3D head-up display for a means of transport

Abstract

The present invention relates to a 3D head-up display (10) for a means of transport and to a method for operating such a 3D head-up display (10). The 3D head-up display (10) has an imaging unit (1) for generating an image, an optical unit (2) for projecting the image onto a mirror unit (3), and a switchable optical component (25) for influencing a polarization of the light emitted by the imaging unit (1). The switchable optical component (25) is configured not to influence a linear polarization of the light emitted by the imaging unit (1) in a first state and to rotate the linear polarization of the light emitted by the imaging unit (1) by 90° in a second state. A quarter-wave plate (251) is used to convert the linear polarization of the light emitted by the switchable optical component (25) into a circular polarization.The invention also relates to a means of transport with such a 3D head-up display.

Description

[0001] The present invention relates to a 3D head-up display for a means of transportation and to a method for operating such a 3D head-up display. The invention also relates to a means of transportation with such a 3D head-up display.

[0002] A head-up display, also known as a HUD, is a display system that allows the viewer to maintain their line of sight by projecting the content into their field of vision. While such systems were originally used primarily in aviation due to their complexity and cost, they are now also being installed in large-scale production in the automotive sector.

[0003] Head-up displays generally consist of an imaging unit or PGU (Picture Generating Unit), an optical unit, and a mirror unit. The imaging unit generates the image using at least one display element. Today's head-up displays use either LC-based displays (LC: Liquid Crystal) or laser scanning systems to generate the image. The optical unit directs the image onto the mirror unit. The mirror unit is a partially reflective, translucent pane. The viewer therefore sees the content displayed by the imaging unit as a virtual image and, at the same time, the real world behind the pane. In the automotive sector, the windshield is often used as the mirror unit, and its curved shape must be taken into account in the display. The interaction of the optical unit and the mirror unit creates a virtual image that is an enlarged representation of the image generated by the imaging unit.

[0004] Head-up displays typically display the same image for both eyes. True 3D head-up display applications have not been successful due to their complexity and associated costs.

[0005] Against this background, US 2012 / 0057133 A1 describes a display system in which two polarized image sources simultaneously generate a pair of differently polarized images. The polarized images from each image source are optically aligned along a common optical path and displayed on a display screen. Depending on the mode of the display system, the viewer can wear 3D polarized glasses to view the displayed images.

[0006] US 2019 / 0041636 A1 describes a head-up display with two image generators, each producing a linearly polarized image. The polarization directions of the two images are perpendicular to each other. A polarization beam splitter combines the two images, which are then reflected into the viewer's eye via an optical system.

[0007] US 11,662,591 B1 describes an optical subsystem for use in a display system or an imaging system. The optical subsystem comprises a plurality of reflective surfaces arranged together to enable variable control of the device's internal path lengths of light reaching an imaging sensor or traveling a path to a viewer's eye. The optical subsystem can be used to provide multiple images simultaneously with different apparent depths perceived by the user.

[0008] It is an object of the present invention to provide simpler solutions for a 3D head-up display for a means of transport.

[0009] This object is achieved by the features of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0010] According to a first aspect of the invention, a 3D head-up display for a means of transport comprises: - an imaging unit for generating an image; - an optical unit for projecting the image onto a mirror unit; - a switchable optical component for influencing a polarization of the light emitted by the imaging unit, wherein the switchable optical component is configured not to influence a linear polarization of the light emitted by the imaging unit in a first state and to rotate the linear polarization of the light emitted by the imaging unit by 90° in a second state; and - a quarter-wave plate for converting the linear polarization of the light emitted by the switchable optical component into circular polarization.

[0011] According to a further aspect of the invention, a method for operating a 3D head-up display according to the invention comprises the steps: - Sequentially generating a first image for a right eye of a viewer and a second image for a left eye of the viewer by an imaging unit of the 3D head-up display; and - Controlling a switchable optical component of the 3D head-up display synchronously with the image generation by the imaging unit.

[0012] In the inventive solution, a single imaging unit alternately generates images for the viewer's right and left eye. Both images can be generated using the full pixel count of a display of the imaging unit. The light strikes a switchable optical component that either allows the light to pass unaffected or rotates the polarization by 90°. A quarter-wave plate, which can be arranged at an angle of 45°, for example, then converts the polarization into left-handed or right-handed circular polarization. Since the inventive solution requires only a single imaging unit, the 3D head-up display can be designed very compactly. The use of circularly polarized light has the advantage that an exact horizontal alignment of the viewer's eyes is not required.A further advantage of the inventive solution is that it is very easy to switch from a 3D display mode to a 2D display mode. In 2D display mode, the switchable optical component is not switched, and the imaging unit always displays the same images, instead of alternating images for the left and right eyes. The two display modes are preferably programmed into a control unit of the 3D head-up display and can be selected by the user as desired.

[0013] According to one aspect of the invention, the imaging unit comprises an LCD-based display for generating the images. The use of the inventive solution is particularly advantageous for such imaging units, since LCD-based displays typically emit linearly polarized light.

[0014] According to one aspect of the invention, the switchable optical component comprises a liquid crystal cell. Liquid crystal cells are particularly well suited for this application because they can influence polarization in a very targeted and controlled manner. Furthermore, they are available at low cost.

[0015] According to one aspect of the invention, the 3D head-up display comprises a control unit configured to switch the switchable optical component synchronously with image generation by the imaging unit for a right eye and a left eye of a viewer. Such a control unit ensures that the images generated in front of the imaging unit for the right eye and the left eye always exhibit the correct polarization after passing through the switchable optical component. In this way, crosstalk between the images on the viewer's side is reliably avoided.

[0016] According to one aspect of the invention, the 3D head-up display has a mirror unit provided with a film for reflecting p-polarized light. When reflected from the windshield, different reflection coefficients apply to s-polarized light and p-polarized light. S-polarized light is reflected far better than p-polarized light at the reflection angles that occur in typical installation situations. To compensate for this, the mirror unit can be provided with a special film that has increased reflectivity for p-polarized light. In this way, it can be achieved that both polarization components have approximately the same intensity after reflection from the mirror unit.

[0017] According to one aspect of the invention, the 3D head-up display comprises a filter for reducing a portion of s-polarized light. As an alternative to using a film, one can ensure that the s-polarized portion of the light has a lower intensity before reflection from the mirror unit, so that both polarization components have approximately the same intensity after reflection from the mirror unit. This approach can also be used in combination with a film for reflecting p-polarized light to compensate for any remaining differences in the intensity of the two polarization components.

[0018] According to one aspect of the invention, the 3D head-up display comprises polarizing glasses for filtering image light for a viewer's right eye and image light for a viewer's left eye. The polarizing glasses preferably comprise a quarter-wave plate and absorbing polarizing filters. Polarizing glasses are required to separate the images for the right eye and the left eye. The quarter-wave plate transforms the circular polarization of the incoming image light back into a linear polarization, which is perpendicular to each other for the images for the right eye and the left eye. Absorbing polarizing filters therefore make it easy to filter out the unwanted image light.

[0019] Preferably, a 3D head-up display according to the invention is used in a means of transportation. The means of transportation can be, for example, a motor vehicle, but alternatively also an aircraft, a rail vehicle, or a watercraft. Use in stationary machines, e.g., a crane, is also possible.

[0020] Further features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the figures. Figure overview Fig. 1 shows schematically a head-up display for a means of transport; Fig. 2 schematically shows a first embodiment of a 3D head-up display for a means of transport; Fig. 3 schematically shows a second embodiment of a 3D head-up display for a means of transport; Fig. 4 schematically shows a third embodiment of a 3D head-up display for a means of transport; Fig. 5 schematically shows a method for operating a 3D head-up display for a means of transport; Fig. 6 illustrates the control of an imaging unit and a switchable optical component; and Fig. Figure 7 shows schematically a means of transport in which a solution according to the invention is implemented. Character description

[0021] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. Like reference numerals are used in the figures for like or equivalent elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the illustrated embodiments and that the described features can also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0022] Fig. Figure 1 shows a schematic diagram of a head-up display 10 according to the prior art for a means of transportation. In this example, the means of transportation is a motor vehicle. The head-up display 10 comprises an imaging unit 1, an optical unit 2, and a mirror unit 3. A beam SB1 emanates from a display element 11, which is reflected by a folding mirror 21 onto a curved mirror 22, which reflects it toward the mirror unit 3. The mirror unit 3 is depicted here as the windshield 31 of a motor vehicle. From there, the beam SB2 travels toward the eye of a viewer 61.

[0023] The viewer 61 sees a virtual image VB, which is located outside the motor vehicle above the hood or even in front of the motor vehicle. Due to the interaction of the optical unit 2 and the mirror unit 3, the virtual image VB is an enlarged representation of the image displayed by the display element 11. A speed limit, the current vehicle speed, and navigation instructions are symbolically shown here. As long as the eye is within the eyebox 62 indicated by a rectangle, all elements of the virtual image VB are visible to the eye. If the eye is outside the eyebox 62, the virtual image VB is only partially visible or not visible at all to the viewer 61. The larger the eyebox 62, the less restricted the viewer 61 is in choosing his or her seating position.The curvature of the curved mirror 22 is adapted to the curvature of the windshield 31 and ensures that the image distortion is stable across the entire eyebox 62. The curved mirror 22 is rotatably mounted by means of a bearing 221. The resulting rotation of the curved mirror 22 enables the eyebox 62 to be moved and thus the position of the eyebox 62 to be adjusted to the position of the eye. The folding mirror 21 ensures that the path traveled by the beam SB1 between the display element 11 and the curved mirror 22 is long, while at the same time the optical unit 2 remains compact. The optical unit 2 is separated from the surroundings by a transparent cover 23. The optical elements of the optical unit 2 are thus protected, for example, against dust present in the interior of the vehicle.A glare shield 24 serves to reliably absorb the light reflected across the boundary surface of the cover 23, preventing glare for the viewer 61. In addition to sunlight SL, light from another interfering light source 64 can also reach the display element 11.

[0024] Fig. Figure 2 schematically shows a first embodiment of a 3D head-up display 10 for a means of transportation. The 3D head-up display 10 has an imaging unit 1 for generating an image, an optical unit 2 for projecting the image onto a mirror unit 3, and a switchable optical component 25 for influencing a polarization of the light emitted by the imaging unit 1. A windshield 31 again serves as the mirror unit 3 here. The switchable optical component 25 is configured not to influence a linear polarization of the light emitted by the imaging unit 1 in a first state and to rotate the linear polarization of the light emitted by the imaging unit 1 by 90° in a second state. For example, the switchable optical component 25 can comprise a liquid crystal cell 250.A quarter-wave plate 251 serves to convert the linear polarization of the light emanating from the switchable optical component 25 into a circular polarization. In the example shown, the imaging unit 1 has an LC-based display 110 for generating the images. A control unit 252 is configured to switch the switchable optical component 25 synchronously with image generation by the imaging unit 1 for a right eye and a left eye of a viewer 61. Polarizing glasses 63 are used to separate the images for the right eye and the left eye. A quarter-wave plate 630 of the polarizing glasses 63 transforms the circular polarization of the incoming image light back into a linear polarization, which is perpendicular to each other for the images for the right eye and the left eye. The unwanted image light can then be easily filtered out using absorbing polarizing filters 631, 632.

[0025] Fig. Figure 3 schematically shows a second embodiment of a 3D head-up display 10 for a means of transport. The embodiment largely corresponds to that shown in Fig. 2. However, the mirror unit 3, here again in the form of the windshield 31, is provided with a film 32 for reflecting p-polarized light. When reflected from the windshield 31, different reflection coefficients apply to s-polarized light and p-polarized light. S-polarized light is reflected far better than p-polarized light at the reflection angles that occur in typical installation situations. To compensate for this, the mirror unit 3 in this embodiment is provided with a special film 32 that has increased reflectivity for p-polarized light. In this way, it can be achieved that both polarization components have approximately the same intensity after reflection from the mirror unit 3.

[0026] Fig. Figure 4 schematically shows a third embodiment of a 3D head-up display 10 for a means of transport. The embodiment largely corresponds to that shown in Fig. 2. However, the 3D head-up display 10 has a filter 33 for reducing a portion of s-polarized light. The filter 33 ensures that the s-polarized portion of the light has a lower intensity before reflection at the mirror unit 3, so that after reflection at the mirror unit 3, both polarization portions have approximately the same intensity. This approach can also be used in combination with the Fig. 3 provided film for the reflection of p-polarized light can be used to compensate for remaining differences in the intensity of the two polarization components.

[0027] Fig. 5 schematically shows a method for operating a 3D head-up display for a means of transportation. In the method, an imaging unit of the 3D head-up display sequentially generates S1 a first image for a viewer's right eye and a second image for a viewer's left eye. A switchable optical component of the 3D head-up display, e.g., a liquid crystal cell, is controlled S2 synchronously with the image generation by the imaging unit. Depending on its state, the switchable optical component either allows the light emitted by the imaging unit to pass through unaffected or rotates its polarization by 90°.

[0028] Fig. Figure 6 illustrates the control of an imaging unit and a switchable optical component. First, the image for the left eye is generated on the display with the full number of pixels (1), and then the image for the right eye (2) is generated with the full number of pixels. Simultaneously with the respective images, the polarization of the switchable optical component is switched, so that image 1 with polarization for the left eye and image 2 with polarization for the right eye always coincide. The first image for the left eye is then generated, for example, at time t1, at which image B11 is shown on the display in full resolution and the switchable optical component is switched to polarization L for the left eye. At time t2, the first image B21 for the right eye is then generated. Accordingly, the switchable optical component is switched to polarization R for the right eye. The switching and pause times do not have to be the same.In particular, it is useful to have short breaks during slightly longer display times.

[0029] Fig.7 schematically shows a means of transport 100 with a 3D head-up display 10 according to the invention. In this example, the means of transport 100 is a motor vehicle. Data on the vehicle's surroundings can be acquired using a sensor system 101. The sensor system 101 can in particular comprise sensors for environmental detection, e.g., ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information acquired by the sensor system 101 can be used to generate content to be displayed for the 3D head-up display 10. Further components of the motor vehicle in this example are a navigation system 102, by means of which position information can be provided, and a data transmission unit 103. By means of the data transmission unit 103, for example, a connection to a backend can be established, for example in order to obtain updated software for components of the motor vehicle.A memory 104 is provided for storing data. Data exchange between the various components of the motor vehicle takes place via a network 105. List of reference symbols 1 imaging unit 10 Head-Up Display 11 Display element 110 LCD display 2 optical unit 21 folding mirrors 22 Curved Mirror 221 Storage 23 Transparent cover 24 Anti-glare protection 25 Switchable optical component 250 liquid crystal cell 251 quarter-wave plate 252 Control unit 3 Mirror unit 31 Windshield 32 slides 33 filters 61 viewers 62 Eyebox 63 Polarized glasses 630 quarter-wave plate 631 polarizing filter 632 polarizing filters 64 stray light source 100 means of transport 101 Sensor Technology 102 Navigation system 103 Data transmission unit 104 memory 105 Network S1 Sequential generation of images for a right and a left eye of a viewer S2 Control of a switchable optical component synchronously with image generation SB1 beam SB2 beam SL Sunlight VB Virtual Image QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2012 / 0057133 A1

[0005] US 2019 / 0041636 A1

[0006] US 11,662,591 B1

[0007]

Claims

[1] 3D head-up display (10) for a means of transport, comprising: - an imaging unit (1) for generating an image; - an optical unit (2) for projecting the image onto a mirror unit (3); - a switchable optical component (25) for influencing a polarization of the light emitted by the imaging unit (1), wherein the switchable optical component (25) is configured not to influence a linear polarization of the light emitted by the imaging unit (1) in a first state and to rotate the linear polarization of the light emitted by the imaging unit (1) by 90° in a second state; and - a quarter-wave plate (251) for converting the linear polarization of the light emitted by the switchable optical component (25) into a circular polarization. [2] 3D head-up display (10) according to claim 1, wherein the imaging unit (1) comprises an LC-based display (110) for generating the images. [3] 3D head-up display (10) according to claim 1 or 2, wherein the switchable optical component (25) comprises a liquid crystal cell (250). [4] 3D head-up display (10) according to one of the preceding claims, comprising a control unit (252) which is configured to switch the switchable optical component (25) synchronously with an image generation by the imaging unit (1) for a right eye and a left eye of a viewer. [5] 3D head-up display (10) according to one of the preceding claims, with a mirror unit (3, 31) provided with a film (32) for the reflection of p-polarized light. [6] 3D head-up display (10) according to one of the preceding claims, comprising a filter (33) for reducing a proportion of s-polarized light. [7] 3D head-up display (10) according to one of the preceding claims, comprising polarizing glasses (63) for filtering image light for a right eye of a viewer and image light for a left eye of the viewer. [8] 3D head-up display (10) according to claim 7, wherein the polarizing glasses (63) comprise a quarter-wave plate (630) and absorbing polarizing filters (631, 632). [9] Method for operating a 3D head-up display (10) according to one of the preceding claims, comprising the steps: - Sequential generation (S1) of a first image for a right eye of a viewer and a second image for a left eye of the viewer by an imaging unit (1) of the 3D head-up display (10); and - Controlling (S2) a switchable optical component (25) of the 3D head-up display (10) synchronously with the image generation by the imaging unit (1). [10] Means of transport (100) with a 3D head-up display (10) according to one of claims 1 to 8.

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