Optical system and method for suspended imaging

Abstract

The present invention provides an optical system for suspended imaging, characterized in that it includes: a light source configured to emit a divergent light beam; a shaping lens located downstream of the light path of the light source, configured to receive the light beam emitted by the light source and emit it after adjustment; a diffractive optical element located downstream of the light path of the shaping lens, configured to receive the emitted light beam and project a suspended light field with a specific pattern at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern unit is configured to modulate the incident light to project the light field with the specific pattern. The present invention also provides a method for suspended imaging. An embodiment of the present invention proposes a solution for realizing suspended imaging in the air. A real suspended image is formed at a specific position in the air by illuminating a diffractive optical element designed for collimated light with a divergent light source.

Description

Technical Field

[0001] The present invention generally relates to the field of optical technology, and more particularly to an optical system for suspended imaging and a method for suspended imaging. Background Art

[0002] In daily life, industrial production, and scientific research, suspended imaging is a new type of display method. The emergence of this technology has brought many possibilities for creative applications in various fields. In the advertising industry, it can replace traditional advertising boards and attract more people's attention. At industrial work sites, this suspended imaging display method allows workers to perform various safe operations while wearing gloves. In the automotive field, various data information of the car can be presented in front of the human eye, bringing a safer driving experience. In addition to these aspects, suspended imaging technology can also bring convenience to various fields such as entertainment, security, and medical care. The demand for 3D fingerprint or palm print recognition in the air is increasing. The light field can indicate the hovering position of a person's fingerprint or palm through 3D suspended imaging.

[0003] The contents of the background technology section are merely the technologies known to the public and do not necessarily represent the existing technologies in the field. Summary of the invention

[0004] In view of at least one defect of the prior art, the present invention provides an optical system for suspended imaging, comprising: a light source, configured to emit a divergent light beam; a shaping lens, located downstream of the light path of the light source, configured to receive the light beam emitted by the light source and emit it after adjustment; a diffractive optical element, located downstream of the light path of the shaping lens, configured to receive the emitted light beam and project a suspended light field with a specific pattern at a preset position in space, wherein the diffractive optical element comprises a microstructure surface, one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to modulate the incident light to project the light field with the specific pattern.

[0005] According to one aspect of the present invention, the light source is a point light source, and the point light source is arranged at a position far away from the focal plane of the shaping lens along the light propagation direction.

[0006] According to one aspect of the present invention, the distance between the point light source and the focal plane of the shaping lens is adjusted so that the optical system projects the light field with the specific pattern at the preset position.

[0007] According to one aspect of the present invention, the point light source includes one or more of a semiconductor laser and a light emitting diode.

[0008] According to one aspect of the present invention, the shaping lens includes one or more of a collimator lens and a Fresnel lens.

[0009] According to one aspect of the present invention, the diffractive optical element is designed using parallel light as a light source and the light field having a specific pattern as a target light field.

[0010] According to one aspect of the present invention, the specific pattern includes one or more of a palm print and a fingerprint.

[0011] According to one aspect of the present invention, the specific pattern includes one or more of a stereogram and a plan view.

[0012] According to one aspect of the present invention, the optical system further comprises:

[0013] The grating unit is located downstream of the optical path of the diffractive optical element and is configured to replicate the light field with a specific pattern at the preset position in space.

[0014] According to one aspect of the present invention, the grating unit includes a two-dimensional grating configured to expand the light field having the specific pattern at the preset position in space in an array form.

[0015] The present invention also provides a suspension imaging method, comprising:

[0016] A divergent light beam is emitted by a light source;

[0017] The light beam emitted by the light source is received by a shaping lens, and then adjusted and emitted;

[0018] The outgoing light beam is received by a diffractive optical element, and a light field with a specific pattern is projected at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to modulate the incident light to project the light field with the specific pattern.

[0019] According to one aspect of the present invention, the method further comprises:

[0020] The distance between the light source and the focal plane of the shaping lens is adjusted so that the optical system projects the light field with the specific pattern at the preset position.

[0021] According to one aspect of the present invention, the method further comprises:

[0022] The light field with the specific pattern is replicated at the preset position through the grating unit.

[0023] According to one aspect of the present invention, the grating unit includes a two-dimensional grating, and the method further includes: expanding the light field with the specific pattern in the form of an array at the preset position through the two-dimensional grating.

[0024] The present invention also provides an optical system for suspended imaging, comprising:

[0025] a light source configured to emit a divergent light beam; and

[0026] A diffractive optical element is located downstream of the optical path of the light source, configured to receive and shape the light beam emitted by the light source, and project a suspended light field with a specific pattern at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to shape and modulate the incident light to project the light field with the specific pattern.

[0027] According to one aspect of the present invention, the optical system further comprises:

[0028] The grating unit is located downstream of the optical path of the diffractive optical element and is configured to replicate the light field with a specific pattern at the preset position in space.

[0029] According to one aspect of the present invention, the grating unit includes a two-dimensional grating configured to expand the light field having the specific pattern at the preset position in space in an array form.

[0030] The present invention also provides a suspension imaging method, comprising:

[0031] A divergent light beam is emitted by a light source;

[0032] The outgoing light beam is received by a diffractive optical element, shaped and modulated, and a light field with a specific pattern is projected at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to shape and modulate the incident light to project the light field with the specific pattern.

[0033] According to one aspect of the present invention, the method further comprises:

[0034] The light field with a specific pattern is expanded in the form of an array at the preset position through a two-dimensional grating. An embodiment of the present invention proposes a solution for realizing suspended imaging in the air. A real suspended image is formed at a specific position in the air by illuminating a diffractive optical element (DOE) designed with collimated light with a divergent light source. A diffractive optical element designed based on collimated light will form an image at infinity. After adding a divergent light source (LD or monochromatic LED) and a collimating lens (or Fresnel lens) before the diffractive optical element, the distance from the light source to the collimating lens is adjusted according to the object-image relationship of the lens in geometric optics, so that imaging can be achieved at a specific position in the air. The larger the physical size of the DOE, the larger the visual angle range (FOV) of the human eye observing the suspended image. Generally, the size of the DOE is limited by the size of the device structure. In order to further increase the visual angle range (FOV) of the suspended image, a grating can be added after the DOE for array expansion of the suspended image, so that the human eye can see the suspended image in a larger FOV range, and the visual effect is better. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0036] Figure 1 An optical system for suspended imaging according to an embodiment of the present invention is shown;

[0037] Figure 2 Shows Figure 1 A schematic diagram of optical path parameters of an embodiment;

[0038] Figure 3 An optical system for suspended imaging according to another embodiment of the present invention is shown;

[0039] Figure 4 A method for suspended imaging according to an embodiment of the present invention is shown; and

[0040] Figure 5 An optical system for suspended imaging according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0041] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0045] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0046] The embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0047] Figure 1 The optical system 100 for suspended imaging according to the first embodiment of the present invention is shown below. Figure 1 Detailed description.

[0048] like Figure 1 As shown, the optical system 100 includes a light source 101, a shaping lens 102, and a diffractive optical element 103, wherein the light source 101 is configured to emit a divergent light beam B1, as shown in FIG. Figure 1 As shown, the divergent light beam B1 has a relatively obvious divergence angle. The shaping lens 102 is located downstream of the light path of the light source 101, receives the divergent light beam B1 emitted by the light source, and adjusts the outgoing light beam B2. The shaping lens 102 is preferably a collimator (such as a convex lens) or a Fresnel lens, which is used to converge the divergent light beam from the light source 101 and then make it incident on the diffractive optical element 103 downstream of the light path. The diffractive optical element 103 receives the outgoing light beam B2 from the shaping lens 102, and projects a suspended light field P with a specific pattern at a preset position in space. Figure 1 In the example, the light field has a palm-shaped pattern, and other patterns may also be projected, such as palm prints, fingerprints, arrows, fingers, etc., which are all within the protection scope of the present invention.

[0049] The diffractive optical element 103 includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, which are used to modulate the light beam incident thereon, for example, to modulate the phase, so as to project a light field with a specific pattern. When designing and manufacturing the diffractive optical element 103, the phase distribution of the microstructure pattern unit can be calculated according to the parameters of the light beam incident on the diffractive optical element 103 (such as parallel light or divergent light, wavelength and other parameters) and the parameters of the target light field (such as the position of the target light field, the pattern of the target light field, etc.). After the phase distribution of the microstructure pattern unit is obtained, it can be used to manufacture the diffractive optical element 103. According to a preferred embodiment of the present invention, the diffractive optical element 103 is designed with parallel light as the incident light field and the light field P with a specific pattern as the target light field.

[0050] In addition, in the present invention, the pattern projected by the optical system 100 is not limited to a two-dimensional plane pattern, but can also be a three-dimensional stereoscopic pattern. Different projection patterns can be achieved through the specific design of the diffractive optical element 103, which will not be described in detail here.

[0051] The optical system 100 according to an embodiment of the present invention is described above, in which the diffractive optical element 103 is used to project a suspended pattern at a preset position in space.

[0052] According to one embodiment of the present invention, the light source 101 is, for example, a point light source, including but not limited to one or more of a semiconductor laser and a light emitting diode. The point light source is arranged at a position away from the focal plane of the shaping lens 102 along the optical axis direction, that is, the distance from the shaping lens 102 is greater than the focal length of the shaping lens 102.

[0053] In addition, by adjusting the distance between the light source 101 and the focal plane of the shaping lens 102, the optical system 100 can be adjusted to project the light field with the specific pattern at the preset position, or the size and / or clarity of the specific pattern can be adjusted.

[0054] Figure 1 In the embodiment, a laser or a light emitting diode can be selected as the light source according to the actual imaging effect. After the light source is selected, the distance S1 between the light source 101 and the diffractive optical element 103 can be determined, and the distance S1 is preferably between 10 cm and 15 cm. By using the active light source projection method, after the light beam emitted by the laser or the light emitting diode passes through the shaping lens 102 and the diffractive optical element 103, for example, a suspended pattern can be formed at a distance S2 of 15 cm from the diffractive optical element 103.

[0055] Figure 2 Shows Figure 1 Schematic diagram of the optical path parameters of the embodiment. Figure 2 As shown, the light source 101 is located outside the focal plane F of the shaping lens 102, for example, on the optical axis of the shaping lens 102. After passing through the shaping lens 102, the light beam emitted from the light source 101 is converged and incident on the diffractive optical element 103, and a light field P with a specific pattern is projected on the image plane IP. Figure 2 In the figure, a square wireframe (with the upper and lower edges defined by A and B respectively) represents the range of the suspended image projected by the diffractive optical element 103, and each point on the suspended image is obtained through the contribution of the entire area of ​​the diffractive optical element 103. In the vertical direction of the figure, the size of the diffractive optical element 103 is D, the size of the projected pattern is d, the distance between the diffractive optical element 103 and the image plane IP is L1, and the distance between the image plane IP and the observer's eyes is L2. For the suspended image represented by the square wireframe, the observer's field of view FOV θ is shown in the figure, which is the angle formed by the line connecting the upper and lower edges of the diffractive optical element 103 and the center of the suspended image. Therefore, the larger the value of D / L1, the larger the observer's field of view FOV θ. In addition, as Figure 2 As shown, the observer's eyes can only observe the complete single-cycle indication image within the Ω region.

[0056] The larger the size D of the diffractive optical element 103 is, the better. However, for the human eye to observe a complete single-period image, the following conditions must be met at the same time:

[0057] 1. D / d > ((L1+L2) / L2)

[0058] 2. To meet the requirement of FOV θ, D > 2 * tan(θ / 2)° * L1. For example, to meet the requirement of FOV5°, D > 2 * tan2.5° * 150mm = 13.1mm

[0059] The larger the value of D is, the more cycles of the indication image that can be observed by the human eye. If you want to see a 3x3 array indication pattern, D can be increased by 3 times while keeping d unchanged.

[0060] According to one embodiment of the present invention, D=40 mm, d=9.5 mm.

[0061] In the above embodiment, the size D of the diffractive optical element 103 needs to be set larger to ensure that the human eye can observe a complete single-period image, which may also bring certain difficulties to the design and manufacture of the diffractive optical element 103, because the larger the size of the diffractive optical element 103, the more difficult it is to manufacture. In addition, the size of the diffractive optical element will be limited by the size of the device structure.

[0062] In view of the above problem, according to a preferred embodiment of the present invention, a grating unit may be provided for the optical system, located downstream of the optical path of the diffractive optical element, and configured to replicate the light field having a specific pattern at the preset position in space. Figure 3 The optical path structure of such an embodiment is shown below. Figure 3 Detailed description.

[0063] Figure 3 2 shows an optical system 200 according to another embodiment of the present invention, which includes a light source 201, a shaping lens 202 and a diffractive optical element 203, respectively. Figure 1 The light source 101, shaping lens 102 and diffractive optical element 103 in the optical system 100 are basically the same, wherein the light source 201 is configured to emit a divergent light beam, and the shaping lens 202 is located downstream of the light path of the light source 201, receives the light beam emitted by the light source, and emits it after adjustment. The diffractive optical element 203 receives the outgoing light beam from the shaping lens 202, and projects a suspended light field P with a specific pattern at a preset position in space. Figure 3 As shown, the optical system 200 further includes a grating unit 204, which is located downstream of the optical path of the diffractive optical element 203 and is configured to replicate the light field with a specific pattern, for example, at the image plane IP, so that a plurality of repeated specific patterns can be projected. The grating unit is preferably a two-dimensional grating, which is configured to expand the light field with a specific pattern in the form of an array at the preset position in space, such as Figure 3 As shown in FIG. 1 , the grating unit 204 expands the pattern P into a 3*3 array.

[0064] exist Figure 3 In the embodiment, the diffractive optical element 203 is used to generate a single pattern P (palm print, or other indicative pattern) in the small box in the figure, and the diffractive optical element 203 can be directly designed based on the scalar GS algorithm. In addition, according to the size of the single pattern P, the two-dimensional period of the grating unit 204 can be calculated, and the structure of the grating is vector-optimized and designed according to the target array number (M*N) and the two-dimensional period to achieve uniform energy distribution, which will not be repeated here. After adding the grating unit 204, the human eye can see the pattern in a larger FOV.

[0065] based on Figure 3In the embodiment, an active light source projection method is used, after the light beam emitted by the light source 201, such as a laser or a light emitting diode, passes through the shaping lens 202, the diffractive optical element 203 and the two-dimensional array grating 204, a suspended periodic array indicator pattern can be formed, for example, at a distance S2 of 15 cm from the two-dimensional array grating 204, and the human eye can observe indicator patterns of different periods when located at different viewing angles. The diffractive optical element 203 realizes the formation of a real image in a small area, and the array grating realizes the periodic arrangement of the pattern on the real image plane.

[0066] In the above embodiments, the present invention proposes a solution for realizing suspended imaging in the air. By illuminating a diffractive optical element (DOE) designed with collimated light using a divergent light source, a suspended real image is formed at a specific position in the air. The diffractive optical element designed based on collimated light will form an image at infinity. After adding a divergent light source (LD or monochromatic LED) and a collimating lens (or Fresnel lens) before the diffractive optical element, the distance from the light source to the collimating lens is adjusted according to the object-image relationship of the lens in geometric optics, so that imaging can be achieved at a specific position in the air. The larger the physical size of the DOE, the larger the visual angle range (FOV) of the human eye observing the suspended image. Generally, the size of the DOE is limited by the size of the device structure. In order to further increase the visual angle range (FOV) of the suspended image, a grating can be added after the DOE to expand the array of the suspended image, so that the human eye can see the suspended image in a larger FOV range, and the visual effect is better.

[0067] The present invention also relates to a method 300 for suspended imaging, such as Figure 4 As shown, the method can be performed, for example, by Figure 1-3 The method 300 is implemented by the optical system 100 or 200 shown. The method 300 includes:

[0068] In step S301, a divergent light beam is emitted by a light source. Figure 1 or Figure 3 The light source 101 or 201 shown in FIG. 1 emits a divergent light beam.

[0069] In step S302, the light beam emitted by the light source is received by a shaping lens, and then adjusted and emitted. Figure 1 or Figure 3 The shaping lens 102 or 202 shown in .

[0070] In step S303, the outgoing light beam is received by a diffractive optical element, and a light field with a specific pattern is projected at a preset position in space. Figure 1 or Figure 3 The shaping lens 103 or 203 shown in FIG.

[0071] According to a preferred embodiment of the present invention, the method 300 further comprises: adjusting the distance between the light source and the focal plane of the shaping lens so that the optical system projects the light field with the specific pattern at the preset position.

[0072] According to a preferred embodiment of the present invention, the method 300 further comprises: replicating the light field having the specific pattern at the preset position by means of a grating unit.

[0073] According to a preferred embodiment of the present invention, the grating unit includes a two-dimensional grating, and the method further includes: expanding the light field with the specific pattern in the form of an array at the preset position through the two-dimensional grating.

[0074] In the above embodiments, the optical system 100 or 200 includes a shaping lens and a diffractive optical element separated from each other. The present invention is not limited thereto, and the shaping lens may be fully or partially integrated into the diffractive optical element. Figure 5 An optical system 400 according to another embodiment of the present invention is shown. Figure 5 Detailed description.

[0075] like Figure 5 As shown, the optical system 400 includes a light source 401 and a diffractive optical element 403. The light source 401 is configured to emit a divergent light beam. The diffractive optical element 403 integrates Figure 2 and Figure 3 The functions of the shaping lens (102, 202) and the diffractive optical element (103, 203) in the embodiment. The diffractive optical element 403 is located downstream of the light path of the light source 401, receives the light beam emitted by the light source 401 and shapes it, and projects a suspended light field with a specific pattern (such as Figure 5 The invention relates to a palm-shaped pattern P on the IP plane, wherein the diffractive optical element comprises a microstructure surface on which one or more microstructure pattern units are arranged, and the microstructure pattern units are configured to modulate the incident light to shape the light beam and project the light field having the specific pattern.

[0076] Figure 5 The diffractive optical element 403 in the embodiment can be divided into two parts in terms of functional logic, namely beam shaping and pattern projection, and the functions of these two parts are not prioritized.

[0077] When designing the diffractive optical element 403, the parameters of the light beam emitted by the light source 401 (such as the light source position, divergence angle, wavelength and other parameters) and the parameters of the target light field (such as the position of the target light field, the pattern of the target light field, etc.) are directly given to calculate the phase distribution of the microstructure pattern unit for manufacturing the diffractive optical element 403. Therefore, in this embodiment, the diffractive optical element 403 is designed for divergent light.

[0078] Similar to Figure 3 Example, in Figure 5 In the embodiment of the present invention, the optical system 400 preferably further includes a grating unit 404, which is located downstream of the optical path of the diffractive optical element 403 and is configured to replicate the light field with a specific pattern at the preset position in space. The grating unit 404 may be, for example, a two-dimensional grating, configured to expand the light field with a specific pattern at the preset position in space in an array form, such as Figure 5 As shown, through the grating unit, the palm-shaped pattern P is replicated and expanded in a two-dimensional direction on the IP plane.

[0079] The above focuses on describing Figure 5 Example and Figure 1-3 The embodiments are different. Figure 1-3 The other features described in the embodiments can be freely combined and applied to Figure 5 The optical system 400 of the embodiment will not be described in detail here.

[0080] The present invention also provides a method for suspended imaging, for example, by Figure 5 The optical system 400 is used for testing. The method comprises:

[0081] S501: emitting a divergent light beam through a light source;

[0082] S502: Receive the outgoing light beam through a diffractive optical element, perform shaping and modulation, and project a light field with a specific pattern at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to modulate the incident light to project the light field with the specific pattern.

[0083] According to one aspect of the present invention, the method further comprises:

[0084] The light field with the specific pattern is expanded in an array form at the preset position through a two-dimensional grating.

[0085] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical system for suspended imaging, characterized in that: include: a light source configured to emit a divergent light beam; A shaping lens, located downstream of the optical path of the light source, configured to receive the light beam emitted by the light source and emit it after adjustment; A diffractive optical element is located downstream of the optical path of the shaping lens, and is configured to receive the outgoing light beam and project a suspended light field with a specific pattern at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to modulate the incident light to project the light field with the specific pattern, and the specific pattern includes one or more of a palm shape, a palm print, a fingerprint, an arrow, and a finger. The distance between the light source and the focal plane of the shaping lens is set so that the diffractive optical element projects the light field with the specific pattern at the preset position, wherein the light source is a point light source, and the point light source is arranged at a position away from the focal plane of the shaping lens along the light propagation direction, and the shaping lens is configured to converge the divergent light beam from the light source and then make it incident on the diffractive optical element downstream of the optical path.

2. The optical system of claim 1, wherein: The distance between the point light source and the focal plane of the shaping lens is adjusted so that the optical system projects the light field with the specific pattern at the preset position.

3. An optical system as claimed in claim 1 or 2, wherein the point light source comprises one or more of a semiconductor laser and a light emitting diode.

4. The optical system as claimed in claim 1 or 2, wherein the shaping lens comprises one or more of a collimator lens and a Fresnel lens. 5 . The optical system as claimed in claim 1 , wherein the diffractive optical element is designed with parallel light as the light source and the light field with the specific pattern as the target light field. The optical system as claimed in claim 5 , wherein the specific pattern comprises one or more of a stereogram and a plan view.

7. The optical system of claim 1 or 2, further comprising: The grating unit is located downstream of the optical path of the diffractive optical element and is configured to replicate the light field with a specific pattern at the preset position in space. 8 . The optical system of claim 7 , wherein the grating unit comprises a two-dimensional grating configured to expand the light field having the specific pattern at the preset position in space in an array form.

9. A method for suspended imaging, characterized in that: include: A divergent light beam is emitted by a light source; The light beam emitted by the light source is received by a shaping lens, and then adjusted and emitted; The outgoing light beam is received by a diffractive optical element, and a light field with a specific pattern is projected at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to modulate the incident light to project the light field with the specific pattern, and the specific pattern includes one or more of a palm shape, a palm print, a fingerprint, an arrow, and a finger. The distance between the light source and the focal plane of the shaping lens is set so that the diffractive optical element projects the light field with the specific pattern at the preset position, wherein the light source is a point light source, and the point light source is arranged at a position away from the focal plane of the shaping lens along the light propagation direction, and the shaping lens converges the divergent light beam from the light source and then makes it incident on the diffractive optical element downstream of the optical path.

10. The method of claim 9, further comprising: The distance between the light source and the focal plane of the shaping lens is adjusted so that the optical system projects the light field with the specific pattern at the preset position.

11. The method of claim 9 or 10, further comprising: The light field with the specific pattern is replicated at the preset position through the grating unit.

12. The method of claim 11, wherein the grating unit comprises a two-dimensional grating, the method further comprising: The light field with the specific pattern is expanded in an array form at the preset position through the two-dimensional grating.

13. An optical system for suspended imaging, characterized in that: include: a light source configured to emit a divergent light beam; and A diffractive optical element is located downstream of the optical path of the light source, configured to receive and shape the light beam emitted by the light source, and project a suspended light field with a specific pattern at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to shape and modulate the incident light to project the light field with the specific pattern, and the specific pattern includes one or more of a palm shape, a palm print, a fingerprint, an arrow, and a finger. The distance between the light source and the focal plane of the shaping lens integrated in the diffractive optical element is set so that the diffractive optical element projects the light field with the specific pattern at the preset position, wherein the light source is a point light source, and the point light source is arranged at a position away from the focal plane of the shaping lens along the light propagation direction, and the shaping lens is configured to converge the divergent light beams from the light source.

14. The optical system of claim 13, further comprising: The grating unit is located downstream of the optical path of the diffractive optical element and is configured to replicate the light field with a specific pattern at the preset position in space. 15 . The optical system of claim 14 , wherein the grating unit comprises a two-dimensional grating configured to expand the light field having the specific pattern at the preset positions in space in an array form.

16. A method for suspended imaging, characterized in that: include: A divergent light beam is emitted by a light source; An outgoing light beam is received by a diffractive optical element, shaped and modulated, and a light field with a specific pattern is projected at a preset position in space, wherein the diffractive optical element includes a microstructure surface, and one or more microstructure pattern units are arranged on the microstructure surface, and the microstructure pattern units are configured to shape and modulate the incident light to project the light field with the specific pattern, and the specific pattern includes one or more of a palm shape, a palm print, a fingerprint, an arrow, and a finger. The distance between the light source and the focal plane of the shaping lens integrated in the diffractive optical element is set so that the diffractive optical element projects the light field with the specific pattern at the preset position, wherein the light source is a point light source, and the point light source is arranged at a position away from the focal plane of the shaping lens along the light propagation direction, and the shaping lens is configured to converge the divergent light beams from the light source.

17. The method of claim 16, wherein the method further comprises: The light field with the specific pattern is expanded in an array form at the preset position through a two-dimensional grating.

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