CN112558275A - Optical imaging lens group, scanning display device and near-to-eye display equipment - Google Patents
Optical imaging lens group, scanning display device and near-to-eye display equipment Download PDFInfo
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- 238000012634 optical imaging Methods 0.000 title claims abstract description 90
- 238000003384 imaging method Methods 0.000 claims description 41
- 239000013307 optical fiber Substances 0.000 claims description 33
- 230000003287 optical effect Effects 0.000 claims description 28
- 230000003190 augmentative effect Effects 0.000 claims description 3
- 239000000835 fiber Substances 0.000 description 18
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- 238000012546 transfer Methods 0.000 description 3
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
- G02B13/005—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having spherical lenses only
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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
- G02B26/103—Scanning systems having movable or deformable optical fibres, light guides or waveguides as scanning elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B27/0172—Head mounted characterised by optical features
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B2027/011—Head-up displays characterised by optical features comprising device for correcting geometrical aberrations, distortion
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/0101—Head-up displays characterised by optical features
- G02B2027/013—Head-up displays characterised by optical features comprising a combiner of particular shape, e.g. curvature
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/01—Head-up displays
- G02B27/017—Head mounted
- G02B2027/0178—Eyeglass type
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Abstract
The embodiment of the application discloses an optical imaging lens group, a display device and near-to-eye display equipment, wherein the optical imaging lens group comprises a first lens, a second lens and a third lens, wherein the first lens, the second lens and the third lens are coaxially arranged in sequence from a first side to a second side; the first side surface of the first lens is a convex surface, and the second side surface of the first lens is a convex surface; a first side surface of the second lens is concave at a paraxial region, and a second side surface of the second lens is convex; the first side surface of the sixth lens element is convex and the second side surface of the sixth lens element is concave at paraxial region.
Description
Technical Field
The application relates to the technical field of scanning display, in particular to an optical imaging lens group, a scanning display device and near-to-eye display equipment.
Background
Scanning display imaging is a new display technology, and can be used for various application scenes such as projection display, near-eye display and the like.
Particularly for application scenes of near-eye display, along with the continuous improvement of the requirements on miniaturization, lightness and imaging definition of near-eye display equipment, the requirements on high resolution and miniaturization of the optical imaging lens group of the near-eye display equipment are also more and more stringent. Therefore, it is an urgent need in the art to provide a miniaturized optical lens assembly with high imaging quality for use in a near-eye display scene.
Disclosure of Invention
The application aims to provide an optical imaging lens group, a scanning display device and a near-eye display device so as to meet the requirements of high imaging quality and miniaturization in a near-eye display scene.
The embodiment of the present application provides an optical imaging lens assembly, comprising a first lens element to a sixth lens element coaxially disposed in sequence from a first side to a second side,
the first side surface of the first lens is a convex surface, and the second side surface of the first lens is a convex surface; a first side surface of the second lens is concave at a paraxial region, and a second side surface of the second lens is convex; the first side surface of the sixth lens element is convex and the second side surface of the sixth lens element is concave at paraxial region.
Optionally, the refractive index of the first lens satisfies:
1.5<n1<1.7;
wherein n1 is the refractive index of the first lens.
Optionally, the refractive index of the second lens satisfies:
1.5<n2<1.8;
wherein n2 is the refractive index of the second lens.
Optionally, the refractive index of the sixth lens satisfies:
1.8<n6<2.0;
wherein n6 is a refractive index of the sixth lens.
Optionally, the overall length of the optical imaging lens group is less than or equal to 15 mm.
Optionally, the overall length of the optical lens group is the maximum length from the first side surface of the first lens to the second side surface of the sixth lens.
Optionally, the second side of the optical imaging lens group corresponds to a curved image.
The embodiment of the application also provides a scanning display device, which comprises an optical fiber scanner and the optical imaging lens group, wherein the optical fiber scanner is used for scanning and emitting light of an image to be displayed, and the optical imaging lens group is used for amplifying, imaging and projecting a scanning surface corresponding to the light emitted by the optical fiber scanner;
the optical fiber scanner comprises an actuator and an optical fiber fixed on the actuator, wherein a part of the optical fiber, which exceeds the actuator, forms an optical fiber cantilever, and the optical fiber cantilever is driven by the actuator to perform two-dimensional scanning.
The embodiment of the application further provides near-eye display equipment which is used as head-mounted augmented reality equipment and at least comprises a near-eye display module and the scanning display device, wherein the scanning display device is arranged in the near-eye display module.
The embodiment of the application also provides near-eye display equipment which is used as head-mounted virtual reality equipment and at least comprises a near-eye display module and the scanning display device, wherein the scanning display device is arranged in the near-eye display module
By adopting the technical scheme in the embodiment of the application, the following technical effects can be realized:
in the embodiment of the application, the surface types and the focal lengths of six coaxial lenses of the optical imaging lens group are reasonably and optimally set, so that the focal power of the system can be reasonably dispersed, the aberration generated by the lenses can be reduced, a small number of lenses can be used, various aberrations can be corrected, and clear imaging of the image side curved surface can be realized. Meanwhile, the whole length of the optical imaging lens group is smaller than or equal to 15mm, the focal length of the optical imaging lens group can be larger than or equal to 3mm, and the imaging requirement of high resolution can be met while the miniaturization of the system is realized. In particular, the eyepiece lens is preferably applicable to a near-eye display device which is reduced in size and weight and requires an increasing demand for image sharpness.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the application may be realized and attained by the structure and/or processes particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, made with reference to the accompanying drawings in which:
FIGS. 1a and 1b are schematic structural views of an illustrative scanning display system;
FIG. 2 is a schematic diagram of a scan output of a fiber scanner provided by an embodiment of the present application;
FIG. 3 is a schematic structural diagram of an optical imaging lens assembly according to an embodiment of the present application;
FIG. 4 is a MTF graph of an optical imaging lens assembly according to an embodiment of the present disclosure;
FIG. 5 is a graph of field curvature distortion of an optical imaging lens assembly in accordance with an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of another optical imaging lens assembly provided in the second embodiment of the present application;
FIG. 7 is a MTF graph of an optical imaging lens assembly according to a second embodiment of the present application;
fig. 8 is a graph of field curvature distortion of the optical imaging lens assembly in example two of the present application.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
Illustrative scanning display system
For current Scanning Display imaging, it can be realized by Digital Micromirror Device (DMD) or Fiber Scanning Display (FSD) Device. The FSD scheme is used as a novel scanning display imaging mode, and the scanning output of images is realized through an optical fiber scanner. In order to make the solution of the present application clearly understandable to those skilled in the art, the following provides a brief description of the principles of fiber scanning imaging and a corresponding system.
Fig. 1a is a schematic diagram of an illustrative scanning display system according to the present application, which mainly includes:
the optical fiber scanning device comprises a processor 100, a laser group 110, a fiber scanning module 120, a transmission fiber 130, a light source modulation circuit 140, a scanning driving circuit 150 and a beam combining unit 160. Wherein,
the processor 100 may be a Graphics Processing Unit (GPU), a Central Processing Unit (CPU), or other chips or circuits having a control function and an image Processing function, and is not limited in particular.
When the system works, the processor 100 may control the light source modulation circuit 140 to modulate the laser group 110 according to image data to be displayed, where the laser group 110 includes a plurality of monochromatic lasers, and the lasers emit light beams of different colors respectively. As shown in fig. 1, three-color lasers of Red (R), Green (G) and Blue (B) can be specifically used in the laser group. The light beams emitted by the lasers in the laser group 110 are combined into a laser beam by the beam combining unit 160 and coupled into the transmission fiber 130.
The processor 100 can also control the scan driving circuit 150 to drive the fiber scanner in the fiber scanning module 120 to scan and output the light beam transmitted in the transmission fiber 130.
The light beam scanned and output by the optical fiber scanner acts on a certain pixel point position on the surface of the medium, and forms a light spot on the pixel point position, so that the pixel point position is scanned. Under the driving of the optical fiber scanner, the output end of the transmission optical fiber 130 sweeps according to a certain scanning track, so that the light beam moves to the corresponding pixel point position. During actual scanning, the light beam output by the transmission fiber 130 will form a light spot with corresponding image information (e.g., color, gray scale or brightness) at each pixel location. In a frame time, the light beam traverses each pixel position at a high enough speed to complete the scanning of a frame of image, and because the human eye observes the object and has the characteristic of 'visual residual', the human eye cannot perceive the movement of the light beam at each pixel position but sees a frame of complete image.
With continued reference to fig. 1b, a specific structure of the fiber scanning module 120 is shown, which includes: scanning actuator 121, fiber suspension 122, mirror group 123, scanner package 124 and fixing member 125. The scanning actuator 121 is fixed in the scanner packaging case 124 through a fixing member 125, and the transmission fiber 130 extends at the front end of the scanning actuator 121 to form a fiber suspension 122 (also called a scanning fiber), so that, in operation, the scanning actuator 121 is driven by a scanning driving signal, the slow axis 121a (also called as the first actuating portion) vibrates along the vertical direction (the vertical direction is parallel to the Y axis in the reference coordinate system in fig. 1a and 1b, and in this application, the vertical direction may also be called as the first direction), the fast axis 121b (also called as the second actuating portion) vibrates along the horizontal direction (the horizontal direction is parallel to the X axis in the reference coordinate system in fig. 1a and 1b, and in this application, the horizontal direction may also be called as the second direction), and is driven by the scanning actuator 121, the front end of the fiber cantilever 122 performs two-dimensional scanning according to a predetermined track and emits a light beam, and the emitted light beam can realize scanning imaging through the lens assembly 123. In general, the structure formed by the scan actuator 121 and the fiber suspension 122 can be referred to as: an optical fiber scanner.
As shown in fig. 2, in the embodiment of the present application, the movement locus of the light exit end of the optical fiber forms a scanning curved surface 230 through the movement of the fast and slow axes, and is converted into an imaging plane 240 after passing through the corresponding mirror group 123. When applied in a near-eye display device such as an Augmented Reality (AR) device, the imaging plane 240 couples the entrance pupil as a waveguide into the waveguide for imaging for viewing by the human eye.
For convenience of description and to make those skilled in the art easily understand the solution of the present application, it should be noted that the optical imaging lens assembly (such as the lens assembly 123 shown in fig. 2) in the present application is used as an eyepiece, and under the action of the optical imaging lens assembly, the scanning curved surface 230 can be converted into an imaging plane 240 (in practical application, the transmission direction of light is from the scanning curved surface 230 to the imaging plane 240), so that one side of the optical imaging lens assembly corresponding to the imaging plane 240 is referred to as a first side, and one side of the optical imaging lens assembly corresponding to the scanning curved surface 230 is referred to as a second side. In the following, embodiments of the optical imaging lens group will be described with reference to "the first side" and "the second side". Also, in the description of the subsequent embodiments, such as for a certain lens in the optical imaging lens group, the "first side surface of the X-th lens" refers to a surface of the X-th lens facing the first side.
Optical imaging lens group
The optical imaging lens group in the embodiment of the application comprises: the lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens which are arranged in sequence from a first side to a second side in a coaxial way, and the total number of the lenses is six.
In one possible embodiment, there is a space between the first lens and the second lens, between the second lens and the third lens, and between the fifth lens and the sixth lens, without bonding. That is, the first lens, the second lens and the sixth lens may be three single non-cemented lenses. The third lens, the fourth lens and the fifth lens may or may not be bonded, and will be determined according to the needs of the practical application, and are not limited herein.
The first lens is a biconvex lens, that is, the first side surface and the second side surface of the first lens are convex surfaces. The refractive index satisfies 1.5< n1<1.7, where n1 is the refractive index of the first lens.
The first side surface of the second lens element is concave at paraxial region and the second side surface is convex. The refractive index satisfies 1.5< n2<1.8, where n2 is the refractive index of the second lens.
The first side surface of the sixth lens element is convex and the second side surface is concave at paraxial region. The refractive index satisfies 1.8< n6<2.0, where n6 is the refractive index of the sixth lens.
For the optical imaging lens group in the embodiment of the present application, under the condition that the surface type structures and the arrangement positions of the first lens element, the second lens element and the sixth lens element are determined, the third lens element, the fourth lens element and the fifth lens element may be arranged according to the first lens element, the second lens element and the sixth lens element (the surface type, the focal length, the refractive index and other parameters of the third lens element, the fourth lens element and the fifth lens element will be exemplified in the following embodiments), so as to form several different optical imaging lens groups.
In the embodiment of the application, the overall length L of the optical imaging lens group is less than or equal to 15 mm. It should be noted that the overall length of the optical imaging lens group is the maximum length from the first side surface of the first lens element to the second side surface of the sixth lens element. In some embodiments, the surface shape of the lens is not concave or convex on the entire side, and the surface shape of the lens may be a compound curve, or a curve near the optical axis and a non-curve on the edge (refer to the sixth lens element 16 in fig. 3), so that the calculation of the total length of the imaging lens assembly requires the calculation of the maximum length from the first side surface of the first lens element to the second side surface of the sixth lens element.
In the embodiment of the present application, the first side surface is a convex surface, which means that the first side surface forms a convex shape toward the first side direction of the optical imaging lens group; the first side surface is a concave surface, which means that the first side surface forms a concave shape towards the first side direction of the optical imaging lens group; the second side surface is a convex surface, which means that the second side surface forms a convex shape towards the second side direction of the optical imaging lens group; the second side surface is a concave surface, which means that the second side surface forms a concave shape towards the second side direction of the optical imaging lens group.
In the embodiment of the application, the focal length of each lens in the six lenses in the optical imaging lens group is set, so that the focal power of the system can be reasonably dispersed, various aberrations can be corrected, a small number of lenses can be used, and clear imaging of the curved surface of the image side can be realized on the premise of ensuring small size.
Example one
Fig. 3 is a schematic structural diagram of an optical imaging lens assembly according to an embodiment of the present invention. The optical imaging lens group comprises a first lens 11, a second lens 12, a third lens 13, a fourth lens 14, a fifth lens 15 and a sixth lens 16 which are coaxially arranged in sequence from a first side (i.e. the side where the imaging plane 01 in fig. 3 is located) to a second side (i.e. the side where the scanning curved surface 02 in fig. 3 is located).
In this embodiment, each two adjacent lenses of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, and the sixth lens 16 have a space therebetween, and the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, and the sixth lens 16 are six single non-cemented lenses.
The focal lengths of the first lens 11 to the sixth lens 16 from the first side to the second side are positive, negative, positive, and negative in sequence.
The first lens 11 is a biconvex lens, i.e., its first and second side surfaces are convex.
The second lens element 12 is a positive meniscus lens element, and the first side surface of the second lens element 12 is concave at the paraxial region and the second side surface is convex.
The first side surface of the third lens 13 is a flat surface, and the second side surface is a concave surface.
The first side surface of the fourth lens element 14 is a flat surface, and the second side surface is a convex surface.
The fifth lens 15 is a biconvex lens.
The sixth lens element 16 is a negative meniscus lens element, and the first side surface of the sixth lens element 16 is convex and the second side surface is concave at a paraxial region.
In the present embodiment, the focal lengths of the first lens element 11 to the sixth lens element 16 in the optical imaging lens group satisfy the following relations:
1.5<f1/f<3,
7<f2/f<9,
0.5<|f3/f|<1.5,
1<f4/f<2,
1<f5/f<1.5,
1<|f6/f|<1.5,
wherein f is an equivalent focal length of the optical imaging lens assembly, f1 is a focal length of the first lens element 11, f2 is a focal length of the second lens element 12, f3 is a focal length of the third lens element 13, f4 is a focal length of the fourth lens element 14, f5 is a focal length of the fifth lens element 15, and f6 is a focal length of the sixth lens element 16.
The refractive indexes of the first lens 11 to the sixth lens 16 in the optical imaging lens group satisfy the following conditions:
1.5<n1<1.7,
1.5<n2<1.8,
1.85<n3<2.0,
1.7<n4<1.9,
1.65<n5<1.8,
1.8<n6<2.0。
where n1 to n6 represent refractive indices of the first lens 11 to the sixth lens 16, respectively.
In the optical imaging lens group provided by the embodiment of the invention, the material of the lens can be glass, plastic or other materials. Preferably, the lens is made of glass, so that the degree of freedom of the refractive power configuration can be increased. In this embodiment, glass is mainly used as an example for lenses in the optical imaging lens group, and glasses with different refractive indexes can be used for different lenses in the optical imaging lens group.
In this embodiment, the equivalent focal length of the optical imaging lens group is 3mm, and the preferred parameters of the curvature radius, the thickness parameter and the refractive index of each lens for imaging a scanning curved surface (taking a spherical surface as an example) are shown in table 1:
TABLE 1
In table 1, the total optical length of the optical imaging lens assembly, i.e. the distance between the image plane 01 and the second side surface of the sixth lens element 16, is 12.852mm, and each of the lens elements is made of glass and is a ball lens. The design of the ball lens is beneficial to the processing of the lens; in practice, aspheric lenses may also be used, with the relevant parameters or proportions still satisfying the foregoing. The optical surface with "infinite" radius of curvature in the imaging plane 01 is referred to as a plane.
Wherein L1 is the distance from the imaging plane 01 to the first side surface of the first lens 11, L2 is the thickness of the first lens 11, and L3 is the distance from the second side surface of the first lens 11 to the first side surface of the second lens 12 on the optical axis; l4 is the thickness of the second lens 12, and L5 is the separation distance on the optical axis from the second side surface of the second lens 12 to the first side surface of the third lens 13; l6 is the thickness of the third lens 13, and L7 is the separation distance on the optical axis from the second side surface of the third lens 13 to the first side surface of the fourth lens 14; l8 is the thickness of the fourth lens 14, and L9 is the separation distance on the optical axis from the second side surface of the fourth lens 14 to the first side surface of the fifth lens 15; l10 is the thickness of the fifth lens 15, and L11 is the separation distance on the optical axis from the second side surface of the fifth lens 15 to the first side surface of the sixth lens 16; l12 is the thickness of the sixth lens 16; l13 is the distance between the second side surface of the sixth lens 16 and the optical axis of the curved scanning surface 02.
Through tests, when the optical imaging lens group is adopted to project image light corresponding to a scanning surface, an optical transfer function curve graph is shown in fig. 4, and a field curvature distortion curve graph is shown in fig. 5; wherein, the Modulation Transfer Function (MTF) represents the comprehensive resolution level of an optical system, and the field distortion curve represents the F-tan (theta) distortion value (percentage) under different field angles.
As can be seen from the MTF curve of the optical imaging lens group shown in fig. 4: the MTF at the center at 200lp/mm is more than 0.5, the MTFs at the edges at 200lp/mm are all more than 0.3, and the imaging resolution is good in the full-field range. As can be seen from the field curvature distortion curve shown in fig. 5: the distortion value of the optical system of the optical imaging lens group is less than 2%, and the distortion is good in the full view field range, so that the optical imaging lens group can clearly image the scanning curved surface image of the optical fiber scanner, and the optical imaging lens group has a good imaging effect.
Certainly, in practical applications, the optical imaging lens assembly may further include a photosensitive element, a housing, and the like, the photosensitive element may be disposed at the second side of the optical imaging lens assembly, and the optical imaging lens assembly may be mounted in the housing, so that a curved image formed by scanning an image source (such as an optical fiber scanner) may be imaged on a plane, thereby realizing clear imaging.
Example two
Fig. 6 is a schematic structural diagram of another optical imaging lens assembly according to an embodiment of the present invention. The optical imaging lens group comprises a first lens 31, a second lens 32, a third lens 33, a fourth lens 34, a fifth lens 35 and a sixth lens 36 which are coaxially arranged in sequence from a first side (i.e. the side where the imaging plane 03 is located in fig. 6) to a second side (i.e. the side where the scanning curved surface 04 is located in fig. 6).
In the present embodiment, each two adjacent lenses of the first lens 31, the second lens 32, the third lens 33, and the sixth lens 36 have a space therebetween, and the first lens 31, the second lens 32, the third lens 33, the fourth lens 34, the fifth lens 35, and the sixth lens 36 are all non-cemented lenses.
The focal lengths of the first lens 31 to the sixth lens 36 from the first side to the second side are positive, negative, positive, and positive in sequence.
The first lens 31 is a biconvex lens, i.e., its first and second side surfaces are convex.
The second lens element 32 is a negative meniscus lens element, and the first side surface of the second lens element 32 is concave at the paraxial region and the second side surface is convex.
The first side surface of the third lens 33 is a flat surface or a convex surface, and the second side surface is a convex surface.
The first side surface of the fourth lens 34 is convex and the second side surface is concave.
The fifth lens 35 is a biconvex lens.
The sixth lens element 36 is a positive meniscus lens element, and the first side surface of the sixth lens element 36 is convex and the second side surface is concave at the paraxial region.
In the present embodiment, the focal lengths of the first lens element 31 to the sixth lens element 36 in the optical imaging lens group satisfy the following relations:
1.5<f1/f<3,
8<|f2/f|<20,
2<f3/f<3,
0.8<|f4/f|<1.5,
1<f5/f<1.8,
7<f6/f<12,
wherein f is an equivalent focal length of the optical imaging lens assembly, f1 is a focal length of the first lens element 31, f2 is a focal length of the second lens element 32, f3 is a focal length of the third lens element 33, f4 is a focal length of the fourth lens element 34, f5 is a focal length of the fifth lens element 35, and f6 is a focal length of the sixth lens element 36.
The refractive indexes of the first lens 31 to the sixth lens 36 in the optical imaging lens group satisfy the following conditions:
1.5<n1<1.7,
1.5<n2<1.8,
1.6<n3<1.8,
1.9<n4<2.0,
1.75<n5<1.9,
1.8<n6<2.0,
where n1 to n6 represent refractive indices of the first lens 31 to the sixth lens 36, respectively.
In the optical imaging lens group provided by the embodiment of the invention, the material of the lens can be glass, plastic or other materials. Preferably, the lens is made of glass, so that the degree of freedom of the refractive power configuration can be increased. In this embodiment, glass is mainly used as an example for lenses in the optical imaging lens group, and glasses with different refractive indexes can be used for different lenses in the optical imaging lens group.
In this embodiment, the equivalent focal length of the optical imaging lens group is 3.13mm, and the preferred parameters of the curvature radius, thickness parameter and refractive index of each lens for imaging a scanning curved surface (taking a spherical surface as an example) are shown in table 2:
TABLE 2
In table 2, the total optical length of the optical imaging lens assembly, i.e. the distance between the image plane 03 and the second side surface of the sixth lens element 36, is 12.319mm, and each of the lens elements is made of glass and is a ball lens. The design of the ball lens is beneficial to the processing of the lens; in practice, aspheric lenses may also be used, with the relevant parameters or proportions still satisfying the foregoing. The optical surface of the imaging plane 03 with "infinite" radius of curvature is referred to as a plane.
Wherein L1 is the distance from the imaging plane 03 to the first side surface of the first lens 31, L2 is the thickness of the first lens 31, and L3 is the distance from the second side surface of the first lens 31 to the first side surface of the second lens 32 on the optical axis; l4 is the thickness of the second lens 32, and L5 is the separation distance on the optical axis from the second side surface of the second lens 32 to the first side surface of the third lens 33; l6 is the thickness of the third lens 33, and L7 is the separation distance on the optical axis from the second side surface of the third lens 33 to the first side surface of the fourth lens 34; l8 is the thickness of the fourth lens 34, and L9 is the separation distance on the optical axis from the second side surface of the fourth lens 34 to the first side surface of the fifth lens 35; l10 is the thickness of the fifth lens 35, and L11 is the separation distance on the optical axis from the second side surface of the fifth lens 35 to the first side surface of the sixth lens 36; l12 is the thickness of the sixth lens 36; l13 is the distance from the second side surface of the sixth lens 36 to the optical axis of the scanning curved surface 04.
Through tests, when the optical imaging lens group is used for projecting image light corresponding to a scanning surface, the graph of the optical transfer function is shown in fig. 7, and the graph of the field curvature distortion is shown in fig. 8.
As can be seen from the MTF curve of the optical imaging lens group shown in fig. 7: the MTF at the center at 200lp/mm is more than 0.6, the MTFs at the edges at 200lp/mm are all more than 0.3, and the imaging resolution in the full-field range is good. As can be seen from the field curvature distortion curve shown in fig. 8: the distortion value of the optical system of the optical imaging lens group is less than 2%, and the distortion is good in the full view field range, so that the optical imaging lens group can clearly image the scanning curved surface image of the optical fiber scanner, and the optical imaging lens group has a good imaging effect.
Scanning display device
The optical imaging lens group can cooperate with an optical fiber scanner (or a corresponding optical fiber scanning module) to form a scanning display device in the embodiment of the present application (as shown in fig. 1a and 1b, the optical imaging lens group is disposed on a light emitting path of the optical fiber scanner), wherein a first side of the optical imaging lens group faces a light emitting direction of the optical fiber scanner, and a preferred mode is that the optical imaging lens group is coaxial with a central optical axis of the optical fiber scanner. Of course, reference may be made to the corresponding contents in fig. 1a and 1b for the structure and the general principle of the fiber scanner, and redundant description is omitted here.
Near-to-eye display device
In the present application, the scanning display device can be further applied to a near-eye display device, and can be used as a head-mounted AR device (e.g., AR glasses) in cooperation with a near-eye display module to form the near-eye display device in the embodiment of the present application. The scanning display device is arranged in the near-eye display module.
Wherein, can include among the near-to-eye display module assembly: light source, processing control circuit, wearable frame structure, waveguide, etc. The image light beam output by the light source enters the scanning display device, and is scanned and output to the optical display mirror group by the optical fiber scanner, the scanning curved surface (refer to the scanning curved surface 02 in fig. 3 and the scanning curved surface 04 in fig. 6) of the optical fiber scanner passes through the optical display mirror group and is converted into an imaging plane (refer to the imaging plane 01 in fig. 3 and the imaging plane 03 in fig. 6), and the imaging plane is coupled into the waveguide as the entrance pupil surface of the waveguide, and is coupled out through waveguide expansion imaging and enters human eyes.
As another possible implementation manner, the scanning display device may further cooperate with the near-eye display module to form a near-eye display device in the embodiment of the present application, and serve as a head-mounted VR device (e.g., VR headset/glasses). The scanning display device is arranged in the near-eye display module.
The above embodiments are merely preferred embodiments of the present application, and the embodiments are only used for illustrating the technical solutions of the present application and not for limiting the present application, and all technical solutions that can be obtained by a person skilled in the art through logic analysis, reasoning or effective experiments according to the concepts of the present application should be within the scope of the present application.
In the embodiment of the application, the surface types and the focal lengths of six coaxial lenses of the optical imaging lens group are reasonably and optimally set, so that the focal power of the system can be reasonably dispersed, the aberration generated by the lenses can be reduced, a small number of lenses can be used, various aberrations can be corrected, and clear imaging of the image side curved surface can be realized. Meanwhile, the whole length of the optical imaging lens group is smaller than or equal to 15mm, the focal length of the optical imaging lens group can be larger than or equal to 3mm, the imaging requirement of high resolution can be met while the miniaturization of the system is realized, and the optical imaging lens group is suitable for near-to-eye display equipment which is miniaturized, light and convenient and has continuously improved imaging definition requirements.
The embodiments in the present application are described in a progressive manner, and the same and similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The expressions "first", "second", "said first" or "said second" used in various embodiments of the present disclosure may modify various components regardless of order and/or importance, but these expressions do not limit the respective components. The above description is only configured for the purpose of distinguishing elements from other elements. For example, the first lens and the second lens represent different lenses, although both are lenses.
Claims (10)
1. An optical imaging lens group, comprising a first lens element to a sixth lens element coaxially disposed in sequence from a first side to a second side,
the first side surface of the first lens is a convex surface, and the second side surface of the first lens is a convex surface; a first side surface of the second lens is concave at a paraxial region, and a second side surface of the second lens is convex; the first side surface of the sixth lens element is convex and the second side surface of the sixth lens element is concave at paraxial region.
2. The optical imaging lens assembly of claim 1 wherein the refractive index of said first lens element is such that:
1.5<n1<1.7;
wherein n1 is the refractive index of the first lens.
3. The optical imaging lens assembly of claim 1 wherein the refractive index of said second lens element is such that:
1.5<n2<1.8;
wherein n2 is the refractive index of the second lens.
4. The optical imaging lens group of claim 1, wherein the refractive index of the sixth lens element satisfies the following:
1.8<n6<2.0;
wherein n6 is a refractive index of the sixth lens.
5. The optical imaging lens group of any one of claims 1 to 4, wherein the overall length of the optical imaging lens group is less than or equal to 15 mm.
6. The optical imaging lens group of claim 5, wherein the overall length of the optical lens group is the maximum length from the first side surface of the first lens element to the second side surface of the sixth lens element.
7. The optical imaging lens group of claim 1 wherein the second side of the optical imaging lens group corresponds to a curved image.
8. A scanning display device, comprising an optical fiber scanner and the optical imaging lens group of any one of the preceding claims 1 to 7, wherein the optical fiber scanner is used for scanning and emitting light of an image to be displayed, and the optical imaging lens group is used for magnifying, imaging and projecting a scanning surface corresponding to the light emitted by the optical fiber scanner;
the optical fiber scanner comprises an actuator and an optical fiber fixed on the actuator, wherein a part of the optical fiber, which exceeds the actuator, forms an optical fiber cantilever, and the optical fiber cantilever is driven by the actuator to perform two-dimensional scanning.
9. A near-eye display apparatus, wherein the near-eye display apparatus is used as a head-mounted augmented reality apparatus, and comprises at least a near-eye display module and the scanning display device according to claim 8, and the scanning display device is disposed in the near-eye display module.
10. A near-eye display apparatus, wherein the near-eye display apparatus is used as a head-mounted virtual reality apparatus, and comprises at least a near-eye display module and the scanning display device according to claim 8, and the scanning display device is disposed in the near-eye display module.
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