B from a negative fourth angle b2 to 0 degrees. As a result, during the period from time t0 to time t1, the pixel PXb included in the composite image light LC shifts from the fourth position P4 toward the first position P1.

[0190] When the first rotation angle θ1 reaches the positive first angle a1 at time t1, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B at the positive first angle a1 from time t1 to time t2. When the second rotation angle θ2 reaches 0 degrees at time t1, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B at 0 degrees from time t1 to time t2. As a result, the position of the pixel PXb included in the composite image light LC is maintained at the first position P1 from time t1 to time t2.

[0191] During the period from time t2 to time t3, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B from the positive first angle a1 to 0 degrees. Furthermore, during the period from time t2 to time t3, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B from 0 degrees to the positive third angle b1. As a result, during the period from time t2 to time t3, the pixel PXb included in the composite image light LC shifts from the first position P1 toward the second position P2.

[0192] When the first rotation angle θ1 reaches 0 degrees at time t3, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B at 0 degrees from time t3 to time t4. When the second rotation angle θ2 reaches the positive third angle b1 at time t3, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B at the positive third angle b1 from time t3 to time t4. As a result, the position of pixel PXb included in the composite image light LC is maintained at the second position P2 from time t3 to time t4.

[0193] During the period from time t4 to time t5, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B from 0 degrees to a negative second angle a2. Furthermore, during the period from time t4 to time t5, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B from a positive third angle b1 to 0 degrees. As a result, during the period from time t4 to time t5, the pixel PXb included in the composite image light LC shifts from the second position P2 toward the third position P3.

[0194] When the first rotation angle θ1 reaches the negative second angle a2 at time t5, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B at the negative second angle a2 from time t5 to time t6. Furthermore, when the second rotation angle θ2 reaches 0 degrees at time t5, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B at 0 degrees from time t5 to time t6. As a result, the position of the pixel PXb included in the composite image light LC is maintained at the third position P3 from time t5 to time t6.

[0195] During the period from time t6 to time t7, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to change the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B from the negative second angle a2 to 0 degrees. Furthermore, during the period from time t6 to time t7, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to change the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B from 0 degrees to the negative fourth angle b2. As a result, during the period from time t6 to time t7, the pixel PXb included in the composite image light LC shifts from the third position P3 toward the fourth position P4.

[0196] When the first rotation angle θ1 reaches 0 degrees at time t7, the control device 30 controls the first actuator 24b of the second two-axis shift device 24B to maintain the first rotation angle θ1 of the glass plate 24a of the second two-axis shift device 24B at 0 degrees from time t7 to time t8. When the second rotation angle θ2 reaches the negative fourth angle b2 at time t7, the control device 30 controls the second actuator 24c of the second two-axis shift device 24B to maintain the second rotation angle θ2 of the glass plate 24a of the second two-axis shift device 24B at the negative fourth angle b2 from time t7 to time t8. As a result, the position of the pixel PXb included in the composite image light LC is maintained at the fourth position P4 from time t7 to time t8.

[0197] The control device 30 controls the third rotation angle θ3 of the glass plate 26a of the first uniaxial shift device 26G so that the center time of the period during which pixel PXb included in the composite image light LC is held at the first position P1 coincides with the center time of the period during which pixel PXg included in the composite image light LC is held at the first position P1. The control device 30 also controls the third rotation angle θ3 of the glass plate 26a of the first uniaxial shift device 26G so that the center time of the period during which pixel PXb included in the composite image light LC is held at the third position P3 coincides with the center time of the period during which pixel PXg included in the composite image light LC is held at the third position P3.

[0198] In this embodiment, the optical path of the red image light LR emitted from the liquid crystal panel 22R is not shifted, so that the position of the pixel PXr included in the composite image light LC is the reference position P0 during the entire frame period including the period from time t0 to time t8.

[0199] In FIG. 20, the period from time t0 to time t8 corresponds to one frame of the video signal supplied to the projector of the sixth embodiment. The frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the sixth embodiment. The frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. In other words, the frame rate of the liquid crystal panel 22G is twice the frame rate of the video signal. The frame rate of the liquid crystal panel 22B is four times the frame rate of the liquid crystal panel 22R. In other words, the frame rate of the liquid crystal panel 22B is four times the frame rate of the video signal.

[0200] The control device 30 controls the drive timing of the liquid crystal panel 22B so that the rotation efficiency Eb of the liquid crystal panel 22B becomes the maximum value Ebm during the periods when the pixel PXb included in the composite image light LC is located at the first position P1, the second position P2, the third position P3, and the fourth position P4. The drive timing of the liquid crystal panel 22B in the sixth embodiment is the same as that in the first embodiment, and therefore description thereof will be omitted.

[0201] The control device 30 controls the drive timing of the liquid crystal panel 22G so that the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm during the period when the pixel PXg included in the composite image light LC is located at the first position P1 and the third position P3.

[0202] During an eleventh period from the center time (not shown) of the fourth period of the previous frame to the center time of the second period of the current frame, the control device 30 applies a voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22G. Specifically, during the first half of the eleventh period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22G. During the second half of the eleventh period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the first position P1 to the liquid crystal layer of the liquid crystal panel 22G.

[0203] During a twelfth period from the center of the second period to the center of the fourth period, the control device 30 applies a voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22G. Specifically, during the first half of the twelfth period, the control device 30 applies a positive voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22G. During the second half of the twelfth period, the control device 30 applies a negative voltage corresponding to the image to be displayed at the third position P3 to the liquid crystal layer of the liquid crystal panel 22G.

[0204] As described above, by the control device 30 controlling the drive timing of the liquid crystal panel 22G, the rotation efficiency Eg of the liquid crystal panel 22G becomes the maximum value Egm during the period when the pixel PXg included in the composite image light LC is located at the first position P1 and the third position P3.

[0205] Meanwhile, the control device 30 controls the drive timing of the liquid crystal panel 22R so that the rotation efficiency Er of the liquid crystal panel 22R becomes the maximum value Erm during one frame period. The drive timing of the liquid crystal panel 22R in the sixth embodiment is the same as that in the fourth embodiment, and therefore description thereof will be omitted.

[0206] As described above, in the projector of the sixth embodiment, the optical shift device 50F includes a first uniaxial shift device 26G that shifts the optical path of the green image light LG along one axis, and the frame rate of the liquid crystal panel 22R is the same as the frame rate of the video signal supplied to the projector of the sixth embodiment, and the frame rate of the liquid crystal panel 22G is twice the frame rate of the liquid crystal panel 22R. According to the fifth embodiment, when the optical shift device 50F includes the first uniaxial shift device 26G that shifts the optical path of the green image light LG along one axis, it is possible to suppress deterioration of color tone and brightness caused by a decrease in rotation efficiency, particularly in the red wavelength band.

[0207] The projector of the sixth embodiment further includes a liquid crystal panel 22B that modulates the blue fourth color light L4 to generate blue image light LB, a dichroic prism 23 that combines the red image light LR, the green image light LG, and the blue image light LB to generate a combined image light LC, the optical shift device 50F further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, and the frame rate of the liquid crystal panel 22B is four times that of the liquid crystal panel 22R. According to the sixth embodiment, when the projector further includes a liquid crystal panel 22B and the optical shift device 50F further includes a second two-axis shift device 24B that shifts the optical path of the blue image light LB along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0208] The above describes embodiments of the present disclosure, but the technical scope of the present disclosure is not limited to the above embodiments, and various modifications can be made within the scope that does not deviate from the spirit of the present disclosure.

[0209] Fig. 21 is a diagram showing a modified example of the second embodiment. As shown in Fig. 21, two dichroic mirrors 41 and 42 may be used instead of the dichroic prism 23, and one two-axis shift device 24 may be used instead of the first two-axis shift device 24G and the second two-axis shift device 24B.

[0210] The dichroic mirror 41 combines the green image light LG emitted from the liquid crystal panel 22G and the blue image light LB emitted from the liquid crystal panel 22B to generate fifth color light LGB. The fifth color light LGB emitted from the dichroic mirror 41 is incident on the dichroic mirror 42 via the two-axis shift device 24. The red image light LR emitted from the liquid crystal panel 22R is incident on the dichroic mirror 42 via the one-axis shift device 26. The dichroic mirror 41 combines the red image light LR incident from the one-axis shift device 26 and the fifth color light LGB incident from the dichroic mirror 41 to generate combined image light LC.

[0211] Summary of the Disclosure A summary of this disclosure is provided below.

[0212] (Supplementary Note 1) A projector comprising: a first liquid crystal panel that modulates light in a first wavelength band to generate first image light; a second liquid crystal panel that modulates light in a second wavelength band having a center wavelength longer than the center wavelength of the first wavelength band to generate second image light; a light combining element that combines the first image light and the second image light to generate combined image light; a projection optical system that projects the combined image light; and an optical shift device that shifts an optical path of at least one of the first image light, the second image light, and the combined image light, wherein a thickness of a liquid crystal layer of the second liquid crystal panel is greater than a thickness of a liquid crystal layer of the first liquid crystal panel, and a frame rate of the first liquid crystal panel is greater than a frame rate of the second liquid crystal panel.

[0213] According to the projector described in Supplementary Note 1, by adopting a configuration in which the liquid crystal layer of the second liquid crystal panel is thicker than the liquid crystal layer of the first liquid crystal panel, it is possible to suppress a decrease in the rotation efficiency of the second liquid crystal panel, which generates second image light by modulating light in a second wavelength band having a center wavelength longer than that of the first wavelength band. Meanwhile, because the liquid crystal layer of the second liquid crystal panel is thicker than that of the first liquid crystal panel, the response speed of the second liquid crystal panel is slower than that of the first liquid crystal panel. In contrast, according to the projector described in Supplementary Note 1, a configuration is adopted in which the frame rate of the first liquid crystal panel is faster than that of the second liquid crystal panel. In other words, because the frame rate of the second liquid crystal panel is slower than that of the first liquid crystal panel, a slow response speed of the second liquid crystal panel does not pose a problem. As described above, according to the projector described in Supplementary Note 1, when a light path shift device is used, it is possible to suppress deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0214] (Appendix 2) The projector described in Appendix 1, wherein the optical shift device includes a two-axis shift device that shifts the optical path of the composite image light along two axes, the frame rate of the second liquid crystal panel is twice the frame rate of the video signal supplied to the projector, and the frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0215] According to the projector described in Appendix 2, when the optical shift device includes a two-axis shift device that shifts the optical path of the composite image light along two axes, it is possible to suppress deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0216] (Appendix 3) The projector described in Appendix 2 further includes a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, and the frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0217] According to the projector described in Appendix 3, when the projector further includes a third liquid crystal panel, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0218] (Appendix 4) The projector described in Appendix 1, wherein the optical shift device includes a first two-axis shift device that shifts the optical path of the first image light along two axes and a single-axis shift device that shifts the optical path of the second image light along one axis, and the frame rate of the second liquid crystal panel is twice the frame rate of a video signal supplied to the projector, and the frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0219] According to the projector described in Appendix 4, when the optical shift device includes a first two-axis shift device that shifts the optical path of the first image light along two axes and a single-axis shift device that shifts the optical path of the second image light along one axis, it is possible to suppress deterioration in color and brightness, particularly due to a decrease in rotation efficiency in the red wavelength band.

[0220] (Appendix 5) The projector described in Appendix 4 further includes a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes, and the frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0221] According to the projector described in Appendix 5, when the projector further includes a third liquid crystal panel and the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0222] (Appendix 6) The projector described in Appendix 1, wherein the optical shift device includes a two-axis shift device that shifts the optical path of the composite image light along two axes and a single-axis shift device that shifts the optical path of the second image light along one axis, and the frame rate of the second liquid crystal panel is twice the frame rate of the video signal supplied to the projector, and the frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0223] According to the projector described in Appendix 6, when the optical shift device includes a two-axis shift device that shifts the optical path of the composite image light along two axes and a single-axis shift device that shifts the optical path of the second image light along one axis, it is possible to suppress deterioration in color and brightness, particularly due to a decrease in rotation efficiency in the red wavelength band.

[0224] (Appendix 7) The projector described in Appendix 6 further includes a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, and the frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0225] According to the projector described in Appendix 7, when the projector further includes a third liquid crystal panel, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color tone and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0226] (Appendix 8) The projector described in Appendix 1, wherein the optical shift device includes a first single-axis shift device that shifts the optical path of the first image light along one axis, the frame rate of the second liquid crystal panel is the same as the frame rate of the video signal supplied to the projector, and the frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0227] According to the projector described in Appendix 8, when the optical shift device includes a first uniaxial shift device that shifts the optical path of the first image light along one axis, it is possible to suppress deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0228] (Appendix 9) The projector described in Appendix 8 further includes a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, the optical shift device further includes a second uniaxial shift device that shifts the optical path of the third image light along one axis, and the frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel.

[0229] According to the projector described in Appendix 9, when the projector further includes a third liquid crystal panel and the optical shift device further includes a second single-axis shift device that shifts the optical path of the third image light along one axis, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0230] (Appendix 10) The projector described in Appendix 8, further comprising a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, the optical shift device further includes a two-axis shift device that shifts the optical path of the third image light along two axes, and the frame rate of the third liquid crystal panel is four times the frame rate of the second liquid crystal panel.

[0231] According to the projector described in Appendix 10, when the projector further includes a third liquid crystal panel and the optical shift device further includes a two-axis shift device that shifts the optical path of the third image light along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0232] (Appendix 11) The projector described in Appendix 1, wherein the optical shift device includes a first two-axis shift device that shifts the optical path of the first image light along two axes, the frame rate of the second liquid crystal panel is the same as the frame rate of the video signal supplied to the projector, and the frame rate of the first liquid crystal panel is four times the frame rate of the second liquid crystal panel.

[0233] According to the projector described in Appendix 11, when the optical shift device includes a first two-axis shift device that shifts the optical path of the first image light along two axes, it is possible to suppress deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band.

[0234] (Appendix 12) The projector described in Appendix 11 further includes a third liquid crystal panel that modulates light of a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light, the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light, the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes, and the frame rate of the third liquid crystal panel is four times the frame rate of the second liquid crystal panel.

[0235] According to the projector described in Appendix 12, when the projector further includes a third liquid crystal panel and the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes, it is possible to achieve high definition images projected from the projector while suppressing deterioration in color and brightness due to a decrease in rotation efficiency, particularly in the red wavelength band. [Explanation of symbols]

[0236] 1...Projector, 10...Optical device, 11...Light source, 22R, 22G, 22B...Liquid crystal panel, 23...Dichroic prism, 25...Projection optical system, 30...Control device, 50A, 50B, 50C, 50D, 50E, 50F...Optical shift device, SC...Projection screen

Claims

1. a first liquid crystal panel that modulates light in a first wavelength band to generate first image light; a second liquid crystal panel that modulates light in a second wavelength band having a center wavelength longer than the center wavelength of the first wavelength band to generate second image light; a light combining element that combines the first image light and the second image light to generate combined image light; a projection optical system that projects the composite image light; an optical shifting device that shifts an optical path of at least one of the first image light, the second image light, and the combined image light; Equipped with the thickness of the liquid crystal layer of the second liquid crystal panel is greater than the thickness of the liquid crystal layer of the first liquid crystal panel; The frame rate of the first liquid crystal panel is higher than the frame rate of the second liquid crystal panel. projector.

2. the optical shift device includes a two-axis shift device that shifts the optical path of the composite image light along two axes; a frame rate of the second liquid crystal panel is twice the frame rate of the video signal supplied to the projector; The frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 1 .

3. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; The frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 2 .

4. The optical shift device is a first biaxial shifting device for shifting an optical path of the first image light along two axes; a single-axis shifting device for shifting the optical path of the second image light along one axis; Including, a frame rate of the second liquid crystal panel is twice the frame rate of the video signal supplied to the projector; The frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 1 .

5. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes; The frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 4 .

6. The optical shift device is a two-axis shifting device for shifting the optical path of the composite image light along two axes; a single-axis shifting device for shifting the optical path of the second image light along one axis; Including, a frame rate of the second liquid crystal panel is twice the frame rate of the video signal supplied to the projector; The frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 1 .

7. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; The frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 6 .

8. the optical shift device includes a first single-axis shift device that shifts an optical path of the first image light along one axis; a frame rate of the second liquid crystal panel is the same as a frame rate of a video signal supplied to the projector; The frame rate of the first liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 1 .

9. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; the optical shift device further includes a second single-axis shift device that shifts the optical path of the third image light along one axis; The frame rate of the third liquid crystal panel is twice the frame rate of the second liquid crystal panel. The projector according to claim 8 .

10. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; the optical shift device further includes a two-axis shift device that shifts the optical path of the third image light along two axes; The frame rate of the third liquid crystal panel is four times the frame rate of the second liquid crystal panel. The projector according to claim 8 .

11. the optical shift device includes a first biaxial shift device that shifts an optical path of the first image light along two axes; a frame rate of the second liquid crystal panel is the same as a frame rate of a video signal supplied to the projector; The frame rate of the first liquid crystal panel is four times the frame rate of the second liquid crystal panel. The projector according to claim 1 .

12. a third liquid crystal panel that modulates light in a third wavelength band having a center wavelength shorter than the center wavelength of the first wavelength band to generate third image light; the light combining element combines the first image light, the second image light, and the third image light to generate the combined image light; the optical shift device further includes a second two-axis shift device that shifts the optical path of the third image light along two axes; The frame rate of the third liquid crystal panel is four times the frame rate of the second liquid crystal panel. The projector according to claim 11.

Images