CN108802971B - Low-distortion machine vision optical system - Google Patents
Low-distortion machine vision optical system Download PDFInfo
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- CN108802971B CN108802971B CN201810593634.0A CN201810593634A CN108802971B CN 108802971 B CN108802971 B CN 108802971B CN 201810593634 A CN201810593634 A CN 201810593634A CN 108802971 B CN108802971 B CN 108802971B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
- G02B13/0055—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element
- G02B13/006—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras employing a special optical element at least one element being a compound optical element, e.g. cemented elements
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Abstract
The invention relates to a low-distortion machine vision optical system, wherein a front group A, a diaphragm C, a rear group B and plate glass are sequentially arranged in an optical system of a lens along the incident direction of light rays from left to right, the front group A comprises a biconvex positive lens A1, a biconvex positive lens A2, a biconcave negative lens A3 and a plano-concave negative lens A4 which are sequentially arranged, and the rear group B comprises a biconcave negative lens B1, a biconvex positive lens B2 and a biconvex positive lens B3 which are sequentially arranged.
Description
Technical Field
The invention relates to a low-distortion machine vision optical system.
Background
A plurality of machine vision lenses are applied to the field of industrial detection in the existing market, but the detection effect of a plurality of industrial lenses is still kept on low pixel and low depth of field, and the detection effect is not ideal enough. The lens has the problems of large edge distortion, small range of detected object distance, large structural size, heavy volume and the like.
Disclosure of Invention
The invention aims to overcome the defects and provides a low-distortion machine vision optical system with a simple structure.
The technical scheme includes that a front group A, a diaphragm C, a rear group B and flat glass are sequentially arranged in an optical system of the lens along the incident direction of light rays from left to right, the front group A comprises a biconvex positive lens A1, a biconvex positive lens A2, a biconcave negative lens A3 and a plano-concave negative lens A4 which are sequentially arranged, and the rear group B comprises a biconcave negative lens B1, a biconvex positive lens B2 and a biconvex positive lens B3 which are sequentially arranged.
Further, the double convex positive lens a2 and the double concave negative lens A3 form a front group adhesive assembly, and the double concave negative lens B1 and the double convex positive lens B2 form a rear group adhesive assembly.
Further, the focal power of the front group A is negative, and the focal power of the rear group B is positive.
Further, the right convex surface of the biconvex positive lens a1 is bent to the diaphragm side; the right convex surface of the biconvex positive lens A2 is bent to the diaphragm side; the left concave surface of the biconcave negative lens A3 bends to the diaphragm side; the bonding surface of the front combined bonding member formed by the double convex positive lens A2 and the double concave negative lens A3 faces back to the diaphragm side; the right concave surface of the double concave negative lens B1 is bent to the diaphragm side; the left convex surface of the biconvex positive lens B2 curves to the diaphragm side; the cemented surface of the rear combined cemented piece consisting of the double-concave negative lens B1 and the double-convex positive lens B2 faces away from the diaphragm side; the left convex surface of the biconvex positive lens B3 is curved to the diaphragm side.
Further, the biconvex positive lens A1 is made of crown glass; the biconvex positive lens A2 is made of crown glass; the biconcave negative lens A3 is made of flint glass; the plano-concave negative lens A4 is made of crown glass; the biconvex positive lens B2 is made of crown glass; the biconvex positive lens B3 is made of crown glass.
Further, the air gap between the double convex positive lens a1 and the double convex positive lens a2 is 2.5mm, the air gap between the double concave negative lens A3 and the plano-concave negative lens a4 is 3.6mm, the air gap between the plano-concave negative lens a4 and the diaphragm C is 1.2mm, the air gap between the diaphragm C and the double concave negative lens B1 is 5.5mm, and the air gap between the double convex positive lens B2 and the double convex positive lens B3 is 0.1 mm; the air gap between the front group a and the rear group B was 6.7 mm.
Compared with the prior art, the invention has the following beneficial effects: the optical system is simple in structure, low distortion and high resolution can be guaranteed at the same time under a certain shooting distance, the industrial detection requirement is met, the distortion degree of images can be effectively reduced, and the detection precision is effectively improved.
Drawings
The invention is further described with reference to the following figures.
FIG. 1 is a diagram of an optical system according to an embodiment of the present invention.
FIG. 2 is a graph of MTF at an object distance of 0.5 meters.
FIG. 3 is a plot of modulation transfer function over a field of view;
FIG. 4 is a graph of the illuminance of an optical system;
FIG. 5 is a distortion diagram of an optical system;
in the figure:
a-front group A, C diaphragm C, B-rear group B, A1 biconvex positive lens A1, A2 biconvex positive lens A2, A3 biconcave negative lens A3, A4 plano-concave negative lens A4, B1 biconcave negative lens B1, B2 biconvex positive lens B2, B3 biconvex positive lens B3, and 1-plate glass.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
As shown in fig. 1 to 5, a low distortion machine vision optical system, a front group a, a diaphragm C, a rear group B and a flat glass 1 are sequentially arranged in an optical system of a lens along a light ray incidence direction from left to right, the front group a includes a biconvex positive lens a1, a biconvex positive lens a2, a biconcave negative lens A3 and a plano-concave negative lens a4, and the rear group B includes a biconcave negative lens B1, a biconvex positive lens B2 and a biconvex positive lens B3 which are sequentially arranged; the front group A consists of four spherical lenses, and the rear group B consists of three spherical lenses.
In the present embodiment, the double convex positive lens a2 and the double concave negative lens A3 form a front group cemented element, and the double concave negative lens B1 and the double convex positive lens B2 form a rear group cemented element.
In this embodiment, the power of the front group a is negative and the power of the rear group B is positive.
In the present embodiment, the right convex surface of the biconvex positive lens a1 is curved to the diaphragm side; the right convex surface of the biconvex positive lens A2 is bent to the diaphragm side; the left concave surface of the biconcave negative lens A3 bends to the diaphragm side; the bonding surface of the front combined bonding member formed by the double convex positive lens A2 and the double concave negative lens A3 faces back to the diaphragm side; the right concave surface of the double concave negative lens B1 is bent to the diaphragm side; the left convex surface of the biconvex positive lens B2 curves to the diaphragm side; the cemented surface of the rear combined cemented piece consisting of the double-concave negative lens B1 and the double-convex positive lens B2 faces away from the diaphragm side; the left convex surface of the biconvex positive lens B3 is curved to the diaphragm side.
In this embodiment, the biconvex positive lens a1 is made of crown glass, which can reduce spherical aberration and correct chromatic aberration; the biconvex positive lens A2 is made of crown glass, so that the chromatic aberration of the lens can be effectively reduced; the biconcave negative lens A3 is made of flint glass; the front group of the gluing component formed by the double convex positive lens A2 and the double concave negative lens A3 can effectively reduce spherical aberration and chromatic aberration; the plano-concave negative lens A4 is made of crown glass; the biconvex positive lens B2 is made of crown glass; the biconvex positive lens B3 is made of crown glass; the cemented surface of the double concave negative lens B1 and the double convex positive lens B2 is bent to the diaphragm C, partial off-axis aberration can be improved by reducing the refractive index of the material of the double concave negative lens B1, good chromatic aberration correction can be realized by improving the Abbe number of the positive veneer sheet, and other aberrations are introduced less, the angle of light incidence to the lens can be reduced by reasonable refractive index distribution, the sensitivity is effectively reduced, and zero temperature drift is realized by optical power balance.
In the present embodiment, the air gap between the biconvex positive lens a1 and the biconvex positive lens a2 is 2.5mm, the air gap between the biconcave negative lens A3 and the planoconcave negative lens a4 is 3.6mm, the air gap between the planoconcave negative lens a4 and the diaphragm C is 1.2mm, the air gap between the diaphragm C and the biconcave negative lens B1 is 5.5mm, and the air gap between the biconvex positive lens B2 and the biconvex positive lens B3 is 0.1 mm; the air gap between the front group a and the rear group B was 6.7 mm.
In this embodiment, the machine vision optical system focal length f =50 mm; the resolution reaches 600 ten thousand when the corresponding chip size is 2/3' and the distortion is less than 0.08%; the F number corresponding to the diaphragm C is 2.8 to 32; the total length of the optical system is less than 40 mm.
In the present embodiment, the machine vision optical system has the following features:
1. assuming the system focal length is f, the focal length of A1 is f1, and so on to f7, wherein:
0.8<|f1/f|<0.9；0.6<|f2/f|<0.65；0.6<|f3/f|<0.7；0.5<|f4/f|<0.65；1.2<|f5/f|<1.3；0.7<|f6/f|<0.85；0.95<|f7/f|<1.2；
2. let A1 have refractive index n1 and Abbe number v1, and so on to n7 and v7, wherein:
1.65<n1<1.75；45<v1<58；1.55<n2<1.65；51<v2<60；1.65<n3<1.80；22<v3<35；1.60<n4<1.70；45<v4<60；1.68<n5<1.85；21<v5<30；1.52<n6<1.67；39<v6<51；1.56<n7<1.75；36<v7<50；
according to the performance indexes, the optical distortion of the system is less than or equal to 0.08%, the distortion of the scheme is low, the distortion degree of the image can be effectively reduced, and the detection precision is effectively improved.
In this example, the parameters for each lens are shown in the following table:
in this embodiment, it can be seen from fig. 2 that the modulation transfer function value of the machine vision optical system at 150 line pairs is kept at 0.5, and the transfer function difference of each field is small.
In this embodiment, fig. 3 shows a transfer function diagram under a full field of view, and the curves from the top up correspond to 50 to 300 line pairs in sequence with 50 lines as intervals, and fig. 2 and 3 show that the optical system has small field curvature and small astigmatism, so that the imaging difference between the edge and the center is small, and a good imaging effect is achieved.
In the present embodiment, fig. 4 is an illuminance map of the machine vision optical system, and it is understood from the map that the illuminance of the lens is 75% or more, and the brightness and uniformity of the detection screen are ensured.
In the present embodiment, fig. 5 is a distortion diagram of the system, and it can be seen from the diagram that the maximum distortion is about 0.07%, and the low distortion ensures that the distortion degree of the imaging at the maximum field of view is small, and ensures its excellent detection performance.
In this embodiment, the front and rear groups form a double-gauss complicated lens; the front group A adopts a combination of four negative focal powers, and the rear group B adopts a combination of three positive focal powers, wherein the combination is mainly used for balancing the focal power and correcting the vertical axis aberration; the optical system adopts a whole group focusing mode, adjusts imaging by changing the distance from the lens B3 to an image surface, can realize good imaging effect in a certain object distance, and has an imaging range of 200 to infinity; wherein, the imaging effect is best when the object distance is 0.3 to 2 meters; the maximum chief ray incident angle of the lens is 5 degrees, so that the balanced chip light receiving area can be ensured, uniform illumination conditions are provided for a detected picture, and the problems of color cast and the like can be effectively solved; the total length of the machine vision optical system is less than or equal to 40mm, and the machine vision optical system has the advantage of small volume, so that the machine vision optical system is more widely applied; the front group of lenses has smaller aperture and reduces the radial length of the structural member, so that the lens is easier to process and assemble, and the lens is more exquisite.
The above-mentioned preferred embodiments, further illustrating the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned are only preferred embodiments of the present invention and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A low distortion machine vision optical system, characterized by: a front group A, a diaphragm C, a rear group B and flat glass are sequentially arranged in an optical system of the lens along the incident direction of light rays from left to right, the front group A comprises a biconvex positive lens A1, a biconvex positive lens A2, a biconcave negative lens A3 and a plano-concave negative lens A4 which are sequentially arranged, and the rear group B comprises a biconcave negative lens B1, a biconvex positive lens B2 and a biconvex positive lens B3 which are sequentially arranged; the air gap between the double-convex positive lens A1 and the double-convex positive lens A2 is 2.5mm, the air gap between the double-concave negative lens A3 and the plano-concave negative lens A4 is 3.6mm, the air gap between the plano-concave negative lens A4 and the diaphragm C is 1.2mm, the air gap between the diaphragm C and the double-concave negative lens B1 is 5.5mm, and the air gap between the double-convex positive lens B2 and the double-convex positive lens B3 is 0.1 mm; the air gap between the front group A and the rear group B is 6.7 mm; the object side curvature radius of the biconvex positive lens A1 is 39.1mm, the image side curvature radius is-165.1 mm, and the glass refractive index is 1.729505; the object-side curvature radius of the biconvex positive lens A2 is 26.5mm, the image-side curvature radius is-332.7 mm, and the glass refractive index is 1.615520; the object-side curvature radius of the double-concave negative lens A3 is-332.7 mm, the image-side curvature radius is 22.6mm, and the glass refractive index is 1.775301; the curvature radius of the image side surface of the plano-concave negative lens A4 is 11.52 mm, and the refractive index of the glass is 1.612553; the object-side curvature radius of the double-concave negative lens B1 is-14.5 mm, the image-side curvature radius is 48.7mm, and the glass refractive index is 1.725252; the object-side curvature radius of the biconvex positive lens B2 is 48.7mm, the image-side curvature radius is-15.2 mm, and the glass refractive index is 1.610468; the object-side curvature radius of the biconvex positive lens B3 was 38.9mm, the image-side curvature radius was-151.3 mm, and the glass refractive index was 1.605450.
2. A low distortion machine vision optical system as set forth in claim 1, wherein: the double-convex positive lens A2 and the double-concave negative lens A3 form a front assembly adhesive assembly, and the double-concave negative lens B1 and the double-convex positive lens B2 form a rear assembly adhesive assembly.
3. A low distortion machine vision optical system as set forth in claim 1, wherein: the focal power of the front group A is negative, and the focal power of the rear group B is positive.
4. A low distortion machine vision optical system as set forth in claim 1, wherein: the right convex surface of the biconvex positive lens A1 is bent to the diaphragm side; the right convex surface of the biconvex positive lens A2 is bent to the diaphragm side; the left concave surface of the biconcave negative lens A3 bends to the diaphragm side; the bonding surface of the front combined bonding member formed by the double convex positive lens A2 and the double concave negative lens A3 faces back to the diaphragm side; the right concave surface of the double concave negative lens B1 is bent to the diaphragm side; the left convex surface of the biconvex positive lens B2 curves to the diaphragm side; the cemented surface of the rear combined cemented piece consisting of the double-concave negative lens B1 and the double-convex positive lens B2 faces away from the diaphragm side; the left convex surface of the biconvex positive lens B3 is curved to the diaphragm side.
5. A low distortion machine vision optical system as set forth in claim 1, wherein: the biconvex positive lens A1 is made of crown glass; the biconvex positive lens A2 is made of crown glass; the biconcave negative lens A3 is made of flint glass; the plano-concave negative lens A4 is made of crown glass; the biconvex positive lens B2 is made of crown glass; the biconvex positive lens B3 is made of crown glass.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1661417A (en) * | 2004-02-24 | 2005-08-31 | 三星电子株式会社 | Retrofocus type projection optical system |
| CN103823289A (en) * | 2012-11-19 | 2014-05-28 | 上海三鑫科技发展有限公司 | Miniature projection lens |
| CN106154517A (en) * | 2015-04-08 | 2016-11-23 | 广州长步道光电科技有限公司 | Doubly telecentric tight shot |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1661417A (en) * | 2004-02-24 | 2005-08-31 | 三星电子株式会社 | Retrofocus type projection optical system |
| CN103823289A (en) * | 2012-11-19 | 2014-05-28 | 上海三鑫科技发展有限公司 | Miniature projection lens |
| CN106154517A (en) * | 2015-04-08 | 2016-11-23 | 广州长步道光电科技有限公司 | Doubly telecentric tight shot |
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