Holographic display system with folded optical path geometry

Abstract

The invention relates to the field of 3D display, and discloses a folded optical path geometric holographic display system, comprising at least one projector, a transmission-type geometric holographic screen, a supporting structure, a controller and at least one optical path folding mirror group; the optical path folding mirror group comprises at least one plane mirror with a reflection function, which is used to change the propagation path of the light projected by the projector; the folded optical path geometric holographic display system has n viewpoints, the average value of the diameter of the light-transmitting part of the outermost lens of the projector is D decimeters, and the average value of the projection light source power of the projector is P watts, which satisfies: the invention introduces an optical path folding mirror group capable of changing the propagation path of the light projected by the projector, flexibly transforms and folds the optical path, can reasonably utilize space, reduce the space occupancy of the entire display system, and effectively improve the flexibility of the display system layout.

Description

Technical Field

[0001] The present invention relates to the field of 3D display, and in particular to a folded light path geometric holographic display system. Background Art

[0002] Compared with traditional 2D display technology, 3D display technology can provide depth information, thereby displaying more visual information and making the displayed image more realistic. Therefore, 3D display technology is a very popular technology in academic research. Among them, the 3D display solution based on holographic technology can, in principle, restore the light field distribution of the real physical world, thereby completely restoring all the optical characteristics of the 3D scene. Traditional holographic display technology uses the wave characteristics of light to simultaneously record the light intensity information and phase information of the scene, thereby achieving the recording of the light intensity, color and depth of field of the scene. However, this method requires coherent light for shooting and display, and the optical path setting during the shooting and display process is very harsh. Slight disturbances in the environment will cause shooting failures, so it has never been truly applied in life.

[0003] At present, mainstream 3D display solutions (such as 3D movies in theaters) are based on pseudo 3D display images of parallax image pairs (stereoscopic image pairs), which cannot display real 3D images. The physical focal depth of the display screen is fixed, and it is impossible to display scenes with different focal depths. Although many 3D display technologies have been proposed, there is no technology that can truly display large-scale, stable, and high-quality 3D images.

[0004] Patent application number 201910875975.1 discloses a new holographic display solution, such as Figure 1 As shown, it includes a holographic projector 1, a projection screen 2, an interactive response unit 3, a processor 4 and a motion actuator 5. The projection data information is sent to the holographic projector 1 by the processor 4 to control the projection picture and picture depth of the holographic projector 1, and the motion actuator 5 is controlled according to the positioning information of the human eye and the user interactive action information obtained by the received interactive response unit 3 to adjust the position of the holographic projector 1 relative to the projection screen 2, so that the user can watch the 3D picture normally. However, at this stage, due to the lack of 3D film sources that can be used, its display advantages are difficult to play. Moreover, the structural limitations of the display system are relatively large. In many application scenarios, it is impossible to provide it with sufficient system layout space, and the system is complex and costly.

[0005] Meanwhile, the optical parameter settings of the above-mentioned display system need to be carefully designed to ensure the ideal display effect and the reliability of the display system. Otherwise, the display system may fail to achieve the ideal display effect or fail to ensure reliability due to inappropriate display parameters. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the deficiencies of the above-mentioned prior art, a folded optical path geometric holographic display system is provided, which introduces an optical path folding mirror group that can change the propagation path of the light projected by the projector, and flexibly transforms and folds the optical path, thereby being able to reasonably utilize space, thereby reducing the space occupancy of the entire display system, and can very effectively improve the flexibility of the display system layout; at the same time, an optimized design parameter configuration is provided to achieve the purpose of taking into account both display effect and system reliability.

[0007] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0008] Folded optical path geometry holographic display system, comprising:

[0009] at least one projector, for projecting picture information in space;

[0010] The transmissive geometric holographic screen is a screen that converges the image points on one side of the transmissive geometric holographic screen to form conjugate image points on the other side;

[0011] A supporting structure, which is matched with the projector and the transmissive geometric holographic screen respectively, and provides physical structural support for the two;

[0012] The controller is electrically connected to the projector, and further includes at least one optical path folding mirror group, which is arranged on one side or both sides of the transmission type geometric holographic screen and respectively connected to the supporting structure, wherein the optical path folding mirror group includes at least one plane mirror with a reflection function, which is used to change the propagation path of the light projected by the projector;

[0013] The number of viewpoints of the folded optical path geometry holographic display system is n, the average value of the diameter of the light-transmitting part of the outermost lens of the projector is D decimeters, and the average value of the projection light source power of the projector is P watts, which satisfies:

[0014]

[0015] Furthermore, the average value of the display luminous flux of the projector is L lumens, which satisfies the following relationship with the number of viewpoints n of the folded optical path geometry holographic display system:

[0016] n 1.27 ·L≤24000.

[0017] Furthermore, the viewpoint number n of the folded optical path geometry holographic display system satisfies the following relationship:

[0018]

[0019] Furthermore, the projector is a common projection device capable of projecting a two-dimensional image or a holographic projection device capable of projecting a three-dimensional image.

[0020] Furthermore, the projection focal depth of the projector is adjustable within a space of 0.1 m and beyond 0.1 m from the outermost lens of the projector lens.

[0021] Furthermore, the transmissive geometric holographic screen adopts a flexible holographic screen.

[0022] Furthermore, the supporting structure is a structure that can be deformed or moved and is electrically connected to a controller. The controller can control the deformation or movement of the supporting structure, thereby realizing relative movement and / or overall movement among the projector, the transmissive geometric holographic screen and the optical path folding mirror group, so that the visible window of the system always covers the user's eyes.

[0023] Furthermore, it also includes an interactive action capture unit electrically connected to the controller, which is used to identify the user's interactive actions and send the user's interactive action information to the controller. The controller adjusts the display screen content according to the user interactive action information obtained by the interactive action capture unit to realize the interactive action between the user and the screen.

[0024] Furthermore, it also includes a human eye tracking unit electrically connected to the controller, wherein the human eye tracking unit is used to track the position of the human eye and send the positioning information of the human eye to the controller. The controller controls the supporting structure to make corresponding action response according to the human eye positioning information obtained by the human eye tracking unit, so as to adjust the relative position and / or the overall spatial position of the projector and the transmissive geometric holographic screen, so that the user's eyes are always in the visible space of the system.

[0025] Furthermore, the visual space is a space that satisfies the following relationship in an optical conjugate coordinate system (X′, Y′, Z′) after optical transformation, in which the center of the outermost lens of each projector lens is taken as the origin, the outer normal of the lens center is taken as the Y-axis direction, the straight line passing through the origin and perpendicular to the horizontal plane is taken as the X-axis, and the straight line passing through the origin and perpendicular to the X-axis and the Y-axis is taken as the Z-axis:

[0026]

[0027] Where K is an expansion constant, the unit is decimeter, and the range of K is 0<K<0.08;

[0028] m is the conjugate deviation constant, and the range of m is 0≤m≤5.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] 1. By introducing an optical path folding mirror group that can change the propagation path of the projector's projected light, the optical path can be flexibly transformed and folded, so that the space can be reasonably utilized to reduce the space occupancy of the entire display system, and the flexibility of the display system layout can be effectively improved;

[0031] 2. The projector uses ordinary projection equipment that can project two-dimensional images, which can greatly reduce costs and improve practicality. Ordinary projection equipment can project a two-dimensional image on a focal plane in the space. The controller adjusts the focal depth of the projected image to achieve image display with depth of field information, presenting a more realistic 3D effect, overcoming the limitation of 3D film source shortage and reducing costs;

[0032] 3. Reasonable optical parameter settings can effectively improve the display effect and reliability of the holographic display system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 is a schematic diagram of an existing holographic display system.

[0035] Figure 2 is a schematic diagram of a system of the present invention including a projector 6 and an optical path folding lens group 10,

[0036] Figure 3 is Figure 2 Based on the above, a system diagram of an interactive motion capture unit 31 and a human eye tracking unit 32 is added;

[0037] Figure 4 is Figure 2 Based on the above, a system diagram of an optical path folding mirror group 10 is added on the same side.

[0038] Figure 5 The system diagram and the optical path diagram of the optical conversion are shown in which the optical path folding mirror groups 10 are respectively arranged on both sides of the transmission type geometric holographic screen 7.

[0039] Figure 6 Schematic diagram of several viewpoint configurations for off-screen display of holographic system;

[0040] Figure 7 A schematic diagram of the system configuration of multiple viewpoints of the present invention;

[0041] Figure 8This is a schematic diagram of the space 0.1m away from the outermost lens of the projection lens;

[0042] Fig. 9 It is a schematic diagram of the coordinate system (X′, Y′, Z′) where the ellipsoid visual space is located;

[0043] Fig.10 is a schematic diagram of the ellipsoidal visual space, i.e., the viewing window.

[0044] The reference numerals are as follows:

[0045] Holographic projector 1, projection screen 2, interactive response unit 3, processor 4, motion actuator 5, projector 6, transmission type geometric holographic screen 7, support structure 8, controller 9, optical path folding mirror group 10, interactive motion capture unit 31, human eye tracking unit 32. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below in conjunction with the accompanying drawings. The description in this part is only exemplary and explanatory and should not have any limiting effect on the protection scope of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] It should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, or are the orientation or positional relationship in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0049] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0050] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of 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.

[0051] like Figures 2 to 5 The present invention provides a folded optical path geometric holographic display system, comprising at least one projector 6, a transmissive geometric holographic screen 7, a support structure 8, a controller 9 and at least one optical path folding mirror group 10;

[0052] The projector 6 is used to project image information with depth in space. The present invention can use an ordinary projection device that can project a two-dimensional image to realize the projection of a two-dimensional image on a focal plane in the space, and then adjust the depth of field and image content of the two-dimensional image through the controller 9. Usually, the 3D film sources in theaters are in the form of stereoscopic image pairs, which show the 3D effect through binocular parallax, but the actual image focal depth is fixed in one position, so it will cause visual fatigue. Since the projection and focal depth of the system of the present invention are adjustable, the equivalent focal depth of the image can be moved to a reasonable position, thereby avoiding the problem of the 3D focal depth being different from the actual focal depth, and presenting a more realistic 3D effect. Compared with using a holographic projector as the projector 6, this method can effectively reduce costs. Specifically, the above-mentioned ordinary projection equipment can use a common ordinary projector;

[0053] Alternatively, a holographic projector is directly used as the projector 6 to project a 3D image in the space; or a projection device capable of realizing the display of a three-dimensional image (or a group of two-dimensional images distributed at different focal depths in the space) can be used to replace the above-mentioned holographic projector. For example, the ordinary projection device can be further optically designed so that it can realize 3D display on the basis of a single projector. Reference can be made to a fully solid-state holographic projector with application number 202010029144.5, which realizes the technical solution of realizing the display of a three-dimensional image by adding some optical elements inside the projector for optical design, which is not specifically limited here;

[0054] The transmissive geometric holographic screen 7 is a screen that converges the image points on one side of the transmissive geometric holographic screen 7 to the other side thereof to form a conjugate image point. Its position corresponds to the projector 6 and the optical path folding lens group 10. It is preferred to use a flexible holographic screen, which can be made into a scroll screen or a folding screen, so that the system as a whole is more compact and portable. Of course, a hard screen can also be used for appropriate occasions.

[0055] When it is necessary to display 2D images, the transmissive geometric holographic screen 7 can be replaced by an ordinary projection screen, such as an ordinary rear projection screen;

[0056] The support structure 8 is matched with the projector 6, the transmission type geometric holographic screen 7 and the optical path folding mirror group 10 respectively, and provides physical structural support for the three respectively. Specifically, the support structure 8 can be made into a support frame with a fixed structure. In this case, the display system of the present invention is fixed as a whole, and the user needs to be in a fixed position to observe the picture;

[0057] The optical path folding mirror group 10 is supported by the supporting structure 8, and includes at least one plane mirror with a reflective function, which is used to change the propagation path of the light projected by the projector 6, and is specifically arranged on one side of the transmission type geometric holographic screen 7, or when there are multiple optical path folding mirror groups 10, they are arranged on one side of the transmission type geometric holographic screen 7 or on both sides of the transmission type geometric holographic screen 7, which is determined specifically according to the spatial form of the applied scene;

[0058] The controller 9 is electrically connected to the projector 6, and the projector 6 can adjust the depth of field and the content of the projected image according to the control signal of the controller 9;

[0059] In order to increase the flexibility of the display system, we can also set the support structure 8 to a movable or deformable structure, electrically connect the support structure 8 to the controller 9, and the support structure 8 makes corresponding response actions according to the control information of the controller 9, so as to realize the relative movement and / or overall movement among the projector 6, the transmission-type geometric holographic screen 7 and the optical path folding mirror group 10, so that the visible window of the system always covers the user's eyes, so that the user can watch the picture normally in different directions. It should be noted that the support structure 8 is a general existing technology, and technicians in this field can design it according to the spatial conditions of actual application. For example, using some hinge structures and structures similar to umbrella shafts can easily design a deformable structure, which is not specifically limited here;

[0060] like Figure 3As a preferred solution, the holographic display system of the present invention further includes an interactive action capture unit 31 electrically connected to the controller 9. The interactive action capture unit 31 is used to identify the user's interactive action and send the user's interactive action information to the controller 9. The controller 9 adjusts the display screen content according to the user's interactive action information received by the interactive action capture unit 31 to realize the interactive action between the user and the screen. Specifically, the camera can be combined with machine vision technology to identify the user's gestures to obtain the user's interactive information, so as to control the movement of the support structure 8 to adjust the spatial position and posture of the projection device and / or the transmission type geometric holographic screen 7. The controller 9 can also adjust the display screen content in real time according to the user's interactive action information received by the interactive action capture unit 31 to realize the interactive action between the user and the screen, such as controlling the screen to translate according to the translation gesture signal, or controlling the zooming, zooming in, zooming out, touching, etc. of the screen according to other corresponding interactive actions;

[0061] The setting of the interactive motion capture unit 31 has positive significance for application scenarios such as wearable applications where the spatial position of the user relative to the display system is fixed;

[0062] In addition, for application scenarios in which the spatial position of the user relative to the display system changes in real time, it is necessary to set up a human eye tracking unit 32 electrically connected to the controller 9. The human eye tracking unit 32 is used to track the position of the human eye and send the positioning information of the human eye to the controller 9. The controller 9 controls the support structure 8 to make corresponding action responses according to the human eye positioning information obtained by the human eye tracking unit 32, so as to adjust the relative position and / or the overall spatial position of the projector 6 and the transmissive geometric holographic screen 7, so that the user's eyes are always in the visible space of the system. In this way, the user's eyes can always receive the projection information and watch the picture normally even when the user is in motion.

[0063] In practical applications, the human eye tracking unit 32 and the interactive motion capturing unit 31 can be integrated into the same device, such as using a machine vision camera device.

[0064] When a common projector is used as the projector 6, the controller 9 sends the picture and the average focal depth information of the picture to the projector, and the projector adjusts the projection focal depth by itself, so that the projector can project the picture to a specific focal depth position for human eyes to watch.

[0065] It should be noted that ordinary projectors generally have an autofocus function. When the projector is turned on, the projector will measure the distance between the screen and the projector based on the built-in distance sensor, and then drive the lens to adjust to a suitable position so that the projection focal depth coincides with the screen. In the system of the present invention, the built-in distance sensor can also be removed, so that the controller 9 directly sends the focal depth data to the projector to achieve control of the projection focal depth. The specific implementation method is the existing mature hardware communication technology, which will not be repeated here.

[0066] The present invention is described by taking a projector 6 as an example:

[0067] like Figure 2 The system is equipped with an optical path folding mirror group 10 located on the same side as the projector 6. After the projection image of the projector 6 is optically transformed by the optical path folding mirror group 10 and the transmissive geometric holographic screen 7, an off-screen display image is formed on the other side of the transmissive geometric holographic screen 7, and the human eye can view it through the window shown in the figure;

[0068] like Figure 4 The system is equipped with two optical path folding mirror groups 10, both of which are located on the same side as the projector 6 relative to the transmissive geometric holographic screen 7. After the projection image of the projector 6 is optically transformed by the two optical path folding mirror groups 10 and the transmissive geometric holographic screen 7, an off-screen display image is formed on the other side of the transmissive geometric holographic screen 7, and the human eye can watch it through the window shown in the figure;

[0069] like Figure 5 The system is also equipped with two optical path folding mirror groups 10, but they are respectively arranged on both sides of the transmissive geometric holographic screen 7. The projection image of the projector 6 is optically transformed by the two optical path folding mirror groups 10 and the transmissive geometric holographic screen 7 (such as Figure 6 ), an off-screen display image is formed on the other side of the transmissive geometric holographic screen 7, and the human eye can see it through the window as shown in the figure;

[0070] It should be noted that the optical transformation principle of the projection image of the projector 6 by the optical path folding mirror group 10 and the transmission type geometric holographic screen 7 can be referred to Figure 5 When the number of the optical path folding mirror groups 10 is greater, any arrangement and combination thereof, as long as the projection image of the projector 6 can be optically transformed to form an off-screen display image at the optical conjugate position, falls within the protection scope of the present invention.

[0071] The above is only an example to illustrate the present invention, and is not intended to limit the present invention. The same is applicable when there are multiple projectors 6 .

[0072] The folded optical path geometry holographic display system of the present invention has a very special feature compared to the traditional display system. It cannot be viewed by a large number of users at the same time like the traditional 2D display device. For the convenience of description, the concept of viewpoint is introduced here:

[0073] If the display system can provide a viewing window for one eye, then the system has one viewpoint. For a binocular display system, it can be viewed by two eyes at the same time, so the number of viewpoints is 2. When the display system can be viewed by n eyes at the same time, the number of viewpoints is n. In actual design, it is also necessary to reasonably set the system structure while considering practicality.

[0074] like Figure 6 As shown, in case a, corresponding to the use of a large-aperture projector, the outermost lens of the projector can cover the user's two eyes with respect to the optical conjugate area (also the mirror-symmetric area, which can be called the viewing window) of the transmissive geometric holographic screen 7. At this time, although the area between the two eyes can also view images in principle, it is impossible to use it under practical conditions. It can only be viewed by two eyes at the same time, so this situation is equivalent to having two viewpoints;

[0075] In cases b to d, two small-aperture projectors are used, and the projection lenses of the two projectors form two separate sub-areas relative to the optical conjugate area of ​​the transmissive geometric holographic screen 7. When the spacing between the two sub-areas just matches the spacing of human eyes, two eyes can watch at the same time (case b), so there are two viewpoints;

[0076] When the distance between the two sub-areas is smaller than the distance between human eyes (case c) or larger than the distance between human eyes (case d), only one of the two eyes can see the image, and therefore there is only one viewpoint.

[0077] like Figure 7 When the number of projectors increases, the number of viewpoints of the system will increase accordingly. The specific number depends on the specific circumstances a to d. The number of viewpoints of the display system is n, which is related to the size and number of the lenses of the projectors used.

[0078] Similarly, when designing a multi-user system, it is even more necessary to consider the spatial position relationship between users in the usage scenario, and reasonably design the spatial distribution between each window to avoid the situation where the actual available viewpoint of the system is smaller than the designed viewpoint. An effective design strategy is to reasonably design the support structure 8 so that it has a structural adjustment function, such as being able to adjust the distance or spatial position between the two projectors, so that when in use, the geometric shape of the support structure 8 can be flexibly adjusted according to the user's pupil distance and the application site to adapt to actual needs.

[0079] It should be noted that when the projection system is switched downward to the 2D projection mode (for example, by adjusting the projection focal plane of the projector to project a 2D image directly on the transmissive geometric holographic screen 7, or by using an ordinary projection receiving screen to replace or place it in front of or behind the front surface of the transmissive geometric holographic screen 7 to receive and display the 2D projection image), the image focal plane coincides with the screen, and the number of viewpoints will increase significantly. However, these viewpoints have great viewing limitations and can only see the image on the screen, and the off-screen images output by the display system cannot be viewed. Therefore, they cannot be counted into the actual number of viewpoints. The actual effective viewpoints should be those that can view the images in all modes of the system.

[0080] For traditional 2D display devices, such as televisions, projectors, computers, etc., the number of viewpoints is very large and can be viewed by many users simultaneously. This is because the light emitted by their light sources has a high divergence and no directivity. Therefore, they also have relatively high requirements for brightness. However, for the holographic display system of the present invention, the number of viewpoints is relatively small. The light emitted by its display device (such as a holographic projector or an ordinary projector) will be very efficiently concentrated at the viewing window position and received by the human eye. Therefore, if the light intensity is too strong, it is easy to cause dizziness, the image is not clear, and even cause harm to the human eye. At the same time, too high a light flux often requires the light source (such as the bulb or LED lamp inside the projector) to operate at a high power, and the service life of the light source will be significantly reduced when it operates at a high power for a long time. Therefore, the light flux cannot be designed too high. However, as the number of viewpoints increases, the total light flux of the display system also needs to be increased to ensure that each viewpoint can provide a clear image. Due to the complexity of the optical path of the display system of the present invention, the relationship between the viewpoint and the light flux is not a simple linear relationship.

[0081] In the folded optical path geometric holographic display system of the present invention, the number of viewpoints is n, the average diameter of the light-transmitting part of the outermost lens of the projector 6 is D decimeters (dm), and the average display light flux of the projector 6 is L lumens (lm). The product of the display light flux and the viewpoint is n 1.27 ·L. In summary, combined with the actual test results, the product of the display light flux and the viewpoint satisfies: n 1.27 ·L ≤ 24000 can ensure better display effects and system reliability.

[0082] Among them, the measurement method of the display light flux L (lm) of the projector 6 can refer to the test method of ANSI lumens:

[0083] 1) Set the distance between the projector and the screen in the display system to: 2.4 meters;

[0084] 2) The screen is 60 inches;

[0085] 3) Use an illuminance meter to measure the illuminance at each of the nine intersection points of the "field" shape on the screen, and calculate the average illuminance of the 9 points;

[0086] 4) The average illumination multiplied by the projection screen area is the ANSI lumen, which is the display luminous flux mentioned in the present invention.

[0087] For different screens, the test value of L may vary greatly. In actual testing, it is preferred to display a full white screen for testing, that is, each pixel is displayed as white.

[0088] When the illumination area of ​​the projector cannot be well matched with the screen, the illumination test is performed according to the actual illumination area. It is preferred to evenly select 8 points in the light band about 10cm to 30cm away from the outer boundary of the illumination area and 1 point in the illumination area no more than 20cm away from the center of the screen, for a total of 9 points for illumination test. Then multiply the average of the 9 illumination values ​​by the actual area of ​​the illumination area to obtain the displayed luminous flux value.

[0089] For application cases that only include one projector 6, the display luminous flux can be tested in the above manner (the display luminous flux of a single projector is the same as the average display luminous flux value). When multiple projectors are used, the luminous flux of each projection unit can be tested separately and the average value can be taken as the display luminous flux value.

[0090] In addition, in actual tests, different design structures (such as differences in sealing and heat dissipation) will also have a more obvious impact on the life of the system. Therefore, different design structures in the actual test process may cause certain fluctuations in the measured data, but the overall trend will not change, and the optimal value of the display configuration parameters will not change.

[0091] The present invention will be further described below with examples:

[0092] It should be noted that in the display systems of the following embodiments, the projector 6 is a common projector, the number of the optical path folding mirror group 10 is one, and it is arranged on the same side of the transmissive geometric holographic screen 7 as the projector 6;

[0093] Embodiment 1: A projector with a lens diameter of 0.5 dm is used as the projector 6, and the number of viewpoints n=1, which can be viewed by a single household using a single eye;

[0094] Usually the number of user eyes is even, and the number of viewpoints n is set to an even number:

[0095] Embodiments 2 to 24: Using one projector with a lens diameter greater than 6.5 dm or two projectors with lens diameters less than 6.5 dm as the projector 6, the number of viewpoints n = 2, which can be viewed by both eyes of a single household;

[0096] Embodiment 25: Four projectors with a lens diameter of 0.4 dm are used as projectors 6, and the number of system viewpoints n=4, which can be used for two users to watch at the same time;

[0097] Embodiment 26: Six projectors with lens diameters of 0.3 dm are used as projectors 6, and the number of viewpoints n=6, so that a family of three can watch at the same time;

[0098] Example 27: Eight projectors with a lens diameter of 0.2 dm are used as projectors 6, and a family of four watches at the same time;

[0099] Comparative Example 1: A projector with a lens diameter of 8 dm is used as the projector 6 for viewing by both eyes of a single household, as shown in the following table:

[0100]

[0101] The data of Examples 1 to 27 show that: the display luminous flux viewpoint product n 1.27 When L≤24000, the display effect is good, and the user rating is above 80 points. The display luminous flux viewpoint product n in Example 1 is 1.27 ·L is 31351, the user rating is low, the picture is dazzling, and the actual display effect is poor.

[0102] In actual use, in addition to considering the design relationship between the number of viewpoints n and the luminous flux L, the projector aperture size and the luminous flux need to be matched. When the projector aperture is large, the visual utilization rate of the display light will be low, and many lights can only reach areas outside the human eye. Therefore, the luminous flux needs to be appropriately increased. According to the application of the above embodiments 1 to 27, the actual application can refer to the following expression for design:

[0103]

[0104] Based on the influence of light source power on the display effect and reliability of the system. When the internal light source of the projector works in high-power mode, its lifespan tends to drop significantly, so it is best to work in low-power mode. However, when there are a large number of viewpoints or when the aperture of a single projector is large, the visual utilization rate of the display light will be low, and many rays can only reach areas outside the human eye. Therefore, it is necessary to increase the power of the light source appropriately to increase the luminous flux. The average power of the projector projection light source included in projector 6 is P watts (W). Tests have found that when the following relationship is met, the system can operate under a better condition:

[0105]

[0106] The measurement of the light source power P of the projection device can directly test the voltage across the light source and the current passing through the light source under normal working conditions, and then multiply them to obtain the power value.

[0107] On the basis of Examples 1 to 27, the light source power P (W) is introduced for illustration, as shown in the following table:

[0108]

[0109] Data shows: Power View Product When the display effect is good, the user rating is above 80 points, while the power viewpoint product in Example 1 The user rating is 679, the picture is glaring, and the actual display effect is poor. In addition, the light source power is less than 400W, which can generally meet the 5-year design life.

[0110] The common projector used in the above implementation can also be replaced by a holographic projector or other projection equipment capable of realizing three-dimensional image display. At the same time, the above design formulas involving the number of viewpoints, light source power and display luminous flux are also applicable to the holographic projector.

[0111] In addition, it was found in actual tests that Examples 1 to 27 can still work normally after 3000 hours in the accelerated test in the high temperature and high humidity environment (85°C, relative humidity 85%), while the light source of Comparative Example 1 was damaged and could not emit light at 3000 hours, indicating that unreasonable design parameters will greatly reduce the service life. The above test is commonly known as the double 85 aging test, and the 3000-hour accelerated aging test is equivalent to the minimum service life standard of 5 years under actual working conditions.

[0112] The principle of the display system described in the present invention can refer to the patent application number 201910875975.1. Here is a brief introduction: the projector 6 can project images at different depths in space, that is, it can provide additional depth of field information for the projected image, but the images projected by the projector 6 are all divergent light and cannot be directly viewed by the human eye. This is why conventional projection systems must use a receiving screen.

[0113] The optical path conversion effect of the transmissive geometric holographic screen 7 can make the divergent light projected by the projector 6 converge again to the optical conjugate position of the projector 6 relative to the transmissive geometric holographic screen 7, that is, its mirror image position, thereby forming convergent light that can be directly viewed by the human eye.

[0114] Therefore, although the holographic display system of the present invention uses a transmissive geometric holographic screen 7, its function is completely different from that of the receiving screen of the traditional projection display system. The receiving screen of the traditional projection system is used to randomly scatter the light for users to watch. The transmissive geometric holographic screen 7 acts more like a special optical element, which can perform a specific optical conversion on the light, and re-converge the light emitted by the light spot on one side of the screen to a very small area near the mirror position of the light spot relative to the screen, thereby forming a converging real image point suspended in the air. This unique imaging feature allows it to perform imaging at different depths in space (off-screen imaging), realizing true 3D display.

[0115] In the holographic display system of the present invention, the projector 6 projects an image, which is reflected by the optical path folding mirror group 10 and optically transformed by the transmission type geometric holographic screen 7 to form an off-screen display in space.

[0116] From the analysis of the display principle of the present invention, it can be found that the image seen by the user when using the projector 6 is completely consistent with the image projected by the projector 6. The distance between the image projected by the projector 6 and the outermost lens is the distance between the image seen by the user and the eye. In life, the visual distance of the human eye is generally 25cm, and the nearest object is generally 10cm away. Therefore, when selecting the projector 6, it is preferred that the projection focal depth can be within a space greater than 0.1m from the outer surface of the outermost lens of the projection lens (such as Figure 8 ) is used to adjust the projector (ordinary projector or holographic projector).

[0117] When the user is static, as long as the system structure is adjusted so that the user's eyes are covered by the window, the user can watch the picture normally. However, if the user is in motion, it is easy for the eyes to leave the window and cannot watch the picture normally. Therefore, for application scenarios where the user cannot be completely static, it is very important to increase the user's eye positioning tracking and then adjust the spatial position of the window in real time so that it always covers the user's eyes. However, in actual scenarios, the parameters of the components of the display system are different, and it is difficult to find a tracking method that is suitable for all systems. In principle, if the user's eye movement trajectory can be located very accurately, then the relative position and overall spatial position between the projector and the transmissive geometric holographic screen are adjusted to drive the window to accurately track the user's eye movement trajectory. The most ideal solution is. However, it is very difficult to completely and accurately track the user's eyes and accurately control the window position. Even if it can be achieved, it will cost a relatively large price, and it is not very practical.

[0118] In fact, since the window itself has a certain size, the human eye can see the picture as long as it is within the window, so when the user moves, it is not necessary to track the movement trajectory of the user's eyes completely accurately. It is sufficient to track the user's eyes roughly to ensure that they are within the window. Even if they are slightly offset from the window, but the pupil intersects with the window, the picture can be viewed normally.

[0119] The above discussion is mainly about the situation where the user moves left, right, up, or down relative to the screen. In addition, when the user moves forward or backward, if he does not deviate too much from the center of the window, he can also watch the screen normally. In summary, the tracking of the user's eyes does not need to be particularly precise, as long as it is guaranteed within a certain accuracy, it can meet the usage requirements. Fig.10 There will be an intersecting diamond-shaped area for the light above and below the screen. In principle, the picture can be observed as long as the supporting structure is adjusted in real time so that the user's eyes are always in the above-mentioned diamond-shaped visual space. However, it is easier to lose tracking near the corners of the diamond. Therefore, a relatively small ellipsoidal visual area is further limited inside the prismatic area to reduce the probability of tracking loss.

[0120] The ellipsoid region is described below. Fig. 9 The ellipsoidal visual space is the visual space that takes the center of the outermost lens of each projector 6 lens as the origin, the outer normal of the lens center as the Y-axis direction, the straight line passing through the origin and perpendicular to the horizontal plane as the X-axis, and the straight line passing through the origin and perpendicular to the X-axis and Y-axis as the Z-axis. After optical transformation, the coordinate system (X, Y, Z) satisfies the following relationship in the optical conjugate coordinate system (X', Y', Z'):

[0121]

[0122] Where K is an expansion constant, the unit is dm, and the range of K is 0<K<0.08;

[0123] m is the conjugate deviation constant, and the range of m is 0≤m≤5.

[0124] The above coordinate system (X′, Y′, Z′) is the conjugate image of the coordinate system (X, Y, Z) after the optical system transformation. The above expression is a space surrounded by an ellipsoid, where the value of m affects the length of the ellipsoid in the y-axis direction. Fig.10 It can be seen that the visual space has a certain extension in the Y' axis direction. The actual test found that the visual space has a certain extension length in the Y' axis direction of about 6 times the lens diameter D. A clear picture can be seen within this range. However, considering the actual tracking effect, it is relatively easy to achieve a better display effect within the range of less than 5 times the lens diameter in the Y' axis direction. In addition, the actual test found that:

[0125] When m is 5, the entire display area of ​​the picture can be clearly seen. Only in the local boundary area, the picture clarity is slightly worse, but the details can still be clearly distinguished.

[0126] When m is 3, the entire display area of ​​the picture can be clearly seen, even in the boundary area, the picture is relatively clear, and the tracking stability is also very good;

[0127] When m is 2, the entire display range of the picture is complete, the display details are very clear, the tracking stability is relatively good, and it is only occasionally lost, which is suitable for desktop office scenes;

[0128] When m is 1, the entire display range of the picture is complete, the display details are very clear, the tracking stability is slightly poor, and the tracking loss frequency increases, which is suitable for movie viewing and entertainment application scenarios;

[0129] K and D determine the cross-section of the visible space in the plane perpendicular to the Y′ axis. In principle, the image can be seen within the diameter range of the projection lens. In fact, as long as the optical conjugate area of ​​the human eye intersects with the projection lens, the image can be seen even if the person is not completely within the optical conjugate area of ​​the projection lens. Therefore, an expansion constant K is introduced, and its value depends on the diameter of the human eye. Usually, the maximum diameter of the human pupil is 0.08dm, so 0.08dm is taken here as the expansion constant.

[0130] Although, mathematically m cannot be 0, taking it as 0 here has physical significance, that is, the point on the plane where Y′ is equal to 0.

[0131] When using multiple projectors (ordinary projectors or holographic projectors), the present invention can select completely the same model, or can select different models according to the requirements of actual application scenarios.

[0132] The display system of the present invention can avoid visual fatigue caused by users watching a fixed-depth image for a long time due to the adjustable depth of focus, thereby avoiding the occurrence of myopia and improving the visual acuity level.

[0133] The present invention can be used for fixed display, such as office, home audio and video, car display, etc., and can also be used for small mobile display and head-mounted display. The quality of the projector 6 in different application scenarios is selected as follows:

[0134] Desktop application: Projection equipment with a mass less than 5kg is preferred;

[0135] Mobile terminal: preferably a projection device with a mass less than 300g;

[0136] Wearable applications: Projection equipment with a mass less than 100g is preferred.

[0137] When the present invention is implemented, some optical elements such as anti-reflection films, light-absorbing films, filters, etc. can be appropriately added to further improve the effect of the system.

[0138] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. Folded optical path geometry holographic display system, including: At least one projector (6) for projecting picture information in space; The transmissive geometric holographic screen (7) is a screen that converges image points on one side of the transmissive geometric holographic screen (7) to form conjugate image points on the other side thereof; A support structure (8) is matched with the projector (6) and the transmission type geometric holographic screen (7) respectively to provide physical structural support for the two; A controller (9) is electrically connected to the projector (6), characterized in that it also includes at least one light path folding mirror group (10) which is arranged on one side or both sides of the transmission type geometric holographic screen (7) and is respectively connected to the support structure (8), wherein the light path folding mirror group (10) includes at least one plane mirror with a reflection function, which is used to change the propagation path of the light projected by the projector (6); The number of viewpoints of the folded optical path geometric holographic display system is n, the average value of the diameter of the light-transmitting portion of the outermost lens of the projector (6) is D decimeters, and the average value of the projection light source power of the projector (6) is P watts, satisfying:

2. The folded light path geometry holographic display system according to claim 1, characterized in that: The average value of the display luminous flux of the projector (6) is L lumens, which satisfies the following relationship with the number of viewpoints n of the folded optical path geometric holographic display system: n 1.27 ·L≤24000。 3. The folded light path geometry holographic display system according to claim 2, characterized in that: The number of viewpoints n of the folded optical path geometric holographic display system, the average value L lumen of the display luminous flux of the projector (6), and the average value D decimeter of the diameter of the light-transmitting part of the outermost lens of the projector (6) satisfy the following relationship:

4. The folded optical path geometry holographic display system according to any one of claims 1 to 3, characterized in that: The projector (6) is a common projection device capable of projecting a two-dimensional image, or a holographic projection device capable of projecting a three-dimensional image or a group of two-dimensional images distributed at different depths in space.

5. The folded light path geometry holographic display system according to claim 4, characterized in that: The projection focal depth of the projector (6) is adjustable within a space 0.1 m away from the outermost lens of the projector (6) lens and a space beyond 0.1 m.

6. The folded light path geometry holographic display system according to claim 1, characterized in that: The transmission type geometric holographic screen (7) adopts a flexible holographic screen.

7. The folded light path geometry holographic display system according to claim 1, characterized in that: The support structure (8) is a structure that can be deformed or moved and is electrically connected to a controller (9). The controller (9) can control the deformation or movement of the support structure (8), thereby achieving relative movement and / or overall movement among the projector (6), the transmission-type geometric holographic screen (7) and the optical path folding mirror group (10).

8. The folded light path geometry holographic display system according to claim 7, characterized in that: It also includes an interactive action capture unit (31) electrically connected to the controller (9), the interactive action capture unit (31) being used to identify the user's interactive actions and send the user's interactive action information to the controller (9), and the controller (9) adjusting the display screen content according to the user's interactive action information received by the interactive action capture unit (31).

9. The folded light path geometry holographic display system according to claim 8, characterized in that: The system also includes an eye tracking unit (32) electrically connected to the controller (9), wherein the eye tracking unit (32) is used to track the position of the eye and send the positioning information of the eye to the controller (9). The controller (9) controls the support structure (8) to make a corresponding action response according to the eye positioning information received from the eye tracking unit (32), so as to adjust the relative position and / or the overall spatial position of the projector (6) and the transmission type geometric holographic screen (7), so that the user's eyes are always within the visible space of the system.

10. The folded light path geometry holographic display system according to claim 9, characterized in that: The visual space is a space that satisfies the following relationship in an optical conjugate coordinate system (X′, Y′, Z′) after optical transformation, in which the center of the outermost lens of each projector (6) lens is taken as the origin, the outer normal of the lens center is taken as the Y-axis direction, the straight line passing through the origin and perpendicular to the horizontal plane is taken as the X-axis, and the straight line passing through the origin and perpendicular to the X-axis and the Y-axis is taken as the Z-axis: Where K is an expansion constant, the unit is decimeter, and the range of K is 0<K<0.08; m is the conjugate deviation constant, and the range of m is 0≤m≤5.

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