Holographic lens element with large field of view and large virtual image distance and manufacturing device thereof

Abstract

The utility model belongs to the technical field of display, and discloses a holographic lens element with a large field of view and a large virtual image distance and a manufacturing device thereof. The holographic lens element generates second light propagating in the direction of the signal light when and only when irradiated by first light propagating in the direction of the reference light from the field of view, the field of view, the first light and the second light are all located on one side of the holographic lens element, and the reverse extension line of the second light is converged to form a virtual image on the other side of the holographic lens element. Particularly, the field of view and the virtual image are both divided into a plurality of areas, the holographic lens element comprises a plurality of gratings, the ith grating generates second light when irradiated by first light from the ith area of the field of view and only when irradiated by first light from the ith area of the field of view, and reverse extension lines of the second light converge to form the ith area of the virtual image, the aberration of each region of the virtual image is within a naked eye acceptable range. According to the scheme, mutual crosstalk of different areas is avoided, aberration is improved, and the key point is that the view field and the virtual image distance can be made larger.

Description

Technical Field

[0001] This solution belongs to the field of display technology, specifically involving a holographic lens element with a large field of view and a large virtual image distance, and its fabrication device. Background Technology

[0002] Holographic lenses, as optical elements based on the wavefront reconstruction principle, exhibit unique technological potential in near-field displays, augmented reality, and 3D imaging due to their fabrication and imaging characteristics. Traditional holographic lenses record the phase information of the signal and reference light waves through interference, reconstructing the original wavefront during the reconstruction process to achieve optical imaging or beam manipulation. Specifically, in the fabrication optical path of a typical holographic lens, the signal and reference light illuminate the holographic photosensitive material from opposite sides. Their interference fringes are recorded within the holographic photosensitive material, forming microstructures with specific phase modulation, such as... Figure 1 During the imaging process, when the reconstructed reference light emitted from object A, propagating along the direction of the reference light, illuminates the holographic lens, the original signal light wavefront is partially reconstructed, generating a reconstructed signal light propagating along the direction of the signal light. The backward extensions of the reconstructed signal light converge to form a virtual image A', as shown below. Figure 2 .

[0003] However, due to the inherent limitations of the resolution of holographic recording media and the design characteristics of the optical path, existing holographic lens elements still face significant challenges in expanding the field of view and suppressing aberrations. Especially during virtual image generation, the image quality deteriorates sharply with increasing field of view and virtual image distance, becoming a key bottleneck restricting its practical application. Specifically, the imaging optical path can only achieve a clear image that strictly meets geometrical optical conditions in a specific region (near point O' through which the optical axis passes). As the observation point gradually deviates from point O', the phase error of wavefront reconstruction accumulates significantly, leading to a rapid increase in various aberrations (such as distortion and coma). The larger the field of view (i.e., the size of object A), the greater the aberrations of the virtual image points corresponding to the object points in its edge regions. Moreover, the larger the virtual image distance, the more difficult it is to correct aberrations. Utility Model Content

[0004] This solution aims to overcome at least one defect in the prior art and provide a holographic lens element with a large field of view and a large virtual image distance, as well as its fabrication apparatus, to solve the problem that the imaging quality deteriorates sharply as the field of view and virtual image distance increase.

[0005] To solve the above-mentioned technical problems, the following technical solution is adopted:

[0006] Firstly, a holographic lens element with a large field of view and a large virtual image distance is proposed. This holographic lens element generates a second ray propagating in the direction of the signal light only when illuminated by a first ray propagating in the direction of the reference light from the field of view. The field of view, the first ray, and the second ray are all located on one side of the holographic lens element, and the backward extensions of the second ray converge on the other side of the holographic lens element to form a virtual image. Specifically, both the field of view and the virtual image are divided into multiple regions. The holographic lens element includes multiple gratings. The i-th grating generates a second ray only when illuminated by a first ray from the i-th region of the field of view. The backward extensions of this second ray converge to form the i-th region of the virtual image, and the aberrations of each region of the virtual image are within the range acceptable to the naked eye.

[0007] The above scheme uses multiple gratings to image multiple regions of the field of view, and the resulting images are multiple regions of the virtual image. This ensures that both the field of view and the virtual image have the same number of imaging centers, and each position on the field of view and the virtual image is close to the nearest imaging center. Regardless of the distance between the field of view and the virtual image, the aberration of each region of the virtual image can be controlled within an acceptable range for the naked eye. The spot size of the image point on the human retina is less than 20 μm, and the distortion is less than 3%. Moreover, each grating only images the corresponding region of the field of view, avoiding crosstalk between virtual images formed by different regions of the field of view through the holographic lens element. This allows the holographic lens element to have the characteristics of a large field of view and a large virtual image distance while ensuring imaging quality.

[0008] The holographic lens element may also include a transparent substrate, on which multiple gratings are located. The transparent substrate can be a car window, shop window, etc., and the car window can be a windshield, side window, or rear window.

[0009] Secondly, a holographic lens element fabrication apparatus is proposed. This apparatus fabricates the aforementioned holographic lens element with a large field of view and large virtual image distance by interferometric exposure of a holographic photosensitive material layer. The apparatus includes a reference light generation mechanism and a signal light generation mechanism. The reference light generation mechanism is located on one side of the holographic photosensitive material layer and is used to generate multiple beams of reference light in multiple exposures. The signal light generation mechanism is located on the other side of the holographic photosensitive material layer and is used to generate multiple beams of signal light in multiple exposures, so as to perform multiple exposures of the holographic photosensitive material layer and form multiple gratings for the holographic lens element. During each exposure, the reference light generation mechanism generates only the i-th beam of reference light corresponding to the i-th region of the field of view, and the signal light generation mechanism generates only the i-th beam of signal light corresponding to the i-th region of the virtual image. Both the i-th reference beam and the i-th signal beam are emitted directly onto the holographic photosensitive material layer, where they interfere. The interference fringes are recorded by the holographic photosensitive material layer, forming the i-th grating.

[0010] The above scheme uses a reference light generating mechanism that generates only the i-th reference light corresponding to the i-th region of the field of view each time, and a signal light generating mechanism that generates only the i-th signal light corresponding to the i-th region of the virtual image each time, to conduct interference exposure on the holographic photosensitive material layer to fabricate each grating of the holographic lens element one by one. Each grating formed in this way only images the corresponding region of the field of view as the corresponding region of the virtual image, which avoids crosstalk between different regions and improves aberrations. The key is that the field of view and the virtual image distance can be made larger, so that the holographic lens element has the characteristics of a large field of view and a large virtual image distance while ensuring imaging quality.

[0011] The reference light generation mechanism can generate multiple reference beams in multiple stages using a first angle adjuster and a first lens group, with each stage generating only the i-th reference beam corresponding to the i-th region of the field of view. The first angle adjuster and the first lens group are used to modulate parallel light, which passes through them sequentially. During each exposure, the first angle adjuster adjusts the incident angle of the parallel light in the first lens group, causing the parallel light to be converged by the first lens group to the i-th region of the field of view, forming the i-th reference beam. The first angle adjuster can be a laser galvanometer or an acousto-optic modulator (AOM). The first lens group can include one, two, or more lenses.

[0012] The reference light generation mechanism can also generate multiple reference beams in multiple stages using a first diffusion element and a first spatial light modulator, with each generation generating only the i-th reference beam corresponding to the i-th region of the field of view. The first diffusion element and the first spatial light modulator modulate the beam, which passes sequentially through them. During each exposure, the first diffusion element modulates the beam into numerous point light sources located in multiple regions of the field of view. Under the modulation of the first spatial light modulator, only the point light source located in the i-th region of the field of view is allowed to emit, forming the i-th reference beam. In addition to the first diffusion element and the first spatial light modulator, the reference light generation mechanism can also include a third lens group for modulating the beam, with the beam passing sequentially through the first diffusion element, the third lens group, and the first spatial light modulator. During each exposure, the first diffusion element modulates the beam into numerous point light sources, and the third lens group converges these numerous point light sources to multiple regions of the field of view, allowing the point light sources to be more accurately focused to each region of the field of view, thereby improving the fabrication accuracy of the grating and further enhancing the imaging quality of the holographic lens element. The third lens group can include one, two, or more lenses.

[0013] The signal light generation mechanism can generate multiple signal beams in multiple stages using a second angle adjuster and a second lens group, with each generation generating only the i-th signal beam corresponding to the i-th region of the virtual image. The second angle adjuster and the second lens group are used to modulate parallel light, which passes sequentially through them. During each exposure, the second angle adjuster adjusts the incident angle of the parallel light in the second lens group, causing the parallel light to be converged by the second lens group to the i-th region of the virtual image, forming the i-th signal beam. The second angle adjuster can be a laser galvanometer or an acousto-optic modulator (AOM). The second lens group can include one, two, or more lenses.

[0014] The signal light generation mechanism can also generate multiple signal beams in multiple stages using a second diffusion element and a second spatial light modulator, with each generation generating only the i-th signal beam corresponding to the i-th region of the virtual image. The second diffusion element and the second spatial light modulator modulate the beam, which passes sequentially through both. During each exposure, the second diffusion element modulates the beam into numerous point light sources located in multiple regions of the virtual image. Under the modulation of the second spatial light modulator, only the point light source located in the i-th region of the virtual image is allowed to emit, forming the i-th signal beam. In addition to the second diffusion element and the second spatial light modulator, the signal light generation mechanism can also include a fourth lens group for modulating the beam. The beam passes sequentially through the second diffusion element, the fourth lens group, and the second spatial light modulator. During each exposure, the second diffusion element modulates the beam into numerous point light sources, and the fourth lens group converges these point light sources to multiple regions of the virtual image, allowing for more accurate convergence of the point light sources to each region of the virtual image, thereby improving the fabrication accuracy of the grating and further enhancing the imaging quality of the holographic lens element. The fourth lens group can include one, two, or more lenses.

[0015] Compared with existing technologies, this solution has the following advantages: This solution uses multiple gratings to image multiple regions of the field of view, and the resulting images are multiple regions of the virtual image. This ensures that both the field of view and the virtual image have the same number of imaging centers, and each position on the field of view and the virtual image is close to the nearest imaging center. No matter how large the distance between the field of view and the virtual image is, the aberration of each region of the virtual image can be controlled within an acceptable range for the naked eye. Moreover, each grating only images the corresponding region of the field of view, avoiding crosstalk between virtual images formed by different regions of the field of view through the holographic lens element. This allows the holographic lens element to have the characteristics of a large field of view and a large virtual image distance while ensuring imaging quality. Attached Figure Description

[0016] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this solution. To better illustrate the solution, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0017] Figure 1 This is a schematic diagram of the optical path for fabricating a traditional holographic lens element.

[0018] Figure 2 This is a schematic diagram of the imaging optical path of a traditional holographic lens element.

[0019] Figure 3 This is a schematic diagram of the structure and imaging optical path of a holographic lens element with a large field of view and a large virtual image distance.

[0020] Figure 4 This is a schematic diagram of the structure and optical path for fabricating HOE1 in Embodiment 1 of the holographic lens element fabrication device.

[0021] Figure 5 This is a schematic diagram of the structure and optical path for fabricating HOE2 in Embodiment 1 of the holographic lens element fabrication device.

[0022] Figure 6 This is a schematic diagram of the structure and fabrication optical path of the HOE1 in Embodiment 2 (transmission type) of the holographic lens element fabrication device.

[0023] Figure 7 This is a schematic diagram of the structure and fabrication optical path of the HOE2 in Embodiment 2 (transmission type) of the holographic lens element fabrication device.

[0024] Figure 8 This is a schematic diagram of the structure and optical path of Embodiment 2 (reflective type) of the holographic lens element fabrication device.

[0025] Explanation of reference numerals in the attached drawings: holographic lens element 100, holographic photosensitive material layer 110, transparent substrate 120, reference light generating mechanism 200, first angle adjuster 211, first lens group 212, first diffuser element 221, first spatial light modulator 222, third lens group 223, signal light generating mechanism 300, second angle adjuster 311, second lens group 312, second diffuser element 321, second spatial light modulator 322, fourth lens group 323, field of view B, virtual image B'. Detailed Implementation

[0026] To enable those skilled in the art to better understand this solution, the following detailed description is provided in conjunction with specific embodiments.

[0027] Figure 3A possible large field-of-view, large virtual image distance holographic lens element is illustrated. This holographic lens element 100 is at least configured with a holographic photosensitive material layer 110 formed of holographic photosensitive material, which generates a grating under interference exposure of signal light and reference light. The holographic lens element 100 (grating) generates a second ray propagating in the direction of the signal light if and only when illuminated by a first ray propagating in the direction of the reference light from the field of view B, wherein the field of view B, the first ray, and the second ray are all located on one side of the holographic lens element 100 (grating), and the backward extension of the second ray converges on the other side of the holographic lens element 100 (grating) to form a virtual image B'.

[0028] Specifically, the holographic lens element 100 includes multiple gratings, and both the field of view B and the virtual image B' are divided into multiple regions, with the number of regions matching the number of gratings. Each grating generates a second ray only when illuminated by a first ray from a corresponding region of the field of view B, which then converges to form the corresponding region of the virtual image B'. Specifically, the i-th grating generates a second ray if and only when illuminated by a first ray from the i-th region of the field of view B, and the backward extension of this second ray converges to form the i-th region of the virtual image B'. Therefore, both the field of view B and the virtual image B' have the same number of imaging centers. Each position on the field of view B and the virtual image B' is close to the nearest imaging center. No matter how large the distance between the field of view B and the virtual image B' is, the aberration of each region of the virtual image B' can be controlled within the range acceptable to the naked eye. The size of the dot on the human retina is less than 20 μm, and the distortion is less than 3%. Moreover, each grating of the holographic lens element 100 only images the corresponding region of the field of view B. For example, the first grating HOE1 of the holographic lens element 100 only images the first region R1 of the field of view B as the first region R1' of the virtual image B', and the second grating HOE2 of the holographic lens element 100 only images the second region R2 of the field of view B as the second region R2' of the virtual image B'. This avoids crosstalk between the virtual images B' formed by different regions of the field of view B through the holographic lens element 100, thus enabling the holographic lens element 100 to have the characteristics of a large field of view B and a large distance between virtual images B' while ensuring imaging quality.

[0029] The holographic lens element 100 can also be configured with a transparent substrate 120, on which a holographic photosensitive material layer 110, i.e., multiple gratings, is formed. In specific applications, the transparent substrate 120 can be a car window, shop window, etc., where the car window includes, but is not limited to, windshields, side windows, and rear windows. In projection-type head-up display devices, the windshield can be directly used as the transparent substrate 120 to provide the driver with real-time updated driving information. In addition, the transparent substrate 120 can also be a transparent film with adhesive properties on the back, and the formed volume holographic optical diffusion element can be attached to the display surface of projection screen products such as car windows and shop windows.

[0030] Figures 4-8The diagram illustrates a possible apparatus for fabricating a holographic lens element, which fabricates the aforementioned holographic lens element 100 with a large field of view and large virtual image distance by interferoscopic exposure of a holographic photosensitive material layer 110. For example... Figures 4-8 As shown, the device is equipped with a reference light generation mechanism 200 and a signal light generation mechanism 300. The reference light generation mechanism 200 is located on one side of the holographic photosensitive material layer 110 and is used to generate multiple reference beams in multiple stages. The signal light generation mechanism 300 is located on the other side of the holographic photosensitive material layer 110 and is used to generate multiple signal beams in multiple stages, so as to expose the holographic photosensitive material layer 110 multiple times and form multiple gratings of the holographic lens element 100. During each exposure, the reference light generation mechanism 200 generates only the i-th reference beam corresponding to the i-th region of the field of view B, and the signal light generation mechanism 300 generates only the i-th signal beam corresponding to the i-th region of the virtual image B'. Both the i-th reference beam and the i-th signal beam are emitted directly onto the holographic photosensitive material layer 110, and they interfere on the holographic photosensitive material layer 110. Their interference fringes are recorded by the holographic photosensitive material layer 110 to form the i-th grating. For example, when exposing the first grating HOE1 of the holographic lens element 100, the reference light generation mechanism 200 only generates the first beam of reference light corresponding to the first region R1 of the field of view B, and the signal light generation mechanism 300 only generates the first beam of signal light corresponding to the first region R1' of the virtual image B'. Figure 4 , Figure 6 and Figure 8 As shown; when exposing and fabricating the second grating HOE2 of the holographic lens element 100, the reference light generation mechanism 200 only generates the second beam of reference light corresponding to the second region R2 of the field of view B, and the signal light generation mechanism 300 only generates the second beam of signal light corresponding to the first region R2' of the virtual image B', as shown. Figure 5 and Figure 7 As shown; and so on, until the exposure fabrication of all gratings of the holographic lens element 100 is completed.

[0031] The reference light generating mechanism 200 and the signal light generating mechanism 300 can share a single light source, which is split into two beams by a beam splitter, and emitted as reference light and signal light respectively through the reference light generating mechanism 200 and the signal light generating mechanism 300. Alternatively, they can each be equipped with independent light sources, namely a reference light source and a signal light source. In addition to the light source (not shown), the reference light generating mechanism 200 can be equipped with a first angle adjuster 211 and a first lens group 212, or a first diffuser element 221 and a first spatial light modulator 222. Similarly, in addition to the light source, the signal light generating mechanism 300 can be equipped with a second angle adjuster 311 and a second lens group 312, or a second diffuser element 321 and a second spatial light modulator 322.

[0032] For the reference light generating mechanism 200 configured with a first angle adjuster 211 and a first lens group 212, the light source needs to be emitted as parallel light, which sequentially passes through the first angle adjuster 211 and the first lens group 212, such as... Figures 4-5 As shown. Both the first angle adjuster 211 and the first lens group 212 are used to modulate parallel light. The first angle adjuster 211 adjusts the incident angle of the parallel light on the first lens group 212, and the first lens group 212 converges the parallel light. After adjustment by the first angle adjuster 211, the parallel light can be converged by the first lens group 212 to different regions of the field of view B, and then diverged from different regions of the field of view B to the holographic photosensitive material layer 110. During each exposure, the first angle adjuster 211 adjusts the incident angle of the parallel light on the first lens group 212, so that the parallel light is converged by the first lens group 212 to the i-th region of the field of view B, forming the i-th reference beam. For example, when exposing to fabricate the first grating HOE1 of the holographic lens element 100, the first angle adjuster 211 adjusts the incident angle of the parallel light on the first lens group 212, so that the parallel light is converged by the first lens group 212 to the first region R1 of the field of view B, forming the first reference beam, as... Figure 4 As shown; when exposing and fabricating the second grating HOE2 of the holographic lens element 100, the first angle adjuster 211 adjusts the incident angle of the parallel light on the first lens group 212, so that the parallel light is converged by the first lens group 212 to the second region R2 of the field of view B, forming a second reference beam, as shown. Figure 5 As shown.

[0033] For the signal light generating mechanism 300 configured with a second angle adjuster 311 and a second lens group 312, the light source needs to be emitted as parallel light, which sequentially passes through the second angle adjuster 311 and the second lens group 312, such as... Figures 4-5 As shown. Both the second angle adjuster 311 and the second lens group 312 are used to modulate parallel light. The second angle adjuster 311 adjusts the incident angle of the parallel light in the second lens group 312, and the second lens group 312 converges the parallel light. After adjustment by the second angle adjuster 311, the parallel light can be converged by the second lens group 312 to different regions of the virtual image B', and then diverges from different regions of the virtual image B' to the holographic photosensitive material layer 110. During each exposure, the second angle adjuster 311 adjusts the incident angle of the parallel light in the second lens group 312, so that the parallel light is converged by the second lens group 312 to the i-th region of the virtual image B', forming the i-th signal light. For example, when exposing to fabricate the first grating HOE1 of the holographic lens element 100, the second angle adjuster 311 adjusts the incident angle of the parallel light in the second lens group 312, so that the parallel light is converged by the second lens group 312 to the first region R1' of the virtual image B', forming the first signal light, as... Figure 4As shown; when exposing and fabricating the second grating HOE2 of the holographic lens element 100, the second angle adjuster 311 adjusts the incident angle of the parallel light on the second lens group 312, so that the parallel light is converged by the second lens group 312 to the second region R2' of the virtual image B', forming the second beam of signal light, as shown. Figure 5 As shown.

[0034] Both the first angle adjuster 211 and the second angle adjuster 311 can be laser galvanometers or acousto-optic modulators (AOMs). The laser galvanometer consists of an XY optical scanning head, an electronic drive amplifier, and optical reflecting mirrors. Signals from the computer controller drive the optical scanning head through a drive amplifier circuit, thereby controlling the deflection of the laser beam in the XY plane and adjusting the incident angle of the parallel light. The acousto-optic modulator (AOM), based on the Bragg grating principle, can obtain first-order diffracted light with high diffraction efficiency. By controlling the period of the Bragg grating, the angle of the diffracted light can be controlled, achieving angle deflection and thus adjusting the incident angle of the parallel light. Both the first lens group 212 and the second lens group 312 can be configured with one, two, or more lenses.

[0035] For the scheme of configuring the reference light generating mechanism 200 with the first diffusion element 221 and the first spatial light modulator 222, the light source can be emitted as parallel light or as divergent light. The light beam emitted by the light source passes through the first diffusion element 221 and the first spatial light modulator 222 in sequence, such as... Figures 6-7 As shown. Both the first diffusion element 221 and the first spatial light modulator 222 are used to modulate the light beam. The first diffusion element 221 modulates the light beam into numerous point light sources, which cover the entire field of view B. The first spatial light modulator 222 regulates the beam to allow the point light sources in a specific area of ​​field of view B to emit while rejecting the emission of other point light sources. Through the synergistic effect of the first diffusion element 221 and the first spatial light modulator 222, the light beam can diverge from different areas of field of view B to the holographic photosensitive material layer 110. During each exposure, the first diffusion element 221 modulates the light beam into numerous point light sources located in multiple areas of field of view B. Under the modulation of the first spatial light modulator 222, only the point light source located in the i-th area of ​​field of view B is allowed to emit, forming the i-th reference beam. For example, when the first grating HOE1 of the holographic lens element 100 is exposed, the first diffusion element 221 modulates the light beam into countless point light sources located in multiple regions of the field of view B. Under the modulation of the first spatial light modulator 222, only the point light sources located in the first region R1 of the field of view B are allowed to emit, forming the first reference beam, such as... Figure 6As shown; when the second grating HOE2 of the holographic lens element 100 is fabricated by exposure, the first diffusion element 221 modulates the light beam into countless point light sources located in multiple regions of the field of view B. Under the modulation of the first spatial light modulator 222, only the point light source located in the second region R2 of the field of view B is allowed to emit, forming the second reference beam, as shown. Figure 7 As shown. The first diffusion element 221 can be frosted glass or other elements with light diffusion characteristics. The first spatial light modulator 222 can be a transmissive spatial light modulator or a reflective spatial light modulator.

[0036] The reference light generating mechanism 200 is configured with a first diffusion element 221 and a first spatial light modulator 222, especially with the first spatial light modulator 222 employing a reflective spatial light modulator scheme. The reference light generating mechanism 200 can also be configured with a third lens group 223, through which the light beam sequentially passes. Figure 8 As shown. The third lens group 223 is used to modulate the light beam, specifically to converge the light beam modulated by the first diffuser element 221, so that the numerous point light sources modulated by the first diffuser element 221 can be more accurately converged to various regions of the field of view B, thereby improving the fabrication accuracy of the grating and further improving the imaging quality of the holographic lens element 100. During each exposure, the first diffuser element 221 modulates the light beam into numerous point light sources, and the third lens group 223 converges these numerous point light sources to multiple regions of the field of view B. The first spatial light modulator 222 only allows the point light source located in the i-th region of the field of view B to emit, forming the i-th reference beam. The third lens group 223 can be configured with one, two, or more lenses.

[0037] For the signal light generating mechanism 300 configured with a second diffuser 321 and a second spatial light modulator 322, the light source can be emitted as parallel light or as divergent light. The light beam emitted by the light source passes sequentially through the second diffuser 321 and the second spatial light modulator 322, such as... Figures 6-7As shown. Both the second diffuser element 321 and the second spatial light modulator 322 are used to modulate the light beam. The second diffuser element 321 modulates the light beam into numerous point light sources, which cover all areas of the virtual image B'. The second spatial light modulator 322 regulates the beam to allow the point light sources corresponding to a certain area of ​​the virtual image B' to emit while rejecting the emission of other point light sources. Through the synergistic effect of the second diffuser element 321 and the second spatial light modulator 322, the light beam can diverge from different areas of the virtual image B' to the holographic photosensitive material layer 110. During each exposure, the second diffuser element 321 modulates the light beam into numerous point light sources located in multiple areas of the virtual image B'. Under the modulation of the second spatial light modulator 322, only the point light source located in the i-th area of ​​the virtual image B' is allowed to emit, forming the i-th signal beam. For example, when the first grating HOE1 of the holographic lens element 100 is exposed, the second diffusion element 321 modulates the light beam into countless point light sources located in multiple regions of the virtual image B'. Under the modulation of the second spatial light modulator 322, only the point light sources located in the first region R1' of the virtual image B' are allowed to emit, forming the first signal light, such as... Figure 6 As shown; when the second grating HOE2 of the holographic lens element 100 is exposed, the second diffusion element 321 modulates the light beam into countless point light sources located in multiple regions of the virtual image B'. Under the modulation of the second spatial light modulator 322, only the point light sources located in the second region R2' of the virtual image B' are allowed to emit, forming the second signal light, as shown. Figure 7 As shown. The second diffusion element 321 can be frosted glass or other elements with light diffusion characteristics. The second spatial light modulator 322 can be a transmissive spatial light modulator or a reflective spatial light modulator.

[0038] The signal light generating mechanism 300 is configured with a second diffuser 321 and a second spatial light modulator 322, especially the second spatial light modulator 322 which is a reflective spatial light modulator. The signal light generating mechanism 300 can also be configured with a fourth lens group 323, through which the light beam sequentially passes. Figure 8 As shown. The fourth lens group 323 is used to modulate the light beam, specifically to converge the light beam modulated by the second diffuser element 321, so that the numerous point light sources modulated by the second diffuser element 321 can be more accurately converged to various regions of the virtual image B', thereby improving the fabrication accuracy of the grating and further improving the imaging quality of the holographic lens element 100. During each exposure, the second diffuser element 321 modulates the light beam into numerous point light sources, and the fourth lens group 323 converges these numerous point light sources to multiple regions of the virtual image B'. The second spatial light modulator 322 only allows the point light source located in the i-th region of the virtual image B' to emit, forming the i-th signal light beam. The fourth lens group 323 can be configured with one, two, or more lenses.

[0039] Obviously, the above embodiments of this solution are merely examples for clearly illustrating this solution, and are not intended to limit the implementation of this solution. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this solution should be included within the scope of protection of the claims of this solution.

Claims

1. A holographic lens element with a large field of view and a large virtual image distance, wherein the holographic lens element generates a second ray propagating in the direction of a signal light when illuminated only by a first ray propagating in the direction of a reference light from the field of view, wherein the field of view, the first ray, and the second ray are all located on one side of the holographic lens element, and the backward extension of the second ray converges to form a virtual image on the other side of the holographic lens element, characterized in that, Both the field of view and the virtual image are divided into multiple regions. The holographic lens element includes multiple gratings. The i-th grating generates a second ray when it is illuminated by a first ray from the i-th region of the field of view. The backward extension of the second ray converges to form the i-th region of the virtual image. The aberration of each region of the virtual image is within the range acceptable to the naked eye.

2. The holographic lens element with a large field of view and large virtual image distance according to claim 1, characterized in that, The holographic lens element also includes a transparent substrate, on which a plurality of the gratings are located.

3. The holographic lens element with a large field of view and a large virtual image distance according to claim 2, characterized in that, The transparent substrate is a car window or shop window, and the car window is a windshield, side window or rear window.

4. A holographic lens element fabrication apparatus, wherein the apparatus fabricates a holographic lens element with a large field of view and a large virtual image distance as described in any one of claims 1 to 3 by interferoscopic exposure of a holographic photosensitive material layer, characterized in that, The device includes a reference light generation mechanism and a signal light generation mechanism. The reference light generation mechanism is located on one side of the holographic photosensitive material layer and is used to generate multiple reference beams in multiple stages. The signal light generation mechanism is located on the other side of the holographic photosensitive material layer and is used to generate multiple signal beams in multiple stages, so as to expose the holographic photosensitive material layer multiple times and form multiple gratings of the holographic lens element. During each exposure, the reference light generation mechanism generates only the i-th reference beam corresponding to the i-th region of the field of view, and the signal light generation mechanism generates only the i-th signal beam corresponding to the i-th region of the virtual image. Both the i-th reference beam and the i-th signal beam are emitted directly onto the holographic photosensitive material layer, where they interfere with each other. The interference fringes are recorded by the holographic photosensitive material layer to form the i-th grating.

5. The holographic lens element fabrication apparatus according to claim 4, characterized in that, The reference light generation mechanism includes a first angle adjuster and a first lens group for modulating parallel light. The parallel light passes through the first angle adjuster and the first lens group in sequence. During each exposure, the first angle adjuster adjusts the incident angle of the parallel light in the first lens group, so that the parallel light is converged by the first lens group to the i-th region of the field of view to form the i-th reference light. The first angle adjuster is a laser galvanometer or an acousto-optic modulator. The first lens group includes one, two, or more lenses.

6. The holographic lens element fabrication apparatus according to claim 4, characterized in that, The reference light generation mechanism includes a first diffusion element and a first spatial light modulator for modulating the light beam. The light beam passes through the first diffusion element and the first spatial light modulator in sequence. During each exposure, the first diffusion element modulates the light beam into numerous point light sources located in multiple regions of the field of view. Under the modulation of the first spatial light modulator, only the point light source located in the i-th region of the field of view is allowed to emit, forming the i-th reference light beam.

7. The holographic lens element fabrication apparatus according to claim 6, characterized in that, The reference light generating mechanism further includes a third lens group for modulating the light beam, which passes sequentially through the first diffusion element, the third lens group, and the first spatial light modulator. During each exposure, the first diffusion element modulates the light beam into numerous point light sources, and the third lens group converges these numerous point light sources into multiple regions of the field of view. The third lens group includes one, two, or more lenses.

8. The apparatus for fabricating a holographic lens element according to any one of claims 4 to 7, characterized in that, The signal light generation mechanism includes a second angle adjuster and a second lens group for modulating parallel light. The parallel light passes through the second angle adjuster and the second lens group in sequence. During each exposure, the second angle adjuster adjusts the incident angle of the parallel light in the second lens group, so that the parallel light is converged by the second lens group to the i-th region of the virtual image to form the i-th signal light. The second angle adjuster is a laser galvanometer or an acousto-optic modulator. The second lens group includes one, two, or more lenses.

9. The apparatus for fabricating a holographic lens element according to any one of claims 4 to 7, characterized in that, The signal light generation mechanism includes a second diffusion element and a second spatial light modulator for modulating the light beam. The light beam passes through the second diffusion element and the second spatial light modulator in sequence. During each exposure, the second diffusion element modulates the light beam into countless point light sources located in multiple regions of the virtual image. Under the modulation of the second spatial light modulator, only the point light source located in the i-th region of the virtual image is allowed to emit, forming the i-th signal light beam.

10. The holographic lens element fabrication apparatus according to claim 9, characterized in that, The signal light generation mechanism further includes a fourth lens group for modulating the light beam, which passes sequentially through the second diffusion element, the fourth lens group, and the second spatial light modulator. During each exposure, the second diffusion element modulates the light beam into numerous point light sources, and the fourth lens group converges these numerous point light sources into multiple regions of the virtual image. The fourth lens group includes one, two, or more lenses.

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