Large-aperture object-side telecentric lens

Abstract

This invention discloses a large-aperture telecentric object-side lens, comprising, along the optical axis from object-side to image-side, a first lens with positive optical power, a second lens with positive optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, an aperture stop, an eighth lens with negative optical power, and a ninth lens with positive optical power; wherein, the second to fourth lenses form a first cemented lens group, the fifth to seventh lenses form a second cemented lens group, and the eighth and ninth lenses form a third cemented lens group. This invention can satisfy the requirements of large aperture and high light throughput, and can be widely applied in the field of optical imaging technology.

Description

Technical Field

[0001] This invention relates to the field of optical imaging technology, and in particular to a large-aperture object-side telecentric lens. Background Technology

[0002] With the acceleration of industrial development, integration has become the direction of industrial development. The inspection of ultra-high precision integrated components requires corresponding inspection machines to ensure the quality of parts. Telecentric lenses are widely used in high-precision inspection due to their low distortion and constant magnification within a certain object distance range. High-magnification telecentric lenses have more advantages than low-magnification telecentric lenses in the inspection of precision and small parts. However, most of the telecentric lenses of the same type launched by manufacturers on the market at present generally have the disadvantages of small aperture and insufficient light throughput. Summary of the Invention

[0003] In view of this, the purpose of this invention is to provide a large-aperture object-side telecentric lens that can meet the requirements of large aperture and large light throughput.

[0004] In a first aspect, embodiments of the present invention provide a large-aperture object-side telecentric lens, comprising a first lens having positive optical power, a second lens having positive optical power, a third lens having negative optical power, a fourth lens having positive optical power, a fifth lens having negative optical power, a sixth lens having positive optical power, a seventh lens having negative optical power, an aperture stop, an eighth lens having negative optical power, and a ninth lens having positive optical power, arranged sequentially from the object side to the image side along the optical axis; wherein the second lens to the fourth lens form a first cemented lens group, the fifth lens to the seventh lens form a second cemented lens group, and the eighth lens and the ninth lens form a third cemented lens group.

[0005] Optionally, the first lens is a biconvex lens, the second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a meniscus lens, the sixth lens is a biconvex lens, the seventh lens is a biconcave lens, the eighth lens is a biconcave lens, and the ninth lens is a meniscus lens.

[0006] Optionally, the focal lengths of the first cemented lens group and the second cemented lens group satisfy the following relationship:

[0007] -0.7 <f z1 / f z2 <-0.2

[0008] Among them, f z1 f represents the focal length of the first cemented lens group. z2 This indicates the focal length of the second cemented lens group.

[0009] Optionally, the first cemented lens group and the second cemented lens group are the front lens group of the lens, and the focal length of the front lens group and the total focal length of the lens satisfy the following relationship:

[0010] 1.5 <f1 / f<2.5

[0011] Where f1 represents the focal length of the front lens group, and f represents the total focal length of the lens.

[0012] Optionally, the focal length of the third cemented lens group and the total focal length of the lens satisfy the following relationship:

[0013] -5.0 <f2 / f<-3.0

[0014] Where f2 represents the focal length of the third cemented lens group, and f represents the total focal length of the lens.

[0015] Optionally, the total length of the lens and the image height of the image plane satisfy the following relationship:

[0016] L / h<13

[0017] Where L represents the total length of the lens, and h represents the image height of the image plane.

[0018] Optionally, the materials of the eighth lens and the ninth lens include either fluorine crown glass or heavy phosphorus crown glass.

[0019] Implementing the embodiments of the present invention has the following beneficial effects: The lens in this embodiment achieves a large aperture and high light throughput by using a first cemented lens group consisting of a second lens with positive optical power, a third lens with negative optical power, and a fourth lens with positive optical power; a second cemented lens group consisting of a fifth lens with negative optical power, a sixth lens with positive optical power, and a seventh lens with negative optical power; and a third cemented lens consisting of an eighth lens with negative optical power and a ninth lens with positive optical power. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of a large-aperture telecentric lens provided in an embodiment of the present invention;

[0021] Figure 2 This is a distortion image of a large-aperture telecentric lens provided in an embodiment of the present invention;

[0022] Figure 3 This is an MTF chart of a large-aperture telecentric lens at 20°C, provided in an embodiment of the present invention.

[0023] Figure 4 This is an MTF chart of a large-aperture telecentric lens at -60°C provided in an embodiment of the present invention;

[0024] Figure 5 This is an MTF chart of a large-aperture telecentric lens at 60°C, provided in an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The step numbers in the following embodiments are only for ease of explanation and do not limit the order of the steps. The execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.

[0026] like Figure 1 As shown, this embodiment of the invention provides a large-aperture object-side telecentric lens, comprising a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens L4 with positive optical power, a fifth lens L5 with negative optical power, a sixth lens L6 with positive optical power, a seventh lens L7 with negative optical power, an aperture stop, an eighth lens L8 with negative optical power, and a ninth lens L9 with positive optical power, arranged sequentially from the object side to the image side along the optical axis; wherein, the second lens L2 to the fourth lens L4 form a first cemented lens group, the fifth lens L5 to the seventh lens L7 form a second cemented lens group, and the eighth lens L8 and the ninth lens L9 form a third cemented lens group.

[0027] Optionally, the first lens is a biconvex lens, the second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a meniscus lens, the sixth lens is a biconvex lens, the seventh lens is a biconcave lens, the eighth lens is a biconcave lens, and the ninth lens is a meniscus lens.

[0028] Optionally, the focal lengths of the first cemented lens group and the second cemented lens group satisfy the following relationship:

[0029] -0.7 <f z1 / f z2 <-0.2

[0030] Among them, f z1 f represents the focal length of the first cemented lens group. z2 This indicates the focal length of the second cemented lens group.

[0031] Optionally, the first cemented lens group and the second cemented lens group are the front lens group of the lens, and the focal length of the front lens group and the total focal length of the lens satisfy the following relationship:

[0032] 1.5 <f1 / f<2.5

[0033] Where f1 represents the focal length of the front lens group, and f represents the total focal length of the lens.

[0034] Optionally, the focal length of the third cemented lens group and the total focal length of the lens satisfy the following relationship:

[0035] -5.0 <f2 / f<-3.0

[0036] Where f2 represents the focal length of the third cemented lens group, and f represents the total focal length of the lens.

[0037] Optionally, the total length of the lens and the image height of the image plane satisfy the following relationship:

[0038] L / h<13

[0039] Where L represents the total length of the lens, and h represents the image height of the image plane.

[0040] Optionally, the material of the eighth to the ninth lenses includes either fluorine crown glass or heavy phosphorus crown glass.

[0041] It should be noted that the anechoic effect of telecentric lenses currently on the market is not ideal, and they require focusing to be used in different temperature environments. Anechoic effects can be achieved by using temperature-sensitive optical glass materials such as fluorine crown glass or heavy phosphorus crown glass to adjust the image plane shift at high and low temperatures.

[0042] Implementing the embodiments of the present invention has the following beneficial effects: The lens in this embodiment achieves a large aperture and high light throughput by using a first cemented lens group consisting of a second lens with positive optical power, a third lens with negative optical power, and a fourth lens with positive optical power; a second cemented lens group consisting of a fifth lens with negative optical power, a sixth lens with positive optical power, and a seventh lens with negative optical power; and a third cemented lens consisting of an eighth lens with negative optical power and a ninth lens with positive optical power.

[0043] The lens in this application is described below with a specific embodiment. For specific design parameters, please refer to Table 1, where R represents the radius of curvature of the lens, d represents the lens thickness or air gap (where 0.21 / 4.19 / 28.20 / 88.00 / 44.54 in Table 1 represent air gaps, and the rest represent lens thickness), n represents the refractive index of the lens, and v represents the Abbe number of the lens. Specifically, S1 represents the first surface of the first lens L1 along the optical axis, S2 represents the second surface of the first lens L1 along the optical axis, S3 represents the first surface of the second lens L2 along the optical axis, S4 represents the cemented surface between the second lens L2 and the third lens L3, S5 represents the cemented surface between the third lens L3 and the fourth lens L4, S6 represents the second surface of the fourth lens L4 along the optical axis, S7 represents the first surface of the fifth lens L5 along the optical axis, S8 represents the cemented surface between the fifth lens L5 and the sixth lens L6, S9 represents the cemented surface between the sixth lens L6 and the seventh lens L7, S10 represents the second surface of the seventh lens L7 along the optical axis, the Stop surface represents the aperture stop, S13 represents the first surface of the eighth lens L8 along the optical axis, S14 represents the cemented surface between the eighth lens L8 and the ninth lens L9, and S15 represents the second surface of the ninth lens L9 along the optical axis.

[0044] Table 1

[0045] Lens serial number Face number R d n v L1 S1 1333.09 3.42 1.59 68.3 S2 -46.67 0.21 L2 S3 107.84 4.51 1.69 49.2 L3 S4 -41.13 1.00 1.78 25.7 L4 S5 33.10 4.36 1.95 17.9 S6 -398.05 4.19 L5 S7 59.79 1.00 1.74 28.3 L6 S8 25.90 5.95 1.57 57.5 L7 S9 -50.06 1.00 1.85 23.8 S10 143.43 28.20 Stop Infinity 88.00 L8 S13 -19.31 1.00 1.50 81.6 L9 S14 31.05 2.52 1.91 35.2 S15 958.75 44.54

[0046] Specifically, the test results of Example 1 are as follows: Figures 2-5 As shown: Figure 2 It includes distortion diagrams for three wavelengths: 435nm, 546nm, and 656nm. Figure 2 It can be seen that the distortion of the large-aperture telecentric lens in this application is less than 0.12%, which is small; from Figures 3 to 5 It is known that the large-aperture telecentric lens in this application can still maintain an MTF of over 0.25 at room temperature (20℃), low temperature (-60℃), and high temperature (60℃) with a spatial frequency of 85 cycles / mm, demonstrating good thermal performance.

[0047] It should be noted that in Embodiment 1, the first lens is a positive lens, the first set of cemented lenses is a triple-cemented lens with a positive-negative-positive configuration, and the second set of cemented lenses is a triple-cemented lens with a negative-positive-negative configuration, used to correct chromatic aberration; behind the aperture, a set of cemented doublet lenses is used, with fluorine crown glass as a negative power lens. Taking advantage of the large temperature coefficient of refractive index of fluorine crown glass, the image plane shift at different temperatures is corrected, thereby achieving a heatless lens and also correcting chromatic aberration.

[0048] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A large-aperture telecentric lens, characterized in that, The system includes a first lens with positive optical power, a second lens with positive optical power, a third lens with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, a sixth lens with positive optical power, a seventh lens with negative optical power, an aperture stop, an eighth lens with negative optical power, and a ninth lens with positive optical power, arranged sequentially from the object side to the image side along the optical axis. The second to fourth lenses form a first cemented lens group, the fifth to seventh lenses form a second cemented lens group, and the eighth and ninth lenses form a third cemented lens group. The first lens is a biconvex lens, the second lens is a biconvex lens, the third lens is a biconcave lens, the fourth lens is a biconvex lens, the fifth lens is a meniscus lens, the sixth lens is a biconvex lens, the seventh lens is a biconcave lens, the eighth lens is a biconcave lens, and the ninth lens is a meniscus lens. The focal lengths of the first cemented lens group and the second cemented lens group satisfy the following relationship: -0.7<f z1 / f z2 <-0.2 Among them, f z1 f represents the focal length of the first cemented lens group. z2 Indicates the focal length of the second cemented lens group; The first cemented lens group and the second cemented lens group constitute the front lens group of the lens, and the focal length of the front lens group and the total focal length of the lens satisfy the following relationship: 1.5 <f1 / f<2.5 Where f1 represents the focal length of the front lens group, and f represents the total focal length of the lens; The focal length of the third cemented lens group and the total focal length of the lens satisfy the following relationship: -5.0 <f2 / f<-3.0 Where f2 represents the focal length of the third cemented lens group; The total length of the lens and the image height of the image plane satisfy the following relationship: L / h<13 Where L represents the total length of the lens, and h represents the image height of the image plane.

2. The lens according to claim 1, characterized in that, The materials of the eighth lens and the ninth lens include either fluorine crown glass or heavy phosphorus crown glass.

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