CN111596443B - Machine vision ultraviolet lens with long rear working distance - Google Patents
Machine vision ultraviolet lens with long rear working distance Download PDFInfo
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- CN111596443B CN111596443B CN202010623498.2A CN202010623498A CN111596443B CN 111596443 B CN111596443 B CN 111596443B CN 202010623498 A CN202010623498 A CN 202010623498A CN 111596443 B CN111596443 B CN 111596443B
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- 239000000463 material Substances 0.000 claims abstract description 12
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 8
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims abstract description 8
- 229910001634 calcium fluoride Inorganic materials 0.000 claims abstract description 8
- 239000005350 fused silica glass Substances 0.000 claims abstract description 8
- 230000003287 optical effect Effects 0.000 claims description 21
- 230000005499 meniscus Effects 0.000 claims description 6
- 238000003384 imaging method Methods 0.000 abstract description 8
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000004075 alteration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000013307 optical fiber Substances 0.000 description 2
- 239000005304 optical glass Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000005286 illumination Methods 0.000 description 1
- 239000000976 ink Substances 0.000 description 1
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000012634 optical imaging Methods 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
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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
- G02B13/005—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having spherical lenses only
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/14—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation
- G02B13/143—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation for use with ultraviolet radiation
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/14—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation
- G02B13/146—Optical objectives specially designed for the purposes specified below for use with infrared or ultraviolet radiation with corrections for use in multiple wavelength bands, such as infrared and visible light, e.g. FLIR systems
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Lenses (AREA)
Abstract
The invention relates to a machine vision ultraviolet lens with a long back working distance, which comprises a front lens group with negative focal power, a diaphragm and a back lens group with positive focal power, which are sequentially arranged along the incident direction of light; the front lens group is a first lens with negative diopter, and the rear lens group is sequentially provided with a second lens with positive diopter, a third lens with negative diopter, a fourth lens with positive diopter and a fifth lens with negative diopter from an object space to an image space; the negative diopter lens is made of fused quartz material, and the positive diopter lens is made of calcium fluoride material. The invention adopts 5 spherical lenses to carry out ultraviolet imaging and has the characteristics of small F number, compact structure, low distortion, long back working distance and the like.
Description
Technical Field
The invention relates to the technical field of ultraviolet optical imaging, in particular to a machine vision ultraviolet lens with a long back working distance.
Background
Detection is one of the most important applications in the field of machine vision industry, and image acquisition is an important component of a machine vision system, wherein the quality of an acquired image is affected by selection of a light source, selection of an optical lens and selection of a camera (CCD or CMOS).
The imaging quality of the optical lens directly influences the detection and judgment results of the system, the existing machine vision lens mainly focuses on visible light and infrared bands, and products in the ultraviolet band are fewer. Because ultraviolet light has a shorter wavelength and can be scattered by surface features of products, features which cannot be detected by visible light can be detected, such as detection of products such as plastics, paints, printing inks, dyes and the like. However, due to the limited materials available in the ultraviolet band, the chromatic aberration of the ultraviolet lens is difficult to correct, and the imaging quality is not easy to improve. Patent CN 104808315B shows a high image quality, low distortion machine vision ultraviolet lens, but it adopts 8 lenses, the number of lenses is large and the maximum rear working distance is only 15mm, which limits the selectable camera interface.
In the model selection of the camera, parameters such as exposure time, frame frequency, camera interface and the like are all factors to be considered, the camera interfaces commonly used for the industrial camera comprise a C interface, a CS interface, an F interface and the like, and the rear intercept of flanges corresponding to different interfaces is different. The rear working distance of the lens is increased, and when the lens is used specifically, only the adapter is needed to convert cameras with different interfaces, so that the application range of the lens is greatly enlarged.
Disclosure of Invention
The invention aims to solve the technical problem of providing a machine vision ultraviolet lens with a long rear working distance, wherein the lens can be compatible with cameras with different interfaces, and the cameras with different interfaces are converted only by an adapter, so that the application range of the optical lens is expanded.
In order to solve the technical problem, the machine vision ultraviolet lens with the long back working distance comprises a front lens group with negative focal power, a diaphragm and a back lens group with positive focal power, which are sequentially arranged along the incident direction of light; the front lens group is a first lens with negative diopter, and the rear lens group is sequentially provided with a second lens with positive diopter, a third lens with negative diopter, a fourth lens with positive diopter and a fifth lens with negative diopter from an object space to an image space; the negative diopter lens is made of fused quartz material, and the positive diopter lens is made of calcium fluoride material.
The first lens is a meniscus negative lens with a concave surface facing an image surface, the second lens is a biconvex positive lens, the third lens is a biconcave lens, the fourth lens is a biconvex positive lens, and the fifth lens is a meniscus negative lens with a concave surface facing an object surface.
The air interval between the first lens and the diaphragm is 12-14 mm, the air interval between the diaphragm and the second lens is 1-3 mm, the air interval between the second lens and the third lens is 2-4 mm, the air interval between the third lens and the fourth lens is 2-4 mm, the air interval between the fourth lens and the fifth lens is 2-4 mm, and the air interval between the fifth lens and the image plane is 57-60 mm.
The focal length of the first lens is between-170 mm and-180 mm, the focal length of the second lens is between 30mm and 40mm, the focal length of the third lens is between-20 mm and-30 mm, the focal length of the fourth lens is between 20mm and 30mm, and the focal length of the fifth lens is between-65 mm and-75 mm.
The effective focal length of the ultraviolet lens is 75mm, the relative numerical aperture is F/3.8, 1.2' CMOS is used for receiving, the pixel size is 6.5 mu m, the maximum aperture is smaller than 25mm, and the total optical length is 46.9mm from the first lens to the fifth lens.
The full field of view of the ultraviolet lens is 14 degrees, and the working wave band is 230-1100 nm.
Further, parameters of each lens, stop and image plane are shown in the following table, wherein R1～R10The radius of curvature, t, of each optical surface from the object plane to the image plane1～t5The thickness of each lens from the object plane to the image plane, d1～d5Sequentially the distance from the object plane to the back surface of each optical element on the image plane to the front surface of the next optical element;
the invention has the advantages of
The machine vision ultraviolet lens has the advantages that the machine vision ultraviolet lens with low distortion and long back working distance is provided, the lens adopts 5 spherical lenses, the value of a full-wave-band modulation transfer function is larger than 0.3 at the maximum view field when the Nyquist frequency is 50lp/mm, except the maximum view field, the value of the full-wave-band modulation transfer function is larger than 0.3 under the condition that the Nyquist frequency is 77lp/mm, the image plane illumination is larger than 90%, the imaging distortion is smaller than 0.1%, the back working distance is larger than 56mm, and the machine vision ultraviolet lens is suitable for cameras with different interfaces. The optical fiber has the characteristics of small F number, compact structure, low distortion, long back working distance and the like, the working wavelength band is 230-1100nm, and ultraviolet imaging can be carried out after the optical fiber is focused by visible light.
Drawings
FIG. 1 is a schematic view of an optical structure of an ultraviolet lens;
FIG. 2 is a dot-column diagram of each field of view of the ultraviolet lens at the wavelength of 240-320 nm;
FIG. 3 is a MTF transfer function curve of the ultraviolet lens at each image plane of fields of 240-320 nm;
FIG. 4 is a graph of field curvature and distortion of an optical lens;
fig. 5 is a relative illuminance diagram of an image plane.
Detailed Description
The long-back working distance machine vision ultraviolet lens of the invention is mainly composed of a front lens group with negative focal power, a back lens group with positive focal power, a diaphragm 6 positioned between the front lens group and the back lens group and an image surface 7, as shown in figure 1. The front lens group is positioned on the front side of the diaphragm 6 and only comprises a first lens 1 with negative diopter, the rear lens group is positioned on the rear side of the diaphragm 6, and a second lens 2 with positive diopter, a third lens 3 with negative diopter, a fourth lens 4 with positive diopter and a fifth lens 5 with negative diopter are sequentially arranged from the object side to the image side.
The first lens 1 is a meniscus lens with a concave surface facing an image surface, the second lens 2 is a biconvex lens, the third lens 3 is a biconcave lens, the fourth lens 4 is a biconvex lens, and the fifth lens 5 is a meniscus lens with a concave surface facing an object surface.
The air interval between the first lens 1 and the diaphragm 6 is 12-14 mm, the air interval between the diaphragm 6 and the second lens 2 is 1-3 mm, the air interval between the second lens 2 and the third lens 3 is 2-4 mm, the air interval between the third lens 3 and the fourth lens 4 is 2-4 mm, the air interval between the fourth lens 4 and the fifth lens 5 is 2-4 mm, and the air interval between the fifth lens 5 and the image plane 7 is 57-60 mm.
Specifically, in the present embodiment, the air interval between the first lens 1 and the diaphragm 6 is 13.645mm, the air interval between the diaphragm 6 and the second lens 2 is 1.99mm, the air interval between the second lens 2 and the third lens 3 is 3.152mm, the air interval between the third lens 3 and the fourth lens 4 is 2.948mm, the air interval between the fourth lens 4 and the fifth lens 5 is 2.5mm, and the air interval between the fifth lens 5 and the image plane 7 is 58.356 mm.
The focal length of the first lens is between 170mm and 180mm, the focal length of the second lens is between 30mm and 40mm, the focal length of the third lens is between 20mm and 30mm, the focal length of the fourth lens is between 20mm and 30mm, and the focal length of the fifth lens is between 65mm and 75 mm.
As the transmission wavelength of the common optical glass is generally between 350 and 2400nm, the common optical glass can not completely transmit in a deep ultraviolet band, and only three types of calcium fluoride, magnesium fluoride and fused quartz are suitable for optical materials in the ultraviolet band. This example finally selects two materials, fused silica and calcium fluoride. Since calcium fluoride is deliquescent in air, the material selection of the first and last lens of an optical lens should be avoided.
In this embodiment, the effective focal length of the ultraviolet lens is 75mm, the relative numerical aperture is F/3.8, 1.2 ″ CMOS reception is used, the pixel size is 6.5 μm, the maximum aperture is less than 25mm, and the total optical length is 46.9mm from the first lens to the fifth lens. The full field of view of the ultraviolet lens is 14 degrees, and the working wave band is 230-700 nm. The parameters of the lens in this embodiment, such as the radius of curvature, the thickness, and the lens material, are shown in table 1 below.
The parameters of each lens, aperture and image plane of the present invention are shown in Table 1, wherein R1～R10The radius of curvature, t, of each optical surface from the object plane to the image plane1～t5The thickness of each lens from the object plane to the image plane, d1～d5The distance from the object plane to the image plane from the back surface of each optical element to the front surface of the next optical element is sequentially calculated.
TABLE 1 UV optical system lens parameter data
| Optical surface | Radius of curvature | Thickness, distance | Material |
| 1 | R1＝31.735 | t1＝2.5 | Fused quartz |
| 2 | R2＝22.685 | d1＝13.645 | |
| Diaphragm | Plane surface | d2＝1.99 | |
| 4 | R3＝17.386 | t2＝6.784 | Calcium fluoride |
| 5 | R4＝-155.26 | d3＝3.152 | |
| 6 | R5＝-37.43 | t3＝3.569 | Fused quartz |
| 7 | R6＝19.008 | d4＝2.948 | |
| 8 | R7＝29.267 | t4＝7.31 | Calcium fluoride |
| 9 | R8＝-18.814 | d5＝2.5 | |
| 10 | R9＝-15.073 | t5＝2.5 | Fused quartz |
| 11 | R10＝-29.424 | d6＝58.356 | |
| Image plane | Plane surface | - |
FIG. 2 is a point diagram of 240-320nm bands in each field of view in the embodiment of the present invention, where the root mean square radius at the maximum field of view is 8.605 μm, and the root mean square radii of other fields of view are all smaller than 6.0 μm, so as to meet the requirement of imaging quality;
FIG. 3 is an MTF transfer function curve of the ultraviolet lens at each image plane of fields of 240-320nm, in which the MTF value of the maximum field in the sagittal direction is slightly lower and is greater than 0.3 at the 50lp/mm line pair; the MTF values of other fields in all directions are larger than 0.3, the curve is smooth and compact, chromatic aberration correction is good, and the system has good imaging quality in the full-band full-field.
Fig. 4 is a graph of field curvature and distortion of the optical lens in this embodiment, and it can be seen from the graph that the field curvature of the ultraviolet lens is smaller than 0.5mm, the distortion is smaller than 0.1%, the distortion of the acquired image is more slight, and the measurement result is more accurate.
Fig. 5 shows the relative illuminance distribution of the 280nm band at the image plane in this embodiment, and the other bands are substantially the same, and it can be seen in the figure that the relative illuminance values at each field are all greater than 90%, which indicates that the lens illuminance is uniform and the imaging effect is good.
The above are preferred embodiments of the present invention, and all changes made according to the technical solutions of the present invention that produce functional effects do not exceed the scope of the technical solutions of the present invention are included in the scope of the present invention.
Claims (2)
1. A machine vision ultraviolet lens with long back working distance is characterized by comprising a front lens group with negative focal power, a diaphragm (6) and a back lens group with positive focal power which are sequentially arranged along the incident direction of light; the front lens group is a first lens (1) with negative diopter, and the rear lens group is composed of a second lens (2) with positive diopter, a third lens (3) with negative diopter, a fourth lens (4) with positive diopter and a fifth lens (5) with negative diopter which are sequentially arranged from an object side to an image side; the negative diopter lens is made of fused quartz material, and the positive diopter lens is made of calcium fluoride material; the first lens (1) is a meniscus negative lens with a concave surface facing an image surface, the second lens (2) is a biconvex positive lens, the third lens (3) is a biconcave lens, the fourth lens (4) is a biconvex positive lens, and the fifth lens (5) is a meniscus negative lens with a concave surface facing an object surface; the air interval between the first lens (1) and the diaphragm (6) is 12-14 mm, the air interval between the diaphragm (6) and the second lens (2) is 1-3 mm, the air interval between the second lens (2) and the third lens (3) is 2-4 mm, the air interval between the third lens (3) and the fourth lens (4) is 2-4 mm, the air interval between the fourth lens (4) and the fifth lens (5) is 2-4 mm, and the air interval between the fifth lens (5) and the image plane (7) is 57-60 mm; the focal length of the first lens (1) is between-170 mm and-180 mm, the focal length of the second lens (2) is between 30mm and 40mm, the focal length of the third lens (3) is between-20 mm and-30 mm, the focal length of the fourth lens (4) is between 20mm and 30mm, and the focal length of the fifth lens (5) is between-65 mm and-75 mm.
2. The long back working distance machine vision uv lens of claim 1, wherein the parameters of each lens, stop and image plane are as shown in the table, wherein R is1～R10The radius of curvature, t, of each optical surface from the object plane to the image plane1～t5The thickness of each lens from the object plane to the image plane, d1～d5Sequentially the distance from the object plane to the back surface of each optical element on the image plane to the front surface of the next optical element;
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| CN202010623498.2A CN111596443B (en) | 2020-07-01 | 2020-07-01 | Machine vision ultraviolet lens with long rear working distance |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013092775A (en) * | 2011-10-26 | 2013-05-16 | Kofukin Seimitsu Kogyo (Shenzhen) Yugenkoshi | Lens system |
| CN107884905A (en) * | 2016-09-30 | 2018-04-06 | 新巨科技股份有限公司 | Broad angle lens group |
| TW201814346A (en) * | 2016-09-29 | 2018-04-16 | 新鉅科技股份有限公司 | Optical lens system with a wide field of view |
| JP2021107893A (en) * | 2019-12-27 | 2021-07-29 | 久保田 洋治 | Wide-angle lens |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109425965B (en) * | 2017-08-21 | 2021-11-05 | 富晋精密工业（晋城）有限公司 | Image capturing lens |
| CN210038305U (en) * | 2019-04-04 | 2020-02-07 | 南京波长光电科技股份有限公司 | 355nm ultraviolet telecentric f-theta lens |
| CN111025536B (en) * | 2019-12-16 | 2021-11-02 | 诚瑞光学(常州)股份有限公司 | Image pickup optical lens |
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- 2020-07-01 CN CN202010623498.2A patent/CN111596443B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013092775A (en) * | 2011-10-26 | 2013-05-16 | Kofukin Seimitsu Kogyo (Shenzhen) Yugenkoshi | Lens system |
| TW201814346A (en) * | 2016-09-29 | 2018-04-16 | 新鉅科技股份有限公司 | Optical lens system with a wide field of view |
| CN107884905A (en) * | 2016-09-30 | 2018-04-06 | 新巨科技股份有限公司 | Broad angle lens group |
| JP2021107893A (en) * | 2019-12-27 | 2021-07-29 | 久保田 洋治 | Wide-angle lens |
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