Indication device

Abstract

To provide a display device that can improve the quality of the display. [Solution] According to one embodiment, the display device comprises an eye-tracking sensor configured to detect the user's gaze, a liquid crystal panel, an illumination device configured to illuminate the liquid crystal panel, a projection optical system configured to project an image displayed on the liquid crystal panel toward the user, a variable focus device configured to change the focal length, and a control unit that controls the variable focus device based on the output from the eye-tracking sensor. The control unit sets the focal length of the variable focus device to a first focal length and controls it to generate the image in a focused state. When a saccade is detected based on the output from the eye-tracking sensor, it sets the focal length of the variable focus device to a second focal length different from the first focal length and controls it to generate the image in a defocused state.

Description

Technical Field

[0001] Embodiments of the present invention relate to a display device.

Background Art

[0002] In a display device, a technique for displaying an image in a Field Sequential Color (FSC) method is known. When a saccade occurs while a user is observing such a display device, there is a problem that color breakup due to a temporal shift of the displayed image is visually recognized. Therefore, improvement of display quality is desired.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the objectives of the embodiments is to provide a display device capable of improving display quality.

Means for Solving the Problems

[0005] According to an embodiment, the display device is The system includes an eye-tracking sensor configured to detect the user's gaze, a liquid crystal panel, a first light-emitting element configured to emit light in a first wavelength range, and a second light-emitting element configured to emit light in a second wavelength range different from the first wavelength range, and an illumination device configured to illuminate the liquid crystal panel, a projection optical system positioned between the liquid crystal panel and the user's observation position and configured to project an image displayed on the liquid crystal panel toward the user, a variable focus device configured to change its focal length, and a control unit that controls the liquid crystal panel and the illumination device, and controls the variable focus device based on the output from the eye-tracking sensor, wherein the control unit controls the system to display a color image in the first wavelength range on the liquid crystal panel in synchronization with the lighting up of the first light-emitting element, to display a color image in the second wavelength range on the liquid crystal panel in synchronization with the lighting up of the second light-emitting element, to set the focal length of the variable focus device to the first focal length and generate the image in focus, and when a saccade is detected based on the output from the eye-tracking sensor, to set the focal length of the variable focus device to a second focal length different from the first focal length and generate the image in defocus.

[0006] According to the embodiment, the display device is The system includes an eye-tracking sensor configured to detect the user's gaze, a liquid crystal panel, a first light-emitting element configured to emit light in a first wavelength range, and a second light-emitting element configured to emit light in a second wavelength range different from the first wavelength range, and an illumination device configured to illuminate the liquid crystal panel, a projection optical system positioned between the liquid crystal panel and the user's observation position and configured to project an image displayed on the liquid crystal panel toward the user, a scattering device configured to switch between a transparent state and a scattering state, and a control unit that controls the liquid crystal panel and the illumination device, and controls the scattering device based on the output from the eye-tracking sensor, wherein the control unit controls the system to display a color image in the first wavelength range on the liquid crystal panel in synchronization with the lighting up of the first light-emitting element, to display a color image in the second wavelength range on the liquid crystal panel in synchronization with the lighting up of the second light-emitting element, to set the scattering device to a transparent state, and to set the scattering device to a scattering state when a saccade is detected based on the output from the eye-tracking sensor. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a perspective view showing an example of the appearance of the head-mounted display 1. [Figure 2A] Figure 2A is a diagram illustrating one example configuration of a display device DSP. [Figure 2B] Figure 2B is a diagram illustrating another example configuration of a display device DSP. [Figure 3] Figure 3 is a plan view illustrating the configuration of a liquid crystal panel (PNL). [Figure 4] Figure 4 is a diagram illustrating the field sequential color scheme applied to a display device DSP. [Figure 5] Figure 5 shows an example of the control of the DSP display device shown in Figures 2A and 2B. [Figure 6A] Figure 6A is a diagram illustrating the focus state. [Figure 6B]Figure 6B is a diagram illustrating the defocused state. [Figure 7] Figure 7 shows another control example of the DSP display device shown in Figures 2A and 2B. [Figure 8A] Figure 8A is a diagram illustrating the congestion adjustment contradiction. [Figure 8B] Figure 8B is a diagram illustrating the mitigation of congestion adjustment contradictions. [Figure 9] Figure 9 illustrates another example configuration of a display device DSP. [Figure 10] Figure 10 shows an example of controlling the DSP display device shown in Figure 9. [Modes for carrying out the invention]

[0008] The embodiments will be described below with reference to the drawings. The disclosure is merely an example, and any modifications that a person skilled in the art could easily conceive of while maintaining the intent of the disclosure are naturally included within the scope of this disclosure. Furthermore, while drawings may schematically represent the width, thickness, shape, etc., of parts in a manner that is clearer than the actual embodiment, they are merely examples and do not limit the interpretation of this disclosure. In addition, in this specification and in each drawing, components that perform the same or similar functions as those described above in previously shown drawings are denoted by the same reference numerals, and redundant detailed explanations may be omitted as appropriate.

[0009] Furthermore, the drawings will include mutually orthogonal X, Y, and Z axes as needed to facilitate understanding. The direction along the X-axis will be referred to as the first direction X, the direction along the Y-axis as the second direction Y, and the direction along the Z-axis as the third direction Z. Viewing various elements parallel to the third direction Z is called a plan view. In addition, terms referring to the positional relationship between two or more constituent elements, such as above, above, between, and opposite, include not only cases where the two or more constituent elements of the object are in direct contact, but also cases where they are separated from each other by gaps or other constituent elements.

[0010] FIG. 1 is a perspective view showing an example of the appearance of the head-mounted display 1.

[0011] The head-mounted display 1 is, for example, worn on the head of the user USR. The head-mounted display 1 is used to provide, for example, virtual reality or augmented reality to the user USR.

[0012] The head-mounted display 1 includes a display device DSP1 for the left eye and a display device DSP2 for the right eye. The display device DSP1 is arranged to be positioned in front of the left eye of the user USR when the user USR wears the head-mounted display 1 on the head. The display device DSP2 is arranged to be positioned in front of the right eye of the user USR when the user USR wears the head-mounted display 1 on the head.

[0013] The display device DSP1 and the display device DSP2 have substantially the same configuration. Hereinafter, the display device DSP applicable to each of the display device DSP1 and the display device DSP2 will be described.

[0014] FIG. 2A is a diagram for explaining an example of the configuration of the display device DSP.

[0015] The display device DSP includes a lighting device IL, an optical sheet OS, a liquid crystal panel PNL, a projection optical system PO, a variable focus device VF, an eye tracking sensor ET, and a control unit CNT. The control unit CNT is configured to control the lighting device IL and the liquid crystal panel PNL. Further, the control unit CNT is configured to control the variable focus device VF based on the output from the eye tracking sensor ET.

[0016] The lighting device IL is arranged behind the liquid crystal panel PNL and is configured to illuminate the liquid crystal panel PNL. The lighting device IL includes a plurality of light-emitting elements LD and at least one light guide plate LG. The plurality of light-emitting elements LD includes, for example, a plurality of light-emitting elements LD1 configured to emit light in the first wavelength range, a plurality of light-emitting elements LD2 configured to emit light in the second wavelength range, and a plurality of light-emitting elements LD3 configured to emit light in the third wavelength range. The first wavelength range, the second wavelength range, and the third wavelength range are different from each other.

[0017] As an example of the light-emitting element LD, the light-emitting element LD1 is a light-emitting diode configured to emit light in the first wavelength range. The light-emitting element LD2 is a light-emitting diode configured to emit light in the second wavelength range. The light-emitting element LD3 is a light-emitting diode configured to emit light in the third wavelength range. Note that the light-emitting element LD is not limited to a light-emitting diode and may be a laser diode having higher directivity than a light-emitting diode. Also, a desired wavelength range of light may be obtained by combining the light-emitting element LD and a wavelength conversion element.

[0018] These light-emitting elements LD are driven by a light source driver DrL. The light source driver DrL is controlled by a control unit CNT.

[0019] The liquid crystal panel PNL includes a first substrate SUB1, a second substrate SUB2, a liquid crystal layer LC, a polarizing plate PL^1, and a polarizing plate PL^2. The liquid crystal layer LC is arranged between the first substrate SUB1 and the second substrate SUB2. The polarizing plate PL^1 is adhered to the first substrate SUB1. The polarizing plate PL^2 is adhered to the second substrate SUB2.

[0020] Such a liquid crystal panel PNL is driven by a panel driver DrP. The panel driver DrP is controlled by a control unit CNT.

[0021] A plurality of optical sheets OS are arranged betweenthe lighting device IL and the liquid crystal panel PNL. The optical sheet OS is, for example, a prism sheet or a diffusion sheet.

[0022] The projection optical system PO is positioned between the user's observation position O and the liquid crystal panel PNL, and is configured to project the image displayed on the liquid crystal panel PNL toward the user's eye E. The projection optical system PO is composed of various optical elements. For example, the projection optical system PO is an optical system sometimes called a pancake optical system, which has at least two reflective surfaces and has the function of folding the optical path twice.

[0023] A variable focus device VF is configured to change the focal length of an internal lens body LS. In the illustrated example, the variable focus device VF is positioned between the projection optical system PO and the user's observation position O. For example, the variable focus device VF may include a liquid crystal lens or a liquid lens with electrowetting applied as the lens body LS. A liquid crystal lens is configured to control the voltage applied to the liquid crystal layer to form a refractive index distribution in the liquid crystal layer. A liquid lens is configured to place a liquid on an electrode and control the voltage applied to the electrode to change the surface shape of the liquid.

[0024] Such a variable focus device (VF) is driven by a driver (DrV). The driver (DrV) is controlled by a control unit (CNT).

[0025] The eye-tracking sensor ET is configured to detect the user's gaze. The detection signal from the eye-tracking sensor ET is output to the control unit CNT.

[0026] Figure 2B is a diagram illustrating another example configuration of a display device DSP.

[0027] The configuration example shown in Figure 2B differs from the configuration example shown in Figure 2A in that the variable focus device VF is positioned between the liquid crystal panel PNL and the projection optical system PO. The other components are the same as those in the configuration example shown in Figure 2A, and their explanation is omitted.

[0028] Figure 3 is a plan view illustrating the configuration of a liquid crystal panel (PNL).

[0029] In a plan view, the first substrate SUB1 and the second substrate SUB2 are superimposed on each other and bonded together by a seal SE. The liquid crystal layer LC is sealed between the first substrate SUB1 and the second substrate SUB2 by a seal SE.

[0030] A liquid crystal panel (PNL) has a display area (DA) for displaying an image in a region where the liquid crystal layer (LC) is sealed. The display area (DA) has multiple pixels (PX) arranged in a matrix in a first direction (X) and a second direction (Y). Multiple scan lines (GL) each extend in the first direction (X) and are aligned in the second direction (Y). Multiple signal lines (SL) each extend in the second direction (Y) and are aligned in the first direction (X).

[0031] In the illustrated example, the IC chip CP and flexible printed circuit board FP for driving the liquid crystal panel PNL are mounted on the first board SUB1. The IC chip CP may also be mounted on the flexible printed circuit board FP. The panel driver DrP shown in Figures 2A and 2B includes a signal line driver that applies a voltage corresponding to the video signal to each of the signal lines SL, and a scan line driver that applies a voltage corresponding to the control signal to each of the scan lines GL. Such a panel driver DrP is, for example, integrated into the IC chip CP.

[0032] In the example shown in Figure 3, the first substrate SUB1 and the second substrate SUB2 are rectangular in shape when viewed from above, but they are not limited to this and may be polygons other than rectangular, or they may be circular or elliptical.

[0033] Figure 4 is a diagram illustrating the field sequential color scheme applied to a display device DSP.

[0034] The horizontal axis in the figure represents time. The frame period F for displaying a color image in the display area DA of the liquid crystal panel PNL includes a subframe period SF1 for displaying a color image in the first wavelength range, a subframe period SF2 for displaying a color image in the second wavelength range, and a subframe period SF3 for displaying a color image in the third wavelength range.

[0035] The subframe period SF1 includes a period T11 in which a video signal corresponding to a color image in the first wavelength range is written to all pixels PX of the liquid crystal panel PNL, and a period T12 in which the video signal written to the pixels PX is held. Multiple light-emitting elements LD1 can be lit at a predetermined duty cycle during period T12.

[0036] The subframe period SF2 includes a period T21 during which a video signal corresponding to a color image in the second wavelength range is written to all pixels PX of the liquid crystal panel PNL, and a period T22 during which the video signal written to the pixels PX is held. Multiple light-emitting elements LD2 can be lit at a predetermined duty cycle during period T22.

[0037] The subframe period SF3 includes a period T31 in which a video signal corresponding to a color image in the third wavelength range is written to all pixels PX of the liquid crystal panel PNL, and a period T32 in which the video signal written to the pixels PX is held. Multiple light-emitting elements LD3 can be lit at a predetermined duty cycle during period T32.

[0038] The control unit CNT shown in Figures 2A and 2B controls the light source driver DrL and the panel driver DrP. First, during subframe period SF1, it controls the display of a color image in the first wavelength range on the liquid crystal panel PNL in synchronization with the illumination of multiple light-emitting elements LD1. Subsequently, during subframe period SF2, the control unit CNT controls the display of a color image in the second wavelength range on the liquid crystal panel PNL in synchronization with the illumination of multiple light-emitting elements LD2. Then, during subframe period SF3, the control unit CNT controls the display of a color image in the third wavelength range on the liquid crystal panel PNL in synchronization with the illumination of multiple light-emitting elements LD3. This allows a color image to be provided to the user.

[0039] Next, we will explain an example of control when a saccade occurs while the user is observing a color image displayed on a DSP display device, referring to Figure 5.

[0040] First, the control unit CNT sets the focal length of the variable focus device VF to a first focal length and controls it to generate an image in focus (step ST11). The variable focus device VF is driven by the driver DrV controlled by the control unit CNT. As a result, as shown in Figure 6A, the focal point F1 is formed on the retina RE of the user's eye E. Therefore, the user can observe the image IM displayed on the liquid crystal panel PNL in focus.

[0041] Next, the control unit CNT determines whether or not a saccade has occurred based on the output from the eye-tracking sensor ET (step ST12). The control unit CNT can detect the user's gaze movement based on the output from the eye-tracking sensor ET. If the control unit CNT detects a saccade based on the output from the eye-tracking sensor ET (step ST12, YES), it controls the variable focus device VF to set its focal length to a second focal length different from the first focal length, thereby generating a defocused image (step ST13). The variable focus device VF is driven by a driver DrV controlled by the control unit CNT, which changes the shape of the built-in lens body LS. As a result, as shown in Figure 6B, the focal point F2 is not formed on the retina RE of the user's eye E, but in the illustrated example, it is formed in front of the retina RE. Therefore, the user can observe the image displayed on the liquid crystal panel PNL in a blurred state.

[0042] If the control unit CNT does not detect a saccade based on the output from the eye-tracking sensor ET (step ST12, NO), it controls the variable focus device VF to set its focal length to the first focal length and generate an image of the focused state (step ST11).

[0043] In this way, when saccades occur, the visibility of color separation (Color Brake Up) can be reduced by having the user observe a temporarily blurred image. This improves the display quality of images displayed using the field sequential color method.

[0044] Next, we will explain other control examples for when saccades occur while the user is observing a color image displayed on the DSP display device, referring to Figure 7. Here, we will explain the case where a stereoscopic image is displayed on the head-mounted display 1 shown in Figure 1.

[0045] The control unit CNT first sets the focal length of the variable focus device VF to the first focal length.

[0046] Next, the control unit CNT determines whether or not a vergence accommodation conflict (VAC) has occurred based on the output from the eye tracking sensor ET (step ST21). Specifically, the control unit CNT determines whether or not there is a mismatch between the depth position of the stereoscopic image displayed by the left eye display device DSP1 and the right eye display device DSP2, and the focal positions of the user's left and right eyes (i.e., the screen positions of the respective liquid crystal panels PNL of the display devices DSP1 and DSP2).

[0047] The case where a congestion adjustment contradiction occurs will be explained with reference to Figure 8A.

[0048] When a stereoscopic image VIM is displayed on the liquid crystal panel PNL, convergence occurs in the user's right eye E and left eye E as if observing the stereoscopic image VIM. On the other hand, the focal points of the user's right eye E and left eye E are fixed on the screen of the liquid crystal panel PNL. At this time, the distance from the user's right eye E and left eye E to the screen of the liquid crystal panel PNL is defined as the focal length FL, and the distance from the user's right eye E and left eye E to the stereoscopic image (virtual image) VIM is defined as the convergence distance VL. Such a mismatch between the focal length FL and the convergence distance VL causes discomfort to the user.

[0049] If the control unit CNT detects a vergence adjustment discrepancy based on the output from the eye-tracking sensor ET (step ST21, YES), it sets the focal length of the variable focus device VF to a third focal length different from the first focal length, and controls it so that the focal length FL of the user's eye becomes equivalent to the vergence distance VL (step ST22). At this time, as shown in Figure 8B, the focal points of the user's right eye E and left eye E are corrected to the position of the stereoscopic image VIM by the variable focus device VF.

[0050] Next, the control unit CNT determines whether or not a saccade has occurred based on the output from the eye-tracking sensor ET (step ST23). If the control unit CNT detects a saccade based on the output from the eye-tracking sensor ET (step ST23, YES), it controls the variable focus device VF to set its focal length to a second focal length different from the first and third focal lengths, thereby generating a defocused image (step ST24). This allows the user to observe the image displayed on the liquid crystal panel PNL in a blurred state.

[0051] If the control unit CNT does not detect a saccade based on the output from the eye-tracking sensor ET (step ST23, NO), it sets the focal length of the variable focus device VF to the third focal length (step ST22).

[0052] In this way, when a convergence adjustment discrepancy occurs, matching the focal length FL and convergence distance VL of the user's eye can alleviate user discomfort even when the user has been observing a stereoscopic image for an extended period. Furthermore, when observing a stereoscopic image, if saccades occur, temporarily showing the user a blurred image can reduce the visibility of color separation and improve display quality.

[0053] Figure 9 illustrates another example configuration of a display device DSP.

[0054] The configuration example shown in Figure 9 differs from the configuration example shown in Figure 2A in that, instead of the variable focus device VF, a scattering device DF configured to switch between a transparent state and a scattering state is used. The other components are the same as those in the configuration example shown in Figure 2A, and their explanation is omitted.

[0055] The scattering device DF is positioned between the projection optical system PO and the user's observation position O. For example, the scattering device DF is a liquid crystal device comprising a cholesteric liquid crystal or a polymer-dispersed liquid crystal. Such a liquid crystal device is configured to switch between a transparent state and a scattering state by controlling the orientation of liquid crystal molecules in response to a voltage applied to the liquid crystal layer.

[0056] Such a variable focus device (VF) is driven by a driver (DrD). The driver (DrD) is controlled by a control unit (CNT).

[0057] Next, we will explain an example of control when a saccade occurs while the user is observing a color image displayed on the DSP display device, referring to Figure 10.

[0058] First, the control unit CNT sets the scattering device DF to a transparent state (step ST31). The scattering device DF is driven by a driver DrD controlled by the control unit CNT. This allows the user to clearly observe the image displayed on the liquid crystal panel PNL.

[0059] Next, the control unit CNT determines whether or not a saccade has occurred based on the output from the eye-tracking sensor ET (step ST32). If the control unit CNT detects a saccade (step ST32, YES), it sets the scattering device DF to a scattering state (step ST33). The scattering device DF is driven by a driver DrD controlled by the control unit CNT, forming a scattering state. As a result, the user is unable to observe the image displayed on the liquid crystal panel PNL.

[0060] If the control unit CNT does not detect a saccade based on the output from the eye-tracking sensor ET (step ST32, NO), it sets the scattering device DF to a transparent state (step ST31).

[0061] In this way, when saccades occur, the image displayed on the liquid crystal panel PNL becomes temporarily invisible, thus reducing the visibility of color separation. This improves the display quality of images displayed using the field sequential color method.

[0062] In the above embodiment, for example, light-emitting element LD1 corresponds to a first light-emitting element, light-emitting element LD2 corresponds to a second light-emitting element, and light-emitting element LD3 corresponds to a third light-emitting element.

[0063] According to the embodiments described above, a display device capable of improving display quality can be provided.

[0064] While several embodiments of this disclosure have been described, these embodiments are presented as examples only and are not intended to limit the scope of the disclosure. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications are permitted without departing from the gist of the disclosure. These embodiments and their variations are included in the scope and gist of the disclosure, as well as in the disclosures described in the claims and their equivalents. [Explanation of Symbols]

[0065] DSP...Display device PNL...Liquid crystal panel IL...Illumination device CNT...Control unit VF…Variable Focus Device PO…Projection Optical System DF…Scattering device ET... Eye tracking sensor

Claims

1. An eye-tracking sensor configured to detect the user's gaze, LCD panel and An illumination device comprising a first light-emitting element configured to emit light in a first wavelength range, and a second light-emitting element configured to emit light in a second wavelength range different from the first wavelength range, and configured to illuminate the liquid crystal panel, A projection optical system is positioned between the liquid crystal panel and the user's observation position and configured to project the image displayed on the liquid crystal panel toward the user. A variable focus device configured to change the focal length, The system includes a control unit that controls the liquid crystal panel and the illumination device, and controls the variable focus device based on the output from the eye tracking sensor, The control unit, As described above, the system is controlled to display a color image in the first wavelength range on the liquid crystal panel in synchronization with the lighting of the first light-emitting element, and to display a color image in the second wavelength range on the liquid crystal panel in synchronization with the lighting of the second light-emitting element. The focal length of the variable focus device is set to a first focal length, and the device is controlled to generate the image in the focused state. When a saccade is detected based on the output from the eye-tracking sensor, the focal length of the variable focus device is set to a second focal length different from the first focal length, and the device is controlled to generate the image in a defocused state. Display device.

2. The variable focus device is positioned between the projection optical system and the user's observation position. The display device according to claim 1.

3. The variable focus device is positioned between the liquid crystal panel and the projection optical system. The display device according to claim 1.

4. The variable focus device comprises a liquid crystal lens or a liquid lens to which electrowetting is applied. The display device according to claim 1.

5. The control unit, When a convergence adjustment discrepancy is detected based on the output from the eye-tracking sensor, the focal length of the variable focus device is set to a third focal length different from the first and second focal lengths, and controlled so that the focal length of the user's eye becomes equal to the convergence distance. The display device according to claim 1.

6. An eye-tracking sensor configured to detect the user's gaze, LCD panel and An illumination device comprising a first light-emitting element configured to emit light in a first wavelength range, and a second light-emitting element configured to emit light in a second wavelength range different from the first wavelength range, and configured to illuminate the liquid crystal panel, A projection optical system is positioned between the liquid crystal panel and the user's observation position and configured to project the image displayed on the liquid crystal panel toward the user. A scattering device configured to switch between a transparent state and a scattering state, The system includes a control unit that controls the liquid crystal panel and the lighting device, and controls the scattering device based on the output from the eye-tracking sensor, The control unit, As described above, the system is controlled to display a color image in the first wavelength range on the liquid crystal panel in synchronization with the lighting of the first light-emitting element, and to display a color image in the second wavelength range on the liquid crystal panel in synchronization with the lighting of the second light-emitting element. Set the scattering device to a transparent state, When a saccade is detected based on the output from the eye-tracking sensor, the scattering device is controlled to be set to a scattering state. Display device.

7. The scattering device is a liquid crystal device comprising a cholesteric liquid crystal or a polymer-dispersed liquid crystal. The display device according to claim 6.

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