Stereoscopic image display device

Abstract

To provide a three-dimensional-image display device capable of suppressing crosstalk.SOLUTION: A three-dimensional-image display device 10 includes a display unit 20, a variable focus lens unit 40, and a control unit 80. The display unit 20 sequentially displays a first image displayed by a first image signal and a second image displayed by a second image signal, and projects display light L1 of the first image and display light L1 of the second image. The variable focus lens unit 40 switches each focal length for each display light L1 and forms, as virtual images, respectively, each of the first image and the second image on each of a first display surface 102 and a second display surface 104. The control unit 80 controls projecting timing at which the display unit 20 projects the display light L1 of the first image and the display light L1 of the second image on the basis of start timing at which writing of an image signal of a different image to pixels of the display unit 20 is started.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a stereoscopic image display device. [Background technology]

[0002] As a display device that displays a stereoscopic image (three-dimensional image) visible to the naked eye, a depth fused 3D (DFD) type stereoscopic image display device is known. For example, Patent Document 1 discloses a three-dimensional display device including a display device that alternately displays two two-dimensional images, a polarizing plate that outputs light emitted from the display device as polarized light, a polarization switching device that switches the polarization direction of the light emitted from the polarizing plate, and a polarized bifocal lens.

[0003] In the three-dimensional display device of Patent Document 1, two two-dimensional images are alternately formed on display surfaces that are located at different depth positions from the observer's perspective, and a stereoscopic image is displayed by independently changing the brightness or transmittance of the two two-dimensional images. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-129983 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the three-dimensional display device of Patent Document 1, two two-dimensional images are alternately displayed, so if crosstalk occurs between the two two-dimensional images, there is a risk that the stereoscopic image will not be displayed in the correct position.

[0006] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a stereoscopic image display device capable of suppressing crosstalk. [Means for solving the problem]

[0007] In order to achieve the above object, the stereoscopic image display device of the present disclosure comprises: a display unit that sequentially displays a first image based on a first image signal and a second image based on a second image signal, and emits display light for the first image and display light for the second image; a variable-focus lens unit that switches between a focal length for the display light of the first image and a focal length for the display light of the second image; a control unit that controls an emission timing at which the display unit emits display light for the first image and display light for the second image, the first image and the second image are two-dimensional images obtained by projecting a display object from a viewer's side onto a first display surface and a second display surface that are located at different positions in a depth direction as viewed from the viewer, respectively; the variable-focus lens unit forms the first image and the second image as virtual images on the first display surface and the second display surface, respectively; The control unit controls the emission timing based on a start timing at which writing of an image signal of a different image to a pixel of the display unit is started. death, The control unit sets the emission timing to a timing at which a time has elapsed from the start timing that ends latest among switching of a focal length of the variable-focus lens unit for the display light of the first image and a focal length of the variable-focus lens unit for the display light of the second image, a response of the pixels of the display unit to the first image signal, and a response of the pixels of the display unit to the second image signal. . Effect of the Invention

[0008] According to the present disclosure, crosstalk can be suppressed. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing a stereoscopic image display device according to a first embodiment. [Diagram 2] FIG. 1 is a plan view showing a liquid crystal display panel according to a first embodiment. [Diagram 3] 2 is a schematic diagram showing a light source unit according to the first embodiment. FIG. [Figure 4] 1 is a cross-sectional view showing a polarization switching section according to a first embodiment. [Diagram 5] FIG. 1 is a cross-sectional view showing a polarized bifocal lens according to a first embodiment. [Figure 6]FIG. 2 is a block diagram showing a control unit according to the first embodiment. [Figure 7] FIG. 2 is a diagram illustrating a hardware configuration of a control unit according to the first embodiment. [Figure 8] 5 is a diagram showing the operation timing of the stereoscopic image display device according to the first embodiment. FIG. [Figure 9] FIG. 11 is a cross-sectional view showing a polarization switching section according to a second embodiment. [Figure 10] FIG. 11 is a diagram showing the operation timing of the stereoscopic image display device according to the second embodiment. [Figure 11] FIG. 11 is a plan view showing a liquid crystal display panel according to a third embodiment. [Figure 12] FIG. 11 is a schematic diagram showing a light source unit according to a third embodiment. [Figure 13] FIG. 11 is a plan view showing a polarization switching section according to a third embodiment. [Figure 14] FIG. 11 is a diagram showing the operation timing of the stereoscopic image display device according to the third embodiment. [Figure 15] FIG. 11 is a schematic diagram showing a stereoscopic image display device according to a fourth embodiment. [Figure 16] FIG. 11 is a plan view showing a liquid crystal lens according to a fourth embodiment. [Figure 17] 17 is a cross-sectional view of the liquid crystal lens shown in FIG. 16 taken along line AA. [Figure 18] FIG. 13 is a block diagram showing a control unit according to the fourth embodiment. [Figure 19] FIG. 11 is a diagram showing the operation timing of the stereoscopic image display device according to the fourth embodiment. [Figure 20] FIG. 13 is a diagram showing the polarity of a write voltage to a pixel according to the fifth embodiment. [Figure 21] FIG. 11 is a schematic diagram showing a pixel circuit according to a fifth embodiment. [Figure 22] 11 is a diagram showing polarity inversion of voltages written to pixels according to embodiment 5. (a) to (d) show frame inversion driving, and (e) to (h) show pixel inversion driving. [Figure 23] FIG. 13 is a schematic diagram showing a stereoscopic image display device according to a modified example. [Figure 24]FIG. 13 is a schematic diagram showing a stereoscopic image display device according to a modified example. [Diagram 25] FIG. 13 is a diagram showing the polarity of a voltage applied to a pixel according to a modified example. [Figure 26] 13A and 13B are diagrams illustrating an example of rewriting a displayed image according to a modified example. [Figure 27] FIG. 13 is a diagram showing the polarity of a voltage applied to a pixel according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, a stereoscopic image display device according to an embodiment will be described with reference to the drawings.

[0011] <Embodiment 1> A stereoscopic image display device 10 according to this embodiment will be described with reference to Figs. 1 to 8. The stereoscopic image display device 10 is a display device that displays stereoscopic images by a DFD (Depth Fused 3D) method. The stereoscopic image display device 10 is combined with an eyepiece lens, for example, and used as a head-mounted display. Note that in this embodiment, the stereoscopic image display device 10 using a monochrome liquid crystal panel will be described as an example.

[0012] (Overall composition) First, there will be described the overall configuration of the stereoscopic image display device 10. The stereoscopic image display device 10 includes a display unit 20, a variable-focus lens unit 40, and a control unit 80, as shown in FIG.

[0013] The display unit 20 sequentially displays the first image and the second image in a time-division manner. In this embodiment, the display unit 20 emits the display light L1 of the first image and the second image as polarized light whose polarization direction is a predetermined first direction. The variable-focus lens unit 40 switches the focal length for the display light L1 of the first image and the focal length for the display light L1 of the second image, and forms the first image and the second image as virtual images on the first display surface 102 and the second display surface 104, respectively. In this embodiment, the variable-focus lens unit 40 has a polarization switching unit 50 and a polarized bifocal lens 60. The polarization switching unit 50 switches the polarization direction of the display light L1 emitted from the display unit 20 between a predetermined first direction and a predetermined second direction, and emits the light. The polarized bifocal lens 60 is a lens whose focal length for the emitted light emitted from the polarization switching unit 50 varies depending on the polarization direction of the emitted light. The control unit 80 controls the emission timing at which the display unit 20 emits the display light L1. The control unit 80 also supplies a first image signal for displaying a first image and a second image signal for displaying a second image to the display unit 20. The control unit 80 also controls the switching of the polarization direction of the polarization switching unit 50.

[0014] 1 (left direction on the paper) is the +Z direction, the upward direction (upward on the paper) is the +Y direction, and the direction perpendicular to the +Y and +Z directions (toward the viewer on the paper) is the +X direction for ease of understanding. In addition, the first image signal for displaying the first image and the second image signal for displaying the second image are collectively referred to as image signals.

[0015] The display unit 20 of the stereoscopic image display device 10 includes a liquid crystal display panel 22 and a light source section 32. The liquid crystal display panel 22 of the display unit 20 modulates light emitted from the light source section 32 based on a first image signal for displaying a first image and a second image signal for displaying a second image, which are supplied from the control section 80, to sequentially display the first image and the second image in a time-division manner. The liquid crystal display panel 22 emits display light L1 of an image (for example, the first image and the second image) as polarized light whose polarization direction is a predetermined first direction. The display light L1 emitted from the liquid crystal display panel 22 is incident on the polarization switching section 50. In this embodiment, the predetermined first direction is the X direction.

[0016] The first and second images are two-dimensional images of a display object projected from the observer side onto first display surface 102 and second display surface 104, which are located at different positions in the depth direction (+Z direction) as seen from the observer. First display surface 102 and second display surface 104 will be described later.

[0017] The liquid crystal display panel 22 is, for example, a transmissive TN (Twisted Nematic) liquid crystal panel that is active-matrix driven by TFTs (Thin Film Transistors). As shown in FIG. 2, the liquid crystal display panel 22 has pixels P arranged in a matrix, a gate driver 23G, and a data driver 23D. The gate driver 23G sequentially selects the pixels P row by row and performs line-sequential scanning in the -Y direction. The data driver 23D supplies a voltage corresponding to an image signal to each of the selected pixels P, and writes the image signal into each of the pixels P. Note that FIG. 2 illustrates only a portion of the pixels P arranged in a matrix. The liquid crystal display panel 22 also includes a polarizing plate, liquid crystal, etc.

[0018] The light source section 32 of the display unit 20 intermittently emits light to the liquid crystal display panel 22 based on a light source drive signal supplied from the control section 80 and synchronized with an image signal. The control section 80 supplies the light source drive signal to the light source section 32 and controls the emission timing t30 at which the light source section 32 emits light, thereby controlling the emission timing at which the display unit 20 emits display light L1. The light source drive signal and the emission timing t30 at which the light source section 32 emits light will be described later.

[0019] The light source unit 32 is, for example, a direct-type backlight provided on the back surface of the liquid crystal display panel 22. As shown in Fig. 3, the light source unit (backlight) 32 includes a housing 33, a plurality of LED (Light Emitting Diode) elements 34, and a driver circuit 36. The light source unit 32 also includes a reflective sheet, a diffusion sheet, etc., which are not shown.

[0020] The housing 33 accommodates the LED elements 34, the driver circuit 36, and the like. The LED elements 34 emit white light. The LED elements 34 are mounted on a mounting substrate 35 and connected in series in the row direction (+X direction) of the pixels P of the liquid crystal display panel 22. The mounting substrate 35 is arranged along the line sequential scanning direction (-Y direction) of the liquid crystal display panel 22 and connected to the driver circuit 36. The driver circuit 36 ​​supplies a current to the LED elements 34 based on a light source drive signal to cause the LED elements 34 to emit light. In this embodiment, the driver circuit 36 ​​causes all the LED elements 34 to emit light at once based on the light source drive signal. Therefore, in the light source section 32 of this embodiment, the entire surface of the light source section 32 emits light at the same timing. That is, the display light L1 is emitted from the entire surface of the display unit 20 at the same timing.

[0021] The polarization switching section 50 of the stereoscopic image display device 10 switches the polarization direction of the display light L1 emitted from the display unit 20 between a predetermined first direction (X direction) and a predetermined second direction based on a switching signal supplied from the control section 80 and synchronized with the image signal. In this embodiment, the predetermined second direction is the Y direction. Specifically, when a first image is displayed on the liquid crystal display panel 22 of the display unit 20, the polarization switching section 50 outputs the incident display light L1 while maintaining the polarization direction in the X direction. On the other hand, when a second image is displayed on the liquid crystal display panel 22 of the display unit 20, the polarization switching section 50 switches the polarization direction of the incident display light L1 to the Y direction and outputs it.

[0022] The polarization switching unit 50 is, for example, a TN liquid crystal element with a twist angle of 90°. As shown in FIG. 4, the polarization switching unit (TN liquid crystal element) 50 includes a liquid crystal 52, two light-transmitting substrates 54a and 54b having electrodes 53 for applying a voltage to the liquid crystal 52 and sandwiching the liquid crystal, and an alignment film (not shown) for aligning the liquid crystal 52. The light-transmitting substrates 54a and 54b are bonded together with a seal material 56. When an OFF-level switching signal is supplied to the polarization switching unit 50, the polarization direction of the display light L1 is rotated by 90° and the display light L2 having a polarization direction in the Y direction is output. On the other hand, when an ON-level switching signal is supplied to the polarization switching unit 50, the liquid crystal 52 is aligned perpendicular to the light-transmitting substrates 54a and 54b, and the polarization switching unit 50 maintains the polarization direction of the display light L1 in the X direction and outputs the display light L2. The display light L2 emitted from the polarization switching unit 50 is incident on the polarized bifocal lens 60. The switching signal will be described later.

[0023] The polarized bifocal lens 60 of the stereoscopic image display device 10 is a lens whose focal length with respect to the light emitted from the polarization switching unit 50, i.e., the display light L2 emitted from the polarization switching unit 50, varies depending on the polarization direction (X direction and Y direction) of the display light L2. The polarized bifocal lens 60 forms the first image and the second image on the first display surface 102 and the second display surface 104, respectively, as virtual images as seen by the observer. The first display surface 102 and the second display surface 104 are virtual display surfaces located at different positions in the depth direction (+Z direction) as seen by the observer. In this embodiment, as shown in FIG. 1, the first display surface 102 and the second display surface 104 are located farther away from the observer than the display unit 20. In addition, the second display surface 104 is located closer to the observer (-Z side) than the first display surface 102.

[0024] The observer views a virtual image of the first image on the first display surface 102 and a virtual image of the second image on the second display surface 104, which are displayed sequentially in a time-division manner, and recognizes that the display object is located between the first display surface 102 and the second display surface 104. The position of the display object recognized by the observer can be changed by adjusting the ratio of brightness (e.g., luminance) between the first image and the second image. For example, when the ratio of brightness between the first image and the second image is 1:1, the observer recognizes that the display object is located midway between the first display surface 102 and the second display surface 104.

[0025] The polarized bifocal lens 60 is, for example, a liquid crystal lens. The polarized bifocal lens (liquid crystal lens) 60 includes a first light-transmitting substrate 61, a second light-transmitting substrate 62, and a liquid crystal 64, as shown in FIG.

[0026] The first light-transmitting substrate 61 and the second light-transmitting substrate 62 are, for example, glass substrates. The first light-transmitting substrate 61 has a resin Fresnel lens 66 on a first main surface 61a facing the second light-transmitting substrate 62. The first light-transmitting substrate 61 and the second light-transmitting substrate 62 are bonded together with a sealant 67, and sandwich a liquid crystal 64 therebetween. The liquid crystal 64 is, for example, a nematic liquid crystal having a positive refractive index anisotropy (Δn=ne-no>0, ne: extraordinary ray refractive index, no: ordinary ray refractive index). The liquid crystal 64 is aligned in the X direction by an alignment film (not shown).

[0027] When display light L2 of a first image, whose polarization direction is the X direction, enters the polarized bifocal lens, the nematic liquid crystal having positive refractive index anisotropy is oriented in the X direction, so that the focal length of the polarized bifocal lens 60 for the display light L2 is short, and the first image is formed on the first display surface 102. On the other hand, when display light L2 of a second image, whose polarization direction is the Y direction, enters the polarized bifocal lens, the focal length of the polarized bifocal lens 60 for the display light L2 is long, and the second image is formed on the second display surface 104.

[0028] A control unit 80 of the stereoscopic image display device 10 controls the display unit 20 and the polarization switching unit 50 based on an input signal input from an external device (not shown). The control unit 80 has a display driving unit 82, a polarization switching driving unit 84, and a light source driving unit 86, as shown in FIG.

[0029] The display driver 82 of the control unit 80 generates a first image signal for displaying a first image and a second image signal for displaying a second image from the input signal. The display driver 82 also supplies the image signals to the liquid crystal display panel 22. Furthermore, the display driver 82 supplies a synchronization signal to the polarization switching driver 84 and the light source driver 86, the synchronization signal being synchronized with the start of the supply of the image signal (i.e., the start timing at which writing of the image signal starts).

[0030] The polarization switching drive unit 84 of the control unit 80 generates a switching signal based on the synchronization signal supplied from the display drive unit 82. In addition, the polarization switching drive unit 84 supplies the generated switching signal to the polarization switching unit 50. In this embodiment, when the first image is displayed on the liquid crystal display panel 22, the polarization switching drive unit 84 sets the switching signal to an ON level and supplies it to the polarization switching unit 50.

[0031] The light source drive unit 86 of the control unit 80 generates a light source drive signal based on the synchronization signal supplied from the display drive unit 82. In addition, the light source drive unit 86 supplies the generated light source drive signal to the driver circuit 36 ​​of the light source unit 32. In this embodiment, when an image signal different from an image signal that has already been written is to be written, the light source drive unit 86 generates a light source drive signal and supplies the light source drive signal to the light source unit 32.

[0032] 7 shows the hardware configuration of the control unit 80. The control unit 80 includes a CPU (Central Processing Unit) 92, a ROM (Read Only Memory) 94, a RAM (Random Access Memory) 96, and an input / output interface 98. The CPU 92, the ROM 94, the RAM 96, and the input / output interface 98 are connected by a bus 99. The CPU 92 executes various processes. The ROM 94 stores programs and data. The RAM 96 stores data. The input / output interface 98 inputs and outputs signals between the CPU 92, the liquid crystal display panel 22, the light source unit 32, the polarization switching unit 50, and an external device. The functions of the control unit 80 are realized by the CPU 92 executing the programs stored in the ROM 94.

[0033] Next, the light emission timing t30 of the light source unit 32 will be described. FIG. 8 shows the operation timing of the stereoscopic image display device 10. In FIG. 8, the first row shows the image signals (first image signal and second image signal) input to the liquid crystal display panel 22. The second row of FIG. 8 shows the transmittance of the pixel P in the first row in the line sequential scanning of the liquid crystal display panel 22, and the third row of FIG. 8 shows the transmittance of the pixel P in the last row in the line sequential scanning of the liquid crystal display panel 22. The fourth row of FIG. 8 shows the timing of the switching signal, and the fifth row of FIG. 8 shows the polarization direction of the display light L2 emitted from the polarization switching unit 50. Furthermore, the sixth row of FIG. 8 shows the timing of the light source drive signal.

[0034] In this embodiment, the display drive unit 82 supplies image signals to the liquid crystal display panel 22 at a cycle of 240 Hz (period of one frame: 4.2 ms), and the liquid crystal display panel 22 performs line-sequential scanning (i.e., writing to pixels P) at a cycle of 240 Hz. Also, as shown in the first row of Fig. 8, the display drive unit 82 supplies the same image signal twice in succession to the liquid crystal display panel 22, and the liquid crystal display panel 22 sequentially displays the first image and the second image. In Fig. 8, writing of the first image starts from timings t11 and t12, and then writing of the second image starts from timings t21 and t22.

[0035] 8, the transmittance of the pixel P in the first row of the liquid crystal display panel 22 changes from timing t11 and timing t21, and the transmittance of the pixel P in the last row of the liquid crystal display panel 22 changes from timing t12 and timing t22. Timing t11 corresponds to the start timing when the first writing of the first image starts, and timing t12 corresponds to the start timing when the second writing of the first image starts. Furthermore, timing t21 corresponds to the start timing when the first writing of the second image starts, and timing t22 corresponds to the start timing when the second writing of the second image starts.

[0036] In this embodiment, as shown in the fourth row of Fig. 8, the polarization switching drive unit 84 supplies an ON level switching signal to the polarization switching unit 50 during a period from timing t25, which is 0.2 ms before timing t11 when the first first image starts to be written, to timing t26, which is 0.2 ms before timing t21 when the first second image starts to be written. As a result, as shown in the fifth row of Fig. 8, the polarization direction of the display light L2 emitted from the polarization switching unit 50 switches from the Y direction to the X direction from timing t25. Also, the polarization direction of the display light L2 emitted from the polarization switching unit 50 switches from the X direction to the Y direction from timing t26.

[0037] The light source driving unit 86 sets the light emission timing t30 based on the start timing at which writing of an image signal of a different image is started. In this embodiment, timing t11 and timing t21 correspond to the start timing at which writing of an image signal of a different image is started. Hereinafter, the start timing at which writing of an image signal of a different image is started will be referred to as different image start timings t11 and t21.

[0038] In this embodiment, the light source driving unit 86 sets the light emission timing t30 to the timing when the latest end time of the switching of the polarization direction of the display light L2 of the polarization switching unit 50 and the response of the pixel P of the liquid crystal display panel 22 to the first image signal and the response to the second image signal from the start timings t11 and t21 of the different image has elapsed from the start timings t11 and t21 of the different image. The switching of the polarization direction of the display light L2 of the polarization switching unit 50 corresponds to the switching of the focal length of the variable-focus lens unit 40 for the display light L2 of the first image and the focal length for the display light L2 of the second image.

[0039] Specifically, if the times from the start timing t11, t21 of the different image to the end of switching the polarization direction of the display light L2 of the polarization switching unit 50 are Td1, Td2, respectively, the time from the start timing t11 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the first image signal is Tp1, and the time from the start timing t21 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the second image signal is Tp2, then, as shown in FIG. 8, the time Td2 is the longest. Therefore, as shown in the sixth row of FIG. 8, the light source driving unit 86 sets the light emission timing t30 to the timing when the time Td2 has elapsed from the start timing t11, t21 of the different image. As a result, the response of the pixel P of the last row of the liquid crystal display panel 22 ends, and then the polarization direction of the display light L2 is switched, and then the light source unit 32 emits light. Therefore, it is possible to prevent the first image displayed by the first image signal and the second image displayed by the second image signal from being mixed together. In this embodiment and the following embodiments, the time until completion refers to the time until the transmittance or luminance of the pixel P, or the display light L2, reaches 99% of the target value. For example, when displaying an image (white) with a transmittance of 100% to an image (black) with a transmittance of 0%, the time until completion means the time until the transmittance reaches 1%.

[0040] Furthermore, the light source driving unit 86 sets the light emission period Te of the light source unit 32 to a period before the polarization direction starts to be switched in the polarization switching unit 50. In this embodiment, the light source driving unit 86 sets the light emission period Te to a period 0.2 ms before the polarization direction starts to be switched in the polarization switching unit 50. As a result, the light source unit 32 causes all the LED elements 34 to emit light at once from the light emission timing t30 to 0.4 ms before the start timings t11 and t21 of the next different image.

[0041] As described above, in this embodiment, the light emission timing t30 of the light source unit 32 is set based on the start timings (different image start timings) t11 and t21 at which writing of image signals for displaying different images to the pixels P of the liquid crystal display panel 22 is started. Specifically, the light emission timing of the light source unit 32 is set to the timing at which the latest end time Td2 from the different image start timings t11 and t21 has elapsed. As a result, the response of the pixels P in the last row of the liquid crystal display panel 22 ends, and then the polarization direction of the display light L2 is switched, after which the light source unit 32 emits light. Therefore, it is possible to prevent the first image and the second image from being mixed, and to suppress crosstalk between the first image and the second image.

[0042] <Embodiment 2> In the first embodiment, the time Td2 from the start timing t21 of the different image to the end of switching of the polarization direction of the display light L2 is the longest. In the present embodiment, a case will be described where the time Tp2 from the start timing t21 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the second image signal is the longest.

[0043] In this embodiment, a PLZT (Lead Lanthanum Zirconate Titanate) element is used in the polarization switching section 50 instead of the TN liquid crystal element of the first embodiment. Also, the operation timing of the stereoscopic image display device 10 is different from that of the first embodiment. Other configurations of the stereoscopic image display device 10 are similar to those of the first embodiment.

[0044] 9, the polarization switching section (PLZT element) 50 of this embodiment includes two light-transmitting substrates 511 and 512, two electrodes 513 and 514, and a PLZT 516. The light-transmitting substrates 511 and 512 sandwich the PLZT 516, and the electrodes 513 and 514 apply a voltage to the PLZT 516. The PLZT 516 is a light-transmitting ferroelectric ceramic. The PLZT element can generally switch the polarization direction of the display light L1 between the X direction and the Y direction faster than the TN liquid crystal element (response time of the PLZT element: several μm to several hundred μm).

[0045] The light emission timing t30 of the light source unit 32 in this embodiment will be described. Here, differences from the timing in the first embodiment will be mainly described.

[0046] FIG. 10 shows the timing of the operation of the stereoscopic image display device 10 of this embodiment. In this embodiment, as shown in the fourth row of FIG. 10, the polarization switching drive unit 84 supplies an ON level switching signal to the polarization switching unit 50 during the period from the timing t11 at which the first first image starts to be written (the timing at which the different image starts) to the timing t21 at which the first second image starts to be written (the timing at which the different image starts). As a result, as shown in the fifth row of FIG. 10, the polarization direction of the display light L2 emitted from the polarization switching unit 50 switches from the Y direction to the X direction from the timing t11 at which the different image starts. Also, the polarization direction of the display light L2 emitted from the polarization switching unit 50 switches from the X direction to the Y direction from the timing t21 at which the different image starts. In this embodiment, since a PLZT element is used for the polarization switching unit 50, the times Td1 and Td2 from the timings t11 and t21 at which the different image starts to be written until the switching of the polarization direction of the display light L2 ends can be shortened as shown in the fifth row of FIG.

[0047] In this embodiment, as shown in FIG. 10, among the times Td1 and Td2 from the start timing t11 and t21 of the different image to the end of switching the polarization direction of the display light L2 of the polarization switching unit 50, the time Tp1 from the start timing t11 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the first image signal, and the time Tp2 from the start timing t21 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the second image signal, the time Tp2 is the longest. Therefore, as shown in the sixth row of FIG. 10, the light source driving unit 86 sets the light emission timing t30 to the timing when the time Tp2 has elapsed from the start timing t11 and t21 of the different image. In addition, the light source driving unit 86 sets the light emission period Te to the time before the start timing t11 and t21 of the different image. In this embodiment, the light source driving unit 86 sets the light emission period Te to 0.2 ms before the start timing t11 and t21 of the different image.

[0048] In this embodiment, by setting the light emission timing t30 to the timing when a time Tp2 has elapsed from the start timings t11 and t21 of the different images, the polarization direction of the display light L2 is switched, and then the light source unit 32 emits light after the response of the pixels P in the last row of the liquid crystal display panel 22 is completed. This makes it possible to prevent the first image and the second image from being mixed together, and to suppress crosstalk between the first image and the second image.

[0049] <Embodiment 3> In the first and second embodiments, the display light L1 is emitted at the same time from the entire surface of the display unit 20. In this embodiment, the display unit 20 of the stereoscopic image display device 10 sequentially emits the display light L1 for each of a plurality of emission regions. In this embodiment, a case where the display unit 20 is divided into four emission regions will be described.

[0050] Like the stereoscopic image display device 10 of the first embodiment, the stereoscopic image display device 10 of this embodiment includes a display unit 20, a polarization switching unit 50, a polarized bifocal lens 60, and a control unit 80. Since the configuration of the polarized bifocal lens 60 of this embodiment is similar to that of the polarized bifocal lens 60 of the first embodiment, the display unit 20, the polarization switching unit 50, and the control unit 80 will be described.

[0051] The display unit 20 of this embodiment includes a liquid crystal display panel 22 and a light source section 32, similar to the display unit 20 of the first embodiment. As shown in Fig. 11, the liquid crystal display panel 22 of this embodiment is divided into four display areas, a first display area 211 to a fourth display area 214, in the line sequential scanning direction. The first display area 211 to the fourth display area 214 correspond to the four emission areas, a first emission area 311 to a fourth emission area 314, respectively, of the light source section 32, which will be described later. The other configurations of the liquid crystal display panel 22 of this embodiment are similar to those of the liquid crystal display panel 22 of the first embodiment.

[0052] The light source unit 32 of this embodiment includes a housing 33, a plurality of LED elements 34, and a driver circuit 36, similar to the light source unit 32 of the first embodiment. The light source unit 32 also includes a reflective sheet, a diffusion sheet, and the like, which are not shown. As shown in FIG. 12, the light source unit 32 of this embodiment is divided into four first to fourth emission regions 311 to 314 in the line sequential scanning direction of the liquid crystal display panel 22. The driver circuit 36 ​​of this embodiment causes the LED elements 34 to emit light for each of the first to fourth emission regions 311 to 314, based on a light source drive signal supplied from the light source drive unit 86 of the control unit 80. In this embodiment, the first to fourth emission regions 311 to 314 correspond to the first to fourth display regions 211 to 214 of the liquid crystal display panel 22, respectively, and therefore the display unit 20 emits display light L1 for each of the first to fourth emission regions 311 to 314. The first emission region 311 to the fourth emission region 314 correspond to the emission regions of the display unit 20.

[0053] The polarization switching section 50 of this embodiment is a TN liquid crystal element, similar to the polarization switching section 50 of the first embodiment. As shown in FIG. 13, the polarization switching section 50 of this embodiment is divided into four switching regions, a first switching region 521 to a fourth switching region 524, which correspond to the first emission region 311 to the fourth emission region 314 of the light source section 32, respectively. The first switching region 521 to the fourth switching region 524 independently switch the polarization direction of the display light L1 between the X direction and the Y direction based on a switching signal supplied from the polarization switching drive section 84 of the control section 80. In this embodiment, the electrode 53 of the polarization switching section 50 is divided into four in the line sequential scanning direction in order to independently supply switching signals to the first switching region 521 to the fourth switching region 524.

[0054] Like the control unit 80 of the first embodiment, the control unit 80 of the present embodiment has a display driving unit 82, a polarization switching driving unit 84, and a light source driving unit 86. The hardware configuration of the control unit 80 of the present embodiment is also similar to that of the first embodiment.

[0055] Similar to the display driver 82 of the first embodiment, the display driver 82 of the present embodiment generates an image signal from an input signal and supplies the generated image signal to the liquid crystal display panel 22. Furthermore, the display driver 82 supplies a synchronization signal, which is synchronized with the start of the supply of the image signal (the start timing at which writing of the image signal starts), to the polarization switching driver 84 and the light source driver 86 each time an image signal is supplied to each of the first display area 211 to the fourth display area 214.

[0056] Similar to the polarization switching driver 84 of the first embodiment, the polarization switching driver 84 of the present embodiment generates a switching signal based on a synchronization signal supplied from the display driver 82, and supplies the generated switching signal to the polarization switching section 50. The polarization switching driver 84 of the present embodiment supplies switching signals to each of the first switching region 521 to the fourth switching region 524 of the polarization switching section 50 independently.

[0057] Similar to the light source driving section 86 of the first embodiment, the light source driving section 86 of the present embodiment generates a light source driving signal based on a synchronization signal supplied from the display driving section 82, and supplies the generated light source driving signal to the driver circuit 36 ​​of the light source section 32. The light source driving section 86 of the present embodiment supplies a light source driving signal to the driver circuit 36 ​​every time a different image is displayed in each of the first to fourth display areas 211 to 214 of the liquid crystal display panel 22. As a result, the driver circuit 36 ​​causes the LED elements 34 to emit light sequentially at the light emission timing t300 for each of the first to fourth emission areas 311 to 314.

[0058] Next, the light emission timing t300 of the light source section 32 of this embodiment will be described. FIG. 14 shows the operation timing of the stereoscopic image display device 10. In FIG. 14, the first row shows image signals (first image signal and second image signal) input to the liquid crystal display panel 22. The second to fifth rows of FIG. 14 respectively show the transmittance of the pixels P in the last row of the first to fourth display regions 211 to 214 of the liquid crystal display panel 22. The sixth to ninth rows of FIG. 14 respectively show the timing of the switching signals in the first to fourth switching regions 521 to 524 of the polarization switching section 50 and the polarization direction of the emitted display light L2. The tenth to thirteenth rows of FIG. 14 respectively show the timing of the light source drive signals in the first to fourth emission regions 311 to 314 of the light source section 32.

[0059] In this embodiment, the display drive unit 82 supplies an image signal to the liquid crystal display panel 22 at a cycle of 120 Hz (period of one frame: 8.3 ms), and the liquid crystal display panel 22 performs line-sequential scanning (writing to pixels P) at a cycle of 120 Hz. In FIG. 14, writing of a first image to the first display area 211 starts at timing t111, and writing of a second image to the first display area 211 starts at timing t211. Writing of a first image to the second display area 212 starts at timing t112, and writing of a second image to the second display area 212 starts at timing t212. Writing of a first image to the third display area 213 starts at timing t113, and writing of a second image to the third display area 213 starts at timing t213. Writing of a first image to the fourth display area 214 starts at timing t114, and writing of a second image to the fourth display area 214 starts at timing t214. For ease of understanding, the light emission timing t300 will be described using the first display region 211, the first switching region 521, and the first emission region 311 as examples.

[0060] In the first display region 211, the first image is written in the period from timing t111 to timing t112, and the second image is written in the period from timing t211 to timing t212. Therefore, as shown in the second row of Fig. 14, the transmittance of the pixels P in the last row of the first display region 211 changes from timing t112 to timing t212. Furthermore, timing t111 and timing t211 correspond to start timings at which writing of an image signal for displaying a different image is started in the first display region 211 (start timings of a different image). Hereinafter, timing t111 and timing t211 will be referred to as start timing t111 of a different image and start timing t211 of a different image, respectively.

[0061] 14, the polarization switching drive unit 84 of this embodiment supplies an ON level switching signal to the polarization switching unit 50 during the period from the start timing t111 of the different image to the start timing t211 of the different image. The polarization direction of the display light L2 emitted from the first switching region 521 switches from the X direction to the Y direction from the start timing t111 of the different image. Also, the polarization direction of the display light L2 emitted from the first switching region 521 switches from the Y direction to the X direction from the start timing t211 of the different image.

[0062] The light source driving unit 86 of this embodiment sets the light emission timing t300 of the first emission region 311 to a timing when the time Td2 has elapsed from the start timing t111 or t211 of the different image, when the switching of the polarization direction of the display light L2 of the first switching region 521 and the response of the pixel P of the first display region 211 to the first image signal and the response to the second image signal end latest from the start timing t111 or t211 of the different image. In this embodiment, as shown in FIG. 14, the time Td2 when the switching of the polarization direction of the display light L2 of the first switching region 521 ends from the start timing t211 of the different image is the longest. Therefore, the light source driving unit 86 of this embodiment sets the light emission timing t300 of the first emission region 311 to a timing when the time Td2 has elapsed from the start timing t111 or t211 of the different image, as shown in the tenth row of FIG. As a result, the response of the pixels P in the last row of the first display region 211 ends, and then, after the polarization direction of the display light L2 in the first switching region 521 is switched, light is emitted from the first emission region 311 of the light source unit 32. This makes it possible to prevent the first image displayed by the first image signal and the second image displayed by the second image signal from being mixed together. Note that, also in this embodiment, the switching of the polarization direction of the display light L1 by the polarization switching unit 50 corresponds to the switching of the focal length of the variable-focus lens unit 40 for the display light L1 of the first image and the focal length for the display light L1 of the second image.

[0063] Furthermore, the light source driving unit 86 of this embodiment sets the light emission period Te of the first emission region 311 to be from the light emission timing t300 to the start timing t111, t211 of the next different image. As a result, the first emission region 311 of the light source unit 32 emits light during the period from the light emission timing t300 to the start timing t111, t211 of the different image.

[0064] The light emission timing t300 and light emission period Te are also set in the second display area 212, the second switching area 522, the second emission area 312, the third display area 213, the third switching area 523, the third emission area 313, and the fourth display area 214, the fourth switching area 524, and the fourth emission area 314, in the same way as the first display area 211, the first switching area 521, and the first emission area 311.

[0065] As described above, in this embodiment, the light emission timing t300 of the first emission region 311 to the fourth emission region 314 of the light source unit 32 is set based on the start timings t111 to t214 of the different images. Specifically, the light emission timing t300 is set to the timing at which the longest time Td2 has elapsed from the start timing t111 to t214 of the different image to the end of the different image. This makes it possible to prevent the first image and the second image from being mixed together, and to suppress crosstalk between the first image and the second image.

[0066] <Embodiment 4> In the first to third embodiments, the variable-focus lens unit 40 includes the polarization switching section 50 and the polarized bifocal lens 60, but the variable-focus lens unit 40 may be a liquid crystal lens 600.

[0067] Like the stereoscopic image display device 10 of the first embodiment, the stereoscopic image display device 10 of this embodiment includes a display unit 20, a variable-focus lens unit 40, and a control unit 80. The configuration of the display unit 20 of the stereoscopic image display device 10 of this embodiment is similar to that of the display unit 20 of the first embodiment. Here, the variable-focus lens unit 40, the control unit 80, and the light emission timing t30 will be described.

[0068] The variable-focus lens unit 40 of this embodiment is a liquid crystal lens 600, as shown in FIG. 15. The liquid crystal lens 600 changes the focal length of polarized light having a polarization direction in a predetermined first direction (X direction), i.e., the display light L1 emitted from the display unit 20, by an applied voltage. Specifically, the liquid crystal lens 600 changes the focal length of the display light L1 emitted from the display unit 20 based on a switching signal supplied from the control unit 80 and synchronized with an image signal. The liquid crystal lens 600 switches the focal length of the display light L1 emitted from the display unit 20, and forms a first image on the first display surface 102 when the first image is displayed on the display unit 20, and forms a second image on the second display surface 104 when the second image is displayed on the display unit 20. The liquid crystal lens 600 has a third light-transmissive substrate 610, a fourth light-transmissive substrate 620, and a liquid crystal 630, as shown in FIG. 16 and FIG. 17.

[0069] The third light-transmitting substrate 610 is, for example, a flat glass substrate. The third light-transmitting substrate 610 and the fourth light-transmitting substrate 620 are bonded together with a sealant 615, and sandwich a liquid crystal 630. The third light-transmitting substrate 610 has a first electrode 612 and an alignment film (not shown).

[0070] The first electrode 612 of the third light-transmissive substrate 610 is formed in a rectangular shape on a first main surface 610a of the third light-transmissive substrate 610. The first electrode 612 faces a second electrode 622 of the fourth light-transmissive substrate 620, which will be described later. The first electrode 612 is connected to the control unit 80.

[0071] The alignment film of the third light-transmissive substrate 610 is provided on the first electrode 612. The alignment film aligns the liquid crystal 630 in the X direction. The alignment film is, for example, a polyimide alignment film that has been subjected to a rubbing process.

[0072] The fourth light-transmissive substrate 620 is a flat glass substrate, similar to the third light-transmissive substrate 610. The fourth light-transmissive substrate 620 and the third light-transmissive substrate 610 are attached to each other with a sealant 615, and sandwich a liquid crystal 630. The fourth light-transmissive substrate 620 has two second electrodes 622 and an alignment film (not shown).

[0073] The second electrodes 622 of the fourth light-transmissive substrate 620 are respectively disposed at an end on the +X side and an end on the -X side of the first main surface 620a of the fourth light-transmissive substrate 620. Each of the second electrodes 622 extends in the Y direction and is connected to the control unit 80.

[0074] The alignment film of the fourth light-transmissive substrate 620 is provided on the first major surface 620a and the second electrode 622. Like the alignment film of the third light-transmissive substrate 610, the alignment film aligns the liquid crystal 630 in the X direction.

[0075] The liquid crystal 630 is a nematic liquid crystal having positive dielectric anisotropy and positive refractive index anisotropy, and is aligned in the X direction when no voltage is applied.

[0076] In the liquid crystal lens 600, by applying a voltage between the first electrode 612 and the second electrode 622, a quadratic curve-shaped potential is formed between the two second electrodes 622 when viewed in the XZ cross section. The liquid crystal 630 is oriented along the formed quadratic curve-shaped potential. Due to the orientation of the liquid crystal 630 along the quadratic curve-shaped potential, the liquid crystal lens 600 acts as a lens for the display light L1 emitted from the display unit 20. The focal length of the liquid crystal lens 600 depends on the value of the applied voltage.

[0077] In this embodiment, when a predetermined first voltage is applied between the first electrode 612 and the second electrode 622, the liquid crystal lens 600 switches the focal length for the display light L1 to a first focal length, thereby forming the display light L1 of the first image on the first display surface 102. Also, when a predetermined second voltage (first voltage>second voltage) is applied between the first electrode 612 and the second electrode 622, the liquid crystal lens 600 switches the focal length for the display light L1 to a second focal length, thereby forming the display light L1 of the second image on the second display surface 104.

[0078] A control unit 80 of this embodiment controls the display unit 20 and the liquid crystal lens 600 based on an input signal input from an external device (not shown). As shown in Fig. 18, the control unit 80 has a display drive unit 82, a focus switching drive unit 814, and a light source drive unit 86. Since the configurations of the display drive unit 82 and the light source drive unit 86 of this embodiment are the same as those of the first embodiment, only the focus switching drive unit 814 will be described.

[0079] The focus switching drive unit 814 generates two types of focus switching signals, a first focus switching signal and a second focus switching signal, based on the synchronization signal supplied from the display drive unit 82. In addition, the polarization switching drive unit 84 supplies the focus switching signal to the liquid crystal lens 600. In this embodiment, when a first image is displayed on the liquid crystal display panel 22, the focus switching drive unit 814 generates a first focus switching signal (first voltage) and supplies the first focus switching signal to the liquid crystal lens 600. In addition, when a second image is displayed on the liquid crystal display panel 22, the focus switching drive unit 814 generates a second focus switching signal (second voltage) and supplies the second focus switching signal to the liquid crystal lens 600.

[0080] Next, the light emission timing t30 of the light source unit 32 of this embodiment will be described. Here, differences from the timing of the first embodiment will be mainly described.

[0081] FIG. 19 shows the timing of the operation of the stereoscopic image display device 10 of this embodiment. In this embodiment, as shown in the fourth row of FIG. 19, the focus switching drive unit 814 supplies a first focus switching signal (first voltage) to the liquid crystal lens 600 during a period from timing t25, which is 0.2 ms before timing t11 when the first first image starts to be written, to timing t26, which is 0.2 ms before timing t21 when the first second image starts to be written. In addition, the focus switching drive unit 814 supplies a second focus switching signal (second voltage) to the liquid crystal lens 600 during a period from timing t26 to timing t25. As a result, as shown in the fifth row of FIG. 19, the focal length of the liquid crystal lens 600 switches from the second focal length to the first focal length from timing t25. In addition, the focal length of the liquid crystal lens 600 switches from the first focal length to the second focal length from timing t26.

[0082] In this embodiment, as shown in Fig. 19, among the times Td1 and Td2 from the start timing t11 and t21 of the different image to the end of the switching of the focal length of the liquid crystal lens 600, the time Tp1 from the start timing t11 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the first image signal, and the time Tp2 from the start timing t21 of the different image to the end of the response of the pixel P of the liquid crystal display panel 22 to the second image signal, the time Td2 is the longest. Therefore, as shown in the sixth row of Fig. 10, the light source driving unit 86 sets the light emission timing t30 to the timing when the time Td2 has elapsed from the start timing t11 and t21 of the different image. The switching of the focal length of the liquid crystal lens 600 corresponds to the switching of the focal length of the variable-focus lens unit 40 for the display light L1 of the first image and the display light L1 of the second image.

[0083] In this embodiment, the light emission timing t30 is set to the timing when the time Td2 has elapsed from the start timings t11 and t21 of the different images, so that the focal length (imaging position) of the liquid crystal lens 600 with respect to the display light L1 is switched, and then the light source unit 32 emits light after the response of the pixels P in the last row of the liquid crystal display panel 22 is completed. This makes it possible to prevent the first image and the second image from being mixed together, and to suppress crosstalk between the first image and the second image. In addition, in this embodiment, by using the liquid crystal lens 600 in the variable-focus lens unit 40, it is not necessary to separately provide the polarization switching unit 50 of the first to second embodiments.

[0084] <Embodiment 5> In the first, second and fourth embodiments, the display drive unit 82 supplies the same image signal twice in succession to the liquid crystal display panel 22. That is, the display drive unit 82 writes the same image signal continuously to the pixels P of the liquid crystal display panel 22. In this case, it is preferable that the polarity of the voltage written to each pixel P is inverted for each write, as shown in FIG. 20. This makes it possible to suppress burn-in of the display on the liquid crystal display panel 22.

[0085] Specifically, in the pixel circuit shown in Fig. 21, the display drive unit 82 reverses the magnitude relationship between the potential Vcom of the common electrode of the liquid crystal display panel 22 and the potential Vpi on the TFT side of the liquid crystal display panel 22 for each write. This allows the polarity of the voltage written to the pixel P of the liquid crystal display panel 22 to be reversed for each write, as shown in Fig. 20.

[0086] FIG. 22 shows an example of change in polarity of voltage written to pixel P when displaying the first and second images in FIG. 20. Here, the first image displays the number "1" and the second image displays the number "2". FIG. 22(a) to FIG. 22(d) show frame inversion driving in which all pixels are inverted with the same polarity. Also, FIG. 22(e) to FIG. 22(h) show pixel inversion driving in which adjacent pixels have different polarities.

[0087] In the first frame starting from t11 in FIG. 20, a voltage for displaying the first image is written to each pixel P with a positive polarity as shown in FIG. 22(a). Then, in the second frame starting from t12, a voltage for displaying the first image is written to each pixel P with a negative polarity as shown in FIG. 22(b). Next, in the third frame starting from t21, a voltage for displaying the second image is written to each pixel P with a positive polarity as shown in FIG. 22(c). Next, in the fourth frame starting from t22, a voltage for displaying the second image is written to each pixel P with a negative polarity as shown in FIG. 22(d). In this way, frame inversion is performed for each write.

[0088] As another inversion drive, in the first frame starting from t11 in FIG. 20, as shown in FIG. 22(e), the voltage for displaying the first image is written with different polarity for each adjacent pixel P. Then, in the second frame starting from t12, as shown in FIG. 22(f), the voltage for displaying the first image is written with the polarity inverted for each pixel. Next, in the third frame starting from t21, as shown in FIG. 22(g), the voltage for displaying the second image is written with the polarity inverted for each pixel from the second frame. Next, in the fourth frame starting from t22, as shown in FIG. 22(h), the voltage for displaying the second pixel is written with the polarity inverted for each pixel from the third frame. In this way, pixel inversion is performed for each write.

[0089] In addition to the above frame inversion and pixel inversion, for example, scanning line inversion in which the polarity is inverted for each row, signal line inversion in which the polarity is inverted for each column, etc. can be applied.

[0090] <Modification> Although the embodiments have been described above, the present disclosure can be modified in various ways without departing from the gist of the present disclosure.

[0091] Although the display unit 20 in the first to fourth embodiments includes a liquid crystal display panel 22 and a light source section 32, the configuration of the display unit 20 is not limited thereto. For example, as shown in FIG. 23, the stereoscopic image display device 10 may include a display unit 20A including a self-luminous display panel 712 and a shutter section 714, instead of the display unit 20 including the liquid crystal display panel 22 and the light source section 32. The self-luminous display panel 712 is, for example, an organic EL (Electro Luminescence) display panel that is active-matrix driven by TFTs. The shutter section 714 intermittently blocks the light emitted from the self-luminous display panel 712. The shutter section 714 is, for example, a liquid crystal shutter that operates in a TN mode. In this case, the control section 80 supplies a blocking signal to the shutter section 714 instead of a light source drive signal. The shutter section 714 blocks the light emitted from the self-luminous display panel 712 based on the blocking timing and blocking period of the blocking signal. That is, the control unit 80 controls the timing at which the shutter section 714 blocks the light emitted from the self-luminous display panel 712, thereby controlling the emission timing at which the display unit 20 emits the display light L1.

[0092] 24, the stereoscopic image display device 10 may include a display unit 20B having a self-luminous display panel 716 and a polarizing plate 718, instead of the display unit 20 having the liquid crystal display panel 22 and the light source unit 32. The self-luminous display panel 716 emits light at the same timing as the light emission timings t30 and t300 of the light source unit 32 in the first to third embodiments, using a known technique. The polarizing plate 718 emits the light emitted from the self-luminous display panel 716 as display light L1 whose polarization direction is a predetermined first direction.

[0093] In the first embodiment, the light source section 32 of the display unit 20 is a direct type backlight, but the light source section 32 is not limited to a direct type backlight. The light source section 32 of the display unit 20 may be, for example, a side edge type backlight.

[0094] Furthermore, the polarization switching section 50 is not limited to the TN liquid crystal element and the PLZT element, but may be, for example, an element that utilizes the Faraday effect.

[0095] Furthermore, the variable-focus lens unit 40 is not limited to the polarization switching unit 50, the polarized bifocal lens 60, and the liquid crystal lens 600. For example, the variable-focus lens unit 40 may be a liquid lens whose focal length changes depending on the applied voltage. For example, a liquid lens using electrowetting can be used as the liquid lens. The liquid lens using electrowetting has a conductive substrate covered with a layer having insulating properties and hydrophobic properties, insulating droplets deposited on the conductive substrate, and a conductive liquid for applying a voltage to the insulating droplets. In the liquid lens using electrowetting, the shape of the insulating droplets changes when a voltage is applied to the insulating droplets by the conductive substrate and the conductive liquid. This changes the focal length of the liquid lens using electrowetting. Another example of the liquid lens is a liquid lens having a high refractive index liquid (refractive index: 1.4 to 1.7) and a PDMS (polydimethylsiloxane) film sandwiching the high refractive index liquid, and the focal length changes depending on the change in shape of the PDMS film.

[0096] In the first embodiment, the polarization switching driver 84 supplies an ON level switching signal to the polarization switching unit 50 during the period from timing t25, which is 0.2 ms before the start timing t11 of the different image, to timing t26, which is 0.2 ms before the start timing t21 of the different image. The timings t25 and t26 are not limited to 0.2 ms before the start timings t11 and t21 of the different image. In addition, the light source driver 86 sets the light emission period Te to the period from the light emission timing t30 to 0.2 ms before the timings t25 and t26, but the light emission period Te is not limited to 0.2 ms before the timings t25 and t26. In the fourth embodiment, the timings t25 and t26 are not limited to 0.2 ms before the start timings t11 and t21 of the different image.

[0097] In the third embodiment, the liquid crystal display panel 22, the light source section 32, and the polarization switching section 50 are each divided into four regions, but the number of divided regions is not limited to four.

[0098] In the third embodiment, a liquid crystal lens 600 may be provided instead of the polarization switching unit 50 and the polarized bifocal lens 60. In this case, the liquid crystal lens 600 is divided into four variable regions corresponding to the first emission region 311 to the fourth emission region 314 of the light source unit 32, respectively. Each of the variable regions independently switches the focal length for the display light L1 based on a switching signal supplied from a focus switching drive unit 814. Note that the first electrode 612 and the second electrode 622 are divided in the line sequential scanning direction in order to independently supply a switching signal to each of the variable regions.

[0099] In the first to fourth embodiments, the time until the end is the time until the transmittance or luminance of the pixel P, or the display light L1, reaches 99% of a target value. The time until the end may be any time until the amount of change in the transmittance, luminance, polarization direction, etc. becomes sufficiently small. For example, in the case where the polarization direction changes sharply as in the polarization switching unit 50 of the second embodiment, the time until the end may be the time until the amount of change reaches 90%.

[0100] In the fifth embodiment, an image signal of the same image is written to the pixel P of the liquid crystal display panel 22 twice in succession, and the polarity of the voltage written to the pixel P of the liquid crystal display panel 22 is inverted between the first and second writes. As shown in Fig. 25, even when the first and second images are written once each, the following can be done. Specifically, the display drive unit 82 may make the polarity of the voltage written to the pixel P of the liquid crystal display panel 22 the same when displaying the successive first and second images, and may invert the polarity of the voltage written to the pixel P of the liquid crystal display panel 22 when displaying the next first and second images.

[0101] Fig. 26 shows an example of rewriting the image in Fig. 25. Here, the displayed image is rewritten in response to an image signal, with the pixels P being selected line by line by the gate driver 23G. That is, when the image signal of the first image is written at t11 ​​shown in Fig. 25, the second image shown by the circle in Fig. 26 is rewritten line by line to the first image, and at the time of t12, the display is switched to the first image shown by the white square in Fig. 26. Fig. 26 shows the period from t11 to t12, but the same operation is performed from t21 to t22, except that the image to be rewritten is different. In addition, in FIG. 25, the same image is displayed over two frames, but it is sufficient that the same image is written for at least one frame.

[0102] FIG. 27 shows another example of the polarity of the voltage applied to the pixel. In FIG. 27, one frame period t11-t21 is composed of a writing period t11-t1b by an image signal and a blanking period t1b-t21 in which there is no image signal within one frame period. The next frame period t21-t11 is composed of a writing period t21-t2b by an image signal and a blanking period t2b-t11. Even in this case, a voltage can be applied to the pixel P with the same polarity as in FIG. 25. Also, in the examples shown in FIG. 25 and FIG. 27, inversion driving such as frame inversion, pixel inversion, scanning line inversion, and signal line inversion shown in FIG. 22 can be applied.

[0103] When the stereoscopic image display device 10 is used in a head mounted display, the stereoscopic image display device 10 may include a variable focus lens unit 40 for the right eye and a variable focus lens unit 40 for the left eye. The head mounted display may also include a stereoscopic image display device 10 for the right eye and a stereoscopic image display device 10 for the left eye.

[0104] In each embodiment, the stereoscopic image display device 10 using a monochrome liquid crystal panel has been described as an example, but a color liquid crystal panel may be used instead of the monochrome liquid crystal panel. In this case, the pixel P may be a sub-pixel that is color-coded into R (red), G (green), B (blue), etc.

[0105] Although the preferred embodiments have been described above, the present disclosure is not limited to such specific embodiments, and the present disclosure includes the invention described in the claims and their equivalents. [Explanation of symbols]

[0106] 10 stereoscopic image display device, 20, 20A, 20B display unit, 22 liquid crystal display panel, 23D data driver, 23G gate driver, 32 light source unit, 33 housing, 34 LED element, 35 mounting board, 36 driver circuit, 40 variable focus lens unit, 50 polarization switching unit, 52 liquid crystal, 53, 513, 514 electrode, 54a, 54b, 511, 512 light-transmitting substrate, 56 sealant, 60 polarized bifocal lens, 61 first light-transmitting substrate, 61a first main surface of first light-transmitting substrate, 62 second light-transmitting substrate, 64 liquid crystal, 66 Fresnel lens, 67 sealant, 80 control unit, 82 display drive unit, 84 polarization switching drive unit, 86 light source drive unit, 92 CPU, 94 ROM, 96 RAM, 98 input / output interface, 99 bus, 102 First display surface, 104 Second display surface, 211 First display region, 212 Second display region, 213 Third display region, 214 Fourth display region, 311 First emission region, 312 Second emission region, 313 Third emission region, 314 Fourth emission region, 416 PLZT, 521 First switching region, 522 Second switching region, 523 Third switching region, 524 Fourth switching region, 600 Liquid crystal lens, 610 Third light-transmitting substrate, 610a First main surface of third light-transmitting substrate, 612 First electrode, 615 Sealing material, 620 Fourth light-transmitting substrate, 620a First main surface of fourth light-transmitting substrate, 622 Second electrode, 630 Liquid crystal, 712, 716 Self-luminous display panel, 714 Shutter section, 718 Polarizing plate, 814 Focus switching driver, L1, L2 display light, P pixel, t11, t21, t111, t112, t113, t114, t211, t212, t213, t214 start timing of different images (timing), t12, t22, t25, t26, t1b, t2b timing, t30, t300 light emission timing, Td1, Td2, Tp1, Tp2 time, Te light emission period

Claims

1. a display unit that sequentially displays a first image based on a first image signal and a second image based on a second image signal, and emits display light for the first image and display light for the second image; a variable-focus lens unit that switches between a focal length for the display light of the first image and a focal length for the display light of the second image; a control unit that controls an emission timing at which the display unit emits display light for the first image and display light for the second image, the first image and the second image are two-dimensional images obtained by projecting a display object from a side of an observer onto a first display surface and a second display surface that are located at different positions in a depth direction as viewed from the observer, respectively; the variable-focus lens unit forms the first image and the second image as virtual images on the first display surface and the second display surface, respectively; the control unit controls the emission timing based on a start timing at which writing of an image signal of a different image to a pixel of the display unit starts; the control unit sets the emission timing to a timing at which a time has elapsed from the start timing that is the latest to end among switching of a focal length of the variable-focus lens unit for the display light of the first image and a focal length of the variable-focus lens unit for the display light of the second image, a response of the pixels of the display unit to the first image signal, and a response of the pixels of the display unit to the second image signal. Stereoscopic image display device.

2. the display unit includes a light source unit that emits light, and a liquid crystal display panel that modulates the light emitted from the light source unit to display the first image and the second image, the first image signal and the second image signal are written into the liquid crystal display panel; The control unit controls the emission timing by controlling the light emission timing at which the light source unit emits the light. The stereoscopic image display device according to claim 1 .

3. When the first image signal for displaying the first image or the second image signal for displaying the second image are successively written to pixels of the liquid crystal display panel, the polarity of the voltage written to each pixel of the liquid crystal display panel is inverted for each write. The stereoscopic image display device according to claim 2 .

4. If the first image and the second image are written one at a time, In the display of the first image and the second image successively, the polarity of the voltage written to the pixel of the liquid crystal display panel is the same for the first image and the second image, and in the display of the next first image and the second image, the polarity of the voltage written to the pixel of the liquid crystal display panel is inverted. The stereoscopic image display device according to claim 2 .

5. A display unit which sequentially displays a first image displayed by a first image signal and a second image displayed by a second image signal, and emits display light for the first image and display light for the second image; a variable-focus lens unit that switches between a focal length for the display light of the first image and a focal length for the display light of the second image; a control unit that controls an emission timing at which the display unit emits display light for the first image and display light for the second image, the first image and the second image are two-dimensional images obtained by projecting a display object from a side of an observer onto a first display surface and a second display surface that are located at different positions in a depth direction as viewed from the observer, respectively; the variable-focus lens unit forms the first image and the second image as virtual images on the first display surface and the second display surface, respectively; the control unit controls the emission timing based on a start timing at which writing of an image signal of a different image to a pixel of the display unit starts; the display unit includes a self-luminous display panel that displays the first image and the second image, and a shutter section that blocks light emitted from the self-luminous display panel; the first image signal and the second image signal are written into the self-luminous display panel; the control unit controls the emission timing by controlling a blocking timing at which the shutter unit blocks the light emitted from the self-luminous display panel. Stereoscopic image display device.

6. the control unit sets the emission timing to a timing at which a time has elapsed from the start timing that is the latest to end among switching of a focal length of the variable-focus lens unit for the display light of the first image and a focal length of the variable-focus lens unit for the display light of the second image, a response of the pixels of the display unit to the first image signal, and a response of the pixels of the display unit to the second image signal. The stereoscopic image display device according to claim 5 .

7. The display unit emits display light of the first image and display light of the second image as polarized light having a polarization direction in a predetermined first direction. The stereoscopic image display device according to claim 1 .

8. The variable focus lens unit comprises: a polarization switching unit that outputs the display light of the first image while maintaining the polarization direction of the display light in the predetermined first direction when the first image is displayed on the display unit, and that outputs the display light of the second image while changing the polarization direction of the display light of the second image to a predetermined second direction different from the predetermined first direction when the second image is displayed on the display unit, thereby switching the polarization direction of the output light between the predetermined first direction and the predetermined second direction; a polarized bifocal lens having a focal length for the light emitted from the polarization switching unit that varies depending on the polarization direction of the light, The stereoscopic image display device according to claim 7 .

9. the display unit displays the first image and the second image by line-sequential scanning, and sequentially emits display light of the first image and display light of the second image from a plurality of emission regions divided in a direction of the line-sequential scanning, the polarization switching unit has a plurality of switching regions that switch the polarization direction of the emitted light corresponding to each of the plurality of emission regions, The control unit controls the emission timing for each of the emission regions based on the start timing for each of the emission regions. The stereoscopic image display device according to claim 8 .

10. The variable-focus lens unit is a liquid crystal lens that changes a focal length for polarized light having a polarization direction in the predetermined first direction in response to an applied voltage. The stereoscopic image display device according to claim 7 .

11. the display unit displays the first image and the second image by line-sequential scanning, and sequentially emits display light of the first image and display light of the second image from a plurality of emission regions divided in a direction of the line-sequential scanning, the liquid crystal lens has a plurality of variable regions that change a focal length for polarized light having a polarization direction of the predetermined first direction in correspondence with each of the plurality of exit regions; The control unit controls the emission timing for each of the emission regions based on the start timing for each of the emission regions. The stereoscopic image display device according to claim 10.

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