Lens structure

Abstract

The utility model provides a lens structure, which comprises a lens barrel and a lens group accommodated in the lens barrel, the lens group is trimmed at two sides relative to the optical axis of the lens structure, the lens group comprises at least two trimmed lenses, the first lens is closest to the object side of the lens structure in the at least two trimmed lenses, the object side surface of the first lens is provided with a first bearing part, and the object side surface of the second lens is provided with a second bearing part. The lens group further comprises a first structure ring, the first structure ring abuts against the first bearing part, and the first structure ring is provided with a first non-trimming part and a first trimming part which are connected in the circumferential direction. The shortest distance d between the inner ring surface, closest to the optical axis, of the first trimming portion and the first lens in the direction parallel to the optical axis, and the shortest distance a between the trimming portion of the first lens and the inner wall surface of the lens barrel in the direction perpendicular to the optical axis meet the condition that d / a is larger than or equal to 0.50 and smaller than or equal to 1.30. The trimming lens solves the problem that high image quality and small size of the trimming lens in the prior art are difficult to consider at the same time.

Description

Technical Field

[0001] The utility model relates to the technical field of imaging equipment, in particular to a lens structure. Background Art

[0002] As imaging products develop towards specialization, users' imaging requirements for optical lenses continue to increase, and the thickness and volume of optical lenses continue to increase, which cannot adapt to the terminal devices that are developing towards miniaturization. In order to reduce the occupied space, the existing technology often uses trimmed lenses to reduce the volume, but trimmed lenses are prone to structural size limits, which can easily lead to processing and molding problems, poor reliability, and assembly interference problems. Therefore, the structural design of trimmed lenses is more difficult and difficult to meet customer needs.

[0003] That is to say, the existing cutting edge lens has the problem of difficulty in achieving both high image quality and small size. Utility Model Content

[0004] The main purpose of the utility model is to provide a lens structure to solve the problem that it is difficult to achieve both high image quality and small size in the prior art edge trimming lens.

[0005] In order to achieve the above-mentioned purpose, the utility model provides a lens structure, comprising: a lens barrel and a lens group accommodated in the lens barrel, the lens group is trimmed on both sides relative to the optical axis of the lens structure, the lens group includes at least two trimmed lenses, of the at least two trimmed lenses, the one closest to the object side of the lens structure is a first lens, the object side surface of the first lens has a first bearing portion, the lens group also includes a first structural ring, the first structural ring bears against the first bearing portion, the first structural ring has a first non-trimmed portion and a first trimmed portion connected circumferentially, the shortest distance d from the inner annular surface of the first trimmed portion closest to the optical axis to the first lens along a direction parallel to the optical axis, and the shortest distance a between the trimmed portion of the first lens and the inner wall surface of the lens barrel along a direction perpendicular to the optical axis satisfy: 0.50≤d / a≤1.30.

[0006] Furthermore, at least two trimmed lenses also include an image end lens closest to the image side of the lens structure, and the object side surface of the image end lens is supported by a variable spacer, the variable spacer has a second non-trimmed portion and a second trimmed portion connected circumferentially, the second trimmed portion has an interference point that interferes with the image end lens, and the maximum distance e from the interference point to the inner annular surface of the second trimmed portion along the direction perpendicular to the optical axis and the width j of the second trimmed portion along the direction perpendicular to the optical axis satisfy: 0.40≤e / j≤0.60.

[0007] Further, a width j of the second trimming portion along a direction perpendicular to the optical axis and a thickness k of the variable spacer along a direction parallel to the optical axis satisfy: 18≥j / k≥12.

[0008] Furthermore, the shortest distance a between the trimmed portion of the first lens and the inner wall surface of the lens barrel along a direction perpendicular to the optical axis satisfies: 0.05 mm≤a≤0.1 mm.

[0009] Furthermore, the object side end of the lens barrel has a notch portion corresponding to the first trimming portion, and a gap h between the notch portion and the first trimming portion along the optical axis and a length L of the first trimming portion satisfy: 0.005≤h / L≤0.01.

[0010] Furthermore, a recessed structure opening away from the optical axis is formed at the connection between the first non-cutting edge portion and the first cutting edge portion, and the recessed structure has a first cross-section, a transition arc surface, and a second cross-section connected in sequence, an extension direction of the first cross-section is parallel to an extension direction of the first cutting edge portion, an extension direction of the second cross-section is perpendicular to an extension direction of the first cutting edge portion, and a gap b1 between the first cross-section and the lens barrel and a gap b2 between the second cross-section and the lens barrel satisfy the following conditions: 0.60≤b1 / b2≤1.30.

[0011] Furthermore, the radius f of the transition arc surface and the gap b1 between the first cross section and the lens barrel satisfy:

[0012] Furthermore, the lens barrel has a protruding structure that is buckled with the recessed structure, and a protruding length c of the inner ring surface of the protruding structure toward the recessed structure and a length L of the first trimming portion satisfy: 0.07≤c / L≤0.09.

[0013] Furthermore, the gap b1 between the first cross section and the lens barrel, the gap b2 between the second cross section and the lens barrel, and the extension length c of the inner ring surface of the protruding structure to the recessed structure satisfy: 0.07≤(b1+b2) / 2c≤0.19.

[0014] Furthermore, the first trimming portion has an arc surface on a side facing the first lens, and the arc surface is the same shape as the object side surface of the first lens and is arranged at an interval.

[0015] Furthermore, the width i of the arc surface along the direction perpendicular to the optical axis and the maximum distance i1 from the arc surface to the outer annular surface of the first trimming portion satisfy: 0.4≤i / i1≤0.8.

[0016] According to the technical solution of the utility model, the lens structure includes a lens barrel and a lens group accommodated in the lens barrel, the lens group is trimmed on both sides relative to the optical axis of the lens structure, the lens group includes at least two trimmed lenses, among the at least two trimmed lenses, the one closest to the object side of the lens structure is a first lens, the object side surface of the first lens has a first supporting portion, the lens group also includes a first structural ring, the first structural ring is supported by the first supporting portion, the first structural ring has a first non-trimmed portion and a first trimmed portion connected in a circumferential direction, the shortest distance d from the inner annular surface of the first trimmed portion closest to the optical axis to the first lens along a direction parallel to the optical axis, and the shortest distance a between the trimmed portion of the first lens and the inner wall surface of the lens barrel along a direction perpendicular to the optical axis satisfies the following: 0.50≤d / a≤1.30.

[0017] By providing a first structural ring for supporting the object side of the first lens, the first trimming portion of the first structural ring is spaced apart from the object side surface of the first lens, thereby preventing the first lens and the first structural ring from interfering with each other when they are assembled. In addition, the trimming portion of the first lens and the inner wall surface of the lens barrel are also spaced apart, thereby reducing the space occupied by the first lens and the lens barrel and avoiding interference when the first lens is assembled in the lens barrel. Furthermore, by controlling d / a within a reasonable range, the gap between the first lens and the first structural ring is reduced on the premise that there is no interference between the first lens and the first structural ring, thereby improving the compactness of the lens structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0019] Figure 1 An exploded view of a lens structure of an optional embodiment of the utility model is shown;

[0020] Figure 2 Shows Figure 1 A cross-sectional view of the lens structure in ;

[0021] Figure 3 Shows Figure 1 A front view of the lens structure in FIG.

[0022] Figure 4 Shows Figure 1 A front view of the first structural ring in FIG.

[0023] Figure 5 A cross-sectional view of the lens structure of Embodiment 1 of the present utility model is shown;

[0024] Figure 6 Shows Figure 5 A front view of the lens structure in FIG.

[0025] Figure 7 Shows Figure 5 A front view of the first structural ring in FIG.

[0026] Figure 8 A cross-sectional view of the lens structure of Embodiment 2 of the present utility model is shown;

[0027] Fig. 9 Shows Figure 8 A front view of the lens structure in FIG.

[0028] Fig.10 Shows Figure 8 A front view of the first structural ring in FIG.

[0029] Fig.11 A cross-sectional view of the lens structure of Embodiment 3 of the present utility model is shown;

[0030] Fig.12 Shows Fig.11 A front view of the lens structure in FIG.

[0031] Fig.13 Shows Fig.11 A front view of the first structural ring in FIG.

[0032] Fig.14 A cross-sectional view of the lens structure of Embodiment 4 of the present utility model is shown;

[0033] Fig.15 Shows Fig.14 A front view of the lens structure in FIG.

[0034] Fig.16 Shows Fig.14 Front view of the first structural ring in.

[0035] The above drawings include the following reference numerals:

[0036] 1. Lens barrel; 2. Lens group; 3. First lens; 4. First supporting part; 5. First structural ring; 6. First non-cutting edge part; 7. First cutting edge part; 8. Image end lens; 9. Variable spacer; 10. Second cutting edge part; 11. Second non-cutting edge part; 12. Notch part; 13. First cross section; 14. Second cross section; 15. Transition arc surface; 16. Circular arc surface. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present utility model will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0039] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0040] In order to solve the problem in the prior art that it is difficult to achieve both high image quality and small size of a trimmed lens, the utility model provides a lens structure.

[0041] like Figures 1 to 16 As shown, the lens structure includes a lens barrel 1 and a lens group accommodated in the lens barrel 1, the lens group is trimmed on both sides relative to the optical axis of the lens structure, the lens group includes at least two trimmed lenses, among the at least two trimmed lenses, the one closest to the object side of the lens structure is a first lens 3, the object side surface of the first lens 3 has a first bearing portion 4, the lens group also includes a first structural ring 5, the first structural ring 5 is supported by the first bearing portion 4, the first structural ring 5 has a first non-trimmed portion 6 and a first trimmed portion 7 connected circumferentially, the shortest distance d from the inner annular surface of the first trimmed portion 7 closest to the optical axis to the first lens 3 along the direction parallel to the optical axis, and the shortest distance a between the trimmed portion of the first lens 3 and the inner wall surface of the lens barrel 1 along the direction perpendicular to the optical axis satisfies: 0.50≤d / a≤1.30.

[0042] By providing the first structural ring 5 for supporting the object side of the first lens 3, the first trimming portion 7 of the first structural ring 5 is spaced apart from the object side surface of the first lens 3, so that the first lens 3 and the first structural ring 5 can be prevented from assembling interference. In addition, the trimming portion of the first lens 3 and the inner wall surface of the lens barrel 1 are also spaced apart, so that while reducing the space occupied by the first lens 3 and the lens barrel 1, interference is avoided when the first lens group 2 is installed in the lens barrel 1. Further, by controlling d / a within a reasonable range, on the premise that the first lens 3 and the first structural ring 5 do not interfere with each other, the gap between the first lens 3 and the first structural ring 5 is reduced, thereby improving the structural compactness of the lens structure.

[0043] It should be noted that, since the lens group is trimmed on both sides relative to the optical axis of the lens structure, the trimmed portions and non-trimmed portions of the components in the lens group are alternately connected in the circumferential direction and are symmetrically arranged.

[0044] Specifically, at least two trimmed lenses also include an image end lens 8 closest to the image side of the lens structure, and the object side of the image end lens 8 is supported by a variable spacer 9, and the variable spacer 9 has a second non-trimmed portion 11 and a second trimmed portion 10 connected circumferentially, and the second trimmed portion 10 has an interference point that interferes with the image end lens 8, and the maximum distance e from the interference point to the inner annular surface of the second trimmed portion 10 along the direction perpendicular to the optical axis and the width j of the second trimmed portion 10 along the direction perpendicular to the optical axis satisfy: 0.40≤e / j≤0.60. By controlling e / j within a reasonable range and controlling the maximum distance from the interference point Z to the inner annular surface of the second trimmed portion 10, the size of the inner diameter shrinkage hole corresponding to the second trimmed portion 10 can be changed, and the optical performance is guaranteed and the stray light of the lens structure is improved without affecting the stability of the assembly of the variable spacer 9 and the image end lens 8, and the variable spacer 9 has good processability.

[0045] Specifically, the width j of the second trimming portion 10 in the direction perpendicular to the optical axis and the thickness k of the variable spacer 9 in the direction parallel to the optical axis satisfy: 18 ≥ j / k ≥ 12. By limiting j / k within a reasonable range, the ratio of the thickness of the variable spacer 9 to the width of the second trimming portion 10 is controlled, and the rigidity of the variable spacer 9 is reduced, so that it can be easily deformed with the shape of the image end lens 8 after assembly, thereby improving the assembly interference problem and improving the space utilization rate.

[0046] Specifically, the shortest distance a between the trimmed portion of the first lens 3 and the inner wall surface of the lens barrel 1 in a direction perpendicular to the optical axis satisfies: 0.05mm≤a≤0.1mm. By limiting the range of a, while controlling the small volume of the front end of the first lens 3 and the lens barrel 1, it is beneficial to improve the compactness of the lens structure, achieve the same performance with a smaller space occupation, and the lens structure can meet the customer's external size requirements and the coordination of optical performance parameters.

[0047] Specifically, the object side end of the lens barrel 1 has a notch 12 corresponding to the first trimming portion 7, and the gap h between the notch 12 and the first trimming portion 7 along the optical axis direction and the length L of the first trimming portion 7 satisfy: 0.005≤h / L≤0.01. By limiting h / L within a reasonable range and controlling the gap between the notch 12 of the lens barrel 1 and the first trimming portion 7, it is beneficial to prevent the first trimming portion 7 from being suspended in the air, resulting in uneven force and excessive deformation, improving the stress distribution of the first structural ring 5, and improving the structural reliability.

[0048] Specifically, a concave structure with an opening facing away from the optical axis is formed at the connection between the first non-cutting edge portion 6 and the first cutting edge portion 7, and the concave structure has a first cross section 13, a transition arc surface 15, and a second cross section 14 connected in sequence, the extension direction of the first cross section 13 is parallel to the extension direction of the first cutting edge portion 7, the extension direction of the second cross section 14 is perpendicular to the extension direction of the first cutting edge portion 7, and the gap b1 between the first cross section 13 and the lens barrel 1 and the gap b2 between the second cross section 14 and the lens barrel 1 satisfy: 0.60≤b1 / b2≤1.30. By limiting b1 / b2 within a reasonable range and controlling the gap distance between the first cross section 13, the second cross section 14 and the lens barrel 1, the structure of the first structural ring 5 is made more uniform, and the space utilization rate is improved.

[0049] Specifically, the radius f of the transition arc surface 15 and the gap b1 between the first cross section 13 and the lens barrel 1 satisfy: By controlling f and b1 to meet the above range, the gap between the transition arc surface 15 and the lens barrel 1 is controlled to prevent the rounded corners of the recessed structure from interfering with the lens barrel 1 due to tolerance and burrs, thereby improving the assembly interference problem.

[0050] Specifically, the lens barrel 1 has a protruding structure that is engaged with the recessed structure, and the extension length c of the inner ring surface of the protruding structure toward the recessed structure and the length L of the first trimming portion 7 satisfy: 0.07≤c / L≤0.09. By controlling c / L within a reasonable range, the position of the annular surface of the lens barrel 1 facing the notch portion 12 to the inner wall of the lens barrel 1 without trimming is controlled, the cutting length of the first structure ring 5 is reduced, the thickness of the first structure ring 5 is increased, and the structural reliability is improved.

[0051] Specifically, the gap b1 between the first cross section 13 and the lens barrel 1, the gap b2 between the second cross section 14 and the lens barrel 1, and the extension length c of the inner ring surface of the protruding structure to the recessed structure satisfy: 0.07≤(b1+b2) / 2c≤0.19. By limiting (b1+b2) / 2c within a reasonable range, the gap distances between the first cross section 13, the second cross section 14 and the lens barrel 1 are reduced, the first structure ring 5 is prevented from rotating too much during the assembly process, and the assembly accuracy of the first structure ring 5 is improved.

[0052] Specifically, the first trimming portion 7 has an arc surface 16 on the side facing the first lens 3, and the arc surface 16 is in the same shape as the object side surface of the first lens 3 and is arranged at an interval. By controlling the arc surface 16 not to interfere with the first lens 3, interference is prevented during the assembly process, and the arc surface 16 is ensured to fit the first lens 3 as much as possible, thereby improving the space utilization rate of the lens structure.

[0053] Specifically, the width i of the arc surface 16 in the direction perpendicular to the optical axis and the maximum distance i1 from the arc surface 16 to the outer annular surface of the first trimming portion 7 satisfy: 0.4≤i / i1≤0.8. By limiting i / i1 within a reasonable range, the maximum height from the arc surface 16 to the first trimming portion 7 is controlled, the thickness of the first structural ring 5 is retained to the greatest extent, the structural strength of the first structural ring 5 is improved, and the structural reliability is improved.

[0054] The present application provides four lens structures with similar structures and only different sizes as embodiments 1 to 4. Among them, the lens structure of embodiment 1 is as follows: Figures 5 to 7 As shown, the lens structure of Example 2 is as follows Figures 8 to 10 As shown, the lens structure of Example 3 is as follows Figures 11 to 13 As shown, the lens structure of Example 4 is as follows Figures 14 to 16 Table 1 below shows some parameters of the lens structures of Examples 1 to 4, with the unit being mm.

[0055] Example Data a b1 b2 c d e h i i1 L j k f 1 0.100 0.085 0.070 0.425 0.060 0.320 0.050 0.290 0.520 5.540 0.630 0.035 0.1 2 0.080 0.030 0.030 0.430 0.040 0.250 0.030 0.200 0.440 5.540 0.600 0.035 0.03 3 0.055 0.070 0.070 0.455 0.070 0.300 0.050 0.320 0.550 5.540 0.500 0.035 0.12 4 0.055 0.040 0.060 0.490 0.070 0.250 0.050 0.180 0.410 5.540 0.450 0.035 0.075

[0056] Table 1

[0057] Table 2 shows the values ​​of conditional expressions satisfied by the lens structures of Examples 1 to 4.

[0058]

[0059] Table 2

[0060] From the above description, it can be seen that the above embodiments of the utility model achieve the following technical effects:

[0061] 1. By providing a first structural ring 5 for supporting the object side of the first lens 3, the first trimming portion 7 of the first structural ring 5 is spaced apart from the object side surface of the first lens 3, thereby preventing the first lens 3 and the first structural ring 5 from assembling interference.

[0062] 2. The trimmed portion of the first lens 3 is also spaced apart from the inner wall of the lens barrel 1 , so as to reduce the space occupied by the first lens 3 and the lens barrel 1 and avoid interference when the first lens group 2 is installed in the lens barrel 1 .

[0063] 3. By controlling d / a within a reasonable range, on the premise that the first lens 3 and the first structural ring 5 do not interfere with each other, the gap between the first lens 3 and the first structural ring 5 is reduced, thereby improving the compactness of the lens structure.

[0064] Obviously, the embodiments described above are only some embodiments of the utility model, not all embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0065] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0066] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0067] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A lens structure, characterized in that: include: A lens barrel (1) and a lens group accommodated in the lens barrel (1), wherein the lens group is trimmed on both sides relative to the optical axis of the lens structure, the lens group comprises at least two trimmed lenses, of which the first lens (3) is closest to the object side of the lens structure, the object side surface of the first lens (3) comprises a first supporting portion (4), the lens group further comprises a first structural ring (5), the first structural ring (5) is supported by the first supporting portion (4), the first structural ring (5) comprises a first non-trimmed portion (6) and a first trimmed portion (7) connected in a circumferential direction, the shortest distance d from the inner annular surface of the first trimmed portion (7) closest to the optical axis to the first lens (3) in a direction parallel to the optical axis, and the shortest distance a from the trimmed portion of the first lens (3) to the inner wall surface of the lens barrel (1) in a direction perpendicular to the optical axis satisfies the following: 0.50≤d / a≤1.

30.

2. The lens structure according to claim 1, characterized in that: The at least two edge-cut lenses also include an image end lens (8) closest to the image side of the lens structure, the object side surface of the image end lens (8) is supported by a variable spacer (9), the variable spacer (9) has a circumferentially connected second non-edge-cut portion (11) and a second edge-cut portion (10), the second edge-cut portion (10) has an interference point that interferes with the image end lens (8), and the maximum distance e from the interference point to the inner annular surface of the second edge-cut portion (10) along the direction perpendicular to the optical axis and the width j of the second edge-cut portion (10) along the direction perpendicular to the optical axis satisfy the following conditions: 0.40≤e / j≤0.

60.

3. The lens structure according to claim 2, characterized in that: The width j of the second trimming portion (10) along a direction perpendicular to the optical axis and the thickness k of the variable spacer (9) along a direction parallel to the optical axis satisfy the following: 18≥j / k≥12.

4. The lens structure according to claim 1, characterized in that: The shortest distance a between the trimmed portion of the first lens (3) and the inner wall surface of the lens barrel (1) in a direction perpendicular to the optical axis satisfies: 0.05 mm ≤ a ≤ 0.1 mm.

5. The lens structure according to claim 1, characterized in that: The object side end of the lens barrel (1) has a notch portion (12) arranged corresponding to the first trimming portion (7), and a gap h between the notch portion (12) and the first trimming portion (7) along the optical axis direction and a length L of the first trimming portion (7) satisfy the following relationship: 0.005≤h / L≤0.

01.

6. The lens structure according to claim 1, characterized in that: A recessed structure facing away from the optical axis opening is formed at the connection between the first non-cutting edge portion (6) and the first cutting edge portion (7); the recessed structure comprises a first cross section (13), a transition arc surface (15) and a second cross section (14) which are connected in sequence; the extension direction of the first cross section (13) is parallel to the extension direction of the first cutting edge portion (7); the extension direction of the second cross section (14) is perpendicular to the extension direction of the first cutting edge portion (7); a gap b1 between the first cross section (13) and the lens barrel (1) and a gap b2 between the second cross section (14) and the lens barrel (1) satisfy the following relationship: 0.60≤b1 / b2≤1.

30.

7. The lens structure according to claim 6, characterized in that: The radius f of the transition arc surface (15) and the gap b1 between the first cross section (13) and the lens barrel (1) satisfy the following conditions:

8. The lens structure according to claim 6, characterized in that: The lens barrel (1) has a protruding structure that is buckled with the recessed structure, and the protruding length c of the inner ring surface of the protruding structure toward the recessed structure and the length L of the first trimming portion (7) satisfy the following relationship: 0.07≤c / L≤0.

09.

9. The lens structure according to claim 8, characterized in that: The gap b1 between the first cross section (13) and the lens barrel (1), the gap b2 between the second cross section (14) and the lens barrel (1), and the extension length c of the inner ring surface of the protruding structure toward the recessed structure satisfy the following relationship: 0.07≤(b1+b2) / 2c≤0.

19.

10. The lens structure according to any one of claims 1 to 9, characterized in that: The first trimming portion (7) has an arc surface (16) on the side facing the first lens (3), and the arc surface (16) is the same shape as the object side surface of the first lens (3) and is arranged at an interval.

11. The lens structure according to claim 10, characterized in that: The width i of the arc surface (16) along the direction perpendicular to the optical axis and the maximum distance i1 from the arc surface (16) to the outer annular surface of the first trimming portion (7) satisfy the following relationship: 0.4≤i / i1≤0.8.

Images