Large-target-area, high-definition, low-distortion industrial lens and focusing method thereof

Abstract

The present invention relates to a large-target-surface high-definition low-distortion industrial lens and a focusing method thereof. The optical system of the lens is composed of a front lens group A, an aperture C, and a rear lens group B arranged in sequence from front to back along an incident light path; the front lens group A is composed of a first cemented group of positive meniscus lens A-1, positive meniscus lens A-2, biconvex lens A-3, and biconcave lens A-4 arranged in sequence from front to back in close contact; the rear lens group B is composed of a second cemented group of negative meniscus lens B-1 and positive meniscus lens B-2 arranged in sequence from front to back in close contact, and a third cemented group of biconvex lens B-3, positive meniscus lens B-4, and negative meniscus lens B-5 in close contact. The large-target-surface high-definition low-distortion industrial lens of the present invention realizes large-target-surface imaging, large clear light path, low distortion, and high resolution, adopts a half-group focusing method, effectively ensures high-definition imaging during close-range shooting, and provides a resolution better than 20 million pixels for industrial imaging systems.

Description

Technical Field

[0001] The invention relates to a large-target-surface, high-definition, low-distortion industrial lens and a focusing method thereof. Background Art

[0002] With the rapid development of science and technology and the continuous deepening of human exploration of science and technology, industrial automation has entered the "machine vision era". By combining industrial lenses with industrial cameras, industrial inspection, high-precision measurement, defect detection, positioning and identification, etc., the efficiency and results of industrial manufacturing have been greatly improved; especially in some working environments that cannot be touched by humans, they can be achieved through machine vision technology, and effectively protect human interests and safety. In the future industrial development, machine vision technology will gradually replace manual operations, reduce labor costs, and improve work efficiency. Summary of the invention

[0003] In view of this, an object of the present invention is to provide a large target surface, high-definition, low-distortion industrial lens with large target surface imaging, large clear diameter, high resolution, and a focusing method thereof.

[0004] The present invention is implemented by the following scheme: a large-target-area, high-definition, low-distortion industrial lens, wherein the optical system of the lens consists of a front lens group A, an aperture C, and a rear lens group B arranged in sequence from front to back along an incident light path; the front lens group A consists of a first cemented group of a positive meniscus lens A-1, a positive meniscus lens A-2, a biconvex lens A-3, and a biconcave lens A-4 arranged in sequence from front to back, which are closely connected; the rear lens group B consists of a second cemented group of a negative meniscus lens B-1 and a positive meniscus lens B-2 arranged in sequence from front to back, which are closely connected, and a third cemented group of a biconvex lens B-3, a positive meniscus lens B-4, and a negative meniscus lens B-5 arranged in sequence from front to back, which are closely connected.

[0005] Furthermore, the air gap between the front lens group A and the rear lens group B is 7.562mm, and the air gap between the front lens group A and the aperture C is 2.593mm; the air gap between the positive meniscus lens A-1 and the positive meniscus lens A-2 in the front lens group A is 3.445mm, and the air gap between the positive meniscus lens A-2 and the first cemented group is 0.1mm; the air gap between the second cemented group and the biconvex lens B-3 in the rear lens group B is 3.587mm, and the air gap between the biconvex lens B-3 and the third cemented group is 8.385-8.795mm.

[0006] Furthermore, the mechanical structure of the lens includes a main sleeve, in which an inner hole of the main sleeve is installed a front lens barrel that can move axially relative to the main sleeve, a front lens group A is installed at the front of the inner hole of the front lens barrel, a rear lens barrel is fixedly installed at the rear of the inner hole of the front lens barrel, a second bonding group of the rear lens group B and a double convex lens B-3 are installed in the inner hole of the rear lens barrel; a lens base is fixedly connected to the rear end of the main sleeve, a third bonding group of the rear lens group B is installed in the inner hole of the lens base, and a focusing mechanism for controlling the forward and backward movement of the front lens barrel and the rear lens barrel is installed on the main sleeve.

[0007] Another technical solution of the present invention is a focusing method for a large-target-area, high-definition, low-distortion industrial lens as described above, which adopts a half-group focusing method and realizes focusing by controlling the front and rear lens barrels to move forward and backward in a straight line through a focusing mechanism.

[0008] Compared with the prior art, the present invention has the following beneficial effects: the large-target-area, high-definition, low-distortion industrial lens of the present invention realizes large-target-area imaging, large clear light path, low distortion and high resolution, adopts a half-group focusing method, effectively ensures high-definition imaging during close-range shooting, and provides a resolution better than 20 million pixels for industrial imaging systems.

[0009] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through specific embodiments and related drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a structural diagram of the lens optical system of an embodiment of the present invention;

[0011] Figure 2 is a cross-sectional view of the overall structure of a lens according to an embodiment of the present invention;

[0012] Figure 3 This is an MTF curve diagram of the lens according to an embodiment of the present invention;

[0013] Figure 4 is a lens distortion variation curve of an embodiment of the present invention;

[0014] Explanation of the numbers in the figure: 1-filter size, 2-front lens barrel, 3-focusing cam, 4-screw A, 5-focusing ring, 6-locating pin, 7-outer cover, 8-countersunk screw A, 9-aperture, 10-aperture nail, 11-aperture limit groove, 12-rear lens barrel, 13-aperture crank, 14-countersunk screw B, 15-C-Mount, 16-lens base, 17-rear pressure ring, 18-front pressure ring, 19-limiting straight groove, 20-spacer A, 21-oblique groove, 22-spacer B, 23-focus fixing screw Nail, 24-screw B, 25-countersunk screw C, 26-main sleeve, 27-aperture fixing screw, 28-spacer C, 29-aperture ring, 30-intermediate pressure ring, 31-positive meniscus lens, 32-positive meniscus lens, 33-double convex lens, 34-double concave lens, 35-aperture C, 36-negative meniscus lens, 37-positive meniscus lens, 38-double convex lens, 39-positive meniscus lens, 40-negative meniscus lens, 41-imaging surface, 42-first bonding group, 43-second bonding group, 44-third bonding group. DETAILED DESCRIPTION

[0015] like Figures 1 to 4 As shown, a large-target-area, high-definition, low-distortion industrial lens, the optical system of the lens consists of a front lens group A, an aperture C, and a rear lens group B arranged in sequence from front to back along the incident light path; the front lens group A consists of a first cemented group of a positive meniscus lens A-1, a positive meniscus lens A-2, a biconvex lens A-3, and a biconcave lens A-4 arranged in sequence from front to back, which are closely connected; the rear lens group B consists of a second cemented group of a negative meniscus lens B-1 and a positive meniscus lens B-2, and a third cemented group of a biconvex lens B-3, a positive meniscus lens B-4, and a negative meniscus lens B-5, which are closely connected and arranged in sequence from front to back.

[0016] In this embodiment, the air gap between the front lens group A and the rear lens group B is 7.562 mm, and the air gap between the front lens group A and the aperture C is 2.593 mm; the air gap between the positive meniscus lens A-1 and the positive meniscus lens A-2 in the front lens group A is 3.445 mm, and the air gap between the positive meniscus lens A-2 and the first cemented group is 0.1 mm; the air gap between the second cemented group and the biconvex lens B-3 in the rear lens group B is 3.587 mm, and the air gap between the biconvex lens B-3 and the third cemented group is 0.1 mm. The air gap between the groups is 8.385-8.795mm, and the air gap between the third cemented group 44 and the imaging surface 41 in the rear lens group B is: 11.805mm; the industrial lens optical system is designed as six groups of nine glass lenses, and adopts a half-group focusing method, which effectively ensures high-definition imaging during close-range shooting and provides a resolution better than 20 million pixels for the industrial imaging system; the industrial lens can be used for related industrial detection applications such as industrial assembly precision alignment, mechanical parts size measurement, and defect detection.

[0017] The specific parameters of each lens in the lens of the present invention are shown in the following table:

[0018]

[0019] The technical indicators achieved by the lens optical system of the present invention are as follows:

[0020] ①Target surface specification: 1.1";

[0021] ②Focal length: f´=50mm;

[0022] ③Relative aperture: F2.0;

[0023] ④Distortion: ≤0.5%;

[0024] ⑤ Resolution: better than 20 million pixels;

[0025] ⑥Total length of optical path: ≤62.524±0.1mm;

[0026] ⑧Interface type: C-Mount;

[0027] ⑨Aperture and focus mode: manual adjustment.

[0028] The optical system of this industrial lens is carefully selected with nine lens glass materials in six groups of front and rear groups, and the refractive index between the front and rear lens groups is reasonably and effectively matched. Through reasonable optimization simulation, astigmatism, chromatic aberration and distortion are corrected. When the center of the lens is 150lp / mm, the MTF value is ≥0.45; when the edge is 150lp / mm, the MTF value is ≥0.35 (such as Figure 3 ), so that the imaging resolution of the optical system is better than 20 million pixels and the distortion is ≤ 0.5% (such as Figure 2 ).

[0029] In this embodiment, the mechanical structure of the lens includes a main sleeve 26, in which an inner hole of the main sleeve 26 is installed a front lens barrel 2 that can move axially relative to the main sleeve 26, in which a front lens group A is installed at the front of the inner hole of the front lens barrel 2, in which a rear lens barrel 12 is fixedly installed at the rear of the inner hole of the front lens barrel 2, in which a second bonding group of the rear lens group B and a double convex lens B-3 are installed at the inner hole of the rear lens barrel 12; the rear end of the main sleeve 26 is fixedly connected to a lens base 16, in which a third bonding group of the rear lens group B is installed at the inner hole of the lens base 16, and a focusing mechanism for controlling the forward and backward movement of the front lens barrel and the rear lens barrel is installed on the main sleeve 26.

[0030] The front lens barrel 2 is provided with a front pressure ring 18, a positive meniscus lens A-1, a spacer A, a positive meniscus lens A-2, a spacer B and a first cementing group 42 in sequence from front to back along the incident direction of the light. The inner and outer diameters of the front lens barrel 2 are formed in one step by a CNC lathe, and the coaxiality of the inner and outer diameters is controlled within 0.01mm, which effectively ensures the coaxiality of the front lens group and the spacer; wherein the spacer A is used to ensure the air gap between the positive meniscus lens A-1 and the positive meniscus lens A-2, and the spacer B is used to ensure the air gap between the positive meniscus lens A-2 and the first bonding group 42; in order to reduce the influence of incident stray light on the imaging of the lens optical system, the inner periphery of the spacer A and the spacer B is designed to be a step extinction pattern, and the stray light is effectively reduced by the refraction and reflection of the extinction pattern, thereby ensuring the imaging quality of the lens; wherein the outer periphery of the front pressure ring is designed with an external thread that cooperates with the internal thread at the front of the front lens barrel, and abuts against the edge of the front end surface of the positive meniscus lens A-1, thereby effectively ensuring the coaxiality of the front lens group and the stability of the structure; further, in order to meet the needs of customers to install filters, a filter size 1 is also designed at the front of the front barrel, the function of which is that different customers may choose suitable filters by themselves.

[0031] The rear lens barrel 12 is provided with a second bonding group 43, a spacer ring C, a biconvex lens B-3 and a middle pressure ring in sequence from front to back along the incident direction of light. The inner and outer diameters of the rear lens barrel 12 are formed by one-time processing using a CNC lathe, and the coaxiality of the inner and outer diameters is controlled within 0.01mm, which effectively ensures the coaxiality of the front lens group and the spacer ring. The spacer ring C is used to ensure the air gap between the second bonding group 43 and the biconvex lens B-3. Similarly, the inner periphery of the spacer ring C is designed to be a step extinction pattern, which effectively reduces stray light through the refraction and reflection of the extinction pattern, thereby ensuring the imaging quality of the lens. ; The outer periphery of the intermediate pressure ring is designed with an external thread which cooperates with the internal thread at the rear of the rear barrel and abuts against the right side of the double convex lens B-3, thereby effectively ensuring the coaxiality of the second bonding group 43, the spacer ring C, and the double convex lens B-3 and the stability of the structure; in order to enable the front barrel and the rear barrel to move together when realizing half-group focusing, three countersunk holes are designed at the outer periphery of the rear of the front barrel, and three threaded holes are designed at the outer periphery of the front of the rear barrel. The front of the rear barrel is inserted into the rear of the front barrel, the threaded holes are aligned with the countersunk holes, and three countersunk screws 25 are passed through the countersunk holes and locked on the rear barrel, thereby forming a linkage.

[0032] The lens base is mainly used for loading the third gluing group 44 and the rear pressure ring 17. The outer periphery of the rear pressure ring 17 is designed with an external thread that cooperates with the inner rear of the lens base and abuts against the right side of the third gluing group 44, thereby effectively ensuring the coaxiality of the third gluing group 44 and the stability of the structure; at the same time, in order to achieve half-group focusing, the third gluing group 44 is fixed, the inner periphery of the front part of the lens base is sleeved on the outer periphery of the rear part of the sleeve, and the lens base is locked and fixed to the sleeve by three countersunk screws 14, thereby ensuring that the third gluing group 44 is fixed and half-group focusing is achieved; further, in order to meet the use of most industrial cameras, the rear interface of the lens base is designed as the mainstream C-Mount, further enhancing market competitiveness.

[0033] In this embodiment, the focusing mechanism includes a focusing cam, an adjustment ring and a positioning pin; a "symmetrical inclined groove + positioning pin sliding" design scheme is adopted; at the same time, in order to ensure that the front and rear lens groups do not move in a circular motion, a "symmetrical limit slider" design scheme is adopted on both sides of the front periphery of the main sleeve; the specific implementation plan is as follows: two symmetrical inclined grooves are adopted on the periphery of the focusing cam 3, and the spiral direction of the symmetrical inclined grooves is designed to move clockwise; in order to ensure that the front and rear lens groups do not move in a circular motion, two symmetrical limit sliders are designed on both sides of the front periphery of the main sleeve. The two straight grooves are matched with the oblique grooves, and then locked and fixed with the two threaded holes on the outer periphery of the front part of the front lens barrel by two locating pins 6, and limited to form a limit in the symmetrical oblique grooves and straight grooves; further, in order to make the focusing smoother and the hand feel lighter, a focusing ring 5 is also designed on the outer periphery of the focusing cam, and is locked and fixed on the focusing cam by three screws A; finally, the focusing ring 5 is manually rotated to drive the focusing cam 3 to rotate circumferentially, so that the locating pins slide in the symmetrical oblique grooves and straight grooves, thereby driving the front and rear lens barrels to perform front and rear linear focusing.

[0034] The diaphragm C is a manual diaphragm. To ensure the stability of the manual diaphragm, the manual diaphragm is integrated into the lens. The integrated diaphragm C is fixed to the three threaded holes on the inner side of the rear of the front lens barrel by three screws B to form an integral body with the front lens barrel. To further limit the rotation angle of the diaphragm C beyond the use stroke, an diaphragm limit groove is designed on the outer periphery of the rear of the sleeve. To further enable the diaphragm to meet the adjustment requirements of different environments, an diaphragm ring 29 is designed, and a threaded hole that matches the diaphragm pin 10 is designed on the outer periphery of the diaphragm ring 29. The specific implementation is as follows: the diaphragm ring 29 is sleeved on the outer periphery of the rear of the main sleeve, and the threaded hole is aligned with the diaphragm limit groove, and the diaphragm pin is fixed by locking with the threaded hole on the diaphragm ring. The diaphragm pin passes through the diaphragm limit groove set on the side of the main sleeve and is connected to the diaphragm crank handle 13 to form an integral linkage. Finally, the diaphragm crank handle is driven to rotate in a circle by manually rotating the diaphragm ring.

[0035] In order to further increase the usability of the lens, locking screws are provided on the focus ring and the aperture ring, namely the focus fixing screw 23 and the aperture fixing screw 27, to ensure their final fixation; in order to further improve the consistency of the lens appearance, the overall appearance adopts a consistent milling and oxidation process to ensure the overall aesthetics of the lens; in order to further meet the use of most industrial cameras, the lens interface is designed as the mainstream C-Mount, which improves market competitiveness.

[0036] A focusing method for a large-target-area, high-definition, low-distortion industrial lens as described above adopts a half-group focusing method, and controls the front and rear lens barrels to move forward and backward in a straight line through a focusing mechanism to achieve focusing; the specific operation is to manually rotate the focusing ring to drive the focusing cam to rotate circumferentially, so that the positioning pin slides in the symmetrical oblique groove and straight groove, thereby driving the front and rear lens barrels to move forward and backward in a straight line to achieve focusing.

[0037] Unless otherwise stated, any technical solution disclosed in the present invention disclosed above, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any technician in the field should understand that the preferred numerical range is only a numerical value with a more obvious technical effect or representative value among many implementable numerical values. Since there are too many numerical values ​​to be exhaustive, the present invention discloses some numerical values ​​to illustrate the technical solution of the present invention, and the numerical values ​​listed above should not constitute a limitation on the scope of protection of the present invention.

[0038] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by integrated molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0039] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0040] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A large-surface, high-definition, low-distortion industrial lens, characterized by: The optical system of the lens is composed of a front lens group A, a stop C, and a rear lens group B arranged in sequence from front to back along the incident light path; the front lens group A is composed of a first cemented group of a positive meniscus lens A-1, a positive meniscus lens A-2, a biconvex lens A-3, and a biconcave lens A-4 arranged in sequence from front to back in close contact; the rear lens group B is composed of a second cemented group of a negative meniscus lens B-1 and a positive meniscus lens B-2 arranged in sequence from front to back in close contact, and a third cemented group of a biconvex lens B-3, a positive meniscus lens B-4, and a negative meniscus lens B-5 arranged in sequence from front to back in close contact; the front lens group The air gap between lens A and the rear lens group B is 7.562mm, and the air gap between the front lens group A and the aperture C is 2.593mm; the air gap between the positive meniscus lens A-1 and the positive meniscus lens A-2 in the front lens group A is 3.445mm, and the air gap between the positive meniscus lens A-2 and the first cemented group is 0.1mm; the air gap between the second cemented group and the biconvex lens B-3 in the rear lens group B is 3.587mm, and the air gap between the biconvex lens B-3 and the third cemented group is 8.385-8.795mm.

2. The large-surface, high-definition, low-distortion industrial lens according to claim 1, characterized in that: The mechanical structure of the lens includes a main sleeve, in which an inner hole of the main sleeve is installed a front lens group barrel that can move axially relative to the main sleeve, a front lens group A is installed at the front of the inner hole of the front lens group barrel, a rear lens group barrel is fixedly installed at the rear of the inner hole of the front lens group barrel, a second bonding group of the rear lens group B and a double convex lens B-3 are installed in the inner hole of the rear lens group barrel; the rear end of the main sleeve is fixedly connected to a lens base, a third bonding group of the rear lens group B is installed in the inner hole of the lens base, and a focusing mechanism for controlling the forward and backward movement of the front lens group barrel and the rear lens group barrel is installed on the main sleeve.

3. A focusing method for a large-target-area, high-definition, low-distortion industrial lens as claimed in claim 2, characterized in that: It adopts a half-group focusing method, and the front and rear lens barrels are controlled by the focusing mechanism to move forward and backward in a straight line to achieve focusing.

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