A high-throughput, high-definition, low-distortion machine vision lens and focusing method thereof

Abstract

The present invention relates to a high-definition, low-distortion machine vision lens with large light transmission and a focusing method thereof. The lens comprises a front lens group, an aperture, and a rear lens group which are arranged in sequence along the incident direction of light in a lens structure; the front lens group is composed of a negative meniscus lens, a first positive meniscus lens, a first biconvex lens, and a first cemented group of closely connected biconcave lenses in sequence from front to back; the rear lens group is provided with a second biconcave lens, a second cemented group of closely connected biconvex lenses, a third biconvex lens, and a second positive meniscus lens in sequence from front to back. The lens has the characteristics of large light transmission and low distortion. The focusing method thereof adopts a half-group translation focusing method, which ensures high-definition imaging of the lens at close range; and can provide high-resolution imaging with better than 20 million pixels for a machine vision system; the machine vision lens is used for vision-related detection applications such as liquid crystal display bad pixel detection, FPC component detection, and circuit board detection.

Description

Technical Field

[0001] The invention relates to a high-throughput, high-definition, low-distortion machine vision lens and a focusing method thereof. Background Art

[0002] With the rapid development of machine vision, small-clearance and small-target machine vision inspection lenses can no longer fully meet the needs of all visual inspection industries. Today, with the development of the electronics industry, especially the inspection of liquid crystal display panels, mobile phone circuit boards, etc., larger target areas and larger clearance lenses are needed to replace inspections. Summary of the invention

[0003] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a large-light-through, high-definition, low-distortion machine vision lens and a focusing method thereof, which not only has a reasonable structure, but also has high optical performance, a large imaging target surface, a large light-through aperture, a resolution better than 20 million pixels, and high-resolution imaging with a distortion less than 0.4%.

[0004] In order to solve the above technical problems, the technical solution of the present invention is: a large-light transmission, high-definition and low-distortion machine vision lens, comprising a front group of lenses, an aperture, and a rear group of lenses arranged in sequence along the incident direction of light in the lens structure; the front group of lenses is composed of a negative meniscus lens, a first positive meniscus lens, a first biconvex lens and a first cemented group of a first biconcave lens in close contact from front to back, and the rear group of lenses is provided in sequence from front to back: a second biconcave lens and a second cemented group of the second biconvex lens in close contact, a third biconvex lens, and a second positive meniscus lens.

[0005] Furthermore, the air gap between the negative meniscus lens and the first positive meniscus lens is 12.07 mm, and the air gap between the first positive meniscus lens and the first cemented group is 3.62 mm.

[0006] Furthermore, the air space between the front lens group and the rear lens group is 10.19 mm, the air space between the front lens group and the diaphragm is 1.34 mm, and the air space between the diaphragm and the rear lens group is 8.85 mm.

[0007] Furthermore, the air gap between the second bonding group and the third biconvex lens is 0.1 mm, and the air gap between the third biconvex lens and the second positive meniscus lens is 0.94 mm.

[0008] Furthermore, the lens structure includes a front group barrel for installing a front group of lenses, the rear side of the front group barrel is connected to a main barrel, a rear group barrel for installing a rear group of lenses is arranged inside the main barrel, the rear group barrel is matched with the front group barrel by three first countersunk screws and threadedly fastened, thereby forming an integrated linkage, and an aperture adjustment mechanism is arranged on the main barrel; a focusing mechanism is also arranged on the main barrel.

[0009] Furthermore, the negative meniscus lens, the first positive meniscus lens, the first biconvex lens and the first biconcave lens are arranged in sequence from front to back in the front group barrel; a first spacer ring is arranged between the negative meniscus lens and the first positive meniscus lens, a second spacer ring is arranged between the first positive meniscus lens and the first cemented group, and a front pressure ring is also screwed in the front group barrel and pressed on the front side of the negative meniscus lens.

[0010] Furthermore, the second double concave lens, the second double convex lens, and the third double convex lens are arranged in sequence from front to back in the rear group barrel, a third spacer ring is arranged between the second bonding group and the third double convex lens, a middle pressure ring is arranged outside the third double convex lens to cooperate with the rear group barrel, and a connecting flange is arranged outside the rear end of the main barrel, and the connecting flange is assembled with the second positive meniscus lens by threaded connection to the rear pressure ring.

[0011] Furthermore, the aperture adjustment mechanism includes an aperture ring sleeved on the middle part of the main tube, and the aperture ring is radially threaded with an aperture guide pin that passes through the main tube and extends into the rear tube. The aperture guide pin is connected to the aperture, and the aperture adjustment ring is also provided with an iris fastening screw that cooperates with the main tube for locking the aperture ring.

[0012] Furthermore, the focusing mechanism includes a focusing cam arranged on the main tube, the rear end of the inner ring of the focusing cam is screwed to the front end outer ring of the main tube, and the rear end of the outer ring of the focusing cam is screwed to the front end inner ring of the main tube outer cover, a focusing ring is also fixed on the focusing cam, and a focusing fastening screw for locking the focusing cam is radially screwed on the main tube.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] Through careful design of the optical path, the optical glass materials of the system's eight lenses in six groups are reasonably selected, and the refractive index and dispersion differences between the cemented lens groups are utilized to effectively correct aberrations, making the MTF value of the lens 150lp / mm≥0.75 at the center and 150lp / mm≥0.35 at the edge, making the resolution of the lens better than 20 million pixels.

[0015] It has the characteristics of large light transmission and low distortion. Its focusing method adopts a half-group translation focusing method, which ensures high-definition imaging of the lens at close range with a distortion of less than 0.4%.

[0016] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the optical path system according to an embodiment of the present invention;

[0018] Figure 2 This is an exploded schematic diagram of the lens structure of an embodiment of the present invention;

[0019] Figure 3 is an MTF curve diagram of an embodiment of the present invention;

[0020] Figure 4 4 is a distortion change curve diagram of an embodiment of the present invention.

[0021] In the figure: 1-focusing ring, 2-front pressure ring, 3-first spacer ring, 4-second spacer ring, 5-front group barrel, 6-pin, 7-first cone end screw, 8-first countersunk screw, 9-focusing cam, 10-main barrel, 11-rear group barrel, 12-third spacer ring, 13-middle pressure ring, 14-rear pressure ring, 15-main barrel cover, 16-aperture ring, 17-connecting flange, 18-second cone end screw, 19-negative meniscus lens, 20-first positive meniscus lens, 21-first cemented group, 22-aperture, 23-spiral inclined groove, 24-double U straight guide Slot, 25-aperture limiting slot, 26-second cementing group, 27-third biconvex lens, 28-second positive meniscus lens, 29-focusing fastening screw, 30-second countersunk screw, 31-aperture guide pin, 32-aperture fastening screw, 33-third countersunk screw, 36-first biconvex lens, 37-first biconcave lens, 38-second biconcave lens, 39-second biconvex lens, A-front lens group, B-rear lens group. DETAILED DESCRIPTION

[0022] In order to make the above features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description.

[0023] like Figures 1 to 4 As shown, a high-definition, low-distortion machine vision lens with large light transmission, includes a front lens group A, an aperture 16, and a rear lens group B arranged in sequence along the incident direction of light in the lens structure; the front lens group is composed of a negative meniscus lens 19, a first positive meniscus lens 20, a first biconvex lens 36, and a first biconcave lens 37 in close contact with a first cemented group 21, and the rear lens group is provided with a second biconcave lens 38 and a second cemented group 26 in close contact with the second biconvex lens 39, a third biconvex lens 27, and a second positive meniscus lens 28 in sequence from front to back. The overall outer size of the lens is designed to be φ42.0mm×74.7mm.

[0024] In the embodiment of the present invention, the air gap between the negative meniscus lens and the first positive meniscus lens is 12.07 mm, and the air gap between the first positive meniscus lens and the first cemented group is 3.62 mm.

[0025] In the embodiment of the present invention, the air space between the front lens group and the rear lens group is 10.19 mm, the air space between the front lens group and the diaphragm is 1.34 mm, and the air space between the diaphragm and the rear lens group is 8.85 mm.

[0026] In the embodiment of the present invention, the air gap between the second cemented group and the third biconvex lens is 0.1 mm, and the air gap between the third biconvex lens and the second positive meniscus lens is 0.94 mm.

[0027] In the embodiment of the present invention, the optical path design utilizes the differences in refractive index and dispersion between the cemented lens groups, thereby effectively correcting aberrations; the lens has the characteristics of large light transmission and low distortion, and its focusing method adopts a half-group translation focusing method, which ensures high-definition imaging of the lens at close range; it can provide high-resolution imaging better than 20 million pixels for machine vision systems.

[0028] In the embodiment of the present invention, the lens structure includes a front group barrel 5 for installing a front group of lenses, the rear side of the front group barrel is connected to a main barrel 10, a rear group barrel 11 for installing a rear group of lenses is arranged in the main barrel, the rear group barrel is matched with the front group barrel by three first countersunk screws 8 and threadedly fastened, thereby forming an integrated linkage, and an aperture adjustment mechanism is arranged on the main barrel; a focusing mechanism is also arranged on the main barrel.

[0029] In an embodiment of the present invention, the negative meniscus lens, the first positive meniscus lens, the first biconvex lens and the first biconcave lens are arranged in sequence from front to back in the front group barrel; a first spacer ring 3 is arranged between the negative meniscus lens and the first positive meniscus lens, and a second spacer ring 4 is arranged between the first positive meniscus lens and the first bonding group, and a front pressure ring 2 pressed on the front side of the negative meniscus lens is also screwed in the front group barrel; the front group barrel, the spacer ring and the front pressure ring are all processed and formed by a turning and milling compound machine at one time, with stronger consistency and higher precision, effectively ensuring the concentricity of the inner diameters of the front group barrel and ensuring the coaxiality of the lens assembly, wherein the convex bearing parts of the first spacer ring, the second spacer ring and the first positive meniscus lens and the first bonding group adopt C0.1 chamfer bearing, so that the lens is not easy to be scratched or cracked, and the air distance between the lenses can be effectively guaranteed, and a main barrel outer cover 15 is arranged outside the main barrel, and the outer periphery of the main barrel outer cover is locked and fixed to the main barrel by three second countersunk screws 30.

[0030] In the embodiment of the present invention, the second double concave lens, the second double convex lens, and the third double convex lens are arranged in sequence from front to back in the rear group barrel, a third spacer ring 12 is arranged between the second glued group and the third double convex lens, a middle pressure ring 13 is arranged outside the third double convex lens to cooperate with the rear group barrel, and a connecting flange 17 is arranged outside the rear end of the main barrel, and the connecting flange is assembled with the second positive meniscus lens through a threaded connection with the rear pressure ring; the third spacer ring is designed to ensure the air distance between the lenses, and the inner wall of the third spacer ring is designed to be a matte step pattern, which effectively avoids the refraction of invalid light and improves the imaging quality of the lens; and the middle pressure ring is designed to cooperate with the rear group barrel to ensure the assembly coaxiality and stability of the three lenses in the rear group and the two groups of lenses; in order to meet the requirements of the lens to achieve half-group movement, the inner wall of the connecting flange is sleeved on the outer periphery of the main barrel, and is locked and fixed by the bearing surface and three third countersunk screws 33, thereby realizing a half-group translation focusing method.

[0031] In an embodiment of the present invention, the aperture adjustment mechanism includes an aperture ring 16 sleeved on the middle part of the main tube, and an aperture guide pin 31 is radially threaded on the aperture ring and passes through the main tube and extends into the rear group tube. The aperture guide pin is connected to the aperture, and the aperture adjustment ring is also provided with an aperture fastening screw 32 that cooperates with the main tube and is used to lock the aperture ring, so as to meet the requirements of different detection environments by adjusting the aperture size to ensure the shooting brightness; in order to improve the stability of its lens, its aperture adjustment mechanism adopts an integrated manual aperture, and locks it to the inner wall of the rear end of the front main tube by two first cone-end screws 7; in order to avoid the extreme use of the aperture angle, an aperture limit groove 25 is also designed on the main tube to limit the aperture angle.

[0032] In the embodiment of the present invention, the focusing mechanism includes a focusing cam 9 arranged on the main barrel, the rear end of the inner ring of the focusing cam is screwed to the front end outer ring of the main barrel, and the rear end of the outer ring of the focusing cam is screwed to the front end inner ring of the main barrel outer cover, a focusing ring 1 is also fixed on the focusing cam, and a focusing fastening screw 29 for locking the focusing cam is radially screwed on the main barrel; the focusing mechanism adopts a "spiral bevel groove + sliding pin" structural design; at the same time, in order to ensure that the lens does not move axially along the optical axis during the focusing process, a "double U straight guide groove limit slider" mechanism is designed;

[0033] The focusing method is as follows: three spiral bevel grooves 23 are used on the periphery of the focusing cam and are evenly distributed at 360°, and the spiral bevel grooves are designed to be counterclockwise; in order to make the front and rear barrel groups work together to perform linear focusing, three double U straight guide grooves 24 that cooperate with the spiral bevel grooves are designed on the periphery of the main barrel, and then the front barrel group is locked and limited in the three spiral bevel grooves and three double U straight guide grooves of the focusing cam by three pins 6, and the focusing ring is inserted into the periphery of the focusing cam and locked and fixed by three second cone-end screws 18, and finally the focusing cam is driven to perform circular motion by adjusting the focusing ring, thereby driving the front and rear barrel groups to work together and perform linear focusing actuation.

[0034] In the embodiment of the present invention, the optical path is carefully designed, the optical glass materials of the eight lenses and six groups of the system are reasonably selected, and the refractive index and dispersion differences between the cemented lens groups are utilized to effectively correct the aberration, so that the MTF value of the lens is 150lp / mm≥0.75 at the center and 150lp / mm≥0.35 at the edge (such as Figure 3 ), making the lens resolution better than 20 million pixels.

[0035] The optical path is carefully designed to have the characteristics of large light transmission and low distortion. The focusing method adopts a half-group translation focusing method, which ensures high-definition imaging of the close-up shooting of the lens with a distortion of less than 0.4% (such as Figure 4 ).

[0036] In the embodiment of the present invention, the parameters of each lens are shown in the following table:

[0037]

[0038] The technical indicators achieved by the present invention are as follows:

[0039] ①Image size: 1.1"

[0040] ②Focal length: f´=35mm

[0041] ③Relative aperture: F2.0~F16

[0042] ④Distortion: ≤0.4%

[0043] ⑤ Resolution: better than 20 million pixels

[0044] ⑥Total length of optical path: ≤74.86±0.1mm

[0045] ⑦Applicable spectral range: 400nm~700nm

[0046] ⑧Dimensions: φ42.0mm×74.7mm

[0047] The present invention is not limited to the above-mentioned best implementation mode. Anyone can derive other forms of high-throughput, high-definition, low-distortion machine vision lenses and focusing methods thereof under the inspiration of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims

1. A high-resolution, low-distortion machine vision lens, characterized by: The lens comprises a front lens group, a diaphragm and a rear lens group which are arranged in sequence along the incident direction of light in the lens structure; the front lens group comprises, from front to back, a negative meniscus lens, a first positive meniscus lens, a first biconvex lens and a first cemented group of closely connected biconcave lenses; the rear lens group comprises, from front to back, a second biconcave lens and a second cemented group of closely connected biconvex lenses, a third biconvex lens and a second positive meniscus lens; The air gap between the negative meniscus lens and the first positive meniscus lens is 12.07 mm, and the air gap between the first positive meniscus lens and the first cemented group is 3.62 mm; The air gap between the front lens group and the rear lens group is 10.19mm, the air gap between the front lens group and the diaphragm is 1.34mm, and the air gap between the diaphragm and the rear lens group is 8.85mm; The air gap between the second glued group and the third biconvex lens is 0.1 mm, and the air gap between the third biconvex lens and the second positive meniscus lens is 0.94 mm.

2. The high-throughput, high-definition, low-distortion machine vision lens according to claim 1, characterized in that: The lens structure includes a front group barrel for installing the front group lens, the rear side of the front group barrel is connected to a main barrel, a rear group barrel for installing the rear group lens is arranged inside the main barrel, the rear group barrel is matched with the front group barrel by three first countersunk screws and threadedly fastened, and an aperture adjustment mechanism is arranged on the main barrel; the main barrel is also provided with a focusing mechanism.

3. The high-throughput, high-definition, low-distortion machine vision lens according to claim 2, characterized in that: The negative meniscus lens, the first positive meniscus lens, the first biconvex lens and the first biconcave lens are arranged in sequence from front to back in the front group barrel; a first spacer ring is arranged between the negative meniscus lens and the first positive meniscus lens, a second spacer ring is arranged between the first positive meniscus lens and the first cemented group, and a front pressure ring is also screwed in the front group barrel and pressed on the front side of the negative meniscus lens.

4. A high-throughput, high-definition, low-distortion machine vision lens according to claim 2 or 3, characterized in that: The second double concave lens, the second double convex lens, and the third double convex lens are arranged in sequence from front to back in the rear group barrel, a third spacer ring is arranged between the second bonding group and the third double convex lens, a middle pressure ring is arranged outside the third double convex lens to cooperate with the rear group barrel, and a connecting flange is arranged outside the rear end of the main barrel, and the connecting flange is assembled with the second positive meniscus lens by threaded connection to the rear pressure ring.

5. The high-throughput, high-definition, low-distortion machine vision lens according to claim 2, characterized in that: The aperture adjustment mechanism includes an aperture ring sleeved on the middle part of the main tube, and the aperture ring is radially threaded with an aperture guide pin that passes through the main tube and extends into the rear group tube. The aperture guide pin is connected to the aperture, and the aperture adjustment ring is also provided with an aperture fastening screw that cooperates with the main tube for locking the aperture ring.

6. The high-throughput, high-definition, low-distortion machine vision lens according to claim 2, characterized in that: The focusing mechanism includes a focusing cam arranged on the main tube, the rear end of the inner ring of the focusing cam is screwed to the front end outer ring of the main tube, and the rear end of the outer ring of the focusing cam is screwed to the front end inner ring of the main tube outer cover, a focusing ring is also fixed on the focusing cam, and a focusing fastening screw for locking the focusing cam is radially screwed on the main tube.

Images