A high-resolution and high-illumination machine vision system and a manufacturing method thereof

Abstract

The present invention provides a high-resolution and high-illuminance machine vision system and a manufacturing method thereof. In the optical system of the lens, a front lens group A, a stop, a rear lens group B, and a flat protective glass are sequentially arranged along the incident direction of light from left to right. The front lens group A includes a crescent lens A1 with positive focal power, a crescent lens A2 with positive focal power, and a crescent lens A3 with negative focal power, which are sequentially arranged. The rear lens group B includes a biconcave lens B1 with negative focal power, a crescent lens B2 with positive focal power, a biconvex lens B3 with positive focal power, and a crescent lens B4 with positive focal power. The front lens group A of the optical system has negative focal power, and the rear lens group B has positive focal power. The structure is simple, beautiful, high resolution, and extremely high illumination.

Description

Technical Field

[0001] The invention relates to a high-resolution and high-illuminance machine vision system and a manufacturing method thereof. Background Art

[0002] Currently, many high-resolution and high-illuminance inspection lenses have been put into use. However, other such lenses have a series of problems such as large size, heavy weight, low illumination, poor close-range image quality, high cost or low edge MTF, etc., which are difficult to meet current inspection needs, making it difficult to effectively promote such lenses. Summary of the invention

[0003] The present invention improves the above-mentioned problem, that is, the technical problem to be solved by the present invention is that currently there are many detection lenses similar to this invention put into use, but other such lenses are large in size, heavy in weight, have low illumination, and poor image quality at close range.

[0004] The specific implementation scheme of the present invention is: a high-resolution and high-illuminance machine vision system, in which the optical system of the lens is provided with a front lens group A, an aperture, a rear lens group B, and a flat protective glass in sequence along the incident direction of light from left to right, the front lens group A includes a crescent lens A1 with positive optical focal length, a crescent lens A2 with positive optical focal length, and a crescent lens A3 with negative optical focal length, which are arranged in sequence; the rear lens group B includes a biconcave lens B1 with negative optical focal length, a crescent lens B2 with positive optical focal length, a biconvex lens B3 with positive optical focal length, and a crescent lens B4 with positive optical focal length, the front lens group A of the optical system has a negative optical focal length, and the rear lens group B has a positive optical focal length.

[0005] Furthermore, the air distance from the front group of crescent lens A1 to the crescent lens A2 is 0.1mm, the air distance from the crescent lens A3 to the aperture is 1.467mm, the air distance from the aperture to the biconcave lens B1 is 5.231mm, the air distance from the biconcave lens B1 to the crescent lens B2 is 0.584mm, the air distance from the crescent lens B2 to the biconvex lens B3 is 0.1mm, and the air distance from the crescent lens B4 to the flat protective glass is 10mm.

[0006] Furthermore, the material of the crescent lens A2 with positive optical power is lanthanum crown glass, and the material of the crescent lens A3 with negative optical power is lanthanum flint glass, and they are combined into a glued sheet by optical glue.

[0007] Furthermore, the air distance between the biconvex lens B3 and the crescent lens B4 varies between 1.831 mm and 12.088 mm.

[0008] Furthermore, the aperture value corresponding to the diaphragm is 2.8 to 16; the focal length is 25mm, and the optical distortion is ≤-0.5%.

[0009] Furthermore, when the object distance is infinite, the total optical length of the lens TTL ≤ 34 mm, the optical back focus ≥ 10 mm, and the illumination > 98%.

[0010] Furthermore, a curvature radius R6 of the object side surface of the biconvex lens B3 and a curvature radius R7 of the image side surface of the meniscus lens B4 satisfy 1.2<(R6+R7) / (R6-R7)<1.8.

[0011] Furthermore, assuming that the focal length of the optical system is f, the focal lengths of the crescent lens A1, the crescent lens A2, the crescent lens A3, the biconcave lens B1, the crescent lens B2, the biconvex lens B3 and the crescent lens B4 are f1, f1, f2, f3, f4, f5, f6 and f7, respectively, where:

[0012] 0.7<|f1 / f|<1.5; 0.5<|f2 / f|<1.3;

[0013] 0.1<|f3 / f|<0.6; 0.3<|f4 / f|<1.0;

[0014] 1.0<|f5 / f|<1.7; 0.3<|f6 / f|<1.0;

[0015] 2.2<|f7 / f|<3.3;

[0016] Assume that the focal lengths of the crescent lens A1, crescent lens A2, crescent lens A3, biconcave lens B1, crescent lens B2, biconvex lens B3 and crescent lens B4 are n1, n2, n3, n4, n5, n6 and n7 respectively, where:

[0017] 1.70<n1<1.80; 1.72<n2<1.83;

[0018] 1.60<n3<1.75; 1.65<n4<1.75;

[0019] 1.80<n5<1.93; 1.71<n6<1.83;

[0020] 1.36<n7<1.53.

[0021] Compared with the prior art, the present invention has the following beneficial effects: Compared with the prior art, the structure of the present invention retains the excellent characteristics of the double Gauss structure to effectively correct part of the vertical axis aberration brought by the telephoto system and reduce sensitivity, and the double concave lens B1 and the crescent lens B2 of the rear group are separated to enhance the lens' ability to correct spherical aberration and color. In addition, the crescent lens B4 has a significant effect on the correction field area, and the air gap between the three lenses can also be used to compensate for high-order aberrations. Under reasonable replacement of glass, the focus of the lens has no obvious shift under high and low temperature conditions. The system has small distortion, which fully reduces the image distortion and can provide a good detection picture for industrial detection.

[0022] By analyzing the direction of light and making full use of the characteristics of the aperture to change the surface shape, it is possible to adjust the incident and exit angles of light on each surface. By adjusting the refractive index and controlling the vignetting, the optical focal length can be well balanced, thereby improving the illumination and achieving a high degree of uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 2 is an optical structure diagram of an embodiment of the present invention.

[0024] Figure 2 This is the modulation transfer function diagram of the optical system.

[0025] Figure 3 is the illumination diagram of the optical system.

[0026] Figure 4 Field curvature and distortion diagram of the optical system.

[0027] In the figure: C-aperture, D-flat protective glass 1-crescent lens A1, 2-crescent lens A2, 3-crescent lens A3, 4-crescent lens B1, 5-biconvex lens B2, 6-biconvex lens B3, 7-crescent lens B4, D-flat glass. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figures 1 to 4As shown, a high-resolution and high-illuminance machine vision system, in which the optical system of the lens is provided with a front lens group A, an aperture, a rear lens group B, and a flat protective glass in sequence along the incident direction of light from left to right, the front lens group A includes a crescent lens A1 with positive optical focal length, a crescent lens A2 with positive optical focal length, and a crescent lens A3 with negative optical focal length, which are arranged in sequence; the rear lens group B includes a biconcave lens B1 with negative optical focal length, a crescent lens B2 with positive optical focal length, a biconvex lens B3 with positive optical focal length, and a crescent lens B4 with positive optical focal length, the front lens group A of the optical system has a negative optical focal length, and the rear lens group B has a positive optical focal length.

[0030] In this embodiment, the air distance from the front group of crescent lens A1 to the crescent lens A2 is 0.1mm, the air distance from the crescent lens A3 to the aperture is 1.467mm, the air distance from the aperture to the biconcave lens B1 is 5.231mm, the air distance from the biconcave lens B1 to the crescent lens B2 is 0.584mm, the air distance from the crescent lens B2 to the biconvex lens B3 is 0.1mm, and the air distance from the crescent lens B4 to the flat protective glass is 10mm.

[0031] The positive-power crescent lens A2 is made of lanthanum crown glass, and the negative-power crescent lens A3 is made of lanthanum flint glass, which are combined into a glued sheet by optical glue. The crescent lens A2 and the crescent lens A3 form a glued sheet, which can effectively reduce the influence of primary chromatic aberration on imaging quality.

[0032] In this embodiment, the air distance between the biconvex lens B3 and the crescent lens B4 varies between 1.831 mm and 12.088 mm. The aperture value corresponding to the aperture is 2.8 to 16; the focal length is 25 mm, the optical distortion is ≤-0.5%, when the object distance is infinite, the total optical length of the lens TTL is ≤34 mm, the optical back focus is ≥10 mm, and the illumination is >98%.

[0033] Assuming that the focal length of the optical system is f, the focal lengths of the crescent lens A1, crescent lens A2, crescent lens A3, biconcave lens B1, crescent lens B2, biconvex lens B3 and crescent lens B4 are f1, f1, f2, f3, f4, f5, f6, f7, respectively, where:

[0034] 0.7<|f1 / f|<1.5; 0.5<|f2 / f|<1.3;

[0035] 0.1<|f3 / f|<0.6; 0.3<|f4 / f|<1.0;

[0036] 1.0<|f5 / f|<1.7; 0.3<|f6 / f|<1.0;

[0037] 2.2<|f7 / f|<3.3;

[0038] Assume that the focal lengths of the crescent lens A1, crescent lens A2, crescent lens A3, biconcave lens B1, crescent lens B2, biconvex lens B3 and crescent lens B4 are n1, n2, n3, n4, n5, n6 and n7 respectively, where:

[0039] 1.70<n1<1.80; 1.72<n2<1.83;

[0040] 1.60<n3<1.75; 1.65<n4<1.75;

[0041] 1.80<n5<1.93; 1.71<n6<1.83;

[0042] 1.36<n7<1.53.

[0043] The following table shows the parameters of each lens in this embodiment. The following are the curvature radius, thickness, and outer diameter of each lens, all in mm. Each surface is from left to right in the figure, and the bonding surface is regarded as the same surface.

[0044]

[0045] In this embodiment, Figure 1 It can be seen that the optical system is composed of 7 spherical lenses. The optical system of the lens is provided with a front group A, an aperture, a rear group B, and a flat protective glass in sequence along the incident direction of light from left to right. The front group A includes a crescent lens A1 with positive focal length, a crescent lens A2 with positive focal length, and a crescent lens A3 with negative focal length. The rear group B includes a biconcave lens B1 with negative focal length, a crescent lens B2 with positive focal length, a biconvex lens B3 with positive focal length, and a crescent lens B4 with positive focal length. The structure of the present invention is further deformed and optimized on the basis of the classic double Gaussian structure. While retaining the double Gaussian structure to effectively correct part of the vertical axis aberration brought by the telephoto system, the B1 and B2 lenses of the rear group are split, and the lens's ability to correct spherical aberration and color is enhanced. In addition, the B4 lens has a significant effect on correcting the Petzval field curvature. The air gap between the three lenses can also be used to compensate for high-order aberrations. The lens has enhanced its ability to correct Petzval field curvature, spherical aberration and chromatic aberration, and the air gap between the two lenses can also be used to compensate for advanced aberrations. By properly replacing the glass, the lens has no obvious focus shift at high and low temperatures. The system has low distortion, which fully reduces the image distortion and can provide a good inspection picture for industrial inspection.

[0046] The EPD satisfies: f / EPD ≤ 3. For example, 1.0 < f / EPD ≤ 3. Reasonably setting the ratio of the total effective focal length of the optical imaging lens to the entrance pupil diameter of the optical imaging lens is beneficial for the optical system to have a large image plane while having a small F-number and a large aperture, so as to achieve good imaging quality in a dark environment.

[0047] By analyzing the light ray direction, making full use of the characteristics of the aperture to change the surface shape, it is possible to adjust the incident and exit angles formed by the light rays on each surface. Combining with the adjustment of the refractive index and the control of vignetting can well balance the optical power, thereby improving the illuminance and also reducing the sensitivity under the Monte Carlo distribution, so that the optical system can withstand the deviations caused by processing or assembly such as structure and process, and enable it to have the production capacity.

[0048] By analyzing the light ray direction, making full use of the characteristics of the aperture to change the surface shape, it is possible to adjust the incident and exit angles formed by the light rays on each surface. Combining with the adjustment of the refractive index and the control of vignetting can well balance the optical power, thereby improving the illuminance and also reducing the sensitivity under the Monte Carlo distribution, so that the optical system can withstand the deviations caused by processing or assembly such as structure and process, and enable it to have the production capacity.

[0049] In this embodiment, the lens uses all-glass spherical lenses, which ensures the performance of the optical system while ensuring low material cost and easy lens processing. Adopting the method of grouped focusing, by changing the air spacing between the biconvex lens B3 and the biconvex lens B4 to achieve imaging with a wide object distance, excellent imaging quality is guaranteed for object distances from 0.1 m to infinity. The distortion can be controlled within 0.5% in the main working range, and high image quality at the edge can be guaranteed at the outermost field of view (ϕ9). The CRA of the system is less than 7.2°, which can well match the image sensor and ensure good illuminance of the system. The system adapts to various temperatures, and there is no obvious focus shift when used in the environment of -20 to 60 °C, and normal operation can be guaranteed.

[0050] From Figure 2 it can be seen that when the optical system is at 150 lp / mm, its MTF value is concentrated around 0.6, and this lens has excellent ability to resolve images.

[0051] Figure 3 For the illuminance of the optical system, it is not difficult to see that the system illuminance is basically above 98%, and the system has good uniformity.

[0052] From Figure 4 it can be seen that the optical distortion of this optical system is only within -0.5%, so this machine vision optical system will bring a high degree of graphic reduction to industrial inspection, and there is no phenomenon of edge deformation.

[0053] In this embodiment, the lens can ensure the imaging quality at object distances from 0.15mm to infinity, and the imaging performance is best when the object distance is 200-1000mm. From the optical indicators, it can be seen that the total length of this optical system is small, the application range is wider, the front and rear lens groups have small apertures, the size of the structural parts is reduced, and the lens can be made more compact; the optical system fully adopts a combination of relatively low-priced crown glass and flint glass, fully balances the system's optical power, and enables the system to clearly image in high and low temperature environments.

[0054] 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.

[0055] If the words "first", "second" and so on are used in this article to limit components, those skilled in the art should know that the use of "first" and "second" is only for the convenience of description to distinguish the components. Unless otherwise stated, the above words have no special meaning.

[0056] At the same time, if the above-mentioned invention discloses or involves components or structural parts that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connected by 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 one-piece molding using a casting process) (except when it is obviously impossible to use an integrated molding process).

[0057] 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.

[0058] 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.

[0059] 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 high-resolution and high-illumination machine vision manufacturing method, characterized in that: An optical system including a lens, the optical system comprising a front lens group A, an aperture, a rear lens group B, and a flat protective glass arranged in sequence along the incident direction of light from left to right, the front lens group A comprising a crescent lens A1 with positive optical power, a crescent lens A2 with positive optical power, and a crescent lens A3 with negative optical power arranged in sequence; the rear lens group B comprising a biconcave lens B1 with negative optical power, a crescent lens B2 with positive optical power, a biconvex lens B3 with positive optical power, and a crescent lens B4 with positive optical power arranged in sequence; The front lens group A of the optical system has a negative optical power, and the rear lens group B has a positive optical power; The air distance from the front group meniscus lens A1 to the meniscus lens A2 is 0.1mm, the air distance from the meniscus lens A3 to the diaphragm is 1.467mm, the air distance from the diaphragm to the biconcave lens B1 is 5.231mm, the air distance from the biconcave lens B1 to the meniscus lens B2 is 0.584mm, the air distance from the meniscus lens B2 to the biconvex lens B3 is 0.1mm, and the air distance from the meniscus lens B4 to the flat protective glass is 10mm; Assuming that the focal length of the optical system is f, the focal lengths of the crescent lens A1, crescent lens A2, crescent lens A3, biconcave lens B1, crescent lens B2, biconvex lens B3 and crescent lens B4 are f1, f1, f2, f3, f4, f5, f6, f7, respectively, where: 0.7<|f1 / f|<1.5; 0.5<|f2 / f|<1.3; 0.1<|f3 / f|<0.6; 0.3<|f4 / f|<1.0; 1.0<|f5 / f|<1.7; 0.3<|f6 / f|<1.0; 2.2<|f7 / f|<3.3; Assume that the focal lengths of the crescent lens A1, crescent lens A2, crescent lens A3, biconcave lens B1, crescent lens B2, biconvex lens B3 and crescent lens B4 are n1, n2, n3, n4, n5, n6 and n7 respectively, where: 1.70<n1<1.80; 1.72<n2<1.83; 1.60<n3<1.75; 1.65<n4<1.75; 1.80<n5<1.93; 1.71<n6<1.83; 1.36＜n7＜1.53； The material of the crescent lens A2 with positive optical power is lanthanum crown glass, and the material of the crescent lens A3 with negative optical power is lanthanum flint glass, which are combined into a glued sheet by optical glue; The air distance between the biconvex lens B3 and the crescent lens B4 varies between 1.831 mm and 12.088 mm; The aperture value corresponding to the diaphragm is 2.8 to 16; the focal length is 25mm, and the optical distortion is ≤-0.5%.

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