Liquid crystal display device

Abstract

The invention relates to a liquid crystal display device. The liquid crystal display device includes: a liquid crystal panel including a display area; a backlight unit located behind the liquid crystal panel and including a plurality of optical sheets stacked; a light source of invisible light, the light source of invisible light being disposed inside or behind the backlight unit; a diffusion structure unit located in front of the light source and configured to diffuse invisible light from the light source; and a lens unit configured to converge the light diffused by the diffusion structure unit, impinging on an object, and reflected by the object onto a sensor. The optical sheet includes a diffusion sheet. The size of the diffusion structure unit is smaller than that of the display area, and the diffusion structure unit is selectively arranged at the position irradiated by the invisible light from the light source. At least one of the optical sheets is interposed between the diffusion structure unit and the light source.

Description

Technical Field

[0001] The present invention relates to a liquid crystal display device. Background Art

[0002] Liquid crystal display devices have a wide range of applications from small mobile phones to large television monitors due to their low power consumption and high resolution characteristics. The liquid crystal display device may be equipped with a camera device including a light source and a sensor for identifying an object to identify fingerprints or gestures.

[0003] An example of a tool for identifying gestures is a NIR-ToF camera unit, which includes a vertical cavity surface emitting laser (VCSEL) that emits near-infrared (NIR) light, a time-of-flight (ToF) image sensor, and a lens unit.

[0004] The NIR-ToF camera unit calculates the distance to an object based on the time it takes for the NIR light emitted from the VCSEL to return to the ToF image sensor through the lens unit after hitting the object and being reflected by the object. In order to use the NIR-ToF camera unit on a liquid crystal panel, the NIR-ToF camera unit is usually disposed behind a cover glass. The area where the NIR-ToF camera is disposed becomes a non-display area. Summary of the Invention

[0005] In order to enable the NIR-ToF camera unit to reduce the light emitted from the VCSEL but blocked by the lens unit, it is important to provide a large distance between the lens unit and the VCSEL. Especially in the case of a type with a wide viewing angle, a larger distance is required; it is difficult to reduce the size of the NIR-ToF camera unit. In order to mount the NIR-ToF camera behind the liquid crystal panel, holes must be formed through the liquid crystal panel for both the lens unit and the VCSEL; these areas become non-display areas where no image can be displayed.

[0006] A liquid crystal display device according to an aspect of the present invention includes: a liquid crystal panel including a display area for displaying an image toward a viewer in front of the liquid crystal display device; a backlight unit located behind the liquid crystal panel, the backlight unit including a plurality of stacked optical sheets; a light source of invisible light disposed inside or behind the backlight unit; a diffusion structure unit located in front of the light source, the diffusion structure unit being configured to diffuse the invisible light from the light source; and a lens unit configured to converge the light diffused by the diffusion structure unit, impinging on an object and reflected by the object, onto a sensor. The plurality of optical sheets include a diffusion sheet configured to diffuse visible light. The size of the diffusion structure unit is smaller than the display area and is selectively disposed at a position irradiated with the invisible light from the light source. At least one of the plurality of optical sheets is interposed between the diffusion structure unit and the light source.

[0007] One aspect of the present invention enables the size of a camera unit used in a liquid crystal display device to be reduced.

[0008] It should be understood that the above general description and the following detailed description are both exemplary and explanatory and do not limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematically shows a liquid crystal display device in an embodiment.

[0010] Figure 2 is a plan view schematically showing a configuration example of a camera unit.

[0011] Figure 3 Schematically shows a cross-sectional structure of a part of a liquid crystal display device in an embodiment of the present invention.

[0012] Figure 4 is a diagram showing the positional relationship between a light source unit and a lens unit.

[0013] Figure 5 Schematically shows a cross-sectional structure of a part of a liquid crystal display device in another embodiment of the present invention.

[0014] Figure 6 Schematically shows a cross-sectional structure of a part of a liquid crystal display device in still another embodiment of the present invention.

[0015] Figure 7 Schematically shows a cross-sectional structure of a part of a liquid crystal display device in still another embodiment of the present invention.

[0016] Figure 8 The cross-sectional structure of a part of a liquid crystal display device in yet another embodiment of the present invention is schematically shown.

[0017] Figure 9 The cross-sectional structure of a part of a liquid crystal display device in yet another embodiment of the present invention is schematically shown.

[0018] Figure 10 Examples of the intensity distribution of light diffused by different diffusion sheets are provided. Detailed Embodiments

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the embodiments are merely examples for implementing the present invention and do not limit the technical scope of the present invention.

[0020] The present invention relates to a camera unit including a light source unit and a light receiving unit. An example of the camera unit is a NIR-ToF camera unit. The light from its light source unit is near-infrared (NIR) light, and its light receiving unit is a time-of-flight (ToF) camera.

[0021] In order for the NIR-ToF camera unit to reduce the light emitted from the light source unit but blocked by the light receiving unit, it is important to provide a large distance between the light receiving unit and the light source unit. Especially in the case of a type with a wide viewing angle, a larger distance is required; it is difficult to reduce the size of the NIR-ToF camera unit. In order to mount the NIR-ToF camera behind the liquid crystal panel, holes must be opened through the liquid crystal panel for both the lens unit and the VCSEL; these areas become non-display areas where no image can be displayed.

[0022] In one embodiment of the present invention, a diffusion structure unit (also simply referred to as a diffusion structure) of the light source unit is provided at a position higher than and away from the emission surface of the light source. Therefore, the distance between the light source unit and the light receiving unit can be reduced, allowing the size of the camera unit to be reduced. Hereinafter, the embodiments of the present invention will be described in more detail.

[0023] Embodiment 1

[0024] Configuration of the Liquid Crystal Display Device

[0025] Figure 1 The liquid crystal display device in the present embodiment is schematically shown. The liquid crystal display device 1 displays an image toward a viewer on the display area 15 of the liquid crystal panel. The periphery of the display area 15 is a border area 18 that serves as a non-display area. The liquid crystal display device 1 includes a backlight unit (not shown) and a camera unit 10 provided behind the liquid crystal panel.

[0026] Figure 2It is a plan view schematically showing a configuration example of the camera unit 10. The camera unit 10 includes a light source unit 11, a light receiving unit 13, and a substrate 17. The light source unit 11 and the light receiving unit 13 are provided on the substrate 17. The substrate 17 can be replaced by two substrates, and the light source unit 11 and the light receiving unit 13 can be mounted on different substrates.

[0027] The light source unit 11 emits light toward an object located on the front side where the viewer is. The light receiving unit 13 receives the light emitted by the light source unit 11 and reflected from the object. The camera unit 10 can be a NIR-ToF camera unit. The light from the light source unit 11 is near-infrared (NIR) light. The wavelength of the NIR light is in the range of 750 nm to 1000 nm. The light receiving unit 13 is a ToF camera.

[0028] The control circuit on the substrate 17 measures information corresponding to the time it takes for the NIR light emitted from the light source unit 11 to return to the light receiving unit 13 after being reflected by the object. This information enables the calculation of the distance from the camera unit 10 to the object and the detection of the three-dimensional shape of the object. The features of the present invention are applicable to camera units different from the NIR-ToF camera unit, which use invisible light with a wavelength different from that of NIR light or adopt different measurement schemes.

[0029] Return Figure 1 , as described above, the camera unit 10 includes a light source unit 11 and a light receiving unit 13. The light receiving unit 13 of the camera unit 10 is placed in a hole 19 provided in the display area 15; the area of the hole 19 is a non-display area. The light source unit 11 is provided in the display area 15. The entire circumference of the hole 19 is surrounded by the display area 15.

[0030] Figure 3 A cross-sectional structure of a part of the liquid crystal display device 1 in an embodiment of the present invention is schematically shown. In Figure 3 , the upper side corresponds to the front side where the viewer or the object of the liquid crystal display device 1 is located. The liquid crystal display device 1 includes a liquid crystal panel 50 and a backlight unit 30 provided behind the liquid crystal panel 50. The liquid crystal display device 1 also includes a light receiving unit 13 and a light source unit 11. As described with reference to Figure 2 , the light receiving unit 13 and the light source unit 11 are included in the camera unit 10.

[0031] The liquid crystal panel 50 can be of any type, such as a twisted nematic (TN) type or an in-plane switching (IPS) type. Examples of the liquid crystal panel 50 include a TFT substrate and a counter substrate facing the TFT substrate. A liquid crystal layer is sandwiched between the TFT substrate and the counter substrate. The TFT substrate includes an insulating substrate that is transparent to visible light. The insulating substrate can have a rectangular shape, and one of the main surfaces faces one of the main surfaces of the counter substrate. A polarizing plate is attached to the other main surface of the insulating substrate that does not face the liquid crystal layer.

[0032] In the case of an IPS liquid crystal panel, pixel electrodes for applying an electric field to the liquid crystal layer and common electrodes are arranged on the TFT substrate. A pair of pixel electrodes and a common electrode apply an electric field to one pixel. The pixel changes the amount of light transmitted therethrough according to the applied electric field. The TFT substrate includes a thin film transistor (TFT) array for selecting the pixel to be controlled.

[0033] In the case of a TN liquid crystal panel, pixel electrodes for applying an electric field to the liquid crystal layer are arranged on the TFT substrate, and common electrodes are provided on the counter substrate. An electric field is applied to the liquid crystal between the pixel electrode and the common electrode of one pixel. The amount of light to be transmitted through the pixel varies according to the applied electric field. The TFT substrate includes a thin film transistor (TFT) array for selecting the pixel to be controlled.

[0034] In the case of a full-color liquid crystal panel, the counter substrate includes a color filter. The counter substrate includes an insulating substrate made of glass or resin. The insulating substrate can have a rectangular shape. A polarizing plate is attached to the main surface of the insulating substrate that does not face the liquid crystal layer.

[0035] Either the TFT substrate or the counter substrate is located on the side closer to the viewer or the front side, and the other is located on the rear side or the back side. That is, the backlight unit 30 is provided behind the TFT substrate or the counter substrate of the liquid crystal panel.

[0036] The backlight unit 30 irradiates the liquid crystal panel 50 from behind the liquid crystal panel 50. The liquid crystal panel 50 displays an image based on the drive signal input thereto. The viewer views the displayed image, which is generated by the light emitted from the backlight unit 30 and transmitted through the liquid crystal panel 50.

[0037] The backlight unit 30 includes a plurality of stacked optical sheets in the chassis 301. For example, the plurality of optical sheets sequentially include a reflection sheet 302, a light guide plate 303, a diffusion sheet 304, a condenser sheet 305, and a two-dimensional condenser sheet 306 from the Figure 3 lower side or the side farther from the liquid crystal panel 50. Each optical sheet includes a functional unit for controlling (diffusing or converging) visible light.

[0038] The sizes of the reflective sheet 302, the light guide plate 303, the diffusion sheet 304, the condenser sheet 305, and the two-dimensional condenser sheet 306 may be larger than the display area 15 of the liquid crystal panel. The reflective sheet 302, the light guide plate 303, the diffusion sheet 304, the condenser sheet 305, and the two-dimensional condenser sheet 306 are also referred to as the optical sheets 302 to 306. When viewed in the stacking direction of the backlight unit 30 and the liquid crystal panel 50, the entire display area 15 overlaps with the optical sheets and may be located inside the outer ends of the optical sheets. One or more of these optical sheets may be smaller than the display area 15.

[0039] The chassis 301 may have a box shape with an open top surface. The optical sheets 302 to 306 are laid one by one on the bottom of the chassis 301. The chassis 301 for accommodating the optical sheets 302 to 306 may be made of metal or resin.

[0040] Each optical sheet may be made of resin and may have any thickness. For example, the reflective sheet 302 may be a polyolefin-based white reflector that effectively reflects visible light. The light guide plate 303 is an optical sheet for obtaining uniform planar visible light and may be made of polycarbonate or polystyrene. Generally, the light guide plate 303 is thicker than other optical sheets, and the thickness may be several millimeters, specifically, in the range of 5 mm to 8 mm. The thickness of other optical sheets may be several tens to several hundreds of micrometers, specifically, in the range of 20 μm to 500 μm.

[0041] The diffusion sheet 304 may have a structure in which acrylic beads are adhered to a polyethylene terephthalate substrate. The condenser sheets 305 and 306 have array prisms on their surfaces to increase the front brightness of the liquid crystal display device. Polyester or polycarbonate may be used for the condenser sheets 305 and 306.

[0042] The types and numbers of the optical sheets included in the backlight unit 30 may be determined as needed and are not limited to the configuration of the present invention. Although Figure 3 An exemplary configuration of an edge-type backlight unit is shown, but a direct backlight unit including light sources arranged in the plane of the liquid crystal panel 50 may be employed. When viewed from the backlight unit 30, the liquid crystal panel 50 is located in the front or the light-emitting side.

[0043] As referred to Figure 1 above, the light receiving unit 13 is placed in the hole 19 provided in the liquid crystal panel 50 and the backlight unit 30. The light receiving unit 13 includes an image sensor 133 mounted on a substrate 17, and the substrate 17 is provided behind the backlight unit 30.

[0044] The image sensor 133 can be a ToF image sensor. The ToF image sensor measures the distance between the ToF image sensor and a point on an object by measuring the time it takes for light emitted from the light source unit 11 to return to the image sensor after being reflected by the point on the object. The type of the image sensor 133 is not limited to a specific type; a one-dimensional sensor can be used instead of the image sensor.

[0045] The light receiving unit 13 further includes a lens unit 130. The lens unit 130 includes a stacked lens 131 disposed in front of the image sensor 133 and a lens barrel 135 for firmly supporting the stacked lens 131. The stacked lens 131 includes a plurality of lenses arranged from the back side (the side closer to the image sensor 133) toward the front. Each lens is fixed to the lens barrel 135.

[0046] In Figure 3 the example of, the image sensor 133 located below the stacked lens 131 is disposed in the lens barrel 135. The stacked lens 131 converges the NIR light reflected by the object onto the image sensor 133. As described above, the lens unit 130 is disposed in the hole in the liquid crystal panel 50 and the backlight unit 30, and neither the liquid crystal panel 50 nor the backlight unit 30 exists in front of the lens unit 130. The lens unit 130 is surrounded by the side wall of the chassis 301 of the backlight unit 30. The side wall of the chassis 301 surrounding the lens unit 130 is optional.

[0047] The light source unit 11 includes a light source 111 and a diffusion sheet 115. The diffusion sheet 115 is an example of a diffusion structure unit. An example of the light source 111 is a vertical cavity surface emitting laser (VCSEL). The VCSEL is a semiconductor laser that emits a laser beam vertically from the top surface (the surface opposite to the substrate 17). The structure of the light source 111 is not limited as long as the light source 111 can emit light with a predetermined intensity forward at a predetermined radiation angle.

[0048] The light source 111 is disposed on the substrate 17 at a position away from the light receiving unit 13, and the substrate 17 is disposed behind the backlight unit 30. The light source 111 is disposed behind the optical sheets 302 to 306 of the backlight unit 30. Specifically, the light source 111 is disposed behind the lowermost reflective sheet 302.

[0049] In Figure 3 the configuration example of, the light source 111 is disposed in the hole provided in the chassis 301. This configuration enables the light from the light source 111 to enter the optical sheet without being blocked by the chassis 301.

[0050] There is no component between the light source 111 and the reflective sheet 302; the NIR light from the light source 111 directly enters the reflective sheet 302. At least a part of the NIR light passes through the optical sheets 302 to 306 of the backlight unit 30 and enters the diffusion sheet 115 of the light source unit 11. Some parts of the NIR light can be absorbed, reflected or diffused by the optical sheets in the backlight unit 30. In Figure 3 In the configuration example, the space between the light source 111 and the diffusion sheet 115 includes a part of all the optical sheets 302 to 306, but does not include any other components.

[0051] The diffusion sheet 115 of the light source unit 11 is arranged to be included in the exit surface of the light source 111 ( Figure 3 the top surface of Figure 3 ) when viewed in the direction of the stacked optical sheets 302 to 306 or in the vertical direction in

[0052] In Figure 3 In the configuration example, the diffusion sheet 115 is arranged between the condenser sheet 306 and the liquid crystal panel 50. The condenser sheet 306 is the uppermost optical sheet in the backlight unit 30. The diffusion sheet 115 can be adhered to the surface of the condenser sheet 306 with an adhesive. The refractive index of the adhesive can be closer to the refractive indices of the diffusion sheet 115 and the condenser sheet 306 and be a value between them. The diffusion sheet 115 can be in contact with the back surface of the liquid crystal panel 50.

[0053] In Figure 3 In the configuration example, a part or the whole of the diffusion sheet 115 overlaps with the display area 15 of the liquid crystal panel 50. This configuration allows the expansion of the display area 15. Arranging the diffusion sheet 115 behind the liquid crystal panel 50 results in a smaller impact on the display in the display area 15. The whole of the diffusion sheet 115 can be located outside the display area 15.

[0054] The area of the diffusion sheet 115 is smaller than that of the optical sheets 302 to 306 of the backlight unit 30, but its area is large enough to receive the light from the light source 111. The diffusion sheet 115 receives the light within at least the range including the half-value width of the center of the light from the light source 111. The diffusion sheet 115 with the minimum area reduces the interference with the display of the liquid crystal panel 50.

[0055] The diffusion sheet 115 uses materials and structures that can effectively diffuse NIR light. The diffusion sheet 115 can be made of resin or glass and has a diffusion structure for diffusing NIR light, such as the structure of a scattering plate or a grating. The diffusion sheet 115 enables the NIR light to be diffused more uniformly. Preferably, the NIR light diffused by the diffusion sheet 115 has an intensity distribution such that objects within the viewing angle of the light receiving unit 13 can be uniformly illuminated.

[0056] Figure 10 An example of the intensity distribution of the light diffused by the diffusion sheet 115 is provided. Figure 10 Including the normal distribution 701 of the intensity of the light diffused by the standard diffusion sheet 115 and the intensity distribution 702 of the light diffused by the preferred diffusion sheet 115. The vertical axis represents the intensity of the diffused NIR light. The horizontal axis represents the angle relative to the optical axis of the incident light. Compared with the normal distribution 701 in which the intensity of the NIR light diffused by the diffusion sheet decreases with the angle relative to its optical axis, the rectangular intensity distribution 702 is preferred, in which the intensity of the NIR light diffused by the diffusion sheet is almost flat within a specific angle.

[0057] The diffusion sheet 115 is allowed to diffuse the NIR light to a wider angle than the optical sheets 302 to 306 of the backlight unit 30 including the diffusion sheet 304. The diffusion sheet 115 is designed to diffuse the light from the light source 111 to the desired angle. The diffusion angle of the diffusion sheet 115 for visible light can be narrower than its diffusion angle for NIR light. This configuration achieves a smaller impact on the display of the liquid crystal panel 50. The diffusion angle of any diffusion sheet of the backlight unit 30 for visible light can be wider than the diffusion angle for NIR light.

[0058] There is an optical sheet of the backlight unit 30 between the diffusion sheet 115 of the light source unit 11 and the exit surface (top surface) of the light source 111; the diffusion sheet 115 is arranged to be away from the light source 111. This configuration makes the diffusion point of the NIR light closer to the viewer and allows the distance between the light source unit 11 and the light receiving unit 13 to be reduced. In Figure 3 the configuration example, the diffusion sheet 115 is arranged at a position farther from the viewer than the top surface (the surface closest to the viewer) of the stacked lens 131, or at a position closer to the substrate 17.

[0059] Hereinafter, the positional relationship between the diffusion sheet 115 of the light source unit 11 and the lens unit 130 is described. Figure 4 It is a diagram showing the positional relationship between the light source unit 11 and the lens unit 130. Figure 4It includes a light source 111, a diffusion sheet 115, a stacked lens 131, and a lens barrel 135. The axis connecting the intersection point between the lower surface of the lens unit 130 and the central axis of the stacked lens 131 and the intersection point between the lower surface of the light source 111 and the optical axis 113 of the light source 111 is defined as the x-axis. The central axis of the stacked lens 131 is defined as the y-axis.

[0060] The light source 111 and the diffusion sheet 115 are arranged such that the light diffused by the diffusion sheet 115 is not blocked by the lens unit 130. As Figure 4 shown, the diffusion angle of the light emitted from the light source 111 and diffused by the diffusion sheet 115 is θ. The camera viewing angle of the lens unit 130 is φ. The height of the lens unit 30 is h, and the outer diameter is 2r. Although the lens unit 130 in this example has a columnar shape, the lens unit can have different shapes. In this case, the distance (the shortest distance) between the central axis of the stacked lens 131 and the point closest to the diffusion sheet 115 in the lens unit 130 can be defined as r.

[0061] In Figure 4 it, the line 331 related to the camera viewing angle φ can be expressed by the following formula:

[0062] y = x * tan((180 – φ) / 2) + h – r * tan((180 – φ) / 2).

[0063] In addition, the line 332 related to the diffusion angle θ of the diffusion sheet 115 can be expressed by the following formula:

[0064] y = -x * 1 / tan(θ / 2) + r / tan(θ / 2) + h.

[0065] The diffusion sheet 115 can be arranged such that the point 333 (x, y) closest to the lens unit 130 thereof is located in a region satisfying the following conditions. If the point 333 of the diffusion sheet 115 is located in a region satisfying the following conditions, the diffused NIR light will not be blocked by the lens unit 130, and the NIR light can be effectively used:

[0066] -x * 1 / tan(θ / 2) + r / tan(θ / 2) + h ≤ y ≤ x * tan((180 – φ) / 2) + h – r * tan((180 – φ) / 2).

[0067] As described above, arranging the diffusion sheet of the light source unit outside the viewing angle of the lens unit and arranging the lens unit outside the diffusion range of the NIR light determined by the diffusion angle θ of the diffusion sheet effectively prevents the light from the light source from being blocked by the lens unit.

[0068] Other embodiments

[0069] Figure 5 Schematically shows a cross-sectional structure of a part of the liquid crystal display device 1 in another embodiment of the present invention. The following mainly describes the differences from Figure 3 the configuration example in Figure 3 The description provided is applicable unless otherwise stated.

[0070] In Figure 5 the configuration example, the diffusion sheet 115 of the light source unit is disposed between the liquid crystal panel 50 and the cover plate 55. The cover plate 55 is disposed in front of the liquid crystal panel 50, and it is a member made of glass or resin. The cover plate 55 transmits visible light and NIR light. Disposing the diffusion sheet 115 in front of the liquid crystal panel 50 enables the light source unit 11 to be disposed closer to the light receiving unit 13. The cover plate 55 prevents the diffusion sheet 115 and the liquid crystal panel 50 from being damaged, but the cover plate 55 is optional.

[0071] Figure 6 Schematically shows a cross-sectional structure of a part of the liquid crystal display device 1 in yet another embodiment of the present invention. Compared with the configuration example in Figure 5 Figure 6 the configuration example in also includes a near-infrared transmission filter (IR filter) 56. The IR filter 56 is disposed in front of the cover plate 55; it transmits NIR light and absorbs visible light. When viewed from the viewer, the IR filter 56 covers the entire light receiving unit 13 and the light source unit 11. The IR filter 56 prevents the viewer from viewing abnormal displays caused by the light receiving unit 13, the light source unit 11, and / or the diffusion sheet 115. Figure 3 The configuration example in can also include an IR filter in front of the liquid crystal panel 50.

[0072] Figure 7 Schematically shows a cross-sectional structure of a part of the liquid crystal display device 1 in yet another embodiment of the present invention. Compared with the configuration example in Figure 5 Figure 7 the configuration example in includes a diffusion sheet 115 disposed in front of the cover plate 55. The rest is the same as the configuration in Figure 5 . The diffusion sheet 115 is disposed on the outermost surface of the liquid crystal display device 1. Increasing the distance between the diffusion sheet 115 and the light source 111 allows the distance between the light receiving unit 13 and the light source unit 11 to be further reduced. The diffusion sheet 115 disposed in front of the cover plate 55 reduces the reflection of NIR light from the back surface of the cover plate 55.

[0073] Figure 8 Schematically shows a cross-sectional structure of a part of the liquid crystal display device 1 in yet another embodiment of the present invention. The following mainly describes the differences from Figure 3 the configuration example in Figure 3The description provided is applicable. Figure 3 Compared to the configuration example in Figure 8 The configuration example in includes the diffusion sheet 115 provided in the optical sheets 302 to 306 of the backlight unit 30 .

[0074] For example, the diffusion sheet 115 may be disposed in a hole provided in one or more optical sheets of the backlight unit 30. The diffusion sheet 115 may be interposed between adjacent optical sheets of the backlight unit 30 and overlap all of the optical sheets 302 to 306 when viewed in the stacking direction.

[0075] Figure 8 The diffusion sheet 115 in the configuration example of FIG. 1 is disposed in a hole provided in the light collecting sheet 305, and is sandwiched between the light collecting sheet 306 and the diffusion sheet 304. The diffusion sheet 115 may be sandwiched between other optical sheets, for example, between the light guide plate 303 and the diffusion sheet 304, or between the light guide plate 303 and the light collecting sheet 305. These configurations can achieve a smaller influence on the display on the liquid crystal panel 50 while increasing the distance between the light source 111 and the diffusion sheet 115.

[0076] Figure 9 The cross-sectional structure of a portion of a liquid crystal display device 1 in another embodiment of the present invention is schematically shown. Figure 3 The configuration example in . Figure 9 In the configuration example, Figure 3 The substrate 17 shown in FIG. 1 is divided into two substrates 171 and 172. The light receiving unit 13 is disposed on the substrate 171, and the light source 111 is disposed on the substrate 172. This configuration increases the flexibility of the arrangement of the light source unit 11 and the light receiving unit 13, and facilitates the assembly of these components. This separate substrate configuration is suitable for Figures 5 to 8 Configuration examples in .

[0077] Each of the light source and the diffusion structure unit included in the light source unit 11 can be configured differently. For example, the NIR light diffusion structure unit can be not only the above-mentioned diffusion sheet 115 that can be set in various positions and can have various shapes, but also a component formed in common with another functional unit. For example, the diffusion structure unit can be set in the insulating substrate or cover plate 55 of the liquid crystal panel 50. In another example, the diffusion structure unit can be set in another functional unit (the other functional unit is in the optical sheet included in the backlight unit 30), for example, in an area other than for the functional unit to converge and diffuse visible light.

[0078] In the foregoing configuration example shown in the figure, the liquid crystal panel 50 has a hole in front of the light receiving unit 13, and the light receiving unit 13 is exposed from the liquid crystal panel 50. In another configuration example, the liquid crystal panel 50 does not have a hole for the light receiving unit 13 and covers the light receiving unit 13. In other words, the entire light receiving unit 13 can overlap with the liquid crystal panel 50 in the stacking direction. For example, Figure 5 or Figure 6 the configuration example in may not have a hole for the light receiving unit 13 in the liquid crystal panel 50, and the light receiving unit 13 is covered not only by the cover plate 55 but also by the liquid crystal panel 50.

[0079] As described above, embodiments of the present invention have been described; however, the present invention is not limited to the above embodiments. Those skilled in the art can easily modify, add, or transform each element in the above embodiments within the scope of the present invention. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment, or the configuration of one embodiment can be incorporated into the configuration of another embodiment.

Claims

1. A liquid crystal display device, comprising: a liquid crystal panel including a display area on which an image is displayed toward a viewer located in front of the liquid crystal display device; A backlight unit, the backlight unit is located behind the liquid crystal panel, and the backlight unit includes a plurality of stacked optical sheets; a light source of invisible light, the light source of invisible light being arranged inside or behind the backlight unit; a diffusion structure unit, the diffusion structure unit is located in front of the light source, and the diffusion structure unit is configured to diffuse the invisible light from the light source; as well as a lens unit configured to focus light diffused by the diffusion structure unit, striking an object, and reflected by the object onto a sensor; wherein the plurality of optical sheets include a diffusion sheet configured to diffuse visible light, The diffusion structure unit is smaller in size than the display area and is selectively disposed at a position illuminated by the invisible light from the light source, and Wherein, at least one optical sheet among the plurality of optical sheets is interposed between the diffusion structure unit and the light source.

2. The liquid crystal display device according to claim 1, in, The diffusion structure unit is arranged outside the viewing angle of the lens unit, and Wherein, the lens unit is arranged outside the range of the diffusion structure unit diffusing the invisible light.

3. The liquid crystal display device according to claim 1, wherein: A part or the whole of the diffusion structure unit overlaps with the display area of ​​the liquid crystal panel.

4. The liquid crystal display device according to claim 1, wherein: The diffusion structure unit is disposed between the liquid crystal panel and the backlight unit.

5. The liquid crystal display device according to claim 1, wherein: All the optical sheets of the backlight unit are interposed between the light source and the liquid crystal panel.

6. The liquid crystal display device according to claim 1, further comprising: a cover plate, the cover plate being arranged in front of the liquid crystal panel, Wherein, the diffusion structure unit is arranged between the liquid crystal panel and the cover plate.

7. The liquid crystal display device according to claim 1, further comprising: a cover plate, the cover plate being arranged in front of the liquid crystal panel, Wherein, the diffusion structure unit is arranged on the front surface of the cover plate.

8. The liquid crystal display device according to claim 1, wherein: The lens unit is disposed in a hole provided in the backlight unit.

9. The liquid crystal display device according to claim 1, wherein: The lens unit is disposed in holes provided in the liquid crystal panel and the backlight unit.

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