Optical system

Abstract

To provide an optical system capable of selectively acquiring an image formed with light having different polarization states, in accordance with a polar angle.SOLUTION: The optical system includes a display device, an optical element, and an optical shutter. The optical element is disposed on the display device and is configured to transmit light from the display device. The optical shutter is disposed on the optical element. The optical element is further configured to maintain a polarization axis of light when driven and to rotate the polarization axis by 90° when not driven. The optical shutter includes a pair of linear polarizers having transmission axes intersecting each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] One embodiment of the present invention relates to an optical system having an image display function, for example, an optical system capable of capturing and viewing an image formed by light of different polarization states. [Background technology]

[0002] An in-vehicle display device in which a TN (Twisted Nematic) liquid crystal element is disposed on a liquid crystal display device is known (Patent Document 1). In this display device, the TN liquid crystal element can rotate the polarization axis of light from the liquid crystal display device, and by appropriately driving the TN liquid crystal element, the polarization axis of the light forming the image can be changed. As a result, by taking advantage of the different reflection characteristics of light with different polarization axes, it is possible not only to prevent image reflection on a reflective surface such as a windshield, but also to display an image on the reflective surface by utilizing the reflection. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-208606 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment of the present invention is to provide an optical system having a novel structure and an image display function, for example, an optical system capable of selectively acquiring images formed by light with different polarization states according to polar angles. [Means for solving the problem]

[0005] One embodiment of the present invention is an optical system. The optical system includes a display device, an optical element, and an optical shutter. The optical element is located on the display device and configured to transmit light from the display device. The optical shutter is disposed on the optical element. The optical element is further configured to maintain the polarization axis of the light when driven and to rotate the polarization axis by 90 degrees when not driven. The optical shutter has a pair of linear polarizers whose transmission axes cross each other. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic exploded perspective view of an optical system according to an embodiment of the present invention; [Figure 2] 1 is a schematic top view of a display device of an optical system according to one embodiment of the present invention; [Figure 3] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 4] 1 is a schematic side view of an optical system according to one embodiment of the present invention; [Figure 5] FIG. 1 is a schematic perspective view illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 6] FIG. 1 is a schematic perspective view illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic perspective view illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 8] FIG. 1 is a schematic perspective view illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 9] FIG. 1 is a schematic perspective view illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 10] 1A and 1B are schematic diagrams illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 11] 1A and 1B are schematic diagrams illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 12] 1A and 1B are schematic side views illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 13]1A and 1B are schematic side views illustrating the operation of an optical system according to an embodiment of the present invention. [Figure 14] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 15] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 16] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 17] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 18] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 19] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 20] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 21] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 22] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 23] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 24] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; [Figure 25] 1 is a schematic end view of a portion of an optical system according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, various embodiments of the present invention will be described with reference to the drawings, etc. However, the present invention can be embodied in various forms without departing from the spirit of the present invention, and should not be construed as being limited to the description of the embodiments exemplified below.

[0008] In order to clarify the description, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and each drawing, elements having the same function as those described in the previous drawings may be given the same reference numerals, and duplicated explanations may be omitted. This reference numeral is used to collectively represent multiple identical or similar structures, and when these are individually represented, a hyphen and a natural number are added after the reference numeral.

[0009] In this specification and claims, when expressing an aspect of placing another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case in which another structure is placed directly on top of a certain structure so as to be in contact with the certain structure, and a case in which another structure is placed above a certain structure via yet another structure.

[0010] In this specification and claims, the expression that two structures are "orthogonal" or "perpendicular to each other" includes not only a state in which the two structures intersect at 90°, but also a state in which the two structures intersect at an angle of 90°±10°. The expression that two structures are "parallel" includes a state in which the extension directions of the two structures form an angle of 0°±10°.

[0011] First Embodiment In this embodiment, an optical system according to one embodiment of the present invention will be described.

[0012] 1. Configuration FIG. 1 is a schematic exploded perspective view of an optical system 100 according to an embodiment of the present invention. As shown in FIG. 1, the optical system 100 includes a display device 110 and an optical element 200 disposed on the display device 110 and overlapping the display device 110. As will be described in detail later, if the display device 110 includes a liquid crystal element, a backlight 102 is further provided. Although components such as the display device 110, the optical element 200, and the backlight 102 are shown separately in FIG. 1, these components are fixed to each other directly or by an adhesive layer, a fixing jig, a housing, or the like. For example, the display device 110 and the optical element 200 can be fixed to each other by an adhesive layer 104 containing a polymer such as an epoxy resin or an acrylic resin. Although not shown in FIG. 1, as will be described later, the optical system 100 further includes an optical shutter.

[0013] (1) Backlight The backlight 102 is a light source that irradiates the optical system 100 with light. A known structure can be adopted for the backlight 102, and therefore a detailed description thereof will be omitted. Briefly, the backlight 102 includes a cold cathode fluorescent lamp and / or a light emitting diode (LED) that functions as a light source, and is composed of a reflector for effectively utilizing the light from the light source, a light diffusion plate for uniformly diffusing the light, a light guide plate, a prism sheet, and the like. The light from the backlight 102 is incident on the optical element 200 via the display device 110.

[0014] (2)Display device A liquid crystal display device or an electroluminescence display device can be used as the display device 110. The display device 110 may be an active matrix type display device or a passive matrix type display device. In this embodiment, as an example, an example will be described in which an active matrix type liquid crystal display device is used as the display device 110.

[0015] FIG. 2 shows a schematic top view of the display device 110, and FIG. 3 shows a schematic end view of the optical system 100 excluding the optical shutter. As shown in these figures, the display device 110 includes a substrate 112 and an opposing substrate 124 facing the substrate 112. The substrate 112 and the opposing substrate 124 are configured to transmit light from the display device 110 and to provide mechanical strength to the display device 110. Therefore, both the substrate 112 and the opposing substrate 124 are configured to contain glass or a resin such as polyimide or polycarbonate so as to transmit visible light. The substrate 112 and the opposing substrate 124 may be flexible.

[0016] Various patterned insulating films, conductive films, and semiconductor films are laminated between the substrate 112 and the opposing substrate 124. These films form a pixel circuit including pixels 120, driving circuits (scanning line driving circuit 114, signal line driving circuit 116), terminals 118, and transistors 130. Power and various signals are input from an external circuit (not shown) via the terminals 118, and the driving circuit generates control signals (gate signals, initialization signals, video signals, etc.) for displaying images and supplies them to the pixels 120. The display device 110 can display images by controlling the pixels 120 with the control signals.

[0017] There are no restrictions on the configuration of the pixel circuit, and the pixel circuit is composed of multiple transistors including the transistor 130, one or more capacitive elements (not shown), and the like. In the example shown here, the transistor 130 is provided on an undercoat 122, which is an inorganic insulating film, and is composed of a semiconductor film 132, a gate insulating film 134, a gate electrode 136, an interlayer insulating film 138, and a pair of terminals 140, 142, and the like. The configuration of the transistor 130 can also be determined arbitrarily, and it may be a top-gate transistor as shown in FIG. 3 or a bottom-gate transistor, for example. A planarization film 144 is provided on the pixel circuit to absorb unevenness thereon.

[0018] The display device 110 further includes a liquid crystal element 150 on the planarization film 144. The liquid crystal element 150 shown in FIG. 3 is a so-called TN liquid crystal element, and includes a pixel electrode 152 electrically connected to the transistor 130, a first alignment film 154 on the pixel electrode 152, a liquid crystal layer 156 on the first alignment film 154, a second alignment film 158 on the liquid crystal layer 156, and a common electrode 160 to which a common potential is applied. On the common electrode 160, a color filter 172 overlapping the pixel electrode 152 via an optional overcoat 174, a black matrix 170 for preventing light leakage between adjacent pixels 120, and other components are provided. With this configuration, the pixel 120 functions as a minimum unit for providing color information. Although not shown, the liquid crystal element 150 is not limited to a TN liquid crystal element, and a VA (Vertical Alignment) liquid crystal element or an IPS (In-Plane Switching) liquid crystal element may also be used.

[0019] The first alignment film 154 and the second alignment film 158 contain a resin such as polyimide, and are configured to align the liquid crystal molecules contained in the liquid crystal layer 156 in a certain direction. For this reason, the first alignment film 154 and the second alignment film 158 are subjected to an alignment treatment such as a rubbing treatment, or are formed using photo-alignment. The directions in which the first alignment film 154 and the second alignment film 158 align the liquid crystal molecules (the long axis directions of the liquid crystal molecules when aligned by the influence of the alignment film, hereinafter referred to as alignment directions) are perpendicular to each other.

[0020] The display device 110 further includes a first linear polarizer 180 below the substrate 112, and a second linear polarizer 182 on the counter substrate 124. The first linear polarizer 180 and the second linear polarizer 182 are arranged to have a crossed Nicol relationship. Therefore, light from the backlight 102 becomes linearly polarized light (e.g., P-polarized light) when it passes through the first linear polarizer 180. If the liquid crystal element 150 is a TN liquid crystal element, this linearly polarized light is rotated by 90° by the liquid crystal layer 156 when the display device 110 is not driven, becoming linearly polarized light (e.g., S-polarized light) and passing through the second linear polarizer 182. Therefore, linearly polarized light is incident on the optical element 200.

[0021] The transmission axis of the first linear polarizer 180 may be parallel to one side of the substrate 112 or may be tilted with respect to the side of the substrate 112. In the latter case, it is preferable to provide the first linear polarizer 180 so that the transmission axis of the first linear polarizer 180 is tilted at 45° with respect to the side of the substrate 112. As described above, the first linear polarizer 180 and the second linear polarizer 182 are in a crossed Nicol relationship. Therefore, when the transmission axis of the first linear polarizer 180 is parallel to one side of the substrate 112, the transmission axis of the second linear polarizer 182 is perpendicular to that side. On the other hand, when the transmission axis of the first linear polarizer 180 is tilted with respect to one side of the substrate 112, the transmission axis of the second linear polarizer 182 is also tilted with respect to that side at the same angle.

[0022] (3) Optical elements The optical element 200 is configured to transmit light emitted from the display device 110 and control the polarization axis of the light, and includes a TN liquid crystal element. Specifically, as shown in FIGS. 1 and 3, the optical element 200 includes a substrate 202 and an opposing substrate 204 facing the substrate 202. Like the substrate 112 and the opposing substrate 124, the substrate 202 and the opposing substrate 204 are configured to transmit light from the display device 110 and to provide mechanical strength to the optical element 200. Therefore, the substrate 202 and the opposing substrate 204 are configured to contain glass or a resin such as polyimide or polycarbonate so as to transmit visible light. The substrate 202 and / or the opposing substrate 204 may also be flexible.

[0023] Between the substrate 202 and the counter substrate 204, there are provided a first electrode 212, a third alignment film 214 on the first electrode 212, a liquid crystal layer 216 on the third alignment film 214, a fourth alignment film 218 on the liquid crystal layer 216, and a second electrode 220 on the fourth alignment film 218. The first electrode 212, the third alignment film 214, the liquid crystal layer 216, the fourth alignment film 218, and the second electrode 220 constitute a TN liquid crystal element. Optionally, the optical element 200 may have protective insulating films 210 and 222 between the substrate 202 and the first electrode 212 and / or between the counter substrate 204 and the second electrode 220. The protective insulating films 210 and 222 may be composed of one or more films containing a silicon-containing inorganic compound such as silicon nitride or silicon oxide. By providing the protective insulating films 210 and 222 , impurities such as alkali metals contained in the substrate 202 and the counter substrate 204 can be prevented from penetrating into the liquid crystal layer 216 .

[0024] Both the first electrode 212 and the second electrode 220 are configured to transmit visible light. Therefore, the first electrode 212 and the second electrode 220 preferably include a conductive oxide that transmits visible light, such as indium tin oxide (ITO) or indium zinc oxide (IZO). The first electrode 212 and the second electrode 220 may each be formed as a single conductive film, or, although not shown, may be formed of multiple conductive films arranged in a stripe pattern. For example, one of the first electrode 212 and the second electrode 220 may be formed as a single conductive film that overlaps all of the pixels 120, and the other may be formed as multiple conductive films arranged in a stripe pattern.

[0025] Like the first alignment film 154 and the second alignment film 158, the third alignment film 214 and the fourth alignment film 218 also contain a resin such as polyimide and are configured to align the nematic liquid crystal molecules contained in the liquid crystal layer 216 in a specific direction. For this reason, the third alignment film 214 and the fourth alignment film 218 are subjected to an alignment treatment such as rubbing, or are formed using photo-alignment. The alignment directions of the third alignment film 214 and the fourth alignment film 218 are also perpendicular to each other. Furthermore, it is preferable that the alignment direction of the third alignment film 214 be parallel to the transmission axis of the second linear polarizer 182. As will be described later, by disposing the optical element 200 having such a configuration, the polarization axis of linearly polarized light incident on the optical element 200 from the display device 110 is rotated by 90° by the liquid crystal layer 216 when the optical element 200 is not driven, and the polarization direction is maintained when the optical element 200 is driven.

[0026] In the optical system 100 having the above configuration, a polarizing plate does not need to be disposed on the optical element 200. Therefore, the adhesive layer 104 that fixes the display device 110 and the optical element 200 together may be in direct contact with the second linear polarizing plate 182 and the substrate 202. Furthermore, the counter substrate 204 may be directly exposed to the outside air.

[0027] (4) Optical shutter As shown in FIG. 4, the optical system 100 includes an optical shutter 230 on an optical element 200. The optical shutter 230 includes a pair of linear polarizers 232 and 234 whose transmission axes are orthogonal to each other. Hereinafter, to distinguish between the first linear polarizer 180 and the second linear polarizer 182, the linear polarizers 232 and 234 will be referred to as optical selection polarizers 232 and 234, respectively. The optical selection polarizer 232 is disposed parallel to the display device 110. That is, the optical selection polarizer 232 is disposed so that its principal surface is perpendicular to the normal to the principal surface of the display device 110 (e.g., the principal surface of the substrate 112). On the other hand, the other optical selection polarizer 234 is disposed so as to be tilted with respect to the display device 110. Specifically, the optical selection polarizer 234 is disposed so that the normal to its principal surface is tilted at a polar angle θ1 from the normal to the principal surface of the display device 110. The polar angle θ1 is, for example, 20°±5°.

[0028] Furthermore, the optical shutter 230 is configured to selectively or preferentially transmit light emitted from the optical element 200 through one of the optical selection polarizers 232, 234 when the optical element 200 is driven, and to selectively or preferentially transmit the light through the other of the optical selection polarizers 232, 234 when the optical element 200 is not driven. For example, the optical selection polarizer 232 is arranged so that its transmission axis (see the straight arrow in the figure) is parallel to the polarization axis of light emitted from the optical element 200 when the optical element 200 is not driven. In the optical system 100 configured as described above, light is rotated by 90° by the optical element 200 when the optical element 200 is not driven, so that the polarization axis of light emitted from the optical element 200 and incident on the optical selection polarizer 232 when the optical element 200 is not driven is perpendicular to the transmission axis of the second linear polarizer 182. Therefore, the optical selection polarizer 232 is arranged so that its transmission axis is parallel to the transmission axis of the second linear polarizer 182. On the other hand, the transmission axis of the optical selective polarizer 234 is orthogonal to that of the optical selective polarizer 232, and therefore the optical selective polarizer 234 is arranged so that its transmission axis is perpendicular to the transmission axis of the second linear polarizer 182. With this configuration, when the optical element 200 is not driven, the image displayed by the display device 110 can be selectively or preferentially acquired via the optical selective polarizer 234. On the other hand, when the optical element 200 is driven, the polarization axis of the light incident on the optical element 200 is maintained, and therefore the image can be selectively or preferentially acquired via the optical selective polarizer 232.

[0029] Conversely, the optical system 100 may be configured so that an image is acquired via the optical selective polarizer 232 when the optical element 200 is not driven, and so that an image is acquired via the optical selective polarizer 234 when the optical element 200 is driven. In this case, the optical selective polarizer 232 may be arranged so that its transmission axis is parallel to the polarization axis of light emitted from the optical element 200 when the optical element 200 is not driven. That is, the optical selective polarizer 232 may be arranged so that its transmission axis is perpendicular to the transmission axis of the second linear polarizer 182. Conversely, since the transmission axis of the optical selective polarizer 234 is orthogonal to the optical selective polarizer 232, the optical selective polarizer 234 is arranged so that its transmission axis is parallel to the transmission axis of the second linear polarizer 182. In this way, by using the optical system 100 having the above configuration, it is possible to observe and acquire images formed by light with different polarization states.

[0030] 2. Light control using optical systems As described above, the optical element 200 disposed on the display device 110 is a TN liquid crystal element. Therefore, when the optical element 200 is not driven, i.e., when no potential difference is applied between the first electrode 212 and the second electrode 220, the liquid crystal molecules are aligned according to the alignment directions of the third alignment film 214 and the fourth alignment film 218. Specifically, the liquid crystal molecules are aligned along the alignment direction of the third alignment film 214 on the first electrode 212 side, and along the alignment direction of the fourth alignment film 218 on the second electrode 220 side. Because the alignment directions of the third alignment film 214 and the fourth alignment film 218 are perpendicular to each other, the alignment direction of the liquid crystal molecules is twisted as they move from the first electrode 212 toward the second electrode 220, and is ultimately twisted by 90°. Therefore, light incident on the optical element 200 is rotated by 90° within the liquid crystal layer 216. In contrast, when optical element 200 is driven, that is, when a potential difference is applied between first electrode 212 and second electrode 220 and a sufficient vertical electric field is formed between them, the liquid crystal molecules are aligned in the direction of the electric field, that is, in a direction perpendicular to first electrode 212. In this case, the light incident on optical element 200 is not rotated, and the polarization axis is maintained.

[0031] 5, the polarization axis of light (indicated by the hollow arrow in the figure) emitted from the display device 110 is parallel to the transmission axis (indicated by the solid arrow) of the second linear polarizer 182. When the optical element 200 is not driven (OFF), the polarization axis of the incident light is rotated by 90° by the optical element 200, and therefore the polarization axis of the light emitted from the optical element 200 is perpendicular to the transmission axis of the second linear polarizer 182. In contrast, when the optical element 200 is driven (ON), the polarization axis of the incident light is not rotated, and therefore the polarization axis of the light emitted from the optical element 200 is parallel to the transmission axis of the second linear polarizer 182 (see the hollow arrow in FIG. 6).

[0032] The same applies when the alignment axis of the second linear polarizer 182 is tilted from one side of the substrate 112. Specifically, by arranging the second linear polarizer 182 so that its transmission axis is tilted from one side of the substrate 112, the polarization axis of the light (white arrow) output from the display device 110 is tilted from one side of the substrate 112, as shown in FIG. 7. When the optical element 200 is not driven (OFF), the polarization axis of the incident light is rotated by 90° by the optical element 200, so that the polarization axis of the light output from the optical element 200 is also tilted from that side. When the polarization axis of the light output from the display device 110 is tilted by 45° from one side of the substrate 112, the polarization axis of the light output from the optical element 200 is tilted by 135° from that side. On the other hand, when the optical element 200 is driven (ON), the polarization axis of the incident light is maintained without rotation, so that the polarization axis of the light output from the optical element 200 (white arrow in FIG. 8) is also tilted from that side. When the polarization axis of light emitted from display device 110 is tilted at 45° from one side of substrate 112, the polarization axis of light emitted from optical element 200 will also be tilted at 45° from that side.

[0033] By utilizing the above-described characteristics, it is possible to acquire and observe an image formed by light of different polarization states depending on the viewing angle (i.e., polar angle) of the optical system 100. This will be explained using FIGS. 9 to 11. In the following explanation, as shown in FIG. 9, an example will be used in which the polarization axis of the polarized light output from the display device 110 is tilted 45° from one side of the substrate 202. The directions of two adjacent sides of the substrate 202 are defined as the x direction and the y direction, respectively, and the normal direction of the substrate 202 is defined as the z direction. The polar angle θ1 is the angle tilted from the z direction to the y direction, and the azimuthal angle θ2 is the angle tilted from the x direction to the y direction.

[0034] By driving the display device 110, each pixel 120 produces red, green, or blue light with controlled gradations, which are combined to form an image. This image is formed by light having a polarization axis tilted 45° from one side of the substrate 112 or 202, and is incident on the optical element 200. Here, as schematically shown in FIG. 10 , the polarization state of light observed through the optical element 200 at a polar angle θ1 of 0° (i.e., facing the optical system 100) is substantially the same whether the optical element 200 is driven or not, and is virtually independent of the azimuth angle θ2. Specifically, the Stokes parameter S3 remains nearly zero even when the azimuth angle θ2 changes, is independent of the azimuth angle θ2, and the light emitted from the optical system 100 is substantially linearly polarized.

[0035] Even when observing at an angle where the polar angle θ1 is shifted from 0° and tilted from the normal to the optical system 100 (for example, when the polar angle θ1 is 20°), linearly polarized light is observed with little dependence on the azimuth angle θ2 when the optical element 200 is not driven, as shown in FIG. 11 . In contrast, when the optical element 200 is driven, the polarization state is highly dependent on the azimuth angle θ2. At azimuth angles θ2 of approximately 45°, 135°, 225°, and 315°, the light emitted from the optical system 100 is nearly linearly polarized, but at other angles, it deviates from linear polarization and approaches circular polarization. In particular, when the azimuth angle θ2 is approximately 0°, 90°, 180°, and 270°, the light emitted from the optical system 100 is closest to circular polarization, becoming elliptically polarized. In other words, the intensity difference between the orthogonal polarized light is maximized.

[0036] Therefore, in the optical system 100, by switching the optical element 200 on and off, it is possible to observe and acquire an image formed by light whose polarization state varies depending on the polar angle θ1. As described above, the optical selection polarizer 232 of the optical shutter 230 is disposed parallel to the display device 110 (see FIG. 4), and therefore an image with a polar angle θ1 of 0° is incident on the optical selection polarizer 232. As shown in FIG. 12, when the optical element 200 is not driven, the polarization axis of light incident on the optical element 200 from the display device 110 is rotated by 90° by the optical element 200. Therefore, by arranging the optical selection polarizer 232 so that the polarization axis of light (white arrow) emitted from the optical element 200 is perpendicular to the transmission axis (see solid arrow) of the optical selection polarizer 232, this image is blocked by the optical selection polarizer 232. On the other hand, an image is incident on the optical selection polarizer 234 at a polar angle θ1. Furthermore, as described above, the transmission axis of the optical selection polarizing plate 234 is perpendicular to the transmission axis of the optical selection polarizing plate 232. Therefore, by arranging the optical selection polarizing plate 234 so that the light emitted from the optical element 200 is incident at an azimuth angle θ2 at which the Stokes parameter S3 is minimum or maximum, the light emitted from the optical element 200 can be transmitted through the optical selection polarizing plate 234. Therefore, when the optical element 200 is not driven, it is possible to selectively or preferentially acquire an image that has passed through the optical selection polarizing plate 234.

[0037] On the other hand, when the optical element 200 is driven, the polarization axis of light incident on the optical element 200 is maintained even after passing through the optical element 200 (see the hollow arrow and the solid arrow below it in FIG. 13), and the polarization axis of this light becomes parallel to the transmission axis (solid arrow) of the optical selection polarizer 232. Therefore, an image can be acquired through the optical selection polarizer 232. On the other hand, light having a polarization axis perpendicular to the transmission axis is incident on the optical selection polarizer 232 arranged at a polar angle θ1. Therefore, the light emitted through the optical element 200 is blocked by the optical selection polarizer 234. Due to this mechanism, when the optical element 200 is driven, an image that has passed through the optical selection polarizer 232 can be selectively acquired.

[0038] For the present purpose of observing orthogonal polarization states at different polar angles, when considering whether it is more advantageous to use the polarization state when the optical element is driven or when it is not driven, it is preferable to use the non-driven state when the polar angle θ1 is not 0 degrees, and to use the polarization state when the optical element is driven when θ1 is 0 degrees.

[0039] The optical selection polarizing plate 234 does not necessarily have to be tilted from the display device 110, and may be arranged parallel to the display device 110. In this case, it is preferable to arrange it so that light that has passed through the optical element 200 is incident at the Brewster angle at which the reflectance of one polarized light becomes zero.

[0040] In this way, by using the optical system 100, it is possible to selectively acquire and view images formed with light of different polarization states. That is, it is possible to selectively acquire and view images formed with linearly polarized light whose polarization axes are orthogonal to each other. Furthermore, although not shown, the images acquired via the optical selective polarizers 232 and 234 may be superimposed using a half mirror or a polarizing beam splitter. This makes it possible to synthesize multiple images using a single display device 110.

[0041] Second Embodiment In this embodiment, modifications of the optical system 100 described in the first embodiment will be described. Descriptions of configurations that are the same as or similar to the configuration described in the first embodiment may be omitted. The modifications described below can be appropriately combined with the optical system 100 described in the first embodiment, and modifications may also be combined with each other.

[0042] 1. Variation 1 In the optical system 100 described in the first embodiment, a pair of linear polarizers (a first linear polarizer 180 and a second linear polarizer 182) is provided in the display device 110. The optical system 100 according to the first modification may further include a half-wave plate (a half-wave plate). For example, as shown in FIG. 14 , the display device 110 may have a half-wave plate 184 on the second linear polarizer 182. In this case, the adhesive layer 104 that fixes the display device 110 and the optical element 200 may be in direct contact with the substrate 202 and the half-wave plate 184. Alternatively, as shown in FIG. 15 , the optical element 200 may have the half-wave plate 184 below the substrate 202. In this case, the adhesive layer 104 may be in direct contact with the second linear polarizer 182 and the half-wave plate 184.

[0043] In the first modification, the half-wave plate 184 rotates the polarization axis of the light emitted from the display device 110 by 45°. Therefore, for example, when the polarization axis of the light emitted from the display device 110 is parallel to one side of the substrate 202, this light can be converted into polarized light having a polarization axis tilted by 45° with respect to that side, and can be incident on the optical element 200. Conversely, when the polarization axis of the light emitted from the display device 110 is tilted by 45° from one side of the substrate 202, this light can be converted into polarized light having a polarization axis parallel to that side, and can be incident on the optical element 200.

[0044] 2. Variation 2 In the optical system 100, a third linear polarizer 186 may be further disposed between the substrate 202 and the counter substrate 124. For example, the third linear polarizer 186 may be provided below the substrate 202 (FIG. 16). In this case, the adhesive layer 104 may be in direct contact with the third linear polarizer 186 and the second linear polarizer 182. The third linear polarizer 186 is disposed so that its transmission axis is parallel to that of the second linear polarizer 182.

[0045] As described above, the display device 110 and the optical element 200 are fixed to each other by the adhesive layer 104, but if misalignment occurs during fixing, the polarization axis of the light emitted from the display device 110 is not necessarily parallel to one side of the substrate 202 or tilted at a predetermined angle (for example, 45°) from that side. In contrast, by providing the third linear polarizer 186, even if such misalignment occurs, the polarization axis of the light incident on the optical element 200 can be set to be parallel to one side of the substrate 202 or at a predetermined angle from that side.

[0046] Alternatively, the third linear polarizer 186 may not be provided in the optical element 200, but may be provided in the display device 110 (FIG. 17). In this case, the third linear polarizer 186 is provided on the second linear polarizer 182. The adhesive layer may be in direct contact with the third linear polarizer 186 and the substrate 202.

[0047] 3. Variation 3 In the optical system 100 described in the first embodiment, a pair of linear polarizers (a first linear polarizer 180 and a second linear polarizer 182) is provided in the display device 110. In contrast, in the optical system 100 according to the third modification, as shown in FIG. 18 , the first linear polarizer 180 is provided below the substrate 112, but the second linear polarizer 182 is not provided in the display device 110. The second linear polarizer 182 is provided below the substrate 202 of the optical element 200, thereby making it possible to obtain a gradation based on a video signal from each pixel 120. The adhesive layer 104 may be in direct contact with the counter substrate 124 and the second linear polarizer 182.

[0048] In the third modification, the light incident on the TN liquid crystal element, which is responsible for the optical rotation of light, is linearly polarized by the second linear polarizer 182 below the substrate 202, and therefore the polarization state of the light that forms the image can be switched by the optical element 200. Although not shown, the third linear polarizer 186 may also be provided in the third modification, as in the second modification. The third linear polarizer 186 is provided between the second linear polarizer 182 and the substrate 202. The third linear polarizer 186 may be in direct contact with the second linear polarizer 182.

[0049] 19 , the optical element 200 may include a second linear polarizing plate 182 and a half-wave plate 184 sandwiched between the second linear polarizing plate 182 and a substrate 202.

[0050] 4. Variation 4 The display device 110 of the optical system 100 described above uses a liquid crystal element 150 as a display element. However, the configuration of the display device 110 is not limited to this. As shown in FIG. 20 , an electroluminescent element 190 may be used as a display element. The electroluminescent element 190 is composed of a pixel electrode 152, a common electrode 160 on the pixel electrode 152, and an electroluminescent layer 192 between them. An insulating bank 146 containing a polymer such as polyimide or polysiloxane resin is provided at the end of the pixel electrode 152 to prevent the electroluminescent layer 192 from being disconnected and electrically insulate adjacent pixels 120 from each other. The electroluminescent layer 192 may be composed of multiple functional layers containing organic compounds. The electroluminescent layer 192 may have a known configuration, such as a combination of functional layers including a charge injection layer, a charge transport layer, a charge blocking layer, and a light-emitting layer. As an optional configuration, a sealing film 194 for protecting the electroluminescent element 190 may be provided on the common electrode 160. When the electroluminescent element 190 is used as the display element, the backlight 102 does not need to be used.

[0051] The display device 110 of the optical system 100 according to the fourth modification does not need to include the first linear polarizer 180, but only needs to include a second linear polarizer 182 on the counter substrate 124. This allows light emitted from the electroluminescent element 190 to be converted into linearly polarized light and supplied to the optical element 200. Alternatively, the second linear polarizer 182 may not be included in the display device 110, but may be provided below the substrate 202 of the optical element 200 (FIG. 21). Alternatively, to prevent problems caused by the misalignment described above, a third linear polarizer 186 may be disposed on the second linear polarizer 182 of the display device 110 (FIG. 22). Alternatively, the second linear polarizer 182 may be provided on the counter substrate 124 of the display device 110, and a third linear polarizer 186 may be provided below the substrate 202 of the optical element 200 (FIG. 23).

[0052] 5. Variation 5 As in the first modification, when the electroluminescent element 190 is used as a display element, the half-wave plate 184 may also be used. For example, as shown in Fig. 24, a second linear polarizing plate 182 and a half-wave plate 184 may be sequentially disposed on the counter substrate 124 of the display device 110. Alternatively, as shown in Fig. 25, no polarizing plate may be disposed in the display device 110, but the second linear polarizing plate 182 may be provided below the substrate 202 of the optical element 200, and the half-wave plate 184 may be disposed between the substrate 202 and the second linear polarizing plate 182.

[0053] In any of the above-described modifications, it is possible to selectively acquire and view images formed by linearly polarized light that is orthogonal to each other, as with the optical system 100 described in the first embodiment. It is also possible to synthesize multiple images using one display device 110.

[0054] The above-described embodiments of the present invention can be combined as appropriate as long as they are not mutually inconsistent. Furthermore, even if a person skilled in the art appropriately adds or deletes components or modifies the design of a display device of each embodiment, or adds or omits processes or modifies conditions, such a display device is included in the scope of the present invention as long as it includes the gist of the present invention.

[0055] Even if there are other effects and advantages different from those brought about by the aspects of each of the above-mentioned embodiments, those that are clear from the description in this specification or that can be easily predicted by a person skilled in the art are naturally understood to be brought about by the present invention. [Explanation of symbols]

[0056] 100: optical system, 102: backlight, 104: adhesive layer, 110: display device, 112: substrate, 114: scanning line driving circuit, 116: signal line driving circuit, 118: terminal, 120: pixel, 122: undercoat, 124: opposing substrate, 130: transistor, 132: semiconductor film, 134: gate insulating film, 136: gate electrode, 138: interlayer insulating film, 140: terminal, 142: terminal, 144: planarizing film, 146: bank, 150: liquid crystal element, 152: pixel electrode, 154: first alignment film, 156: liquid crystal layer, 158: second alignment film, 160: common electrode, 170: black matrix, 172: color filter, 174: overcoat, 180: first linear polarizer, 182: second linear polarizer, 184: wavelength plate, 186: third linear polarizer, 190: electroluminescent element, 192: electroluminescent layer, 194: sealing film, 200: optical element, 202: substrate, 204: opposing substrate, 210: protective insulating film, 212: first electrode, 214: third alignment film, 216: liquid crystal layer, 218: fourth alignment film, 220: second electrode, 222: protective insulating film, 230: optical shutter, 232: optically selective polarizer, 234: optically selective polarizer

Claims

1. display device, an optical element positioned above the display device and transmitting light from the display device; and an optical shutter disposed on the optical element; the optical element is configured to maintain the polarization axis of the light when driven and to rotate the polarization axis by 90° when not driven; The optical shutter comprises a pair of linear polarizers whose transmission axes cross each other.

2. The display device includes: a first linear polarizer; a liquid crystal element on the first linear polarizer; and a second linear polarizer on the liquid crystal element; The optical system of claim 1 , wherein the optical element comprises a TN liquid crystal element.

3. The optical system of claim 2 further comprising a half wave plate between the display device and the optical element.

4. The display device includes: a first linear polarizer, and a liquid crystal element on the first linear polarizer; The optical element is a second linear polarizer, and 10. The optical system of claim 1, further comprising a TN liquid crystal element on the second linear polarizer.

5. The optical system of claim 4 , further comprising a half-wave plate between the second linear polarizer and the TN liquid crystal element.

6. The display device includes: Electroluminescent display devices, and a first linear polarizer on the electroluminescent display device; The optical system of claim 1 , wherein the optical element comprises a TN liquid crystal element.

7. The optical system of claim 6 , further comprising a half-wave plate between the electroluminescent display device and the optical element.

8. the display device comprises an electroluminescent display device, The optical element is a first linear polarizer, and 10. The optical system of claim 1, further comprising a TN liquid crystal element on the first linear polarizer.

9. The optical system of claim 8 , further comprising a half-wave plate between the first linear polarizer and the TN liquid crystal element.

10. a third linear polarizer between the display device and the optical element; The optical system of claim 2 , wherein the transmission axis of the third linear polarizer is parallel to the polarization axis of the light from the display device.

11. a third linear polarizer between the display device and the optical element; The optical system of claim 4 , wherein the transmission axis of the third linear polarizer is parallel to the polarization axis of the light from the display device.

12. a third linear polarizer between the display device and the optical element; The optical system of claim 6 , wherein the transmission axis of the third linear polarizer is parallel to the polarization axis of the light from the display device.

13. a third linear polarizer between the display device and the optical element; The optical system of claim 7 , wherein the transmission axis of the third linear polarizer is parallel to the polarization axis of the light from the display device.

14. the pair of linear polarizers includes a first optically selective polarizer and a second optically selective polarizer; the first optically selective polarizer is disposed parallel to the display device; 2. The optical system according to claim 1, wherein the second optically selective polarizer is disposed so that a normal to a principal surface thereof is inclined from a normal to a principal surface of the display device.

15. 15. The optical system of claim 14, wherein the normal to the main surface of the second optical selective polarizer and the normal to the main surface of the display device are inclined at 20°±5°.

16. The optical system according to claim 14 , wherein the first optical selective polarizing plate is arranged so that its transmission axis is parallel to the polarization axis of light emitted from the optical element when the optical element is not driven.

Images