CN107515473A - Optical system - Google Patents
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- CN107515473A CN107515473A CN201610423624.3A CN201610423624A CN107515473A CN 107515473 A CN107515473 A CN 107515473A CN 201610423624 A CN201610423624 A CN 201610423624A CN 107515473 A CN107515473 A CN 107515473A
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
- G02B30/50—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images the image being built up from image elements distributed over a 3D volume, e.g. voxels
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
- G02B30/20—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes
- G02B30/34—Stereoscopes providing a stereoscopic pair of separated images corresponding to parallactically displaced views of the same object, e.g. 3D slide viewers
- G02B30/36—Stereoscopes providing a stereoscopic pair of separated images corresponding to parallactically displaced views of the same object, e.g. 3D slide viewers using refractive optical elements, e.g. prisms, in the optical path between the images and the observer
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Abstract
The embodiments of the invention provide a kind of optical system, the optical system includes：Including N number of grating, N number of grating intersects at same point, and same plane is arranged on centered on the same point, and N number of grating non-overlapping copies, N >=2；Drive device, the drive device includes center rotating shaft, the center rotating shaft is vertically intersected on the same point with the grating group, for driving the grating group to be rotated in the same plane centered on the center rotating shaft, incident beam is radiated on N number of grating in turn, at least one beam scanning path is formed in the light emission side of the grating group.Due to when incident beam enters adjacent gratings by a sheet gration in the embodiment of the present invention, outgoing beam will be returned to the original position of wherein one beam scanning path and scan the scanning pattern, the embodiment of the present invention obtains scanning effect without flyback by the rotation of grating group, so as to avoid flyback problem.
Description
Technical Field
The invention relates to the field of optics, in particular to an optical system.
Background
In an optical system, it is often necessary to display contents to be presented by means of scanning. For example, the output beam of the optical system may be projected by scanning into a scanning area (which may also be referred to as a scanning path).
For example, when displaying a 3D holographic image, high bandwidth data of the 3D holographic image can be projected into a scanning path in space by means of scanning to meet the requirements of the 3D holographic display. Specifically, when the 3D holographic image is displayed, images of respective viewing angles of the 3D holographic image may be projected into the scanning path by scanning, and the observer may 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 method, the imaging information is first projected onto a mirror, and the imaging information is distributed within a scanning area by the rotation of the mirror. However, when the scan reaches the boundary position, it must be swept back, i.e., moved in the opposite direction, to return to the starting position. Therefore, the conventional galvanometer mode scanning method has the problem of retrace, and the display effect is influenced.
Therefore, how to provide a scanning method without retrace becomes a problem to be solved urgently.
Disclosure of Invention
Embodiments of the present invention provide an optical system that does not require retrace, thereby avoiding the problem of retrace.
A first aspect provides an optical system comprising:
the grating group comprises N gratings, the N gratings are intersected at the same point and arranged on the same plane by taking the same point as a center, the N gratings are not overlapped with each other, and N is more than or equal to 2;
the driving device comprises a central rotating shaft, the central rotating shaft and the grating group are perpendicularly intersected at the same point and used for driving the grating group to rotate on the same plane by taking the central rotating shaft as a center, so that incident beams can be irradiated on the N gratings in turn, and at least one beam scanning path is formed on the light emergent side of the grating group.
Therefore, the embodiment of the invention drives the grating group to rotate on the same plane by taking the central rotating shaft as the center through driving the transpose, so that the incident beam can be irradiated on the N gratings of the grating group in turn, and at least one beam scanning path is formed on the light emitting side.
It should be understood that the driving device according to the embodiment of the present invention may be a motor, and may also be other driving devices as long as the driving device can be used for driving the grating group to rotate around the central rotation axis, and the embodiment of the present invention is not limited thereto.
It should be understood that, in the embodiment of the present invention, 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 a light beam of an image, specifically, the light beam of the image may be a light beam of each viewing angle of a two-dimensional image or a holographic image, and the like, and the embodiment of the present invention is not limited thereto.
The incident light beam can be generated by other devices and input into the optical system; the input light beam may be generated by the optical system itself, and the embodiments of the present invention are not limited thereto.
Accordingly, when the input light beam is a light beam of an image and the input light beam is generated by the optical system itself, the optical system of the embodiment of the present invention may further include:
a light source for generating a base beam;
and the spatial light modulator is used for modulating information of an image onto the base light beam to generate the incident light beam, wherein the image comprises a two-dimensional image or a three-dimensional image.
It should be understood that the spatial light modulator of the embodiment of the invention may be a Digital micro-mirror display (DMD), or may be other devices, as long as the information of the image is modulated onto the base light beam to generate the incident light beam, and the embodiment of the invention 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 stereo image, and the embodiments of the present invention are 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 arranged in time series.
It should also be understood that the N gratings of the embodiment of the present invention may include 2, 3, 4, 5, 6, 7, 8, etc. gratings, and the embodiment of the present invention is not limited thereto.
It should also be understood that, in the embodiment of the present invention, the shape of one grating in the grating group may be a rectangle, a sector, or the like, and the embodiment of the present invention is not limited thereto.
It is also understood that the N gratings may be disposed in a same plane around the same point, for example, the N gratings may be seamlessly spliced together, that is, the nth grating of the N gratings has two sides intersecting at the same point and forms the nth angle θ n N is taken over all positive integers from 1 to N,
in other words, the sum of N angles corresponding to the N gratings is 360 °, where one grating corresponds to one angle, and the angle corresponding to each grating in the N gratings represents the angle at which two edges of each grating connected to the same point are spread.
In this case, when all the N gratings have a fan shape and have the same radius, the N gratings form a circle. I.e. the sum of the radians of the N gratings is 360.
Optionally, the N gratings may also be disposed on the same plane around the same point with gaps, for example, when all the gratings in the N gratings are fan-shaped and have equal radius, the N gratings are spliced together to form a fan-shaped structure of 180 degrees, 270 degrees, or 320 degrees, etc.; a certain gap may also be left between two adjacent gratings of the N gratings, which is not limited in this embodiment of the present invention.
It should be understood that the included angle θ formed by different gratings in the N gratings in the embodiment of the present invention n The embodiments of the present invention are not limited to the above embodiments. Preferably, the angle θ formed by each grating n All equal, for example, when the sum of the N angles corresponding to the N gratings is 360 °, the angle formed by each grating is 360 °/N.
It should also be understood that the structures of the N gratings in the embodiments of the present invention may be the same; the N gratings may also have a variety of configurations.
The structures of the N gratings are the same below; and N gratings have various structures, both of which are described.
First, when the structures of the N gratings are all the same, the at least one beam scanning path is a beam scanning path.
Specifically, when the incident beam enters from one grating of the N gratings to another grating adjacent to the one grating, the beam scanning path formed by the emergent beam returns to the initial position to repeat the one beam scanning path. The light beams of all the visual angles in the same visual angle plane of the image are sequentially arranged on the light beam scanning path.
Therefore, an observer can see an image (for example, the image is a holographic image) on the scanning path, and see different viewing angles of the holographic image at different positions of the scanning path, so that the observer is provided with a stereoscopic feeling, and the user experience is improved.
In this case, embodiments of the present invention utilize a repeating grating structure such that the scan path repeats back to the initial point. In order to achieve accurate scanning, each of the portions constituting the tiled grating needs to have the same structure, in other words, the parameters of the N gratings are the same.
For example, the 1st included angle θ formed by the 1st grating to the Nth grating in the N gratings 1 To the Nth angle theta N The sum is 360 degrees, and theta n =360 °/N; when the grating is rotated to the same position of different gratings, the grid direction of each grating is the same. Thus, after each 360/N rotation of the plane, the previous pattern is repeated. The corresponding outgoing beam also repeats the same scanning path.
It should be understood that, in the embodiment of the present invention, when the incident light beam is a light beam of an image, the rotation speed of the grating group and the display frame rate of the image satisfy the following formula:
RS＝FR/N
wherein RS represents a rotation speed of the raster set, and FR represents a display frame rate of the image.
That is, N is inversely proportional to RS at the same frame rate FR.
For example, the display frame rate may represent a display frame rate of an image viewed by a user at the same viewing angle position, and the display frame rate may be a minimum image refresh rate satisfying a viewing requirement of human eyes.
Secondly, when the N gratings have various structures, for example, when the N gratings comprise M gratings with different structures, M is more than or equal to 2 and less than or equal to N; the at least one light beam scanning path is M light beam scanning paths, wherein the light beam scanning paths formed by the emergent light beams of the gratings with the same structure are the same, and the light beam scanning paths formed by the emergent light beams of the gratings with different structures are different.
If the incident beam enters the second grating irradiating the first structure from the first grating irradiating the first structure in the N gratings, the scanning path of the emergent beam returns to the initial position to repeat the first beam scanning path corresponding to the grating of the first structure,
or if the incident beam enters a fourth grating irradiating a second structure from a third grating irradiating the first structure in the N gratings, the scanning path of the emergent beam is switched from the first beam scanning path corresponding to the grating of the first structure to the second beam scanning path corresponding to the grating of the second structure;
wherein, the first light beam scanning path is sequentially arranged with light beams of each view angle in the first view angle plane of the image.
The second light beam scanning path is sequentially arranged with light beams of each view angle in a second view angle plane of the image.
Optionally, in an embodiment of the present invention, the optical system may further include:
and the one-way scattering film is arranged on the light-emitting side surface of the grating group and is used for expanding the visible area of the emergent light beam.
For example, the one-way scattering film may enlarge a visible area of the outgoing light beam in a direction perpendicular to the at least one scanning path.
Further, the optical system may further include:
and the first lens group comprising at least one lens is arranged between the spatial light modulator and the grating group and is used for converging the incident light beam.
Optionally, the optical system may further include:
and the second lens group comprises at least one lens, is arranged on the light-emitting side of the grating group and is used for converging the emergent light beam.
It should be understood that, in the embodiment of the present invention, the number of the first lens group and the second lens group is not limited, as long as the convergence of the light beams can be achieved, and the number of the lenses of the first lens group and the second lens group may be appropriately adjusted according to a practical use scenario, and the embodiment of the present invention is not limited thereto.
Optionally, when the incident beam irradiates an nth grating of the N gratings, an effective rotation radian of the nth grating and a visible angle of an nth beam scanning path formed by an emergent beam passing through the nth grating satisfy the following formula:
wherein ARGR represents the effective rotation radian of the nth grating; the effective rotation radian of the nth grating is the radian rotated by the nth grating when the light spot of the incident light beam completely falls on the nth grating in the rotation process of the grating group; angle _ image represents the visual Angle of the nth beam scanning path; α represents a diffraction angle of the nth grating.
It shows that the spot of the incident beam on the nth grating is a rectangle with the length H and the width W,
the minimum side length of the N-th grating intersected in the two sides of the same point satisfies the following formula:
wherein Angle _ D = θ n -ARGR, AB = W/2/Cos (Angle _ D/2), BC = H, R represents the minimum side length of the two sides of the nth grating connected to the same point, wherein, when the nth grating is a sector, R represents the minimum radius of curvature of the sector, θ n And indicating an nth included Angle formed by two edges intersected at the same point in the nth grating, wherein Angle _ D indicates a radian corresponding to an edge, which is closer to the center of the circle, in the rectangle by taking the same point as the center of the circle.
Therefore, the embodiment of the invention drives the grating group to rotate on the same plane by taking the central rotating shaft as a center through driving the transpose, so that the incident beam can irradiate on N gratings of the grating group in turn, and at least one beam scanning path is formed on the light emitting side.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic illustration of one scanning approach;
FIG. 2 is a diagram illustrating the scanning results of one scanning method;
FIG. 3 is a schematic view of another scanning mode;
FIG. 4 is a schematic view of another scanning mode;
FIG. 5 is a schematic diagram of an optical system according to one embodiment of the present invention;
FIG. 6 is a schematic diagram of a structure of a grating group of an optical system according to one embodiment of the present invention;
FIG. 7 is a schematic diagram of a structure of a grating group of an optical system according to another embodiment of the present invention;
FIG. 8 is a schematic diagram of a scan path of an optical system according to one embodiment of the present invention;
FIG. 9 is a schematic diagram of a display area of an optical system according to one embodiment of the invention;
FIG. 10 is a schematic diagram of a mathematical model of an optical system according to one embodiment of the present invention;
FIG. 11 is a schematic view of a rotation process of a grating according to another embodiment of the present invention;
FIG. 12 is a schematic diagram of an optical system according to another embodiment of the present invention;
fig. 13 is a schematic structural view of an optical system according to another embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
To facilitate an understanding of embodiments of the invention, some terms used in the description of embodiments of the invention herein are first defined as follows:
the term "scanning path" in the embodiment of the present invention denotes a path where the outgoing beam of the optical system is repeatedly scanned and irradiated from the start position to the end position. This scan path may also be referred to as a scan trajectory.
It should be understood that the outgoing beam may be a point beam, and may also be a beam with a certain spot size, for example, the outgoing beam may be a beam with a rectangular spot size, for example, the rectangular beam may be a beam of an image, specifically, the image may be a two-dimensional image or a three-dimensional image (e.g., a holographic image), for example, the beam of the image may be a grating of the two-dimensional image or a beam of each viewing angle of the holographic image, and the like, and the embodiments of the present invention are not limited thereto.
It should be noted that the existing scanning methods have respective disadvantages and are difficult to satisfy the practical requirements, and the existing scanning methods will be exemplified with reference to fig. 1 to 4.
Fig. 1 is a schematic diagram of a scanning mode. The scanning mode shown in fig. 1 is a galvanometer mode scanning mode. Specifically, imaging information (e.g., image information) is first projected onto a mirror, and the imaging information is distributed within a scan area by rotation of the mirror. However, the galvanometer mode scan approach of FIG. 1 suffers from kickback problems. That is, when the scan reaches the boundary position, it must be swept back, i.e., moved in the opposite direction, to return to the starting position.
During retrace, there can be two processing modes, one, no image is displayed; 2. and displaying the image.
In the first mode, since no image is displayed during retrace, this mode will reduce the efficiency of using the display bandwidth. To reduce the loss of efficiency, the retrace time needs to be compressed, thus requiring a higher retrace speed than the scan speed. This will significantly increase the requirements on the scanning mechanism, and for systems requiring high speed scanning, the speed and load capacity of the motor will be limited.
With respect to the second mode, an image can be displayed using a retrace period, which does not reduce efficiency. But produces a kickback effect. Specifically, as shown in fig. 2, fig. 2 illustrates an example in which 7 scan images are generated in a single direction. As can be seen from fig. 2, the interval (scan period) between two views of the image may be different at the same viewing angle position. Specifically, as can be seen from the figure, the scanning period is fixed to T for the center position of the scanning. For the edgemost scan position, its scan period is also fixed, but the period of the edgemost position has changed to twice the period of the center position, i.e., 2T. For positions 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 directions is 10, and the interval between the adjacent different scanning directions is 2.
For image display, the variation of the scanning frequency will have a serious influence on the system. Suppose the system needs to meet a minimum frame rate f min . If it is desired to maintain such a frame rate also at the edge positions, the center position must be provided with 2f min The frame rate of (2). If the central position provides f min The frame rate of the edge position will be lower than required, and the display effect will be affected. For other positions, the scanning frequency changes, the display effect is also affected, and the display effect is not ideal.
Fig. 3 is a schematic diagram of another scanning mode. The scanning system shown in fig. 3 is a cylindrical prism scanning system. Specifically, as shown in fig. 3. A plurality of mirror surfaces are arranged on each vertical surface of the axisymmetric prism to form a cylindrical prism. The input image is projected from one side onto a mirror. When the prism is rotated about the central axis, the image will be reflected into a scanning area.
Although the scan mode does not have the problem of kickback of the above scheme. However, in this method, the size of the cylindrical prism is determined by the number of mirrors constituting the cylindrical surface and the size of the mirrors. The size of the mirror, in turn, is related to the size of the image projected on the mirror. As the size of the projected image increases, the overall size and weight of the projected image increases. Assuming a projected image size of 100mm x 100mm, the final prism system would be larger than 300mm x 100mm if a system of 8 mirrors were used. Such a prism is bulky and heavy in overall weight. And therefore require a more powerful motor to be able to drive. Another problem with cylindrical prisms is: the center of rotation of the entire system is the prism axis, not the center of the mirror. The distance between these two centers will result in a distortion of the reflected image during scanning. The longer the distance is, the more obvious the deformation is, the display effect is also influenced, and the display effect is not ideal.
Fig. 4 is a schematic diagram of another scanning mode. The scanning system shown in fig. 4 is a scanning system in which the tilt mirror is rotated. Specifically, as shown in fig. 4. The reflecting mirror surface is arranged at an angle of 45 degrees with the horizontal plane. The projected image is irradiated from the right above onto the mirror surface. When the mirror rotates, the image is reflected onto an annular area, thereby obtaining a scanning effect.
Although this scheme would not require retrace when used for 360 degree scanning. But when the required imaging area is not 360 degrees around, similar problems as in fig. 1 are encountered: that is, if the tilting mirror is still rotated by 360 degrees, the required rotation process outside the display area will be wasted, which, like the blanking period, will significantly reduce the efficiency; if the rotation corresponds only to the desired area, a back-and-forth scan must be used, again producing a flyback effect.
In view of some problems of the conventional scanning methods in fig. 1 to 4, the embodiment of the present invention does not use the reflection of a mirror surface, but uses the diffraction generated by the grating to obtain the scanning effect. Specifically, in the embodiment of the present invention, a plurality of gratings having the same or different patterns may be spliced on a plane according to a certain manner to form a grating group. The input light beam is diffracted to different directions after passing through the grating group, and forms at least one scanning track along with the rotation of the grating group. Thereby obtaining a scanning effect by rotation of the plane grating group and avoiding the problem of retrace. As will be described in detail below in connection with fig. 5.
FIG. 5 is a schematic diagram of an optical system according to one embodiment of the present invention. The optical system 500 as shown in fig. 5 may include:
the grating group 510 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 a center, the N gratings are not overlapped with each other, and N is more than or equal to 2;
and a driving device 520, which includes a central rotation axis perpendicularly intersecting the grating group at the same point, and configured to drive the grating group to rotate around the central rotation axis in the same plane, so that the incident light beams can alternately irradiate on the N gratings, and at least one light beam scanning path is formed on the light exit side of the grating group.
Therefore, the embodiment of the invention drives the grating group to rotate on the same plane by taking the central rotating shaft as the center through driving the transpose, so that the incident beam can be irradiated on the N gratings of the grating group in turn, and at least one beam scanning path is formed on the light emitting side.
In addition, in the embodiment of the present invention, compared with the cylindrical prism, the grating group of the embodiment of the present invention can be made very thin, so that the weight can be very light, and therefore, the torque required for rotation can be very small, so that the driving force of the driving device can be small, for example, when the driving device is a motor, the grating group can be driven by using a smaller motor. For example, the rotational inertia of the spliced grating group with the diameter of 30cm and the supporting plane is only 3 multiplied by 10 -3 kg·m 2 Therefore, the grating group can be driven using a smaller motor, and further, the use of a smaller motor can also be reducedThe volume of the optical system.
It should be understood that the driving device of the embodiment of the present invention may be a motor, and may also be other driving devices as long as the driving device can be used to drive the grating group to rotate around the central rotating shaft, and the embodiment of the present invention is not limited thereto.
It should be understood that the grating group in the embodiment of the present invention may also be referred to as a tiled grating, and in the embodiment of the present invention, the grating group and the tiled grating may be equivalent, and will not be described one by one below.
It should be understood that, according to the principle of diffraction, the light will be diffracted into multiple diffracted lights of different orders after passing through the grating, where each order can be divided into two paths. In other words, the light will be diffracted into two paths (first order) after passing through the grating. That is to say, each scanning path has one equivalent-step scanning path, and in practical application, only one of the two scanning paths is needed, so in the embodiment of the present invention, only one of the two scanning paths may be retained, for example, the primary light beam in the equivalent-step scanning path of each scanning path may be blocked by using a baffle, so as to avoid an influence of the primary light beam on each scanning path, and improve user experience.
It should be understood that, in the embodiment of the present invention, 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 a light beam of an image, specifically, the light beam of the image may be a light beam of each viewing angle of a two-dimensional image or a holographic image, and the like, and the embodiment of the present invention is not limited thereto.
The incident light beam can be generated by other devices and input into the optical system; the input light beam may be generated by the optical system itself, and the embodiments of the present invention are not limited thereto.
Accordingly, when the input light beam is a light beam of an image and the input light beam is generated by the optical system itself, the optical system of the embodiment of the present invention may further include:
a light source for generating a base beam;
and a spatial light modulator for modulating information of an image onto the base light beam to generate the incident light beam, wherein the image comprises a two-dimensional image or a three-dimensional image.
It should be understood that the spatial light modulator of the embodiment of the invention may be a Digital micro-mirror display (DMD), or may be other devices, as long as the information of the image is modulated onto the base light beam to generate the incident light beam, and the embodiment of the invention 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 stereo image, and the embodiments of the present invention are 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 arranged in time series.
Hereinafter, for the purpose of description, a description will be developed taking the image as a holographic image as an example, but the embodiment of the present invention is not limited thereto.
It should also be understood that the N gratings of the embodiment of the present invention may include 2, 3, 4, 5, 6, 7, 8, etc. gratings, and the embodiment of the present invention is not limited thereto.
It should also be understood that, in the embodiment of the present invention, the shape of one grating in the grating group may be a rectangle, a sector, or the like, and the embodiment of the present invention is not limited thereto.
It should also be understood that the N gratings may be disposed in the same plane around the same point, for example, the N gratings may be seamlessly spliced together, that is, the nth grating of the N gratings has two sides intersecting at the same point and forms the nth included angle θ n N is taken over all positive integers from 1 to N,
in other words, the sum of the N angles corresponding to the N gratings is 360 degrees, where one grating corresponds to one angle, and the angle corresponding to each grating in the N gratings represents the angle spread by two edges of each grating connected to the same point.
In this case, when all the N gratings have a fan shape and have the same radius, the N gratings form a circle. I.e. the sum of the radians of the N gratings is 360.
Optionally, the N gratings may also be disposed on the same plane around the same point with gaps, for example, when all the gratings in the N gratings are fan-shaped and have equal radius, the N gratings are spliced together to form a fan-shaped structure of 180 degrees, 270 degrees, or 320 degrees, etc.; a certain gap may also be left between two adjacent gratings of the N gratings, which is not limited in this embodiment of the present invention.
It should be understood that the included angle θ formed by different gratings in the N gratings in the embodiments of the present invention n The embodiments of the present invention are not limited to the above embodiments. Preferably, the angle θ formed by each grating n All equal, for example, when the sum of the N angles corresponding to the N gratings is 360 °, the angle formed by each grating is 360 °/N.
It should also be understood that the structures of the N gratings in the embodiments of the present invention may be the same; the N gratings may also have a variety of configurations.
The structures of the N gratings are the same respectively; and N gratings have various structures, both of which are described.
First, when the structures of the N gratings are all the same, the at least one beam scanning path is a beam scanning path.
Specifically, when the incident beam enters from one grating of the N gratings to another grating adjacent to the one grating, the beam scanning path formed by the emergent beam returns to the initial position to repeat the one beam scanning path. The light beams of all the visual angles in the same visual angle plane of the image are sequentially arranged on the light beam scanning path.
Therefore, an observer can see the holographic image on the scanning path, and can see different visual angles of the holographic image at different positions of the scanning path, so that the observer can feel three-dimensional, and the user experience is improved.
In this case, embodiments of the present invention utilize a repeating grating structure such that the scan path repeats back to the initial point. In order to achieve accurate scanning, each of the portions constituting the tiled grating needs to have the same structure, in other words, the parameters of the N gratings are the same.
For example, the 1st included angle θ formed by the 1st grating to the Nth grating in the N gratings 1 To the Nth angle theta N The sum is 360 degrees, and theta n =360 °/N; when the grating is rotated to the same position of different gratings, the grid direction of each grating is the same. Thus, after each 360/N rotation of the plane, the previous pattern is repeated. The corresponding outgoing beam also repeats the same scanning path. For example, fig. 6 shows a schematic diagram of a grating group with N =4 and each grating forms an included angle of 90 degrees. Fig. 7 shows a schematic diagram of a grating group with N =6 and each grating forming an angle of 60 degrees.
It should be understood that fig. 6 and 7 illustrate the shape of the grating group as a sector, but the embodiment of the present invention is not limited thereto, for example, the shape of the grating may also be a rectangle, etc., as long as the incident light beam can be fully irradiated onto the grating group during the rotation of the grating group.
It should be understood that, in the embodiment of the present invention, when the incident light beam is a light beam of an image, the rotation speed of the grating group and the display frame rate of the image satisfy the following formula:
RS＝FR/N
wherein RS represents a rotation speed of the raster set, and FR represents a display frame rate of the image.
That is, N is inversely proportional to RS at the same frame rate FR.
For example, the display frame rate may represent a display frame rate of an image viewed by a user at the same viewing angle position, and the display frame rate may be a minimum image refresh rate satisfying a viewing requirement of human eyes.
Secondly, when the N gratings have various structures, for example, when the N gratings comprise M gratings with different structures, M is more than or equal to 2 and less than or equal to N; the at least one light beam scanning path is M light beam scanning paths, wherein the light beam scanning paths formed by the emergent light beams of the gratings with the same structure are the same, and the light beam scanning paths formed by the emergent light beams of the gratings with different structures are different.
If the incident beam enters the second grating irradiating the first structure from the first grating irradiating the first structure in the N gratings, the scanning path of the emergent beam returns to the initial position to repeat the first beam scanning path corresponding to the grating of the first structure,
or if the incident beam enters a fourth grating irradiating a second structure from a third grating irradiating the first structure in the N gratings, the scanning path of the emergent beam is switched from the first beam scanning path corresponding to the grating of the first structure to the second beam scanning path corresponding to the grating of the second structure;
wherein the first beam scan path has the beams of each view angle in the first view angle plane of the image (e.g., holographic image) arranged in sequence.
The second beam scan path has the beams at each viewing angle in a second viewing angle plane of the image (e.g., holographic image) arranged in sequence.
Specifically, according to the basic principle of a grating, the diffraction deflection angle is related to the input wavelength, as shown in the following equation:
where d represents the grating constant. Theta j Represents the diffraction angle; theta i Represents an incident angle; λ represents the wavelength of the incident beam; m is a constant, representing the interference or spectral order. As can be seen from the above formula, the deflection angle is fixed when the incident angle is fixed with the wavelength of lightThe degree will vary with the grating constant d.
It has been described above that when the gratings constituting the tiled grating have the same parameters, a single scan path is formed during rotation. In order to provide multiple scanning paths, gratings with different parameters can be used for splicing. As shown, the grating group is composed of 4 gratings with different parameters, i.e. different grating constants d. Wherein the diffraction angles of the first grating (1 st), the second grating (2 nd), the third grating (3 rd) and the fourth grating (4 th) are respectively theta 1 、θ 2 、θ 3 And theta 4 Wherein, theta 4 >θ 3 >θ 2 >θ 1 . As shown in fig. 8 (a), when rotated to the first grating, the emergent beam forms the innermost scanning track because the deflection angle is the smallest. When rotating to the second to fourth rasters, the outer scanning tracks are formed in order as shown in fig. 8 (b), fig. 8 (c), and fig. 8 (d). Wherein, the visual angle planes of the holographic images corresponding to different scanning tracks are different.
Therefore, an observer can see the holographic image on the scanning path, see different viewing angles of the holographic image at different positions of the scanning path, and see different viewing angle planes of the holographic image on different scanning paths, for example, the observer can see the holographic image in different viewing angle planes at the height of the upper and lower sight lines, so that the observer can have all-round stereoscopic feeling, and the user experience is improved.
It should be understood that, according to the principle of diffraction, the light will be diffracted into two paths after passing through the grating. Two scanning paths in fig. 8 (a) to (d) are shown, and in practical applications, only one of the scanning paths may be needed, so that a baffle may be disposed as shown in fig. 8 (d) to block the other scanning path, so as to avoid affecting the experience.
It should be understood that the shape of the grating in (a) to (d) in fig. 8 is a rectangle, but the embodiment of the present invention is not limited thereto, for example, the shape of the grating may also be a rectangle, etc., as long as the incident light beam can be fully irradiated onto the grating group during the rotation of the grating group.
Optionally, in an embodiment of the present invention, the optical system may further include:
and the one-way scattering film is arranged on the light-emitting side surface of the grating group and is used for expanding the visible area of the emergent light beam.
For example, the one-way scattering film may enlarge a visible area of the outgoing light beam in a direction perpendicular to the at least one scanning path.
Specifically, when the display is used, a piece of one-way scattering film, for example, a one-way vertical scattering film, needs to be added after the grating is spliced to form an effective display area, as shown in fig. 9. The emergent beam passes through the rotating grating and then passes through the one-way vertical scattering film 901 to form a scanning path 902, and the scanning path is scattered to form a visible area 903 of the expanded emergent beam. In this viewable area, a regular rectangular area may be determined for display, as shown by the rectangular display area 904.
Further, the optical system may further include:
and the first lens group comprising at least one lens is arranged between the spatial light modulator and the grating group and is used for converging the incident light beam.
Optionally, the optical system may further include:
and the second lens group comprises at least one lens, is arranged on the light-emitting side of the grating group and is used for converging the emergent 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 invention is not limited as long as the convergence of the light beams can be achieved, and the number of the lenses of the first lens group and the second lens group may be appropriately adjusted according to the actual use scenario, and the embodiment of the present invention is not limited thereto.
The following describes a process for determining some parameters of the gratings of a grating group of an embodiment of the present invention. Specifically, the scanning imaging process of the optical system of the embodiment of the present invention can be simplified to a mathematical model as shown in fig. 10.
Specifically, O r Indicating the same point where the N gratings in the grating group intersect, and point O indicating the first point where the input beam irradiates the N gratingsAn n raster of light spots, angle _ image represents the visual Angle of the nth beam scanning path, namely ≈ AOC; the ARGR represents an effective rotation radian of the nth grating, that is, the effective rotation radian of the nth grating is a radian rotated by the nth grating when a light spot of the incident light beam completely falls on the nth grating in a rotation process of the grating group; α represents a diffraction angle of the nth grating. In fig. 10, for ease of derivation, let α = ≈ BOG = ≈ AOG = COG here.
According to the principle of grating diffraction:where λ represents the wavelength of the incident beam and d represents the grating constant. And from fig. 10 can be derived:
CB＝sin(ARGR/2)×r
OC＝r/sin(α)
sin(Angle_image/2)＝CB/OC
combining the above formulas, we can get: the relationship between the effective rotation radian of the nth grating and the visible angle of the nth beam scanning path formed by the emergent beam passing through the nth grating is as follows:
it should be understood that when the input light beam is used for image display, the light spot of the input light beam on the grating has a certain size, and since the light spot needs to completely fall on one grating when the light beam is imaged by the grating, the emergent light beam can form the image to be displayed on the scanning path. Thus, in embodiments of the present invention, a scan boundary exists for each raster. For example, as shown in fig. 11, the nth raster rotates clockwise, and the scanning boundary start position and the scanning end position of the nth raster are as shown in fig. 11. Within the boundary from the starting position to the end position, the entire image area is located within one raster area. Wherein the rotation radian of the nth grating from the starting position to the ending position is the effective rotation radian ARGR,
when the fan shape just covers the whole image, the radius of the fan shape is the minimum curvature radius of the spliced grating, namely the nth grating of the N gratings intersects with the minimum side length in two sides of the same point. In fig. 11, assuming that the spot of the incident beam on the grating is a rectangle with a length H and a width W, it 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 the minimum side length of two sides of the n-th grating intersected at the same point, wherein, when the n-th grating is fan-shaped, R also represents the minimum curvature radius of the fan-shaped, theta n The nth Angle formed by two edges intersecting at the same point in the nth grating is shown, and Angle _ D represents the radian of the light spot.
Combining the above formulas, the minimum side length of the N-th grating intersecting with the same point in two sides of the same point satisfies the following formula:
therefore, according to the relationship between the parameters obtained above, in practical application, a suitable grating can be selected according to different scenes of the practical application.
The specific structure of the optical system of the embodiment of the present invention for holographic display is described below with reference to specific examples of fig. 12 and 13.
The optical system 1200 shown in fig. 12 includes:
the device comprises a laser source 1201, a beam splitter 1202, a spatial light modulator 1203, a spliced grating 1204, a motor 1205 connected with a grating group, and a one-way vertical scattering film 1206. Optionally, the optical system 1200 may further include a lens 1207 and a baffle 1208.
Specifically, the laser source 1201 passes through the beam splitter 1202 and then irradiates the spatial light modulator 1203, which is exemplified by a DMD. The image generated by the DMD modulation is irradiated to a tiled grating 1204 rotated by a motor 1205 through a lens 1207. A vertical scattering film 1206 is placed behind the tiled grating 1204. A hologram formed behind the unidirectional vertical scattering film 1206. A viewable area is formed behind the hologram. According to the principle of diffraction, light is diffracted into two paths after passing through the grating. In the embodiment of the present invention, only one of the light beams is needed, so that one of the light beams needs to be blocked by one of the blocking plates 1208 to prevent the other light beam from affecting the experience
The specific structure of the optical system of the embodiment of the present invention is described below with reference to a more detailed example of fig. 13. Fig. 13 can be seen as a more detailed example of the optical system of fig. 11, in particular, the optical system 1300 of fig. 13 may include:
a three-color laser source (R/G/B Lasers) 1301, a Beam splitter (Beam splitter) 1302, a Beam expander (Beam expander) 1303, a Mirror (Mirror) 1304, a Spatial Light Modulator (SLM) 1305, a 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, a three-color laser source 1301 is used to generate three-color laser light and irradiate the light splitter 1302, the light splitter 1302 combines the three-color laser light, transmits the light beam to a beam expander 1303, generates a base light beam capable of irradiating the entire SLM through expansion of the beam expander 1303, the base light beam irradiates a spatial light modulator 1305 through irradiation of a mirror 1304, the spatial light modulator 1305 loads image information onto the base light beam, generates an incident light beam through convergence of a first lens 1306, the incident light beam irradiates a grating group 1307 rotated by a motor 1308, the emergent light beam through the grating group is scattered by a unidirectional vertical scattering film 1309, and a Reconstructed image (Reconstructed image) is formed through convergence of a second lens 1310 and a third lens 1311.
It should be noted that the examples of fig. 12 and 13 are provided to assist those skilled in the art to better understand the embodiments of the present invention, and are not intended to limit the scope of the embodiments of the present invention. It will be apparent to those skilled in the art that various equivalent modifications or variations are possible in light of the examples given in fig. 12 and 13, and such modifications or variations are also within the scope of the embodiments of the invention.
It should be appreciated that reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in various embodiments of the present invention, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
Although the present invention has been described in detail by referring to the drawings in connection with the preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or alterations to the embodiments of the present invention may be made by those skilled in the art without departing from the spirit and scope of the present invention, and such modifications or alterations are intended to be within the scope of the present invention.
Claims (12)
1. An optical system, comprising:
the grating group comprises N gratings, the N gratings are intersected at the same point and arranged on the same plane by taking the same point as a center, the N gratings are not overlapped with each other, and N is more than or equal to 2;
the driving device comprises a central rotating shaft, the central rotating shaft is vertically intersected with the grating group at the same point and used for driving the grating group to rotate around the central rotating shaft on the same plane, so that incident beams can irradiate on the N gratings in turn, and at least one beam scanning path is formed on the light emergent side of the grating group.
2. The optical system of claim 1, further comprising:
a light source for generating a base beam;
a spatial light modulator for modulating information of an image onto the base light beam, producing the incident light beam, the image comprising a two-dimensional image or a three-dimensional image.
3. The optical system according to claim 2,
the nth grating of the N gratings has two sides intersecting at the same point and forms an nth included angle theta n N is taken all over the positive integers from 1 to N,
4. the optical system according to claim 3,
θ n ＝360°/N。
5. the optical system according to any one of claims 2 to 4,
the structures of the N gratings are the same, and the at least one light beam scanning path is a light beam scanning path.
6. The optical system according to claim 4,
the N gratings comprise M gratings with different structures, and M is more than or equal to 2 and less than or equal to N;
the at least one light beam scanning path is M light beam scanning paths, wherein light beam scanning paths formed by emergent light beams of gratings with the same structure are the same, and emergent light beams of gratings with different structures are different in the formed light beam scanning paths.
7. The optical system according to any one of claims 2 to 6, characterized in that the optical system further comprises:
and the first lens group comprises at least one lens, is arranged between the spatial light modulator and the grating group and is used for converging the incident light beam.
8. The optical system according to any one of claims 2 to 7, characterized in that the optical system further comprises:
the second lens group comprises at least one lens, is arranged on the light-emitting side of the grating group and is used for converging emergent light beams.
9. The optical system according to any one of claims 2 to 8, wherein the rotation speed of the grating group and the display frame rate of the image satisfy the following formula:
RS＝FR/N
wherein RS represents a rotation speed of the grating group, and FR represents a display frame rate of the image.
10. The optical system according to any one of claims 1 to 9, characterized in that the optical system further comprises:
and the one-way scattering film is arranged on the light-emitting side surface of the grating group and is used for expanding the visible area of the emergent light beam.
11. The optical system according to any one of claims 1 to 10,
when the incident beam irradiates an nth grating in the N gratings, the effective rotation radian of the nth grating and the visible angle of an nth beam scanning path formed by an emergent beam passing through the nth grating satisfy the following formula:
the ARGR represents the effective rotation radian of the nth grating, and the effective rotation radian of the nth grating is the radian rotated by the nth grating when the light spot of the incident light beam completely falls on the nth grating in the rotation process of the grating group; angle _ image represents the Angle of visibility of the nth beam scan path; α represents a diffraction angle of the nth grating.
12. The optical system of claim 11, wherein the spot of the incident light beam on the nth grating is a rectangle with a length H and a width W,
the minimum side length of the two sides of the n-th grating which are intersected at the same point meets the following formula:
wherein Angle _ D = θ n -ARGR, AB = W/2/Cos (Angle _ D/2), BC = H, R representing the minimum side length of the two sides of the nth grating connected to the same point, θ n And representing an nth included Angle formed by two edges intersecting at the same point in the nth grating, wherein Angle _ D represents a radian corresponding to an edge, which is closer to the center of the circle, in the rectangle by taking the same point as the center of the circle.
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Citations (6)
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| US4852956A (en) * | 1986-12-15 | 1989-08-01 | Holotek Ltd. | Hologan scanner system |
| CN2201704Y (en) * | 1994-05-23 | 1995-06-21 | 乐勤 | Dynamic raster advertisment device |
| US5504595A (en) * | 1992-05-26 | 1996-04-02 | Symbol Technologies, Inc. | Holographic scanning |
| US5859715A (en) * | 1996-07-19 | 1999-01-12 | Eastman Kodak Company | Diffractive laser scanner |
| CN1749804A (en) * | 2004-08-18 | 2006-03-22 | Lg电子株式会社 | Raster scanning display system |
| CN105023492A (en) * | 2015-07-15 | 2015-11-04 | 武汉理工大学 | True color holographic imaging experiment apparatus |
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2016
- 2016-06-15 CN CN201610423624.3A patent/CN107515473B/en active Active
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4852956A (en) * | 1986-12-15 | 1989-08-01 | Holotek Ltd. | Hologan scanner system |
| US5504595A (en) * | 1992-05-26 | 1996-04-02 | Symbol Technologies, Inc. | Holographic scanning |
| CN2201704Y (en) * | 1994-05-23 | 1995-06-21 | 乐勤 | Dynamic raster advertisment device |
| US5859715A (en) * | 1996-07-19 | 1999-01-12 | Eastman Kodak Company | Diffractive laser scanner |
| CN1749804A (en) * | 2004-08-18 | 2006-03-22 | Lg电子株式会社 | Raster scanning display system |
| CN105023492A (en) * | 2015-07-15 | 2015-11-04 | 武汉理工大学 | True color holographic imaging experiment apparatus |
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