OPTICAL SYSTEM FOR GENERATING A TWO- OR THREE-DIMENSIONAL IMAGE

Description

[0001] The invention relates to an optical system for generating a two- or three-dimensional image, comprising an imaging unit for the optical transmission and / or generation of image information and an optical waveguide which is designed to project the image information in at least one direction, further comprising a disc inclined with respect to the optical waveguide for reflecting the projected image information of the optical waveguide, so that the viewer perceives the image information as a virtual image in a display area on a side of the disc facing away from the user.

[0002] A head-up display shows the driver relevant information while driving. This information is projected onto the windshield in the driver's field of vision. To minimize obstruction to the driver's view, the displayed image is projected as a virtual image in front of the windshield, allowing the driver to simultaneously observe the surroundings and the displayed data without having to adjust their eyesight.

[0003] A disadvantage of this well-known head-up display, however, is that stray light falling onto the windshield from outside in the direction of the optical waveguide is directed by the reflected surface of the windshield in a direction in which it can reach the viewer's eye via the windshield, thus causing irritation to the viewer.

[0004] JP 2007 148092 A describes a head-up display in which the display contents of a display are reflected across a windshield and thus appear to be perceptible to an observer in an area behind the windshield in a so-called eyebox. The eyebox can be moved by pivoting a lens, whereby pivoting the lens also pivots incoming light out of the observer's field of vision. US 2019 / 212557 describes a head-up display with a waveguide in which the eyebox is realized by pivoting a mirror or pivoting an image generation unit. DE 10 2019 205138 A1 describes a head-up display with an image generation unit and a waveguide in which an eyebox (virtual display 2609) is movable.

[0005] WO 2019 038 201 A2 discloses a head-up display comprising a display element, a projection system, a diffusion screen and a mirror element, wherein the diffusion screen has focusing elements on its side facing the projection system and a light-blocking mask on its side facing away from the projection system.

[0006] CN 207752235 U discloses a head-up display with windshield projection, comprising an image generation module and an optical waveguide. The image generation module is arranged laterally along the waveguide. The waveguide has an input and output end. It receives light from the image generation module at the input end and transmits it to the output end. There, the light exits, is projected onto the windshield, reflected by the windshield, and directed into the eyebox area, creating a virtual image in the driver's line of sight. The head-up display further includes a drive motor that rotates the optical waveguide.

[0007] It is therefore an object of the invention to provide an optical system improved with regard to reflections.

[0008] This object is achieved by an optical system having the features of claim 1.

[0009] The subclaims list further advantageous measures which can be combined to achieve further advantages.

[0010] The object is achieved by an optical system for generating a two- or three-dimensional image, comprising an imaging unit for the optical transmission and / or generation of image information and an optical waveguide which is designed to project the image information in at least one direction and further comprising a disc inclined with respect to the optical waveguide for reflecting the projected image information of the optical waveguide, so that the viewer perceives the image information as a virtual image in a display area on a side of the disc facing away from the user, wherein a radiation detection unit is provided for detecting an angle of incidence range of radiation incident on the optical waveguide, and a control unit is provided which is connected to the radiation detection unit for data transmission,and which achieves tilting of the optical waveguide at a given angle of incidence.

[0011] An optical waveguide can, for example, be a holographic waveguide device. This can comprise, for example, an input coupling grating, an output coupling grating, and a plate. The optical waveguide is capable of projecting high-resolution, full-color images, generated using light sources with a wide bandwidth and wavelength, through an optically transparent or "transparent" medium onto the eye of a viewer.

[0012] Other flat specular reflectors can also be included with optical waveguides.

[0013] The disc can be a lens, for example a windshield.

[0014] Incident radiation is preferably light radiation such as solar radiation / sunlight radiation.

[0015] However, it has been recognized that such an optical waveguide exhibits a series of specific reflections when interacting with the sun. The critical interaction occurs in direct sunlight, where the sun's light is reflected via the optical waveguide and the windshield into the driver's eye. The brightness of this reflected beam can reach several tens of thousands of cd / m² and is therefore considered safety-critical.

[0016] According to the invention, it was recognized that common attenuation strategies, which involve reducing the reflected beam using a louver film, polarizers, and spectral filters, would disproportionately attenuate the useful light. Furthermore, the use of a film such as a louver film, for example, requires considerable manufacturing effort and is associated with high costs. Furthermore, it was recognized that the use of polarizers or spectral filters is also associated with high costs due to the required quality of the films.

[0017] The invention provides a simple solution for preventing reflected rays from entering the driver's eye and causing irritation. A radiation detection unit is used to measure solar radiation, which is at least data-linked to the control unit.

[0018] To prevent solar glare, the optical waveguide onto which the light is incident is tilted when a critical angle is reached at which a reflected beam hits the driver's eye. This tilt reliably moves reflected beams, such as those generated by sunlight, away from the driver's eye, so that they no longer hit the driver's eye.

[0019] Here it was recognized that tilting is possible because when using an optical waveguide there is an angular conformity of the coupled light, so that despite movement of the optical waveguide the coupling out does not change.

[0020] Preferably, the optical system is designed as a head-up display in a vehicle.

[0021] Preferably, the control unit is designed to change the angle of reflection of the incident radiation by tilting the lens. The angle of reflection can be used to change the direct reflection beam, which would otherwise cause irritation to the driver's eye.

[0022] Furthermore, the control unit is preferably configured to tilt the optical waveguide along a vertical axis. Direct sunlight thus travels along the vertical axis. This has the advantage that the driver does not move into the reflected beam due to typical lateral movements, which can often occur with drivers.

[0023] Furthermore, the control unit is preferably configured to tilt the optical waveguide by a tilt angle between a first position and a second position. These positions are preferably sufficiently far apart so that an unwanted reflection beam does not reach the driver's eye in the other position. By having only two positions, rapid tilting of less than 500 ms can be achieved. This is advantageous because when switching between the positions, the "reflection state" towards the sun is passed through, meaning that a direct reflection beam can be generated that falls into the driver's eye. This state should be as short as possible.

[0024] Preferably, the tilt angle is 10 degrees or less. It is particularly advantageous to have a tilt angle of around 5 degrees. This tilt angle can be easily achieved, for example, in a vehicle.

[0025] Preferably, an actuator system is provided, which is at least data-connected to the control unit and connected to the optical waveguide. Thus, the control unit can cause the optical waveguide to tilt by sending a signal to the actuator system. "Data-connected" can mean either wired or wireless.

[0026] Preferably, the imaging unit is designed such that it is tilted together with the optical waveguide. This allows for a particularly simple design of the optical system.

[0027] According to the invention, the radiation detection unit is arranged on the side of the optical waveguide opposite the radiation incidence side. In other words, this means that the radiation detection unit is arranged below the optical waveguide. This enables precise detection of the radiation and, in particular, the angle of incidence of the radiation, for example, solar radiation.

[0028] The beam detection unit comprises at least a first photodiode, phototransistor, pyrheliometer, or photomultiplier and a second photodiode, phototransistor, pyrheliometer, or photomultiplier for measuring a first angle of incidence range and a second angle of incidence range of a light beam incident on the optical waveguide. Furthermore, the first photodiode, phototransistor, pyrheliometer, or photomultiplier is preferably arranged in the beam detection unit at an angle substantially identical to the first angle of incidence range, and the second photodiode, phototransistor, pyrheliometer, or photomultiplier is preferably arranged at an angle substantially identical to the second angle of incidence range.In a further preferred embodiment, the first photodiode, phototransistor, pyrheliometer or photomultiplier is arranged in the radiation detection unit such that it has an orientation identical to the first angle of incidence range and the second photodiode, phototransistor, pyrheliometer or photomultiplier is arranged in the radiation detection unit such that it has an orientation identical to the second angle of incidence range.

[0029] This makes it easy to measure the critical angle of solar radiation.

[0030] Solar irradiance can be measured particularly easily using a photodiode. Photodiodes are operated in reverse bias and allow photocurrent and photovoltage to increase almost linearly with increasing illuminance.

[0031] Instead of photodiodes, phototransistors, pyrheliometers and photomultipliers can also be used.

[0032] In a further preferred embodiment, the radiation detection unit has a third photodiode arranged between the first photodiode, phototransistor, pyrheliometer, or photomultiplier and the second photodiode, phototransistor, pyrheliometer, or photomultiplier. Furthermore, the third photodiode is preferably arranged centrally between the first photodiode, phototransistor, pyrheliometer, or photomultiplier and the second photodiode, phototransistor, pyrheliometer, or photomultiplier.

[0033] This enables redundant measurement at the minimum of the voltages generated by the first photodiode, phototransistor, pyrheliometer or photomultiplier and the second photodiode, phototransistor, pyrheliometer or photomultiplier under direct sunlight. This means that the third photodiode has a maximum voltage at a certain solar ray incidence angle range, while the first photodiode, phototransistor, pyrheliometer or photomultiplier and the second photodiode, phototransistor, pyrheliometer or photomultiplier each have a minimum at this solar ray incidence angle range. This can serve as a safety-relevant safeguard when determining the solar radiation incidence angle range, since the position of the third photodiode represents a control variable for the first and second photodiode, phototransistor, pyrheliometer or photomultiplier.

[0034] Further features and advantages of the present invention will become apparent from the following description with reference to the accompanying figures, which schematically show: FIG 1 : a trained optical system according to the state of the art, FIG 2 : a first embodiment of an optical system according to the invention, FIG 3 : the optical system according to the invention in a tilted position, FIG 4 : a further embodiment of a radiation detection unit with voltage diagram, FIG 5 : the function of safety-relevant protection in detail.

[0035] FIG 1 shows an optical system 100 designed as a head-up display according to the prior art. This system has an imaging unit 8. Furthermore, the optical system 100 has an optical waveguide 7, in particular a holographic waveguide. The image generated in the imaging unit 8 (PGU) is reflected via the optical waveguide 7 and a windshield 3 into the area of ​​the driver's eye 5 as useful light 6.

[0036] The generated image or its beam is coupled into the, for example, multi-layer optical waveguide 7, deflected within the optical waveguide 7 and coupled out towards the windshield 3 in order to form the virtual image in a display area 9 reflected via the windshield 3.

[0037] Such an optical waveguide 7 consists of an optically transparent material that propagates light at the required wavelengths. The image emitted by the imaging unit 8 is coupled into the optical waveguide 7. This coupling can be achieved via a folding mirror 2. The optical waveguide 7 is capable of projecting high-resolution full-color images, generated using light sources with a wide bandwidth and wavelength, onto the driver's eye 5 through an optically transparent or "transparent" medium.

[0038] However, such an optical waveguide 7 exhibits a series of specific reflections when interacting with the sun 4. The critical interaction occurs during direct sunlight 10, where the sun's light is reflected via the optical waveguide 7 and the windshield 3 directly into the driver's eye 5.

[0039] The direct sunlight 10 falls on the optical waveguide 7 at a first angle of incidence α1 and exits as the first direct reflection beam 11 at a first angle of reflection β1.

[0040] The brightness of this first direct reflection beam 11 can easily be several 10,000 cd / m 2 and is therefore to be classified as safety-critical.

[0041] Common attenuation strategies using a louver foil, polarizers and spectral filters would achieve a reduction in the reflected radiation, but they would attenuate the reflected radiation disproportionately.

[0042] FIG 2 shows an optical system 1 in a first embodiment according to the invention.

[0043] This has an imaging unit 8 for generating an image for the driver in the display area 9. Furthermore, the optical system optionally has a folding mirror 2. The optical system 1 also has the optical waveguide 7, which is identical to the one in FIG 1 can be.

[0044] Furthermore, the optical system 1 has a windshield 3 for reflecting the image generated by the optical waveguide 7.

[0045] Furthermore, the optical system 1 has a beam detection unit 14 ( FIG 3 ) to capture the first angle of incidence range α1 ( FIG 1 ) from direct solar radiation 10 incident on the optical waveguide 7.

[0046] Furthermore, a control unit 12 is provided, which is connected to the radiation detection unit 14 ( FIG 3 ) is connected to the data stream. If the recorded first angle of incidence range α1 ( FIG 1 ) and thus the angle of reflection β1 is in a critical range, the control unit 12 causes the optical waveguide 7 to be tilted from, for example, the first position to the second position.

[0047] The tilting can be achieved by an actuator system (not shown). Furthermore, tilting about a vertical axis V is preferably provided, so that the direct solar radiation 10 is reflected at a second angle of reflection β2.

[0048] Since the optical waveguide 7 is tilted vertically, the direct solar radiation 10 is reflected at the second angle of reflection β2. With such a tilt, the direct solar radiation 10 migrates along the vertical axis V. This has the advantage that the driver does not move into the reflected second direct reflection beam 13 due to typical lateral movements, which can often occur with drivers.

[0049] Due to the tilting, the first direct reflection beam 11 is reliably moved out of the area of ​​the driver's eye 5 as a second direct reflection beam 13, so that it no longer hits the driver's eye 5.

[0050] Preferably, the control unit 12 is configured to tilt the optical waveguide 7 vertically by a predetermined angle from a first position to a second position, i.e., between two specific states. The magnitude of the tilt angle is preset and depends on the set image height and the tilt axis.

[0051] By tilting in only two specific states, i.e., between two positions, a rapid tilt can also be achieved. Furthermore, the actuator system must be designed to allow such a tilt. Such a tilt is sufficient because the first position and the second position are sufficiently far apart to convert the direct first reflection beam 11 into the second reflection beam 13, in which the second reflection beam 13 no longer reaches the driver's eye 5.

[0052] The optical system 1 according to the invention, with only two dedicated states, allows switching between positions in less than 500 ms. The reason for the speed of the switching lies primarily in the possibility, which cannot be ruled out, that the "reflex state" to the sun 4 is passed through during the switch. Therefore, the switch must be carried out quickly.

[0053] Additionally, the positions can be traversed in a 2-dimensional movement. The second dimension would correspond to a tilt around the horizontal axis (not shown). During this movement, the horizontal axis would be controlled to avoid the sun's reflection during the transition. The horizontal axis is orthogonal to the vertical axis V.

[0054] Preferably, such a tilt angle is up to 10 degrees, in particular approximately 5 degrees. Such a tilt can be achieved without any problems.

[0055] Several such tilt angles can, for example, be stored in a memory unit not shown as a function of the image height and can be read out by the control unit 12.

[0056] The optical system 1 according to the invention makes it possible to avoid reflections in critical reflection situations by means of geometric anti-reflection coating by tilting the optical waveguide 7. The possibility of using such a tilt of an optical waveguide 7 lies, among other things, in the angular conformity of the coupled-in light, so that the coupling-out remains unchanged despite movement of the optical waveguide 7. Furthermore, the folding mirror 2 and the imaging unit 8 can preferably be tilted with the optical waveguide 7.

[0057] If, during the migration of the sun 4 and thus of the solar radiation 10, the second reflection beam 13 becomes the critical reflection beam with a second angle of incidence range α2, a (re)tilting of the optical waveguide 7 from, for example, the second position to the first position is effected.

[0058] In other words: If the angle of reflection β2 is in a critical range, the control unit 12 causes the optical waveguide 7 to tilt, for example, from the second position to the first position.

[0059] In case of distortion of the resulting virtual image, for example due to defects in the windshield 3, compensation via software or another optical element is necessary.

[0060] FIG 3 shows the optical system 1 according to the invention in a tilted position. The optical system 1 has the beam detection unit 14 for detecting the first angle of incidence range α1 ( FIG 1 ) from direct solar radiation 10 incident on the optical waveguide 7.

[0061] The radiation detection unit 14 has at least two discrete diodes for detecting the position of the sun or the angle of incidence α1. The diodes are preferably designed as photodiodes 15a, 15c. The radiation detection unit 14 is arranged below the optical waveguide 7, with an arrangement below it on the side of the optical waveguide 7 opposite the radiation incidence side.

[0062] The photodiodes 15a, 15c are arranged in angle and orientation identical to the angle of incidence range α1 and the angle of incidence range α2, i.e. those angles which generate critical reflection rays.

[0063] Photodiodes 15a, 15c are operated in reverse bias, allowing the photocurrent to increase almost linearly with increasing illuminance. Without light, the photocurrent, which is a reverse current, exhibits similarly low values ​​as in other silicon diodes. As soon as light enters the junction, the light particles knock additional electrons out of the crystal lattice. As a result, the photocurrent increases with increasing illuminance. The relationship between photocurrent and illuminance is almost linear.

[0064] This means that without light, a photodiode behaves like a conventional diode. The light exposure releases additional electrons in the junction layer, and the photocurrent increases.

[0065] Instead of photodiodes, phototransistors or pyrheliometers, photomultipliers can also be used.

[0066] If the photocurrent, i.e. the photovoltage, increases, this causes a tilting of the optical waveguide 7. An increase means that the angle of incidence range α1 or α2 and thus a critical first reflection beam 12 or a critical second reflection beam 13 is present.

[0067] Furthermore, a control unit 12 is provided, which is connected to the beam detection unit 14 for data purposes. If the detected angle of incidence range α1 ( FIG 1 ) and thus the angle of reflection β1 in a critical range, the control unit 12 causes the optical waveguide 7 to be tilted from, for example, the first position to the second position.

[0068] If, during the migration of the sun 4 and thus of the solar radiation 10, the second reflection beam 13 with the critical second angle of incidence range α2 becomes the critical reflection beam, a (re)tilting of the optical waveguide 7 from, for example, the second position to the first position is effected.

[0069] An actuator system (not shown) can be provided. Furthermore, tilting about a vertical axis V is preferably provided, so that the direct solar radiation 10 is reflected at a second angle of reflection β2.

[0070] FIG 4 shows a second embodiment of a radiation detection unit 14a.

[0071] This radiation detection unit 14a points to the optical waveguide 7 ( FIG 3 ) the discrete photodiodes, phototransistors, pyrheliometers or photomultipliers as used in FIG 3 The photodiodes, phototransistors, pyrheliometers, or photomultipliers can also preferably be designed as photodiodes 15a, 15c. The beam detection unit 14a is arranged below the optical waveguide 7 ( FIG 3 ), wherein below, an arrangement on the side of the optical waveguide 7 opposite the radiation incidence side ( FIG 3 ) is.

[0072] The photodiodes 15a, 15c are arranged in angle and orientation identical to the angle of incidence range α1 and the angle of incidence range α2, i.e. those angles which generate critical reflection rays.

[0073] The photodiodes 15a, 15c are operated in reverse direction and allow a photocurrent and a photovoltage U1, U3 to increase almost linearly with increasing illuminance. Without incident light, the voltage U1 has a low value. This means that the voltages U1 and U3 depend on the position of the sun 4, which here moves along a path X during the course of the day. Thus, the voltages U1, U3 depend both on the position of the sun 4 along a path X and on the position of the optical waveguide 7 ( FIG 3 ) (tilted or not tilted, that is, first or second position of the optical waveguide 7 ( FIG 3 )). As soon as light falls directly on the photodiode 15a or 15c, the voltage U1, U3 increases.

[0074] The radiation detection unit 14a also has a third photodiode 15b. This is arranged centrally between the first photodiode 15a and the second photodiode 15c, thus enabling redundant measurement at the minimum voltage level. This means that the third photodiode 15b has a maximum in the voltage U2 at a solar ray incidence angle range, while the first photodiode 15a and the second photodiode 15c each have a minimum at this solar ray incidence angle range. This can be used as a safety-relevant safeguard when determining the solar radiation incidence angle range, as the third photodiode 15b, through its position, represents a control variable for the first photodiode 15a and the second photodiode 15c.

[0075] FIG 5shows such safety-relevant protection in detail. Except for extreme situations, the control variable U2 creates a transition region, which is represented as a third dimension in the voltage diagram. Using a "tunnel" around a characteristic curve, an action and control region can be defined around the data, while a deviation from these ratios of the three voltages U1, U2, and U3 represents a malfunction. Points A, B, C, and D describe such a possible characteristic curve.

Claims

1. Optical system (1) for creating a two- or three-dimensional image, comprising a picture generating unit (8) for optical transfer and / or generation of image information, and an optical waveguide (7) configured to project the image information in at least one direction, and a pane inclined relative to the optical waveguide (7) and serving for reflecting the projected image information of the optical waveguide (7), so that the observer perceives the image information as a virtual image in a display region (9) on a side of the pane facing away from the user, wherein a radiation capturing unit (14, 14a) is provided for capturing an incidence angle range (α1, α2) of radiation incident on the optical waveguide (7), and a control unit (12) is provided, which is connected to the radiation capturing unit (14, 14a) for data transfer, and which brings about tilting of the optical waveguide (7) in conjunction with a predefined incidence angle range, characterized in that the radiation capturing unit (14, 14a) is arranged on the opposite side of the optical waveguide (7) with respect to the radiation incidence side.

2. Optical system (1) according to Claim 1, characterized in that the control unit (12) is configured to change a reflection angle (β1, β2) of the incident radiation by the tilting.

3. Optical system (1) according to Claim 1 or 2, characterized in that the control unit (12) is configured to bring about a tilting along a vertical axis (V) of the optical waveguide (7).

4. Optical system (1) according to any of the preceding claims, characterized in that the control unit (12) is configured to tilt the optical waveguide (7) by a tilt angle between a first position and a second position.

5. Optical system (1) according to Claim 4, characterized in that the tilt angle is 10 degrees or less.

6. Optical system (1) according to any of the preceding claims, characterized in that an actuator system is provided, which is connected to the control unit (12) at least in terms of data technology and is connected to the optical waveguide (7).

7. Optical system (1) according to Claim 6, characterized in that the picture generating unit (8) is designed in such a way that it is tilted together with the optical waveguide (7).

8. Optical system (1) according to any of the preceding claims, characterized in that the radiation capturing unit (14, 14a) has at least a first photodiode, phototransistor, pyrheliometer, or photomultiplier and a second photodiode, phototransistor, pyrheliometer, or photomultiplier for measuring a first incidence angle range (α1) and a second incidence angle range (α2) of a light beam impinging on the optical waveguide (7).

9. Optical system (1) according to Claim 8, characterized in that the first photodiode, phototransistor, pyrheliometer, or photomultiplier is arranged at an angle substantially identical to the first incidence angle range (α1) and the second photodiode, phototransistor, pyrheliometer, or photomultiplier is arranged at an angle substantially identical to the second incidence angle range (α2) in the radiation capturing unit (14, 14a).

10. Optical system (1) according to Claim 8 or 9, characterized in that the first photodiode, phototransistor, pyrheliometer, or photomultiplier is arranged in the radiation capturing unit (14, 14a) in such a way that it has an orientation identical to the first incidence angle range (α1) and the second photodiode, phototransistor, pyrheliometer, or photomultiplier is arranged in the radiation capturing unit (14, 14a) in such a way that it has an orientation identical to the second incidence angle range (α2).

11. Optical system (1) according to any of the preceding Claims 8 to 10, characterized in that the radiation capturing unit (14, 14a) has a third photodiode arranged between the first photodiode, phototransistor, pyrheliometer, or photomultiplier and the second photodiode, phototransistor, pyrheliometer, or photomultiplier.

12. Optical system (1) according to Claim 11, characterized in that the third photodiode is arranged centrally between the first photodiode, phototransistor, or pyrheliometer, or photomultiplier and the second photodiode, phototransistor, pyrheliometer, or photomultiplier.

13. Optical system (1) according to any of the preceding claims, characterized in that the optical system (1) is designed as a head-up display.