CN112817122B - Projection objective and scanning display device - Google Patents
Projection objective and scanning display device Download PDFInfo
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- CN112817122B CN112817122B CN201911129878.4A CN201911129878A CN112817122B CN 112817122 B CN112817122 B CN 112817122B CN 201911129878 A CN201911129878 A CN 201911129878A CN 112817122 B CN112817122 B CN 112817122B
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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
- 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
- G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
- G02B13/006—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element at least one element being a compound optical element, e.g. cemented elements
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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
- G02B13/16—Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
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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
Abstract
The invention relates to a projection objective and a scanning display device, which are used for solving the problem of arc-shaped image surface imaging and realizing clear imaging. The projection objective comprises: a first lens group and a second lens group coaxially arranged in sequence from an object side to an image side; the first lens group comprises 6 lenses from the first lens to the sixth lens which are arranged in sequence on a common optical axis and have positive, negative, positive and positive focal lengths in sequence; the second lens group comprises 5 lenses from a seventh lens to an eleventh lens which are arranged in sequence on a common optical axis and have negative, positive and positive focal lengths in sequence; the seventh lens element and the eighth lens element form a double-cemented lens element with a convex surface facing the image side; the object side surface of the eleventh lens is a convex surface, and the image side surface of the eleventh lens is a concave surface; wherein, the object side curvature radius of the first lens is R1, the image side curvature radius is R2, the equivalent focal length of the second, third and fourth lenses is F3, the equivalent focal length of the fifth and sixth lenses is F4, which satisfies the relation: 1< R1/R2<1.4, and 4< | F4/F3| < 10.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to a projection objective and a scanning display device.
Background
The imaging principle of the optical fiber scanning projection technology is as follows: the actuator drives the scanning optical fiber to move along a preset two-dimensional scanning track, the light emitting power of the light source is modulated, and information of each pixel point of an image to be displayed is projected onto an imaging area one by one, so that a projection picture is formed.
Fig. 1A and 1B are schematic structural diagrams of a conventional fiber scanning projection system, wherein fig. 1B is a side view of fig. 1A. The fiber scanner projection system includes: the optical fiber scanning device comprises a processor 100, a laser unit 110, a fiber scanner 120, an optical fiber 130, a light source modulation module 140, a scanning driving module 150 and a light source beam combining module 160. The fiber scanner 120 includes an actuator 121, a base 125, and a housing 124, and the fiber 130 is fixed on the actuator 120, and a portion beyond the actuator 121 forms a fiber suspension 122. In operation, the processor 100 controls the fiber scanner 120 to perform the vibration scanning by sending an electrical control signal to the scan driving module 150, and at the same time, the processor 100 controls the light output power of the beam combining module 160 by sending an electrical control signal to the light source modulation module 140. The light source modulation module 140 outputs a light source modulation signal according to the received electrical control signal to modulate one or more color laser units 110 in the light source beam combining module 160, which is shown to include red (R), green (G), and blue (B) three-color lasers; the light generated by the laser unit 110 of each color in the light source beam combining module 160 is combined to generate color and gray information of each pixel point one by one, and the combined light beam emitted by the light source beam combining module is guided into the optical fiber scanner through the optical fiber. Synchronously, the scan driving circuit 150 outputs a scan driving signal according to the received electrical control signal to control the optical fiber 130 in the optical fiber scanner 120 to perform a scanning motion in a predetermined two-dimensional scanning trajectory to scan out the light beam transmitted in the transmission optical fiber 130.
The projection objective is used to image an arc-shaped pattern at the image plane of the projection objective onto the object plane of the projection objective, and is typically arranged in the exit optical path of the exit end of the optical fiber in the fiber scanner, as indicated by reference numeral 123 in fig. 1B. However, since the image plane scanned by the fiber scanner is a curved surface, and the image plane of the conventional projection objective (i.e. the image plane of the image source) is generally a flat surface, the conventional projection objective cannot clearly image the curved image scanned by the fiber scanner.
Disclosure of Invention
The embodiment of the invention aims to provide a projection objective and a scanning display device, which are used for solving the problem of arc-shaped image surface imaging in an optical fiber scanning projection system and realizing clear imaging.
In order to achieve the above object, according to a first aspect, the present invention provides a projection objective comprising a first lens group and a second lens group coaxially disposed in order from an object side to an image side;
the first lens group comprises 6 lenses including a first lens, a second lens, a third lens and a fourth lens, wherein the first lens, the second lens, the third lens and the fourth lens are sequentially arranged from an object side to an image side, and focal lengths of the first lens, the second lens, the third lens and the fourth lens are sequentially positive, negative, positive and positive; the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;
the second lens group comprises 5 lenses including a seventh lens, a eleventh lens and a fourth lens, wherein the seventh lens, the eleventh lens and the fourth lens are sequentially arranged from the object side to the image side, and focal lengths of the seventh lens, the eleventh lens and the fourth lens are sequentially negative, positive and positive; the seventh lens element is a biconcave lens element, the eighth lens element is a biconvex lens element, and the seventh lens element and the eighth lens element form a double cemented lens element with a convex surface facing the image side; the object side surface of the eleventh lens is a convex surface, and the image side surface of the eleventh lens is a concave surface;
wherein the radius of curvature of the object side surface of the first lens is R1, the radius of curvature of the image side surface of the first lens is R2, the equivalent focal lengths of the second lens, the third lens and the fourth lens are F3, and the equivalent focal lengths of the fifth lens and the sixth lens are F4, which satisfy the following relations:
1< R1/R2< 1.4; and
4<|F4/F3|<10。
optionally, the object-side surface of the second lens element is a convex surface, and the image-side surface of the second lens element is a concave surface; the third lens and the fourth lens are both biconcave lenses, the image side surface of the fifth lens is a convex surface, and the sixth lens is a biconvex lens.
Optionally, a distance between an object side surface of the first lens and an image plane of the projection objective is less than 4.5 cm.
Optionally, the following relation is also satisfied:
1.7<N1<1.9，
1.8<N2<2.0，
1.85<N3<2.0，
1.46<N4<1.65，
1.8<N5<2.0，
1.46<N6<1.65，
1.85<N7<2.0，
1.46<N8<1.65，
1.46<N9<1.65，
1.46<N10<1.65，
1.65<N11<1.85，
wherein N1 is a refractive index of the first lens, N2 is a refractive index of the second lens, N3 is a refractive index of the third lens, N4 is a refractive index of the fourth lens, N5 is a refractive index of the fifth lens, N6 is a refractive index of the sixth lens, N7 is a refractive index of the seventh lens, N8 is a refractive index of the eighth lens, N9 is a refractive index of the ninth lens, N10 is a refractive index of the tenth lens, and N11 is a refractive index of the eleventh lens.
Optionally, the second lens and the fifth lens are made of the same material.
Optionally, the third lens and the seventh lens are made of the same material.
Optionally, the fourth lens, the sixth lens, the eighth lens, the ninth lens, and the tenth lens are made of the same material.
Optionally, the projection objective further includes a diaphragm disposed between the sixth lens and the seventh lens in a coaxial manner.
Optionally, on the optical axis, a distance between an image side surface of the sixth lens and the stop is T1, a distance between the stop and an object side surface of the seventh lens is T2, and the relationship is satisfied: t1< T2.
Optionally, the projection objective further comprises: and the parallel flat plate is positioned between the eleventh lens and the image surface of the projection objective, shares the same optical axis with the eleventh lens, and is used for protecting the projection objective.
In a second aspect, an embodiment of the present invention provides a scanning display device, including an optical fiber scanner and the projection objective of any one of claims 1 to 10 corresponding to the optical fiber scanner, wherein the optical fiber scanner includes an actuator and an optical fiber fixed on the actuator, and a portion of the optical fiber beyond the actuator forms an optical fiber cantilever; wherein the actuator comprises a first actuation portion and a second actuation portion connected to the first actuation portion; under the action of a driving signal, the first actuating part moves in a first direction, the second actuating part drives the first actuating part to move in a second direction, the optical fiber cantilever moves in the direction which is the combination of the first direction and the second direction, and the movement frequency of the first actuating part is greater than or equal to that of the second actuating part.
Optionally, the curvature radius corresponding to the scanning track of the optical fiber driven by the actuator in the first direction is [2.0mm, 2.3mm ], the scanning radius in the second direction is [2.3mm, + ∞ ], and the equivalent focal length of the projection objective lens is 2 mm.
The specific technical scheme provided in the embodiment of the invention is as follows:
in an embodiment of the present invention, the projection objective includes 11 first to eleventh lenses, each of which has a focal length of positive, negative, positive, and positive, wherein the first to eleventh lenses are arranged on a same optical axis in order from an object side to an image side, the first to sixth lenses are a first lens group, and the seventh to eleventh lenses are a second lens group; the first lens is a meniscus lens with a convex surface facing the object side, the sixth lens is a biconvex lens, the seventh lens is a biconcave lens, the eighth lens is a biconvex lens, the seventh lens and the eighth lens form a double-cemented lens with a convex surface facing the image plane, and the image side surface of the eleventh lens is a concave surface; the focal length of the first lens group is F1, the focal length of the second lens group is F2, and 1.5< F1/F2<2.0, so that the focal power of the system can be effectively dispersed, the aberration generated by each lens can be reduced, and clear imaging can be realized.
Drawings
FIGS. 1A-1B are schematic structural diagrams of a conventional optical fiber scanning projection system;
fig. 2 is a schematic diagram of a structure and an image of a projection objective according to an embodiment of the present invention (fast axis scanning direction);
FIG. 3 is a schematic imaging diagram (slow axis scanning direction) of a projection objective provided by an embodiment of the present invention;
fig. 4A to 7B are MTF graphs and distortion graphs when a projection objective images different fiber scanners according to an 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 only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The projection objective lens provided by the embodiment of the invention is used for imaging the arc-shaped pattern on the image surface of the projection objective lens onto the object surface of the projection objective lens so as to solve the problem of arc-shaped image surface imaging. Wherein, the arc-shaped pattern of the image surface is an arc-shaped scanning surface scanned by the fiber scanner shown in fig. 1A-1B or emitted by other image sources; the object plane is a projection screen, a curtain or a wall surface.
First, a scanning display device to which the projection objective is applied in the embodiment of the present invention will be described for the understanding of those skilled in the art.
The scanning display device in the embodiment of the invention comprises an optical fiber scanner and the projection objective lens corresponding to the optical fiber scanner, and the wavelength range of the device which can act at least comprises 400nm-700 nm. The optical fiber scanner comprises an optical fiber and an actuator, wherein the optical fiber is fixed on the actuator, and the part of the optical fiber, which exceeds the actuator, forms an optical fiber cantilever. The actuator comprises a fast-axis actuating part and a slow-axis actuating part connected with the fast-axis actuating part, wherein the fast-axis actuating part and the slow-axis actuating part are connected together by gluing, embedding and fixing, adding a fixed structure and the like, or the actuator can be integrally formed; the shape of the integrally formed actuator can be a sheet shape, a column shape, or a combination of the two, wherein the column shape includes a cylindrical shape and a square column shape, such as a round rod (tube) and a square rod (tube). The driving frequency of the fast axis actuating part is more than or equal to that of the slow axis actuating part. Under the action of a driving signal, the fast axis actuating part scans in a first direction, the slow axis actuating part drives the fast axis actuating part to scan in a second direction, and the actuator drives the optical fiber cantilever to scan in a predetermined two-dimensional scanning track in a synthesis direction of the first direction and the second direction, such as a grid scanning mode, a spiral scanning mode and the like, so as to form an arc-shaped scanning surface (corresponding to an image surface of the projection objective lens). Preferably, the first direction is an X direction and the second direction is a Y direction.
In practical application, the scanning track corresponding to the optical fiber in the optical fiber scanner can be controlled by controlling the driving signal of the optical fiber scanner. In the embodiment of the invention, the curvature radius corresponding to the scanning track of the optical fiber scanner in the fast axis direction (X direction) can be controlled within the range of [2.0mm, 2.3mm ], the curvature radius corresponding to the scanning track in the slow axis direction (Y direction) is more than or equal to 2.3mm, and the correspondingly formed arc-shaped scanning surface is the image surface of the projection objective; when the curvature radius of the scanning track in the slow axis direction is "+ ∞", it is shown that the radian of the scanning track in the Y direction in the arc image surface tends to be a straight line, and at this time, the scanning surface is similar to a cylindrical surface. Because the light-emitting facula of the optical fiber in the optical fiber scanner is small, namely the pixel unit of the light-emitting surface is small, the lens is required to have higher resolution so as to realize clear imaging of the arc-shaped scanning surface emitted by the optical fiber scanner.
Next, a projection objective lens in an embodiment of the present invention will be described.
Fig. 2 is a schematic structure of a projection objective according to an embodiment of the present invention. The projection objective comprises a first lens group and a second lens group which are arranged on the same optical axis in sequence from an object side to an image side; the first lens group comprises 6 lenses including a first lens 1 to a sixth lens 6 which are arranged from an object side to an image side in sequence and have positive focal lengths, a negative focal lengths, a positive focal lengths and a positive focal lengths; the object side surface 11 of the first lens element 1 is convex, and the image side surface 12 is concave; the second lens group comprises 5 lenses including a seventh lens 7 to an eleventh lens 11 which are sequentially arranged from the object side to the image side and have negative, positive and positive focal lengths in sequence; the seventh lens element 7 is a biconcave lens element, the eighth lens element 8 is a biconvex lens element, and the seventh lens element 7 and the eighth lens element 8 form a double cemented lens element with a convex surface facing the image side; the object-side surface 111 of the eleventh lens element 11 is convex, and the image-side surface 112 is concave. In the projection objective, focal lengths of all lenses are set, so that focal power of a system can be reasonably dispersed, aberration generated by the lenses is reduced, and clear imaging of an arc-shaped image surface is realized.
The term "object-side to image-side" as used herein refers to the direction from the object plane 01 to the image plane 02 in fig. 2; the object side surface is a convex surface, which means that the object side surface faces the object surface 01 of the projection objective to form a convex shape; the object side surface is a concave surface, which means that the object side surface faces the object surface 01 to form a concave shape; the image side surface is convex, namely the image side surface faces the image surface 02 of the projection objective and is convex; the image side surface is concave, and is recessed toward the image plane 02.
In the embodiment of the invention, the focal length of the first lens group is F1, and the focal length of the second lens group is F2, which satisfy the relation: 1.5< F1/F2< 2.0. Preferably, 1.75< F1/F2<1.89, so as to disperse the optical power of the system and relieve the aberration generated by each lens.
In practical applications, the first lens 1 is a meniscus lens with a convex surface facing the object side, and can focus light into the lens. The curvature radius of the object side surface 11 of the first lens 1 is R1, and the curvature radius of the image side surface 12 of the first lens 1 is R2, which satisfy the following relation: 1.4> R1/R2> 1. The radius of curvature is within the ratio, and the first lens 1 can effectively focus light in a required field of view to the lens.
In the embodiment of the present invention, the object-side surface 21 of the second lens element 2 with negative focal length is convex, and the image-side surface 22 is concave; the third lens 3 and the fourth lens 4 with negative focal length are both biconcave lenses, the object side surface 31 and the image side surface 32 of the third lens 3 are both concave surfaces, and the object side surface 41 and the image side surface 42 of the fourth lens 4 are both concave surfaces; the object side surface 51 of the fifth lens element 5 with positive focal length is a plane, and the image side surface 52 is a convex surface; the sixth lens element 6 is a biconvex lens element, and has a convex object-side surface 61 and a convex image-side surface 62.
In an alternative embodiment, the equivalent focal length of the second lens 2, the third lens 3 and the fourth lens 4 is F3, and the equivalent focal length of the fifth lens 5 and the sixth lens 6 is F4, which satisfy the relation: 4< | F4/F3| < 10.
Further, in practical applications, the design structures and the number of lenses of the second lens 2 to the fourth lens 4 may be adjusted based on F3, and/or the design structures and the number of lenses of the fifth lens 5 and the sixth lens 6 may be adjusted based on F4, as long as the equivalent distance between the two lenses can satisfy the aforementioned proportional relationship between F3 and F4, and the light rays can be acted accordingly as required, which is not limited in the present invention.
Preferably, a common-axis stop 12 may be disposed between the sixth lens 6 and the seventh lens 7 to reduce stray light and improve image quality, which is also shown in fig. 2. The diaphragm 12 is of a kind such as an aperture diaphragm, a Field diaphragm (Field Stop), a vignetting diaphragm, or the like. Then, if the distance between the image-side surface 62 of the sixth lens element 6 and the stop 12 on the optical axis is T1 and the distance between the stop 12 and the object-side surface 71 of the seventh lens element 7 on the optical axis is T2, the following relationship is satisfied: t1 is less than T2, and aberration can be effectively corrected. Preferably, 1< T2/T1<8, which makes the system structure of the projection objective more compact.
The object-side surface 71 and the image-side surface 72 of the seventh lens element 7 are both concave, and the object-side surface 81 and the image-side surface 82 of the eighth lens element 8 are both convex; the image side 72 of the seventh lens element 7 is cemented with the object side 81 of the eighth lens element 8, so that the seventh lens element 7 and the eighth lens element 8 form a double cemented lens, and the object side (such as a screen, a wall surface, etc.) of the double cemented lens element is a biconcave lens element, and the image side (i.e. a scanning surface) of the double cemented lens element is a biconvex lens element, which can effectively correct aberration and reduce optical sensitivity. Meanwhile, the ninth lens element 9 has a positive focal length, and the object-side surface 91 may be a plane surface and the image-side surface 92 may be a convex surface; the tenth lens element 10 is a biconvex lens element with a positive focal length, and has a convex object-side surface 101 and a convex image-side surface 102; furthermore, the object-side surface 111 and the image-side surface 112 of the eleventh lens element 11 with positive focal length are convex and concave, so that the optical sensitivity can be effectively reduced.
Since the lens structure has reversibility on the action of light, the effect of the design structure of the projection objective provided by the embodiment of the invention on light can be understood from the direction from the object plane 01 to the image plane 02 as follows: the first lens 1 focuses light rays to the lens, convergent light rays are converted into divergent light rays through the second lens 2, the third lens 3 and the fourth lens 4, the divergent light rays are converged through the fifth lens 5 and the sixth lens 6 and enter the diaphragm 12, main light rays in emergent light rays of the diaphragm 12 are diverged towards two sides through the double cemented lenses, and finally the divergent light rays can be converged on the image plane 02 through the ninth lens 9, the tenth lens 10 and the eleventh lens 11. Therefore, after the light of the arc-shaped image surface 02 is acted by the projection objective, the arc-shaped image emitted by the optical fiber scanner can be clearly amplified and imaged on a plane (namely the object surface 01).
In an alternative embodiment, the projection objective may further comprise a parallel plate 13, which is coaxial with the lens group, and which is arranged between the eleventh lens 11 and the image plane 02, as also shown in fig. 2. The parallel plate 13 may be a transparent material such as glass, plastic, etc. which may be used to protect the lenses in the projection objective, e.g. to avoid scratching the eleventh lens 11 during adjustment of the fiber.
In an embodiment of the present invention, the refractive index of each lens in the projection objective satisfies the following relation:
1.7<N1<1.9，
1.8<N2<2.0，
1.85<N3<2.0，
1.46<N4<1.65，
1.8<N5<2.0，
1.46<N6<1.65，
1.85<N7<2.0，
1.46<N8<1.65，
1.46<N9<1.65，
1.46<N10<1.65，
1.65<N11<1.85，
1.46<NX<1.65，
where N1 is a refractive index of the first lens 1, N2 is a refractive index of the second lens 2, N3 is a refractive index of the third lens 3, N4 is a refractive index of the fourth lens 4, N5 is a refractive index of the fifth lens 5, N6 is a refractive index of the sixth lens 6, N7 is a refractive index of the seventh lens 7, N8 is a refractive index of the eighth lens 8, N9 is a refractive index of the ninth lens 9, N10 is a refractive index of the tenth lens 10, N11 is a refractive index of the eleventh lens 11, and NX is a refractive index of the parallel plate 13.
In the projection objective 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. The description is mainly made by taking glass as an example of the lenses in the projection objective, and different lenses in the projection objective can be made of glass with different refractive index or dispersion parameters.
Preferably, the second lens 2 and the fifth lens 5 can be made of the same material, such as glass material with higher refractive index (e.g. refractive index higher than 1.65) and lower abbe number (e.g. abbe number less than 30); meanwhile, the third lens 3 and the seventh lens 7 may also be made of the same material, such as a glass material with a high refractive index and a low abbe number; further, the same material, for example, a glass material having a low refractive index and a high dispersion coefficient (for example, dispersion coefficient higher than 60) may be used for the fourth lens 4, the sixth lens 6, the eighth lens 8, the ninth lens 9, and the tenth lens 10. In addition, the surface of each lens is spherical, which is beneficial to optical cold processing.
In one embodiment of the present invention, the projection objective has an equivalent focal length of 2mm as a whole, and preferred parameters of the curvature radius, thickness parameter, and pitch of each lens for imaging a light-emitting surface as a cylindrical surface (the curvature radius corresponding to the scanning locus in the fast axis direction is 2mm) are shown in table 1:
TABLE 1
In table 1, the numbers of the radii of curvature of the object-side surface 11 and the image-side surface 12 in the first lens element 1 are R1 and R2, respectively; the curvature radius serial numbers of the object side surface 21 and the image side surface 22 in the second lens 2 are R3 and R4 respectively; the curvature radius numbers of the object side surface 31 and the image side surface 32 of the third lens 33 are R5 and R6 respectively, and the curvature radius numbers of the object side surface 41 and the image side surface 42 of the fourth lens 4 are R7 and R8 respectively; the serial numbers of the curvature radii of the object side surface 51 and the image side surface 52 in the fifth lens 5 are R9 and R10 respectively; the serial numbers of the curvature radii of the object side surface 61 and the image side surface 62 in the sixth lens 6 are R11 and R12 respectively; the curvature radius number of the object side surface 71 of the seventh lens element 7 is R13; the numbers of the radii of curvature of the object-side surface 81 and the image-side surface 82 in the eighth lens 8 cemented with the seventh lens 7 are R14 and R15, respectively; the numbers of the radii of curvature of the object-side surface 91 and the image-side surface 92 in the ninth lens element 9 are R16 and R17, respectively; the tenth lens 10 has the object-side surface 101 and the image-side surface 102 with the respective numbers of radii of curvature R18 and R19; the numbers of the radii of curvature of the object-side surface 111 and the image-side surface 112 in the eleventh lens 11 are R20 and R21, respectively; the object side 131 and the image side 132 of the parallel plate 13 have respective numbers of radii of curvature R22 and R23.
In table 1, the center distance (i.e., the total optical length) between the object-side surface 11 of the first lens 1 and the image plane 02 is 44.39mm as an example. Each lens in the projection objective is made of glass, an optical surface with an infinite (infinity) curvature radius in the lens is a plane, and a distance parameter corresponding to the object plane 0101 is a projection distance of the projection lens, and the projection distance can be set according to actual conditions. Wherein L1 is the thickness of the first lens element 1, and L2 is the distance between the image-side surface 12 of the first lens element 1 and the object-side surface 21 of the second lens element 2 on the optical axis; l3 is the thickness of the second lens 2, and L4 is the distance from the image-side surface 22 of the second lens 2 to the object-side surface 31 of the third lens 3 on the optical axis; l5 is the thickness of the third lens element 3, and L6 is the distance from the image-side surface 32 of the third lens element 3 to the object-side surface 41 of the fourth lens element 4 on the optical axis; l7 is the thickness of the fourth lens element 4, and L8 is the distance from the image-side surface 42 of the fourth lens element 4 to the object-side surface 51 of the fifth lens element 5 on the optical axis; l9 is the thickness of the fifth lens 5, and L10 is the distance between the image-side surface 52 of the fifth lens 5 and the object-side surface 61 of the sixth lens 6 on the optical axis; l11 is the thickness of the sixth lens 6, and L12 is the distance between the image side surface 62 of the sixth lens 6 and the stop 12 on the optical axis; l13 is the thickness of the diaphragm 12; l14 is the thickness of the seventh lens 7; l15 is the thickness of the eighth lens element 8, and L16 is the distance from the image-side surface 82 of the eighth lens element 8 to the object-side surface 91 of the ninth lens element 9 on the optical axis; l17 is the thickness of the ninth lens element 9, and L18 is the distance from the image-side surface 92 of the ninth lens element 9 to the object-side surface 101 of the tenth lens element 10 on the optical axis; l19 is the thickness of the tenth lens 10, and L20 is the distance between the image-side surface 102 of the tenth lens 10 and the object-side surface 111 of the eleventh lens 11 on the optical axis; l21 is the thickness of the eleventh lens 11, and L22 is the distance from the image-side surface 112 of the eleventh lens 11 to the object-side surface 131 of the parallel plate 13 on the optical axis; l23 is the thickness of the parallel plate 13, and L24 is the distance between the image side 132 of the parallel plate 13 and the image plane 02 on the optical axis.
The rear working distance (i.e. the central distance between the image side 132 of the parallel flat plate 13 and the image plane 02) of the projection objective is 3.198 mm; the relative aperture of the projection objective, namely the ratio (D/F ') of the effective entrance pupil focal length (D) to the integral equivalent focal length (F') can be improved to 0.5, and the light energy utilization rate can be effectively improved.
Further, as an embodiment of the present invention, each lens of the projection objective is made of glass, and the focal length of the entire projection objective is 2mm, the preferable parameters of refractive index and dispersion coefficient of each lens are shown in table 2:
TABLE 2
In table 2, the same glass material with higher refractive index and lower dispersion is used for the second lens 2 and the fifth lens 5; the third lens 3 and the seventh lens 7 are made of the same glass material with high refractive index and low dispersion; the fourth lens 4, the sixth lens 6, the eighth lens 8, the ninth lens 9, and the tenth lens 10 are made of glass having a low refractive index and a high dispersion coefficient.
In an actual scanning projection system, when the projection objective is applied to a fiber scanning projection system, if an arc-shaped scanning surface (i.e. the image surface 02 of the projection objective) formed by scanning an optical fiber in an optical fiber scanner has a curvature radius R corresponding to a scanning track in a fast axis directionkAnd R isk∈[2.0mm，2.3mm]The radius of curvature corresponding to the scanning track in the slow axis direction is RmAnd R ismE [2.3mm, + ∞). The arc-shaped pattern (scan surface) emerging from the fiber scanner can then be imaged using the above-mentioned projection objective with an equivalent focal length of 2 mm.
Referring to fig. 2, an imaging process of the light beam scanned and emitted by the optical fiber light-emitting end in the fast axis direction by the projection lens is shown in fig. 3, where the scanning track in the slow axis direction is a straight line (i.e., the curvature radius corresponding to the scanning track is "+ ∞") in fig. 3.
Tested at Rk＝2mm，RmThe optical transfer function graph and distortion graph of the projection objective are shown in fig. 4A and 4B, respectively; the Modulation Transfer Function (MTF) represents the comprehensive resolution level of an optical system, and the distortion curve represents the F-tan (theta) distortion under different angles of view.
Further, at Rk＝2mm，RmWhen the image plane 02 is 2.5mm, please refer to fig. 2 before. The MTF and distortion plots for the projection objective are shown in fig. 5A and 5B, respectively; at Rk＝2.3mm，RmThe MTF plot and distortion plot for the projection objective are shown in fig. 6A and 6B, respectively; at Rk＝2.3mm，RmThe MTF and distortion plots for the projection objective are shown in fig. 7A and 7B, respectively, at 2.3 mm.
As can be seen from the MTF curves of the projection objectives shown in fig. 4A, 5A, 6A: MTFs at 160lp/mm in the center are all larger than 0.3, MTFs at 200lp/mm in the edge are all larger than 0.2, MTFs at the center and the edge of FIG. 7A are all larger than 0.3, and imaging resolution is good; and, as can be seen from the distortion curves shown in fig. 4B, 5B, 6B, and 7B: the absolute value of the distortion of the optical system of the projection objective is less than 2%, and the distortion is good in the full field of view. Therefore, the projection objective can clearly image the optical fiber scanners with the scanning radiuses and has a good imaging effect.
The above embodiments are only preferred embodiments of the present invention, and the embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the present invention, 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 concept of the present invention should be within the scope of the present invention.
In the embodiment of the invention, through setting the focal lengths of the two lens groups of the projection objective in 11 lenses, the focal power of the system can be reasonably dispersed, the aberration generated by the lenses is reduced, and the clear imaging of the arc-shaped image surface is realized.
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
Any feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. That is, unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features.
The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification and any novel method or process steps or any novel combination of features disclosed.
Claims (12)
1. A projection objective is characterized by comprising a first lens group and a second lens group which are coaxially arranged in sequence from an object side to an image side;
the first lens group comprises 6 lenses including a first lens, a second lens, a third lens and a fourth lens, wherein the first lens, the second lens, the third lens and the fourth lens are sequentially arranged from an object side to an image side, and focal lengths of the first lens, the second lens, the third lens and the fourth lens are sequentially positive, negative, positive and positive; the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;
the second lens group comprises 5 lenses including a seventh lens, a eleventh lens and a fourth lens, wherein the seventh lens, the eleventh lens and the fourth lens are sequentially arranged from the object side to the image side, and focal lengths of the seventh lens, the eleventh lens and the fourth lens are sequentially negative, positive and positive; the seventh lens element is a biconcave lens element, the eighth lens element is a biconvex lens element, and the seventh lens element and the eighth lens element form a double cemented lens element with a convex surface facing the image side; the object side surface of the eleventh lens is a convex surface, and the image side surface of the eleventh lens is a concave surface;
the curvature radius of the object side surface of the first lens is R1, the curvature radius of the image side surface of the first lens is R2, the equivalent focal lengths of the second lens, the third lens and the fourth lens are F3, and the equivalent focal lengths of the fifth lens and the sixth lens are F4, and the following relations are satisfied:
1< R1/R2< 1.4; and
4<|F4/F3|<10。
2. projection objective according to claim 1, characterized in that the second lens has a convex object-side surface and a concave image-side surface; the third lens and the fourth lens are both biconcave lenses, the image side surface of the fifth lens is a convex surface, and the sixth lens is a biconvex lens.
3. Projection objective according to claim 2, characterized in that the distance between the object-side face of the first lens and the image plane of the projection objective is less than 4.5 cm.
4. Projection objective according to one of claims 1 to 3, characterized in that the following relation is also satisfied:
1.7<N1<1.9，
1.8<N2<2.0，
1.85<N3<2.0，
1.46<N4<1.65，
1.8<N5<2.0，
1.46<N6<1.65，
1.85<N7<2.0，
1.46<N8<1.65，
1.46<N9<1.65，
1.46<N10<1.65，
1.65<N11<1.85，
wherein N1 is a refractive index of the first lens, N2 is a refractive index of the second lens, N3 is a refractive index of the third lens, N4 is a refractive index of the fourth lens, N5 is a refractive index of the fifth lens, N6 is a refractive index of the sixth lens, N7 is a refractive index of the seventh lens, N8 is a refractive index of the eighth lens, N9 is a refractive index of the ninth lens, N10 is a refractive index of the tenth lens, and N11 is a refractive index of the eleventh lens.
5. Projection objective according to claim 4, characterized in that the second lens and the fifth lens are of the same material.
6. Projection objective according to claim 4, characterized in that the third lens and the seventh lens are of the same material.
7. Projection objective according to claim 4, characterized in that the fourth lens, the sixth lens, the eighth lens, the ninth lens and the tenth lens are of the same material.
8. Projection objective according to claim 4, characterized in that the projection objective further comprises a diaphragm arranged coaxially between the sixth lens and the seventh lens.
9. Projection objective according to claim 8, characterized in that the distance on the optical axis from the image-side face of the sixth lens to the diaphragm is T1 and the distance from the diaphragm to the object-side face of the seventh lens is T2, which satisfy the relation: t1< T2.
10. Projection objective according to claim 9, characterized in that the projection objective further comprises:
and the parallel flat plate is positioned between the eleventh lens and the image surface of the projection objective, shares the same optical axis with the eleventh lens, and is used for protecting the projection objective.
11. A scanning display device, comprising a fiber scanner and a projection objective according to any one of claims 1 to 10 corresponding to the fiber scanner, wherein the fiber scanner comprises an actuator and a fiber fixed on the actuator, and a part of the fiber beyond the actuator forms a fiber cantilever; wherein the actuator comprises a first actuation portion and a second actuation portion connected to the first actuation portion; under the action of a driving signal, the first actuating part moves in a first direction, the second actuating part drives the first actuating part to move in a second direction, the optical fiber cantilever moves in the direction which is the combination of the first direction and the second direction, and the movement frequency of the first actuating part is greater than or equal to that of the second actuating part.
12. A scanning display device as claimed in claim 11, wherein the scanning trajectory of the optical fiber by the actuator in the first direction corresponds to a radius of curvature of [2.0mm, 2.3mm ], a scanning radius of [2.3mm, + ∞ in the second direction, and an equivalent focal length of the projection objective of 2 mm.
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| CN201911129878.4A CN112817122B (en) | 2019-11-18 | 2019-11-18 | Projection objective and scanning display device |
| PCT/CN2020/129775 WO2021098723A1 (en) | 2019-11-18 | 2020-11-18 | Projection objective and scanning display device |
| US17/776,598 US20220397746A1 (en) | 2019-11-18 | 2020-11-18 | Projection objective and scanning display device |
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| JP5084775B2 (en) * | 2009-03-31 | 2012-11-28 | キヤノン株式会社 | Zoom lens and imaging apparatus having the same |
| JP5553566B2 (en) * | 2009-09-25 | 2014-07-16 | キヤノン株式会社 | Optical element, optical system, and optical instrument |
| CN101975983B (en) * | 2010-09-13 | 2012-05-30 | 北京理工大学 | High-resolution aspheric photoetching object lens |
| CN102981249B (en) * | 2012-09-21 | 2015-01-28 | 中国科学院光电技术研究所 | Projection optical system |
| JP2017138490A (en) * | 2016-02-04 | 2017-08-10 | セイコーエプソン株式会社 | Projection optical system, projector, and conversion lens for projector |
| CN108802977A (en) * | 2017-08-29 | 2018-11-13 | 成都理想境界科技有限公司 | A kind of short focus projection objective and optical fiber scanning projection device |
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