WO2017215603A1

WO2017215603A1 - Optical system

Info

Publication number: WO2017215603A1
Application number: PCT/CN2017/088208
Authority: WO
Inventors: 陈政锡; 贾甲; 初大平; 姚峻
Original assignee: 华为技术有限公司; 剑桥实业有限公司
Priority date: 2016-06-15
Filing date: 2017-06-14
Publication date: 2017-12-21
Also published as: CN107515473A; CN107515473B

Abstract

An optical system (500). The optical system (500) comprises: N gratings, wherein the N gratings intersect at the same point, and are arranged on the same plane by taking the same point as the centre, and the N gratings are not overlapped with one another, where N≥2; and a driving apparatus (520), wherein the driving apparatus (520) comprises a central rotation axis, and the central rotation axis perpendicularly intersects with a grating group (510) at the same point and is used for driving the grating group (510) to rotate in the same plane by taking the central rotation axis as the centre, such that an incident light beam can irradiate on the N gratings in turn, and at least one light beam scanning path is formed on a light emergent side of the grating group (510). When an incident light beam enters, from one grating, an adjacent grating, an emergent light beam returns to a starting position of a light beam scanning path therein and scans the scanning path so that a scanning effect is obtained by means of the rotation of a grating group without flyback, thereby avoiding the problem of flyback.

Description

Optical system

The present application claims priority to Chinese Patent Application No. 20161042362, filed on Jun.

Technical field

The present application relates to the field of optics, and in particular to an optical system.

Background technique

In an optical system, it is often necessary to display the content that needs to be presented by scanning. For example, the output beam of the optical system can be projected into the scanning area (which can also be referred to as a scanning path) by scanning.

For example, when displaying a 3D holographic image, the high-bandwidth data of the 3D holographic image can be projected into the scanning path in the space by scanning to meet the requirements of the 3D holographic display. Specifically, when the 3D holographic image is displayed, the images of the respective angles of view of the 3D holographic image can be projected into the scanning path by scanning, and the observer can see different viewing angles of the 3D holographic image at different viewing angle positions on the scanning path.

However, in the conventional scanning method, for example, in the galvanometer mode scanning mode, the imaging information is first projected onto a mirror surface, and the imaging information is distributed within one scanning area by mirror rotation. However, when the scan reaches the boundary position, it must pass through the retrace, that is, move in the opposite direction to return to the starting position. Therefore, the existing galvanometer mode scanning method has a retrace problem, which affects the display effect.

Therefore, how to provide a scanning method that does not require retracement has become an urgent problem to be solved.

Summary of the invention

Embodiments of the present application provide an optical system that does not require retrace, thereby avoiding the retrace problem.

The first aspect provides an optical system comprising:

a grating group comprising N gratings, the N gratings intersecting at the same point, and are disposed in the same plane centered on the same point, and the N gratings do not overlap each other, N≥2;

a driving device, the driving device comprising a central rotating shaft intersecting the grating group perpendicularly at the same point for driving the grating group to rotate around the central rotating shaft in the same plane, so that the incident light beam can take turns Irradiating on the N gratings, at least one beam scanning path is formed on the light exiting side of the grating group.

Therefore, the embodiment of the present application drives the grating group to rotate around the central rotation axis in the same plane by driving the transposition, so that the incident light beam can be irradiated on the N gratings of the grating group in turn, and at least one beam scanning is formed on the light emitting side. The path is obtained by rotating the grating group to obtain a scanning effect when the incident beam is returned to the adjacent grating by one grating, and the outgoing beam is returned to the starting position of one of the beam scanning paths and scanned. There is no need to retrace, thus avoiding the retrace problem.

It should be understood that the driving device of the embodiment of the present application may be a motor or other driving device, as long as it can be used to drive the grating group to rotate around the central rotating axis. The embodiment of the present application is not limited thereto.

It should be understood that, in the embodiment of the present application, the incident light beam may be a light beam emitted by a point light source, or may be a light beam having a certain spot size. For example, the incident light beam may be a light beam having a rectangular spot size. For example, the rectangular light beam may be an image. The light beam, in particular, the light beam of the image may be a light beam of a different angle of view of the two-dimensional image or the holographic image, and the embodiment of the present application is not limited thereto.

The incident beam may be generated by other devices and input to the optical system; the input beam may also be generated by the optical system itself, and the embodiment of the present application is not limited thereto.

Correspondingly, when the input beam is a beam of an image, and the input beam is generated by the optical system itself, the optical system of the embodiment of the present application may further include:

a light source for generating a base beam;

A spatial light modulator for modulating image information onto the base beam to produce the incident beam, the image comprising a two-dimensional image or a three-dimensional image.

It should be understood that the spatial light modulator of the embodiment of the present application may be a digital micro-mirror display (DMD), or may be other devices, as long as the information of the image can be modulated onto the base beam to generate the incident. The light beam is sufficient, and the embodiment of the present application is not limited thereto.

It should be understood that the image may be a two-dimensional image or a three-dimensional image, for example, the image is a holographic image or a stereoscopic image, and the embodiment of the present application is not limited thereto.

For example, the image is a three-dimensional image, and the information of the image may include information of a plurality of perspective images of the image that are consecutively arranged in chronological order.

It should be understood that the N gratings in the embodiment of the present application may include two, three, four, five, six, seven, eight, etc. gratings, and the embodiments of the present application are not limited thereto.

It should be understood that the shape of a grating in the grating group of the embodiment of the present application may be a rectangle or a fan shape, and the embodiment of the present application is not limited thereto.

It should also be understood that N gratings can be disposed in the same plane around the same point. For example, N gratings can be stitched together without gaps, that is, the nth grating of the N gratings has two sides intersecting at the same point. And forming a nth angle θ _n , n takes all positive integers from 1 to N,

In other words, the sum of the N angles corresponding to the N gratings is 360°, wherein one grating corresponds to an angle, and the angle corresponding to each of the N gratings represents the grating of each grating connected to the same point. The angle at which the two sides are open.

In this case, when all of the gratings in the N gratings are fan-shaped and the radii are equal, the N gratings form a circle. That is, the sum of the radians of the N gratings is 360°.

Optionally, the N gratings may also be disposed in the same plane around the same point with a gap. For example, when all the gratings in the N gratings are fan-shaped and the radii are equal, the N gratings are spliced together to form 180. A fan shape of 270 or 320 degrees, etc.; a certain gap may be left between two adjacent gratings in the N gratings, and the embodiment of the present application is not limited thereto.

It should be understood that the angle θ _n formed by the different gratings in the N gratings in the embodiment of the present application may be the same or different, which is not limited by the embodiment of the present application. Preferably, for example, the angle θ _n formed by each grating is equal. For example, when the sum of the N angles corresponding to the N gratings is 360°, each grating forms an angle of 360°/N.

It should also be understood that the structures of the N gratings in the embodiments of the present application may be the same; the N gratings may also have various structures.

The following will be the same for the N gratings; and the N gratings have multiple structures. Line description.

First, when the structures of the N gratings are the same, the at least one beam scanning path is a beam scanning path.

Specifically, when the incident light beam illuminates one of the N gratings and enters another grating adjacent to the one grating, the scanning path of the beam formed by the outgoing beam returns to the starting position to repeat the one beam scanning path. . The light beams of the respective viewing angles in the same viewing plane of the image are sequentially arranged on the one beam scanning path.

Therefore, the observer can see the image on the scanning path (for example, the image is a holographic image), and see different perspectives of the holographic image at different positions of the scanning path, giving the observer a three-dimensional feeling and improving the user experience.

In this case, the embodiment of the present application utilizes a repeated grating structure to cause the scan path to repeat back to the initial point. In order to achieve accurate scanning, each part constituting the spliced grating needs to have the same structure. In other words, the parameters of the N gratings are the same.

For example, the sum of the first angle θ ₁ to the Nth angle θ _N formed by the first grating to the Nth grating of the N gratings is 360 degrees, and θ _n =360°/N; When the same position is used, the raster direction of each raster is the same. Thus, the previous mode is repeated after every 360°/N rotation of the plane. The corresponding outgoing beam also repeats the same scan path.

It should be understood that, in the embodiment of the present application, when the incident beam is a beam of an image, the rotation speed of the raster group and the display frame rate of the image satisfy the following formula:

RS=FR/N

Wherein, the RS represents the rotation speed of the raster group, and FR represents the display frame rate of the image.

That is, at the same frame rate FR, N is inversely proportional to RS.

For example, the display frame rate may represent the same viewing angle position, the display frame rate of the image seen by the user, and the display frame rate may be the lowest image refresh frequency that satisfies the viewing requirements of the human eye.

Secondly, when the N gratings have a plurality of structures, for example, when the N gratings comprise M gratings having different structures, 2 ≤ M ≤ N; the at least one beam scanning path is M beam scanning paths, wherein The beam scanning path formed by the outgoing beams of the grating of the same structure is the same, and the scanning paths formed by the outgoing beams of the gratings of different structures are different.

If the incident beam illuminates the first grating of the first one of the N gratings and enters the second grating illuminating the first structure, the scanning path of the outgoing beam returns to the starting position to repeat the a first beam scanning path corresponding to a grating of a structure,

Alternatively, if the incident beam illuminates the third grating of the first one of the N gratings and enters the fourth grating illuminating the second structure, the scanning path of the outgoing beam corresponds to the grating of the first structure. Switching the first beam scanning path to the second beam scanning path corresponding to the grating of the second structure;

The light beam of each view in the first view plane of the image is sequentially arranged on the first beam scanning path.

The light beams of the respective viewing angles in the second viewing angle plane of the image are sequentially arranged on the second beam scanning path.

Optionally, in the embodiment of the present application, the optical system may further include:

A unidirectional scattering film is disposed on the light exiting side surface of the grating group for enlarging the visible area of the outgoing beam.

For example, the one-way scattering film may enlarge the visible area of the outgoing beam in the vertical direction of the at least one scanning path.

Further, the optical system may further include:

A first lens group including at least one lens is disposed between the spatial light modulator and the grating group for concentrating the incident light beam.

Optionally, the optical system may further include:

A second lens group including at least one lens is disposed on a light exiting side of the grating group for concentrating the outgoing light beam.

It should be understood that the number of the first lens group and the second lens group in the embodiment of the present application is not limited, as long as the convergence of the light beams can be achieved, the lenses of the first lens group and the second lens group according to the actually used scene. The number of the present application can be appropriately adjusted, and the embodiment of the present application is not limited thereto.

Optionally, when the incident beam is irradiated on the nth grating of the N gratings, the nth grating is effectively rotated by an arc, and the viewing angle of the nth beam scanning path formed by the exiting beam passing through the nth grating is satisfied. The following formula:

Wherein, the ARGR indicates the effective rotation arc of the nth grating; the effective rotation arc of the nth grating is the rotation of the nth grating when the spot of the incident beam falls completely on the nth grating during the rotation of the grating group The arc is; Angle_image indicates the viewing angle of the scan path of the nth beam; α indicates the diffraction angle of the nth grating.

Optionally, the spot of the incident beam on the nth grating is a rectangle having a length of H and a width of W.

The minimum length of the two sides of the N gratings intersecting at the same point has the following formula:

Where Angle_D=θ _n -ARGR, AB=W/2/Cos(Angle_D/2), BC=H, R represents the minimum side length of the two edges connected to the same point in the nth raster, wherein When the nth grating is fan-shaped, R also represents the minimum radius of curvature of the sector, and θ _n represents the nth angle formed by the two sides intersecting the same point in the nth grating, and Angle_D indicates the same point. The center of the rectangle corresponds to the arc of the edge closer to the center of the circle.

DRAWINGS

Figure 1 is a schematic view of a scanning mode;

2 is a schematic diagram of scanning results of a scanning method;

Figure 3 is a schematic view of another scanning mode;

Figure 4 is a schematic view of another scanning mode;

FIG. 5 is a schematic structural view of an optical system according to an embodiment of the present application; FIG.

6 is a schematic structural diagram of a grating group of an optical system according to an embodiment of the present application;

FIG. 7 is a schematic structural diagram of a grating group of an optical system according to another embodiment of the present application; FIG.

8 is a schematic diagram of a scan path of an optical system according to an embodiment of the present application;

9 is a schematic diagram of a display area of an optical system in accordance with an embodiment of the present application;

Figure 10 is a schematic illustration of a mathematical model of an optical system in accordance with one embodiment of the present application;

11 is a schematic diagram of a rotation process of a grating according to another embodiment of the present application;

FIG. 12 is a schematic structural diagram of an optical system according to another embodiment of the present application; FIG.

FIG. 13 is a schematic structural view of an optical system according to another embodiment of the present application.

detailed description

In order to facilitate the understanding of the embodiments of the present application, some terms in the description of the embodiments of the present application are first defined as follows:

The term "scanning path" in the embodiment of the present application means a path in which the outgoing beam of the optical system is repeatedly scanned from the start position to the end position. This scan path can also be referred to as a scan track.

It should be understood that the outgoing beam may be a point beam or a beam having a certain spot size. For example, the outgoing beam may be a beam having a rectangular spot size. For example, the rectangular beam may be a beam of an image, specifically, the image. The image may be a two-dimensional image or a three-dimensional image (for example, a holographic image). For example, the light beam of the image may be a light beam of a two-dimensional image or a light beam of each view of the holographic image. The embodiment of the present application is not limited thereto.

It should be noted that the existing scanning methods have their own shortcomings, and it is difficult to meet the actual needs. The following scanning methods will be exemplified in conjunction with FIGS. 1 to 4 .

Figure 1 is a schematic diagram of a scanning method. The scanning method shown in Fig. 1 is an ammeter mode scanning method. Specifically, imaging information (for example, image information) is first projected onto a mirror surface, and the imaging information is distributed into one scanning area by mirror rotation. However, the galvanometer mode scanning method of Figure 1 has a retrace problem. That is, when the scan reaches the boundary position, it must pass through the retrace, that is, move in the opposite direction to return to the home position.

In the retrace process, there are two ways of processing, one, no image is displayed; second, the image is displayed.

For mode one, this method will reduce the use efficiency of the display bandwidth because no image is displayed during retrace. In order to reduce the loss of efficiency, it is necessary to compress the retrace time, so the speed of the retrace is required to be higher than the speed of the scan. This will significantly increase the requirements for the scanning mechanism. For high speed scanning systems, the speed and load capacity of the motor will be limited.

For mode 2, the image can be displayed during the retrace period, which does not reduce the efficiency. But it will produce a retrace effect. Specifically, as shown in FIG. 2, FIG. 2 illustrates an example in which seven scanned images are generated in one direction. As can be seen from Fig. 2, at the same viewing angle position, the interval (scanning period) of the images seen twice may be different. Specifically, it can be seen from the figure that the scan period is fixed to T for the center position of the scan. For the most edge scan position, the scan period is also fixed, but the period of the most edge position has changed to twice the center position period, that is, 2T. For the position immediately adjacent to the edge, the scanning frequency varies with the scanning direction. As shown in the above figure, the interval between the same scanning direction is 10, and the interval between adjacent scanning directions is 2.

For image display, changes in scan frequency will have a serious impact on the system. Suppose the system needs to meet the minimum frame rate f _min . If it is required to maintain such a frame rate at the edge position, the center position must provide a frame rate of 2f _min . If the center position provides a frame rate of f _min , the frame rate at the edge position will be lower than the requirement, affecting the display effect. For other positions, the display effect is also affected due to changes in the scanning frequency, and the display effect is not satisfactory.

Figure 3 is a schematic illustration of another scanning method. The scanning mode shown in FIG. 3 is a cylindrical prism scanning method. Specifically, as shown in FIG. A plurality of mirrors are placed on each of the symmetry prisms to form a cylindrical prism. The input image is projected from one side onto the mirror. As the prism rotates about the central axis, the image is reflected into a scanned area.

Although the retrace problem of the above scheme does not exist in the scanning mode. However, in this mode, the size of the cylindrical prism is determined by the number of mirrors constituting the cylinder and the size of the mirror. The size of the mirror is in turn related to the size of the image projected on the mirror. Therefore, as the projected image size increases, its overall size and weight increase. Suppose the size of the projected image is 100mm × 100mm, if a system consisting of 8 mirrors, the final prism system will be larger than 300mm × 300mm × 100mm. Such a prism is not only bulky, but also has a heavy overall weight. Therefore, a motor requiring a larger power can be driven. Another problem with cylindrical prisms is that the center of rotation of the entire system is the axis of the prism, not the center of the mirror. The distance between the two centers will cause the deformation of the reflected image during the scan. The farther the distance is, the more obvious the deformation is, the display effect will be affected, and the display effect will be unsatisfactory.

Figure 4 is a schematic illustration of another scanning method. The scanning method shown in FIG. 4 is a scanning method of rotating the tilted mirror. Specifically, as shown in FIG. The mirror surface is placed at a 45 degree angle to the horizontal. The projected image is illuminated from directly above to the mirror surface. When the mirror is rotated, the image is reflected onto an annular area to obtain a scanning effect.

Although this solution will not require retrace when used for 360 degree scanning. However, when the required imaging area is not 360-degree surround, it will face a problem similar to that of Figure 1: if the tilted mirror is still rotated by 360 degrees, the required rotation outside the display area will be wasted, similar to the blanking period. , will significantly reduce efficiency; if the rotation only corresponds to the desired area, then a round-trip scan must be used, which will also produce a retrace effect.

For some problems existing in the above-mentioned scanning methods in FIG. 1 to FIG. 4, the embodiment of the present application does not utilize the reflection of the mirror surface, but uses the diffraction generated by the grating to obtain the scanning effect. Specifically, in the embodiment of the present application, a plurality of gratings having the same or different modes may be spliced on a plane in a certain manner to form a grating group. After the input beam passes through the grating group, it is diffracted into different directions, and at least one scanning track is formed as the grating group rotates. Thereby the scanning effect is obtained by the rotation of the planar grating group and the retrace problem is avoided. A detailed description will be given below in conjunction with FIG. 5.

Figure 5 is a schematic illustration of an optical system in accordance with one embodiment of the present application. The optical system 500 as shown in FIG. 5 may include:

The grating group 510 includes N gratings, the N gratings intersect at the same point, and are disposed in the same plane centering on the same point, and the N gratings do not overlap each other, N≥2;

a driving device 520, the driving device includes a central rotating shaft that intersects the grating group perpendicularly at the same point for driving the grating group to rotate around the central rotating shaft in the same plane, so that the incident light beam can The N gratings are alternately illuminated, and at least one beam scanning path is formed on the light exiting side of the grating group.

In addition, in the embodiment of the present application, the grating group of the embodiment of the present application can be made thinner than the cylindrical prism, so that the weight can be very light, so the torque required for the rotation can be small, so that the driving device is driven. The force can be small, for example, when the drive is a motor, the grating set can be driven using a smaller motor. For example, the 30 cm diameter spliced grating group and the supporting plane have a moment of inertia of only 3 × 10 ^-3 kg·m ² , so that the grating group can be driven with a smaller motor, and further, the optical can be reduced by using a small motor. The volume of the system.

It should be understood that the grating group in the embodiment of the present application may also be referred to as a splicing grating. In the embodiment of the present application, the grating group and the splicing grating may be equivalent, which will not be described below.

It should be understood that according to the principle of diffraction, after passing through the grating, the light will be diffracted into multiple diffracted lights of different orders, Each of the stages can be divided into two paths. In the embodiment of the present application, the first order diffracted light can be selected as the scanning path. Specifically, the first order diffracted light has two sides on the central transmitted light. All the way, in the embodiment of the present application, one of the paths is used as a scanning optical path. In other words, the light will be diffracted into two paths (first stage) after passing through the grating. That is to say, in the actual application, only one of the two scan paths is required for each scan path. Therefore, in the embodiment of the present application, only the two scans may be retained. One of the paths, for example, can use a baffle to block the initial beam in the equal-order scanning path of each scanning path to avoid its influence on each scanning path, thereby improving the user experience.

a light source for generating a base beam;

Hereinafter, for the description, the description will be made by taking the image as a holographic image as an example, but the embodiment of the present application is not limited thereto.

In other words, the sum of the N angles corresponding to the N gratings is 360 degrees, wherein one grating corresponds to an angle, and the angle corresponding to each of the N gratings represents the grating of each of the gratings connected to the same point. Two sides The angle of opening.

The following will be described for the same structure for N gratings respectively; and N gratings having various structures.

Therefore, the observer can see the holographic image on the scanning path, and see different perspectives of the holographic image at different positions of the scanning path, giving the observer a three-dimensional feeling and improving the user experience.

For example, the sum of the first angle θ ₁ to the Nth angle θ _N formed by the first grating to the Nth grating of the N gratings is 360 degrees, and θ _n =360°/N; When the same position is used, the raster direction of each raster is the same. Thus, the previous mode is repeated after every 360°/N rotation of the plane. The corresponding outgoing beam also repeats the same scan path. For example, Figure 6 shows a schematic representation of a grating set with an angle of 90 degrees formed by each grating with N = 4. Figure 7 shows a schematic representation of a grating set with an angle of 60 degrees formed by each grating with N = 6.

It should be understood that the shape of the grating of the grating group is exemplified in FIG. 6 and FIG. 7 , but the embodiment of the present application is not limited thereto. For example, the shape of the grating may also be a rectangle or the like, as long as the grating group is rotated. It is possible to make the incident beam all illuminate the grating group.

RS=FR/N

That is, at the same frame rate FR, N is inversely proportional to RS.

Second, when the N gratings have various structures, for example, the N gratings include M different structures of light. In the case of grid, 2≤M≤N; the at least one beam scanning path is M beam scanning paths, wherein the beam of the same type of grating has the same scanning path of the beam, and the outgoing beam of the grating of different structures is formed. The beam scanning path is different.

Wherein, the first beam scanning path is sequentially arranged with the light beams of the respective viewing angles in the first viewing angle plane of the image (for example, the holographic image).

The light beams of the respective viewing angles in the second viewing angle plane of the image (for example, a holographic image) are sequentially arranged on the second beam scanning path.

Specifically, according to the basic principle of the grating, the diffraction deflection angle is related to the input wavelength, as shown in the following equation:

Where d represents the grating constant. θ _j represents the diffraction angle; θ _i represents the incident angle; λ represents the wavelength of the incident beam; m is a constant, indicating the interference level or the spectral level. It can be seen from the above equation that when the incident angle is fixed to the wavelength of the light, the deflection angle will vary with the grating constant d.

It has been described above that when the gratings constituting the spliced grating have the same parameters, a single scanning path is formed during the rotation. In order to be able to provide multiple scan paths, it is also possible to use a grating of different parameters for splicing. As shown in the figure, the grating group is composed of four different parameters, that is, gratings having different grating constants d. The diffraction angles of the first grating (1st), the second grating (2nd), the third grating (3rd), and the fourth grating (4th) are θ ₁ , θ ₂ , θ _{3 ,} and θ ₄ , respectively, wherein θ ₄ > θ ₃ > θ ₂ > θ ₁ . As shown in (a) of Fig. 8, when rotated to the first grating, since the deflection angle is the smallest, the outgoing beam forms the innermost scanning trajectory. When rotating to the second to fourth gratings, as shown in (b) of FIG. 8, (c) of FIG. 8, and (d) of FIG. 8, the outer scanning trajectories are sequentially formed. The holographic images corresponding to different scan trajectories have different viewing angle planes.

Therefore, the observer can see the holographic image on the scanning path, and see different perspectives of the holographic image at different positions of the scanning path, and see the viewing plane of the holographic image differently on different scanning paths, for example, the observer can The height of the upper and lower lines of sight, seeing the holographic images in different viewing angle planes, gives the observer a full range of three-dimensional feelings and enhances the user experience.

It should be understood that, according to the principle of diffraction, light will be diffracted into two paths after passing through the grating. The two scanning paths in (a) to (d) of Fig. 8 have been shown. In practical applications, only one of them can be required, so that a baffle occlusion can be set as shown in (d) of FIG. Another way to avoid the impact of the experience.

It should be understood that the shape of the grating in (a) to (d) of FIG. 8 is a rectangle, but the embodiment of the present application is not limited thereto. For example, the shape of the grating may also be a rectangle or the like as long as the grating group is rotated. The incident beam is all irradiated onto the grating group.

Specifically, for display, it is necessary to add a unidirectional scattering film, for example, a unidirectional vertical scattering film, after splicing the grating to form an effective display area, as shown in FIG. After the exiting beam passes through the rotating grating, it passes through the unidirectional vertical scattering film 901 to form a scanning path 902 which is scattered to form a visible region 903 which enlarges the outgoing beam. In this viewable area, a regular rectangular area can be determined for display, as shown in the rectangular display area 904.

Further, the optical system may further include:

Optionally, the optical system may further include:

The process of determining some parameters of the grating of the grating set of the embodiment of the present application is described below. Specifically, the scanning imaging process of the optical system of the embodiment of the present application can be simplified to a mathematical model as shown in FIG.

Specifically, O _r represents the same point where the N gratings intersect in the grating group, the O point represents the spot of the nth grating in which the input beam is irradiated, and the Angle_image represents the viewing angle of the scanning path of the nth beam. , that is, ∠AOC; ARGR represents the effective rotation arc of the nth grating, that is, the effective rotation arc of the nth grating is that during the rotation of the grating group, when the spot of the incident beam falls completely on the nth grating, the first The radian rotated by the n grating; α represents the diffraction angle of the nth grating. In Fig. 10, for convenience of derivation, it is assumed here that α = ∠ BOG = ∠ AOG = ∠ COG.

According to the principle of grating diffraction:

Where λ represents the wavelength of the incident beam and d represents the grating constant. And can be obtained from Figure 10:

CB=sin(ARGR/2)×r

OC=r/sin(α)

Sin(Angle_image/2)=CB/OC

By combining the above formulas, the relationship between the effective rotation arc of the nth grating and the viewing angle of the nth beam scanning path formed by the outgoing beam passing through the nth grating can be obtained as follows:

It should be understood that, when used for image display, the spot of the input beam on the grating in the embodiment of the present application has a certain size. Because, when the image is rasterized, the spot needs to completely fall on one grating, and the outgoing beam can be The image to be displayed is formed on the scan path. Therefore, in each embodiment of the present application, there is a scan boundary for each of the gratings. For example, as shown in FIG. 11, the nth grating rotates clockwise, and the scanning boundary start position and the scanning end position of the nth grating are as shown in FIG. Within the boundary from the starting position to the ending position, the entire image area is located within a raster area. Wherein, the arc of rotation of the nth grating from the starting position to the ending position is the effective arc of rotation described above ARGR,

Taking the same point as the center, the starting and ending raster positions can be edged to obtain a fan shape. When the fan shape covers the entire image, the radius is the minimum radius of curvature of the spliced grating, that is, the nth grating in the N gratings. The smallest side length of the two sides intersecting at the same point. In Fig. 11, it is assumed that the spot of the incident beam on the grating is a rectangle having a length H and a width W, which can be derived from Fig. 11:

Angle_D=θ _n -ARGR,

AB=W/2/Cos(Angle_D/2),

BC=H,

Angle_m=180°-Angle_D/2

Wherein, R represents a minimum side length of the two sides intersecting the nth grating at the same point, wherein when the nth grating is fan-shaped, R also represents a minimum radius of curvature of the sector, and θ _n represents the nth grating The nth angle formed by the two sides intersecting at the same point, and Angle_D indicates the arc of the spot.

Combining the above formulas, it can be obtained that the minimum side length of the two sides of the N gratings intersecting at the same point satisfies the following formula:

Therefore, in the embodiment of the present application, according to the relationship between the parameters obtained above, in an actual application, an appropriate grating may be selected according to different scenarios of the actual application.

The specific structure of the optical system of the embodiment of the present application for holographic display will be described below with reference to 12 and FIG.

The optical system 1200 shown in Figure 12 includes:

A laser source 1201, a beam splitter 1202, a spatial light modulator 1203, a splicing grating 1204, a motor 1205 connected to the grating group, and a unidirectional vertical scattering film 1206. Optionally, the optical system 1200 can also include a lens 1207 and a baffle 1208.

Specifically, the laser source 1201 is irradiated onto the spatial light modulator 1203 after passing through the beam splitter 1202. Here, the spatial light modulator is described by taking the DMD as an example. The image produced by the DMD modulation passes through the lens 1207 and is irradiated onto the splicing grating 1204 rotated by the motor 1205. A vertical scattering film 1206 is placed after the splicing grating 1204. A hologram formed after the unidirectional vertical scattering film 1206. A visible area is formed behind the hologram. According to the principle of diffraction, the light will be diffracted into two paths after passing through the grating. In the embodiment of the present application, since only one of the paths is needed, a baffle 1208 is needed to block another light to avoid the impact experience.

The specific structure of the optical system of the embodiment of the present application will be described below with reference to a more detailed example of FIG. FIG. 13 can be seen as a more detailed example of the optical system of FIG. 11. Specifically, the optical system 1300 of FIG. 13 can include:

Tri-color laser source (R/G/B Lasers) 1301, Beam splitter 1302, Beam expander 1303, Mirror 1304, Spatial Light Modulator (SLM) 1305, First lens (Lens_1) 1306, a grating group 1307, a motor 1308 connected to the grating group (1307), a unidirectional vertical scattering film 1309, a second lens (Lens_2) 1310, and a third lens (Lens_3) 1311.

Specifically, the three-color laser source 1301 is used to generate a three-color laser light and is irradiated onto the beam splitter 1302. The beam splitter 1302 combines the three-color laser light to transmit the light beam to the beam expander 1303, and is expanded by the beam expander 1303 to generate The base beam of the entire SLM is irradiated, and the base beam is irradiated by the mirror 1304 to be irradiated to the spatial light modulator 1305. Above, the spatial light modulator 1305 loads the image information onto the base beam to produce an incident beam that is concentrated by the first lens 1306. The incident beam is incident on the grating set 1307 rotated by the motor 1308, and the outgoing beam passing through the grating set passes. The unidirectional vertical scattering film 1309 is scattered, and a reconstructed image (Reconstructed image) is formed by the convergence of the second lens 1310 and the third lens 1311.

It should be noted that the examples of FIG. 12 and FIG. 13 are intended to help those skilled in the art to better understand the embodiments of the present application, and do not limit the scope of the embodiments of the present application. A person skilled in the art will be able to make various modifications or changes in the embodiments according to the examples of FIG. 12 and FIG. 13 which are within the scope of the embodiments of the present application.

It is to be understood that the phrase "one embodiment" or "an embodiment" or "an embodiment" or "an embodiment" means that the particular features, structures, or characteristics relating to the embodiments are included in at least one embodiment of the present application. Thus, "in one embodiment" or "in an embodiment" or "an" In addition, these particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in the various embodiments of the present application, the size of the sequence numbers of the foregoing processes does not mean the order of execution sequence, and the order of execution of each process should be determined by its function and internal logic, and should not be applied to the embodiment of the present application. The implementation process constitutes any limitation.

Although the present application has been described in detail by reference to the accompanying drawings in conjunction with the preferred embodiments, this application is not limited thereto. Various equivalent modifications and alterations to the embodiments of the present application can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications or substitutions are intended to be included within the scope of the present application.

Claims

An optical system, comprising:

The grating group includes N gratings, the N gratings intersect at the same point, and are disposed in the same plane centering on the same point, and the N gratings do not overlap each other, N≥2;

a driving device, the driving device comprising a central rotating shaft, the central rotating shaft intersecting the grating group perpendicularly at the same point, and driving the grating group to be centered on the same plane with the central rotating axis Rotating so that the incident beam can be illuminated on the N gratings in turn, forming at least one beam scanning path on the light exit side of the grating group.
The optical system of claim 1 wherein the optical system further comprises:

a light source for generating a base beam;

A spatial light modulator for modulating information of an image onto the base beam to produce the incident beam, the image comprising a two-dimensional image or a three-dimensional image.
The optical system according to claim 2, wherein

The nth grating of the N gratings has two sides intersecting at the same point, and forms an nth angle θ n , where n takes all positive integers from 1 to N,
The optical system according to claim 3, wherein

θ n =360°/N.
The optical system according to any one of claims 2 to 4, characterized in that

The structures of the N gratings are all the same, and the at least one beam scanning path is a beam scanning path.
The optical system according to claim 4, wherein

The N gratings comprise M gratings of different structures, 2≤M≤N;

The at least one beam scanning path is M beam scanning paths, wherein the beam scanning paths formed by the outgoing beams of the gratings of the same structure are the same, and the beam scanning paths formed by the outgoing beams of the gratings of different structures are different.
The optical system according to any one of claims 2 to 6, wherein the optical system further comprises:

A first lens group including at least one lens is disposed between the spatial light modulator and the grating group for concentrating the incident light beam.
The optical system according to any one of claims 2 to 7, wherein the optical system further comprises:

A second lens group including at least one lens is disposed on a light exiting side of the grating group for condensing an outgoing beam.
The optical system according to any one of claims 2 to 8, wherein the rotation speed of the raster group and the display frame rate of the image satisfy the following formula:

RS=FR/N

Where RS represents the rotational speed of the raster group and FR represents the display frame rate of the image.
The optical system according to any one of claims 1 to 9, wherein the optical system further include:

A unidirectional scattering film is disposed on a light exiting side surface of the grating group for enlarging a visible area of the outgoing beam.
The optical system according to any one of claims 1 to 10, characterized in that

When the incident light beam is irradiated on the nth grating of the N gratings, the effective rotation arc of the nth grating and the viewing angle of the nth beam scanning path formed by the outgoing beam passing through the nth grating Meet the following formula:

Wherein, the ARGR indicates the effective rotation arc of the nth grating, and the effective rotation arc of the nth grating is the rotation of the grating group during the rotation, and the spot of the incident beam falls completely on the nth grating. The arc of the nth grating is rotated; Angle_image represents the viewing angle of the nth beam scanning path; and α represents the diffraction angle of the nth grating.
The optical system according to claim 11, wherein the spot of the incident light beam on the nth grating is a rectangle having a length H and a width W.

The minimum side length of the two sides of the nth grating intersecting at the same point satisfies the following formula:

Where Angle_D=θ n -ARGR, AB=W/2/Cos(Angle_D/2), BC=H, R represents the minimum side length of the two edges connected to the same point in the nth raster, θ n represents an nth angle formed by two sides of the nth grating intersecting at the same point, and Angle_D represents an edge of the rectangle which is closer to the center of the circle with the same point as a center The curvature.