Patent Application
20240427166
This application claims the benefit of priority to Japanese Patent Application Number 2023-103653 filed on Jun. 23, 2023. The entire contents of the above-identified application are hereby incorporated by reference.
The disclosure relates to a display device.
Some information, such as confidential information or private information, is preferable only to be displayed under certain conditions. For example, JP 2001-255844 A discloses a system in which a user viewing a display using a pair of active glasses including lenses with shutters can view private data, while an unauthorized viewer without active glasses can view only private data masked by masking data.
However, such a system requires glasses including lenses with shutters. Thus, the glasses used by the user may become complex and expensive. In addition, control is required to synchronize the glasses with the display in order to open and close the shutters of the lens. Therefore, wireless or wired communication is required for the user's wearable items, which may impair ease-of-use for the user. Thus, a display device capable of ensuring confidentiality of a specific image without impairing ease-of-use for the user is desired.
According to one embodiment, a display device includes a display, a polarization module placed overlapping the display, the polarization module being configured to actively switch a polarization state between a first polarization state and a second polarization state, and a controller. The controller is configured to generate second image data from first image data, cause the display to display a first image based on the first image data and a second image based on the second image data in a time division manner, and switch the polarization state of the polarization module to the first polarization state in a case in which the first image is displayed and to the second polarization state in a case in which the second image is displayed in synchronization with a timing of the time division.
Further details will be described in the embodiments below.
The disclosure will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
(1) A display device according to an embodiment includes a display, a polarization module placed overlapping the display and configured to switch a polarization state between a plurality of polarization states, the polarization module being configured to actively switch a polarization state between a first polarization state and a second polarization state, and a controller. The controller is configured to generate second image data from first image data, cause the display to display a first image based on the first image data and a second image based on the second image data in a time division manner, and switch the polarization state of the polarization module to the first polarization state in a case in which the first image is displayed and to the second polarization state in a case in which the second image is displayed in synchronization with a timing of the time division.
A viewer uses polarized glasses that transmit an image displayed on the display and emitted in the first polarization state from the polarization module and do not transmit an image displayed on the display and emitted in the second polarization state from the polarization module. When wearing this polarized glasses, the viewer visually recognizes only the first image of the first image and the second image displayed on the display, which are switched in a time division manner. When not wearing the polarized glasses, the viewer visually recognizes both the first image and the second image displayed on the display, which are switched in a time division manner. When display switching between the first image and the second image is performed at such a speed that only the first image is not perceived and flicker is not perceived when the viewer is not wearing the polarized glasses, a composite image of the first image and the second image is perceived by the viewer not wearing the polarized glasses. Thus, the first image can be perceived only when wearing the polarized glasses, or only by a user wearing the polarized glasses. At this time, there is no need to change a polarization state of the polarized glasses in synchronization with the display on the display. Therefore, it is not necessary to control the polarized glasses by wireless communication or the like. In addition, the polarized glasses do not require a control mechanism and do not require a power supply. Therefore, the display device according to the present embodiment can ensure confidentiality of a specific image (first image) without impairing ease-of-use for users.
(2) In the display device according to (1), preferably, in the first polarization state, the first image is visually recognized by a viewer through polarized glasses worn by the viewer, and in the second polarization state, the second image is not visually recognized by the viewer through the polarized glasses. Thus, by using the polarized glasses, the confidentiality of the first image can be easily ensured as described above.
(3) In the display device according to (1) or (2), preferably, the generating second image data includes converting a gray scale of the image data into a gray scale with a predefined relationship. Thus, a composite image of the first image and the second image becomes an image having a gray scale according to the predefined relationship.
(4) In the display device according to any one of (1) to (3), preferably, the generating second image data includes converting a gray scale of a pixel belonging to at least one area of the image data into a different gray scale with a relationship predefined for each gray scale, and setting a gray scale of a pixel belonging to an area other than the at least one area to a gray scale predefined regardless of the gray scale. Thus, the areas in which a pattern of the first image may appear in the second image is limited to the at least one area and does not appear in other areas. Therefore, the pattern of the first image is less likely to be perceived even when blinking, a sudden shift of eye gaze, or the like occurs. Accordingly, the confidentiality of the first image can be further enhanced.
(5) In the display device according to any one of (1) to (4), preferably, the generating second image data includes dividing the image data into multiple areas, and changing a gray scale of a pixel belonging to each of the multiple areas to a gray scale with a relationship predefined for each of the multiple areas. Thus, a composite image of the first image and the second image may have different gray scales in different areas.
(6) In the display device according to any one of (1) to (5), preferably, the switching the polarization state of the polarization module includes dividing the polarization module into multiple segments along a scanning direction of the display, and switching the polarization states of the multiple segments in turn along the scanning direction with a time difference. Thus, compared to a case in which the polarization state of the polarization module is uniformly switched as a whole, the area on the display in which writing of the first image is not completed, which is included in a range where the polarization module is in the first polarization state, can be reduced. Therefore, compared to the case in which the polarization state of the polarization module is uniformly switched as a whole, differences in luminance (unevenness) of the first image that are visually recognized when a viewer is wearing polarized glasses are suppressed.
The display panel 12 includes multiple pixels. Preferably, the display panel 12 includes the multiple pixels arranged in a matrix. A configuration of the display panel 12 is not limited. The display panel 12 may have, for example, a structure in which a liquid crystal layer is sandwiched between a pair of substrates. In detail, the display panel 12 may have a structure in which a liquid crystal layer is sandwiched between a pair of substrates, one of which includes a pixel electrode and a common electrode formed thereon, and display is made by applying a voltage between the pixel electrode and the common electrode to apply a transverse electrical field (including a fringe electrical field) to the liquid crystal layer. As another example, the display panel 12 may have a structure in which a liquid crystal layer is sandwiched between a pair of substrates in which a pixel electrode is formed on one substrate and a common electrode is formed on the other substrate, and display is made by applying a voltage between the pixel electrode and the common electrode to apply a vertical electrical field to the liquid crystal layer. Examples of the transverse electrical field mode include FFS mode and IPS mode. Examples of the vertical electrical field mode include Vertical Alignment (VA) mode and Twisted Nematic (TN) mode.
A liquid crystal mode of the display panel 12 is not limited. The liquid crystal mode of the display panel 12 may be, for example, a mode in which black is displayed by aligning liquid crystal molecules in a liquid crystal layer 260 perpendicular to a substrate plane, or a mode in which black is displayed by aligning the liquid crystal molecules in the liquid crystal layer 260 in a direction parallel to the substrate plane or in a direction neither perpendicular nor parallel to the substrate plane. Examples of drive methods of the display panel 12 include a TFT method (active matrix method), a simple matrix method (passive matrix method), and a plasma address method.
The display panel 12 has, as an example, a structure in which the liquid crystal layer 260 is sandwiched between a pair of substrates 211 and 212, and they are sandwiched by insulating films 231 and 232. One of the substrates (the substrate 211) is provided with a pixel electrode and a common electrode (not illustrated). A black matrix layer (BM layer) 250 and color filter layers 240 (a blue color filter layer 240B, a red color filter layer 240R, and a green color filter layer 240G) regularly arranged between adjacent portions of the BM layer are formed in the substrate 211. The display panel 12 preferably includes the BM layer 250 arranged in a lattice pattern in a plan view.
The display panel 12 is connected to a display panel drive unit 16 that enables display. Under control of the display panel drive unit 16, the display panel 12 sequentially displays a main image (first image) and a sub image (second image), which will be described later, while switching them in a time division manner.
The backlight 13 includes one or more light sources (not illustrated). The light sources are light emitting diodes (LEDs) as an example.
The backlight 13 is connected to a backlight (BL) drive unit 17, and the BL drive unit 17 controls on/off of the backlight 13. The BL drive unit 17 may control on/off of the multiple light sources (not illustrated) individually or uniformly. When the display panel drive unit 16 sequentially displays a first image and a second image, which will be described later, on the display panel 12 in a time division manner, the BL drive unit 17 turns on an entire backlight in the display region 1100.
The polarization module 11 is a panel including an active retarder as an example. The polarization module 11 is switched to multiple polarization states by an Active Retarder (AR) panel drive unit 15. Under control of the AR panel drive unit 15, a polarization state of the polarization module 11 is switched between a first polarization state and a second polarization state in synchronization with switching between the main image (first image) and the sub image (second image) on the display panel 12. As an example, the polarization module 11 is in the first polarization state when the display panel 12 displays the first image, and the polarization module 11 is in the second polarization state when the display panel 12 displays the second image.
The viewer A views the display in the display region 1100 using removable polarized glasses 200. Note that the polarized glasses 200 do not have a shutter function. When the viewer A is wearing the polarized glasses 200, a display on the display panel 12 is given a polarization state by the polarization module 11 and reaches eyes of the viewer A through the polarized glasses 200. When the viewer A is not wearing the polarized glasses 200, a display on the display panel 12 is given a polarization state by the polarization module 11 and reaches the eyes of the viewer A without passing through the polarized glasses 200. “the viewer A captures a display on the display panel 12 in his/her field of view” is referred to as “visual recognition”, and “the viewer A grasps a meaning of the display captured in his/her field of view” is referred to as “perception”.
The polarized glasses 200 include polarizing films attached to both lenses. The polarizing film is preferably a circularly polarizing film. The polarizing film is not limited to a circularly polarizing film, and other types of polarizing films may be used.
The polarized glasses 200 transmit an image displayed on the display panel 12 for the first polarization state in the polarization module 11 and do not transmit an image displayed on the display panel 12 for the second polarization state in the polarization module 11. In other words, in the polarization module 11, the first polarization state is a polarization state in which the first image displayed on the display panel 12 is transmitted through the polarized glasses 200, and the second polarization state is a polarization state in which the second image displayed on the display panel 12 is not transmitted through the polarized glasses 200.
Thus, when the viewer A is not wearing the polarized glasses 200, the viewer A visually recognizes both the first image and the second image that are displayed on the display panel 12 while being switched in a time division manner. When the viewer A is wearing the polarized glasses 200, the viewer A visually recognizes only the first image of the first image and the second image that are displayed on the display panel 12 while being switched in a time division manner. In the display system 100, there is no need to change a polarization state of the polarized glasses 200 in synchronization with the display on the display panel 12. Therefore, it is not necessary to control the polarized glasses 200 by wireless communication or the like. In addition, the polarized glasses 200 do not require a control mechanism and do not require a power supply.
The polarization module 11 includes an optical layered body 110 and a retarder 120. The optical layered body 110 includes a pair of substrates 111 and 112, a pair of electrodes 121 and 122, a liquid crystal layer 160, and columnar spacers 151 and 152. To be more specific, the optical layered body 110 includes, from the observation face side, the first substrate 111, the first electrode 121, the liquid crystal layer 160, the second electrode 122, and the second substrate 112. Light blocking layers 170 for limitedly blocking light to the columnar spacers 151 and 152 are provided between the first substrate 111 and the first electrode 121, and a flattening film 180 is provided between the light blocking layers 170 and the first electrode 121. Between the electrodes 121 and 122 and the liquid crystal layer 160, insulating films 131 and 132 and alignment films 141 and 142 are provided in order from these electrode sides, respectively.
The second spacers 152 are provided to control a thickness of the liquid crystal layer 160. The first spacers 151 are placed in a floating island shape. Thus, the polarization module 11 can be given resistance to surface pressing.
When the first spacers 151 are placed in a floating island shape, it means that the first spacers 151 are placed in a floating island shape in the liquid crystal layer 160. To be specific, this means that the liquid crystal layer 160 is present between the first spacers 151 and the first substrate 111 or the second substrate 112 in a cross-sectional view. That is, a height of the first spacers 151 is smaller than a thickness of the liquid crystal layer 160. On the other hand, a height of the second spacers 152 is equal to the thickness of the liquid crystal layer 160.
The height of the first spacers 151 is smaller than the thickness of the liquid crystal layer 160. That is, when the thickness of the liquid crystal layer 160 is 100%, the height of the first spacers 151 may be a value less than 100%, for example, from 5 to 95%.
The first spacers 151 and the second spacers 152 are formed from, for example, a light transmitting resin material. By forming multiple types of columnar spacers having different heights on one substrate (e.g., the first substrate 111) side, the first spacers 151 and the second spacers 152 can be formed. To be specific, for example, after forming columnar spacers having different heights on the first substrate 111 side, the second substrate 112 is bonded to the first substrate 111 with a liquid crystal material sandwiched therebetween, so that the columnar spacers having a height lower than the thickness of the liquid crystal layer 160 formed from the liquid crystal material become the first spacers 151 and other columnar spacers become the second spacers 152.
The optical layered body 110 includes light blocking portions (also referred to as the light blocking layers) 170 as an example of a light blocking means for limitedly blocking light to the first spacers 151 and the second spacers 152. The light blocking portions 170 are placed at positions overlapping the columnar spacers. By providing such light blocking means, deterioration in display performance due to retardation shift around the columnar spacers can be sufficiently suppressed.
When the light blocking portion 170 is placed at a position overlapping the columnar spacer, it means that 80% to 100% of an area of the columnar spacer overlaps the light blocking layer in a plan view. Preferably, 85% to 100%, more preferably 90% to 100% of the area of the columnar spacer overlaps the light blocking layer.
The light blocking portions 170 are formed from a light blocking material. Examples of the light blocking material include a metal black matrix (also referred to as a metal BM) made of a metal and a resin black matrix (also referred to as a resin BM) made of a resin material. Examples of the metal BM include metal films containing aluminum, molybdenum, chromium, titanium, or an alloy thereof. Examples of the resin BM include black resists, among which black photosensitive resins are preferable. Specific examples thereof include a black photosensitive acrylic resin. The light blocking portion 170 may be a single-layer film or a multilayer film.
A light transmittance of the light blocking portion 170 is preferably, for example, from 0 to 1%. A thickness of the light blocking portion 170 is not limited. The thickness of the light blocking portion 170 is preferably, for example, from 10 nm to 2 μm. The thickness of the light blocking portion 170 is more preferably from 50 nm to 1.5 μm.
In order to obtain the unit U, first, a large number of first spacers 151 are regularly arranged such that a distance (clearance) between a first spacer 151 and another first spacer 151 adjacent thereto in the horizontal direction is set to 37.7 μm, a distance (clearance) between the first spacer 151 and another first spacer 151 adjacent thereto in the vertical direction is set to 217.6 μm. Thereafter, third, fourth, and fifth first spacers 151 from the left in the second row from the bottom (three spacers in total) are removed, and one second spacer 152 (second spacer 152A) is placed at the center position of the area from which the first spacers 151 have been removed. A distance (clearance) between each of first spacers 151a and 151b on both left and right sides of the removed first spacers 151 (three spacers) and the second spacer 152A placed this time is 127.75 μm. FIG. X on the right side of
Further, a third first spacer 151 (one spacer) from the right in a fourth row from the bottom is also removed, and one second spacer 152 (second spacer 152B) is placed at the center position of the area from which the first spacer 151 has been removed. A distance (clearance) between each of first spacers 151c and 151d on both left and right sides of the removed first spacer 151 (one spacer) and the second spacer 152B placed this time is 50.05 μm.
The flattening film (also referred to as a flattening layer) 180 for flattening is provided between the light blocking layers 170 and the first electrode 121. The flattening film 180 is preferably, for example, an organic insulating film. As the organic insulating film, for example, an organic film having a low relative dielectric constant (relative dielectric constant C=2 to 5) such as a photosensitive resin or a layered film thereof can be used. Specific examples of the organic insulating film include organic films made of an acrylic resin, a polyimide resin, and a novolac resin, and layered bodies thereof. A thickness of the flattening film 180 is not limited, and is preferably, for example, from 10 nm to 5 μm. The thickness of the flattening film 180 is more preferably from 30 nm to 3 μm.
The first substrate 111 and the second substrate 112 are preferably transparent substrates. The transparent substrate may be any substrate that transmits visible light. Examples of the transparent substrate include glass substrates and plastic substrates.
The first electrode 121 and the second electrode 122 are preferably transparent electrodes. The transparent electrode can be formed using, for example, a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or tin oxide (SnO), or an alloy thereof.
The first electrode 121 and the second electrode 122 are electrodes placed planarly on entire surfaces of the corresponding substrates, that is, so-called solid electrodes, but may be patterned.
The polarization module 11 is driven in ECB mode as an example. The ECB mode is a mode in which double refraction of the liquid crystal layer 160 is controlled by voltage application, and is classified into horizontal alignment, vertical alignment (VA), and HAN depending on an initial alignment state of liquid crystal molecules. In these modes, a voltage is applied to the liquid crystal layer in the vertical direction. Note that a Fringe Field Switching (FFS) mode, In-Plane Switching (IPS) mode, and the like in which a voltage is applied in a lateral direction can also be regarded as one type of the ECB mode in a sense that the double refraction of the liquid crystal layer is controlled by voltage application. The polarization module 11 according to the embodiment uses a positive liquid crystal and employs a vertical electrical field ECB mode in which initial alignment of liquid crystal molecules is in a horizontal alignment state.
The liquid crystal layer 160 is composed of a liquid crystal material containing liquid crystal molecules 1601. By applying a voltage to the liquid crystal layer 160 and changing the alignment state of the liquid crystal molecules 1601 in accordance with the applied voltage, an amount of light transmission can be controlled. Note that a state in which the voltage applied to the liquid crystal layer 160 is less than a threshold value is referred to as a no voltage applied state.
The liquid crystal molecules 1601 may preferably have a positive value of anisotropy of dielectric constant (Ac) defined by the following equation.
The liquid crystal molecules 1601 may have a negative value of anisotropy of dielectric constant (Ac). In the polarization module 11 according to the embodiment, liquid crystal molecules having a positive value of anisotropy of dielectric constant (Ac) are used. Note that the liquid crystal molecules having positive anisotropy of dielectric constant is also referred to as positive liquid crystal, and the liquid crystal molecules having negative anisotropy of dielectric constant is also referred to as negative liquid crystal. The major axis direction of the liquid crystal molecules is a direction of a slow axis.
The liquid crystal molecules 1601 also preferably satisfy Equation (1) below.
(In the equation, K11 represents a splay elastic constant (pN) of the liquid crystal molecules 1601. γ1 represents a rotational viscosity coefficient (mPa·s) of the liquid crystal material. Δε represents anisotropy of dielectric constant of the liquid crystal molecules 1601)
That is, it is preferable to select, as the liquid crystal molecules 1601, liquid crystal molecules having anisotropy of dielectric constant Δε that satisfies the relationship in Equation (1). Thus, in particular, a response time from voltage on to voltage off can be shortened, and the polarization module 11 that can follow ultra-high-speed image switching can be obtained.
The anisotropy of dielectric constant Δε of the liquid crystal molecules 1601 may be within a range that satisfies Equation (1) above, and is preferably 0.1 or more from the viewpoint of further enabling high-speed response. More preferably, the anisotropy of dielectric constant Δε is 0.11 or more. From the viewpoint of cell thickness control in consideration of actual production, the anisotropy of dielectric constant Δε is preferably 0.22 or less. More preferably, the anisotropy of dielectric constant Δε is 0.2 or less.
The liquid crystal molecules 1601 preferably have a splay elastic constant K11 of 5 pN or more from the viewpoint of further enabling high-speed response. More preferably, the splay elastic constant K11 is 10 pN or more. From the same viewpoint, the splay elastic constant K11 is preferably 30 pN or less. More preferably, the splay elastic constant K11 is 20 pN or less. The most preferable range of the splay elastic constant K11 is from 10 to 20 pN.
From the viewpoint of further enabling high-speed response, the liquid crystal material constituting the liquid crystal layer 160 preferably has a rotational viscosity coefficient γ1 of 100 mPa·s or less. More preferably, the rotational viscosity coefficient γ1 is 60 mPa·s or less. From the same viewpoint, the rotational viscosity coefficient γ1 is preferably 20 mPa·s or more. More preferably, the rotational viscosity coefficient γ1 is 30 mPa·s or more. The most preferable range of the rotational viscosity coefficient γ1 is from 30 to 60 mPa·s.
A thickness of the liquid crystal layer 160 (cell thickness) is preferably from 100 nm to 10 μm. More preferably, the cell thickness is from 500 nm to 5 μm, and still more preferably from 1 μm to 3 μm.
The alignment films 141 and 142 are placed on both sides (the observation face side and the back face side) of the liquid crystal layer 160, respectively. Further, an insulating film may be provided between the alignment film and the electrode. In the polarization module 11 according to the embodiment, the insulating film 131 and the alignment film 141 are provided between the first electrode 121 and the liquid crystal layer 160 in the order from the electrode side, and the insulating film 132 and the alignment film 142 are provided between the second electrode 122 and the liquid crystal layer 160 in the order from the electrode side.
The alignment films 141 and 142 have a function of controlling the alignment of the liquid crystal molecules contained in the liquid crystal layer 160. When the voltage applied to the liquid crystal layer 160 is less than the threshold voltage (including no voltage application), the alignment of the liquid crystal molecules in the liquid crystal layer 160 is controlled mainly by action of the alignment films. As materials for the alignment films 141 and 142, materials commonly used in the field of liquid crystal display panels can be used, such as polymers having polyimide in a main chain, polymers having polyamic acid in a main chain, and polymers having polysiloxane in a main chain.
The insulating films 131 and 132 are preferably inorganic insulating films, for example. Examples of the inorganic insulating film include inorganic films (relative dielectric constant c=5 to 7) such as silicon nitride (SiNx) and silicon oxide (SiO2), and a layered film thereof. A thickness of each insulating film is not limited, and is preferably, for example, from 10 nm to 500 nm. More preferably, the thickness of each insulating film is from 30 nm to 300 nm.
The retarder 120 to be combined with the optical layered body 110 may have an in-plane retardation Ro or a thickness direction retardation Rth. The retarder 120 is preferably a uniaxial retarder having an in-plane retardation Ro. An absolute value |Ro| of the in-plane retardation Ro is preferably 50 nm or more. More preferably, the absolute value |Ro| is 80 nm or more, and still more preferably 100 nm or more. The absolute value |Ro| is preferably 500 nm or less. More preferably, the absolute value |Ro| is 400 nm or less, and still more preferably 350 nm or less.
As the retarder 120, a A/4 retarder (also referred to as a A/4 plate) or a A/2 retarder (also referred to as a A/2 plate) is suitable. In the polarization module 11 according to the embodiment, a A/4 plate is used as the retarder 120, as will be described later.
The retarder 120 may have a single layer structure or a layered structure of two or more layers. When combining the display panel 12 and the polarization module 11, the retarder 120 is preferably placed closer to the display panel 12.
A thickness of the retarder 120 is not limited, and is preferably, for example, from 10 μm to 500 μm. More preferably, the thickness is from 50 μm to 200 μm.
A material of the retarder 120 is not limited, and, for example, a drawn polymer film, a liquid crystal material with fixed alignment, a thin plate made of an inorganic material, or the like can be used. A method of forming the retarder 120 is not limited.
When the retarder 120 is formed from a polymer film, for example, the forming method may be a solvent casting method, a melt extrusion method, or the like. The method of forming the retarder 120 may be a co-extrusion method to simultaneously form multiple retarders 120. As long as a desired retardation is exhibited by the retarder 120, the retarder 120 may or may not be drawn. The drawing method is not limited, and examples thereof include an inter-roll pulling drawing method, an inter-roll compression drawing method, a tenter transverse uniaxial drawing method, an oblique drawing method, a longitudinal and lateral biaxial drawing method, and a special drawing method in which drawing is performed under action of shrinkage force of a heat-shrinkable film.
When the retarder 120 is formed from a liquid crystal material, examples of the formation method include a method of applying the liquid crystal material on a base film subjected to an alignment treatment and fixing the alignment. As long as a desired retardation is exhibited by the retarder 120, the formation method may be a method in which a substrate film is not subjected to a special alignment treatment, a method in which alignment is fixed and then the base film is peeled off and transferred to another film, or the like. Further, the retarder 120 may be formed by a method in which the alignment of the liquid crystal material is not fixed. When the retarder 120 is formed from a non-liquid crystal material, the formation method may be the same as when formed from a liquid crystal material.
As the retarder 120, a drawn film containing a material having positive intrinsic birefringence (intrinsic refractive index anisotropy) as a component or the like can be used as appropriate. Examples of the material having positive intrinsic birefringence include polycarbonate, polysulfone, polyethersulfone, polyethylene terephthalate, polyethylene, polyvinyl alcohol, norbornene, triacetylcellulose, diacetylcellulose, and a cycloolefin polymer.
A method of manufacturing the optical layered body 110 and a method of manufacturing the polarization module 11 using the optical layered body 110 and the retarder 120 are not limited, and methods commonly used in the field of liquid crystal panels can be used.
The AR panel drive unit 15 controls voltage application to the liquid crystal layer 160 under the control of the controller 20 to be described later. Thus, the polarization module 11 can be switched to multiple polarization states.
In the polarization module 11 according to the embodiment, the optical layered body 110 performs retardation switching between λ/2 and 0. In the polarization module 11 according to the embodiment, a λ/4 plate is used as the retarder 120, and the optical layered body 110 and the retarder 120 are arranged so that a slow axis of the optical layered body 110 and a slow axis of the retarder 120 are orthogonal to each other. Thus, the polarization module 11 according to the embodiment can perform retardation switching between +λ/4 and −λ/4.
In this case, one of the polarizing films having a −λ/4 retardation and a +λ/4 retardation is attached to the polarized glasses 200. As an example, assuming that the +λ/4 phase in the polarization module 11 is a first polarization state and the −λ/4 phase is a second polarization state, a polarizing film having a +λ/4 retardation is attached to the polarized glasses 200. Thus, when the polarization module 11 is in the first state (the retardation switching state is +λ/4), the retardation becomes+λ/2 (=(+λ/4)+(+λ/4)), and the polarized glasses 200 transmit polarized light. When the polarization module 11 is in the second state (the retardation switching state is −λ/4), the retardation becomes 0 (=(−λ/4)+(+λ/4)), and the polarized glasses 200 do not transmit polarized light. When the first polarization state and the second polarization state of the polarization module 11 are reversed in the retardation switching between +λ/4 and −λ/4, a polarizing film having a −λ/4 retardation may be attached to the polarized glasses 200.
The controller 20 includes a timing controller 21, a memory 22, an image generation unit 23, and a data selector 25. The memory 22 includes a storage area 221 for storing first image data D1 input as an image signal Sg1 from the outside.
The image generation unit 23 generates second image data D2 from the first image data D1 stored in the memory 22. In order to generate the second image data D2 from the first image data D1, the image generation unit 23 uses a lookup table (LUT) 24 described later. The image generation unit 23 may be configured of an electric circuit or may be achieved by software control.
The timing controller 21 inputs a synchronization signal Sg2 to the memory 22, the data selector 25, and the AR panel drive unit 15 at a predefined timing. The predefined timing is, as an example, every frame of the first image data D1 contained in the signal Sg1.
The data selector 25 obtains the first image data D1 stored in the memory 22 and the second image data D2 generated in the image generation unit 23. The data selector 25 alternately outputs the first image data D1 and the second image data D2 to the display panel drive unit 16 at the timing according to the synchronization signal Sg2. Thus, the first image based on the first image data D1 and the second image based on the second image data D2 are alternately displayed on the display panel 12 in a time division manner at the timing based on the synchronization signal Sg2. The timing based on the synchronization signal Sg2 is, as an example, every frame. The display switching between the first image and the second image is not limited to every frame and may be switched at such a speed that the first image and the second image are not perceived individually when the viewer A is not wearing the polarized glasses 200 and does not perceive any flicker. The display switching between the first image and the second image is preferably performed at 180 Hz or more.
The AR panel drive unit 15 switches the polarization state of the polarization module 11 alternately between the first polarization state and the second polarization state in synchronization with switching between the first image and the second image on the display panel 12 at a timing based on the synchronization signal Sg2. As an example, the AR panel drive unit 15 switches the polarization state of the polarization module 11 between the first polarization state and the second polarization state every frame. That is, the polarization module 11 switches to the first polarization state at the timing when the first image is displayed on the display panel 12, and the polarization module 11 switches to the second polarization state at the timing when the second image is displayed on the display panel 12.
Generating the second image data D2 from the first image data D1 in the image generation unit 23 is generating the second image data D2, which is an image that is combined with the first image to make the first image imperceptible, by converting at least part of the first image data D1. Preferably, the second image data D2 may be an image that, when combined with the first image, renders the first image imperceptible in a state in which responsiveness of the display panel 12 is affected by luminance. In other words, the second image data D2 is an image that is combined with the first image displayed on the display panel 12 and visually recognized by the viewer A, so that the viewer A does not perceive the first image. The image generation unit 23 converts pixel values of predefined pixels among the pixels indicated in the first image data D1 in accordance with a predefined relationship. The predefined pixels are, for example, all pixels of the first image. The second image is, as an example, an image in which all pixels have a specific pixel value (e.g., a gray image) by being combined with the first image.
The first image 301 and the second image 302 illustrated in
The LUT 24 defines corresponding relationship between the pixel values of the first image data D1 and the second image data D2. The image generation unit 23 generates the second image data D2 by converting the pixel values of pixels of the first image data D1 into pixel values defined in the LUT 24. Preferably, the corresponding relationship of pixel values between the first image data D1 and the second image data D2 is determined by measuring combination of the gray scales of the first image data D1 and the second image data D2 displayed with the display settings of the display panel 12, such as responsiveness of the display panel 12, responsiveness of the polarization module 11, and overdrive and gamma value as the same settings as the display device 10, using a luminance meter so that the integrated luminance for each combination is constant. As another example, the corresponding relationship of pixel values between the first image data D1 and the second image data D2 may be defined by a function or an arithmetic equation. As another example, the corresponding relationship of pixel values between the first image data D1 and the second image data D2 may be machine learned by deep learning or the like, so that the image generation unit 23 uses the first image data D1 as input values and outputs the second image data D2.
Brightness (luminance) at which the viewer A visually recognizes each pixel on the display panel 12 is an amount of light that the viewer A receives from each pixel during a predetermined period. Therefore, the luminance at which the viewer A visually recognizes each pixel on the display panel 12 is an integrated value of the luminance change of each pixel during a predetermined period. An integrated value of luminance in a pixel during a predetermined period is also referred to as “integrated luminance” in distinction from instantaneous luminance in this pixel. The luminance of each pixel that the viewer A visually recognizes when not wearing the polarized glasses 200 by displaying the first image and the second image alternately on the display panel 12 in a time division manner is the integrated luminance of each pixel in the first image and the second image.
In
Here, attention is paid to a pixel having a gray scale of 0 as a pixel value in the first image and a pixel having a gray scale of 255 as a pixel value in the first image. The former pixel is referred to as a first target pixel, and the latter pixel is referred to as a second target pixel. The first target pixel has a gray scale of 255 as a pixel value in the second image, and the second target pixel has a gray scale of 0 as a pixel value in the second image. A curve L1 in
Referring to
Referring to
The luminance that the viewer A visually recognizes when not wearing the polarized glasses 200 for the first target pixel is an integrated value of the curve L1. The integrated value of the curve L1 is a hatched area S1 in
For the first target pixel, when the luminance of the first target pixel in the second image is a gray scale of 255, the luminance that the viewer A visually recognizes when not wearing the polarized glasses 200 is the maximum. For the second target pixel, when the luminance of the second target pixel in the second image is a gray scale of 0, the luminance that the viewer A visually recognizes when not wearing the polarized glasses 200 is the minimum.
Since the pixel values of the first image data D1 and the second image data D2 for each pixel have the corresponding relationship defined in the LUT 24 in
What defines the relationship between the pixel values of the first image data D1 and the pixel values of the second image data D2 is not limited to the table format as shown in
The LUT 24 does not need to define the correspondence of pixel values of the second image data D2 for all pixel values of the first image data D1, but only needs to define for at least some of the pixel values. For example, the LUT 24 may define the correspondence of the second image data D2 for multiple pixel values that are less than all of the first image data D1, and other pixel values may be obtained by linear interpolation or the like. Furthermore, the LUT 24 may be prepared for each temperature, and the LUT 24 corresponding to the temperature on the display panel 12 may be used. Alternatively, LUTs 24 for multiple specific temperatures may be prepared and used by linear interpolation corresponding to the temperature on the display panel 12.
The image generation unit 23 generates the second image data D2 from the first image data D1 stored in the memory 22 (step S101) and inputs the second image data D2 to the data selector 25. The timing controller 21 outputs the synchronization signal Sg2 for each frame of the first image data D1 contained in the signal Sg1.
At the timing indicated by the synchronization signal Sg2, the data selector 25 outputs a control signal to the display panel drive unit 16 to display the first image from the first image data D1 stored in the memory 22 on the display panel 12 (step S103). At the same timing indicated by the synchronization signal Sg2, the AR panel drive unit 15 sets the polarization module 11 to the first polarization state (step S105).
Upon receiving the synchronization signal Sg2 indicating the timing of the next frame from the timing controller 21 (YES in step S107), the data selector 25 outputs a control signal to the display panel drive unit 16 to display the second image from the second image data D2 on the display panel 12 (step S109). At the same timing indicated by the synchronization signal Sg2, the AR panel drive unit 15 sets the polarization module 11 to the second polarization state (step S111).
When the synchronization signal Sg2 indicating the timing of the next frame is received from the timing controller 21 (YES in step S113), the processes from step S103 are repeated. That is, until the synchronization signal Sg2 indicating the timing of the next frame is no longer received from the timing controller 21 (NO in step S107 or NO in step S113), the data selector 25 outputs a control signal to the display panel drive unit 16 to display the first image and the second image alternately on the display panel 12 in synchronization with the synchronization signal Sg2 from the timing controller 21. The AR panel drive unit 15 alternately switches the polarization state of the polarization module 11 between the first polarization state and the second polarization state.
In
When the viewer A is wearing the polarized glasses 200 (
When the viewer A is not wearing the polarized glasses 200 (
By using the display system 100 according to the embodiment, the viewer A can perceive the first image only when wearing the polarized glasses 200. When not wearing the polarized glasses 200, the viewer A also visually recognizes an image (second image) different from the first image, and thus cannot perceive the first image. Thus, the first image can be perceived only by a specific user who can wear the polarized glasses 200. Alternatively, the first image can be perceived only at specific timing when the polarized glasses 200 can be worn. For example, by making confidential information or private information the first image, confidentiality of the information can be ensured. Thus, in the display system 100 according to the present embodiment, the confidentiality of a specific image can be ensured only by the presence or absence of polarized glasses 200 without impairing ease-of-use for users.
In the display system 100 according to the second embodiment, the polarization module 11 is divided into multiple segments in the direction D. In the example in
An image is written on the display panel 12 by sequentially applying voltages based on the image data to the display panel 12 from the upper end 12U to the lower end 12D in one frame time T by the display panel drive unit 16. A writing direction E indicated by an arrow in
In this case, when the AR panel drive unit 15 switches the polarization state of the entire polarization module 11 to the first polarization state at times t0 and t2 based on the synchronization signal Sg2 from the timing controller 21, the viewer A wearing the polarized glasses 200 visually recognizes a screen in which the first image 301 is displayed only at the upper end 12U of the display panel 12, and the second image 302 is displayed below the upper end 12U. That is, when the entire polarization module 11 is switched to the first polarization state at the same timing as the writing of the first image 301 starts, the first image 301 may not be visually recognized in proper way.
In this regard, the AR panel drive unit 15 according to the second embodiment sequentially switches the polarization state of the upper segment 11A and the polarization state of the lower segment 11B in the direction D with a time difference, based on the synchronization signal Sg2 from the timing controller 21. In this example, the AR panel drive unit 15 switches the polarization state by shifting the lower segment 11B from the upper segment 11A by half the frame (T/2).
Accordingly, the upper segment 11A becomes the first polarization state at the timing at which the first image 301 is displayed at least at the upper end 12U of the display panel 12, and the first image 301 is visually recognized at least at the upper end 12U when the viewer A is wearing the polarized glasses 200. On the other hand, since the lower segment 11B is not switched to the first polarization state but is in the second polarization state at that timing, when the viewer A is wearing the polarized glasses 200, visual recognition of the second image 302 that is still displayed is reduced.
Preferably, the AR panel drive unit 15 switches the polarization state of the upper segment 11A after a predetermined time from the start of writing an image onto the display panel 12. By switching the polarization state of the upper segment 11A after a predetermined time from the start of writing an image onto the display panel 12, the area in which writing is completed on the display panel 12 at the time when the upper segment 11A is switched to the first polarization state increases.
As an example, the AR panel drive unit 15 switches the upper segment 11A to the first polarization state after a time difference dt1 (dt1<T) from times t0 and t2. The AR panel drive unit 15 switches the lower segment 11B to the first polarization state after a time difference dt2 (dt2=dt1+T/2) from times t0 and t2 by shifting from the upper segment 11A by half a frame (T/2). The AR panel drive unit 15 switches the upper segment 11A to the second polarization state after the time difference dt1 (dt1<T) from times t1 and t3. The AR panel drive unit 15 switches the lower segment 11B to the second polarization state after the time difference dt2 (dt2=dt1+T/2) from times t1 and t3 by shifting from the upper segment 11A by half a frame (T/2).
When the second target pixel is located near the upper end 12U of the display panel 12 (
In the example in
When the second target pixel is located near the lower end 12D of the display panel 12 (
In the example in
By dividing the polarization module 11 into the multiple segments in the direction D and sequentially switching the polarization state of the segments with a time difference, compared to a case in which the polarization state of an entire polarization module 11 is uniformly switched at the start of each frame, the area on the display panel 12 in which writing of the first image 301 is not completed, which is included in a range where the polarization module 11 is in the first polarization state, can be reduced. Therefore, compared to the case in which the polarization state of the entire polarization module 11 is uniformly switched at the start of each frame, differences in luminance (unevenness) of the first image 301 that are visually recognized when the viewer A is wearing the polarized glasses 200 are suppressed. As a result, display quality when the viewer A is wearing the polarized glasses 200 is improved.
The timing difference in switching the polarization states between the upper segment 11A and the lower segment 11B is not limited to one half of one frame time (T/2) and may be any other time difference. The timing difference in switching the polarization states between the upper segment 11A and the lower segment 11B may be set in accordance with the writing response of the display panel 12 or the like or may be set in accordance with the response speed of the polarization module 11.
The control to change the timings of switching the polarization states of the upper segment 11A and the lower segment 11B may include control to switch the polarization states of the upper segment 11A and the lower segment 11B at the same timing, that is, to uniformly switch the polarization state of the entire polarization module 11. That is, the AR panel drive unit 15 may switch the polarization states of the upper segment 11A and the lower segment 11B at the same time. The division of the polarization module 11 in the direction D is not limited to two divisions. The polarization module 11 may be divided into three or more parts in the direction D.
Generating the second image data D2 from the first image data D1 in the image generation unit 23 may be, as another example, converting the pixel values of the pixels belonging to at least some areas of the first image data D1 in accordance with the LUT 24 and setting the pixel values of the pixels belonging to areas other than the at least some areas to a specific gray scale value predefined regardless of the pixel values.
The image generation unit 23 makes pixels in areas other than the areas 301a, 301b, 301c, and 301d to a predefined gray scale such as black (a gray scale of 0). The color after conversion is not limited to black (a gray scale of 0) and may be any other gray scale. For example, different gray scales may be designated for RGB.
In the display system 100 according to the first embodiment, all the pixels of the first image data D1 are converted into the second image data D2 having a specific relationship, so that the pattern of the first image 301 may appear in the second image 302. Thus, when the viewer A is not wearing the polarized glasses 200, the pattern of the first image 301 may be instantaneously perceived by the eye tracking integration effect due to blinking, a sudden shift of eye gaze, or the like.
On the other hand, in the display system 100 according to the third embodiment, the pattern of the first image 301 may appear in a second image 304 only in some areas and does not appear in other areas. Therefore, the pattern of the first image 301 is less likely to be perceived even when blinking, a sudden shift of eye gaze, or the like occurs. Accordingly, confidentiality of the first image 301 can be further enhanced.
In the display system 100 according to the third embodiment, when the viewer A is not wearing the polarized glasses 200, a fourth image 305, which is a composite image of the first image 301 and the second image 304, is perceived.
In
When the viewer A is not wearing the polarized glasses 200, the fourth image 305, which is a composite of the first image 301 and the second image 304, is perceived. In the areas 301a, 301b, 301c, and 301d, the sums of the pixel values of the respective pixels in the first image 301 and the second image 304 are equal. Areas other than the areas 301a, 301b, 301c, and 301d are monochromatic areas in which the pixel values of the second image 304 are black (a gray scale of 0) or the like. Therefore, the fourth image 305 is an image that includes the pattern of the first image 301 in the areas other than the areas 301a, 301b, 301c, and 301d, but has a specific gray scale as a whole, for example, a gray image, in the areas 301a, 301b, 301c, and 301d. Accordingly, when the viewer A is not wearing the polarized glasses 200, the first image 301 is not perceived. Thus, the confidentiality of the first image 301 can be ensured.
The areas 301a, 301b, 301c, and 301d may have any size or shape as long as the pattern of the first image 301 is not easily perceived even when a blink, a sudden shift of eye gaze, or the like occurs. Preferably, the areas 301a, 301b, 301c, and 301d are smaller than the first image 301, and are discontinuous with each other. In the example in
Sizes of the areas 301a, 301b, 301c, and 301d do not necessarily have to be constant (identical). As another example, the size of each of the areas 301a, 301b, 301c, and 301d may be determined in accordance with content included in the first image 301. As an example, when the first image 301 includes characters, a size may correspond to a font size. In this case, for example, the image generation unit 23 may identify the font size from information contained in the image signal Sg1, and may determine the size of each of the areas 301a, 301b, 301c, and 301d based on a pre-stored corresponding relationship between the font size and the area size.
Generating the second image data D2 from the first image data D1 in the image generation unit 23 may be, as another example, dividing the first image 301 into multiple areas, and changing the pixel values to pixel values predefined for each area in accordance with the pixel values of the pixels belonging to each area. In this case, the LUT 24 defines pixel values corresponding to individual pixel values of pixels belonging to the area. The pixel values of the pixels belonging to the area may be defined, as an example, as a gray scale range for each area, that is, the minimum and maximum gray scale values. As another example, other characteristics such as an average value of gray scales may be used.
What defines the relationship between the pixel values of the first image data D1 and the pixel values of the second image data D2 is not limited to the table format shown in
The multiple areas may be two or more. As an example, the image generation unit 23 divides the first image 301 into predefined areas, each area being, for example, 10 pixels×10 pixels. A size of the area is not limited to a specific size and may be determined by predefined conditions. The image generation unit 23 determines the dataset of the pixel values of the second image for each area by calculating the maximum value and the minimum value of the pixel values for each area. The image generation unit 23 generates the second image data D2 by converting the pixel values of the pixels belonging to each area of the first image data D1 using the dataset of pixel values of the second image determined for each area.
When using the LUT 24 in
Preferably, a dataset is selected in which the difference between the pixel values of the first image data D1 and the pixel values of the second image data D2 is small. Thus, the influence of crosstalk due to response can be suppressed, and the viewer A can easily visually recognize the first image 301 when wearing the polarized glasses 200.
In the display system 100 according to the fourth embodiment, it is possible to use different datasets of pixel values of the second image for different areas of the first image 301. By generating the second image data D2 in this manner, the composite image of the first image 301 and the second image perceived by the viewer A when not wearing the polarized glasses 200 may have different gray scales for different areas. That is, by generating the second image data D2 in this manner, the third image including multiple gray scales can be perceived by the viewer A when not wearing the polarized glasses 200.
Note that the disclosure is not limited to the above-mentioned embodiments, and it is possible to make various changes.
While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-103653 | Jun 2023 | JP | national |
