阅读说明：本技术 一种投影物镜及扫描显示装置 (Projection objective and scanning display device ) 是由 不公告发明人 于 2020-03-19 设计创作，主要内容包括：本发明涉及一种投影物镜及扫描显示装置,用于对光纤扫描器的弧型扫描面进行清晰成像。该投影物镜包括由物侧至像侧依次共光轴设置的第一透镜组和第二透镜组；所述第一透镜组包括由物侧至像侧依次设置的焦距依序为正、正、正、正及负的第一透镜至第五透镜共5个透镜；所述第一透镜的物侧面为凹面,第四透镜和所述第五镜头组合形成第一双胶合透镜,所述第五透镜为双凹透镜；所述第二透镜组包括由物侧至像侧依次设置的焦距依序为正、正、负、负、负及正的第六透镜至第十一透镜共6个透镜；其中,第十透镜的物侧面为凹面,十一透镜的像侧面为凸面,所述第十透镜和所述第十一镜头组合形成第二双胶合透镜。(The invention relates to a projection objective and a scanning display device, which are used for clearly imaging an arc-shaped scanning surface of an optical fiber scanner. The projection objective comprises a first lens group and a second lens group which are coaxially arranged from an object side to an image side in sequence; the first lens group comprises 5 lenses including a first lens, a second lens, a third lens and a fourth lens, wherein the focal lengths of the first lens, the second lens, the third lens and the fourth lens are sequentially positive, positive and negative; the object side surface of the first lens is a concave surface, the fourth lens and the fifth lens are combined to form a first double cemented lens, and the fifth lens is a double concave lens; the second lens group comprises 6 lenses which are a sixth lens, a fifth lens, a sixth lens, an eleventh lens and an image side, wherein the focal lengths of the lenses are positive, negative and positive in sequence; the object side surface of the tenth lens is a concave surface, the image side surface of the eleventh lens is a convex surface, and the tenth lens and the eleventh lens are combined to form a second double cemented lens.)

1. A projection objective is characterized by comprising a first lens group and a second lens group which are coaxially arranged from an object side to an image side in sequence;

the first lens group comprises 5 lenses including a first lens, a second lens, a third lens and a fourth lens, wherein the focal lengths of the first lens, the second lens, the third lens and the fourth lens are sequentially positive, positive and negative; the object side surface of the first lens is a concave surface, the fourth lens and the fifth lens are combined to form a first double cemented lens, and the fifth lens is a double concave lens;

the second lens group comprises 6 lenses which are a sixth lens, a fifth lens, a sixth lens, an eleventh lens and an image side, wherein the focal lengths of the lenses are positive, negative and positive in sequence; the object side surface of the tenth lens is a concave surface, the image side surface of the eleventh lens is a convex surface, and the tenth lens and the eleventh lens are combined to form a second double cemented lens.

2. The projection objective of claim 1, wherein the second lens element and the fourth lens element are each a biconvex lens element, the object-side surface of the third lens element is convex, the image-side surface of the sixth lens element is convex, the object-side surface of the seventh lens element is convex, the eighth lens element is a biconcave lens element, and the object-side surface of the ninth lens element is concave.

3. Projection objective according to claim 2, characterized in that the equivalent focal length of the first lens group is F1 and the equivalent focal length of the second lens group is F2, which satisfy the relation:

F2/F1＞1.5。

4. projection objective according to claim 3, characterized in that the second lens and the third lens form an equivalent focal length of F3, the equivalent focal length of the projection objective being F, which satisfies the relation:

1.4<F3/f<4.2。

5. projection objective according to claim 4, characterized in that the projection objective further satisfies the following relation:

2.00<f1/f<2.60，

2.30<f2/f<2.90，

4.60<f3/f<5.60，

1.00<f4/f<1.20，

-0.50<f5/f<-0.40，

1.50<f6/f<1.90，

1.40<f7/f<1.80，

-0.45<f8/f<-0.36，

-1.00<f9/f<-0.82，

-3.23<f10/f<-2.64，

1.86<f11/f<2.27，

wherein f is an equivalent focal length of the projection objective lens, f1 is a focal length of the first lens, f2 is a focal length of the second lens, f3 is a focal length of the third lens, f4 is a focal length of the fourth lens, f5 is a focal length of the fifth lens, f6 is a focal length of the sixth lens, f7 is a focal length of the seventh lens, f8 is a focal length of the eighth lens, f9 is a focal length of the ninth lens, f10 is a focal length of the tenth lens, and f11 is a focal length of the eleventh lens.

6. Projection objective according to claim 5, characterized in that the projection objective further satisfies the following relation:

7.31<f1<10.97，

8.24<f2<12.36，

16.46<f3<24.69，

3.55<f4<5.33，

-2.06<f5<-1.44，

5.37<f6<8.05，

5.14<f7<7.71，

-1.88<f8<-1.26，

-4.37<f9<-2.92，

-14.1<f10<-9.4，

6.61<f11<9.91。

7. projection objective according to claim 5 or 6, characterized in that the projection objective further satisfies the following relation:

1.7<n1<2.0，

1.5<n2<1.7，

1.5<n3<1.7，

1.5<n4<1.7，

1.7<n5<2.0，

1.5<n6<1.7，

1.7<n7<2.0，

1.7<n8<2.0，

1.7<n9<2.0，

1.5<n10<1.7，

1.7<n11<2.0，

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.

8. Projection objective according to claim 7, characterized in that the projection objective further comprises a diaphragm arranged coaxially between the fifth lens and the sixth lens.

9. Projection objective according to claim 8, characterized in that on the optical axis the distance from the image-side face of the fifth lens to the center of the diaphragm is D1 and the distance from the center of the diaphragm to the object-side face of the sixth lens is D2, which satisfies the relation: d1> D2.

10. Projection objective according to claim 9, characterized in that the distance between the object space of the lens barrel and the image side of the eleventh lens is less than 3.7 cm.

11. Projection objective according to claim 10, characterized in that the equivalent focal length of the projection objective is 4 mm.

12. A scanning display device comprising an optical fiber scanner and a projection objective according to any one of claims 1 to 11 corresponding to the optical scanner, the optical fiber scanner comprising an actuator and an optical fiber fixed to the actuator, a portion of the optical fiber beyond the actuator forming 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 the movement frequency of the second actuator.

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

With the development of fiber scanners, projection imaging of fiber scanners is a problem to be solved. 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 configured to image an arc-shaped pattern on a scanning surface of the projection objective on the object side onto the image side of the projection objective, where the arc-shaped pattern is the object side of the projection objective, as shown by reference number 123 in fig. 1B. However, since the object side scanned by the fiber scanner is a curved surface, and the object side (i.e. the image plane of the image source) acted by the conventional projection objective is generally a plane, the conventional projection objective cannot clearly image the curved surface image scanned by the fiber scanner.

Disclosure of Invention

The invention aims to provide a projection objective and a scanning display device, which are used for solving the imaging problem of an arc-shaped scanning image surface of an optical fiber scanner.

In order to achieve the above object, according to a first aspect of the present invention, there is provided in a first aspect thereof a projection objective comprising a first lens group and a second lens group coaxially arranged in order from an object side to an image side;

the first lens group comprises 5 lenses including a first lens, a second lens, a third lens and a fourth lens, wherein the focal lengths of the first lens, the second lens, the third lens and the fourth lens are sequentially positive, positive and negative; the object side surface of the first lens is a concave surface, the fourth lens and the fifth lens are combined to form a first double cemented lens, and the fifth lens is a double concave lens;

the second lens group comprises 6 lenses which are a sixth lens, a fifth lens, a sixth lens, an eleventh lens and an image side, wherein the focal lengths of the lenses are positive, negative and positive in sequence; the object side surface of the tenth lens is a concave surface, the image side surface of the eleventh lens is a convex surface, and the tenth lens and the eleventh lens are combined to form a second double cemented lens.

Optionally, the second lens element and the fourth lens element are both biconvex lenses, an object-side surface of the third lens element is a convex surface, an image-side surface of the sixth lens element is a convex surface, an object-side surface of the seventh lens element is a convex surface, the eighth lens element is a biconcave lens element, and an object-side surface of the ninth lens element is a concave surface.

Optionally, the first lens group has an equivalent focal length of F1, and the second lens group has an equivalent focal length of F2, which satisfy the following relation:

F2/F1＞1.5。

optionally, an equivalent focal length formed by the second lens and the third lens is F3, and an equivalent focal length of the projection objective lens is F, which satisfies the following relation:

1.4<F3/f<4.2。

optionally, the projection objective further satisfies the following relation:

2.00<f1/f<2.60，

2.30<f2/f<2.90，

4.60<f3/f<5.60，

1.00<f4/f<1.20，

-0.50<f5/f<-0.40，

1.50<f6/f<1.90，

1.40<f7/f<1.80，

-0.45<f8/f<-0.36，

-1.00<f9/f<-0.82，

-3.23<f10/f<-2.64，

1.86<f11/f<2.27，

wherein f is an equivalent focal length of the projection objective lens, f1 is a focal length of the first lens, f2 is a focal length of the second lens, f3 is a focal length of the third lens, f4 is a focal length of the fourth lens, f5 is a focal length of the fifth lens, f6 is a focal length of the sixth lens, f7 is a focal length of the seventh lens, f8 is a focal length of the eighth lens, f9 is a focal length of the ninth lens, f10 is a focal length of the tenth lens, and f11 is a focal length of the eleventh lens.

Optionally, the projection objective further satisfies the following relation:

7.31<f1<10.97，

8.24<f2<12.36，

16.46<f3<24.69，

3.55<f4<5.33，

-2.06<f5<-1.44，

5.37<f6<8.05，

5.14<f7<7.71，

-1.88<f8<-1.26，

-4.37<f9<-2.92，

-14.1<f10<-9.4，

6.61<f11<9.91。

optionally, the projection objective further satisfies the following relation:

1.7<n1<2.0，

1.5<n2<1.7，

1.5<n3<1.7，

1.5<n4<1.7，

1.7<n5<2.0，

1.5<n6<1.7，

1.7<n7<2.0，

1.7<n8<2.0，

1.7<n9<2.0，

1.5<n10<1.7，

1.7<n11<2.0，

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 projection objective further includes a diaphragm disposed coaxially between the fifth lens and the sixth lens.

Optionally, on the optical axis, a distance between an image side surface of the fifth lens and a center of the stop is D1, and a distance between the center of the stop and an object side surface of the sixth lens is D2, which satisfy the following relation: d1> D2.

Optionally, a distance between an object side of the lens barrel and an image side surface of the eleventh lens is less than 3.7 cm.

Optionally, the equivalent focal length of the projection objective is 4 mm.

In a second aspect, an embodiment of the present invention provides a scanning display device, including an optical fiber scanner and the projection objective corresponding to the optical scanner as described in the first aspect, where 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 the movement frequency of the second actuator.

In the embodiment of the invention, the focal length of each lens in the two lens groups of the projection objective lens, namely 11 lenses with the same optical axis, can be set, so that the focal power of the system can be reasonably dispersed, the aberration generated by the lenses can be reduced, and the clear imaging of an arc object space can be realized. Meanwhile, the object side surface of the diaphragm is a first double cemented lens, the image side surface of the first double cemented lens is a biconvex lens, and the object side surface of the first double cemented lens is a biconcave lens, so that aberration can be effectively corrected.

Drawings

Fig. 1A to 1B are schematic structural diagrams of a conventional optical fiber scanning projection system;

fig. 2 is a schematic diagram of a structure and an imaging 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 is a graph of MTF of a projection objective imaging a fiber optic scanner according to an embodiment of the present invention;

FIG. 4B is a graph showing distortion of a fiber optic scanner when imaged by a projection objective 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 provided in the embodiments of the present invention is configured to image an arc-shaped pattern on a scanning surface of the projection objective on an object side of the projection objective onto an image side of the projection objective, and at the same time, reduce chromatic aberration of the lens by introducing two double cemented lenses. Wherein, the arc-shaped pattern on the object side is an arc-shaped scanning surface scanned by the optical fiber scanner shown in fig. 1A-1B or emitted by other image sources; the image side is a projection imaging surface such as 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. Wherein the fiber scanner includes an optical fiber and an actuator, the optical fiber is fixed on the actuator along the extending direction of the actuator (refer to the direction of the mark A to the mark B in FIG. 1A), and the part of the optical fiber beyond the actuator forms a 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 and moves in the fast axis direction, the slow axis actuating part drives the fast axis actuating part to scan and move in the slow axis direction, and the actuator drives the optical fiber cantilever to perform two-dimensional scanning and moving in the synthetic direction of the fast axis direction and the slow axis direction, such as a grid scanning mode, a spiral scanning mode and the like, so that an arc-shaped scanning surface (corresponding to the image surface of the projection objective lens) is formed. Preferably, the fast axis direction is the X direction and the slow axis direction is the 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 optical fiber scanner moves through the fast and slow axes, scanning tracks in the fast axis direction and the slow axis direction respectively have corresponding curvature radiuses, and an arc-shaped scanning surface correspondingly formed by the movement track of the light outlet end of the optical fiber is an object space 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-shaped image space tends to a straight line, and the scanning surface is similar to a cylindrical surface at this time. 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 emergent arc-shaped scanning surface of the optical fiber scanner.

Next, a projection objective lens in an embodiment of the present invention will be described.

Fig. 2 to fig. 3 are schematic structures of projection objectives according to embodiments of the present invention. The projection objective comprises a first lens group and a second lens group which are coaxially arranged in sequence from an object side to an image side, wherein the first lens group comprises five lenses from a first lens 1 to a fifth lens 5 which are arranged in sequence from the object side to the image side and have positive, positive and negative focal lengths in sequence, the object side surface of the first lens 1 is a concave surface which is beneficial to reducing the optical sensitivity, the fifth lens 5 is a biconcave lens, and the fourth lens 4 and the fifth lens 5 form a first biconcave lens; the second lens group includes six lenses, namely a sixth lens 6 to an eleventh lens 11, which are sequentially arranged from the object side to the image side and have positive, negative and positive focal lengths, wherein an object side surface of the tenth lens 10 is a concave surface, an image side surface of the eleventh lens 11 is a convex surface, and the tenth lens 10 and the eleventh lens 11 form a second double cemented lens.

The fourth lens 4 and the fifth lens 5 can form a first cemented doublet through optical cement bonding and the like; similarly, the tenth lens 10 and the eleventh lens 11 may be combined into a second cemented doublet by optical cement. In the projection objective, the concave surface of the first cemented doublet faces the image side, and the convex surface of the second cemented doublet faces the image side, and the two cemented doublets can play the roles of correcting chromatic aberration and reducing optical sensitivity in the projection objective.

Preferably, the second lens element 2 and the fourth lens element 4 are both biconvex lenses, the object-side surface of the third lens element 3 is a convex surface, the image-side surface of the sixth lens element 6 is a convex surface, the object-side surface of the seventh lens element 7 is a convex surface, the eighth lens element 8 is a biconcave lens element, and the object-side surface of the ninth lens element 9 is a concave surface.

The term "object side to image side" refers to the direction from the object side 01 (i.e. the object side) to the image side 02 (i.e. the image side) in fig. 2; the object side surface is a convex surface, which means that the object side surface faces the object space 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 is concave towards the object space 01; the image side surface is convex, and is in a convex shape towards the image space 02 of the projection objective; the image side surface is concave, and is a shape in which the image side surface is concave toward the image side 02.

In the embodiment of the present invention, the equivalent focal length of the first lens group 1 is F1, and the equivalent focal length of the second lens group 2 is F2, which satisfy the following relation: F2/F1 is more than 1.5, so that the optical power of the system is dispersed, and the aberration generated by each lens is relieved.

Preferably, if the two lenses of the second lens 2 and the third lens 3 form an equivalent focal length F3 and the equivalent focal length of the projection objective lens is F, 1.4< F3/F <4.2, so as to effectively balance the aberration generated by the first cemented doublet.

An aperture 03 may be disposed between the fifth lens element 5 and the sixth lens element 6 for reducing stray light and improving image quality, which is also shown in fig. 2. The kind of the diaphragm 03 may be an aperture diaphragm, a Field diaphragm (Field Stop), a vignetting diaphragm, or the like. If the distance between the image side surface of the fifth lens 5 and the center of the stop 03 is D1, and the distance between the center of the stop 03 and the object side surface of the sixth lens 6 is D2, the following relation is satisfied: d1> D2, so that the aberration can be corrected better, the system structure of the projection objective is more compact, the total optical length of the projection objective does not exceed 37mm, and the volume of the projection objective is smaller.

In the embodiment of the present invention, the effect of the design structure of the projection objective on the light can be understood from the direction from the object space 01 (arc-shaped scanning surface) to the image space 02 as follows: the first lens 1, the second lens 2 and the third lens 3 converge the middle of a chief ray in emergent light of an object space, then the first double cemented lens converges the light into the diaphragm 03, further the light is diverged through the sixth lens 6 and the seventh lens 7 to be converged, then the eighth lens 8 and the ninth lens 9 are converged, and then the image can be formed on the image space 02 through the second double cemented lens. Therefore, after the light of the arc scanning surface (i.e. the object space 01) is acted by the projection objective, the arc image emitted from the optical fiber scanner can be clearly magnified and imaged on a plane (i.e. the image space 02), please refer to fig. 2.

In one possible embodiment, the first lens 1 to the eleventh lens 11 of the projection objective satisfy the following relationships:

2.00<f1/f<2.60，

2.30<f2/f<2.90，

4.60<f3/f<5.60，

1.00<f4/f<1.20，

-0.50<f5/f<-0.40，

1.50<f6/f<1.90，

1.40<f7/f<1.80，

-0.45<f8/f<-0.36，

-1.00<f9/f<-0.82，

-3.23<f10/f<-2.64，

1.86<f11/f<2.27，

where f is the equivalent focal length of the projection objective lens, f1 is the focal length of the first lens 1, f2 is the focal length of the second lens 2, f3 is the focal length of the third lens 3, f4 is the focal length of the fourth lens 4, f5 is the focal length of the fifth lens 5, f6 is the focal length of the sixth lens 6, f7 is the focal length of the seventh lens 7, f8 is the focal length of the eighth lens 8, f9 is the focal length of the ninth lens 9, f10 is the focal length of the tenth lens 10, and f11 is the focal length of the eleventh lens 11.

In another possible embodiment, the focal lengths of the first lens 1 to the eleventh lens 11 in the projection objective satisfy the following condition:

7.31<f1<10.97，

8.24<f2<12.36，

16.46<f3<24.69，

3.55<f4<5.33，

-2.06<f5<-1.44，

5.37<f6<8.05，

5.14<f7<7.71，

-1.88<f8<-1.26，

-4.37<f9<-2.92，

-14.1<f10<-9.4，

6.61<f11<9.91，

wherein f 1-f 11 represent focal lengths of the first lens 1-the eleventh lens 11, respectively.

Further, in a possible embodiment, the refractive index of the first lens 1 to the eleventh lens 11 in the projection lens satisfies the following condition:

1.7<n1<2.0，

1.5<n2<1.7，

1.5<n3<1.7，

1.5<n4<1.7，

1.7<n5<2.0，

1.5<n6<1.7，

1.7<n7<2.0，

1.7<n8<2.0，

1.7<n9<2.0，

1.5<n10<1.7，

1.7<n11<2.0，

where n1 to n11 represent refractive indices of the first lens 1 to the eleventh lens 11, respectively.

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 given by taking glass as an example of the lens in the projection objective, and glasses with different refractive indexes can be used for different lenses in the projection objective.

In one embodiment of the present invention, the projection objective has an equivalent focal length of 4mm as a whole, and the preferred parameters of the curvature radius, thickness parameter and refractive index of each lens for projection imaging on the scanning surface (taking a cylindrical surface as an example) are shown in table 1:

TABLE 1

In table 1, the total optical length of the projection objective, i.e. the distance between the object space and the image side of the eleventh lens 11, is taken as an example to be 36.5 mm. Meanwhile, taking the example that all lenses in the projection objective are made of glass and are all ball lenses, the design of the ball lenses is beneficial to processing the lenses; in practice, aspheric lenses may also be used, with the relevant parameters or proportions still satisfying the foregoing. The optical surface with "infinite" curvature radius in the lens is a plane, and the distance parameter corresponding to the image space is the projection distance of the projection lens, and the projection distance can be set according to the actual situation. Wherein, L1 is the distance from the object space 01 (arc scanning surface) to the object side surface of the first lens 1, L2 is the thickness of the first lens 1, and L3 is the distance between the image side surface 12 of the first lens 1 and the object side surface of the second lens 2 on the optical axis; l4 is the thickness of the second lens 2, and L5 is the distance between the image side surface of the second lens 2 and the object side surface of the third lens 3 on the optical axis; l6 is the thickness of the third lens element 3, and L7 is the distance from the image-side surface of the third lens element 3 to the object-side surface of the fourth lens element 4 on the optical axis; l8 is the thickness of the fourth lens 4, L9 is the thickness of the fifth lens 5, and L10 is the distance between the image side surface of the fifth lens 5 and the diaphragm 03 on the optical axis; l11 is the distance between the stop 03 and the object-side surface of the sixth lens element 6 on the optical axis, L12 is the thickness of the sixth lens element 6, and L13 is the distance between the image-side surface of the sixth lens element 6 and the object-side surface of the seventh lens element 7 on the optical axis; l14 is the thickness of the seventh lens 7; l15 is the distance between the image-side surface of the seventh lens element 7 and the object-side surface of the eighth lens element 8 on the optical axis, L16 is the thickness of the eighth lens element 8, and L17 is the distance between the image-side surface of the eighth lens element 8 and the object-side surface of the ninth lens element 9 on the optical axis; l18 is the thickness of the ninth lens element 9, and L19 is the distance from the image-side surface of the ninth lens element 9 to the object-side surface of the tenth lens element 10 on the optical axis; l20 is the thickness of the tenth lens 10, L21 is the thickness of the eleventh lens 11, and L22 is the distance from the image side surface of the eleventh lens 11 to the image side 02 (i.e., the projected image), and this distance is designed to be infinity as an example in the table.

In the actual scanning projection process, when the projection objective is applied to the optical fiber scanning projection system, the imaging process of the light beam scanned and emitted by the optical fiber light-emitting end in the fast axis direction through the projection lens is shown in fig. 2, the imaging process of the light beam scanned and emitted by the optical fiber light-emitting end in the slow axis direction through the projection lens to the object space 01 is shown in fig. 3, and the scanning track in the slow axis direction is taken as a straight line in fig. 3 (i.e., the curvature radius corresponding to the scanning track of the optical fiber light-emitting end is "+ ∞").

Through tests, when the projection objective is adopted to project image light corresponding to a scanning surface, an optical transfer function curve graph and a distortion curve graph are respectively shown as fig. 4A and fig. 4B; wherein, the Modulation Transfer Function (MTF) represents the comprehensive resolution level of an optical system, and the distortion curve represents the F-tan (theta) distortion value (percentage) under different angles of view.

As can be seen from the MTF curve of the projection objective shown in fig. 4A: the MTF at the center at 0.4lp/mm is more than 0.6, the MTFs at the edges at 0.4lp/mm are all more than 0.3, and the imaging resolution ratio in the full field range is good; as can be seen from the distortion curve shown in fig. 4B: the distortion value of the optical system of the projection objective is less than 3%, and the distortion is good in the full view field range, so that the projection objective can clearly image the arc-shaped scanning image of the optical fiber scanner, and the projection objective 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 length of each lens in the two lens groups of the projection objective, which are 11 coaxial lenses, the focal power of the system can be reasonably dispersed, the aberration generated by the lenses is reduced, and clear imaging of an arc-shaped image space is realized. Meanwhile, the object side surface of the diaphragm 03 is a first double cemented lens, the image side surface of the first double cemented lens is a double convex lens, and the object side surface of the first double cemented lens is a double concave lens, so that aberration can be effectively corrected.

Meanwhile, the focal length of the projection objective is designed to be 4mm, and the imaging requirement of high resolution can be met.

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.