CN112098424A

CN112098424A - High-precision imaging system, method and detection equipment

Info

Publication number: CN112098424A
Application number: CN202011284549.XA
Authority: CN
Inventors: 崔忠伟
Original assignee: Beijing Leader Intelligent Equipment Co ltd
Current assignee: Beijing Leader Intelligent Equipment Co ltd
Priority date: 2020-11-17
Filing date: 2020-11-17
Publication date: 2020-12-18
Anticipated expiration: 2040-11-17
Also published as: CN112098424B

Abstract

The embodiment of the invention discloses a high-precision imaging system, a high-precision imaging method and high-precision detection equipment, wherein the imaging system comprises: the lens, the lens group, the spectroscope and the light-emitting surface; wherein the lens group comprises at least one lens having an equivalent positive power, a focal point and a first lens optical axis; the position difference between the light-emitting surface and the equivalent focal plane of the lens group does not exceed a first preset range; the first lens optical axis is reflected by the beam splitter to form a second lens optical axis; the lens is provided with a lens optical axis, the lens optical axis penetrates through the spectroscope, and the angle deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range; the first preset range is the distance deviation +/-10 mm and/or the angle deviation +/-20 degrees; the second predetermined range is the angular deviation ± 15 degrees. According to the technical scheme, the illumination and imaging lenses are integrally arranged, so that the imaging consistency is effectively improved, and a high-precision and stable workpiece image can be obtained.

Description

High-precision imaging system, method and detection equipment

Technical Field

The invention relates to the technical field of imaging equipment, in particular to a high-precision imaging system, a high-precision imaging method and high-precision detection equipment.

Background

In the field of workpiece detection at present, the defect detection of small workpieces, particularly fine parts, also depends on the visual detection of assembly line workers to a great extent. In order to improve the detection efficiency, the prior art attempts to introduce a machine vision technology based on image recognition, and detects and discovers defects on a workpiece by intelligently recognizing the acquired workpiece image.

However, machine vision technology has long been faced with many challenges, especially, metal surface parts have high light reflection characteristics and have long been difficult to perform stable high quality imaging. Machine vision techniques rely heavily on the quality of the acquired image, which is affected by many factors. The light path design of the light source illumination and imaging optical system (lens) has the greatest influence on the imaging quality, and the image acquisition device is arranged in the second place. At present, in a workpiece detection system, a workpiece is generally irradiated by a common light source such as coaxial light, annular light, semi-annular light, planar light, strip light or dome light, and then an image of the workpiece is transmitted to an image sensor through a common industrial lens.

However, in the process of implementing the related technical solution of the embodiment of the present invention, it is found that the machine vision inspection method in the prior art still has obvious defects: the imaging consistency of the workpiece in the field of view of the lens is poor, the imaging presented by the workpiece when placed in different positions is different, and when the workpiece is located in certain positions within the field of view, slight defects such as scratches cannot be imaged clearly, resulting in very unstable detection of certain surface defects of the workpiece. In a shallow tool mark defect as shown in fig. 1, the geometrical features of the shallow tool mark at the defect are usually not very different from the surface of the workpiece, and under the imaging of ordinary illumination, the fine defect can not be revealed at all.

Therefore, when the prior art is adopted for detection, the workpiece needs to be placed at a specific position in a visual field, and defects on the workpiece and a light source are kept at a special position, so that a certain quality of collected images can be obtained. However, in an automated inspection line, the workpiece usually keeps a moving state, and the inspection requirement is not matched with an actual working scene, so that the prior art cannot obtain an ideal acquired image in a dynamic inspection process (because the inspection position requirement cannot be ensured), and has poor imaging quality, low accuracy and low detectable rate of surface defects of the workpiece.

Disclosure of Invention

Aiming at the technical problems in the prior art, the embodiment of the invention provides a high-precision imaging system, a high-precision imaging method and high-precision imaging detection equipment, so as to solve the problem of poor dynamic detection imaging quality in the prior art.

A first aspect of embodiments of the present invention provides a high-precision imaging system, including: a lens 110, a lens group 120, a spectroscope 130 and a light-emitting surface 141; wherein,

the lens group 120 comprises at least one lens having an equivalent positive power, a focal point, and a first lens optical axis;

the position difference between the light-emitting surface 141 and the equivalent focal plane of the lens group 120 does not exceed a first preset range;

the first lens optical axis is reflected by the beam splitter 130 to form a second lens optical axis;

the lens 110 has a lens optical axis, the lens optical axis passes through the beam splitter 130, and an angle deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range;

the first preset range is a distance deviation of +/-10 mm and/or an angle deviation of +/-20 degrees; the second preset range is an angle deviation of +/-15 degrees.

In some embodiments, the light emitting face 141 is produced by a light source shining on a diffuser plate, or by a planar light emitting device.

In some embodiments, the light emitting face 141 has a single color light emitting area with a boundary shape that is asymmetric with respect to the first lens optical axis; alternatively, the light emitting surface 141 has two or more monochromatic light emitting areas of different colors.

In some embodiments, the light emitting face 141 has three monochromatic light emitting areas distributed Y-shaped and having three colors of red, green and blue, respectively.

In some embodiments, the lens 110 is a telecentric lens or a quasi-telecentric lens.

In some embodiments, the telecentric or quasi-telecentric lens has an adjustable stop.

In some embodiments, the first preset range is a distance deviation ± 5mm and/or an angle deviation ± 15 degrees; the second preset range is an angle deviation of +/-10 degrees.

In some embodiments, the light emitting area of the light emitting face 141 is generally approximately circular, the circle having a radius R, the lens group 120 having an equivalent focal length f, and a characteristic angle of illumination θ = arctan (R/f), wherein the characteristic angle of illumination θ is not greater than 10 degrees.

In some embodiments, the light emitted from the light emitting surface 141 is refracted and/or reflected to form emergent light, and the image formed by the emergent light irradiated on the metal surface is output by the imaging system through the lens 110.

A second aspect of an embodiment of the present invention provides a high-precision imaging system, including: lens 210, lens group 220, beam splitter 230, stop 240 and illuminant 250; wherein,

the lens group 220 includes at least one lens having an equivalent positive power, a focal point, and a first lens optical axis;

the position difference between the plane where the diaphragm 240 is located and the equivalent focal plane of the lens group 220 does not exceed a first preset range;

the first lens optical axis is reflected by the beam splitter 230 to form a second lens optical axis;

the lens 210 has a lens optical axis, the lens optical axis passes through the beam splitter 230, and an angle deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range;

In some embodiments, the light-transmitting portion of the diaphragm 240 is a light-transmitting hole, and the profile of the light-transmitting hole is asymmetric; alternatively, the diaphragm 240 is a variable aperture diaphragm.

In some embodiments, the imaging system further comprises: and a filter 242 disposed proximate to the diaphragm 240, wherein the filter 242 includes two or more bandpass filter regions having different passbands.

In some embodiments, the filtering device 242 is a filter, and the distance between the filter and the diaphragm 240 is not more than 10 mm; the filter film comprises red, green and blue band-pass filter regions which are distributed in a Y shape.

In some embodiments, the lens 210 is a telecentric lens or a quasi-telecentric lens.

In some embodiments, the light-transmissive portion of the stop 240 generally approximates a circle having a radius R, the lens group 220 has an equivalent focal length f, and a characteristic angle of illumination θ = arctan (R/f), wherein the characteristic angle of illumination θ is no greater than 10 degrees.

In some embodiments, the light transmitted by the diaphragm 240 is refracted and/or reflected to form emergent light, and the image forming system outputs the emergent light through the lens 210 to illuminate an image formed on a metal surface.

A third aspect of embodiments of the present invention provides a high precision imaging method using an imaging system as described above to obtain an image of at least one surface of an item to be inspected.

A fourth aspect of an embodiment of the present invention provides a detection apparatus, including: the carrying device, the image acquisition device and the high-precision imaging system are arranged on the carrying device; wherein,

the carrying device comprises a bearing table, and the bearing table can bear an article to be tested and dynamically move the article to be tested into or out of the observation range of the imaging system;

the imaging system is used for projecting light rays to the article to be detected and generating an optical image;

the image acquisition device is used for acquiring the optical image.

In some embodiments, the inspection apparatus further includes an image recognition device for recognizing the optical image to detect a defect condition of the object to be inspected.

According to the technical scheme provided by the embodiment of the invention, the consistency of imaging is effectively improved through the integrated arrangement of the illumination and the imaging lens, and a high-precision and stable workpiece image can be obtained.

Drawings

The features and advantages of the present invention will be more clearly understood by reference to the accompanying drawings, which are illustrative and not to be construed as limiting the invention in any way, and in which:

FIG. 1 is a schematic diagram of a conventional shallow cut defect in the art;

FIG. 2 is a schematic diagram of a high precision imaging system according to some embodiments of the present invention;

FIG. 3 is a schematic diagram of a high precision imaging system according to further embodiments of the present invention;

FIG. 4A is an example of an asymmetric shape of a single monochromatic light emitting area or aperture clear hole, shown in accordance with some embodiments of the present invention;

fig. 4B is an example of an arrangement of a plurality of bandpass filtering regions of a plurality of monochromatic light-emitting areas or filtering devices according to some embodiments of the present invention.

Detailed Description

In the following detailed description, numerous specific details of the invention are set forth by way of examples in order to provide a thorough understanding of the relevant disclosure. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. It should be understood that the use of "system," "device," "unit" and/or "module" terminology herein is a method for distinguishing between different components, elements, portions or assemblies at different levels of sequential arrangement. However, these terms may be replaced by other expressions if they can achieve the same purpose.

It will be understood that when a device, unit or module is referred to as being "on" … … "," connected to "or" coupled to "another device, unit or module, it can be directly on, connected or coupled to or in communication with the other device, unit or module, or intervening devices, units or modules may be present, unless the context clearly dictates otherwise. Although the terms "top," "bottom," "front," "back," "side," and the like may be used in this specification to describe various example features and elements of the invention, these terms are used herein for convenience only, e.g., in the orientation of the examples described in the figures. Nothing in this specification should be construed as requiring a specific three dimensional orientation of structures in order to fall within the scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. As used in the specification and claims of this application, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to be inclusive in the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" are intended to cover only the explicitly identified features, integers, steps, operations, elements, and/or components, but not to constitute an exclusive list of such features, integers, steps, operations, elements, and/or components. For example, as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

These and other features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will be better understood upon consideration of the following description and the accompanying drawings, which form a part of this specification. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. It will be understood that the figures are not drawn to scale.

Various block diagrams are used in the present invention to illustrate various variations of embodiments according to the present invention. It should be understood that the foregoing and following configurations are not intended to limit the present invention. The protection scope of the invention is subject to the claims.

In the prior art, the efficiency and the accuracy of workpiece detection are expected to be improved by a machine vision technology, but when a common light source and a common industrial lens are adopted, the imaging quality of an acquired image cannot be ensured, the dynamic detection requirement cannot be met, the increasingly severe workpiece surface defect detection requirement cannot be met, and the method is particularly not suitable for the detection of metal surface parts. In view of this, the embodiment of the present invention provides a high-precision imaging system, which effectively improves the consistency of illumination and imaging by integrally arranging the illumination and imaging lenses, and can obtain a high-precision and stable workpiece image.

In one embodiment of the present invention, as shown in fig. 2, the high precision imaging system comprises: a lens 110, a lens group 120, a spectroscope 130 and a light-emitting surface 141; the lens group 120 has equivalent positive focal power (i.e. diopter is positive, and diopter power is equivalent to a convex lens), a focal point and a first lens optical axis, and the position difference between the light-emitting surface 141 and an equivalent focal plane of the lens group 120 (a plane passing through the equivalent focal point and perpendicular to the first lens optical axis) does not exceed a first preset range; the first lens optical axis is reflected by the beam splitter 130 to form a second lens optical axis; the lens 110 has a lens optical axis, the lens optical axis passes through the beam splitter 130, and an angle deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range.

In the embodiment of the present invention, the lens assembly 120 is located between the light-emitting surface 141 and the beam splitter 130, light emitted from the light-emitting surface 141 is refracted by the lens assembly 120 and then irradiates the beam splitter 130, and then is reflected by the beam splitter 130 to form emergent light (another part of the light is transmitted at the beam splitter 130, which is not considered for the moment), and the lens 110 is located on the other side of the beam splitter 130 opposite to the emergent light. To ensure effective reflection of light by the beam splitter 130, the beam splitter 130 is preferably inclined at an angle to the optical axis of the first lens. In the preferred embodiment of fig. 2, the included angle between the beam splitter 130 and the optical axis of the first lens is 45 degrees, but it should be understood by those skilled in the art that the included angle may also be set to be different angles such as 30 degrees, 40 degrees or 60 degrees, as long as the light can be effectively reflected to form emergent light, and therefore the degree of the included angle should not be considered as a limitation to the specific embodiment of the present invention.

In the embodiment of the present invention, the lens group 120 may be a single lens or a group of lenses, and a single convex lens is taken as an example in fig. 2, but it should be understood by those skilled in the art that a lens group consisting of a plurality of lenses may also be equivalent to a convex lens effect, which is also applicable to the technical solution of the present invention, and thus the form of the lens herein should not be taken as a limitation to the specific embodiment of the present invention. In addition, the convex lens can adopt a traditional convex lens, and also can adopt a Fresnel lens. The Fresnel lens is also called as a screw lens, is mostly formed by injection molding of polyolefin materials and can also be made of glass or organic glass, one surface of the lens surface of the Fresnel lens is a smooth surface, and the other surface of the lens surface of the Fresnel lens is a concentric circle from small to large.

In a preferred embodiment of the present invention, the light-emitting surface 141 coincides with a position of an equivalent focal plane of the lens group 120, the lens optical axis is parallel to the second lens optical axis, and a lens field of view is set corresponding to an illumination range (a lens field of view includes a part or all of the illumination range of the light source). However, it should be understood by those skilled in the art that the above two overlapping/parallel situations are only preferred embodiments, and in fact, the technical problem can be solved by the present invention when the light emitting surface 141 has a certain translation and/or tilt relative to the focal plane, or when the optical axis of the lens has a certain tilt relative to the optical axis of the second lens, or even when both situations occur, so that the overlapping/parallel positions should not be considered as limiting the specific embodiments of the present invention. Optionally, the first preset range is a distance deviation of ± 10mm (or 10% of the effective focal length of the corresponding lens group, based on the distance between two points where the optical axis of the first lens passes through the light emitting surface 141 and the focal plane) and/or an angle deviation of ± 20 degrees; preferably, the first preset range is a distance deviation ± 5mm (or 5% of the effective focal length of the corresponding lens group) and/or an angle deviation ± 10 degrees; and more preferably, the first preset range is a distance deviation ± 3mm (or 3% of an effective focal length of the corresponding lens group) and/or an angle deviation ± 5 degrees. The second predetermined range is an angular deviation of ± 15 degrees, preferably the second predetermined range is an angular deviation of ± 10 degrees, more preferably the angular deviation is ± 5 degrees. It will be understood by those skilled in the art that smaller deviations in the more preferred embodiments mean better technical results, but it should be noted that even the largest deviations in the above-mentioned claims may still achieve sufficient technical results, and that the preferred or optimal embodiments should not be considered as a specific limitation of the first preset range and/or the second preset range of the present invention.

In one embodiment of the present invention, the light emitting surface 141 can be an equivalent light emitting plane, with various implementations. For example, in the preferred embodiment shown in fig. 2, light from the light source 150 is directed onto a diffuser plate 140 to form a light emitting surface 141. Further, the light emitting surface 141 may be provided with some specific arrangements to obtain more ideal outgoing light. For example, the light emitting surface 141 may have a single color light emitting area whose boundary shape is an asymmetrical shape; or the light emitting face 141 may have more than two monochromatic light emitting areas (each of which is a different color). More preferably, referring to fig. 4A, when there is only one single color light emitting area, the arrangement of the asymmetrical shape with respect to the optical axis of the first lens (the dots near the shapes in fig. 4A indicate the points where the optical axis of the first lens passes through the light emitting surface) may have various forms such as a fan shape, a fan ring, an offset rectangle, an arbitrary asymmetrical closed curve, or a plurality of combined asymmetrical shapes. While referring to fig. 4B, there are many other symmetrical or asymmetrical arrangements when there are more than two monochromatic light emitting areas of different colors, fig. 4B shows several exemplary preferred embodiments in which different numbers indicate monochromatic light emitting areas of different colors. More preferably, the luminous surface of the invention comprises 3 single-color luminous zones with different colors, and the 3 single-color luminous zones are all fan-shaped and distributed on the same circular surface, such as two preferred embodiments in the first row of fig. 4B. Preferably, the 3 monochromatic light emitting areas are distributed in a Y shape, and the colors are red, green and blue. The monochromatic light emitting area can be a color coating with a specific shape on the diffusion plate or a filter with a specific shape which is additionally arranged independently.

In another preferred embodiment of the present invention, the light emitting surface 141 may also be formed by a planar light emitting device, such as any type of display panel or display screen known in the art, including but not limited to a liquid crystal screen (in the form of an LCD or LED, etc.), a CRT display screen, a PDP display screen, etc. In this embodiment, the single-color light-emitting area shown in fig. 4A or 4B may preferably be realized by a specific display screen output by the planar light-emitting device. Through the arrangement of the plurality of single-color light emitting areas in the preferred embodiment of the invention, emergent light projected on any point on the surface of an object to be detected can have different color partitions at different phases (different directions), light collection is carried out through the lens at the specific position in the invention, and then images collected from different directions can show different color effects, so that fine defects on the object to be detected (a miniature workpiece) can show obvious differences in collected images (the surface of the workpiece at the defect position has geometric differences, and the collected images can show color differences at the position), thereby improving the imaging quality of the defect position, improving the precision and the accuracy of defect detection, and being suitable for dynamic detection. Similarly, when only one monochromatic light emitting area is provided, emergent light projected on any point of the surface of an object to be detected can be enabled to present illumination subareas with different intensities (or light has or does not have) on different phases (directions) through the arrangement of the asymmetric shape relative to the optical axis of the first lens, light collection is carried out through the lens at the specific position in the invention, and further images collected from different directions can present different gray scale effects, so that fine defects on the object to be detected (a miniature workpiece) can present differences in collected images (the surface of the workpiece at the defect position has geometric differences, and the collected images can present gray scale differences at the position), thereby improving the imaging quality of the defect position, improving the precision and accuracy of defect detection, and being applicable to dynamic detection.

More preferably, in the embodiment of the present invention, the light emitting area of the light emitting surface 141 is generally circular or approximately circular (i.e., all the light emitting areas are generally distributed in a circular or approximately circular area), the circular area has a radius R, the lens group 120 has an equivalent focal length f, and the characteristic angle of lighting is θ = arctan (R/f), wherein the characteristic angle of lighting θ is not greater than 10 degrees. By limiting the size of the lighting characteristic angle θ, the divergence degree of the light emitted from the light emitting surface 141 can be controlled, so that the final emergent light has a better visual angle and is concentrated in a certain visual field range.

In another preferred embodiment of the present invention, the light emitting area of the light emitting surface 141 may be generally rectangular, elliptical, or a generally closed curve shape, the size of the generally closed curve shape is further limited to obtain a better lighting effect, and in particular, the generally closed curve shape (including rectangular, elliptical) or the like has a minimum circumscribed rectangle, the maximum inscribed circle of the minimum circumscribed rectangle has a radius r, the lens group 120 has an equivalent focal length f, and the lighting characteristic angle θ = arctan (r/f), wherein the lighting characteristic angle θ is not greater than 10 degrees. By limiting the size of the lighting characteristic angle θ, the divergence degree of the light emitted from the light emitting surface 141 can be controlled, so that the final emergent light has a better visual angle and is concentrated in a certain visual field range.

Specifically, the light emitted from the light emitting surface 141 is refracted and/or reflected to form an emergent light, and the imaging system outputs the emergent light through the lens 110 to illuminate an image formed on a metal surface (a surface of a metal product or a surface of any product plated with metal). Typical metal-plated surfaces are usually nickel-plated, chrome-plated, zinc-plated, etc., but obviously other forms are also applicable to the solution of the present invention, so that no specific limitation is made to the specific form of the metal surface here. By adopting the technical scheme of the embodiment of the invention, the metal surface with high light reflection property can have excellent imaging effect, and the technical problem which cannot be solved for a long time in the prior art is effectively solved.

Through the arrangement of the position relation of the light-emitting surface and the lens in the preferred embodiment of the invention, the light angle projected to the surface to be detected is standardized, the defect display of the inhibition of redundant stray light is avoided, and meanwhile, the position of the optical axis of the lens is specially regulated so that the imaging optical path and the illumination optical path are matched with each other, so that the consistent imaging is realized on the surface of a workpiece, particularly a metal surface, the geometric characteristics of which conform to normal distribution, and the detection capability of the corresponding metal surface is greatly improved. Through the setting of a plurality of monochromatic luminous areas in preferred embodiment, can let the emergent light of throwing on waiting to detect article have the subregion of different colours, based on the coaxial relation of camera lens and illumination, and then the image of gathering from different directions can demonstrate different colour effects, this makes to detect slight defect on article (miniature work piece, metal surface etc.) can demonstrate apparent difference in the collection image (defect department work piece surface has geometric difference, it can demonstrate the color difference to gather the image in this department), thereby defect department image quality has been promoted, the precision and the accuracy of defect detection have been improved, it is applicable in dynamic detection.

Fig. 3 is a schematic structural diagram of a high-precision imaging system in another embodiment of the present invention, as shown in fig. 3, the high-precision imaging system includes: lens 210, lens group 220, beam splitter 230, stop 240 and illuminant 250; wherein the lens group 220 has equivalent positive focal power, focal point and first lens optical axis, and the position difference between the plane (light emitting surface 241 in fig. 3) of the stop 240 and the equivalent focal plane of the lens group 220 is not more than a first preset range; the first lens optical axis is reflected by the beam splitter 230 to form a second lens optical axis; the lens 210 has a lens optical axis, the lens optical axis passes through the beam splitter 230, and an angle deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range.

Compared with fig. 2, the embodiment of fig. 3 mainly adjusts the form of light emission, and the light emitted by the light emitting body 250 forms emergent light through the adjustment of the diaphragm 240. The stop 240 is a device including a light shielding portion and a light transmitting portion, and light emitted by the light emitter 250 passes through the light transmitting portion of the stop 240 (i.e., the emergent light adjusted by the stop 240 is formed at the light emitting surface 241) and irradiates on the lens group 220. In a preferred embodiment of the present invention, the light-transmitting portion of the diaphragm 240 is a light-transmitting hole, and the profile of the light-transmitting hole is an asymmetric shape, such as a sector structure of a semicircle, a quarter circle, etc.; see in particular the various arrangements of the asymmetrical shape with respect to the optical axis of the first lens shown in fig. 4A. In another preferred embodiment of the invention, the diaphragm 240 is a variable aperture diaphragm, such as in the form of an iris diaphragm. Preferably, the diaphragm 240 can have a plurality of shielding blades and an inner hole, the shielding blades can be arranged in a plurality of manners, the plurality of shielding blades jointly form the inner hole, the shielding blades are used for shielding part of light rays, the other part of light rays can pass through the inner hole, and the size of the inner hole of the diaphragm 240 can be adjusted, so that the size and/or the shape of the boundary of the light emitting surface can be controlled, and the light emitting effect can be adjusted to be suitable for workpieces with different surfaces or defects with different characteristics.

Furthermore, in one embodiment of the present invention, the imaging system may further include a filter device 242 disposed proximate to the diaphragm 240, wherein the filter device 242 includes more than two bandpass filter regions with different passbands (i.e., the bandpass filter devices emit light of different colors under white light illumination); such as the arrangement of various symmetrical or asymmetrical shapes shown in fig. 4B. Preferably, the filtering means is a filter, and the distance between the filter and the diaphragm 240 is not more than 10mm, more preferably not more than 5 mm; the filter film comprises three band-pass filter areas distributed in a Y shape. Preferably, the three band-pass filtering regions are three colors of red, green and blue. Similar to the effect of setting the monochromatic light emitting area in the preferred embodiment of fig. 2, the shape of the diaphragm 240 and/or the setting of the filtering device 242 are also for obtaining ideal emergent light, so that the fine defects on the object to be detected (the miniature workpiece) can show significant difference in the collected image, thereby improving the imaging quality at the defect position and improving the precision and accuracy of defect detection. More preferably, in the embodiment of the present invention, the light-transmitting portion of the diaphragm 240 is generally circular or approximately circular (i.e. all light-emitting areas are generally distributed in a circular or approximately circular area), the circular area has a radius R, the lens group 220 has an equivalent focal length f, and the characteristic angle of light striking is θ = arctan (R/f), wherein the characteristic angle of light striking is θ is not greater than 10 degrees. By limiting the size of the light striking characteristic angle θ, the divergence degree of the light transmitted by the diaphragm 240 can be controlled, so that the final emergent light has a better visual angle and is concentrated in a certain visual field range.

Specifically, the light transmitted through the diaphragm 240 is refracted and/or reflected to form emergent light, and the imaging system outputs the emergent light through the lens 210 to irradiate an image formed on a metal surface (the surface of a metal product or the surface of any product plated with metal). Typical metal-plated surfaces are usually nickel-plated, chrome-plated, zinc-plated, etc., but obviously other forms are also applicable to the solution of the present invention, so that no specific limitation is made to the specific form of the metal surface here. By adopting the technical scheme of the embodiment of the invention, the metal surface with high light reflection property can have excellent imaging effect, and the technical problem which cannot be solved for a long time in the prior art is effectively solved.

In the preferred embodiment of fig. 3, the implementation of the lens group 220 is similar to that described in the preferred embodiment of fig. 2, and may be a single lens or a lens group consisting of a plurality of lenses; the positional relationship of the lens 210, the lens group 220, the beam splitter 230, etc. and the angular disposition of the beam splitter 230 are similar to those of the preferred embodiment of fig. 2, and will not be described again.

Similarly, in a preferred embodiment of the present invention, the plane (the light emitting surface 241 in fig. 3) of the stop 240 coincides with the position of the equivalent focal plane of the lens group 220, the lens optical axis is parallel to the second lens optical axis, and the lens field of view is set corresponding to the illumination range (including part or all of the illumination range of the light source in the lens field of view). However, it should be understood by those skilled in the art that the above two cases of coincidence/parallelism are only preferred embodiments, and in fact, the technical problem can be solved by the technical solution of the present invention when the plane of the diaphragm 240 has a certain translation and/or tilt relative to the focal plane, or when the optical axis of the lens has a certain tilt relative to the optical axis of the second lens, or even when both cases occur, so that the position coincidence/parallelism should not be regarded as a limitation to the specific embodiments of the present invention. Optionally, the first preset range is a distance deviation of ± 10mm (or 10% of the effective focal length of the corresponding lens group, based on the distance between two points where the first lens optical axis passes through the light emitting surface 241 and the focal plane) and/or an angle deviation of ± 20 degrees; preferably, the first preset range is a distance deviation ± 5mm (or 5% of the effective focal length of the corresponding lens group) and/or an angle deviation ± 10 degrees, and more preferably, the first preset range is a distance deviation ± 3mm (or 3% of the effective focal length of the corresponding lens group) and/or an angle deviation ± 5 degrees. The second predetermined range is an angular deviation of ± 15 degrees, preferably the second predetermined range is an angular deviation of ± 10 degrees, more preferably the angular deviation is ± 5 degrees. It will be understood by those skilled in the art that smaller deviations in the more preferred embodiments mean better technical results, but it should be noted that even the largest deviations in the above-mentioned claims may still achieve sufficient technical results, and that the preferred or optimal embodiments should not be considered as a specific limitation of the first preset range and/or the second preset range of the present invention.

Further, in a preferred embodiment of the present invention, the lens used in the embodiment of fig. 2 or fig. 3 may be further optimized, and a telecentric lens (such as an object-side telecentric lens or a double telecentric lens) or a quasi-telecentric lens is used to replace the common industrial lens. The quasi-telecentric lens is characterized in that the position difference (distance on an optical axis) between the center of a lens diaphragm and the image space focus of a front group of lenses is less than 10% of the effective focal length of the front group of lenses, and the front group of lenses are lens groups positioned on the front side (object side) of the diaphragm in the lens. The telecentric lens or the quasi-telecentric lens has a specific parallel light path design, so that the magnification of the presented image does not change along with the distance within a certain object distance range, the parallax problem of the traditional industrial lens can be effectively corrected, and the imaging quality is further improved. However, in the technical field, a telecentric lens is generally used for size measurement, and a common industrial FA lens is generally used for defect detection, instead of using the telecentric lens during defect detection (in the prior art, it is generally considered that an industrial lens can obtain a clearer image through focusing, so that the application range of the telecentric lens is limited). The preferred embodiment of the invention realizes the optimal matching of the illumination and imaging light paths by using the telecentric lens and matching with the special light source and the specific position relation of a plurality of components, and especially can realize the optimal optical matching with the illumination light path with the light ray angle specified, thereby realizing better imaging consistency and fine defect expression by using the telecentric lens, realizing the optimal effect, effectively breaking the technical bias and obtaining unexpected technical effect.

More preferably, the telecentric lens has an adjustable diaphragm. The adjustable diaphragm can adjust the angle of light rays entering the lens according to needs. In the preferred embodiment of the invention, because the specially-made light source with good consistency is adopted, and the telecentric lens is adopted, the slight defect can present an obvious difference image, and the defect detection precision is obviously improved. However, in some cases, the workpiece is allowed to have certain tolerance and/or slight flaw, and the overhigh detection precision may cause certain false alarm, and the later software identification algorithm is required to consume calculation force for screening and removing. Therefore, in the preferred embodiment of the invention, the adjustable diaphragm can properly adjust (such as widening or tightening) the imaging precision by adjusting the angle of the light rays entering the lens, so that whether certain fine flaws are imaged or not is selected according to needs, the false alarm condition is reduced in the imaging link, and the computational power requirement of later software is effectively reduced.

In one embodiment of the invention, there is also provided a high precision imaging method using the imaging system as described above to obtain an image of at least one surface of an article to be inspected.

Further, in an embodiment of the present invention, there is also provided a detection apparatus, including a carrying device, an image capturing device and the high precision imaging system; the carrying device comprises a carrying table, wherein the carrying table can carry an article to be tested and dynamically move the article to be tested into or out of an observation range of the imaging system; the imaging system is used for projecting light rays to the article to be detected and generating an optical image; the image acquisition device is used for acquiring the optical image. Preferably, the detection apparatus further includes an image recognition device for recognizing the optical image to detect a defect condition of the object to be detected. Preferably, detecting the defect condition of the object to be detected refers to: and detecting whether the article to be detected has defects, and further detecting the positions and/or types of the defects when the defects exist.

It should be understood by those skilled in the art that the claims and the embodiments of the specification of the present invention are only examples of the preferred embodiments, and should not be construed as limiting the embodiments of the present invention. Typically, the subject in various positional relationships illustrated may be an objective subject, or the virtual image may be constructed by a plane mirror or other feasible means, so that the subject in various positional relationships is a virtual image of the objective subject. Those skilled in the art can make various conversions on various positional relationships of examples and their subjects without creative efforts, and the results of the conversions should be considered to be within the scope of the claims of the present invention.

In summary, embodiments of the present invention provide a high-precision imaging system, method and detection device, which effectively improve the imaging consistency and obtain a high-precision and stable workpiece image by the integrated arrangement of the illumination and the imaging lens. More specifically, in the preferred embodiment of the invention, the imaging consistency of the part to be detected in the lens field of view is improved, the shape and/or color of the light-emitting region in the imaging system can be further improved, the defect imaging effect is further improved, the defects of the illumination and imaging system which affect the imaging stability are further eliminated, and the better realization of the machine vision dynamic detection is ensured.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.

Claims

1. A high precision imaging system, characterized in that it comprises: the lens comprises a lens (110), a lens group (120), a spectroscope (130) and a light-emitting surface (141); wherein,

the lens group (120) comprises at least one lens having an equivalent positive power, a focal point and a first lens optical axis;

the position difference between the light-emitting surface (141) and the equivalent focal plane of the lens group (120) does not exceed a first preset range;

the first lens optical axis is reflected by the beam splitter (130) to form a second lens optical axis;

the lens (110) is provided with a lens optical axis, the lens optical axis passes through the spectroscope (130), and the angular deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range;

2. An imaging system according to claim 1, wherein the light emitting face (141) is produced by illumination of a light source on a diffuser plate or by a planar light emitting device.

3. The imaging system of claim 1 or 2, wherein the light emitting face (141) has a single color light emitting area, a boundary shape of the single color light emitting area being asymmetrical with respect to the first lens optical axis; alternatively, the light emitting surface (141) has two or more monochromatic light emitting areas of different colors.

4. An imaging system according to claim 3, wherein the light emitting face (141) has three monochromatic light emitting areas which are Y-shaped and are three colors red, green and blue, respectively.

5. The imaging system of any of claims 1, 2, or 4, wherein the lens (110) is a telecentric lens or a quasi-telecentric lens.

6. The imaging system of claim 5, wherein the telecentric or quasi-telecentric lens has an adjustable stop.

7. The imaging system of claim 5, wherein the first preset range is a distance deviation ± 5mm and/or an angle deviation ± 15 degrees; the second preset range is an angle deviation of +/-10 degrees.

8. The imaging system of claim 1, wherein the light emitting area of the light emitting face (141) generally approximates a circle having a radius R, the lens group (120) has an equivalent focal length f, and a characteristic angle of illumination θ = arctan (R/f), wherein the characteristic angle of illumination θ is no greater than 10 degrees.

9. The imaging system according to claim 8, wherein the light emitted from the light emitting surface (141) is refracted and/or reflected to form emergent light, and the imaging system outputs the image formed by the emergent light irradiating on the metal surface through the lens (110).

10. A high precision imaging system, characterized in that it comprises: the lens comprises a lens (210), a lens group (220), a spectroscope (230), a diaphragm (240) and a luminous body (250); wherein,

the lens group (220) comprises at least one lens having an equivalent positive power, a focal point and a first lens optical axis;

the difference between the position of the plane of the diaphragm (240) and the position of the equivalent focal plane of the lens group (220) is not more than a first preset range;

the first lens optical axis is reflected by the beam splitter (230) to form a second lens optical axis;

the lens (210) is provided with a lens optical axis, the lens optical axis passes through the spectroscope (230), and the angular deviation between the lens optical axis and the second lens optical axis does not exceed a second preset range;

11. The imaging system according to claim 10, wherein the light-transmissive portion of the diaphragm (240) is a light-transmissive hole having an asymmetric profile; alternatively, the diaphragm (240) is a variable aperture diaphragm.

12. The imaging system of claim 10, further comprising: a filter arrangement (242) disposed proximate to the diaphragm (240), the filter arrangement (242) including more than two bandpass filter regions having different passbands.

13. The imaging system according to claim 12, characterized in that the filtering means (242) is a filter, which is at a distance of not more than 10mm from the diaphragm (240); the filter film comprises red, green and blue band-pass filter regions which are distributed in a Y shape.

14. The imaging system of any of claims 10-13, wherein the lens (210) is a telecentric lens or a quasi-telecentric lens.

15. The imaging system of claim 14, wherein the telecentric or quasi-telecentric lens has an adjustable stop.

16. The imaging system of claim 14, wherein the first preset range is a distance deviation ± 5mm and/or an angle deviation ± 15 degrees; the second preset range is an angle deviation of +/-10 degrees.

17. The imaging system of claim 10, wherein the light-transmissive portion of the stop (240) generally approximates a circle having a radius R, the lens group (220) has an equivalent focal length f, and a characteristic angle of illumination θ = arctan (R/f), wherein the characteristic angle of illumination θ is no greater than 10 degrees.

18. The imaging system according to claim 17, wherein the light transmitted by the diaphragm (240) is refracted and/or reflected to form emergent light, and the imaging system outputs the image formed by the emergent light on the metal surface through the lens (210).

19. A high precision imaging method, characterized in that an imaging system according to any of claims 1-18 is used to obtain an image of at least one surface of an object to be inspected.

20. A detection apparatus, comprising: a carrier device, an image acquisition device and a high precision imaging system according to any of claims 1-18; wherein,

the image acquisition device is used for acquiring the optical image.

21. The inspection apparatus of claim 20, further comprising an image recognition device for recognizing the optical image to detect a defect condition of the object to be inspected.