An imaging and illumination method for bolt outer surface quality detection

Abstract

The application discloses a kind of imaging and illumination method for bolt outer surface quality detection, comprising the following steps: 1) when detecting the side wall of bolt, the side wall of bolt is illuminated using dark field illumination mode, and the camera is used to obtain side wall imaging with optical axis perpendicular to the side wall of bolt;2) when detecting the end face of bolt, the camera is placed on the extension line of bolt central axis, the optical axis of camera overlaps with the central axis of bolt, a half-mirror half-transmission lens is arranged between the end face of bolt and camera, a light source is arranged on the side of half-mirror half-transmission lens, and the light emitted by the light source is reflected to the end face of bolt after being reflected to the half-mirror half-transmission lens;If a groove is provided on the end face of bolt, a divergent light source is used to illuminate the inner side wall of groove, and the optical axis of camera and the central axis of bolt form an angle of 25-45 ° to shoot the inner side wall of groove.The application realizes full-range high-precision imaging of bolt outer surface by improving and designing the imaging and illumination method, which can meet the bolt detection requirements in the field of high reliability.

Description

TECHNICAL FIELD

[0001] The application relates to an imaging and illumination method for detecting the outer surface quality of a bolt, and belongs to the technical field of bolt outer surface detection. BACKGROUND

[0002] Bolt shanks are the most commonly used fastening parts and are widely used in various industries. In many application fields requiring high reliability, such as aerospace, railway, automobile, nuclear power station, bridge and the like, the quality detection of bolt shanks becomes an important link that cannot be ignored in the production process.

[0003] At present, machine vision has begun to enter the detection field of bolt shanks, but is basically limited to profile detection and size measurement with relatively low algorithm requirements. Although there are currently some reports about defect detection of bolt shanks, the focus is on the design of mechanical structures such as conveying, clamping, rotating and classifying, and the detection requirements of high-precision industries cannot be met. For example, a patent with the application number 201822274251.5 discloses a bolt detection system, which comprises a rotating conveying device, a head detection device and a shank detection device. The rotating conveying device comprises a rotating disc, a rotating shaft and a clamping groove. The head detection device comprises a head detection camera. The shank detection device comprises a shank detection camera. Although the detection efficiency is improved to a certain extent, the transition between the stem and the head of the bolt is not a right-angle transition, and the head is not a simple column. The patent does not introduce how to adjust the illumination and imaging for each part, and therefore cannot meet the detection requirements of high-precision industries. For another example, a patent with the application number 201810573052.6 discloses a bolt detection and sorting device, which comprises a rack, a vibrating feeding mechanism, a reversing device, a feeding device, a first positioning device, a second positioning device, a first camera detection device and a second camera detection device. The bolt can be arranged and reversed and then conveyed to the second industrial camera for detection of the two ends of the bolt. Then, the bolt is controlled to rotate through an electromagnetic driving disc, and the second industrial camera detects the circumference of the bolt. According to the detection result, the sorting cylinder is used for sorting and rejecting, and the working efficiency is improved. However, the circumference of the bolt is not a simple column with equal diameter. The patent does not introduce how to adjust the illumination and imaging for each part, and therefore cannot meet the detection requirements of high-precision industries.

[0004] The quality requirements for bolts in key parts such as automobiles, airplanes and bridges are very high. Any defect may cause safety accidents. The existing detection equipment cannot meet the high-precision requirements. Manual detection has the problems of low efficiency and high intensity. In addition, the outer shape characteristics of different bolt shanks are different. How to obtain high-quality appearance images to meet the detection requirements of high-precision industries becomes a technical problem to be solved urgently. SUMMARY

[0005] The application provides an imaging and illumination method for bolt outer surface quality detection.

[0006] To solve the above technical problems, the application adopts the following technical solutions:

[0007] An imaging and illumination method for bolt outer surface quality detection comprises the following steps:

[0008] 1) When detecting the side wall of the bolt, the side wall of the bolt is illuminated by using dark field illumination, and the camera is used to obtain side wall imaging in a manner that the optical axis (the optical axis of the camera) is perpendicular to the side wall of the bolt, that is, the camera is installed on the side of the bolt, and the optical axis of the camera is perpendicular to the side wall of the bolt;

[0009] 2) When detecting the end face of the bolt, the camera is placed on the extension line of the central axis of the bolt, the optical axis of the camera overlaps the central axis of the bolt, a half-mirror is arranged between the end face of the bolt and the camera, and a light source is arranged on the side of the half-mirror, so that the light emitted by the light source is reflected to the end face of the bolt through the half-mirror;

[0010] If the end face of the bolt is provided with a groove, a divergent light source is used to illuminate the inner side wall of the groove, and the optical axis of the camera and the central axis of the bolt form an included angle of 25-45° to shoot the inner side wall of the groove.

[0011] The work station, blanking and other schemes during detection can refer to the prior art. The key of the application lies in the design of imaging and illumination of each part of the outer side of the bolt to obtain high-quality imaging and realize high-precision detection of the outer surface quality of the bolt.

[0012] In the step 2), the half-mirror is arranged to realize flexible illumination of the end face of the bolt and good imaging of each part of the end face; and the half-mirror can change the direction of the illumination light by folding back in the same light working wave band, and also can allow the camera to shoot the target through the half-mirror.

[0013] In order to further improve the imaging quality, in the step 1), the parallel light is illuminated to the side wall of the bolt at an angle of 120-160° relative to the side wall of the bolt to realize dark field illumination. This illumination method does not produce bright field shining light spots in the field of view of the camera, that is, the effect of dark field illumination is produced, and high-quality imaging photos can be obtained by using the camera with the optical axis perpendicular to the side wall of the bolt.

[0014] In order to obtain a complete image of the outer circumferential surface of the bolt shank, in the step 1), if the camera is a line array camera, the bolt is rotated at 360 degrees around the central axis of the bolt as the rotating shaft to realize 360-degree continuous shooting without dead angle.

[0015] If the camera is a surface array camera, a photo is taken every 60-120 degrees during the 360-degree rotation of the bolt around its (bolt) central axis, and then the photos are spliced into a complete image of the outer surface of the bolt side wall; or, without rotating the bolt, a surface array camera is installed every 60-120 degrees in the (bolt) circumferential direction, and then the photos are spliced into a complete image of the outer surface of the bolt side wall.

[0016] In order to further improve the detection accuracy, in step 1), at least one camera with its optical axis perpendicular to the outer side wall of the bolt is added every time the angle of the outer side wall of the bolt changes.

[0017] When the outer side wall of the bolt is not parallel to the axial direction of the bolt, the parallel light is illuminated at an angle of 120-160° with respect to the segment of the bolt side wall to perform dark field illumination, and the optical axis of the camera corresponding to the segment of the bolt side wall is perpendicular to the segment of the bolt side wall.

[0018] In order to obtain high-definition imaging of each segment, in step 1), at least one camera with its optical axis perpendicular to the outer side wall of the bolt is added every time the diameter changes when the outer side wall of the bolt is parallel to the axial direction of the bolt.

[0019] In the above step 2), the half-reflective half-transmissive lens is inclined at an angle of 45° with respect to the central axis of the bolt.

[0020] In order to obtain the image of the entire inner circumferential surface of the groove inner side wall, in step 2), when imaging the groove inner side wall of the end face of the bolt, if the camera is a linear array camera, the bolt is rotated 360 degrees around its (bolt) central axis to realize 360-degree continuous shooting without dead angle;

[0021] If the camera is a surface array camera, a photo is taken every 60-120 degrees during the 360-degree rotation of the bolt around its (bolt) central axis, and then the photos are spliced into a complete image of the outer surface of the bolt side wall; or, without rotating the bolt, a surface array camera is installed every 60-120 degrees in the (bolt) circumferential direction, and then the photos are spliced into a complete image of the outer surface of the bolt side wall.

[0022] The fastening bolt of the automobile wheel hub is very important for the driving safety of the automobile, and the production quantity is very large. The fastening bolt of the automobile wheel hub comprises a screw rod, a circular arc transition surface and a hexagonal nut which are sequentially connected in the axial direction, the end face of the hexagonal nut is provided with a circular groove, and the inner bottom of the circular groove is provided with a letter.

[0023] The imaging and illumination device of the above bolt comprises a first XYZ three-dimensional pneumatic V-shaped clamp jaw, a side wall detection device, a second XYZ three-dimensional pneumatic V-shaped clamp jaw and an end detection device which are sequentially arranged in the flowing direction of the production line.

[0024] The side wall detection device comprises a first base, a first support, a first camera group, a first parallel light source, a second camera group and a second parallel light source;

[0025] The first base, the first camera group, the first parallel light source, the second camera group and the second parallel light source are all mounted on the first support;

[0026] The first base is arranged at the bottom of the first support, and a bolt fixing device is arranged on the first base;

[0027] The number of the first camera group is more than one, each first camera group comprises more than three first cameras, the optical axis of the first camera is parallel to the horizontal direction, the height of the first camera is adjustable, the first parallel light source forms an angle of 120-160° with the vertical direction, the angle of the first parallel light source with the vertical direction is adjustable, the mounting height of the first parallel light source in the longitudinal direction is higher than that of the first camera, the number of the first parallel light source is equal to that of the first camera group, and the first parallel light source corresponds to the first camera group one by one;

[0028] The number of the second camera group is more than one, each second camera group comprises more than one second camera, the optical axis of the second camera is installed in a downward inclined manner, the angle of the second camera with the vertical direction is adjustable, the irradiation direction of the second parallel light source is inclined from downward to upward, the angle of the second parallel light source with the vertical direction is adjustable, the mounting height of the second parallel light source in the longitudinal direction is lower than that of the second camera, the number of the second parallel light source is equal to that of the second camera group, and the second parallel light source corresponds to the second camera group one by one;

[0029] The first camera and the second camera are of the same type;

[0030] The end detection device comprises a second base, a second support, a third camera, a third light source, a half-reflective half-transmissive lens, a fourth camera group and a fourth light source;

[0031] The second base, the third camera, the third light source, the half-reflective half-transmissive lens, the fourth camera group and the fourth light source are all mounted on the second support;

[0032] The second base is arranged at the top of the second support, an opening downward vertical clamping claw or clamping sleeve is arranged on the second base, the clamping claw or clamping sleeve is movable in the horizontal direction; the third camera, the third light source and the half-reflective half-transmissive lens are all arranged below the second base, the half-reflective half-transmissive lens is installed in an inclined manner at an angle of 45°, the third light source is arranged on the side of the half-reflective half-transmissive lens and the light reflected on the half-reflective half-transmissive lens is upward reflected, the third camera is arranged at the bottom of the half-reflective half-transmissive lens and the optical axis is vertically upward, the clamping claw or clamping sleeve on the second base is movable to a position where the optical axis of the third camera and the central axis are collinear;

[0033] The fourth camera group and the fourth light source are arranged below the second base, the number of the fourth camera group is more than one, each group of the fourth camera group has more than one fourth camera, the optical axis of the fourth camera is inclined upward, the angle between the optical axis of the fourth camera and the vertical direction is adjustable, and the illumination direction of the fourth light source is vertically upward.

[0034] In the bolt outer surface quality detection, the bolt vibration feeder is used for detection. For detection, the bolt vibration feeder adopts existing market products, or existing patent products (application number 201220723884. X, application number 201711257826. 6, application number 201821146572. 0, etc.) can be used.

[0035] The first parallel light source and the vertical direction form an angle of 120-160°, which means that the parallel light emitted by the first parallel light source forms an angle of 120-160° with the vertical direction. This angle can be adjusted to obtain high-quality imaging photos.

[0036] In order to obtain the whole circumferential image, the bolt fixing device on the first base is a rotatable structure, or four groups of first camera groups and four groups of second camera groups are arranged along the circumference of the first base, the angle between adjacent two groups of first camera groups is 90°, the angle between adjacent two groups of second camera groups is 90°, and the first camera and the second camera are both area array cameras.

[0037] The clamping claw or the clamping sleeve on the second base is a rotatable structure, or four groups of fourth camera groups are arranged along the circumference of the fourth light source, and the angle between adjacent two groups of fourth camera groups is 90°.

[0038] The above device is used for the above bolt imaging and illumination method, which includes the following steps:

[0039] 1) Detecting the side wall of the bolt:

[0040] 1.1) Detecting the vertical section of the bolt outside the wall (referring to the outer side wall parallel to the axial direction of the bolt):

[0041] A, the vertical section of the bolt outside the wall includes the side wall of the screw rod, the bottom side wall of the circular arc transition surface and the side wall of the hexagonal nut, the first XYZ three-dimensional pneumatic V-shaped clamping jaw is used to move the bolt to the first base, and the bolt is vertically upward (the screw rod is on the top and the nut is on the bottom) The bolt is sleeved or clamped on the bolt fixing device of the first base.

[0042] B. The bottom side wall of the screw side wall, the arc transition surface, and the hexagonal nut side wall are respectively at least opposite to one of the first camera groups, the first parallel light source corresponding to the first camera group is turned on, the parallel light is irradiated to the screw side wall at an angle of 120-160° relative to the screw side wall to perform dark field illumination, and the first camera group completes imaging of the screw side wall, the bottom side wall of the arc transition surface, and the hexagonal nut side wall, respectively;

[0043] C. The bolt fixing device on the first base is a rotatable structure, the bolt fixing device is rotated, and the bolt is rotated 360 degrees with the axis as the rotation axis, if the first camera is a line array camera, 360-degree continuous shooting without dead angle is performed, if the first camera is a plane array camera, a photo is taken every 90 degrees of rotation, and then the taken photos are spliced into a complete screw side wall outer surface image;

[0044] Or four groups of first camera groups are arranged circumferentially on the first base, the included angle between adjacent two groups of first camera groups is 90°, each group of first camera groups corresponds to a first parallel light source, and the first camera adopts a plane array camera, which also does not need to rotate the bolt, and the four angle photos are spliced into a complete screw side wall outer surface image, that is, one shooting can complete 360-degree imaging without dead angle of the bolt along the axial direction;

[0045] 1.2) Detection of the non-vertical section outer side wall of the bolt (referring to the outer side wall not parallel to the axial direction of the bolt):

[0046] A. The bottom of the arc transition surface is a vertical section, and the rest is a slope in the form of an arc transition, that is, the non-vertical section outer side wall of the bolt; the vertical line of the arc transition surface is determined, the angle of the second camera is adjusted so that the optical axis of the second camera is collinear with the vertical line of the arc transition surface, the second parallel light source is irradiated to the arc transition surface at an angle of 120-160° relative to the arc transition surface to perform dark field illumination, the angle of the second parallel light source is adjusted so that no bright field flash spot is generated in the field of view of the second camera, the effect image of dark field illumination is manufactured, and the imaging of the arc transition surface is completed;

[0047] B. The bolt fixing device on the first base is a rotatable structure, the bolt fixing device is rotated, and the bolt is rotated 360 degrees with the axis as the rotation axis, if the second camera is a line array camera, 360-degree continuous shooting without dead angle is performed, if the second camera is a plane array camera, a photo is taken every 90 degrees of rotation, and then the taken photos are spliced into a complete screw side wall outer surface image;

[0048] Or four groups of second camera groups are arranged circumferentially along the first base, the included angle between two adjacent groups of second camera groups is 90°, each group of second camera groups corresponds to a second parallel light source, and the second camera is a face array camera. This also does not need to rotate the bolt, and the four angle photos are spliced into a complete circular transition surface outer surface image, that is, one shooting can complete 360-degree non-blind imaging of the bolt along the axial direction.

[0049] 2) Detection of the bolt end face and the side wall of the circular groove:

[0050] 2.1) Detection of the bolt end face:

[0051] A. The bolt end face includes the bolt end face periphery and the bottom surface of the circular groove. After the side wall of the bolt is shot, the second XYZ three-dimensional pneumatic V-shaped clamping jaw is used to clamp the screw rod part of the bolt, the first base is moved upward and separated from the first base, and then the second base position is moved to the clamping jaw or clamping sleeve on the second base.

[0052] B. The horizontal position of the clamping jaw or clamping sleeve is adjusted so that the optical axis of the third camera is collinear with the central axis of the bolt, the third light source is diffuse light, the flexible illumination of the bolt head is realized by means of the 45-degree half-reflective half-transmissive lens, and the third camera completes the imaging of the bolt end face.

[0053] 2.2) Detection of the inner side wall of the circular groove on the end face:

[0054] A. After the end face detection is completed, the clamping jaw or clamping sleeve on the second base is moved to a position where the central axis of the clamping jaw or clamping sleeve is collinear with the central axis of the fourth light source, the fourth light source is diffuse light, and the inner side wall of the circular groove is illuminated. In order to shoot the defects on the inner side wall of the circular groove, the fourth camera is adjusted to an inclined angle to obtain the imaging of the inner side wall of the circular groove.

[0055] B. The clamping jaw or clamping sleeve on the second base is a rotatable structure, the clamping jaw or clamping sleeve is rotated to drive the bolt to rotate 360 degrees with the central axis as the rotation axis. If the fourth camera is a line array camera, 360-degree non-blind continuous shooting is performed. If the fourth camera is a face array camera, a photo is taken every 90 degrees, and then the photos are spliced into a complete inner side wall image of the circular groove.

[0056] Or four groups of fourth cameras are arranged circumferentially along the fourth light source, the included angle between two adjacent groups is 90°, and the fourth camera is a face array camera. In this way, the bolt does not need to be rotated, and the four angle photos are spliced into a complete inner side wall image of the circular groove, that is, one shooting can complete 360-degree non-blind imaging of the bolt along the axial direction.

[0057] After the outer surface image is obtained, the defects are analyzed with reference to the prior art.

[0058] The technologies not mentioned in the present application refer to the prior art.

[0059] The imaging and illumination method for bolt outer surface quality detection of the present application realizes all-around high-precision imaging of the bolt outer surface through improvement and design of the imaging and illumination method, and can meet the bolt detection requirements in the high-reliability field. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 It is the imaging of the real bolt to be measured in the embodiment;

[0061] Figure 2 It is Figure 1 the top view;

[0062] Figure 3 It is the imaging principle diagram of the outer side wall of the vertical section of the bolt in the embodiment;

[0063] Figure 4 It is the imaging image of the first camera in the embodiment;

[0064] Figure 5 It is the imaging principle diagram of the outer side wall of the non-vertical section of the bolt in the embodiment;

[0065] Figure 6 It is the imaging image of the circular arc transition surface in the embodiment;

[0066] Figure 7 It is the imaging principle diagram of the end surface of the bolt in the embodiment;

[0067] Figure 8 It is the end surface image obtained in the embodiment;

[0068] Figure 9 It is the imaging principle diagram of the inner side wall of the circular groove on the end surface in the embodiment;

[0069] Figure 10 It is the inner side wall image of the circular groove on the end surface obtained in the embodiment;

[0070] In the figure, 1 is a first base, 2 is a first parallel light source, 3 is a first camera, 4 is a second parallel light source, 5 is a second camera, 6 is a second base, 7 is a third camera, 8 is a third light source, 9 is a half-mirror, 10 is a fourth camera, and 11 is a fourth light source. DETAILED DESCRIPTION

[0071] In order to better understand the present application, the content of the present application will be further illustrated below in combination with the embodiments, but the content of the present application is not limited to only the following embodiments.

[0072] The up, down, left, right, horizontal, vertical and other orientation words in the present application are based on the relative orientation or positional relationship shown in the drawings, and should not be understood as an absolute limitation on the present application.

[0073] As shown in Figures 1-2 , the fastening bolt of the automobile hub includes a screw rod, a circular arc transition surface and a hexagonal nut which are sequentially connected in the axial direction, and the top diameter of the circular arc transition surface is greater than the outer diameter of the hexagonal nut, as shown in Figure 2 , a mesa is formed between the circular arc transition surface and the root of the hexagonal nut, and the end surface of the hexagonal nut is provided with a circular groove, and the bottom of the circular groove is provided with a letter; all defects on the exposed outer surface need to be detected;

[0074] The imaging and lighting device of the above-mentioned bolt includes a first XYZ three-dimensional pneumatic V-shaped clamp jaw, a side wall detection device, a second XYZ three-dimensional pneumatic V-shaped clamp jaw and an end detection device which are sequentially arranged in the flow direction of the production line;

[0075] The side wall detection device includes a first base, a first support, a first camera group, a first parallel light source, a second camera group and a second parallel light source;

[0076] The first base, the first camera group, the first parallel light source, the second camera group and the second parallel light source are all mounted on the first support;

[0077] The first base is arranged at the bottom of the first support, and a bolt fixing device is arranged on the first base, as shown in Figures 3-4 , the bolt fixing device is a circular convex rod, the diameter of the circular convex rod is consistent with the circular recess of the bolt head, and when detecting, the bolt is sleeved on the circular convex rod of the first base through the circular groove, so that the entire outer side surface of the bolt is completely exposed without obstruction, which facilitates the illumination and shooting of the outer side surface;

[0078] The number of the first camera group is one or more, each first camera group has three first cameras, the optical axis of the first camera is parallel to the horizontal direction, and the height of the first camera is adjustable; the first parallel light source forms an angle of 120-160° with the vertical direction, the angle between the first parallel light source and the vertical direction is adjustable, the installation height of the first parallel light source in the longitudinal direction is higher than that of the first camera, and the number of the first parallel light source is equal to and corresponds to the number of the first camera group;

[0079] The number of the second camera group is one or more, each second camera group has one or more second cameras, the optical axis of the second camera is installed obliquely downward, and the angle between the second camera and the vertical direction is adjustable; the irradiation direction of the second parallel light source is obliquely upward from the bottom, the angle between the second parallel light source and the vertical direction is adjustable, the installation height of the second parallel light source in the longitudinal direction is lower than that of the second camera, and the number of the second parallel light source is equal to and corresponds to the number of the second camera group;

[0080] The first camera and the second camera are of the same type;

[0081] The end detection device comprises a second base, a second support, a third camera, a third light source, a half-reflective half-transmissive lens, a fourth camera group and a fourth light source;

[0082] The second base, the third camera, the third light source, the half-reflective half-transmissive lens, the fourth camera group and the fourth light source are all mounted on the second support;

[0083] The second base is arranged at the top of the second support, and an opening vertically downward clamping claw or clamping sleeve is arranged on the second base, the clamping claw or clamping sleeve can move in the horizontal direction; the third camera, the third light source and the half-reflective half-transmissive lens are all arranged below the second base, the half-reflective half-transmissive lens is arranged at an angle of 45°, the third light source is arranged on the side of the half-reflective half-transmissive lens, and the light reflected on the half-reflective half-transmissive lens is upward, the third camera is arranged at the bottom of the half-reflective half-transmissive lens, and the optical axis is vertically upward, the clamping claw or clamping sleeve on the second base can be moved to a position where the optical axis of the third camera and the central axis are collinear;

[0084] The fourth camera group and the fourth light source are arranged below the second base, the number of the fourth camera group is more than one group, there is more than one fourth camera in each group of the fourth camera group, the optical axis of the fourth camera is upwardly inclined, the angle between the optical axis of the fourth camera and the vertical direction is adjustable, the irradiation direction of the fourth light source is vertically upward, and the clamping claw or clamping sleeve on the second base can be moved to a position where the central axis and the central axis of the fourth light source are collinear.

[0085] The bolt fixing device on the first base is a rotatable structure, or four groups of first camera groups and four groups of second camera groups are arranged along the circumference of the first base, the angle between adjacent two groups of first camera groups is 90°, the angle between adjacent two groups of second camera groups is 90°, and the first camera and the second camera are both area array cameras;

[0086] The clamping claw or clamping sleeve on the second base is a rotatable structure, or four groups of fourth camera groups are arranged along the circumference of the fourth light source, and the angle between adjacent two groups of fourth camera groups is 90°.

[0087] The imaging and illumination method for the outer surface quality detection of the bolt comprises the following steps:

[0088] Workstation 1: vibration queuing feeding:

[0089] The bolt is queued by using a vibration feeder, and is sequentially output one by one to the fixed workstation 1 at the output port of the feeder by using a cylinder push rod or the like, so as to control the position and posture of the detected bolt;

[0090] Workstation 2: bolt outer wall detection:

[0091] 2.1 Bolt vertical section outer wall detection:

[0092] 1) with the first XYZ three-dimensional pneumatic V-shaped clamping jaw, grab the bolt at the first station, move the bolt to the first base, and vertically upward (the screw rod is on the top, and the nut is on the bottom) the bolt is sleeved or clamped on the bolt fixing device of the first base;

[0093] 2) as shown in Figure 1 , the outer side wall of the vertical section (parallel to the axial side) of the bolt includes the screw rod side wall, the bottom side wall of the circular arc transition surface, and the hexagonal nut side wall, as shown in Figure 3 , the first camera in each first camera group has three, respectively opposite the screw rod side wall, the bottom side wall of the circular arc transition surface, and the hexagonal nut side wall, turn on the first parallel light source corresponding to the first camera group, and the parallel light is illuminated to the bolt side wall at an angle of 120-160° relative to the bolt side wall to perform dark field illumination, this illumination method will not produce bright field shining spots in the field of view of the camera, that is, the effect of dark field illumination is produced, and high-quality imaging photos can be obtained, three first cameras, respectively, complete the imaging of the screw rod side wall, the bottom side wall of the circular arc transition surface, and the hexagonal nut side wall, Figure 4 the imaging images of the topmost first camera in different directions can realize clear imaging of the screw rod side wall, and of course other parts outside the screw rod can also be seen in the image, in order to realize clear imaging of each part and improve the accuracy of detection, the bottom side wall of the circular arc transition surface and the hexagonal nut side wall are respectively completed by another two first cameras, and the circular arc transition surface is completed by a second camera;

[0094] The bolt fixing device on the first base is a rotatable structure, which rotates the bolt fixing device and further drives the bolt to rotate 360 degrees with its axis as the rotation axis, if the first camera is a line camera, it performs 360-degree continuous shooting without dead angle, if the first camera is a plane array camera, it takes a photo every 90 degrees of rotation, and then splices the photos taken into a complete bolt side wall outer surface image;

[0095] Or four groups of first camera groups are arranged circumferentially along the first base, the included angle between adjacent two groups of first camera groups is 90°, in order to ensure the imaging effect, each group of first camera groups corresponds to a first parallel light source, and the first camera adopts a plane array camera, which also does not need to rotate the bolt, and four angle photos can be spliced into a complete bolt side wall outer surface image, that is, one shooting can complete the 360-degree non-dead angle imaging of the bolt along the axial direction;

[0096] 2.2 Detection of the outer side wall of the non-vertical section of the bolt:

[0097] As shown in Figure 1 , the side wall of the bolt has a circular arc transition surface, the bottom 2mm or so of the circular arc transition surface is a vertical section, and the rest is an inclined surface with a circular arc transition;

[0098] If the first parallel light source is used for illumination, the image will show over-saturated reflection spots, as shown in Figure 4 , resulting in failure to image defects on the circular-arc transition surface;

[0099] The vertical line of the circular-arc transition surface is determined, as shown in Figure 5 , which is the axis of the second camera, i.e. the shooting angle of the camera. The second parallel light source is used to illuminate the circular-arc transition surface at an angle of 120-160° relative to the circular-arc transition surface, the angle of the second parallel light source is adjusted so that no bright spots are generated in the field of view of the second camera, and the effect image of dark field illumination is produced;

[0100] The acquisition method of the complete side view of the circular-arc transition surface is the same as that of the outer side wall of the vertical section of the bolt in 2.1, and the imaging effect of the circular-arc transition surface is shown in Figure 6 ;

[0101] Station 3: Detection of end face and circular groove side wall

[0102] 3.1 Detection of end face (including bottom surface of circular groove):

[0103] After the shooting task at station 2 is completed, the bolt shank part is clamped by the second XYZ three-dimensional pneumatic V-shaped clamping jaw, moved up and separated from the first base, then moved to the second base position and clamped on the clamping jaw or clamping sleeve on the second base; as shown in Figure 7 , the clamping jaw or clamping sleeve on the second base is an open downward structure, which is convenient for the camera to shoot from the bottom of the end face.

[0104] As shown in Figure 7 , the horizontal position of the clamping jaw or clamping sleeve is adjusted so that the optical axis of the third camera is collinear with the central axis of the bolt, and a 45-degree half-reflective half-transmissive lens is used to achieve flexible illumination of the bolt head and good imaging of all parts of the head. The third light source is diffuse light, Figure 8 , the obtained photo clearly shows the head plane and the defects and dirt on the plane.

[0105] 3.2 Detection of the inner side wall of the circular groove on the end face:

[0106] As shown in Figure 9 , after the end face detection is completed, the clamping jaw or clamping sleeve on the second base is moved to a position where the central axis is collinear with the central axis of the fourth light source, and the fourth light source is diffuse light, which can illuminate the inner side wall of the circular groove; in order to shoot the defects on the inner side wall of the circular groove, the fourth camera is installed at an angle of 60° between the optical axis and the vertical direction, and the imaging effect is shown in Figure 10 , which can clearly shoot the defects on the inner side wall of the circular groove;

[0107] The clamping claw or clamping sleeve on the second base is a rotatable structure. The clamping claw or clamping sleeve is rotated, and the bolt is rotated 360 degrees with the axis as the rotation axis. If the fourth camera is a line camera, 360-degree continuous shooting without dead angle is performed. If the fourth camera is a plane array camera, a photo is taken every 90 degrees, and then the photos are spliced into a complete image of the inner side wall of the circular groove.

[0108] Alternatively, four groups of the fourth camera group are arranged circumferentially around the fourth light source, and the included angle between adjacent two groups is 90°. The fourth camera is a plane array camera. In this way, the bolt is not rotated, and the photos taken at four angles are spliced into a complete image of the inner side wall of the circular groove, that is, one shooting can complete 360-degree imaging of the bolt along the axial direction without dead angle.

[0109] Station 4: blanking and classification

[0110] If the outer surface of the bolt is defect-free, the bolt is moved to the good material groove by the pneumatic clamping claw. If the outer surface of the bolt is defective, the bolt is moved to the bad material groove by the pneumatic clamping claw. The qualified and unqualified bolts are slid into different containers to realize classification. This part of technology refers to mature existing technology.

[0111] The above cameras each adopt a plane array camera with 5120X5120 and 25 million pixels. The digital precision resolution of detection is better than 35 microns / pixel, the detection accuracy is below 0.1 um, the accuracy is above 99.999% within an error range of 2.5 um.

Claims

1. An imaging and illumination method for bolt exterior surface quality detection, characterized in that: It comprises the following steps: 1) When detecting the side wall of the bolt, the side wall of the bolt is illuminated by dark field illumination, and the camera is used to obtain the imaging of the side wall with the optical axis perpendicular to the side wall of the bolt; 2) When detecting the end face of the bolt, the camera is placed on the extension line of the central axis of the bolt, the optical axis of the camera overlaps the central axis of the bolt, a half-mirror is arranged between the end face of the bolt and the camera, a light source is arranged on the side of the half-mirror, and the light emitted by the light source is reflected to the end face of the bolt after being reflected to the half-mirror; If the end face of the bolt is provided with a groove, a divergent light source is used to illuminate the inner side wall of the groove, and the optical axis of the camera and the central axis of the bolt form an angle of 25-45° to shoot the inner side wall of the groove; In step 1), parallel light is irradiated to the side wall of the bolt at an angle of 120-160° relative to the side wall of the bolt for dark field illumination; In step 1), at least one camera with the optical axis perpendicular to the outer side wall of the bolt is added at the position opposite to the bolt after the change of the bolt for each change of the angle of the outer side wall of the bolt; In step 1), when the outer side wall of the bolt is parallel to the axial direction of the bolt, at least one camera with the optical axis perpendicular to the outer side wall of the bolt is added for each change of the diameter of the bolt.

2. The method of imaging and illuminating the exterior surface of a bolt for quality inspection as claimed in claim 1, wherein: In step 1), if the camera is a line array camera, the bolt is rotated 360 degrees with the central axis as the rotation axis to realize 360-degree continuous shooting without dead angle; If the camera is a plane array camera, a photo is taken every 60-120 degrees during the rotation of the bolt with the central axis as the rotation axis, and then the photos are spliced into a complete image of the outer surface of the side wall of the bolt; or, without rotating the bolt, a plane array camera is installed every 60-120 degrees in the circumferential direction, and then the photos are spliced into a complete image of the outer surface of the side wall of the bolt.

3. The method of imaging and illuminating the exterior surface of a bolt for quality inspection as claimed in claim 1 or 2, wherein: In step 2), the half-mirror is inclined at an angle of 45° relative to the central axis of the bolt.

4. The method of imaging and illuminating the exterior surface of a bolt for quality inspection as claimed in claim 1 or 2, wherein: In step 2), when imaging the inner side wall of the groove of the end face of the bolt, if the camera is a line array camera, the bolt is rotated 360 degrees with the central axis as the rotation axis to realize 360-degree continuous shooting without dead angle; If the camera is a plane array camera, a photo is taken every 60-120 degrees during the rotation of the bolt with the central axis as the rotation axis, and then the photos are spliced into a complete image of the inner side wall of the groove; or, without rotating the bolt, a plane array camera is installed every 60-120 degrees in the circumferential direction, and then the photos are spliced into a complete image of the inner side wall of the groove.

5. The imaging and illumination method for detecting the outer surface quality of the bolt according to claim 1 or 2, characterized in that: The bolt comprises a screw rod, a circular arc transition surface and a hexagonal nut which are sequentially connected in the axial direction, the end face of the hexagonal nut is provided with a circular groove, and the inner bottom of the circular groove is provided with a letter; The imaging and illumination device of the above bolt comprises a first XYZ three-dimensional pneumatic V-shaped clamp, a side wall detection device, a second XYZ three-dimensional pneumatic V-shaped clamp and an end detection device which are sequentially arranged in the flowing direction of the production line; The side wall detection device comprises a first base, a first support, a first camera group, a first parallel light source, a second camera group and a second parallel light source; The first base, the first camera group, the first parallel light source, the second camera group and the second parallel light source are all installed on the first support. The first base is arranged at the bottom of the first support, and the first base is provided with a bolt fixing device; The number of the first camera groups is more than one group, each group of the first camera groups has more than three first cameras, the optical axis of the first camera is parallel to the horizontal direction, and the height of the first camera is adjustable; the first parallel light source forms an angle of 120-160° with the vertical direction, the angle of the first parallel light source with the vertical direction is adjustable, the installation height of the first parallel light source in the longitudinal direction is higher than that of the first camera, the number of the first parallel light sources is equal to and corresponds to the number of the first camera groups; The number of the second camera groups is more than one group, each group of the second camera groups has more than one second camera, the optical axis of the second camera is installed in a downward inclined manner, and the angle of the second camera with the vertical direction is adjustable; the irradiation direction of the second parallel light source is inclined from downward to upward, the angle of the second parallel light source with the vertical direction is adjustable, the installation height of the second parallel light source in the longitudinal direction is lower than that of the second camera, and the number of the second parallel light sources is equal to and corresponds to the number of the second camera groups; The first camera and the second camera are of the same type; The end detection device comprises a second base, a second support, a third camera, a third light source, a half-reflective half-transmissive lens, a fourth camera group and a fourth light source; The second base, the third camera, the third light source, the half-reflective half-transmissive lens, the fourth camera group and the fourth light source are all installed on the second support; The second base is arranged at the top of the second support, and the second base is provided with an open vertical downward clamping claw or clamping sleeve, and the clamping claw or clamping sleeve is movable in the horizontal direction; the third camera, the third light source and the half-reflective half-transmissive lens are all arranged below the second base, the half-reflective half-transmissive lens is installed in an inclined manner at an angle of 45°, the third light source is arranged on the side of the half-reflective half-transmissive lens and the light reflected on the half-reflective half-transmissive lens is upward, the third camera is arranged at the bottom of the half-reflective half-transmissive lens and the optical axis is vertically upward, and the clamping claw or clamping sleeve on the second base is movable to a position where the optical axis of the third camera and the central axis are collinear; The fourth camera group and the fourth light source are arranged below the second base, the number of the fourth camera groups is more than one group, each group of the fourth camera groups has more than one fourth camera, the optical axis of the fourth camera is upwardly inclined, the angle of the optical axis of the fourth camera with the vertical direction is adjustable, the irradiation direction of the fourth light source is vertically upward, and the clamping claw or clamping sleeve on the second base is movable to a position where the central axis and the central axis of the fourth light source are collinear.

6. The method of imaging and illuminating of the bolt outer surface quality detection of claim 5, wherein: The bolt fixing device on the first base is a rotatable structure, or four groups of first camera groups and four groups of second camera groups are arranged circumferentially along the first base, the angle between adjacent two groups of first camera groups is 90°, the angle between adjacent two groups of second camera groups is 90°, and the first camera and the second camera are both area array cameras; The clamping claw or clamping sleeve on the second base is a rotatable structure, or four groups of fourth camera groups are arranged circumferentially along the fourth light source, and the angle between adjacent two groups of fourth camera groups is 90°.

7. The method of imaging and illuminating of the bolt outer surface quality detection of claim 6, wherein: The method comprises the following steps: 1) Side wall detection of the bolt: 1.1) Vertical section outer side wall detection of the bolt: A, the outer side wall of the vertical section of the bolt includes the screw rod side wall, the bottom side wall of the circular arc transition surface and the hexagonal nut side wall, the bolt is moved to the first base by the first XYZ three-dimensional pneumatic V-shaped clamp, and the bolt is connected vertically upward on the bolt fixing device; B, the screw rod side wall, the bottom side wall of the circular arc transition surface and the hexagonal nut side wall respectively at least opposite to one of the first camera groups, open the first parallel light source corresponding to the first camera group, the parallel light is irradiated to the bolt side wall at an angle of 120-160° relative to the bolt side wall to perform dark field illumination, and the first camera group respectively completes imaging of the screw rod side wall, the bottom side wall of the circular arc transition surface and the hexagonal nut side wall; C, the bolt fixing device on the first base is a rotatable structure, the bolt fixing device is rotated, and then the bolt is rotated 360 degrees with the axis as the rotation axis, if the first camera is a line camera, 360-degree continuous shooting without dead angle is performed, if the first camera is a plane array camera, a photo is taken every 90 degrees of rotation, and then the taken photos are spliced into a complete bolt side wall outer surface image; Or four groups of first camera groups are arranged along the circumference of the first base, the included angle between adjacent two groups of first camera groups is 90°, each group of first camera groups corresponds to a first parallel light source, and the first camera adopts a plane array camera, and four angle photos are spliced into a complete bolt side wall outer surface image; 1.2) Detection on the non-vertical section outer side wall of the bolt: A, the bottom of the circular arc transition surface is a vertical section, and the rest is an inclined surface in a circular arc transition, that is, the non-vertical section outer side wall of the bolt; the vertical line of the circular arc transition surface is determined, the angle of the second camera is adjusted, the optical axis of the second camera is collinear with the vertical line of the circular arc transition surface, the second parallel light source irradiates to the circular arc transition surface at an angle of 120-160° relative to the circular arc transition surface to perform dark field illumination, the angle of the second parallel light source is adjusted, the bright field shining light spot not in the field of view of the second camera is generated, the effect image of dark field illumination is manufactured, and the imaging of the circular arc transition surface is completed; B, the bolt fixing device on the first base is a rotatable structure, the bolt fixing device is rotated, and then the bolt is rotated 360 degrees with the axis as the rotation axis, if the second camera is a line camera, 360-degree continuous shooting without dead angle is performed, if the second camera is a plane array camera, a photo is taken every 90 degrees of rotation, and then the taken photos are spliced into a complete bolt side wall outer surface image; Or four groups of first camera groups are arranged along the circumference of the first base, the included angle between adjacent two groups of first camera groups is 90°, each group of first camera groups corresponds to a first parallel light source, and the first camera adopts a plane array camera, and four angle photos are spliced into a complete bolt side wall outer surface image; 2) Detection on the bolt end face and the circular groove side wall: 2.1) Detection on the bolt end face: A, the bolt end face includes the bolt end face periphery and the bottom surface of the circular groove, after the bolt side wall is shot, the screw rod part of the bolt is clamped by the second XYZ three-dimensional pneumatic V-shaped clamp, is moved upward and is separated from the first base, then is moved to the second base position, and is clamped on the clamping jaw or the clamping sleeve on the second base; B. Adjust the horizontal position of the clamping jaw or clamping sleeve so that the optical axis of the third camera is collinear with the central axis of the bolt, the third light source is diffuse light, and flexible illumination of the bolt head is achieved with the help of a 45-degree half-reflective half-transmissive lens. The third camera completes the imaging of the end face of the bolt; 2.2) Detection of the inner side wall of the circular groove on the end face: A. After completing the end face detection, move the clamping jaw or clamping sleeve on the second base to a position where the central axis is collinear with the central axis of the fourth light source. The fourth light source is diffuse light, illuminating the inner side wall of the circular groove. Adjust the tilt angle of the fourth camera to obtain the imaging of the inner side wall of the circular groove; B. The clamping jaw or clamping sleeve on the second base is a rotatable structure. Rotate the clamping jaw or clamping sleeve, and then rotate the bolt with its axis as the rotation axis by 360 degrees. If the fourth camera is a line camera, take continuous photos without dead angles by 360 degrees. If the fourth camera is a surface array camera, take a photo every 90 degrees, and then splice the photos to obtain the complete image of the inner side wall of the circular groove. Alternatively, four groups of fourth camera assemblies are arranged circumferentially around the fourth light source, and the included angle between adjacent two groups is 90°. The fourth cameras all adopt surface array cameras. In this way, the bolt does not need to be rotated, and the photos taken at four angles are spliced to obtain the complete image of the inner side wall of the circular groove.

Images