IT202100031832A1 - APPARATUS FOR ACQUISITION OF THREE-DIMENSIONAL INFORMATION OF OBJECTS AND SURFACES FOR AN ARTIFICIAL VISION SYSTEM FOR THE AUTOMATIC OPTICAL INSPECTION OF THE VISUAL QUALITY OF AN UNDERLYING OBJECT, IN PARTICULAR ELECTRONIC ASSEMBLIES, ELECTRONIC BOARDS AND THE SIMILAR - Google Patents

Description

DESCRIPTION

The present invention refers to an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for the automatic optical inspection of objects, in particular, but not limited to, electronic assemblies, electronic boards and the like.

? I know that artificial vision systems for quality inspection? visual are widely applied in the high-volume manufacturing industry, semiconductor industry, food and pharmaceutical industries and are based on standard image processing and computer vision techniques such as, but not limited to, edge detection, connected component analysis, texture analysis and projective geometry .

These approaches are simple and very effective when ? Is it necessary to perform quantitative measurements of entities? well defined (such as lengths, heights, colors, fine grain patterns); once the measurements are completed, ? It is possible to use simple tools based on pre-established rules to evaluate whether an observed product meets the acceptance criteria or not.

In particular, in this field, the expression "Automatic Optical Inspection" (AOI) generally refers to an automated visual quality inspection system. objects (which can consist of electronic assemblies, such as printed circuits, i.e. PCBs and Surface Mount Technology, i.e. SMT) in which a camera autonomously scans the object under test.

In particular, in the case of electronic assemblies, the camera allows you to identify both manufacturing defects (e.g. missing components) and quality defects? (e.g. size or shape of the fitting or inclination of the component). AOIs are commonly used in manufacturing processes because? they are non-contact testing and inspection methods; AOIs are implemented in many stages of the manufacturing process, including bare panel inspection, solder paste inspection (SPI), pre-reflow and post-reflow, and other stages.

As ? known, substantially all automatic optical inspection systems require projecting a light, or one or more? light patterns, on the object to be inspected and to acquire the light reflected by the object via a digital sensor; the acquired images are analyzed by a unit? processing configured to determine the physical and/or geometric characteristics of the object to be inspected based on the light acquired by the sensor.

Nowadays, in the field of visual quality inspection systems? automation for electronic assemblies, there is? a growing need? to acquire coordinated measurements online.

Since? the complexity? of today's electronic boards? increasing with more? components, more? joints, greater density? and new packaging technologies such as microchips of size 01005 and even size 008004, two-dimensional automatic optical inspection technology uses grayscale image analysis or the camera view of the corners of color images may no longer be? a valid option.

To overcome these limitations, three-dimensional scanning technology is been effectively combined with the AOI and ? now used for many applications such as inspection of microelectronics and solder paste deposits below 100 microns and other demanding applications.

AND? furthermore, I note that, although functional, these known systems have limitations and have some disadvantages and limitations.

In particular, some limitations arise from the nature of the measurement technique, while others are more particularly related to the measurement of electronic assemblies (SMT and PCB) and include:

- difficulties? in ensuring complete measurement of low components near high components due to the shadow effect (if the reference frame is projected at an angle, high features may cast a shadow, preventing measurement of nearby low features);

- difficulties? in avoiding measurement errors caused by multiple reflections between components (multiple specular reflections between shiny elements, such as solder joints, tinned wires and metal oscillators, can cause distortions in the fringe pattern and errors in height measurements);

- difficulties? in ensuring fast, highly accurate and repeatable measurements in the micrometer (pm) range in all directions.

A further difficulty? ? given by the complexity? physical and overall dimensions of the components of the image acquisition systems of known systems, which require relatively large dimensions for the complete inspection system and to guarantee mutual non-interference of the different components. Is there therefore a need to improve the structure of artificial vision systems for quality inspection? visual notes.

The technical task proposed by the present invention is, therefore, to create an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection. visual that allows to eliminate the technical drawbacks complained of of the known art.

In the context of this technical task, one purpose of the invention is? is to create an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? visual that is simple and effective.

Another purpose of the invention? is to create an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? visual that is compact in size.

Not the least purpose of the invention? is to create an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? visual that can guarantee fast, highly accurate and repeatable measurements.

The technical task, as well as? These and other purposes, according to the present invention, are achieved by creating an apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection. view of an underlying object, comprising a first camera having a vertical optical axis Z and a first flat sensor having orthogonal axes X,Y lying in a horizontal plane and a second camera having a horizontal optical axis X? and a second flat sensor having orthogonal axes Y?, Z? lying in a vertical plane, a system of illumination from above the object comprising a plurality? of light projectors, an optic of the first and second cameras comprising a double lens optical assembly having a first vertical optical arm associated with said first camera and coaxial to said vertical optical axis Z and a second horizontal optical arm associated with said second camera and coaxial to said horizontal optical axis where the light projectors are angularly spaced around the vertical optical axis Z of said first camera, and where said horizontal optical arm of said optical group is? positioned with a first angle a of offset from an X axis of said first sensor of said first camera.

Light projectors may include structured or unstructured light sources.

The headlight assembly preferably but not necessarily? a telecentric or bi-telecentric optical unit.

In one embodiment, one of the first and second cameras ? preferably a high resolution camera.

In one embodiment, one of the first and second cameras ? a camera capable of acquiring images containing information relating to the polarization of the light incident on the sensor.

In one embodiment, a Z-axis? of the second sensor of the second camera? oriented with a second offset angle? with respect to a vertical axis parallel to said Z axis, uniquely determined by the value of said first offset angle a to guarantee the alignment of the acquisition areas of the first and second cameras.

In one embodiment, the light projectors are positioned with a vertical projection axis.

In one embodiment, the light projectors are positioned with an inclined projection axis.

In one form of execution, a plurality? of mirrored reflectors? interposed between the plurality? of light projectors and an object station for converting the optical path of light from the projectors to the object.

In one embodiment, a series of monochromatic or polychromatic light-emitting rings coaxial to the vertical optical axis of the first camera with decreasing diameter and decreasing distance from the first camera are included.

Other characteristics of the present invention are also defined in the subsequent claims.

Further characteristics and advantages of the invention will be more evident from the description of a first preferred but not exclusive embodiment of the apparatus according to the invention, illustrated for indicative and non-limiting purposes in the attached drawings, in which:

figure 1 shows a schematic elevation view of the apparatus in a first embodiment;

figure 2 shows a schematic plan view of the apparatus in a first embodiment;

figure 3 shows a schematic elevation view of the apparatus in a second embodiment;

figure 4 shows a schematic plan view of the apparatus in a second embodiment.

The following detailed description refers to the attached drawings, which form part of it.

In drawings, similar reference numerals typically identify similar components, unless the context indicates otherwise.

The illustrative embodiments described in the detailed description and drawings are not intended to be limiting.

Other embodiments may be used, and other modifications may be made without departing from the spirit or scope of the subject matter represented herein.

Aspects of the present disclosure, as generally described herein and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety. of different configurations, all of which are explicitly contemplated and are part of this description.

With reference to the figures cited, an apparatus for acquiring three-dimensional information of objects and surfaces is shown for an artificial vision system for automatic optical quality inspection. view of an underlying object indicated overall with the reference number 1.

The apparatus 1 includes a first camera 10 typically positioned in an upper position having a vertical optical axis Z and a first flat sensor 110 having orthogonal axes X,Y lying in a horizontal plane. The apparatus 1 further comprises a second camera 20 having a horizontal optical axis and a second flat sensor 120 having orthogonal axes Y?, ?? lying in a vertical plane.

The apparatus comprises a double-lens optical assembly 55, comprising one or more? lenses and possibly other optical elements, which acts as optics for both the first camera 10 and the second camera 20.

Preferably this optical unit 55 ? telecentric or bitelecentric, that is to say that it forms a telecentric or bitelecentric optic having the entrance pupil and/or the exit pupil at? infinite.

The optical assembly 55 includes an optical beam splitter 50 (beam divider: typically, but not limited to, a prism) configured to split the light beam reflected from the object 100 into a first light beam directed along a first vertical optical arm 51 associated with the first camera 10 and coaxial to the vertical optical axis Z of the first camera 10, and a second light beam directed along a second horizontal optical arm 52 associated with the second camera 20 and coaxial to the horizontal optical axis of the second camera 20.

The optical arms 51, 52 referred to are in practice optical paths, preferably linear, which can be defined by optical and structural elements of a known type.

Advantageously, the horizontal optical arm 52 of the optical group 55, and consequently the optical axis of the second camera 20, ? positioned with a first angle a of offset from an X axis of the first sensor of the first camera 10.

Advantageously, the dual lens 55 optical group is capable of supporting two cameras with the same or even different sensor sizes and therefore allowing you to measure objects with different magnification factors for each camera and also to support two different magnification factors.

Advantageously and typically, the first camera 10 ? a high resolution camera, with a resolution preferably of at least 12 Megapixels which allows obtaining high resolution 3D data.

Advantageously the second camera 20? a camera capable of acquiring images containing information relating to the polarization of the light incident on the sensor, typically but not necessarily a camera with an integrated polarization sensor, which allows the acquisition of images without reflections, or with greatly reduced reflections and glare on reflective surfaces such as example, but not limited to, plastic and metal.

With the images coming from the second camera? It is possible to reconstruct the shape, and therefore 3D information, of those parts of components made of reflective material (mainly metal, such as welds) that cannot be effectively reconstructed with structured light projection techniques, precisely because? they are reflective materials.

The apparatus 1 comprises a system for illuminating the object 100 to be inspected from above, typically placed in a lower position, comprising a plurality of of 30i light projectors, typically four light projectors preferably configured to emit structured light, such as for example DLP (Digital Light Processing) projectors or other projectors capable of emitting fringes of structured light, even more so? preferably to emit sinusoidal or binary patterns (fringed images) suitable for carrying out a profile of the type known as phase-shift profiling (PSP).

In a first embodiment, illustrated in figures 1 and 2, the light projectors 30i have a vertical projection axis parallel to the vertical optical axis Z of the first camera 10, and the lighting system comprises a plurality of of mirrored reflectors 3 mutually interposed between the plurality? of projectors 30i and the station for the object 100 for the conversion of the plurality? of the 32i optical paths of light from the plurality? of the projectors 30i to the object 100. The individual light projectors 30i and the corresponding mirror reflectors 31 are equally angularly spaced around the vertical optical axis Z of the first camera 10.

Typically, at least a 30i light projector ? placed, with respect to the vertical optical axis Z of the first camera 10, in an angular position coinciding with that of the X axis of the first sensor 110 of the first camera 10.

In a second embodiment, illustrated in figures 3 and 4, the light projectors 30i have projection axes inclined with respect to the vertical axis Z and arranged to converge on the station for the object 100.

Also in the second embodiment, the individual light projectors 30i are equally angularly spaced around the vertical optical axis Z of the first camera 10.

By way of example but not limitation, each 30i light projector can? comprise at least one LED light source, at least one lens, an optical beam splitter and a digital micromirror device (DMD), where the lens is positioned between the LED light source and the optical beam splitter, and the optical beam splitter ? positioned between the lens and the digital micromirror display (DMD).

Typically, in a preferred solution, each light projector 30i comprises at least three different monochromatic LED light sources each associated with a corresponding lens, and an optical system interposed between the lenses and the optical beam splitter ? configured to collimate the light beams emitted by the three LED light sources.

The apparatus 1 can? further comprise an indirect lighting system of the object 100. This indirect lighting system preferably includes a plurality of of rings emitting monochromatic or polychromatic light 40i, or a plurality? of light emitters arranged along a plurality? of rings, which rings are coaxial to the vertical optical axis Z of the first camera 10 with increasing diameter and increasing distance away from the first camera 10.

Also advantageously a Z axis? of the second sensor of the second camera 20 ? oriented with a second offset angle? with respect to a vertical axis parallel to the vertical optical axis Z, uniquely determined by the value of the first offset angle a.

The offset of a corner? with respect to the vertical axis it corrects the rotation of the projection caused by the first offset angle a.

Therefore, if the first and second sensors are of the same shape and size, according to the present invention it is possible to acquire the object 100 with the same field of view from the first camera 10 and from the second camera 20.

Conveniently, the 30i light projectors and cameras (10 and 20) are operationally connected to a?unit? control electronics (not shown) which commands and controls the operation or activation of the light projectors 30i, the cameras (10 and 20) and possibly also the indirect lighting system of the object 100.

According to an optimal solution, the unit? control electronics? configured to operate or activate the 30i light projectors alternately, so? that the object to be inspected is 100? illuminated by a single light pattern produced by a single 30i light projector. In this way the cameras 10, 20 acquire successive images of the same object illuminated by (structured) light coming from different angles - without carrying out any movements of the object 100 n? of 30i projectors - and these images can be combined to have a complete and precise detection of totality? of the object.

Preferably, in the embodiments in which the light projectors 30i project structured light, thanks to the alternating activation of the projectors 30i themselves, a series of light patterns is projected onto the object 100, which can then be combined to perform a filometry.

In preferred embodiments, the first 10 and second 20 cameras are operationally connected to a unit? processing electronics (not shown) configured to process and combine the images acquired by the two cameras 10, 20 in order to obtain a detection of the characteristics of the object.

This unit? processing electronics can? be included, or consist, in the aforementioned unit? control electronics, or can? be included in, or consist of, an external computing device, such as a computer or the like.

The operation of the image acquisition apparatus for the inspection of an underlying object according to the invention appears evident from what has been described and illustrated and, in particular, it is essentially the following.

Object 100 to be inspected? positioned in a position typically lower than the apparatus and suitably illuminated by the plurality? of 30i light projectors and the plurality? of rings emitting monochromatic or polychromatic 40i light.

The light beam reflected by the object 100 through the double lens optical assembly 55 is divided into a first light beam directed along the first vertical optical arm 51 associated with the first camera 10 and coaxial with the vertical optical axis Z of the first camera 10, and in a second light beam directed along the second horizontal optical arm 52 associated with the second camera 20 and coaxial with the horizontal optical axis of the second camera 20.

For an effective, immediate and repetitive inspection reading of the apparatus 1, the appropriate images collected by the first camera 10 and the second camera 20 must be appropriately superimposed and processed by systems of a known type, for example by the unit processing electronics in the manner previously described.

Essential condition for correct reading by the device? that an alignment of the images acquired by the first camera 10 and the second camera 20 is guaranteed, and a congruence of at least two edges of the images acquired by the first sensor and the second sensor.

In case the horizontal optical arm 52 for construction and space reasons of the apparatus 1 is positioned with the first offset angle a with respect to the X axis of the first sensor 110 of the first camera 10, typically coinciding with the angular position of at least one projector of light 30i, the second sensor 120 of the second camera 20 has the Z axis? rotated with a second offset angle ? with respect to a vertical axis parallel to the Z axis, uniquely determined by the value of the first offset angle a.

Yes ? in practice it has been observed as the apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? visual of an underlying object according to the invention is particularly advantageous for being simple and effective, compact in size and for not presenting interference between different components.

The apparatus for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? visual of an underlying object like this? conceived? susceptible to numerous modifications and variations, all falling within the scope of the inventive concept, as defined by the claims; furthermore, all details can be replaced by technically equivalent elements.

For example ? It is possible to provide special means for reconfiguring the images projected onto the object.

In practice, the materials used, as well as? the dimensions may be any depending on the needs and the state of the art.

Claims (14)

1. Apparatus (1) for acquiring three-dimensional information of objects and surfaces for an artificial vision system for automatic optical quality inspection? view of an object (100) below, comprising a first camera (10) presenting a vertical optical axis Z and a first flat sensor (110) having orthogonal axes X,Y lying in a horizontal plane and a second camera (20) presenting a horizontal optical axis X? and a second flat sensor (120) having orthogonal axes Y?, Z? lying in a vertical plane, a lighting system from above? object comprising a plurality? of light projectors (30i), a double lens optical assembly (55) presenting a first vertical optical arm (51) associated with said first camera (10) and coaxial to said vertical optical axis Z and a second horizontal optical arm (52 ) associated with said second camera (20) and coaxial to said horizontal optical axis optical arm (51) and a second light beam directed along said second optical arm (52), where the light projectors (30i) are angularly spaced around the vertical optical axis Z of said first camera (10), and where said second horizontal optical arm (52) ? positioned with a first angle a of offset from an X axis of said first sensor (110) of said first camera (10). 2. Apparatus (1) according to the previous claim, characterized in that said optical assembly (55) is telecentric or bi-telecentric 3. Apparatus (1) according to any previous claim, characterized in that one of said first camera (10) and said second camera (20) is? a high resolution camera. 4. Apparatus (1) according to any previous claim, characterized in that one of said first camera (10) and said second camera (20) is? a camera capable of acquiring images containing information relating to the polarization of the light incident on the sensor. 5. Apparatus (1) according to any previous claim, characterized in that a Z axis? of said second sensor (120) of said second camera (20) ? oriented with a second offset angle? with respect to a vertical axis parallel to said Z axis, uniquely determined by the value of said first offset angle a. 6. Apparatus (1) according to any previous claim, characterized in that at least one light projector (30i) is placed, with respect to said vertical optical axis Z of said first camera (10), in an angular position coinciding with that of said axis X of said first sensor (110) of said first camera (10). 7. Apparatus (1) according to any previous claim, characterized by the fact of comprising a plurality? of rings emitting monochromatic or polychromatic light (40i), coaxial to said vertical optical axis Z of said first camera (10) having increasing diameter and increasing distance away from said first camera (10). 8. Apparatus (1) according to any previous claim, characterized by the fact that said plurality? of light projectors (30i) comprises at least four light projectors (30i) angularly equally spaced around said vertical optical axis Z of said first camera (10). 9. Apparatus (1) according to any previous claim, characterized by the fact that said plurality? of light projectors (30i) have a vertical projection axis parallel to said vertical optical axis Z of said first camera (10). 10. Apparatus (1) according to any previous claim, characterized by the fact of comprising a plurality? of mirror reflectors (3 li) mutually interposed between said plurality? of projectors (30i) and the station for the object (100) for the conversion of the plurality? of optical paths (32i) of light from said plurality? of projectors (30i) to said object (100). 11. Apparatus according to any claim from 1 to 8, characterized by the fact that said plurality? of light projectors (30i) have inclined projection axes arranged to converge on the station for said object (100). 12. Apparatus (1) according to any previous claim, characterized in that each light projector (30i) of the plurality? of light projectors (30i) includes at least one LED light source, at least one lens, an optical beam splitter and a digital micromirror display (DMD), where the lens is positioned between the LED light source and the optical beam splitter, and the optical beam splitter ? positioned between the lens and the digital micromirror device (DMD). 13. Apparatus (1) according to the previous claim, characterized in that at least one and preferably each light projector (30i) of the plurality? of light projectors (30i) includes at least three different monochromatic LED light sources each associated with a corresponding lens, and an optical system interposed between said lenses and said optical beam splitter and configured to collimate the light beams emitted by said three light sources LED light. 14. Apparatus (1) according to any previous claim, characterized in that it further comprises means for reconfiguring the images projected onto the object (100).