Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
  • G01N21/956—Inspecting patterns on the surface of objects
  • G01N21/95607—Inspecting patterns on the surface of objects using a comparative method
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
  • G01N21/956—Inspecting patterns on the surface of objects
  • G01N21/95684—Patterns showing highly reflecting parts, e.g. metallic elements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
  • G01N21/956—Inspecting patterns on the surface of objects
  • G01N21/95607—Inspecting patterns on the surface of objects using a comparative method
  • G01N2021/95615—Inspecting patterns on the surface of objects using a comparative method with stored comparision signal
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
  • G01N21/84—Systems specially adapted for particular applications
  • G01N21/88—Investigating the presence of flaws or contamination
  • G01N21/95—Investigating the presence of flaws or contamination characterised by the material or shape of the object to be examined
  • G01N21/956—Inspecting patterns on the surface of objects
  • G01N2021/95638—Inspecting patterns on the surface of objects for PCB's

Definitions

• the present invention generally relates to optical inspection systems and, more particularly, to three-dimensional image determination systems intended for online analysis of objects, in particular electronic circuits. Presentation of the prior art
• Optical inspection systems are generally used to check the condition of an object before it is placed on the market. In particular, they make it possible to determine a three-dimensional image of the object that can be analyzed for possible defects.
• the three-dimensional image of the electronic circuit can be used in particular to inspect the good state of the welds of the electronic components on the printed circuit.
• the object to be inspected is moved to an inspection position by via a conveyor.
• At least one position sensor is used to detect that the object is in the inspection position so as to control the stopping of the conveyor.
• the position sensor may be of the mechanical type, magnetic or projecting a light beam.
• the sensor may comprise a cell emitting a light beam which is interrupted or reflected by the object to be inspected when it reaches the inspection position.
• the position detected by the position sensor may not be correct.
• the materials composing the object to be inspected can disturb the operation of the position sensor.
• the object to be inspected is an electronic circuit, in particular a printed circuit, for which reflective metal materials, opaque materials or partially transparent materials may be present on the surface.
• the object to be inspected may have an irregular shape in the region that is detected by the position sensor.
• the object to be inspected is an electronic circuit, in particular a printed circuit, for which the edge of the circuit may locally have a significant change of shape, for example a cut, at the level of the zone which is detected by the position sensor.
• the position of the edge detected by the position sensor can vary from one electronic circuit to the other.
• One possibility is, taking into account the object to be inspected, to move the position sensor to a location at which safer position measurements can be made.
• the displacement of the position sensor increases the duration of implementation of the optical inspection process. This is not desirable particularly when the optical inspection method is used for small series.
• access to the position sensor can be difficult.
• An object of an embodiment is to overcome all or part of the disadvantages of optical inspection systems comprising a device for detecting the position of an object to be inspected described above.
• Another object of an embodiment is that the operation of the device for detecting the position of an object to be inspected is not disturbed by the nature of the materials on the surface of the object.
• Another object of an embodiment is that the operation of the device for detecting the position of an object to be inspected is not disturbed by the shape of the object.
• optical inspection system is adapted to correct the position detected by a mechanical position sensor, magnetic or projecting light radiation.
• optical inspection system does not include a mechanical position sensor, magnetic or projecting light radiation.
• an embodiment provides a method of optical inspection of an electronic circuit comprising the acquisition of images of the electronic circuit by image sensors, the use of the images for determining the difference between the position of the electronic circuit and an inspection position and the use of said images in at least one other step of the method.
• the method comprises modifying the position of the electronic circuit when said difference is greater than a threshold.
• the method comprises comparing, for each image sensor among some of the image sensors, the image acquired by the image sensor with at least one reference image. According to one embodiment, the method comprises comparing, for each image sensor among some of the image sensors, the acquired image with at least one additional reference image obtained from the reference image.
• the method comprises comparing, for each image sensor among some of the image sensors, the image acquired by the image sensor with a first reference image and with a second reference image. obtained by blurring the first reference image.
• the method comprises comparing, for each image sensor among some of the image sensors, the image acquired by the image sensor with a third reference image obtained by contour extraction from the image sensor. first reference image.
• the method comprises comparing, for each image sensor among some of the image sensors, the image acquired by the image sensor with a fourth reference image obtained by blurring the third image. reference.
• the image sensors are moved in a first direction relative to the electronic circuit at least a first location in the first direction to acquire images of a first portion of the electronic circuit to a second location in the first direction for acquiring images of a second portion of the electronic circuit, the electronic circuit being moved to a first position when the image sensors are at the first location and at a second, different position from the first position, when the image sensors are in the second location, or the image sensors being moved in a second direction, not parallel to the first direction, to a third position in the second direction when the image sensors are at the first location in the first direction and at a fourth position in the second direction, dif the third position, when the image sensors are at the second location in the first direction.
• the first portion of the electronic circuit is in the sharpening zone of the image sensors when the electronic circuit is in the first position or when the image sensors are in the third position
• the second portion of the The electronic circuit is in the sharpness zone of the image sensors when the electronic circuit is in the second position or when the image sensors are in the fourth position.
• At least two parts of the electronic circuit are based on two supports and the other step comprises modifying the position of each support, independently of one another.
• the electronic circuit comprises a printed circuit, each support supporting a lateral edge of the printed circuit.
• a conveyor transports the electronic circuit in a conveying direction of the electronic circuit, the supports extending parallel to the conveying direction of the electronic circuit.
• a displacement device transports the image sensors in a direction of displacement of the image sensors, not parallel to the conveying direction of the electronic circuit, in particular perpendicular to the conveying direction of the electronic circuit.
• each support is moved, independently of one another, in a direction of support displacement, not parallel to the conveying direction of the electronic circuit and to the direction of movement of the image sensors, in particular perpendicular to the conveying direction of the electronic circuit and to the direction of movement of the image sensors.
• Figures 1, 2 and 3 are respectively a perspective view, a top view and a side view, partial and schematic, of an embodiment of an optical inspection system
• FIG. 4 illustrates, in the form of a block diagram, an embodiment of a method of optical inspection of an electronic circuit.
• Figures 1, 2 and 3 show, very schematically, a system 10 for optical inspection of an electronic circuit Card.
• the term "electronic circuit” is understood to mean either a set of electronic components interconnected via a support, the only support used to make this interconnection without the electronic components or the support without the electronic components but provided with means for fixing the electronic components.
• the support is a printed circuit and the electronic components are fixed to the printed circuit by solder joints obtained by heating soldering paste blocks.
• the term "electronic circuit” means the printed circuit alone (without electronic components or soldering paste blocks), the printed circuit provided with solder paste blocks and without electronic components, the printed circuit fitted with the dough blocks welding and electronic components before the heating operation or the printed circuit provided with electronic components attached to the printed circuit by solder joints.
• the dimensions of the circuit Card correspond, for example, to a rectangular card having a length and a width ranging from 50 mm to 550 mm.
• the electronic circuit Card to be inspected is placed on a conveyor 12, for example a planar conveyor, not shown in FIG. 3.
• the conveyor 12 is capable of moving the Card circuit in a direction X, for example a horizontal direction, by a position introducing the circuit to an inspection position and the inspection position to a recovery position of the circuit.
• the conveyor 12 may comprise a set of belts and rollers driven by a rotating electric motor, not shown.
• the conveyor 12 may comprise a linear motor moving a carriage on which rests the electronic circuit Card.
• the optical inspection system 10 comprises an image projection device on the card circuit comprising projectors P, two aligned projectors being, by way of example, diagrammatically represented in FIGS. 1 and 2.
• the system 10 further comprises: , an image acquisition device comprising image sensors or digital cameras C.
• an image acquisition device comprising image sensors or digital cameras C.
• eight cameras are shown schematically in FIGS. 1 and 2, aligned along two rows of cameras on either side of the camera.
• the row of floodlights P and each projector P is placed substantially in the center of a rectangle each corner of which is occupied by a camera C.
• the assembly comprising the projectors P and the cameras C, hereinafter referred to as camera-projector unit 14, can be moved by a device 15, shown only in Figures 2 and 3, in a direction Y, for example a horizontal direction, perpendicular to the direction X.
• a direction Y for example a horizontal direction, perpendicular to the direction X.
• a dashed line 14 ' the block camera projectors to another position along the Y direction.
• the optical inspection system 10 makes it possible to determine a three-dimensional image of the electronic circuit card.
• a three-dimensional image, or 3D image is a cloud of points, for example several million points, of at least a part of the outer surface of the circuit in which each point of the surface is marked by its coordinates determined relative to a three-dimensional space marker.
• a two-dimensional image, or 2D image is a digital image acquired by one of the cameras C and corresponding to a matrix of pixels.
• the term image refers to a two-dimensional image.
• the field of view of the camera-projector unit 14 is the real-space portion captured by the cameras C during the acquisition of images and enabling the determination of a three-dimensional image.
• the cameras C and the projectors P are connected to a computer system 16 adapted in particular to perform an image processing.
• the processing system 16 may comprise a computer or a microcontroller comprising a processor and memories of different types including a non-volatile memory in which are stored instructions whose execution by the processor allows the processing system 16 to perform the desired functions .
• the system 16 may correspond to a dedicated electronic circuit or to a combination several different technology processing modules.
• the processing system 16 is adapted to determine a three-dimensional image of the card circuit by image projection, including for example fringes, on the circuit card to be inspected.
• the processing system 16 is further adapted to control the conveyor 12 and the conveyor 15.
• the optical inspection system 10 comprises at least one sensor S of the position of the circuit Card.
• the position sensor S can be of the mechanical type, magnetic or projecting a light beam.
• the position sensor S can be connected to the processing system 16.
• the detection of the position of the circuit Card by the sensor S can cause the control of the stop of the conveyor 12 by the processing system 16.
• the optical inspection system 10 comprises first and second position sensors arranged so that when the card circuit is moved in the X direction, it is detected by the first position sensor and then by the second position sensor.
• the detection of the circuit Card by the first sensor causes the control by the processing system 16 of a slowing of the conveyor 12 and the detection of the circuit Card by the second sensor causes the control system 16 to stop the conveyor 12.
• the dimensions of the circuit Card are generally higher than the visual field of the cameras C.
• the determination of a three-dimensional image of the entire circuit Card is then obtained by bringing the camera-projector unit 14 in the direction Y to several fixed positions relative to the Card circuit, images being acquired by the cameras C at each position of the camera-projector block 14. These positions are hereinafter referred to as image acquisition positions.
• image acquisition positions can be chosen so that the portion of the circuit Card in the field of view of the cameras C at an image acquisition position covers as little as possible the portion of the circuit Card in the field of view of the cameras C at the next image acquisition position.
• the reference Cardj denotes the portion of the electronic circuit Card whose three-dimensional image can be determined by the processing system 16 from the images acquired by the cameras C for a given image acquisition position of the camera-projector unit. .
• Each circuit portion Card 1 comprises an initial edge BI 1, the leftmost edge in FIG. 2, and a final edge BF 1, the most right in Figure 2.
• the image acquisition positions are chosen in order that the overlap between the circuit portion Cardj_ in the field of view of the camera-projector unit 14 at an image acquisition position and the circuit portion Cardj__
• the final edge BF-j_ of the circuit portion Cardj_ substantially corresponds to the initial edge BI-j_ +] _ of the circuit portion Cardj__
• the two-dimensional images acquired by the cameras C must not be blurred.
• the circuit card must therefore be placed in the area of sharpness of the cameras C.
• the card circuit is brought by the conveyor 12 at a reference plane] REF whose position relative to the cameras C is known so that, if the card circuit is perfectly flat, it is in the area of sharpness of the cameras C.
• the card circuit may not be flat.
• the Card circuit is shown in FIG. 3 with a generally curved downward shape which is exaggerated for purposes of illustration.
• the deformations of the card circuit may not be regular in the Y direction.
• the card circuit may comprise curved portions upwards and curved portions. down. Nevertheless, in the case of a warp, the deformations are generally substantially independent of the X direction.
• the deformations measured in a Z direction perpendicular to the X and Y directions are generally less than a few millimeters.
• the optical inspection system 10 comprises a device 20, shown in FIG. 3, for moving the card circuit to bring the card circuit, at each image acquisition position, into the sharpness zone of the cameras C.
• the device 20 may have the structure described in patent application WO2014 / 167248.
• the device 20 is adapted to move the card circuit closer to or away from the camera-projector unit 14.
• the device 20 is adapted to independently move two distinct parts of the card circuit, each in the Z direction. for example, the Z direction is the vertical direction.
• the device 20 comprises two supports 22, 24, represented in FIG. 3, which extend substantially in the direction X.
• the support 22 comprises an upper end 23 which can bear against an edge lateral 26 of the card circuit and the support 24 comprises an upper end 25 which can bear against the opposite side edge 28 of the card circuit.
• the ends 23 and 25 may contain belts, not shown, for conveying the electronic circuits.
• each end 23, 25 comprises a flat portion which extends over a portion of the width of the card circuit, in the direction X.
• a band of the conveyor 12, not shown in FIG. 3 can be sandwiched between the edge 26 of the Card circuit and the support 22 or between the edge 28 of the Card circuit and the support 24 when the supports 22, 24 are brought in abutment against the edges 26, 28 of the Card circuit.
• the device 20 is adapted to change the height Z ] _ of the top of the support 22 and the height Z2 of the top of the support 24 independently of one another.
• the device 20 comprises two actuators 30, 32, for example rotary electric motors step by step, each rotating each cam 34, 36 about an axis parallel to the direction Y.
• Each cam 34, 36 is, for example, an outer profile cam on which rests a portion of the support 22, 24 associated.
• the height Z ] _ depends on the angular position of the cam 34 and the height Z2 depends on the angular position of the cam 36.
• the actuators 30, 32 are controlled by the processing system 16.
• linear actuators which directly move the supports 22, 24 in the direction Z can be used.
• the device 20 further comprises a device 28 for locking the edge 26 of the card circuit on the support 22 and a device 40 for locking the edge 28 on the support 24.
• Each locking device 38, 40 follows the movement of the support 20
• the locking devices 38, 40 are controlled by the processing system 16 to hold the edges 26, 28 of the card circuit against the supports 22, 24 after the card circuit has been moved according to the direction of rotation. the direction X to the position where the acquisitions of images are made.
• each blocking device 38, 40 corresponds to to a clamp actuated by an actuator controlled by the treatment system 16.
• the processing system 16 is adapted to determine the difference ⁇ in the X direction between the real position XI of the Card circuit and the desired inspection position XO from the images acquired by the cameras C. Card circuit position can then be changed in direction X when the actual position of the circuit Card deviates too much from the desired inspection position XO and / or corrections can be made during the implementation of the subsequent steps of the method. optical inspection to take into account the difference ⁇ determined.
• the images used to determine the positional deviation of the card circuit are images that are used at another stage of the optical inspection process.
• the images used to determine the positional deviation of the Card circuit are images that are acquired in one of the first steps of the optical inspection process. Therefore, if the position of the Card circuit in the X direction is to be changed, the number of steps of the optical inspection process that must be performed again is reduced.
• the processing system 16 is adapted to determine the position of the Card circuit in the X direction from the images acquired by the cameras C during a movement operation of the Card circuit in the Z direction to bring the Card circuit in the sharpness area of C cameras.
• the images used for the determination of the positional deviation of the circuit Card are images acquired by a part of the cameras C, called active group thereafter.
• the active group comprises a number of cameras C strictly less than the total number of cameras C.
• the active group comprises for example from two to eight cameras, for example four cameras.
• the cameras of the active group are determined before the implementation of the method by an analysis of the expected images for each camera.
• Fig. 4 shows, in the form of a block diagram, an embodiment of an optical inspection method of the Card circuit.
• step 50 the circuit Card is moved by the conveyor 12 to an initial inspection position which is, for example, obtained by the detection of the circuit Card by the position sensor S.
• step 50 may not include any movement of the circuit card by the conveyor 12. The method continues in step 51.
• the first process includes steps 51, 52, 53, 54 and 55.
• the second process includes step 51 and steps 56, 57, 58, 59.
• step 51 the processing system 16 controls the acquisition of two-dimensional images of the circuit portion Card 1 by the cameras C of the camera-projector block 14. These are the same images acquired in step 51 which are used. by the first and second process. For the first process, the process continues in step 52 while for the second process, the process proceeds to step 56.
• step 52 of the first process the processing system 16 determines whether the method of correcting the position of the Card circuit in the X direction is to be implemented. If this is the case, the method continues in step 53.
• the method for correcting the position of the circuit card in the X direction may be implemented only at the first acquisition of images following the introduction of the Card circuit in the optical inspection system 10.
• the processing system 16 determines the deviation ⁇ from the analysis of the two-dimensional images of the first circuit portion Card . acquired by the cameras of the active group in step 51.
• the image acquired by each camera C of the active group is compared with at least one reference image for the camera in question.
• the processing system 16 includes a memory in which the reference images are stored.
• the reference image may correspond to the image, in color or grayscale, that would be acquired by the camera C under specific lighting conditions if the card circuit was in the position desired inspection.
• the reference image is thus an image representing at least a portion of the circuit Card in the desired inspection position.
• the reference image does not correspond to a pattern, that is to an image comprising predetermined geometric shapes and which is generally used for a calibration operation of a camera.
• the reference image covers a portion of the card circuit larger than that actually obtained with the camera C.
• the reference image may be the same for several cameras C of the active group when it covers a part of the card circuit which contains the images to be acquired by these C cameras.
• a pretreatment of the image acquired by the camera C can be implemented in order to allow the comparison of the image acquired by the camera C with the reference image.
• the image acquired by the camera C is an image that is used at a later stage for the determination of a 3D image of the card circuit.
• the image can be acquired by the camera C while fringes are projected on the circuit card to be inspected.
• the pretreatment may then include filtering the acquired image to obtain a gray-scale image corresponding to the image that would be acquired by the camera C in the absence of projections of the fringes.
• the processing system 16 determines the normalized cross correlation product (NCC) in the X direction between the acquired image and the reference image.
• the correlation product is a function which depends on the position in the X direction of the acquired image and which has a peak when the acquired image is at a position at which it is superimposed best on the reference image.
• the processing system 16 may further determine a global function from the normalized correlation products determined for the cameras of the active group.
• the processing system 16 determines M standardized correlation products NCCj, j being an integer varying from 1 to M. The processing system 16 then determines the function F from the normalized M correlation products NCCj which depends on the position in the X direction of the acquired images. The position of the maximum of the function F indicates the difference ⁇ between the actual position XI of the circuit Card and the desired inspection position X0.
• the function F can be given by the following relation (1):
• the acquired image is compared to more than one reference image.
• a second reference image may correspond to the first reference image described above to which a blur process has been applied.
• a third reference image may correspond to the first reference image to which contour extraction processing has been applied.
• the edge extraction processing is applied to the acquired image and the image thus modified is compared with the third reference image.
• a fourth reference image may correspond to the third reference image described above to which a blur process has been applied.
• the method may comprise the determination for each reference image of the deviation ⁇ , for example as previously described and the determination of an average deviation AX mQ y from the deviations ⁇ , for example by determining the mean of the deviations ⁇ .
• the difference ⁇ can be determined by using the function F described above with all the reference images. The process continues in step 54.
• step 54 of the first process the processing system 16 determines whether correction of the position of the circuit Card is to be implemented. According to one embodiment, the processing system 16 compares the difference ⁇ determined in step 53 with a threshold. If the difference ⁇ is greater than the threshold, the method continues in step 55.
• step 55 of the first process the processing system 16 controls the conveyor 12 to move the Card circuit in the X direction of the difference ⁇ .
• the process continues in step 51 for the first process.
• step 54 If, in step 54, the difference ⁇ is below the threshold, the card circuit is not displaced. However, the processing system 16 can correct the position of the pixels of the images acquired by the cameras C by the difference ⁇ at the subsequent steps of the method. The first process is complete and the process continues in step 60.
• step 52 the processing system 16 determines that the method of correcting the position of the circuit Card is not to be implemented, the first process is completed and the method continues in step 60.
• step 56 of the second process the processing system 16 determines whether the circuit portion Card i appears sharply on the three-dimensional images acquired by the cameras C by analysis of the three-dimensional images acquired in step 51 or by the analysis. of a three-dimensional image determined from the three-dimensional images acquired by the cameras C.
• the processing system 16 is adapted to determine whether the circuit portion Cardj_ is found, in part or in full, in the area of sharpness of the cameras C, before the first net plane of the cameras C or after the last net plane of the cameras C.
• the three-dimensional image determined possibly in step 56 may not be as accurate as a three-dimensional image determined at a later stage of the process Optical inspection and used for fault finding of the Card circuit.
• the process continues at step 57.
• step 57 the processing system 16 determines whether the sharpness of the three-dimensional images acquired by the cameras C or to be acquired by the cameras C is sufficient for the determination of a three-dimensional image at the desired precision. If all or part of the Card I portion does not appear clearly on the pictures acquired or to be acquired by the C cameras, the process proceeds to step 58.
• step 58 the processing system 16 determines the heights Z 1 and Z 2 to be provided so that the whole of the circuit portion Card 1 clearly appears on the images acquired or to be acquired by the cameras C.
• the first circuit portion Card 1 is close to the edge 26 whose position is known. Indeed, the edge 26 is initially maintained in the reference plane PREF which is part of the sharpness zone of the cameras C.
• the height Z2 is modified so that the final edge BF ] _ of the circuit portion Card
• the new value of the height Z2 is, for example, determined from the position of the edge BF ] with respect to the PREF plane determined by analysis of the measurements of the range finder. acquired by the image acquisition devices other than the cameras C, images acquired by the cameras C and / or when determining the 3D image of the circuit portion Card 1.
• the edge BI-j is located in the plane PREF OR at least in the sharpness zone of the cameras C following the settings of the heights Z 1 and Z2 to the previous cycle.
• the heights Z] _ and Z2 are changed to the initial edge BIj_ be maintained in the reference plane PREF e t 3 ⁇ 4 EU I.sub.E final edge BF-j_ is returned to the reference plane PREF- -New values of the heights Z 1 and Z 2 are determined from the position of the edge BF 1 with respect to the PREF plane determined by analysis of the measurements of the range finder, images acquired by the image acquisition devices other than the cameras C , images acquired by the cameras C and / or when determining the 3D image of the circuit portion Cardj_.
• the process continues at step 59.
• step 59 the actuators 30 and 32 are implemented by the processing system 16 to bring the vertices of the supports 22 and 24 respectively to the heights Z] _ and Z2. The process continues in step 51.
• step 57 if all of the first portion Card1 appears sharply on the images acquired or to be acquired by the cameras C, the second process is completed and the process proceeds to step 60.
• step 60 it is expected that the first and second processes will be completed.
• step 61 the process continues in step 61.
• step 61 two-dimensional images of the first circuit portion Card 1 are acquired by the cameras C of the camera-projector block 14 and the processing system 16 determines a three-dimensional image of the first circuit portion Card 1.
• steps 51 and / or 56 two-dimensional images have already been acquired by the cameras C and a three-dimensional image has already been determined, step 61 can not not be present.
• step 51 three-dimensional images have already been acquired by the cameras C but there has been no determination of a three-dimensional image
• the three-dimensional image can be determined in step 61 to from the images acquired in step 51.
• new images are acquired independently of the images acquired in previous steps.
• the acquired images may include color images and grayscale images for the purpose of determining a three-dimensional image.
• the third process includes steps 62 and 63.
• the fourth process includes step 64.
• the fifth process includes step 65.
• step 62 of the third process the processing system 16 determines the new values of the heights Z 1 and Z 2 so that the whole of the circuit portion Card 1 _ +] _ appears in a clear manner on the images that will be acquired by them. C cameras at the next position of the camera-projector unit 14.
• the edge BI 1 is substantially in the plane PR 2 F OR at least in the sharpness zone of the cameras C following the adjustments of the heights Z 1 and 2 to the cycle previous.
• the Z] _ Z2 and heights may be modified so that the initial edge BI-j_ +] _ of the portion Cardj + _] _, which substantially corresponds to the final edge BF-j_ of the circuit portion Cardj ⁇ be maintained in the reference plane
• the new values heights Z 1 and Z 2 can be determined by extrapolation from the general shape of the portion Card 1, for example by considering that the circuit portion Card 1 + has substantially the same shape as the circuit portion Card i, taking account of the evolution of the curvature of the previous circuit portions Card 1, Card 1, Card 2 , ⁇ , taking into account the profiles of the identical electronic circuits previously measured or by instantaneous measurement of the profile of the Cardj_ circuit potion to be inspected, or by combination of these solutions.
• the processing system 16 determines the new values of the heights Z] _ and Z2 so that all of the new Card circuit portion ] of the Card circuit which will be obtained after displacement of the Card circuit in the X direction clearly appears on the images that will be acquired by the cameras C at the next position of the camera-projector unit 14. The process continues at step 63.
• step 63 of the third process the actuators 30 and 32 are controlled by the processing system 16 for moving the supports 22 and 24 to the new values of heights, respectively Z] _ and Z2.
• the third process is then completed and the process continues in step 66.
• step 64 of the fourth process the block cameras projectors 14 is moved to the next position along the Y direction for determining one three dimensional image of the circuit portion Cardj_ +] _.
• the camera-projector unit 14 is moved in the Y direction for the determination of the three-dimensional image of the new image.
• circuit portion Card ] _ of the Card circuit which will be obtained after displacement of the Card circuit in direction X. The fourth process is then completed and the process continues in step
• steps 62 and 63 are not present.
• step 65 of the fifth process a method of optical inspection of the circuit portion Card I can be implemented, for example from a three-dimensional image analysis of the circuit portion Card I, for a search. of defects in the circuit portion Cardj_.
• the process proceeds to step 66.
• step 66 it is expected that the third, fourth and fifth processes will be completed.
• the process proceeds to step 50 for optical inspection of another portion of the Card circuit.
• the optical inspection system 10 comprises at least one sensor S for controlling the stopping of the conveyor 12 and the steps 51, 52, 53, 54 and 55 described previously are carried out while the card circuit is stopped.
• the steps 51, 52 and 53 are implemented while the conveyor 12 is moving the Card circuit.
• the processing system 16 can control the conveyor 12 to slow down and stop the card circuit at the desired inspection position X0.
• the optical inspection system 10 may then advantageously not include a mechanical, magnetic, or light-beam position sensor for controlling the stopping of the conveyor 12.
• step 59 can to be achieved by moving the camera-projector unit 14 in the Z direction, the electronic circuit Card not being moved in the Z direction.
• the images acquired by the cameras of the active group and used to determine the positional difference ⁇ of the card circuit are images used to bring the circuit into the sharpness zone.
• the images used for determining the positional deviation ⁇ of the card circuit may be images acquired at another stage of the optical inspection process.
• the images acquired by the cameras and used for determining the positional difference ⁇ of the card circuit are images used for the determination of the three-dimensional image of the card circuit in step 61 described above.

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