Display device with an ir camera for a vehicle
Patent Information
- Application Number
- EP2023773260
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-14
- Filing Date
- 2023-09-19
- Publication Date
- 2025-07-30
AI Technical Summary
Existing display devices for vehicles with integrated IR cameras face challenges in accommodating the camera due to the trend of narrowing frames and edge areas, which limits the space for optical components, and often require separate optical films for the IR camera and display, affecting optical efficiency.
A display device design where the IR camera is integrated behind the display with a shared optical and opto-electronic structure, utilizing a backlighting unit with a light guide, an IR-transparent reflection film, and mirror reflection polarization films to reflect visible and IR light efficiently, ensuring maximum display area and optimal light intensity without scattering IR light.
This design maximizes the display area by eliminating the need for additional space for the IR camera, maintains sufficient backlighting intensity and homogeneity, and provides a sharp IR image for accurate monitoring, while ensuring that IR light is not scattered, thus enhancing safety features like driver fatigue detection.
Smart Images
Figure 1.1
Abstract
Description
[0001] Display device with IR camera for a vehicle
[0002] The invention relates to a display device with an IR camera for a vehicle and in particular to a display device in which the IR camera is arranged behind the display surface of the display or, in other words, behind that surface of the display device which is enclosed by a frame which typically surrounds the display.
[0003] To increase vehicle safety, it has long been known to monitor the vehicle interior for potential safety risks. In particular, it is known to capture the driver's face, for example, based on eyelid movement, to detect possible driver fatigue early on and then issue an appropriate alarm signal.
[0004] For various reasons, the cameras used for this purpose should be integrated into displays installed in the instrument panel. The frame that typically surrounds the display is generally the ideal location for accommodating the cameras in such displays. However, for aesthetic reasons, the trend is increasingly toward making these frames as narrow as possible, so that there is no longer enough space in this area to accommodate the camera. The same applies to the edge of the display itself, which is typically colored black near the display surface.
[0005] It is known, for example, to arrange IR cameras behind the display and behind its backlight unit. An example of such a concept is described in EP-A-3 608 147. However, this known system uses two different stacks of "optical films" for the IR camera and the actual display surface, which can be undesirable.
[0006] From US-A-2010 / 0073584 a display device with an IR camera for a vehicle is known, in which no reflection polarization filter intended for the backlighting light illuminating the display is arranged behind the display.
[0007] 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 polarization film before reaching the windshield.
[0008] Further display devices are described in DE-A-10 2019 001 333 and DE-A-10 2016 224 246.
[0009] The object of the invention is to provide a display device with an IR camera for a vehicle, in which the structure and arrangement of the individual optical and opto-electronic as well as illumination layers are the same for both the area of the display surface and for the IR camera.
[0010] To achieve this object, the invention proposes a display device with an IR camera for a vehicle, wherein the display device is provided with an LCD display, in particular, which has a front side with a display surface and a rear side, a backlight unit with backlight light sources and with a light guide, which has a light exit side, a rear side facing away from the latter and a circumferential edge side connecting the front side to the rear side, wherein the backlight light sources radiate visible light into at least a partial area of the edge side, wherein the space between the rear side of the display and the light exit side of the light guide is free of optical light diffusion elements, a reflective film arranged on the rear side of the light guide or opposite thereto for reflecting backlight light and for transmitting IR light,wherein the reflective film has a back side facing away from the light guide,
[0011] IR light sources and an IR photodiode array, all of which are arranged facing the back of the reflective film, and a first mirror-reflective polarizing film arranged on the back of the display or opposite it for reflecting visible backlighting light whose polarization deviates from the polarization direction of the rear polarizing filter of the display, wherein backlighting light reflected by the mirror-reflective polarizing film can be reflected back by the reflective film with a change in its polarization direction towards the mirror-reflective polarizing film, wherein IR light from the IR light sources passes through the reflective film, the light guide, the first mirror-reflective polarizing film and the display and thus reaches an area in front of the display surface, and IR light from the IR light sources reflected by an object potentially located in this area illuminates the display,passes through the first mirror reflection polarization film, the light guide and the reflection film and thus reaches the IR photodiode array.
[0012] The display device according to the invention, which can also have an operating function if required, has a display typically designed using LCD technology, which has a front side with a display surface and a rear side. Behind the display is the backlighting unit with a light guide, which has a light exit side, a rear side facing away from this, and a surrounding edge side that connects the front to the rear. The backlighting light sources of the backlighting unit feed their visible backlighting light into the edge of the light guide (edge lit). The light guide itself is typically designed as a plate or thin film. There are no optical light diffuser elements in the space between the rear of the display and the light exit side of the light guide.
[0013] Facing the back of the light guide is a reflective film for reflecting backlighting light and transmitting IR radiation (hereinafter also referred to as IR light). This IR-transparent reflective film can also be part of the back of the light guide. The reflective film has a back side facing away from the light guide. An example of a film that is transparent to IR radiation and otherwise (visible)
[0014] Light-reflecting material is described, for example, in US 5 233 465 A.
[0015] Facing the back of this IR-transparent reflective film are IR radiation sources (hereinafter also referred to as IR light sources) and an IR photodiode array (as an IR camera). The IR light from the IR light sources passes through the reflective film, the light guide, and the display, reaching an area in front of the display surface. There, it is reflected by an object, such as a hand or a person (driver observation), and thus passes through the display, the light guide, and the IR-transparent reflective film to the IR photodiode array.
[0016] According to a further feature of the invention, the display device comprises a first specular reflection polarization film arranged on the rear of the display or opposite thereto for reflecting visible backlight light whose polarization deviates from the polarization direction of the rear polarization filter of the display. Backlight light reflected by the specular reflection polarization film can be reflected back by the reflection film, changing its polarization direction, toward the specular reflection polarization film. This (first) specular reflection polarization film reflects backlight light whose polarization direction does not coincide with the direction specified for the display by the rear polarization filter.Such backlighting light is reflected and reaches the IR-transparent reflective film, where it is reflected back again, changing its polarization direction. This ensures that light otherwise absorbed by the rear polarization filter can be used to backlight the display. A mirror-reflective polarization film that can be used in this and the further developments of the invention described below is offered by the US company 3M under the designation 3M APF (3m-automotive-reflective-320-tech-data-sheet.Ddf).
[0017] The inventive concept of the display device has the advantage that no space is required in the frame or edge area of the display device for accommodating the IR camera, thus the size of the display area can be maximized, whereby the backlight intensity of the display is impaired, although the entire display device, ie the display and the backlight unit, must be transparent to IR light.
[0018] A thin light guide film with a minimal prism structure is particularly suitable as a light guide for the backlight unit. Such light guide films are marketed, for example, by the Finnish company Nanocomp Oy (http: / / www.nanocomD.fi / wD-content / uDloads / 2022 / 04 / nanocomp directional light guide film lowres 4- 2022.pdf).
[0019] However, it is also possible for such a light guide film to be arranged by optical bonding on a conventional light guide whose light exit side has no structure whatsoever.
[0020] This light guide film ensures optimal homogenization of the backlight light without the need for additional light diffusion elements, which are typically arranged between the backlight unit and the display.
[0021] In a further advantageous embodiment of the invention, the first mirror-reflective polarizing film also reflects IR light whose polarization deviates from the polarization direction of the rear polarizing filter of the display. An IR-reflective film is arranged below the IR light sources to reflect the IR light reflected by the first mirror-reflective polarizing film while changing the polarization direction. In this way, the mirror-reflective polarizing film can also be used to increase the utilization of IR light.
[0022] It may be expedient to arrange a second mirror-reflective polarizing film on the back of the IR-transparent reflective film or opposite it for reflecting IR light whose polarization differs from the polarization direction of the rear polarizing filter of the display. An IR reflective film is arranged below the IR light sources for reflecting IR light reflected by the second mirror-reflective polarizing film while changing the polarization direction. Thus, in this embodiment, the second mirror-reflective polarizing film serves to improve IR light yield.
[0023] Typically, IR light sources emit NIR light, so the IR photodiode array is a NIR photodiode array. The photodiode array can generally be one- or two-dimensional.
[0024] As already explained above, the display surface can also be used to enter commands by touching the display surface if a touch sensor is integrated accordingly, such as can be achieved by a touch panel.
[0025] Finally, an optical lens for IR radiation can be arranged between the IR-transparent reflection film and the IR photodiode array.
[0026] According to an advantageous embodiment of the invention, a diffuser layer for scattering the backlighting light can be located in the space between the light exit side of the light guide and the back of the display, which diffuser layer allows the IR light from the IR light sources to pass through without scattering. According to a further advantageous embodiment of the invention, the diffuser layer, which is neutral for IR light, can be arranged between the light guide and the mirror-reflective polarizing film or between the mirror-reflective polarizing film and the display. The advantage of the IR-neutral diffuser layer is that, although the backlighting light is scattered, the IR light is not scattered. The latter is particularly advantageous for the IR light recording by the IR camera.
[0027] The invention is characterized by the special features of the backlight unit, which ensures that the display is backlit sufficiently brightly and thus with the required light intensity and homogeneity. At the same time, IR light passes through the display to the camera without resulting in a blurred or fuzzy image. Rather, the IR image is sufficiently sharp to allow the necessary information to be extracted from the IR image through processing.
[0028] Just as an edge-lit design is used for backlighting the display with visible light, this can also be used for the IR light input. Behind the IR-transparent reflective film is a light guide exposed to IR light from the side, which redirects the IR light and projects it onto the IR-transparent reflective film from behind.
[0029] In order for the IR light to reach the IR photodiode array as, for example, scattered light, it is advisable to optically shield the IR photodiode array from the IR light sources or the previously described I light guide.
[0030] In the variant of the invention described so far, there is no light-scattering diffuser in the space between the light exit side of the light guide and the back of the display. However, such a diffuser would be advantageous if it only scattered the backlight light. Diffuser films are known in the prior art that, depending on the wavelength of the light, scatter it or transmit it without scattering. In this context, reference is made to http: / / onlinelibrarv.wilev.com / doi / full / 10.1002 / adma.202105868.
[0031] It is advantageous if a wavelength-dependent diffuser is arranged in the space between the light exit side of the light guide and the back of the display. This diffuser scatters the backlight light and allows the IR light from the IR light sources to pass through without scattering. This diffuser, which is "neutral" for IR light, can be arranged between the mirror-reflective polarization film and either the display or the light guide if the mirror-reflective polarization film is present.
[0032] The invention will be explained in more detail below using an exemplary embodiment of the first variant of the invention described above and with reference to the drawing. In detail: Fig. 1 shows an example of the application of the display device according to an exemplary embodiment of the invention,
[0033] Fig. 2 shows a first example of the optical layer stack of the display device (highly schematic) and
[0034] Fig. 3 shows a second example of the optical layer stack of the display device (highly schematic).
[0035] Fig. 1 shows an application example for the display device 10 according to the invention with an IR camera 12 arranged behind it. In this exemplary embodiment, both are arranged in the instrument panel 14 of a vehicle, with the IR camera 12 directed at the driver 16. The information extracted from the camera image is application-specific and generally known, which is why it need not be discussed in more detail within the scope of this invention.
[0036] Fig. 2 shows a highly schematic view of a first embodiment of the individual optical and opto-electronic layers of the display device 10, wherein neither the thickness of the individual layers nor their spacings are to scale.
[0037] In the embodiment of Fig. 2, the display device 10 comprises, for example, an LCD display 18 with a touch sensor 20 arranged behind a cover glass 22. In this embodiment, the display device 10 also serves to input commands by touching the display surface 24.
[0038] Behind the display 18 is a backlighting unit 26 for backlighting the display 18 with visible light. For this purpose, the backlighting unit 26 has a light guide 28, which has a light exit side 30 facing the display 18 and a rear side 32 facing away from this. Both sides or main surfaces of the light guide 28 are connected to one another by a circumferential edge side 34. The backlighting light 36 is radiated into a partial area of this edge side 34, which is realized with several backlighting light sources 38 in the form of LEDs, for example. On the light exit side 30 there is an additional light guide film 40, which has a minimally sized light prism structure. This light guide film 40 is offered, for example, by the Finnish company Nanocomp Oy.
[0039] According to the invention, there are no light diffuser films or similar elements between the backlight unit 26 and the display 18, since such elements would be detrimental to the IR light, which will be discussed further below.
[0040] Below the light guide 28, namely facing its rear side 32, is an IR-transparent reflection film 42, which also belongs to the backlight unit 26. This reflection film ensures the reflection of backlight light toward the display 18.
[0041] IR light sources 46, such as LEDs, are located facing the back side 44 of the IR-transparent reflection film 42. Furthermore, the IR camera 12, such as an IR photodiode array 48, is also located facing the back side 44 of the IR-transparent reflection film 42.
[0042] It is also optional, but advantageous, to provide a diffuser layer 59 that is neutral to IR light between the light guide 28 and the (first) mirror-reflective polarization film 50, or between the latter and the display 18. This diffuser layer scatters the backlighting light but allows the IR light to pass through without scattering. This homogenizes the backlighting of the display 18 without scattering either the IR light reaching the area in front of the display 18 or its cover glass 22, or the IR light potentially reflected from there, which is advantageous with regard to IR recording by the IR camera 48.Between the backlight unit 26 and the rear of the display 18 is a (first) mirror-reflective polarization film 50, which reflects backlight light with a polarization direction that deviates from the polarization direction specified by the rear polarization film 52 (for the sake of clarity, the front polarization film of the display 18 is not shown) of the display 18. This reflects the backlight light in the direction of the IR-transparent reflection film 42, where the backlight light is reflected back again, changing its polarization direction. This is indicated by the arrows 54, 56, and 58. This measure ensures that almost the entire proportion of backlight light from the backlight light sources 38 can also be used for backlighting the display 18.
[0043] The (first) mirror-reflective polarizing film 50 can also be used to reflect back the IR light from the IR light sources 46 whose polarization direction deviates from that of the rear polarizing film 52 of the display. However, this would require a reflection film for IR light, which is not yet shown in Fig. 2.
[0044] Alternatively, laser diodes can also be used as IR light sources, which emit only light with a polarization direction corresponding to that of the rear polarization film 52 of the display 18.
[0045] In the embodiment of the "optical stack" of Fig. 2, the light guide film 40 and the (first) mirror reflection polarization film 50 are optional; both layers could therefore be omitted.
[0046] The light from the IR light sources 46 passes through the backlight unit 26 and further through the display, the touch sensor system and the cover glass into the area in front of the display device 10, where it is reflected by objects potentially to be monitored or detected located there, in order to ultimately be recorded as a reflection image by the IR camera 12. It is also optional, but advantageous, to provide a diffuser layer 59 that is neutral for IR light between the light guide 28 and the (first) mirror reflection polarization film 50 or between this and the display 18. This diffuser layer 59 scatters the backlight light but allows the IR light to pass through without scattering. This homogenizes the backlighting of the display 18 without affecting the light in the area in front of the display 18 or the mirror reflection polarization film 50.in front of the cover glass 22, the IR light potentially reflected from there is scattered, which is advantageous with regard to the IR recording by the IR camera 48.
[0047] Fig. 3 graphically illustrates the previously discussed case in which the optical stack of the display device 10 comprises layers that provide for the reflection of IR light having a polarization direction that deviates from that predetermined by the rear polarizing film 52 of the display 18, namely to increase the IR light yield. Those layers and elements in Fig. 3 that are identical to those in Fig. 2 are provided with the same reference numerals in Fig. 3 as in Fig. 2.
[0048] The light from the IR light sources 46 is reflected by a second mirror-reflective polarizing film 60 if the polarization direction does not match the rear-side polarizing film 52 and reaches an IR reflection film 62, which is arranged, for example, below the IR light sources 46. IR light reflected from there, with its polarization direction changing, travels back toward the second mirror-reflective polarizing film 60 and, with the correct polarization direction, through it (the above is indicated in Fig. 3 by arrows 64, 66, and 68) and into the area in front of the display device 10, where it is reflected back by an object to be observed or detected to be recorded by the IR camera 12. LIST OF REFERENCE SYMBOLS
[0049] Display device
[0050] IR camera
[0051] instrument panel
[0052] driver
[0053] Display
[0054] Touch sensors
[0055] Cover glass
[0056] Display area
[0057] Backlight unit
[0058] light guide
[0059] Light exit side
[0060] Back of the light guide
[0061] Edge of the light guide
[0062] Backlight light
[0063] Backlight light source
[0064] Fiber optic film
[0065] IR-transparent reflective film
[0066] Back of the IR-transparent reflection film
[0067] IR light sources
[0068] IR photodiode array first mirror reflection polarization film in the back polarization film of the display
[0069] Arrow
[0070] Arrow
[0071] Arrow
[0072] IR light neutral diffuser layer for backlight light second mirror reflection polarization film
[0073] IR reflection film
[0074] Arrow
[0075] Arrow
[0076] Arrow
Claims
CLAIMS A device with an IR camera for a vehicle, comprising a display (18) having a front side with a display surface (24) and a rear side, a backlighting unit (26) with backlighting light sources (38), and a light guide (28) having a light exit side (30), a rear side (32) facing away from the latter, and a circumferential edge side (34) connecting the front side to the rear side (32), wherein the backlighting light sources (38) radiate visible light into at least a partial area of the edge side (34), wherein the space between the rear side of the display (18) and the light exit side (30) of the light guide (28) is free of optical light diffusion elements, a reflection film (42) arranged on the rear side of the light guide (28) or opposite thereto for reflecting backlighting light (36) and for transmitting IR light,wherein the reflection film (42) has a rear side facing away from the light guide (28), IR light sources (46) and an IR photodiode array (48), all of which are arranged facing the back of the reflection film (42), and a first mirror reflection polarization film (50) arranged on the back of the display (18) or opposite thereto for reflecting visible backlighting light (36), the polarization of which deviates from the polarization direction of the rear polarization filter of the display (18), wherein backlighting light (36) reflected by the mirror reflection polarization film (50) can be reflected back by the reflection film (42) with a change in its polarization direction in the direction of the mirror reflection polarization film (50), wherein IR light of the IR light sources (46) passes through the reflection film (42), the light guide (28), the first mirror reflection polarization film (50) and the display (18) and thus into an area before the arrival display surface (24) and IR light from the IR light sources (46) reflected by an object potentially located in this area passes through the display (18), the first mirror-reflective polarization film (50), the light guide (28) and the reflection film (42) and thus reaches the IR photodiode array (48). Display device according to claim 1, characterized in that the light guide (28) is designed as a light guide film (40). Display device according to claim 1, characterized in that the light guide (28) has a light guide film (40) and a light guide plate, which are bonded to one another by an optical adhesive layer.Display device according to one of claims 1 to 3, characterized in that the first mirror reflection polarization film (50) also reflects IR light whose polarization deviates from the polarization direction of the rear polarization filter of the display (18), and that an IR reflection film (62) is arranged below the IR light sources (46) for reflecting IR light reflected by the first mirror reflection polarization film (50) while changing the polarization direction.Display device according to one of claims 1 to 4, characterized by a second mirror reflection polarization film (60) arranged on the back of the reflection film (42) or opposite it for reflecting IR light whose polarization deviates from the polarization direction of the rear polarization filter of the display (18), and an IR reflection film (62) arranged below the IR light sources (46) for reflecting IR light reflected by the second mirror reflection polarization film (60) with a change in the polarization direction. Display device according to one of claims 1 to 5, characterized in that the IR light sources (46) emit NIR light and that the IR photodiode array is an NIR photodiode array. Display device according to one of claims 1 to 6, characterized in that the IR photodiode array (48) is two-dimensional. Display device according to one of claims 1 to 7, characterized by a touch panel for manually entering commands by touching the display surface (24) of the display (18). Display device according to one of claims 1 to 8, characterized by at least one optical lens arranged between the reflection film (42) and the IR photodiode array (48).Display device according to one of claims 1 to 9, characterized in that a diffuser layer (59) for scattering the backlight light is located in the space between the light exit side of the light guide (28) and the back of the display (18), which diffuser layer allows the IR light from the IR light sources (46) to pass through without scattering. Display device according to claim 10, characterized in that the diffuser layer (59) neutral for IR light is arranged between the light guide (28) and the mirror-reflective polarization film (50) or between the mirror-reflective polarization film (50) and the display (18).