Display device with infrared camera for vehicle

Abstract

A display device (10) for a vehicle having an infrared camera is provided with: a display screen (18) having a front side with a display surface (24) and a rear side; the invention relates to a lighting device (10), in particular for a motor vehicle, comprising a light source (38) and a light guide (28), which has a light exit surface (30), a rear surface (32) facing away from the light exit surface, and a circumferential edge surface (34) connecting the front surface to the rear surface (32), the backlight source (38) emitting visible light into at least a partial region of the edge surface (34). There is no optical light diffusion element in an intermediate space between the rear face of the display screen (18) and the light exit face (30) of the light guide (28). The display device (10) is further provided with a reflective film arranged on or opposite the rear face of the light guide (28) for reflecting the backlight (36) and for passing the infrared light, the reflective film having a rear face facing away from the light guide (28), and with an infrared light source (46) and an infrared photodiode array (48), the infrared light source (46) and the infrared photodiode array (48) being arranged on the rear face of the light guide (28). And the infrared light source and the infrared photodiode array are arranged towards the back surface of the reflecting film. The infrared light of the infrared light source (46) passes through the reflective film, the light guide (28) and the display screen (18) and reaches a region in front of the display surface (24), and the infrared light of the infrared light source (46) reflected at an object that may be located in the region passes through the display screen (18), the light guide (28) and the reflective film and reaches the infrared photodiode array (48).

Description

Technical Field

[0001] The invention relates to a display device for a vehicle with an infrared camera and in particular to a display device in which the infrared camera is arranged behind a display surface of a display screen, or in other words, behind a surface of the display device that is typically surrounded, enclosed by a frame of the display screen. Background Art

[0002] It has long been known that in order to improve the safety of a vehicle, the vehicle interior is monitored for possible safety risks. In particular, it is known to detect the driver's face in order to recognize possible driver fatigue as early as possible, for example based on the driver's eyelid movements, and thus to be able to issue a corresponding warning signal.

[0003] For various reasons, the camera used for this should be part of a display device installed in the dashboard. In order to accommodate the camera in the display device, a frame is generally provided, which typically surrounds the display device. However, for optical reasons, there is an increasing trend to make these frames as narrow as possible, so that the space required for accommodating the camera is no longer available in this area. The same applies to the edge region of the display screen itself, which is typically painted black on the display surface.

[0004] It is known that, for example, an infrared camera is arranged behind the display screen and behind the backlight unit. An example of such a solution is described in EP-A-3608147. In this known system, however, two different stacks of "optical films" are used for the infrared camera on the one hand and for the actual display surface on the other hand, which may be undesirable.

[0005] A display device for a vehicle with an infrared camera is known from US Pat. No. 2010 / 0073584, wherein no reflective polarization filter is arranged behind the display screen for backlighting the display screen.

[0006] DE-A-10 2009 002 184 discloses a head-up display in which a projection unit is provided, the projection light of which passes through a reflective polarizing film before reaching the windshield.

[0007] Further display devices are described in DE-A-10 2019 001 333 and DE-A-10 2016 224 246. Summary of the invention

[0008] The object of the present invention is to provide a display device for a vehicle with an infrared camera, in which the structure and arrangement of the individual optical and optoelectronic layers as well as the illumination layers are identical both for the area of ​​the display surface and for the infrared camera.

[0009] In order to achieve the object, the present invention provides a display device for a vehicle having an infrared camera, wherein the display device is provided with:

[0010] - in particular an LCD display having a front side with a display surface and a back side,

[0011] a backlight unit having a backlight source and an optical waveguide, the optical waveguide having a light exit surface, a rear surface facing away from the light exit surface, and a peripheral edge surface connecting the front surface to the rear surface, wherein the backlight source radiates visible light into at least a partial region of the edge surface,

[0012] - wherein no optical light diffusing element is present in the intermediate space between the rear side of the display screen and the light exit surface of the light guide,

[0013] a reflective film arranged on the rear side of the light guide or opposite thereto for reflecting the backlight and letting the infrared light pass, wherein the reflective film has a rear side facing away from the light guide,

[0014] - an infrared light source and an infrared photodiode array, both of which are arranged toward the back side of the reflective film, and

[0015] a first specularly reflective polarizing film arranged on the back side of the display screen or opposite thereto, for reflecting visible backlight, the polarization of which is different from the polarization direction of the rear polarization filter of the display screen, wherein the backlight reflected by the specularly reflective polarizing film can be reflected back by the reflective film in the direction of the specularly reflective polarizing film while changing its polarization direction,

[0016] -Wherein, infrared light passes through an infrared light source reflective film, an optical conductor, a first mirror-reflective polarizing film and a display screen and thereby reaches an area in front of a display surface, and infrared light from the infrared light source reflected on an object that may be in the area passes through the display screen, the first mirror-reflective polarizing film, the optical conductor and the reflective film and thereby reaches an infrared photodiode array.

[0017] The display device according to the invention, which may also have an operating function, typically has a display screen implemented in LCD technology, which has a front side with a display surface and a back side. Behind the display screen, a backlight unit with a light conductor is located, which has a light exit surface, a back side facing away from the light exit surface, and a surrounding edge surface, which connects the front side with the back side. The backlight light source of the backlight unit inputs its visible backlight from the edge surface into the light conductor (edge ​​lighting, edgelit). The light conductor itself is typically designed as a plate or film. There is no optical light diffusion element in the intermediate space between the back side of the display screen and the light exit surface of the light conductor.

[0018] There is a reflective film on the back side facing the light conductor for reflecting backlight and allowing infrared radiation (hereinafter also referred to as infrared light) to pass through, wherein the reflective film that allows infrared light to pass through can also be a component of the back side of the light conductor. The reflective film has a back side that faces away from the light conductor. For example, US 5 233 465 A describes an example of a material that is transparent to infrared radiation and also reflects (visible) light.

[0019] There is an infrared radiation source (hereinafter also referred to as an infrared light source) and an infrared photodiode array (infrared camera) facing the back of the reflective film that allows infrared light to pass. The infrared light of the infrared light source passes through the reflective film, the optical conductor and the display screen and thus reaches the area in front of the display surface. The infrared light is reflected there by an object, such as a hand or a person (observed by the driver), and thus passes through the display screen, the optical conductor and the infrared transparent reflective film to reach the infrared photodiode array.

[0020] According to another feature of the present invention, the display device has a first specular reflective polarizing film arranged on the back of the display screen or arranged opposite thereto, for reflecting visible backlight, the polarization of which is different from the polarization direction of the back polarizing filter of the display screen, wherein the backlight reflected by the specular reflective polarizing film can be reflected back by the reflective film in the direction of the specular reflective polarizing film while changing its polarization direction. The (first) specular reflective polarizing film reflects backlight, the polarization direction of which is inconsistent with the direction predetermined by the back polarizing filter of the display screen. That is, this backlight is reflected and reaches the infrared transparent reflective film, where it is reflected back while changing its polarization direction. This achieves that the light otherwise absorbed by the back polarizing filter can be utilized to backlight the display screen. The specular reflective polarizing film that can be used in this improved scheme of the present invention and in the improved scheme described below is provided by 3M Company of the United States in the form of 3M APF ( 3m-automotive-reflective-polarize-3m-arp-320- tech-data-sheet.pdf ).

[0021] The solution of the display device according to the invention has the advantage that no space is required in the frame or edge area of ​​the display device for accommodating the infrared camera, that is, the size of the display surface can be maximized, wherein the backlight intensity of the display is still affected although the entire display device, i.e. the display and the backlight unit for the infrared light, must be transparent.

[0022] Thin light-conducting films with minimal prismatic structures are particularly suitable for use as light conductors in backlight units. Such light conductor films are sold, for example, by the Finnish company Nanocomp Oy (https: / / www.nanocomp.fi / wp- content / uploads / 2022 / 04 / nanocompdirectionallightguidefilmlowres4-2022.pdf ).

[0023] However, it is also possible to arrange such a light-conducting film by optical bonding on a conventional light guide body whose light exit surface has no structure.

[0024] The light-guiding film results in an optimal homogenization of the backlight, without the need for additional light-diffusing elements, which are typically arranged between the backlight unit and the display screen.

[0025] In another advantageous design of the present invention, the first specular reflective polarizing film also reflects infrared light, the polarization of which is different from the polarization direction of the back polarizing filter of the display screen, wherein an infrared reflective film is arranged below the infrared light source for reflecting the infrared light reflected by the first specular reflective polarizing film while changing the polarization direction. That is, the specular reflective polarizing film can also be used to improve the utilization rate of infrared light in this way.

[0026] It is expedient to arrange a second specular reflective polarizing film on the back side of the infrared transparent reflective film or opposite to it for reflecting infrared light, the polarization of which is different from the polarization direction of the back polarizing filter of the display screen, wherein an infrared reflective film is arranged below the infrared light source for reflecting the infrared light reflected by the second specular reflective polarizing film while changing the polarization direction. That is, the second specular reflective polarizing film is used to improve the infrared light output efficiency in this embodiment.

[0027] Typically, the infrared light source emits near-infrared light, wherein the infrared photodiode array is correspondingly a near-infrared photodiode array. The photodiode array can be designed in principle in one dimension or in two dimensions.

[0028] As already provided above, if a touch sensor system is integrated accordingly, which can be realized by a touch panel, for example, the display surface of the display screen can also be used to input commands by touching the display surface.

[0029] Finally, an optical lens for the infrared beam may be arranged between the infrared transparent reflective film and the infrared photodiode array.

[0030] According to an advantageous design of the present invention, it can be provided that a diffusion layer for scattering backlight is present in the intermediate space between the light exit surface of the optical conductor and the back side of the display screen, and the infrared light of the infrared light source passes through without scattering. According to another advantageous design of the present invention, it can be provided that a diffusion layer neutral to infrared light is arranged between the optical conductor and the mirror-reflective polarizing film or between the mirror-reflective polarizing film and the display screen. The advantage of the infrared-light-neutral diffusion layer is that although the backlight is scattered, the infrared light is not scattered. The latter is particularly advantageous for infrared light shooting by an infrared camera.

[0031] In other words, the invention is characterized by the uniqueness of the backlight unit, which ensures that the display screen is bright enough and is thus backlit with the required light intensity and uniformity, wherein at the same time infrared light reaches the camera through the display screen without causing blurred, double-image images. Rather, the infrared image is clear enough to be able to extract the necessary information from it by processing or processing.

[0032] This also applies to the input of infrared light, as is the case with the edge lighting concept for backlighting displays with visible light. Behind the infrared-transparent reflective film there is a light guide that applies infrared light from the side, deflects the infrared light and impinges on the infrared-transparent reflective film from behind.

[0033] In order that the infrared light can reach the infrared photodiode array, for example as scattered light, it is expedient if the infrared photodiode array is optically isolated from the infrared light source or the aforementioned infrared light guide.

[0034] In the variants of the invention described so far, there is no light-scattering diffuser in the intermediate space between the light exit surface of the light guide and the back of the display screen. However, the diffuser is advantageous if it only scatters the backlight. Diffuser films are known in the prior art, which can scatter the light or allow it to pass without scattering, depending on its wavelength. Reference is made here to:

[0035] https: / / onlinelibrary.wiley.com / doi / full / 10.1002 / adma.202105868 .

[0036] It is now advantageous to arrange such a diffuser that operates according to the light wavelength in the intermediate space between the light exit surface of the light guide and the back side of the display screen, which diffuser scatters the backlight and lets the infrared light of the infrared light source pass without scattering. Such a diffuser that is "neutral" with respect to infrared light can be arranged between the specularly reflective polarizing film and the display screen or light guide if a specularly reflective polarizing film is present. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The present invention will be specifically described below with reference to the embodiments of the aforementioned first variant of the present invention and with reference to the accompanying drawings. Shown in detail herein:

[0038] Figure 1 An example of application of a display device according to an embodiment of the present invention is shown.

[0039] Figure 2 a first example of an optical stack for a display device is shown (very schematically), and

[0040] Figure 3 A second example of an optical stack for a display device is shown (very schematically). DETAILED DESCRIPTION

[0041] Figure 1 An example of application of a display device 10 according to the invention is shown, which has an infrared camera 12 arranged behind the display device. In this embodiment, both are arranged in the dashboard 14 of the vehicle, wherein the infrared camera 12 is pointed toward the driver 16. The information extracted from the camera image is application-specific and known in principle, so that no further detailed explanation is required within the scope of the invention.

[0042] Figure 2 A first exemplary embodiment of individual optical and optoelectronic layers of the display device 10 is shown very schematically, wherein neither the thickness of the individual layers nor the distances between the individual layers are drawn to scale.

[0043] exist Figure 2 In the embodiment of the embodiment of the present invention, the display device 10 has, for example, an LCD display screen 18 with a touch sensor device 20, which is arranged behind a cover glass 22. That is, the display device 10 is also used in this embodiment to input commands by touching the display surface 24.

[0044] Behind the display screen 18 there is a backlight unit 26 for backlighting the display screen 18 with visible light. For this purpose, the backlight unit 26 has a light conductor 28, which has a light exit surface 30 facing the display screen 18 and a back side 32 facing away from the light exit surface. The two faces or main faces of the light conductor 28 are connected to each other by a surrounding edge surface 34. The backlight 36 is radiated into a partial area of ​​the edge surface 34, which is achieved by means of a plurality of backlight light sources 38, for example in the form of LEDs. On the light exit surface 30 there is an additional light guide film 40, which has a light prism structure of minimal size. The light guide film 40 is provided, for example, by the Finnish company Nanocomp Oy.

[0045] According to the present invention, there is no light diffusion film or light diffusion element between the backlight unit 26 and the display screen 18, because such elements are not favorable for infrared light, which will be further explained below.

[0046] Below the light conductor 28 , ie towards its rear side 32 , there is an infrared-transparent reflective film 42 , which likewise belongs to the backlight unit 26 . The reflective film ensures that the backlight is reflected in the direction of the display screen 18 .

[0047] An infrared light source 46, for example in the form of an LED, is located toward the back side 44 of the infrared-transparent reflective film 42. In addition, an infrared camera 12, for example in the form of an infrared photodiode array 48, is also located toward the back side 44 of the infrared-transparent reflective film 42.

[0048] Likewise optionally, but advantageously, a diffuser layer 59 neutral to infrared light is provided between the light conductor 28 and the (first) specularly reflective polarizing film 50 or between the specularly reflective polarizing film and the display screen 18, the diffuser layer scattering the backlight but allowing the infrared light to pass without scattering. This makes the backlighting of the display screen 18 homogenized, while the infrared light reaching the area in front of the display screen 18 or in front of its cover glass 22 or the infrared light possibly reflected there is not scattered, which is advantageous for infrared recording by the infrared camera 48.

[0049] Between the backlight unit 26 and the back of the display screen 18, there is a (first) specularly reflective polarizing film 50, which reflects the backlight in a polarization direction that is different from the polarization direction predetermined by the back polarizing film 52 of the display screen 18 (the front polarizing film of the display screen 18 is not shown for simplicity), more precisely, the backlight is reflected in the direction of the infrared transparent reflective film 42, where it is reflected back again with its polarization direction changed. This is shown by arrows 54, 56 and 58. By means of the measures described, almost the entire part of the backlight source 38, also the backlight, can be used to backlight the display screen 18.

[0050] The (first) specular reflective polarizing film 50 can also be used to reflect back the infrared light 46 of the infrared light source, the polarization direction of which is different from the direction predetermined by the rear polarizing film 52 of the display screen. However, a reflective film for infrared light is also required for this purpose, which is Figure 2 Not yet shown.

[0051] Alternatively, however, a laser diode may also be used as an infrared light source, which laser diode emits only light having a polarization direction corresponding to the polarization direction of rear polarization film 52 of display screen 18 .

[0052] exist Figure 2In the embodiment of the “optical stack”, the light-guiding film 40 and the (first) specularly reflective polarizing film 50 are optional; that is, these two layers may also be eliminated.

[0053] The light from the infrared light source 46 passes through the backlight unit 26 and continues through the display screen, the touch sensor device and the cover glass to reach the following area of ​​the display device 10, in which the light is reflected on an object to be monitored or detected that may be located there, so as to be finally captured as a reflected image by the infrared camera 12.

[0054] Likewise optionally, but advantageously, a diffuser layer 59 neutral to infrared light is provided between the light conductor 28 and the (first) specularly reflective polarizing film 50 or between the specularly reflective polarizing film and the display screen 18, the diffuser layer scatters the backlight but allows the infrared light to pass without scattering. This makes the backlighting of the display screen 18 homogenized, while the infrared light that reaches the area in front of the display screen 18 or in front of its cover glass 22 and the infrared light that may be reflected therefrom are not scattered, which is advantageous for infrared recording by the infrared camera 48.

[0055] exist Figure 3 The figure shows the situation described above, in which the optical stack of the display device 10 has a layer that ensures reflection of infrared light, wherein the infrared light has the following polarization direction, which is different from the direction predetermined by the back polarizing film 52 of the display screen 18, thereby improving the infrared light output efficiency. Figure 3 Zhongyu Figure 2 The same layers and components in Figure 3 There are Figure 2 The same reference numerals are used in the drawings.

[0056] The light from the infrared light source 46 is reflected on the second specular reflective polarizing film 60 in a polarization direction that does not match the back polarizing film 52, and reaches, for example, an infrared reflective film 62 arranged below the infrared light source 46. The infrared light reflected back therefrom is directed toward the second specular reflective polarizing film 60 again with its polarization direction changed, and when the polarization direction is correct, it passes through the second specular reflective polarizing film (the above situation is Figure 3 The infrared light is reflected by the object to be observed or detected so as to be captured by the infrared camera 12.

[0057] List of Reference Numerals

[0058] 10 Display device

[0059] 12 Infrared Camera

[0060] 14 Dashboard

[0061] 16 Driver

[0062] 18 Display

[0063] 20 Touch sensor device

[0064] 22 Cover glass

[0065] 24 Display surface

[0066] 26 Backlight unit

[0067] 28 Photoconductor

[0068] 30 Light exit surface

[0069] 32 Back side of the light conductor

[0070] 34 Edge surface of light conductor

[0071] 36 Backlight

[0072] 38 Backlight source

[0073] 40 Light guide film

[0074] 42 Infrared transparent reflective film

[0075] 44 The back of infrared transparent reflective film

[0076] 46 Infrared light source

[0077] 48 Infrared Photodiode Array

[0078] 50 First Specular Reflective Polarizing Film

[0079] 52 Display back polarizing film

[0080] 54 Arrow

[0081] 56 Arrow

[0082] 58 Arrow

[0083] 59 IR neutral diffuser for backlighting

[0084] 60 Second mirror reflective polarizing film

[0085] 62 Infrared reflective film

[0086] 64 Arrow

[0087] 66 Arrow

[0088] 68 Arrows.

Claims

1. A display device with an infrared camera for a vehicle, comprising: a display screen (18) having a front side with a display surface (24) and a rear side, - a backlight unit (26) comprising a backlight light source (38) and a light conductor (28), the light conductor having a light exit surface (30), a rear surface (32) facing away from the light exit surface, and a peripheral edge surface (34) connecting the front surface to the rear surface (32), wherein: The backlight source (38) emits visible light into at least a partial region of the edge surface (34). - wherein no optical light diffusing element is present in the intermediate space between the rear side of the display screen (18) and the light exit surface (30) of the light conductor (28), a reflective film (42) arranged on the rear side of the optical waveguide (28) or opposite thereto for reflecting the backlight (36) and for letting infrared light pass through, wherein the reflective film (42) has a rear side facing away from the optical waveguide (28), - an infrared light source (46) and an infrared photodiode array (48), both of which are arranged toward the back side of the reflective film (42), and a first specularly reflective polarizing film (50) arranged on the back side of the display screen (18) or opposite thereto, for reflecting visible backlight (36), the polarization of which is different from the polarization direction of the rear polarizing filter of the display screen (18), wherein the backlight (36) reflected by the specularly reflective polarizing film (50) can be reflected back by the reflective film (42) in the direction of the specularly reflective polarizing film (50) while changing its polarization direction, - wherein the infrared light of the infrared light source (46) passes through the reflective film (42), the optical conductor (28), the first mirror-reflective polarizing film (50) and the display screen (18) and thereby reaches the area in front of the display surface (24), and the infrared light of the infrared light source (46) reflected on an object that may be in the area passes through the display screen (18), the first mirror-reflective polarizing film (50), the optical conductor (28) and the reflective film (42) and thereby reaches the infrared photodiode array (48).

2. The display device according to claim 1, characterized in that The light conductor (28) is designed as a light guide film (40).

3. The display device according to claim 1, characterized in that The optical conductor (28) comprises a light guide film (40) and a light guide plate, wherein the light guide film and the light guide plate are connected to each other via an optical adhesive layer.

4. The display device according to any one of claims 1 to 3, characterized in that: The first mirror-reflective polarizing film (50) also reflects infrared light, the polarization of which is different from the polarization direction of the rear polarizing filter of the display screen (18), and an infrared reflecting film (62) is arranged below the infrared light source (46) for reflecting the infrared light reflected by the first mirror-reflective polarizing film (50) while changing the polarization direction.

5. The display device according to any one of claims 1 to 4, characterized in that: A second specular reflective polarizing film (60) is arranged on the back side of the reflective film (42) or opposite to it, and is used to reflect infrared light, wherein the polarization of the infrared light is different from the polarization direction of the rear polarizing filter of the display screen (18); and an infrared reflective film (62) is arranged below the infrared light source (46), and is used to reflect the infrared light reflected by the second specular reflective polarizing film (60) while changing the polarization direction.

6. The display device according to any one of claims 1 to 5, characterized in that: The infrared light source (46) emits near-infrared light, and the infrared photodiode array is a near-infrared photodiode array.

7. The display device according to any one of claims 1 to 6, characterized in that: The infrared photodiode array (48) is two-dimensional.

8. The display device according to any one of claims 1 to 7, characterized in that: A touch panel is provided for manually inputting instructions by touching a display surface (24) of the display screen (18).

9. The display device according to any one of claims 1 to 8, characterized in that: At least one optical lens is provided and arranged between the reflective film (42) and the infrared photodiode array (48).

10. The display device according to any one of claims 1 to 9, characterized in that: A diffusion layer (59) for scattering backlight is present in the intermediate space between the light exit surface of the optical waveguide (28) and the back side of the display screen (18), and the diffusion layer allows infrared light from the infrared light source (46) to pass through without scattering.

11. The display device according to claim 10, characterized in that: A diffuser layer (59) neutral to infrared light is arranged between the optical waveguide (28) and the specularly reflective polarizing film (50) or between the specularly reflective polarizing film (50) and the display screen (18).

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