A Bragg periodic scanning holographic imager

Abstract

The present invention relates to the field of 3D imaging, and discloses a Bragg periodic scanning holographic imager, which includes an imaging element, an imaging lens group and a focal depth scanning mechanism respectively arranged inside the holographic imager. The imaging element is used to provide a plurality of non-coincident or parallel equivalent image planes, and the imaging lens group is used for optical imaging and forms a plurality of two-dimensional sections; the focal depth scanning mechanism is respectively connected to drive the imaging element and / or the imaging lens group, and is used to control the spatial position change of the imaging element and / or the imaging lens group to realize volume scanning of the two-dimensional sections. The present invention can stably realize the 3D imaging / projection display function with ultra-high resolution and ultra-fast frame rate by introducing multi-focal planes and Bragg periodic scanning methods.

Description

Technical Field

[0001] The present invention relates to the field of 3D imaging, and particularly to a Bragg-period scanning holographic imager. Background Art

[0002] 3D display technology can provide additional depth information on the basis of traditional 2D displays, so it is considered the development direction of the next-generation display technology. However, there is currently no relatively effective solution for realizing 3D display. Most commercially successful cases are pseudo-3D technologies based on stereoscopic image pairs, which cannot provide users with a truly 3D picture with depth information. For example, the 3D movies in cinemas work by using projectors to project two 2D left and right eye image pairs on the screen. By wearing selective filtering glasses, the two eyes receive different pictures, thus creating an illusion of seeing a 3D picture. In fact, the projected picture is just a 2D picture. Prolonged viewing can also cause eye discomfort.

[0003] Using the volume scanning imaging method can achieve a true 3D effect and is already a very promising 3D solution. However, volume scanning imaging 3D often requires a high-speed rotating / moving screen, the system has relatively large safety hazards, poor stability, very limited display space, cannot be directly touched and interacted with, and the display picture is transparent and cannot express the correct occlusion relationship.

[0004] Patents with the authorization numbers CN106773469B, CN 207114903 U, and CN 206431409 U disclose a solution that can achieve true 3D display. Its key component is a stereoscopic display module, which can reproduce a true 3D picture through depth-of-field scanning. Its working principle is to reciprocally scan a focal plane in the depth direction (depth-of-field scanning) to form a continuous 3D picture. In this way, although a 3D picture can be projected, it depends on the scanning imaging of a single focal plane, has extremely high requirements for the movement speed of the mechanical structural parts of the display system, cannot guarantee the reliability of the system, cannot optimize the frame refresh rate and the overall brightness of the picture, and at the same time makes the operation and control system extremely complex, difficult to achieve stable picture display, and has extremely high manufacturing costs. A full-solid-state holographic projector with the application number 202010029144.5 discloses an effect of full-solid-state holographic display by setting multiple discrete focal planes in a projector. However, the 3D picture formed in this way is not continuous but a slice-by-slice picture in real space, and cannot fully achieve a continuous 3D picture. At the same time, for 3D images with a relatively large depth-of-field variation range, its visual performance ability cannot meet the psychological expectations of users.

[0005] To achieve 3D display, in addition to a device capable of displaying 3D images, a device capable of recording 3D videos is also required. According to the principle of reversibility of light paths, the light path used for 3D display can, conversely, be used to shoot 3D videos. Summary of the Invention

[0006] The technical problem to be solved by the present invention is as follows: In view of the deficiencies of the above-mentioned prior art, a Bragg period scanning holographic imager is provided. By introducing a focal depth scanning mechanism to perform a small-amplitude (Bragg period scanning) scan of a two-dimensional section, continuous full-scene reproduction can be achieved. Compared with the conventional volume scanning 3D method, reliability is ensured, and at the same time, the refresh rate can be increased by more than one order of magnitude, greatly improving the user's viewing experience.

[0007] To solve the above technical problem, the present invention proposes a Bragg period scanning holographic imager, which includes the following components respectively arranged inside the holographic imager:

[0008] An imaging element for providing a plurality of non-coincident or parallel equivalent image planes, and the number of the equivalent image planes is n;

[0009] An imaging lens group, whose position corresponds to the equivalent image plane, for optical imaging and forming a plurality of two-dimensional sections; and

[0010] A focal depth scanning mechanism, connected to the imaging element and / or the imaging lens group respectively, for controlling the spatial position change of the imaging element and / or the imaging lens group to perform volume scanning on the two-dimensional section.

[0011] Further, the scanning frequency or equivalent frequency of the focal depth scanning mechanism is greater than

[0012] Further, the focal depth scanning mechanism performs volume scanning on the two-dimensional section by changing the spatial position between the equivalent image plane and the imaging lens group and / or the effective focal length of the imaging lens group.

[0013] Further, the focal depth scanning mechanism performs volume scanning on the two-dimensional section by changing the relative position and / or the overall position of the optical elements in the imaging lens group.

[0014] Further, the imaging lens group includes at least a liquid zoom lens or a flexible zoom lens.

[0015] Further, the amplitude of the volume scanning along the focal depth direction controlled by the focal depth scanning mechanism is L1 mm, and the depth of distribution of the plurality of equivalent image planes along the focal depth direction is L2 mm, satisfying L1 < L2.

[0016] Further, the mass Mg of the imaging element and the number n of the equivalent image planes satisfy:

[0017] Further, the imaging element is a projection display element or an imaging sensor element.

[0018] Further, a plurality of projection display chips and imaging sensor chips are provided inside the imaging element to realize the dual functions of projection and imaging.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] 1. The present invention can realize the reproduction of a completely continuous 3D scene, which is a holographic display in the true sense;

[0021] 2. During the working process of the present invention, only a small range of scanning (Bragg period scanning) is required to realize the reproduction of a continuous full scene. Compared with the conventional volume scanning 3D method, the reliability is guaranteed. At the same time, the refresh rate can be increased by more than one order of magnitude, greatly improving the user viewing experience; there is no safety hazard, the touch operation of the 3D picture can be realized, and the occlusion relationship can be correctly represented;

[0022] 3. When the present invention is applied, the eyes need to perform dynamic adjustment of the depth of focus like viewing real objects, rather than the fixed depth of focus of a common 2D display screen. Therefore, it will not cause visual fatigue and is helpful for protecting eyesight;

[0023] 4. The present invention can simultaneously realize the functions of projection and imaging, facilitating the simultaneous output of picture information and real-time reception of external image information during practical application. For example, user interaction actions and expression information can be recognized while displaying. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 FIG. is a schematic diagram of the imager in which the imaging element 1 is a projection display element and the system of Embodiment 1;

[0026] Figure 2 In Figure 1 On the basis of, a schematic diagram of the equivalent image plane 2 that simultaneously includes the physical real image plane and the virtual image plane obtained by optical conversion provided by the imaging element 1 is shown.

[0027] Figure 3 For Figure 1 On the basis of, a schematic diagram of the system of the imager of the present invention in which the projection display element is replaced with an imaging sensor element is shown.

[0028] Figure 4 For Figure 3 On the basis of, the equivalent image plane 2 includes a schematic diagram of the physical real image plane and the virtual image plane obtained through optical conversion, highlighting Figure 3 The difference between the equivalent image plane 2 and the two-dimensional section 4 in

[0029] Figure 5 Is the system schematic diagram of Embodiment 2

[0030] Figure 6 Is the system schematic diagram of Embodiment 3

[0031] Figure 7 Is the state schematic diagram of one vibration period of the equivalent image plane 2

[0032] Figure 8 Is the principle schematic diagram of the mechanical zoom of the imaging lens group 3

[0033] Figure 9 Is the zoom principle schematic diagram of the imaging lens group 3 using a flexible zoom lens

[0034] The reference numerals are as follows:

[0035] Imaging element 1, equivalent image plane 2, imaging lens group 3, two-dimensional section 4, depth-of-field scanning mechanism 5 Specific implementation manners

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description of this part is only exemplary and explanatory, and should not have any restrictive effect on the protection scope of the present invention

[0037] Referring to Figures 1 to 9 , the present invention provides a Bragg period scanning holographic imager, including an imaging element 1, an imaging lens group 3, and a depth-of-field scanning mechanism 5 respectively disposed inside the holographic imager

[0038] The imaging element 1 is used to provide a plurality of non-coincident or parallel equivalent image planes 2. The number of image planes of the equivalent image plane 2 is n. These equivalent image planes 2 can be physical real image planes, or virtual image planes or real image planes obtained through optical conversion, etc. The specific implementation manners are described in detail in a full-solid-state holographic projector with the application number 202010029144.5, which will not be elaborated here

[0039] The position of the imaging lens group 3 corresponds to the equivalent image plane 2 and is used for optical imaging and forming a plurality of two-dimensional sections 4

[0040] The depth of focus scanning mechanism 5 is respectively connected to the imaging element 1 and / or the imaging lens group 3, and is used to control the spatial position change of the imaging element 1 and / or the imaging lens group 3, so as to realize volume scanning of the two-dimensional section 4. Preferably, reciprocating motion back and forth is used to realize volume scanning;

[0041] This kind of volume scanning is equivalent to the depth of field scanning of a 3D picture, and can scan an imaging space, in which an array of denser two-dimensional sections 4 or a continuous 3D picture is formed. Preferably, the present invention realizes periodic volume scanning by controlling the periodic position change of each component.

[0042] Each equivalent image plane 2 and the two-dimensional section 4 are both full of pixel arrays (two-dimensional). Multiple equivalent image planes 2 and two-dimensional sections 4 can respectively form three-dimensional pixel arrays. This unique multi-section image plane structure is very similar to the three-dimensional Bragg lattice structure. The characteristic of this structure is that as long as the whole is moved by one Bragg period, a space much larger than the Bragg unit cell can be scanned, so the scanning frequency can be greatly improved. Since the Bragg period length is very small, the moving range of the scanning mechanism is very small, and the stability and reliability are much higher than those of the conventional large-scale scanning system.

[0043] Among them, the imaging element 1 can be a projection display element or a photographing light-sensitive element;

[0044] Such as Figure 1 and Figure 2 , when the projection display element is used as the imaging element 1, the scanning imager of the present invention is used as a holographic projector:

[0045] The light of the projection display element is optically converted by the imaging lens group 3 to form a plurality of two-dimensional sections 4 in space, and forms a two-dimensional section array, which is equivalent to the display effect that the imaging lens group 3 directly projects a plurality of equivalent image planes 2 optically conjugate to the two-dimensional section array. By controlling the spatial position change of the projection display element and / or the imaging lens group 3 by the depth of focus scanning mechanism 5, preferably periodic change, the relative position or the overall position between the equivalent image plane 2 and the imaging lens group 3 changes periodically, and the array of two-dimensional sections 4 in space also vibrates in the depth of focus direction to perform volume scanning. The previous multi-layer section type and discontinuous three-dimensional display effect form a denser array of two-dimensional sections 4 or a continuous 3D picture after scanning, realizing a continuous 3D display effect;

[0046] And there is optical conjugation between the above two-dimensional section 4 and the equivalent image plane 2. Therefore, when performing volume scanning on the array of two-dimensional sections 4, multiple equivalent image planes 2 are also performing volume scanning at the same time;

[0047] Such as Figure 3 and Figure 4, when the imaging element 1 is the shooting photosensitive element, the scanning imager of the present invention is used as a holographic camera:

[0048] Similar to the above projection process, according to the principle of optical path reversibility, the light rays of the external scene are optically converted by the imaging lens group 3 and then multiple real image two-dimensional sections 4 are generated and recorded on the shooting photosensitive element, which is equivalent to the effect that the light rays of the external scene directly generate multiple equivalent image planes 2 that are optically conjugate to the external scene after optical imaging by the imaging lens group 3;

[0049] This is very similar to the working principle of an ordinary camera. The difference is that an ordinary camera has only one photosensitive chip and can only record the scene information at the optically conjugate position corresponding to it, while the shooting photosensitive element of the present invention contains multiple photosensitive chips. Therefore, multiple images can be recorded simultaneously, and each image corresponds to the scene at a different depth of field, achieving a slice 3D-like shooting record. By controlling the spatial position change of the shooting photosensitive element and / or the imaging lens group 3 through the depth of focus scanning mechanism 5, preferably a periodic change, the relative position or the overall position between the equivalent image plane 2 and the imaging lens group 3 changes periodically, and accordingly, the depth of field space optically conjugate to the photosensitive chip or the equivalent image plane 2 also undergoes a periodic scan, so that the information at different depths of the scene is recorded separately, thereby recording a complete and continuous 3D scene and achieving the purpose of 3D shooting. According to the optical path reversibility, during the process of the depth of field space optically conjugate to the shooting photosensitive chip or the equivalent image plane 2 undergoing a periodic scan, the equivalent image plane 2 undergoes a corresponding periodic scan, and there is an equivalent relationship between the above equivalent image plane 2 and the two-dimensional section 4. Therefore, the scan of the equivalent image plane 2 can be equivalent to the scan of the two-dimensional section 4;

[0050] The present invention preferably realizes periodic volume scanning by controlling the periodic position change of each component. For example, by mechanically controlling the periodic reciprocating scanning movement of the imaging element 1 in space, a continuous space can be swept out in space. In practical applications, it can be reciprocally scanned at a fixed frequency, or scanned at different frequencies according to the needs of the display content;

[0051] Or by controlling the periodic change of the effective focal length of the imaging lens group 3 through the depth of focus scanning mechanism 5, the reciprocating scan of the two-dimensional section 4 can also be realized. The periodic change of the effective focal length of the imaging lens group 3 can be achieved by changing the relative position and / or the overall position of the optical elements in the imaging lens group 3 (mechanical zoom method), or by setting a liquid zoom lens and / or a flexible zoom lens with zoom function in the imaging lens group 3;

[0052] In addition, in addition to performing a simple one-dimensional depth of field scan, a three-dimensional scan method can be used to further improve the display effect. For example, adding a scan parallel to the equivalent image plane 2 can further increase the horizontal resolution and make the image quality more delicate.

[0053] The design of the specific scanning mechanism belongs to the common general knowledge in the art and can be designed according to the actual usage scenario, so it will not be elaborated here.

[0054] The following takes the holographic imager of the present invention with the imaging element 1 as the projection display element and the number n of the equivalent image planes 2 being 3 as an example to further illustrate the present invention:

[0055] Embodiment 1

[0056] As Figure 1 , the Bragg period scanning holographic imager includes a projection display element, an imaging lens group 3 and a depth of focus scanning mechanism 5 respectively arranged inside. The depth of focus scanning mechanism 5 is connected to the projection display element and controls the projection display element to make periodic reciprocating movements back and forth in the depth of field direction, so that the relative position between the equivalent image plane 2 and the imaging lens group 3 also makes periodic changes, and the two-dimensional section 4 optically conjugated to the equivalent image plane 2 vibrates in the depth of focus direction to perform periodic reciprocating scans, thereby realizing a continuous 3D display effect.

[0057] Embodiment 2

[0058] As Figure 5 , the Bragg period scanning holographic imager includes a projection display element, an imaging lens group 3 and a depth of focus scanning mechanism 5 respectively arranged inside. The depth of focus scanning mechanism 5 is connected to the imaging lens group 3 and controls the imaging lens group 3 to make periodic reciprocating movements back and forth in the depth of field direction, so that the relative position between the equivalent image plane 2 and the imaging lens group 3 makes periodic changes, and the two-dimensional section 4 optically conjugated to the equivalent image plane 2 vibrates in the depth of focus direction to perform periodic reciprocating scans, thereby realizing a continuous 3D display effect.

[0059] Embodiment 3

[0060] As Figure 6 , the Bragg period scanning holographic imager includes a projection display element, an imaging lens group 3 and a depth of focus scanning mechanism 5 respectively arranged inside. The depth of focus scanning mechanism 5 is respectively connected to the projection display element and the imaging lens group 3 and controls the periodic reciprocating movements back and forth of their spatial positions, so that the relative position or the overall position between the equivalent image plane 2 and the imaging lens group 3 makes periodic changes, and the two-dimensional section 4 optically conjugated to the equivalent image plane 2 vibrates in the depth of focus direction to perform periodic reciprocating scans, thereby realizing a continuous 3D display effect.

[0061] Embodiment 4

[0062] The Bragg period scanning holographic imager includes a projection display element, an imaging lens group 3, and a depth of focus scanning mechanism 5 disposed inside. The depth of focus scanning mechanism 5 is connected to the projection display element and controls the relative position and / or the overall position of a plurality of optical elements provided inside the imaging lens group 3 to change, periodically changing the effective focal length of the imaging lens group 3, such as Figure 8 , this mechanical zoom causes the spatial position of the two-dimensional section 4 to change periodically, and the two-dimensional section 4 vibrates in the depth of focus direction to perform reciprocating scanning back and forth, thereby achieving a continuous 3D display effect.

[0063] Embodiment 5

[0064] The Bragg period scanning holographic imager includes a projection display element, an imaging lens group 3, and a depth of focus scanning mechanism 5 disposed inside. The imaging lens group 3 is provided with a flexible zoom lens having a zoom function. The depth of focus scanning mechanism 5 is connected to the imaging lens group 3 and controls the effective focal length of the flexible zoom lens to change periodically, such as Figure 9 , causing the spatial position of the two-dimensional section 4 to change periodically, and the two-dimensional section 4 vibrates in the depth of focus direction to perform reciprocating scanning back and forth, thereby achieving a continuous 3D display effect.

[0065] It should be noted that the flexible zoom lens in Embodiment 5 can be replaced with a liquid zoom lens or other lenses having a zoom function.

[0066] Embodiments 1 to 5 respectively embody volume scanning for reciprocating scanning of the two-dimensional section 4 in different ways, and finally all achieve a continuous 3D display effect.

[0067] According to the principle of reversibility of light paths, the projection display element in Embodiments 1 to 5 can also be replaced with a photographing light-sensitive element, such as Figure 2 , to achieve the effect of 3D photographing.

[0068] Such as Figure 7 As shown, when the depth of focus scanning mechanism 5 operates to perform reciprocating scanning (volume scanning) on the two-dimensional section 4 during the actual application of the present invention, the equivalent image plane 3 optically conjugate to the two-dimensional section 4 also performs volume scanning at the same time;

[0069] The vibration controlled by the depth of focus scanning mechanism 5 actually has a corresponding relationship with the scanning of the equivalent image plane 2. However, based on the lens imaging law, the scanning of the two-dimensional section 4 in the depth of focus direction and the scanning of the equivalent image plane 2 are not linearly corresponding. Therefore, it is more convenient to design the relevant design parameters with reference to the equivalent image plane 2;

[0070] The amplitude of the equivalent image plane 2 in the depth of focus direction (i.e., the maximum displacement of the equivalent image plane 2 from the equilibrium position in the depth of focus direction) is L1 mm, and the depth of distribution of multiple equivalent image planes 2 in the depth of focus direction (i.e., the central distance between the foreground equivalent image plane 2 closest to the imaging lens group 3 and the background equivalent image plane 2 farthest from the imaging lens group 3) is L2 mm. It should satisfy L1 < L2, and only in this way can the amplitude of the volume scan be relatively smaller.

[0071] The equilibrium positions of the above-mentioned equivalent image plane 2 are respectively the midpoints between the two points of the amplitude point in the depth of focus direction and the amplitude point in the opposite direction of the depth of focus of the equivalent image plane 2, and the amplitude points of the equivalent image plane 3 are as Figure 7 shown: Define the maximum displacement of the equivalent image plane 2 in the depth of focus direction as the amplitude point in the depth of focus direction, and the maximum displacement in the opposite direction of the depth of focus as the amplitude point in the opposite direction of the depth of focus.

[0072] Considering that as long as the gap between adjacent equivalent image planes 2 can be completely scanned through the scanning action, a continuous 3D picture space can be realized. Therefore, as long as the scanning amplitude is greater than the distance between the largest adjacent equivalent image planes 2, the scanning of a complete continuous space can be realized.

[0073] During design, it can be preferably selected: Within this design parameter range, on the premise of making the amplitude very small, it can also ensure finding appropriate design parameters so that the equivalent image plane 2 can sweep out a complete continuous space in the space (in fact, there is a certain overlap in the space swept by adjacent equivalent image planes 2, completely avoiding the problem of longitudinal depth of field discontinuity, and at the same time leaving enough design margin to allow a part of a scanning cycle to be used to update the display screen during design, increasing design flexibility), and the scanning amplitude can be reduced to a very small value.

[0074] Of course, in actual applications, sometimes the scanning amplitude can be made larger to show a more delicate picture effect, or it can be smaller for scenarios with low requirements for depth resolution.

[0075] During actual application, the scanning frequency or equivalent frequency of the depth of focus scanning mechanism 5 is preferably greater than Here, the frequency refers to the reciprocal of the time interval between two consecutive passes of a moving part through a certain space point in the same direction. For example, during the reciprocating scanning of the imaging element 1, it is the reciprocal of the time between two consecutive passes through the equilibrium position in the same direction. In addition, for the case of scanning by means of zooming, it can be equivalent to the reciprocal of the time from the initial focal length of the imaging lens group 3 back to this focal length again. The initial focal length refers to the focal length of the imaging lens group 3 when the depth of focus scanning mechanism 5 is not operating. Of course, it can also be obtained by measuring the reciprocal of the time interval between two consecutive same-direction sweeps of the projection focal plane through a certain position in space.

[0076] When displaying a 3D image within a certain space, it is necessary to scan the focal plane back and forth within a certain space to update the entire space image. Therefore, the frame rate of the 3D image is the depth of field scanning frequency.

[0077] In addition, there is a special case. When the display space undergoes overall movement, such as during the process of moving from a close view to a distant view, during the switching process, the depth of field often only needs to move in one direction without reciprocating scanning. In this case, there is no concept of depth of field scanning. However, the display depth of field switching process also needs to be completed at a relatively appropriate speed; otherwise, problems such as image jitter or trailing are likely to occur. For this situation, we introduce the concept of equivalent frequency: The equivalent frequency refers to the reciprocal of the time taken during the process when the equivalent image plane 2 moves unidirectionally relative to the imaging lens group 3 and the movement distance is equal to the maximum adjacent spacing between adjacent equivalent image planes 2.

[0078] For the case of scanning using the zoom method, the reciprocal of the time taken for the equivalent focal length to change from the initial focal length back to the same focal length (or the reciprocal of the time interval for the maximum focal length to change back to the maximum focal length) can be used. The initial focal length refers to the focal length of the imaging lens group 3 when the depth of field scanning mechanism 5 is not operating. Of course, it can also be obtained by measuring the reciprocal of the time interval between two consecutive sweeps of the projection focal plane across a certain position in space in the same direction.

[0079] In actual applications, it is found that the larger the number n of equivalent image planes 2, the denser the two-dimensional cross-sections will be. In general display situations, a relatively good stereoscopic display effect can basically be presented. Therefore, it is only necessary to perform a depth of field scanning operation to re-match the depth of field of the display space when there is a large change in the overall depth of field of the display content. For example, when the display content of a movie changes from an indoor scene to an open outdoor scene or an outer space galaxy scene, at this time, the depth of field of the display changes significantly. Usually, such a large depth of field difference scene switch is completed within multiple frames of images, and the conversion process is relatively slow. Therefore, it is only necessary for the display system to achieve depth of field switching relatively slowly, so the scanning frequency (equivalent frequency) can be much lower than the frame rate of the 3D video. This can also greatly reduce the requirements for the computing and control systems, making the system more stable;

[0080] On the other hand, the larger n is, the greater the total mass of the corresponding components will be, and the natural frequency of the system will decrease. As a result, it is relatively difficult to achieve a high scanning frequency. Therefore, it is necessary to lower the lower limit of the scanning frequency to protect the reliability of the system.

[0081] Generally, the display screen is within a relatively small range, such as an indoor scene. At this time, the projection space of the equivalent image plane 2 may fully meet the display requirements of this small space range. In this case, even without performing the depth of focus scanning operation, the 3D scene can be relatively realistically restored. Or, in order to make the display effect more delicate, only a very small amplitude of scanning is required.

[0082] Only when the change range of the display depth of field is large, or when the overall depth of field changes greatly, a large amplitude of scanning or overall translation is required for the depth of focus scanning.

[0083] It should be noted that in many cases, the depth of field switching does not require a complete scanning cycle.

[0084] For example, when the screen scene slowly switches from a close view to a distant view and then stays at the distant view for a period of time, the depth of focus scanning only needs to correspondingly adjust the depth of field of the screen. At this time, the equivalent frequency concept can be used. In summary, the scanning frequency can find a suitable design range to meet the balance of various requirements.

[0085] The following are the feedback situations of several users during actual tests:

[0086]

[0087] Judging from the data, for general application scenarios with not particularly high requirements, the scanning frequency (or equivalent frequency) is preferably greater than When this is the case, the comprehensive score of users is higher than 60 points, which can meet the needs of general users;

[0088] Of course, in order to further improve the 3D display effect and improve the comprehensive performance score, for some special application scenarios, it is preferred that n≥2 and the scanning frequency

[0089] For some users who pursue an extreme experience, it is preferred that n≥3 and the scanning frequency

[0090] Generally, the depth resolution of the human eye is much lower than the horizontal resolution. Therefore, even if the pixel pitch in the depth direction is relatively large, it will not cause resolution distortion. Therefore, the pixel pitch of the projection screen in the depth direction can be set larger, so that a very realistic 3D picture can be projected under the condition of effectively reducing the equipment and process costs.

[0091] In addition, the quality Mg of the imaging element 1 satisfies the relationship with the number n of equivalent image planes Among them, the mass M of the imaging element 1 refers to the mass of the remaining part after removing the imaging lens group, support mechanism, wire harness and other auxiliary components in the holographic imager.

[0092] Here, a holographic projector is taken as an example for illustration. Usually, the main application field of a holographic projector is a geometric holographic display system (refer to the patent document with the application number 201910875975.1). In such a system, the holographic projector often needs to be in a moving state. Therefore, its mass cannot be too large. Otherwise, controlling the movement of a component with too large a mass will have a very large inertia due to the mass, resulting in extremely difficult operation and extremely high energy consumption. On the other hand, it will cause a great burden on the support structure, and the entire system will be very bulky and impractical. Therefore, it is necessary to reasonably design its mass. Ideally, the smaller the overall mass, the better. However, the equivalent image plane 2 must depend on the physical entity. Thus, the larger the number of equivalent image planes 2, the larger the overall mass. If you want to design a holographic projector as light as possible, then it is necessary to sacrifice the number of equivalent image planes 2. If you want to obtain a denser equivalent image plane 2, you have to accept the increase in mass. The two cannot reach the optimal state simultaneously. The present invention provides a design criterion for weighing the relationship between the two, that is

[0093] This design relationship indirectly limits the size of the total mass and gives the upper limit boundary of the holographic projector in the case of different numbers of equivalent image planes 2. When exceeding this upper limit boundary, the practicality of the produced holographic projector will be very poor. For example, for living room display, using 11 equivalent image planes 2 for depth-of-field performance can achieve a very perfect display effect. And the maximum mass of moving objects in the living room should not exceed 5000g. Otherwise, on the one hand, there may be potential safety hazards to people, and on the other hand, the support structure will be very bulky, occupying a large amount of space and not being very beautiful. For this boundary situation is used as the design upper limit. In actual tests, it is also found that the vast majority of families are not willing to accept products that exceed this design boundary.

[0094] In addition, for desktop office scenarios, when designing, it is preferably to select a more stringent design specification, preferably At this time, both the overall structure and the display performance are more ideal. The actual test results show that users generally rate products that meet the design rules higher than 60 points;

[0095] Furthermore, preferably At this time, the entire system is more compact, flexible, and beautiful. The actual test results show that users generally rate products that meet the design rules higher than 70 points;

[0096] Furthermore, preferably At this time, it is equivalent to further tightening the design boundary. The system is not only compact but also can add some appearance design elements to make the customer attraction of the system stronger. The actual test results show that users generally rate products that meet the design rules higher than 90 points;

[0097] It should be noted that the Bragg period scanning holographic imager of the present invention with the projection display element as the imaging element 1 is used as a holographic projector, and the Bragg period scanning holographic imager of the present invention with the photosensitive element as the imaging element 1 is used as a holographic camera. The above design description is mainly an explanation for the case of the holographic projector. However, since the application scenarios of the holographic camera are very similar, based on the principle of optical path reversibility, the problems that need to be considered in the holographic projector will also be encountered in the holographic camera. Therefore, the above design description also applies to the holographic camera.

[0098] Inside the imaging element 1 of the present invention, a number of projection display chips and photosensitive chips for shooting can be respectively provided to achieve the dual functions of projection and shooting.

[0099] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A Bragg periodic scanning holographic imager, characterized in that, Including those respectively arranged inside the holographic imager: An imaging element (1) for providing a plurality of non-coincident or parallel equivalent image planes (2), the number of the equivalent image planes (2) being n; An imaging lens group (3) whose position corresponds to the equivalent image plane (2) for optical imaging to form a plurality of two-dimensional sections (4); and A depth-of-field scanning mechanism (5) respectively connected to the imaging element (1) and / or the imaging lens group (3) for controlling the spatial position change of the imaging element (1) and / or the imaging lens group (3) to perform volume scanning on the two-dimensional section (4); wherein, The depth-of-field scanning mechanism (5) controls the amplitude of the volume scanning in the depth-of-field direction to be L1 mm, and the depth of distribution of the plurality of equivalent image planes (2) in the depth-of-field direction is L2 mm, satisfying L1 < L2; The mass Mg of the imaging element (1) and the number n of the equivalent image planes (2) satisfy: .

2. The Bragg periodic scanning holographic imager according to claim 1, characterized in that: The scanning frequency or equivalent frequency of the depth of focus scanning mechanism (5) is greater than Hz.

3. The Bragg periodic scanning holographic imager according to claim 1, characterized in that: The depth-of-field scanning mechanism (5) performs volume scanning on the two-dimensional section (4) by changing the spatial position between the equivalent image plane (2) and the imaging lens group (3) and / or the effective focal length of the imaging lens group (3).

4. The Bragg periodic scanning holographic imager according to claim 3, wherein: The depth-of-field scanning mechanism (5) performs volume scanning on the two-dimensional section (4) by changing the relative position and / or the overall position of the optical elements in the imaging lens group (3).

5. A Bragg periodic scanning holographic imager according to claim 3, characterized in that: The imaging lens group (3) at least includes a liquid zoom lens or a flexible zoom lens.

6. The blazed periodic scanning holographic imager according to claim 1, wherein: The imaging element (1) is a projection display element or a photographing photosensitive element.

7. The Bragg periodic scanning holographic imager according to claim 1, wherein: A plurality of projection display chips and photographing photosensitive chips are arranged inside the imaging element (1) to achieve the dual functions of projection and photographing.

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