Vehicle-mounted projection display system and holographic projection system

Abstract

The present application discloses a vehicle-mounted projection display system and a holographic projection system. The vehicle-mounted projection display system comprises an image display unit and a holographic element. The image display unit is used for image display; the holographic element is located on a light exit side of the image display unit; the holographic element receives light emitted by the image display unit, and performs diffraction imaging on incident light; finally, a windshield reflects imaging light to a human eye. The holographic element has the function of a lens, and miniaturization of a projection system is achieved.

Description

In-vehicle projection display system and holographic projection system

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent applications filed with the State Intellectual Property Office of China on January 8, 2024, with application number 202410031839.5, filed with the State Intellectual Property Office of China on February 23, 2024, with application number 202420339334.0, filed with the State Intellectual Property Office of China on February 23, 2024, with application number 202410203465.0, and filed with the State Intellectual Property Office of China on March 27, 2024, with application number 202410361639.6, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of projection technology, and in particular to a vehicle-mounted projection display system and a holographic projection system. Background Art

[0004] Holographic Optical Elements (HOEs), also known as holographic elements, holographic optical films, and holographic films, are optical elements made based on the principles of holography. HOEs have a periodic microstructure that can be considered a Bragg grating structure. For a light beam incident on an HOE, the HOE can split the beam into multiple beams and recombine the multiple beams to form a diffraction pattern. This diffraction pattern is caused by phase differences in the light beams, which are caused by changes in the refractive index of the grating when the light beam passes through the grating inside the HOE.

[0005] Since HOE can focus a light beam to a point or spread it to an area, thus forming a diffraction pattern, it can be used to make holographic lenses. HOE can be applied in a variety of scenarios, for example, HOE can be used in vehicle-mounted projection display systems.

[0006] Summary of the Invention

[0007] Some embodiments of the present application provide a vehicle-mounted projection display system, including:

[0008] An image display unit, used for image display;

[0009] a holographic element located on the light-emitting side of the image display unit; the holographic element receives the light emitted by the image display unit, diffracts the incident light into an image, and emits the image toward the windshield, so that the diffracted light is reflected by the windshield to the human eye;

[0010] The display surface of the image display unit forms a set angle with respect to the plane where the holographic element is located.

[0011] Some embodiments of the present application further provide a holographic projection system, including:

[0012] An image source, configured to emit a projection light beam carrying image information;

[0013] A diffusion element and a holographic element are both located in the optical path of the projection light beam, the diffusion element is used to expand the projection light beam, and the holographic element is used to form an image based on the expanded projection light beam;

[0014] A beam adjustment element is located in the optical path between the diffusion element and the image source, and is used to input the first light beam and adjust the output second light beam; the difference in angular expansion between the center and edge of the spot of the second light beam is smaller than the difference in angular expansion between the center and edge of the spot of the first light beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 is a schematic diagram showing the principle of a holographic element provided in an embodiment of the present application serving as a holographic lens for recording information;

[0016] FIG2 is a schematic diagram showing the principle of a holographic element provided in an embodiment of the present application as a holographic lens to reproduce information;

[0017] FIG3 is a schematic structural diagram of a HUD system in related art;

[0018] FIG4 is a schematic diagram of a structure of a holographic projection system according to an embodiment of the present application;

[0019] FIG5 is a schematic diagram of a structure of an image display unit according to an embodiment of the present application;

[0020] FIG6 is a second structural diagram of an image display unit provided in an embodiment of the present application;

[0021] FIG7 is one of the object-image relationship diagrams provided in an embodiment of the present application;

[0022] FIG8 is a schematic diagram of the angle variation range of the diffusion element provided in an embodiment of the present application;

[0023] FIG9 is a second schematic diagram of the object-image relationship provided in an embodiment of the present application;

[0024] FIG10 is a schematic diagram of the position variation range of the diffusion element provided in an embodiment of the present application;

[0025] FIG11 is a curve showing the corresponding relationship between object distance and image distance provided in an embodiment of the present application;

[0026] FIG12 is an architecture diagram of a holographic projection system provided in an embodiment of the present application;

[0027] FIG13 is a second structural diagram of the holographic projection system provided in an embodiment of the present application;

[0028] FIG14 is a partially enlarged structural diagram of a holographic projection system provided in an embodiment of the present application;

[0029] FIG15 is a third structural diagram of the holographic projection system provided in an embodiment of the present application;

[0030] FIG16 is a fourth structural diagram of the holographic projection system provided in an embodiment of the present application;

[0031] FIG17 is a fifth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0032] FIG18 is a sixth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0033] FIG19 is a seventh structural diagram of a holographic projection system provided in an embodiment of the present application;

[0034] FIG20 is an eighth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0035] FIG21 is a ninth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0036] FIG22 is a tenth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0037] FIG23 is an eleventh structural diagram of a holographic projection system provided in an embodiment of the present application;

[0038] FIG24 is a schematic diagram showing the change in diffusion angle of projection light on a diffusion element according to an embodiment of the present application;

[0039] FIG25 is a schematic diagram of a partially enlarged structure of a first Fresnel lens provided in an embodiment of the present application;

[0040] FIG26 is a schematic diagram of light beam convergence of a first Fresnel lens provided in an embodiment of the present application;

[0041] FIG27 is a second schematic diagram of a partially enlarged structure of the first Fresnel lens provided in an embodiment of the present application;

[0042] FIG28 is a twelfth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0043] FIG29 is a thirteenth structural diagram of a holographic projection system provided in an embodiment of the present application;

[0044] FIG30 is a schematic diagram of the internal structure of a holographic element provided in an embodiment of the present application;

[0045] FIG31 is a schematic flow chart of a method for determining manufacturing parameters of a holographic element according to an embodiment of the present application;

[0046] FIG32 is a schematic diagram of a simulation scenario provided in an embodiment of the present application;

[0047] FIG33 is a schematic diagram of detecting the intensity distribution of light beams of different wavelengths at different angles using a far-field monitor according to an embodiment of the present application;

[0048] FIG34 is a schematic diagram showing angle and intensity distribution of light beams of multiple wavelengths according to an embodiment of the present application;

[0049] FIG35 is a second schematic diagram of angle and intensity distribution of light beams of multiple wavelengths provided in an embodiment of the present application;

[0050] FIG36 is a third schematic diagram of angle and intensity distribution of light beams of multiple wavelengths provided in an embodiment of the present application;

[0051] FIG37 is a schematic flow chart of a method for preparing a holographic element according to an embodiment of the present application;

[0052] FIG38 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to make the purpose and implementation of this application clearer, the exemplary implementation of this application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of this application. Obviously, the described exemplary embodiments are only part of the embodiments of this application, not all of the embodiments.

[0054] A holographic optical element can also be called a holographic element, a holographic film, etc., and its working principle is a holographic lens. A holographic lens refers to recording the information of a lens in a three-dimensional photosensitive material in a "holographic" manner, hence the name holographic lens. A three-dimensional photosensitive material is an organic material whose refractive index changes when exposed to light of a certain intensity. The working principle of a holographic element as a holographic lens can be seen in FIG1 , which is a schematic diagram of the principle of recording information by a holographic element as a holographic lens provided in an embodiment of the present application.

[0055] As shown in Figure 1, interference fringes are recorded in the holographic lens by interfering a reference beam (a parallel light wave without lens information) with an object beam (spherical waves, focused spherical waves with lens information). The reference beam can be a parallel light wave without lens information, and the object beam can be a focused spherical wave with lens information.

[0056] FIG2 is a schematic diagram showing the principle of the holographic element provided in an embodiment of the present application being used as a holographic lens to reproduce information.

[0057] As shown in Figure 2, when the reproduction beam is incident on the holographic element at the angle and wavelength of the reference light, the holographic element will exhibit the function of the recorded lens, converting the incident parallel light reproduction beam into a reconstructed focused spherical wave, thereby reproducing the image.

[0058] Holographic elements can be applied to in-vehicle projection display systems, for example, in heads-up displays (HUDs). HUD technology was first used on military aircraft and has gradually penetrated the automotive field with technological development and expansion. In addition to replacing instrument clusters and displaying various dashboard information (such as speed, tire pressure, fuel consumption, speed limits, and warnings), HUDs can also display navigation, assisted driving, and autonomous driving information previously displayed on the central control multimedia screen. This allows drivers to almost completely avoid looking down while driving, greatly improving driving safety.

[0059] FIG3 is a schematic structural diagram of a HUD system in related art.

[0060] As shown in FIG3 , a HUD system typically includes an image source 101 and at least one curved reflector q. The image source 101 projects an image onto the curved reflector q, and the image is reflected by the curved reflector q onto the windshield. The windshield then reflects the image to the human eye, and the human eye can view a magnified virtual image in front of the windshield.

[0061] HUD systems, based on the geometric optics of free-form surfaces, suffer from drawbacks such as a small field of view and a short imaging distance. When driving on a highway, the road is 3.5 meters wide. To overlay the displayed information on the traffic environment of two lanes, the head-up display's horizontal field of view must be at least 20°, and the display distance must be greater than 7 meters. Current HUDs cannot meet these requirements. Furthermore, if a HUD system were to achieve a field of view of 10° × 5° and a virtual image distance of 10 meters, its volume would be over 25L, as shown in Figure 3. The HUD would need to be located below the center console. However, the center console's limited space makes such a large HUD too complex to accommodate, significantly increasing the design complexity. Since the windshield is a free-form surface, the curved mirror q in the HUD must be extremely precise to produce an undistorted image, making mass-produced and modularized HUD manufacturing difficult.

[0062] Furthermore, current HUD systems typically have a fixed depth of field, meaning the image can only be projected at a fixed location. Furthermore, the image displayed by current head-up displays is often perpendicular to the road, failing to closely align with it, creating a sense of distance between the image and the road. Incorrect distance displays on the HUD can affect the driver's perception of the true distance to obstacles, potentially creating a dangerous situation.

[0063] Based on the above problems, an embodiment of the present application provides a holographic projection system, which can be specifically a vehicle-mounted projection display system, which can not only reduce the system volume, but also make the displayed image more closely aligned with the road surface.

[0064] FIG4 is one of the structural schematic diagrams of the holographic projection system provided in an embodiment of the present application.

[0065] As shown in FIG4 , the vehicle-mounted projection display provided by the embodiment of the present application includes: an image display unit 10 and a holographic element 20 .

[0066] The image display unit 10 is used for image display. The holographic element 20 is located on the light-emitting side of the image display unit 10. The holographic element 20 receives the light emitted by the image display unit 10, diffracts the incident light into an image, and emits it toward the windshield. Finally, the windshield reflects the imaging light to the human eye.

[0067] In the embodiment of the present application, the holographic element is a HOE, which is a diffraction optical element made according to the holographic principle. It can not only reproduce the object light wave using the diffraction method, but also has the functions of a lens and a reflector. The holographic element 20 can be exposed on a photosensitive film material using double-beam interference, which reduces processing costs, is thin, and occupies very little space. It can be directly attached to the center console. Accordingly, the image display unit 10 can be fixed on the roof, and the image light emitted from the roof reaches the holographic element 20, which then diffracts the light and forms an image that is reflected onto the windshield. Finally, the windshield reflects the imaging light to the human eye, forming an enlarged long-distance virtual image. As a result, there is no need to dig a groove in the center console to place the HUD system, and almost no center console space is occupied, greatly reducing the volume of the vehicle-mounted projection display system.

[0068] The holographic element 20 functions as a lens, and a suitable focal length can be designed according to the application scenario to satisfy the object-image relationship of the lens. In an embodiment of the present application, as shown in FIG4 , the image display unit 10 includes an image source 101 and a diffusion element 102. The image source 101 is used for image display, and the diffusion element 102 is located on the light-emitting side of the image source 101 and is used to diffuse the incident light. Due to the presence of the diffusion element 102, the image emitted by the image source 101 can be scattered and diffused, resulting in a more uniform light distribution. The divergence angle of the light after passing through the diffusion element 102 is different from the divergence angle of the light emitted by the image source 101. When designing the focal length of the holographic element 20, the light-emitting surface of the diffusion element 102 is used as the display surface of the image display unit 10, which is also the object surface; and the position of the image finally viewed by the human eye is the image surface, and the projection system satisfies the object-image relationship.

[0069] When the focal length of the holographic element 20 is constant and the object distance changes, the image distance also changes accordingly. This change in image distance will cause the position of the image perceived by the human eye to change. The present embodiment utilizes this object-image relationship to position the display surface of the image display unit 10, i.e., the plane where the diffusion element 102 resides, at a set angle to the plane where the holographic element resides. This positions one side of the diffusion element 102 closer to the holographic element 20 and the other side farther away from the holographic element 20. This results in different object distances between the diffusion element 102 and the holographic element 20 at different positions, and thus different image distances for the virtual image formed at different positions. Ultimately, the image perceived by the human eye is no longer perpendicular to the road surface, but rather tilted at a certain angle. This allows for different depths of field to be displayed within the same image, better matching actual road conditions.

[0070] Specifically, the holographic element 20 is a diffractive optical element. The incident angle and wavelength of the incident light significantly influence the diffraction efficiency. Therefore, in the embodiment of the present application, the image source 101 utilizes a laser projection device, which uses a laser light source. Laser light sources have characteristics such as high brightness and narrow bandwidth, making them suitable for use with holographic optical elements. To achieve full-color display, the laser light source can be a three-color laser light source, with the three primary wavelengths of red light (643nm±3nm), green light (522nm±3nm), and blue light (461nm±3nm), with the wavelength bandwidth being as small as possible. The projection device can utilize a digital light processing (DLP) system or a laser beam scanning (LBS) system, with a luminous flux of at least 100lm.

[0071] Light emitted from the image source 101 produces an image of a certain size on the diffusion element 102, which then projects the image onto the holographic element 20. Figure 5 is a schematic diagram of the structure of an image display unit according to an embodiment of the present application; Figure 6 is a schematic diagram of the structure of an image display unit according to an embodiment of the present application.

[0072] As shown in Figure 5, the primary function of the diffusion element 102 is to change the propagation direction of light, scattering or diffusing it, thereby achieving a more uniform light distribution. The diffusion element 102 is typically evaluated using three optical metrics: diffusion angle, transmittance, and haze. The diffusion angle affects image uniformity; a larger angle results in a more pronounced homogenization effect, but also reduces light utilization. Transmittance and haze are related; increasing the haze value reduces transmittance. To maximize image uniformity and light utilization, the diffusion element 102 and image source 101 require appropriate design.

[0073] As shown in FIG5 , the relationship between the projection ratio of the image source 101 and the diffusion angle of the diffusion element 102 is as follows: if the image source 101 is a projection device with a projection angle α and the diffusion angle of the diffusion element 102 is γ, then the divergence angle β of the light emitted from the diffusion element 102 is:

[0074] The angle of the main light beam projected from image source 101 onto diffuser 102 gradually increases as the diffuser increases in size. This, after being diffused by diffuser 102, results in uneven brightness, with high brightness in the center and low brightness around the edges. To address this issue, a collimated beam emitted from image source 101 theoretically achieves better homogenization and diffusion. As shown in Figure 6, a collimating lens 103 can be added between image source 101 and diffuser 102; collimating lens 103 can collimate the light emitted from image source 101.

[0075] In specific implementations, the windshield exhibits polarization selectivity, thereby preventing problems such as excessive ambient light or glare. Embodiments of the present application utilize this characteristic of the windshield to adjust the polarization direction of light emitted by image source 101. If the windshield can reflect incident first linearly polarized light and transmit incident second linearly polarized light, typically the first linearly polarized light can be s-polarized light and the second linearly polarized light can be p-polarized light. The polarization direction of s-polarized light is perpendicular to the plane of incidence, while the polarization direction of p-polarized light is parallel to the plane of incidence. Therefore, the polarization directions of the first and second linearly polarized light are perpendicular to each other. When image source 101 utilizes a laser projection device, the laser light emitted by the laser source is polarized light, typically either p-polarized or s-polarized light. Therefore, when applied to the in-vehicle projection display system provided by embodiments of the present application, the laser light emitted by the laser source can be adjusted to the first linearly polarized light, i.e., s-polarized light. This not only satisfies the characteristics of holographic element 20 but also improves the windshield's reflectivity of the projection light, thereby enhancing the brightness of the displayed image.

[0076] FIG7 is one of the object-image relationship diagrams provided in an embodiment of the present application.

[0077] In the embodiment of the present application, the light emitted by the image source 101 needs to be diffused by the diffusion element 102 before entering the holographic element 20. Therefore, the light-emitting surface of the diffusion element 102 serves as the display surface of the image display unit 10. When the holographic element 20 has a certain focal length, it also serves as the object plane of the holographic element 20. The position of the image viewed by the human eye is the image plane of the holographic element 20. According to Figure 7, the object-image relationship of the holographic element 20 satisfies:

[0078] Wherein, D2 represents the distance from the diffusion element 102 to the holographic element 20, i.e., the object distance; if the distance from the holographic element 20 to the windshield is not considered, then D3 represents the distance from the holographic element 20 to the virtual image, i.e., the image distance; and f represents the focal length of the holographic element 20.

[0079] It can be seen from the above-mentioned object-image relationship that the focal length of the holographic element 20 needs to be designed accordingly according to the application scenario of the holographic projection system. After the design of the holographic element 20 is completed, its focal length f is fixed.

[0080] During implementation, the object distance D2 and image distance D3 require comprehensive consideration. Object distance D2 represents the distance between the diffuser element 102 and the holographic element 20. This distance should be neither too close nor too far. Too close obstructs the driver's view, while too far hinders installation. Depending on the specific application scenario, the distance between the diffuser element 102 and the holographic element 20 can be set to 500mm, and the image distance D3 to 8000mm. Based on the aforementioned object-image relationship, the focal length f of the holographic element 20 can be determined to be approximately 533.3mm.

[0081] The magnification M of the virtual image can be determined according to the following relationship:

[0082] M = D3 / D2;

[0083] The object size is the size L1 of the image projected on the diffusion element 102, and the virtual image size L3 = M × L1. The virtual image distance (VID) of the holographic projection system refers to the distance between the virtual image and the human eye during actual observation, which is D3 + D4 in Figure 7. D4 is the distance from the windshield to the human eye. Based on actual application scenarios, D4 = 700mm. Once the system's object distance D2, focal length f, and image distance are determined, the VID of the HUD system can be calculated.

[0084] In addition, after determining the above distance, the field of view angle of the HUD system can be calculated according to the following formula:

[0085] FOV=2arctan[L3 / (2(D3+D4))];

[0086] Among them, FOV represents the field of view of the HUD system, L3 represents the imaging size, and D3+D4 represents the virtual image distance (i.e., VID). Based on the above-determined values, it can be calculated that the field of view of the vehicle-mounted projection display system provided in the embodiment of the present application can reach 13.6°.

[0087] If the effective imaging area of ​​the diffuser 102 is 120 mm × 60 mm, that is, the short side L1 of the diffuser 102 is 60 mm, then rotating the diffuser 102 with the center point of the short side of the diffuser 102 as the rotational symmetry axis can change the angle of the diffuser 102 relative to the holographic element 20, so that one side of the diffuser 102 is closer to the holographic element 20 and the other side is farther away from the holographic element 20. As a result, the virtual image formed is no longer perpendicular to the road surface, but is tilted at a certain angle. In this way, different depths of field can be displayed on the same image, thereby better matching actual road conditions.

[0088] FIG8 is a schematic diagram of the angle variation range of the diffusion element provided in an embodiment of the present application.

[0089] As shown in FIG8 , the angle θ between the diffusion element 102 and the holographic element 102 can be greater than or equal to 0°, or less than or equal to 30°. In a specific implementation, the angle of the diffusion element 102 can be rotated to maintain a degree at which the virtual image formed by the HUD system can completely fit the ground, and then the angle of the diffusion element 102 can be fixed.

[0090] When the angle between the diffuser 102 and the holographic element 102 is 30°, the upper and lower edges of the diffuser 102 will move -15 mm and +15 mm away from the holographic element 20, respectively. The image distances of the upper and lower edges of the formed virtual image will be 15 m and 5.36 m, respectively. This means that the upper edge of the virtual image is farther from the human eye, while the lower edge is closer, allowing the virtual image to fit closely with the road. The virtual image distance (VID) can be continuously varied between 6.06 m and 15.7 m.

[0091] FIG9 is a second schematic diagram of the object-image relationship provided in an embodiment of the present application; FIG10 is a schematic diagram of the position change range of the diffusion element provided in an embodiment of the present application.

[0092] As shown in FIG9 , the image source 101 and the diffusion element 102 may be solidified into an integral component, namely, the image display unit 10. A driving device connected to the image display unit 10 may also be provided in the vehicle-mounted projection display system; the driving device may drive the image display unit 10 to move, thereby changing the relative position of the image display unit 10 and the holographic element 20. When the relative position of the image display unit 10 and the holographic element 20 changes, the object distance changes, thereby causing the image distance to change accordingly, thereby realizing image display with variable focal depth.

[0093] As shown in FIG10 , the driving device can drive the image display unit 10 to move closer to or farther away from the holographic element 20 , so that the distance between the image display unit 10 and the holographic element 20 changes, thereby causing the virtual image distance VID to change accordingly.

[0094] If the image display unit 10 is at the focal position of the holographic element 20 as the coordinate origin, the image distance D3 at this time is 8000mm. When the image display unit 10 moves 10mm in the direction away from the holographic element 20, that is, D2 becomes 510mm, and at this time, it can be determined based on the object-image relationship that the image distance D3 becomes 11.67m. Under normal circumstances, when the human eye observation distance is greater than 10m, it can be considered that the focal length corresponding to the human eye is infinity. When the image display unit 10 moves 30mm in the direction close to the holographic element 20, that is, D2 becomes 470mm, and at this time, it can be determined based on the object-image relationship that the image distance D3 becomes 3.96m. The image display unit 10 can move continuously within the above range. The corresponding relationship between the object distance D2 and the image distance D3 is shown in Figure 11. The image distance D3 can change continuously within the range of the two end points of the curve.

[0095] When the holographic projection system is applied to the application scenarios of the above-mentioned embodiments of the present application, the movement range of the image display unit 10 is from -10 mm to 30 mm, and the range of change of the distance between the display surface of the image display unit 10 (i.e., the light-emitting surface of the diffusion element 102) and the holographic element 20 (a in FIG10 ) is 470 mm to 510 mm. Accordingly, the virtual image distance VID from the human eye to the observed image can be continuously changed within the range of 4.66 m to 12.37 m.

[0096] When the angle between the diffusion element 102 and the holographic element 102 is 30°, the image display unit 10 as a whole can be moved forward and backward by 5 mm in the direction of approaching or moving away from the holographic element 20. At this time, the distance from the upper edge of the virtual image to the human eye (VID) is 21.5 m, and the distance from the lower edge of the virtual image to the human eye (VID) is 5.5 m. The image distance of the virtual image continuously changes between 4.8 m and 20.8 m.

[0097] It is worth noting that the embodiments of the present application are exemplified by data for one type of vehicle. When applied to different vehicle models and different scenarios, data such as object distance, image distance, and focal length may change. Accordingly, the range of variation of the depth of field of the virtual image formed will also change accordingly.

[0098] FIG12 is an architecture diagram of a holographic projection system provided in an embodiment of the present application.

[0099] As shown in FIG12 , the holographic projection system further includes: a driving device 30 , an eye tracking device 50 , a three-dimensional panoramic measurement device 60 and a processor 40 . The eye tracking device 50 and the three-dimensional panoramic measurement device 60 are both connected to the processor 40 .

[0100] The 3D panoramic measurement device 60 is used to obtain 3D road information and transmit it to the processor. This 3D road information can include 3D information of vehicles, buildings, pedestrians, and lanes. The eye tracking device 50 is used to obtain eye information and transmit it to the processor. This eye information can include the eye's focus distance. The processor 40 determines adjustment information for the image display unit 10 based on the 3D road information and the eye information, and transmits this adjustment information to the drive device 30. The drive device 30 then drives the image display unit 10 to move according to the adjustment information, thereby aligning the virtual image distance with the human eye's focus distance, achieving true virtual-real image fusion.

[0101] FIG13 is a second structural diagram of the holographic projection system provided in an embodiment of the present application, and FIG14 is a partially enlarged structural diagram of the holographic projection system provided in an embodiment of the present application.

[0102] In some embodiments, as shown in Figures 13 and 14 , the holographic projection system can still be applied to an in-vehicle projection display system, specifically comprising an image source 101, a reflective element 106, a diffuser 102, and a holographic element 20. Specifically, when the projection beam emitted by the image source 101 is reflected by the reflective element 106 and reaches the diffuser 102, the projection beam is expanded by the diffuser 102 and reaches the holographic element 20. The holographic element 20 is used to direct the image carried by the projection beam to the human eye, and the image seen by the human eye is a virtual image 104 formed in the far field.

[0103] However, the projection light beam emitted by the image source 101 is reflected by the reflective element 106 and reaches the diffusion element 102. Since the angular spread at the center of the projection light beam is smaller than the angular spread at the edge of the light beam, the angular spread at the edge of the projection light beam is further increased after the projection light beam is further expanded by the diffusion element 102. As a result, when the projection light beam reaches the holographic element 20, the diffusion angle of the projection light beam on the holographic element 20 deviates from the diffraction angle of the holographic element 20 itself. In addition, the diffusion angle of the projection light beam on the holographic element 20 deviates significantly from the diffraction angle of the holographic element 20 itself, thereby reducing the diffraction efficiency of the holographic element 20 and causing an uneven image to be seen by the human eye.

[0104] In response to the above technical problems, an embodiment of the present application further provides a holographic projection system, which arranges a beam adjustment element in the optical path between the image source and the diffusion element, and uses the beam adjustment element to adjust the projection light emitted by the image source, so that the difference in angular spread between the center and edge of the spot of the adjusted projection beam, i.e., the second beam, becomes smaller. Then, the second beam is expanded by the diffusion element and enters the holographic element. Since the difference in angular spread between the center and edge of the spot of the second beam becomes smaller, the difference in angular spread between the center and edge of the spot of the beam after expansion by the diffusion element can be reduced after the second beam is expanded by the diffusion element, which is beneficial to reducing the deviation between the diffusion angle of the projection beam incident on the holographic element and the diffraction angle of the holographic element itself, thereby improving the diffraction efficiency of the holographic element and improving the uniformity of the image seen by the human eye.

[0105] FIG15 is a third structural diagram of the holographic projection system provided in an embodiment of the present application.

[0106] As shown in FIG. 15 , the holographic projection system includes an image source 101 , a diffusion element 102 , a holographic element 20 and a beam adjustment element 105 .

[0107] The image source 101 may include a picture generation unit (PGU), which generates a projection beam carrying image information and emits the projection beam. Specifically, the image source 101 may be disposed in a projector, so that the projector can emit a projection beam carrying image information.

[0108] The diffusion element 102 is located in the optical path of the projection beam. The diffusion element 102 is used to receive the projection beam emitted by the image source 101 and expand the received projection beam. For example, the diffusion element 102 can be configured as a diffusion film, which receives the projection beam through the diffusion film to achieve beam expansion of the projection beam. The diffusion element 102 can also be configured as a diffusion wheel formed by a rotating diffusion sheet, which can expand the projection beam along the beam transmission path through rotational diffusion. In some embodiments, the diffusion element 102 can also be configured as other specific components that can achieve beam expansion of the projection beam, which is not limited in this embodiment of the present application.

[0109] The holographic element 20 is located in the optical path of the projection beam. The holographic element 20 is specifically used to receive the projection beam after being expanded by the diffusion element 102, form an image based on the expanded projection beam, and transmit the image to the human eye. The image seen by the human eye is a virtual image 104 formed in the far field.

[0110] The beam adjustment element 105 is located in the optical path of the projection beam and is used to receive the incident first beam, adjust the first beam, and then emit a second beam to adjust the angular spread difference between the center and edge of the projection beam's corresponding beam spot. Specifically, the adjustment result is that the angular spread difference between the center and edge of the second beam's spot is smaller than the angular spread difference between the center and edge of the first beam's spot.

[0111] In some embodiments, as shown in FIG15 , a beam shaping element 105 is disposed between the image source 101 and the diffusion element 102. Specifically, the projection beam emitted by the image source 101 passes through the beam shaping element 105, which is configured to receive the incident beam, i.e., the first beam, and shape the first beam to form an outgoing beam, i.e., the second beam. After the first beam is shaped by the beam shaping element 105, the difference in angular spread between the center and edge of the second beam's spot can be smaller than the difference in angular spread between the center and edge of the first beam's spot.

[0112] It should be noted that when the projection beam emitted by the image source 101 reaches the holographic element 20 through the beam transmission path, the projection beam has a corresponding target diffusion angle at the target edge position of the holographic element 20, while the holographic element 20 itself has a preset diffraction angle. Based on this, in the embodiment of the present application, the projection beam emitted by the image source 101 is adjusted by the beam adjustment element 105 and then expanded by the diffusion element 102 to the holographic element 20. This can reduce the difference between the target diffusion angle of the projection beam on the holographic element 20 and the preset diffraction angle of the holographic element 20 itself. For example, a preset difference threshold can be set to ensure that the difference between the target diffusion angle and the preset diffraction angle is less than the preset difference threshold, thereby facilitating the improvement of the diffraction efficiency of the holographic element 20 and enhancing the uniformity of the image perceived by the human eye.

[0113] Therefore, by providing the beam adjusting element 105, the projection beam can be adjusted before the diffusing element 102 diffuses the projection beam, so that the difference in angular spread between the center and the edge of the light spot of the adjusted projection beam, i.e., the second light beam, is reduced. After the second light beam is expanded by the diffusing element 102, it enters the holographic element 20. Since the difference in angular spread between the center and the edge of the light spot of the second light beam is reduced, the difference in angular spread between the center and the edge of the light spot of the second light beam after expansion by the diffusing element 102 can be reduced. This helps to reduce the deviation between the target diffusion angle of the projection beam incident on the holographic element 20 and the preset diffraction angle of the holographic element 20 itself, thereby helping to improve the diffraction efficiency of the holographic element 20 and enhance the uniformity of the image seen by the human eye.

[0114] As shown in Figures 13 and 14, when the projection beam emitted by the image source 101 passes through the reflective element 106 and directly reaches the diffuser 102, the angular spread at the center of the projection beam emitted by the image source 101 is smaller than the angular spread at the edges of the beam. As a result, the angular spread at the edges of the projection beam increases further after further expansion by the diffuser 102. As a result, after the projection beam is expanded by the diffuser 102 and then incident on the holographic element 20, the target diffusion angle of the projection beam at the holographic element 20 deviates significantly from the preset diffraction angle of the holographic element 20, thereby reducing the diffraction efficiency of the holographic element 20. However, in the embodiment of the present application, by adjusting the projection beam before it is diffused by the diffuser 102, the diffraction efficiency of the holographic element 20 is improved, thereby enhancing the uniformity of the image perceived by the human eye.

[0115] It should be noted that Figure 15 only shows the example of setting the beam adjustment element 105 between the image source 101 and the diffusion element 102. The beam adjustment element 105 can also be integrated with the diffusion element 102, for example, the beam adjustment element 105 can be integrated on the beam incident surface of the diffusion element 102.

[0116] Figure 16 is a fourth schematic diagram of the structure of the holographic projection system provided by an embodiment of the present application. As shown in Figure 16, the beam adjustment element 105 is integrated with the beam incident surface of the diffuser element 102. Thus, by integrating the beam adjustment element 105 with the diffuser element 102, the projection beam emitted by the image source 101 can be adjusted and expanded when it is incident on the diffuser element 102. The integration of the beam adjustment element 105 with the diffuser element 102 facilitates the miniaturization of the holographic projection system.

[0117] Figure 17 is a fifth schematic diagram of the structure of the holographic projection system provided in an embodiment of the present application. As shown in Figure 17, the beam adjustment element 105 is integrated with the beam exit surface of the diffuser element 102. Thus, by integrating the beam adjustment element 105 with the diffuser element 102, the projection beam emitted by the image source 101 can be adjusted and expanded when it is incident on the diffuser element 102.

[0118] Figure 18 is a sixth schematic diagram of the structure of the holographic projection system provided by an embodiment of the present application. As shown in Figure 18, two beam adjustment elements 105 can be provided: one beam adjustment element 105 is integrated with the beam incident surface of the diffuser element 102, and the other beam adjustment element 105 is integrated with the beam exit surface of the diffuser element 102. Thus, by integrating the beam adjustment element 105 with the diffuser element 102, when the projection beam emitted by the image source 101 is incident on the diffuser element 102, the projection beam can be adjusted and expanded.

[0119] In addition, by integrating two beam adjustment elements 105 on the diffusion element 102, when the projection light beam expanded by the diffusion element 102 is incident on the holographic element 20, the degree of proximity between the target diffusion angle of the projection light beam on the holographic element 20 and the preset diffraction angle of the holographic element 20 is further improved, thereby further improving the diffraction efficiency of the holographic element 20.

[0120] The holographic projection system provided in an embodiment of the present application provides a beam adjusting element 105 in the optical path between the image source 101 and the diffuser 102. The beam adjusting element 105 is used to adjust the projection light emitted by the image source 101 so that the difference in angular spread between the center and edge of the spot of the adjusted projection light beam, i.e., the second light beam, is reduced. The second light beam is then expanded by the diffuser 102 and incident on the holographic element 20. Since the difference in angular spread between the center and edge of the spot of the second light beam is reduced, the difference in angular spread between the center and edge of the spot of the expanded light beam after expansion by the diffuser 102 can be reduced. This helps reduce the deviation between the diffusion angle of the projection light beam incident on the holographic element 20 and the diffraction angle of the holographic element 20 itself, thereby improving the diffraction efficiency of the holographic element 20 and enhancing the uniformity of the image viewed by the human eye.

[0121] In some embodiments, the holographic projection system may also include a reflective element. Figure 19 is a seventh schematic diagram of the structure of the holographic projection system provided in an embodiment of the present application. As shown in Figure 19, a reflective element 106 is provided between the image source 101 and the beam adjustment element 105. The projection beam emitted by the image source 101 is incident on the reflective element 106, which then reflects the projection beam to the beam adjustment element 105.

[0122] Therefore, by providing the reflective element 106 between the image source 101 and the beam shaping element 105, the reflective element 106 can be used to reflect the projection beam emitted by the image source 101 onto the beam shaping element 105. The reflective element 106 can be used to deflect the projection beam emitted by the image source 101, which helps shorten the transmission path of the projection beam and thus facilitates the miniaturization of the holographic projection system.

[0123] In some embodiments, the reflective element 106 can be specifically configured as a reflector, which can reflect the projection light beam emitted by the image source 101 to the beam adjustment element 105. In some embodiments, the reflective element 106 can also be configured as other specific elements that can reflect the projection light, which is not limited in this embodiment of the present application.

[0124] FIG20 is an eighth structural schematic diagram of a holographic projection system provided in an embodiment of the present application. In some embodiments, as shown in FIG20 , a reflective element 106 is disposed between the beam adjusting element 105 and the diffuser 102 . The projection beam emitted by the image source 101 is incident on the beam adjusting element 105 , which adjusts the projection beam. The adjusted projection beam is then reflected by the reflective element 106 onto the diffuser 102 .

[0125] Therefore, by providing a reflective element 106 between the beam adjusting element 105 and the diffuser 102, the projection beam adjusted by the beam adjusting element 105 is reflected toward the diffuser 102. Utilizing the reflective element 106, the projection beam can be redirected, which helps shorten the beam projection transmission path, thereby facilitating a miniaturized holographic projection system.

[0126] Figure 21 is a ninth structural diagram of a holographic projection system provided in an embodiment of the present application. In some embodiments, as shown in Figure 21 , when the beam shaping element 105 is integrated with the beam incident surface of the diffuser 102, the reflective element 106 can be positioned between the beam incident surface of the diffuser 102 and the image source 101. Specifically, the projection beam emitted by the image source 101 is reflected by the reflective element 106 onto the beam shaping element 105 on the beam incident surface. After passing through the beam shaping element 105, the projection light is incident on the diffuser 102.

[0127] FIG22 is a tenth schematic diagram of the structure of a holographic projection system provided in an embodiment of the present application. In some embodiments, as shown in FIG22 , two beam adjustment elements 105 may be provided: one beam adjustment element 105 is disposed between the image source 101 and the reflective element 106, and the other beam adjustment element 105 is disposed between the reflective element 106 and the diffuser 102. Specifically, the projection beam emitted by the image source 101 is adjusted by one beam adjustment element 105. The adjusted projection beam is then reflected by the reflective element 106 to the other beam adjustment element 105 for further adjustment. The adjusted projection beam is then incident on the diffuser 102 via the projection beam transmission optical path.

[0128] Therefore, by providing two beam adjusting elements 105, it is helpful to reduce the target diffusion angle of the adjusted projection light beam when it reaches the holographic element 20 after being expanded by the diffusion element 102, so that the target diffusion angle of the adjusted projection light beam when it reaches the holographic element 20 is close to the preset diffraction angle of the holographic element 20, which is helpful to improve the diffraction efficiency of the holographic element 20 and improve the uniformity of the image seen by the human eye.

[0129] In addition, by combining the two beam adjustment elements, the diffraction efficiency of the holographic element 20 is improved, and the reflection element 106 can be used to deflect the projection beam, which is beneficial to shortening the projection beam transmission path, thereby facilitating the miniaturization of the holographic projection system.

[0130] It should be noted that Figures 13 to 22 only exemplarily illustrate schematic diagrams of the projection optical path of the holographic projection system, and do not constitute a limitation on the distance of the light beam transmission path between the various elements in the holographic projection system, nor do they constitute a limitation on the specific positions between the various elements.

[0131] In some embodiments, as shown in FIG. 15 to FIG. 22 , the beam adjustment element 105 may be configured as a first Fresnel lens, and the holographic element 20 may be configured as a second Fresnel lens.

[0132] FIG23 is a schematic diagram of the structure of the holographic projection system provided in an embodiment of the present application. As shown in FIG23 , the beam adjustment element 105 is configured as a first Fresnel lens 0105 , and the holographic element 20 is configured as a second Fresnel lens 0103 .

[0133] The focal length of the first Fresnel lens 0105 is smaller than the focal length of the second Fresnel lens 0103. In some embodiments, the focal length of the first Fresnel lens 0105 can be set to 80 mm to 150 mm, and the focal length of the second Fresnel lens 0103 can be set to 250 mm to 450 mm. This configuration allows the projection beam emitted by the image source 101 to be adjusted by the beam adjustment element 105, then expanded by the diffusion element 102 and incident on the holographic element 20. The holographic element 20 receives the incident projection light and forms an image, thereby improving the display quality.

[0134] Figure 24 is a schematic diagram showing the variation in the diffusion angle of the projection light on the diffusion element according to an embodiment of the present application. As shown in Figure 24 , the diffusion angle of the light beam at the upper edge of the diffusion element 102 is small, while the diffusion angle of the light beam at the center of the diffusion element 102 is large.

[0135] Figure 25 is a partial magnified schematic diagram of the structure of a first Fresnel lens provided in an embodiment of the present application. In some embodiments, as shown in Figure 25 , the first Fresnel lens 0105 has an annularly distributed microstructure 1051. When a projection beam is incident on the first Fresnel lens 0105, the annularly distributed microstructure 1051 on the first Fresnel lens 0105 is used to converge the projection beam.

[0136] Among them, the edge of the circularly distributed microstructure 1051 and the center of the circularly distributed microstructure 1051 have different convergence capabilities for projection light. Specifically, the edge of the circularly distributed microstructure 1051 has a greater convergence capability for projection light than the center of the circularly distributed microstructure 1051.

[0137] Figure 26 is a schematic diagram of light beam convergence by the first Fresnel lens provided in an embodiment of the present application. As shown in Figure 26, when the first Fresnel lens 0105 converges the incident projection light beam, the converging power at the edge of the first Fresnel lens 0105 is higher than the converging power at the center of the first Fresnel lens 0105.

[0138] Therefore, after adjustment by the beam adjustment element 105, the angular expansion difference between the center and edge of the outgoing beam can be smaller than the angular expansion difference between the center and edge of the incident beam, that is, the angular expansion difference between the center and edge of the second beam is smaller than the angular expansion difference between the center and edge of the first beam.

[0139] Figure 27 is a second partially enlarged schematic diagram of the structure of a first Fresnel lens provided in an embodiment of the present application. In some embodiments, as shown in Figure 27 , the first Fresnel lens 0105 includes microstructures 1052 distributed in a semicircular pattern. When a projection beam is incident on the first Fresnel lens 0105, the semicircular microstructures 1052 are used to converge the projection beam.

[0140] Among them, the edge of the semicircularly distributed microstructure 1052 and the center of the semicircularly distributed microstructure 1052 have different convergence capabilities for projection light. Specifically, the edge of the semicircularly distributed microstructure 1052 has greater convergence capability for projection light than the center of the semicircularly distributed microstructure 1052.

[0141] Therefore, after adjustment by the beam adjustment element 105, the angular expansion difference between the center and edge of the outgoing beam can be smaller than the angular expansion difference between the center and edge of the incident beam, that is, the angular expansion difference between the center and edge of the second beam is smaller than the angular expansion difference between the center and edge of the first beam.

[0142] In some embodiments, the second Fresnel lens can be configured as a holographic film or a grating, so that the holographic element 20 can form an image after receiving the projection light beam expanded by the diffusion element 102. This embodiment of the present application is not limited to this.

[0143] The holographic film can realize the display of images while allowing the human eye to see the virtual image 104 behind the holographic film. The grating is a thin sheet composed of strip lenses, which guides the image carried by the projection beam into the human eye.

[0144] FIG28 is a twelfth structural diagram of a holographic projection system provided in an embodiment of the present application. In some embodiments, as shown in FIG28 , the image source 101 includes a lens structure 107. The optical axis of the lens structure 107, the optical axis of the beam adjustment element 105, and the optical axis of the holographic element 20 are coaxial.

[0145] When the center of the image carried by the projection beam is in the central area of ​​the beam adjusting element 105, and when the center of the image carried by the projection beam is also in the central area of ​​the holographic element 20, the projection beam emitted by the image source 101 can be adjusted by the beam adjusting element 105 so that the angular expansion of the edge of the adjusted beam can be reduced.

[0146] When the center of the image carried by the projection beam is located on one side of the above-mentioned coaxial optical axis, the projection beam emitted by the image source 101 can be adjusted by the beam adjustment element 105 to reduce the angular expansion of the center of the adjusted beam and the angular expansion of the edge of the adjusted beam.

[0147] As shown in FIG29 , when a holographic element is applied to a HUD system, specifically an AR-HUD system, a laser projection module may be used as the image source. The laser projection module may emit a light beam containing vehicle information. The light beam emitted by the laser projection module passes through a reflector and a diffuser and is incident on the holographic element 20 of the front windshield. Since the working principle of the holographic element is a volume holographic lens, its function is equivalent to a reflective free-form mirror. Therefore, the light beam incident on the holographic element can be diffracted and converged into the driver's Eye Box, so that the driver can see the vehicle information by looking up.

[0148] The eye box range refers to the movable space within which the user's pupil can obtain complete image information. In Figure 29, the eye box range refers to the movable space within which the driver's pupil can obtain complete image information.

[0149] Vehicle information may include vehicle speed, speed limit, steering action, lane departure, guide lines and other information. The specific information can be set according to the actual situation of the vehicle.

[0150] The structure of the holographic element attached to the front windshield of the vehicle can be seen in FIG30 , which is a schematic diagram of the internal structure of the holographic element provided in an embodiment of the present application.

[0151] As shown in FIG30 , the thickness of the holographic element is d, and the Bragg grating structure is composed of alternating regions with a refractive index of n0 and regions with a refractive index of n1=n0+Δ, and the sum of the thicknesses of the regions with the two refractive indices is V.

[0152] The laser emitted by the laser emission module is irradiated onto the Bragg grating as the reproduced light. The Bragg grating is a periodic microstructure that performs Bragg grating diffraction on the incident light beam, splitting the light beam into multiple beams and recombining them to form a diffraction pattern, that is, an image containing vehicle information.

[0153] However, the period length of the Bragg grating structure of a holographic element is smaller than the wavelength of light, which disperses sunlight and other broad-spectrum ambient light, creating noticeable rainbow patterns on the holographic element. This creates rainbow patterns in the resulting image, potentially impacting driving safety. In other scenarios, the rainbow patterns produced by holographic optical elements can also affect the resulting image, resulting in a poor user experience.

[0154] To address the above issues, embodiments of the present application provide a method for determining parameters of a holographic element. This method uses multiple detection data within the user's eye box to determine whether rainbow patterns exist within the user's eye box. This method then determines target detection data from the multiple detection data as being free of rainbow patterns, and uses the target simulation parameters used to obtain this target detection data as the preparation parameters of the holographic element. This holographic element with this structure can be used in an AR-HUD system and attached to a vehicle's windshield, ensuring that the image formed by the holographic element has fewer or no rainbow patterns within the user's eye box, thereby improving the user experience.

[0155] Figure 31 is a flow chart of a method for determining fabrication parameters of a holographic element according to an embodiment of the present application. This method can be executed by software and / or hardware. For example, the hardware device can be a device for determining fabrication parameters of a holographic element, which can be a terminal or a processing chip in the terminal.

[0156] As shown in FIG31 , the method for determining the preparation parameters of the holographic element may include:

[0157] S11. Acquire multiple detection data of the holographic element in the target usage scenario, where the detection data is detection data within the user's eye box range obtained by simulation parameters in the target usage scenario, and any two of the multiple simulation parameters correspond to different structural parameters of the Bragg grating of the holographic element.

[0158] The usage scenarios of holographic elements may include AR-HUD systems, AR glasses and other scenarios, which are not limited in the embodiments of the present application.

[0159] The structural parameters of the Bragg grating of the holographic element include the Bragg grating period and the tilt angle of the holographic element.

[0160] The target usage scenario described in the embodiments of the present application can be an AR-HUD system or AR glasses, and the embodiments of the present application do not limit this.

[0161] For example, the plurality of detection data may be detection data within the user's eye box obtained by simulating the target usage scenario with different simulation parameters. The detection data may be used to determine whether rainbow lines appear within the user's eye box.

[0162] S12. Determine, among the plurality of detection data, a plurality of target detection data in which rainbow patterns do not exist within the user's eye box.

[0163] Exemplarily, the detection data may include the corresponding intensities of light beams of multiple wavelengths at multiple angles. When determining, among the multiple detection data, multiple target detection data indicating that rainbow patterns do not exist within the user's eye box, the maximum intensity of the light beam of each wavelength in the detection data may be determined for each detection data, and the center angle corresponding to the intensity maximum may be determined to obtain multiple intensity maxima and multiple center angles; the difference between the center angles of any two light beams of wavelengths may be calculated to obtain multiple first differences; the difference between the maximum intensity of the light beams of any two wavelengths may be calculated to obtain multiple second differences; if the multiple first differences are all less than a first preset value, and / or if any of the multiple second differences is greater than a second preset value, then the detection data is determined to be target detection data indicating that rainbow patterns do not exist within the user's eye box, and multiple target detection data are obtained.

[0164] The first preset value and the second preset value may be pre-set, and this embodiment of the present application does not limit this.

[0165] It is understood that if the detection data within the user's eye box contains rainbow patterns, it is possible that the maximum intensities of light beams of different wavelengths are similar, but the center angles corresponding to the maximum intensities are located at different positions. If the center angles of light beams of different wavelengths are relatively concentrated, then rainbow patterns will not exist within the user's eye box. Therefore, if the multiple first difference values ​​are all less than the first preset value, it can be determined that the corresponding detection parameters are target detection data without rainbow patterns.

[0166] It is understood that if, among the maximum intensities of light beams of different wavelengths detected within the user's eyebox, the maximum intensity of one or more wavelengths is significantly greater than the maximum intensities of light beams of other wavelengths, rainbow streaks will not be present within the user's eyebox. Therefore, if any of the multiple second difference values ​​is greater than the second preset value, the corresponding detection data can be determined to be target detection data without rainbow streaks.

[0167] In this way, whether rainbow stripes exist within the user's eye box is determined based on the distribution of the maximum intensity and central angle of different wavelengths after passing through the holographic element. Therefore, target detection data without rainbow stripes can be determined from multiple detection data.

[0168] S13. Determine multiple preparation parameters of the holographic element according to target simulation parameters corresponding to the multiple target detection data.

[0169] Since the target simulation parameters correspond to target detection data without rainbow patterns, and the target detection data is detected in the target usage scenario, when a holographic element is prepared using any one of a plurality of preparation parameters, the obtained holographic element will not have rainbow patterns within the user's eye box during use.

[0170] Exemplarily, the simulation parameters may include the incident angle of visible light and the structural parameters of the Bragg grating of the holographic element. When determining the multiple preparation parameters of the holographic element based on the target simulation parameters corresponding to the target detection data, the target incident angle of visible light corresponding to each target detection data in the multiple target detection data and the structural parameters of the target Bragg grating of the holographic element may be analyzed and processed to determine the object light phase corresponding to each target detection data, thereby obtaining multiple object light phases; and the multiple object light phases and the multiple Bragg grating structural parameters are determined as the multiple preparation parameters of the holographic element.

[0171] The incident angle of the visible light is the angle between the visible light and the plane where the holographic element is located. The visible light can be broad-spectrum visible light, and the wavelength of the visible light can be in the range of 400 nm to 700 nm.

[0172] The analysis and processing of the target incident angle of visible light corresponding to the target detection data and the structural parameters of the target Bragg grating of the holographic element may include a K-vector closure analysis method or a light intensity calculation method after light wave interference superposition. The embodiments of the present application do not limit the specific processing method.

[0173] In this way, since the phase of the object light and the structural parameters of the Bragg grating need to be set when preparing the holographic element, the phase of the object light and the corresponding structural parameters of the Bragg grating in the preparation parameters determined in this application are the phase of the object light and the structural parameters of the Bragg grating at which no rainbow patterns exist within the user's eye box. Therefore, when the holographic element prepared using the preparation parameters is used, no rainbow patterns exist within the user's eye box, which can improve the user experience.

[0174] Thus, the method for determining the preparation parameters of a holographic element provided in the embodiments of the present application determines whether rainbow patterns exist within the user's eye box using multiple detection data within the user's eye box, thereby determining target detection data indicating the absence of rainbow patterns from the multiple detection data, and determining the target simulation parameters used to obtain the target detection data as the preparation parameters of the holographic element. When the obtained preparation parameters are used to prepare a holographic element, the prepared holographic element will not exhibit rainbow patterns within the user's eye box during use, thereby improving the user experience. For example, if the prepared holographic element is used in a vehicle's AR-HUD system, it can enhance driver safety during driving.

[0175] In the embodiment of the present application, a plurality of detection data of the holographic element in the target usage scenario may be obtained in a simulation scenario. The following describes a method for obtaining the plurality of detection data.

[0176] For example, in a simulation scenario corresponding to a target usage scenario, visible light may be incident on multiple holographic elements at multiple incident angles, and the light beams passing through the holographic elements may be detected to obtain multiple detection data.

[0177] The simulated scene can be a scene that simulates the target usage scene. Since the appearance of rainbow patterns is mostly caused by visible light irradiating the holographic element, simulating with visible light makes the obtained detection data closer to the actual scene, thereby improving the accuracy of the obtained detection data.

[0178] For example, when detecting the light beam after passing through the holographic element, a monitor may be used to detect the light beam after passing through the holographic element, which is not limited in the embodiments of the present application.

[0179] For example, the detection data may include the corresponding intensities of light beams of multiple wavelengths at multiple angles. When detecting the light beam after passing through the holographic element to obtain multiple detection data, the light beam after passing through the holographic element may be subjected to far-field detection to obtain the corresponding intensities of the light beams of multiple wavelengths at multiple angles in the far field.

[0180] In this way, since the user's pupil may be far away from the holographic element, the detection data obtained by far-field detection is more consistent with the actual use scenario of the holographic element, which can further improve the accuracy of the obtained detection data.

[0181] Below, the method for determining the preparation parameters of the holographic element is described by taking the application of the holographic element in the AR-HUD system as an example. In the following description, the holographic element is referred to as HOE film for short.

[0182] The method for determining the preparation parameters of the holographic element may include the following steps:

[0183] Step 1: In the AR-HUD system, simulate the scenario where visible light at different incident angles is irradiated onto HOE films with different grating periods, and determine the intensity distribution of multiple wavelengths of dispersed light within the driver's eye box at different angles.

[0184] The incident angle of the visible light is the angle between the visible light and the plane where the HOE film is located. The visible light can be broad-spectrum visible light, and the wavelength of the visible light can be in the range of 400 nm to 700 nm.

[0185] Figure 32 is a schematic diagram of a simulation scenario provided in an embodiment of the present application.

[0186] As shown in Figure 32, the vehicle's front windshield is tilted 23° from the horizontal plane, with the HOE film applied to the vehicle's front windshield. The incident angle of the visible light in Figure 32 is 67°, which is vertical (perpendicular to the horizontal plane) and can be considered the angle of sunlight at noon.

[0187] The embodiment of the present application is only illustrated by taking the scenario shown in FIG32 as an example and does not constitute any limitation.

[0188] For example, as shown in FIG32 , a wide spectrum of visible light at different incident angles can be incident on the HOE film. A monitor can be set up on an initial plane parallel to the plane of the vehicle's front windshield to detect the intensity distribution corresponding to different angles in the far field of light beams of different wavelengths. The use of a monitor for detection is shown in FIG33 , which is a schematic diagram of detecting the intensity distribution of light beams of different wavelengths at different angles using a far-field monitor, as provided in an embodiment of the present application.

[0189] In FIG33 , the HOE film has a Bragg grating structure consisting of alternating regions with a refractive index of n0=1.5 and regions with a refractive index of n1=1.505, and the sum of the thicknesses of the regions with the two refractive indices is λ / (2nsinθ).

[0190] For example, when simulating the above scenario, electromagnetic simulation software such as FDTD, comsol, and RCWA may be used. The embodiment of the present application does not limit the software used for the simulation.

[0191] It should be noted that by simulating scenarios where visible light at different incident angles impinges on HOE films with different grating periods, the initial plane containing the angles of the multiple wavelengths of the dispersed light beams obtained is parallel to the plane of the vehicle's windshield, while the plane of the eyebox range is perpendicular to the horizontal plane. Therefore, based on the angle between the initial plane and the plane containing the eyebox range, the angles of the multiple wavelengths of the light beams obtained in the initial plane can be converted to the angles of the multiple wavelengths of the light beams within the eyebox range. Furthermore, the converted angles and intensities can be correlated to determine the angle and intensity distribution of the multiple wavelengths of the dispersed light beams within the driver's eyebox range.

[0192] It should be noted that since the structural parameters of the HOE mode include the Bragg grating period and the tilt angle, in the embodiment of the present application, different tilt angles can be simulated by the incident angle of light. Therefore, in the embodiment of the present application, only the Bragg grating period is described.

[0193] For example, the angle and intensity distributions of the light beams of multiple wavelengths obtained by chromatically dispersing light within the eye box can be seen in Figures 34, 35, and 36. Figure 34 is a first schematic diagram of the angle and intensity distributions of the light beams of multiple wavelengths provided in an embodiment of the present application. Figure 35 is a second schematic diagram of the angle and intensity distributions of the light beams of multiple wavelengths provided in an embodiment of the present application. Figure 36 is a third schematic diagram of the angle and intensity distributions of the light beams of multiple wavelengths provided in an embodiment of the present application.

[0194] Step 2: Determine multiple target incident angles and multiple target Bragg grating periods of visible light without rainbow fringes based on the intensity distribution of the light beams of multiple wavelengths at different angles.

[0195] Exemplarily, for the angle and intensity distributions of multiple wavelengths obtained under any visible light incident angle and any Bragg grating period, the maximum intensity of each wavelength and the center angle corresponding to the intensity maximum of each wavelength are determined, and the difference between the center angles of any two wavelengths is calculated to obtain multiple first differences. Furthermore, the difference between the intensity maximums of any two wavelengths is calculated to obtain multiple second differences. If the multiple first differences are all less than a first preset value, and / or if a second difference is greater than a second preset value among the multiple second differences, then the visible light angle and Bragg grating period under this scenario are determined to be multiple target incident angles and multiple target Bragg grating periods for visible light without rainbow fringes.

[0196] As shown in Figure 34 above, the center angles of different wavelengths are located at different positions. That is, the difference between the center angles of any two wavelengths is greater than the first preset value. Furthermore, the maximum intensities of the different wavelengths are similar, that is, the difference between the maximum intensities of any two wavelengths is less than the second preset value. Therefore, the incident angle of visible light and the Bragg grating period corresponding to Figure 34 are those at which rainbow fringes are present.

[0197] As shown in Figure 35 , the center angles of different wavelengths are similar in position, meaning the difference between the center angles of any two wavelengths is less than a first preset value. Furthermore, the maximum intensities of different wavelengths are similar in position, meaning the difference between the maximum intensities of any two wavelengths is less than a second preset value. Therefore, the incident angle of visible light and the Bragg grating period corresponding to Figure 35 are those at which rainbow fringes are absent.

[0198] As shown in Figure 36 above, the center angles of different wavelengths are located at different positions, meaning that the difference between the center angles of any two wavelengths is greater than a first preset value. Furthermore, the maximum intensities of different wavelengths differ, meaning that the difference between the maximum intensities of any two wavelengths is greater than a second preset value. Therefore, the incident angle of visible light and the Bragg grating period corresponding to Figure 36 are those at which rainbow fringes are absent.

[0199] Step 3: Calculate and obtain phase distributions of multiple object beams based on multiple target incident angles and multiple target Bragg grating periods.

[0200] Exemplarily, the incident angle and wavelength of the object light can be calculated based on multiple target incident angles and multiple target Bragg grating periods through the K-vector closure analysis method or the light intensity calculation method after light wave interference superposition, and the phase distribution of the object light can be determined based on the incident angle and wavelength of the object light.

[0201] Step 4: Store the multiple object light phase distributions and the multiple target Bragg gratings in a preparation parameter library.

[0202] Exemplarily, a plurality of object light phase distributions and corresponding target Bragg gratings are stored in a preparation parameter library, so that the parameters in the preparation parameter library can be used to subsequently fabricate the HOE film.

[0203] After the parameters of the holographic element are determined by the above method, the holographic element can be prepared using the parameters determined above. The following describes the method for preparing the holographic element. FIG37 is a flow chart of the method for preparing the holographic element provided in an embodiment of the present application. As shown in FIG37, the method for preparing the holographic element may include the following steps:

[0204] S21. Determine a target usage scenario of the holographic element, and obtain scene parameters corresponding to the target usage scenario.

[0205] Exemplarily, the scene parameters may include the wavelength, spectral width, imaging distance, phase distribution of the object light, parameters of the reflector used in the scene, parameters of the prism, parameters of the lens, etc. The specific parameters can be set according to the actual situation of the target usage scenario, and the embodiments of the present application are not limited to this.

[0206] S22. Determine a target preparation parameter from a plurality of preparation parameters corresponding to the target usage scenario according to the scenario parameter.

[0207] The multiple preparation parameters are obtained according to the method for determining the preparation parameters of the holographic element, which can be found in the above embodiments and will not be described in detail here.

[0208] Exemplarily, the scene parameters may include the phase of the target object light, and the preparation parameters include the phases of multiple object lights and the corresponding Bragg grating periods; when determining the target preparation parameters from the multiple preparation parameters corresponding to the target usage scene based on the scene parameters, the Bragg grating period corresponding to the phase of the target object light can be determined from the multiple preparation parameters based on the phase of the target object light; the phase of the target object light and the corresponding Bragg grating period are determined as the target preparation parameters.

[0209] Exemplarily, the phase of the target object light can be a free-form surface type continuous object light phase distribution calculated by optical design software such as Zemax, odeV, lighttools, or optical design methods such as iterative design. The continuous object light phase distribution includes the phases of multiple object lights, that is, the phase of the target object light includes the phases of multiple object lights.

[0210] According to the phases of multiple object beams in the continuous object beam phase distribution and the phase distribution of the object beam in the preparation parameters, the Bragg grating period corresponding to the phases of the multiple object beams can be determined in the preparation parameters, thereby determining the target preparation parameters of the holographic element.

[0211] It should be noted that since the above method for determining the fabrication parameters is based on simulation modeling, considering that a large amount of simulation data may place higher demands on the electronic equipment, and that the larger the area of ​​the holographic element, the more data the simulation requires, simulation can be performed on holographic elements with smaller areas.

[0212] Therefore, after obtaining the phase distribution of the free-form surface continuous object light, the phase distribution of the object light can be discretized to obtain multiple phase distributions of the object light, so that the corresponding Bragg grating period can be determined according to the phase distributions of the multiple object lights.

[0213] For example, when discretizing the phase distribution of the object light, it can be done based on parameters such as the area of ​​the holographic element used in the simulation when determining the preparation parameters, so as to match the Bragg grating period.

[0214] In this way, the corresponding Bragg grating period is determined by the phase distribution of the object light in the actual use scene, so that when a holographic element is prepared according to the phase of the object light and the corresponding Bragg grating period, the obtained holographic element will not have rainbow stripes within the user's eye box.

[0215] S23. Prepare a holographic element using target preparation parameters.

[0216] Exemplarily, the method for preparing a holographic element using the target preparation parameters can be seen in FIG1 , which will not be described in detail here.

[0217] In this way, according to the scene parameters in the actual target usage scenario, the target preparation parameters are determined from multiple preparation parameters, and the target preparation parameters are used to prepare the holographic element. Since the multiple preparation parameters are obtained in the absence of rainbow patterns, the prepared holographic element does not have rainbow patterns within the eye box range of the user in the target usage scenario.

[0218] It should be noted that in the above embodiments, only the Bragg grating period of the holographic element is involved in the calculation process, and its tilt angle is not involved. This is because the tilt angle has been taken into account in the process of simulating data, or the tilt angle is set to be the same. Therefore, the method described in the embodiments of the present application can be implemented by the Bragg grating period.

[0219] FIG38 is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. As shown in FIG38 , the electronic device 120 may include: at least one processor 1201 and a memory 1202 .

[0220] The memory 1202 is used to store programs. Specifically, the programs may include program codes, and the program codes include computer operating instructions.

[0221] The memory 1202 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0222] The processor 1201 is used to execute the computer-executable instructions stored in the memory 1202 to implement the data processing method described in the aforementioned method embodiment. Among them, the processor 1201 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application. Specifically, when implementing the method described in the aforementioned method embodiment, the electronic device may be, for example, an electronic device with processing capabilities, such as a terminal or a server.

[0223] Optionally, the electronic device 120 may further include a communication interface 1203. In a specific implementation, if the communication interface 1203, the memory 1202, and the processor 1201 are implemented independently, the communication interface 1203, the memory 1202, and the processor 1201 may be interconnected via a bus and communicate with each other. The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. Buses can be divided into address buses, data buses, control buses, etc., but this does not mean that there is only one bus or only one type of bus.

[0224] Optionally, in a specific implementation, if the communication interface 1203, the memory 1202 and the processor 1201 are integrated on a chip, the communication interface 1203, the memory 1202 and the processor 1201 can complete communication through an internal interface.

[0225] The present application also provides a computer-readable storage medium, which may include: a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes. Specifically, the computer-readable storage medium stores program instructions, and the program instructions are used in the methods in the above embodiments.

[0226] The present application also provides a program product, comprising execution instructions stored in a readable storage medium. At least one control module of a display device can read the execution instructions from the readable storage medium, and at least one control module executes the execution instructions to cause the display device to implement the methods for determining preparation parameters of holographic elements provided in the various embodiments described above.

[0227] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An in-vehicle projection display system, comprising: An image display unit for image display; A holographic element located on the light-emitting side of the image display unit; The holographic element receives the light emitted by the image display unit, diffracts and images the incident light, and emits it towards the windshield, so that the diffracted light is reflected by the windshield to the human eye; The display surface of the image display unit forms a set angle with respect to the plane where the holographic element is located.

2. The vehicle-mounted projection display system according to claim 1, wherein, The angle between the display surface of the image display unit and the plane where the holographic element is located is greater than or equal to 0°, and / or less than or equal to 30°.

3. The vehicle-mounted projection display system according to claim 2, wherein The relative position of the display surface of the image display unit and the holographic element is variable; the distance from the human eye to the observed image is greater than or equal to 4.66 m, and / or less than or equal to 21.5 m.

4. The vehicle-mounted projection display system according to any one of claims 1 to 3, wherein, The image display unit includes: An image source for image display; A diffusion element located on the light-emitting side of the image source for diffusing the incident light.

5. The vehicle-mounted projection display system according to claim 4, wherein, The image display unit further includes: A collimating lens located between the image source and the diffusion element; the collimating lens is used for collimating the light emitted by the image source.

6. The vehicle-mounted projection display system according to any one of claims 1 to 3, wherein, The holographic element is attached to the center console, and the image display unit is fixed to the roof of the vehicle.

7. The in-vehicle projection display system according to claim 4, wherein, The image source uses a laser projection device; The windshield reflects the incident first linearly polarized light and transmits the incident second linearly polarized light; the polarization directions of the first linearly polarized light and the second linearly polarized light are perpendicular to each other; The laser emitted by the laser projection device is linearly polarized light, and the polarization direction of the laser emitted by the laser projection device is parallel to the polarization direction of the first linearly polarized light.

8. The in-vehicle projection display system according to any one of claims 1 to 3, further comprising: A driving device connected to the image display unit; the driving device is used for driving the image display unit to approach or move away from the holographic element, so that the distance between the image display unit and the holographic element changes.

9. The vehicle-mounted projection display system according to claim 8, wherein, The display surface of the image display unit is parallel to the plane where the holographic element is located; the distance between the display surface of the image display unit and the holographic element is greater than or equal to 470 mm, and / or less than or equal to 510 mm, and the distance from the human eye to the observed image is greater than or equal to 4.66 m, and / or less than or equal to 12.37 m.

10. The in-vehicle projection display system according to claim 8, wherein, The angle between the display surface of the image display unit and the plane where the holographic element is located is 30°; the distance between the display surface of the image display unit and the holographic element is greater than or equal to 495 mm, and / or less than or equal to 505 mm, and the distance from the human eye to the observed image is greater than or equal to 5.5 m, and / or less than or equal to 21.5 m.

11. The in-vehicle projection display system according to claim 8, further comprising: A human eye tracking device, a three-dimensional panoramic measurement device and a processor, the human eye tracking device and the three-dimensional panoramic measurement device are both connected to the processor; The three-dimensional panoramic measurement device is used for acquiring three-dimensional information of the road and sending it to the processor, and the human eye tracking device is used for acquiring eye information and sending it to the processor; The processor determines adjustment information for the image display unit based on the three-dimensional information of the road and the eye information, and sends the adjustment information to the driving device to drive the image display unit to move according to the adjustment information.

12. A holographic projection system, comprising: An image source for emitting a projection beam carrying image information; A diffusion element and a holographic element, both located in the optical path of the projection beam, the diffusion element being used for expanding the projection beam, and the holographic element being used for imaging based on the expanded projection beam; A beam adjustment element located in the optical path between the diffusion element and the image source, for incident first beam and adjusting an outgoing second beam; the difference in the angular spread between the center and the edge of the spot of the second beam is less than the difference in the angular spread between the center and the edge of the spot of the first beam.

13. The holographic projection system according to claim 12, wherein, The holographic element has a preset diffraction angle; The projection beam has a target diffusion angle at a target edge position of the holographic element; The difference between the target diffusion angle and the preset diffraction angle is less than a preset difference threshold.

14. The holographic projection system according to claim 12, wherein, The beam adjustment element is located on the beam incident surface of the diffusion element; And / or, the beam adjustment element is located on the beam outgoing surface of the diffusion element.

15. The holographic projection system according to claim 12, further comprising: A reflection element located in the optical path between the image source and the diffusion element, for reflecting the projection beam; The reflected projection beam is incident on the diffusion element; Wherein, the beam adjustment element is located in the optical path between the image source and the reflection element, and / or the beam adjustment element is located in the optical path between the reflection element and the diffusion element.

16. The holographic projection system according to claim 12, wherein, The beam adjustment element includes a first Fresnel lens, and the holographic element includes a second Fresnel lens; The focal length of the second Fresnel lens is greater than the focal length of the first Fresnel lens.

17. The holographic projection system according to claim 16, wherein, The first Fresnel lens has a micro-structure with a circular ring distribution or a semi-circular ring distribution, for converging the projection beam, and the converging ability at the edge is higher than that at the center.

18. The holographic projection system according to claim 16, wherein, The second Fresnel lens includes a holographic film or a grating.

19. The holographic projection system according to claim 16, wherein, The focal length of the first Fresnel lens is 80 mm to 150 mm; The focal length of the second Fresnel lens is 250 mm to 450 mm.

20. The holographic projection system according to claim 12, wherein, The image source has a lens structure, and the optical axes of the lens structure, the beam adjustment element, and the holographic element are all coaxial; The center of the image carried by the projection beam is in the central region of the beam adjustment element and in the central region of the holographic element.

21. The holographic projection system according to claim 12, wherein, The image source has a lens structure, and the optical axes of the lens structure, the beam adjustment element, and the holographic element are all coaxial; The center of the image carried by the projection beam is located on one side of the optical axis.

Images