Optical arrangement having a holographic display, head-up display, and transparent display

Abstract

The invention relates to an optical arrangement (7) which comprises at least one projector (11) and at least one display (8, 12, 19), wherein the at least one projector (11) and the at least one display (8, 12, 19) are arranged relative to one another in such a way that light emitted by the projector (11) onto the display (8, 12, 19) is diffracted by the display (8, 12, 19) in the direction of at least one eyebox (14). The display (8, 12, 19) comprises at least one holographic optical element (HOE) (9), the diffraction grating structure of which comprises a plurality of segments and which is designed such that, for each segment, at least one scattering lobe (5, 16-18, 21, 22) of the diffracted light is location-dependently defined so as to generate at least one eyebox (14) having a predefined boundary.

Description

[0001] 1 PATERIS

[0002] Applicant: Carl Zeiss Jena GmbH

[0003] Our reference number: Z50431-WO bzi / ehä

[0004] Optical arrangement with holographic display, head-up display and transparent display

[0005] The present invention relates to an optical arrangement, a head-up display and a transparent display.

[0006] Displays or display devices of various types are used in numerous applications. Examples include head-up displays (HUDs) or head-mounted displays (HMDs), or screens in general, such as those on monitors or mobile devices, or in the form of transparent displays. In many cases, it is desirable that the content displayed by the respective screen is visible to users within a defined spatial angle. This is particularly important when a certain level of confidentiality of displayed content, such as private or business information, needs to be ensured, or when the surrounding environment should not be disturbed by the use of the display.

[0007] It has become apparent that combining transparent displays with a so-called privacy function is difficult to implement. Conventional privacy films are designed to narrow the scattering lobe of the emitted light, with the reduction being uniform across every point. This means that outside the intended viewing angle, the entire image is not completely invisible, but remains visible in certain areas. Furthermore, a sharply defined eyebox cannot be achieved using conventional privacy films. Z50431-WO 2 PATERIS

[0008] The term scattering lobe refers here to the solid angle distribution under which the light incident on a scattering element, scattering center, pixel, or segment is scattered.

[0009] A head-up display typically comprises a picture generating unit (PGU) or projector, also called an image generator, a projection surface, an eyebox, and a virtual image plane. The image generator or projector creates an image. This image is projected onto the projection surface or display and then projected from the surface into the eyebox. The eyebox is the area of ​​space in which the projected image is perceived by a user or viewer as a virtual image. The virtual image plane, the plane on which the virtual image is generated, is located on or behind the projection surface. When a user looks through the projection surface of a head-up display, they see a superimposed or reflected "virtual image" overlaid on their view of the real world ("real image").This superposition is achieved by a beam combiner, which is transparent to ambient light but also directs a beam of light generated by an external image sensor into an eyebox where the user's eye can be positioned. The eye perceives this beam as a virtual image. The combiner can, for example, be formed by a windshield, which in this case serves as the projection surface.

[0010] A transparent display can, for example, comprise a projector and a transparent projection surface or display surface onto which light is shone by the projector and reflected or transmitted to create a real image (preferably in-plane). The transparent projection surface can have appropriately designed scattering centers, e.g., in the form of a diffraction grating.

[0011] Furthermore, in certain situations or applications, two projectors or two displays are desired, whose displayed content should be visible simultaneously in a common eyebox, but not outside of this Z50431-WO 3 PATERIS

[0012] Eyebox. This cannot be achieved, or only unsatisfactorily, with the solutions known from the current state of the art.

[0013] Document WO 2021 / 175608 A1 discloses an arrangement for reflection suppression in a windshield display system for a motor vehicle. Document DE 102023 123 102 A1 describes a multi-user head-up display, particularly for a vehicle. Document Weng, Yishi, et al., “Polarization volume grating with high efficiency and large diffraction angle,” Optics Express Vol. 24, No. 16 (08.08.2016), 17746-17759, describes a polarization-sensitive volume diffraction grating with high efficiency and a large diffraction angle.

[0014] Against the background described above, the object of the present invention is to provide an advantageous optical arrangement. A further object is to provide an advantageous head-up display and an advantageous transparent display. These objects are achieved by an optical arrangement according to claim 1, a head-up display according to claim 10, and a transparent display according to claim 12. The dependent claims contain further advantageous embodiments of the invention.

[0015] The optical arrangement according to the invention comprises at least one projector, e.g., an image transmitter or beamer, and at least one display. The display can be configured as a diffuser and / or projection surface. The display can be, for example, a windshield of a vehicle or a portion thereof. The at least one projector and the at least one display are arranged, particularly spatially, relative to each other such that light emitted by the projector onto the display is diffracted by the display towards at least one eyebox, e.g., a predetermined, fixed, or defined eyebox. Z50431-WO 4 PATERIS

[0016] The display comprises at least one holographic optical element (HOE) whose diffraction grating structure comprises or has a plurality, preferably a multiplicity, of segments and is configured such that for each segment, e.g., each point or pixel of the HOE, at least one diffraction lobe of the diffracted light is defined spatially such that at least one eyebox with a defined or predetermined boundary or edge, in particular with a defined or predetermined spatial boundary, preferably in the form of a sharp edge, is generated. In other words, the holographic optical element is segmented planarly or spatially with respect to its diffraction grating structure such that one or more diffraction lobes are defined individually for each segment.Each segment, pixel, or point diffracts the light emitted by the projector into a unique scattering pattern, thus generating or forming a defined, preferably sharply defined, eyebox via the display. The diffraction efficiency of each point or pixel of the HOE depends on the angle of incidence of the light. This angle-of-incidence dependence can vary depending on location. The HOE can also be described as a graphic diffuser.

[0017] The holographic optical element can comprise at least one volume hologram and / or at least one two-dimensional hologram, i.e., a planar hologram, e.g., in the form of a surface hologram or a film.

[0018] To fabricate the holographic optical element, a simulation can first be performed using standard software, such as ray tracing software like Ansys Zemax or Lighttools. Subsequently, a suitable light-sensitive material or substrate, such as a photopolymer, can be exposed using a freeform exposure setup. The entire surface or volume of the substrate can be exposed simultaneously or section by section, for example, using a freeform wavefront. EsZ50431-WO 5 PATERIS

[0019] Multiple exposure sets can also be used, e.g., a first exposure set to generate a grid structure for a first eyebox and a second exposure set to generate a grid structure for a second eyebox. Alternatively, instead of area exposure, the holographic optical element can be printed using an HOE printer. In this case, the grid structure can be generated or printed segment by segment, particularly point by point or pixel by pixel, depending on the location.

[0020] The optical arrangement according to the invention has the advantage of providing a high-performance privacy function, which efficiently reduces both potential intensity losses and unwanted stray light. Furthermore, the optical arrangement according to the invention is relatively easy and cost-effective to manufacture, requires little installation space, is robust, and can be used to advantage in many areas. Application areas include, for example, head-up displays, head-mounted displays, screens, display boards, mobile devices, as well as in the fields of consumer optics and smart home technology.

[0021] Preferably, the defined boundary or edge of the eyebox is designed as an edge, or in other words, a step, at which the intensity of the light projected by the projector towards the eyebox drops to a value below a predetermined threshold. Advantageously, the intensity of the light projected towards the eyebox decreases in steps or abruptly at the boundary, edge, or step. The edge can also be designed as a gradual intensity reduction (fade-out) extending over a predetermined or specific length, such as 10 percent of the eyebox size, for example, with a change in intensity from 90 percent to 10 percent. These variations ensure that high-intensity light is projected only into the area of ​​the eyebox.For example, the intensity at the boundary or edge can be reduced from 90 percent to 10 percent or by more than 90 percent, preferably by more than 99 percent, i.e., for example, to a value of less than 10 percent, preferably less than 1Z50431-WO 6 PATERIS.

[0022] The percentage of the average intensity of the light projected into the eyebox, or the percentage of the light intensity, can drop to zero. This design has the advantage of creating a precisely defined and delimited eyebox that offers high-quality privacy.

[0023] The display and / or the holographic optical element can be designed to be transmissive and / or reflective, for example depending on the wavelength or frequency and / or the angle of incidence and / or the polarization of the light. This opens up diverse application possibilities for the optical arrangement.

[0024] In an advantageous embodiment, for a plurality of segments, e.g., for each individual segment, of the at least one holographic optical element, at least one first scattering lobe and at least one second scattering lobe can be defined, wherein the first and second scattering lobes differ from each other with respect to their geometry, i.e., for example, with respect to their emission direction and / or their divergence angle or opening angle, and / or with respect to at least one feature of the diffracted light, i.e., with respect to its wavelength and / or angle of incidence and / or polarization. The first and second scattering lobes can be spatially partially overlapping or spatially disjoint, i.e., not spatially overlapping. In this way, two or more eyeboxes can be generated, which is advantageous for applications related to HUDs for vehicles.In particular, for a plurality of segments, e.g., for each segment, of the at least one holographic optical element, at least one first scattering lobe and at least one second scattering lobe can be defined, wherein the first scattering lobe creates a first eyebox and the second scattering lobe creates a second eyebox. The at least one first scattering lobe and the at least one second scattering lobe can differ from each other with respect to the wavelength or frequency and / or the beam angle and / or the polarization of the diffracted light. This makes it possible to focus different content into the at least two eyeboxes.

[0025] Projecting content into eyeboxes is possible. However, it is also possible to project the same content into at least two eyeboxes simultaneously.

[0026] The at least one holographic optical element can be designed as a multiplex HOE or as a stack of several holographic optical elements. This can improve the image quality and thus the user experience.

[0027] In another variant, the optical arrangement can comprise at least one first projector and at least one second projector, and the at least one holographic optical element (HOE) of the display can be configured to diffract light emitted by the first and second projectors in such a way as to form or create a common eyebox. In other words, the at least one holographic optical element of the display can be configured to emit or project light from the projector into a common eyebox, e.g., a single eyebox.

[0028] The optical arrangement can be configured as a head-up display, a head-mounted display, a display panel, or a screen. In particular, it can be configured as a component of a mobile device or a device in the field of consumer optics or smart home technology.

[0029] The head-up display according to the invention comprises a previously described optical arrangement. The head-up display according to the invention has the same features and advantages as the optical arrangement already described. The head-up display can be configured as a head-up display for a vehicle, e.g., a motor vehicle, an aircraft, a rail vehicle, or a ship.

[0030] The transparent display according to the invention comprises a previously described optical arrangement. The transparent display according to the invention Z50431-WO 8 PATERIS

[0031] The display has the same features and advantages as the optical arrangement already described.

[0032] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying figures. Although the invention is illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention.

[0033] The figures are not necessarily detailed or to scale and may be enlarged or reduced to provide a better overview. Therefore, the functional details disclosed here are not to be understood as limiting, but merely as an illustrative basis to guide a person skilled in this field of technology in using the present invention in a variety of ways.

[0034] The expression "and / or" used here, when used in a series of two or more elements, means that each of the listed elements can be used alone, or any combination of two or more of the listed elements can be used. For example, when describing a composition containing the components A, B, and / or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.

[0035] Fig. 1 schematically shows the beam path of a display without and with privacy film according to the prior art.

[0036] Fig. 2 schematically shows a head-up display or transparent display of a motor vehicle according to the prior art. Z50431-WO 9 PATERIS

[0037] Fig. 3 schematically shows a first variant of a transparent display of a motor vehicle according to the invention with an optical arrangement according to the invention.

[0038] Fig. 4 schematically shows a second variant of a transparent display of a motor vehicle according to the invention with an optical arrangement according to the invention.

[0039] Fig. 5 schematically shows a third variant of a transparent display of a motor vehicle according to the invention with an optical arrangement according to the invention.

[0040] Fig. 6 schematically shows a variant of a head-up display according to the invention for a motor vehicle with an optical arrangement according to the invention.

[0041] Fig. 7 schematically shows another variant of a head-up display according to the invention for a motor vehicle with an optical arrangement according to the invention.

[0042] Fig. 8 schematically shows an optical arrangement according to the invention in the form of a block diagram.

[0043] The prior art is first described below with reference to Figures 1 and 2. Figure 1 schematically shows the light path of a display 1 without privacy film 6 (Fig. 1 top) and with privacy film 6 (Fig. 1 bottom) according to the prior art. In a typical display 1, individual pixels, of which a first pixel 2 and a second pixel 3 are shown as examples, emit light in different directions. The light path is indicated by arrows with the reference numeral 5. In a typical display 1, each pixel 2 and 3 is visible to a user, whose eye is schematically represented by the reference numeral 4, from different viewing angles of the display 1 (e.g., according to Lambert's law). A user can

[0044] This means that even when viewing Display 1 at an angle, the user can still fully perceive the displayed content. This is a real (in-plane) image of a transparent display, unlike the virtual image of the HUD. In contrast, a privacy film placed on Display 1, as shown in Figure 1 below, reduces the beam angle or scattering of individual pixels 2 and 3. As a result, a user viewing Display 1 at an angle greater than a certain threshold angle can only visually perceive individual pixels. In the example shown, pixel 2 is invisible to the user, and only pixel 3 is visible.

[0045] Figure 2 schematically shows a head-up display or transparent display 10 of a motor vehicle according to the prior art. Light emitted by a projector or image transmitter or beamer 11 is reflected or diffracted towards an eyebox 14 by means of a holographic optical element (HOE) 13 attached to or integrated into a windshield 12. The beam path 5 indicates the light emitted by a single pixel of the HOE 13 towards the eyebox 14. The projected image is visually perceptible to a user from the eyebox 14 as a virtual image. In addition, ambient light 15 passes through the windshield 12 and the HOE 13 into the eyebox 14, so that a user can visually perceive the real surroundings in addition to the virtual image.

[0046] Figure 3 schematically shows a first variant of a transparent display 10 of a motor vehicle according to the invention, comprising an optical arrangement 7 according to the invention. The optical arrangement 7 according to the invention comprises a projector 11 and a display, which in this case is formed by the windshield 12, and which includes a HOE 9. The HOE 9 has a diffraction grating structure, which is preferably segmented in at least two dimensions, i.e., comprises a plurality, preferably a multiplicity, of segments. The diffraction grating structure is designed such that for each segment, e.g., each point or each pixel, of the HOE 9, at least one scattering lobe of the diffracted light is spatially dependent.

[0047] is defined such that an eyebox 14 is generated with a defined or predetermined boundary or a defined or predetermined edge, preferably a sharp edge which limits the beam angle.

[0048] In Figure 3, the light path emitted by a first pixel of HOE 9 is labeled with reference numeral 16, the light path emitted by a second pixel of HOE 9 with reference numeral 17, and the light path emitted by a third pixel of HOE 9 with reference numeral 18. Thus, for each segment or point / pixel of HOE 9, a unique diffraction pattern of the diffracted light is defined and localized. Each pixel diffractes light precisely and exclusively into the eyebox 14. From a viewing angle outside the eyebox 14, the projected image is not visually perceptible, and in particular, not pixel by pixel. In this way, a clearly defined and precise privacy function can be implemented, and disruptive stray light can be effectively reduced.

[0049] Figure 4 schematically shows a second variant of a transparent display 10 according to the invention for a motor vehicle with an optical arrangement 7 according to the invention. In this variant, light emitted by the projector 11 from a segment, point, or pixel of the HOE 9 is diffracted into two scattering lobes 21 and 22, or in other words, into non-overlapping solid angle regions 21 and 22. A first eyebox 14a is formed by means of the first scattering lobe 21, and a second eyebox 14b is formed by means of the second scattering lobe 22. Both eyeboxes 21 and 22 each have a sharp boundary or edge. This design is advantageous, for example, in connection with head-up displays 10 for vehicles.For example, a first eyebox 14a can be intended for content to be displayed to a driver, and a second eyebox 14b can be intended for a passenger or other occupants to display different content. More than two eyeboxes can also be implemented in this way. The same content can be displayed in the eyeboxes, or Z50431-WO 12 PATERIS.

[0050] Different content can be projected. The beam paths for the various eyeboxes 14a and 14b can be separated or divided by diffracting the light into one of the scattering cones depending on its wavelength or frequency and / or its polarization.

[0051] Figure 5 schematically shows a third variant of a transparent display 10 according to the invention for a motor vehicle with an optical arrangement 7 according to the invention. In this variant, a first HOE 9a and a second HOE 9b are arranged on the windshield 12. The two HOE 9a and 9b can also be two areas of a display. Furthermore, in this variant, a first projector 11a and a second projector 11b are provided. Light is directed onto the first HOE 9a by means of the first projector 11a and diffracted by it towards an eyebox 14. The scattering lobe of a single segment or pixel of the first HOE 9a is identified by the reference numeral 5a. Light is directed onto the second HOE 9b by means of the second projector 11b and diffracted by it towards the eyebox 14. The scattering lobe of a single segment or pixel of the second HOE 9b is identified by the reference numeral 5b.Using the present variant, content from two or more different projectors 11a, 11b can be projected into a common eyebox 14.

[0052] In the variants shown in Figures 3 to 5, the HOEs 9, 9a, 9b used are each designed to be reflective.

[0053] Two further variants of a head-up display 10 are described below with reference to Figures 6 and 7. In each variant, different content is projected into two different eyeboxes 14a and 14b by means of a single projector 11 or by means of several separate projectors forming a projector unit 11, in combination with a display 8 comprising at least one HOE 9. In both variants, light is directed from the projector 11 onto a holographic optical element 9, with the HOE 9 in Figures 6 and 7 being the

[0054] The HOE 9 is designed to be either transmissive or reflective. Using the HOE 9, the incident light is selectively diffracted towards a reflective optical element 19. A resulting virtual image of the HOE 9 is designated by the reference numeral 20.

[0055] In the variant shown in Figure 6, the diffraction of light at the HOE 9 occurs selectively depending on the wavelength or frequency of the light. In other words, light of a first wavelength is diffracted in a first direction to form the first eyebox 14a, and light of a second wavelength is diffracted in a second direction, which differs from the first direction, to form the second eyebox 14b. This is characterized by the beam paths 21 (representative of the first wavelength) and 22 (representative of the second wavelength).

[0056] In the variant shown in Figure 7, the diffraction of light at the HOE 9 occurs selectively depending on the polarization of the light. In other words, light of a first polarization, e.g., right-circularly polarized light, is diffracted in a first direction to form the first eyebox 14a, and light of a second polarization, e.g., left-circularly polarized light, is diffracted in a second direction, which differs from the first direction, to form the second eyebox 14b. This is characterized by the beam paths 21 (representative of the first polarization) and 22 (representative of the second polarization). It is also possible to use other polarizations, for example, various linear polarizations or combinations of circular and linear polarization, for selection.For this purpose, several projectors can be used and / or a projector can be used that is designed to emit differently polarized light simultaneously or using time-division multiplexing. Furthermore, a polarization-sensitive volume diffraction grating with high efficiency and a large diffraction angle is described in the document Weng, Yishi, et al. “Polarization volume grating with high efficiency and large diffraction angle.” Optics Express Vol. 24, No. 16 (08.08.2016), 17746-17759, to which reference is hereby made. Z50431-WO 14 PATERIS.

[0057] The variants shown in Figures 6 and 7 have the advantage that, using only one projector 11 or a projector unit 11 comprising several projectors, and only one HOE 9, multiple eyeboxes 14a, 14b can be formed into which different content can be projected. The HOE 9 can each be configured as a multiplex HOE.

[0058] Figure 8 schematically shows a general form of an optical arrangement 7 according to the invention in the form of a block diagram. The optical arrangement 7 comprises at least one projector 11 and a display 8, which includes at least one HOE 9. As already described in detail above, the HOE 9 is segmented such that for each segment at least one scattering lobe of the diffracted light is defined spatially in such a way that at least one eyebox with a predetermined boundary is generated. Z50431-WO 15 PATERIS

[0059] Reference symbol list:

[0060] 1 Display

[0061] 2 pixels

[0062] 3 pixels

[0063] 4. A user's eye

[0064] 5 Beam path

[0065] 6 Privacy Slide

[0066] 7 optical arrangement

[0067] 8 Display

[0068] 9 HOE

[0069] 10 Head-up display, transparent display 11 Projector / Projector unit / Beamer 12 Windshield

[0070] 13 HOE

[0071] 14 Eyebox

[0072] 14a Eyebox

[0073] 14b Eyebox

[0074] 15. Path of ambient light 16. Path of light

[0075] 17 Beam path

[0076] 18 Beam path

[0077] 19 reflective optical element

[0078] 20 virtual image of the HOE

[0079] 21 scatter club

[0080] 22 scatter club

Claims

Z50431-WO 16 PATERIS Patent claims 1. Optical arrangement (7) comprising at least one projector (11) and at least one display (8, 12, 19), wherein the at least one projector (11) and the at least one display (8, 12, 19) are arranged relative to each other such that light emitted from the projector (11) onto the display (8, 12, 19) is diffracted from the display (8, 12, 19) towards at least one eyebox (14), characterized by the fact that the display (8, 12, 19) comprises at least one holographic optical element (HOE) (9) whose diffraction grating structure comprises a plurality of segments and which is designed such that for each segment at least one diffraction lobe (5, 16-18, 21, 22) of the diffracted light is defined in a location-dependent manner such that at least one eyebox (14) with a predefined boundary is generated.

2. Optical arrangement (7) according to claim 1, characterized by the fact that the specified boundary of the eyebox (14) is formed as an edge at which the intensity of light projected by means of the projector (11) in the direction of the eyebox (14) drops to a value that is below a specified limit value.

3. Optical arrangement (7) according to claim 1 or 2, characterized by the fact that the display (8, 12, 19) and / or the holographic optical element (9) is designed to be transmissive and / or reflective.

4. Optical arrangement (7) according to one of claims 1 to 3, characterized by the fact that for a plurality of the segments of the at least one holographic optical element (9) at least one first scattering lobe (21) and at least one second scattering lobe (22) are defined, wherein the first scattering lobe (21) and the second scattering lobe (22) differ with respect to their geometry. Z50431-WO 17 PATERIS and / or differ from each other with respect to at least one feature of the diffracted light.

5. Optical arrangement (7) according to one of claims 1 to 4, characterized by the fact that for a plurality of the segments of the at least one holographic optical element (9) at least one first scattering lobe (21) and at least one second scattering lobe (21) are defined, wherein the first scattering lobe (21) generates a first eyebox (14a) and the second scattering lobe (22) generates a second eyebox (14b).

6. Optical arrangement (7) according to one of claims 4 or 5, characterized by the fact that the at least one first scattering lobe (21) and at least one second scattering lobe (22) differ from each other with respect to the wavelength and / or the angle of emission and / or the polarization of the diffracted light.

7. Optical arrangement (7) according to any one of claims 1 to 6, characterized by the fact that that at least one holographic optical element (9) is designed as a multiplex HOE or as a stack of several holographic optical elements.

8. Optical arrangement (7) according to any one of claims 1 to 7, characterized by the fact that the optical arrangement (7) comprises at least one first projector (11a) and at least one second projector (11b) and the at least one holographic optical element (9) of the display (8, 12) is designed such that it diffracts light incident from the first (11a) and the second projector (11b) in such a way as to form a common eyebox.

9. Optical arrangement (7) according to any one of claims 1 to 8, characterized by the fact that Z50431-WO 18 PATERIS the optical arrangement (7) is designed as an optical arrangement of a head-up display (10) or a head-mounted display or a display board or a screen.

10. Head-up display (10) comprising an optical arrangement (7) according to any one of claims 1 to 9.

11. Head-up display (10) according to claim 10, characterized by the fact that the head-up display (10) is designed as a head-up display (10) of a vehicle.

12. Transparent display (10) comprising an optical arrangement (7) according to any one of claims 1 to 9.

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