WO2023160133A1 - A differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources - Google Patents

A differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources Download PDF

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WO2023160133A1
WO2023160133A1 PCT/CN2022/138508 CN2022138508W WO2023160133A1 WO 2023160133 A1 WO2023160133 A1 WO 2023160133A1 CN 2022138508 W CN2022138508 W CN 2022138508W WO 2023160133 A1 WO2023160133 A1 WO 2023160133A1
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light source
capture
line
angle
measurement
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PCT/CN2022/138508
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French (fr)
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Yixin Xu
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Yixin Xu
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/0004—Microscopes specially adapted for specific applications
    • G02B21/0016—Technical microscopes, e.g. for inspection or measuring in industrial production processes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/245—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using a plurality of fixed, simultaneously operating transducers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G01B11/2518—Projection by scanning of the object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
    • G01B11/2545—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object with one projection direction and several detection directions, e.g. stereo
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/56—Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B21/00—Microscopes
    • G02B21/06—Means for illuminating specimens
    • G02B21/08—Condensers
    • G02B21/082—Condensers for incident illumination only
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/48—Laser speckle optics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
    • H01L22/10—Measuring as part of the manufacturing process
    • H01L22/12—Measuring as part of the manufacturing process for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions

Definitions

  • the present invention relates to the field of 3D optical measurement technology, in particular, to a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources which can perform high-speed and high-accuracy 3D measurement for micro objects with diffuse-reflective surface.
  • the laser-based triangulation method uses a laser light source to project a laser line onto the object to be measured and extracts the centre line of the corresponding distorted profile line due to surface undulations and calculates the height information based on the trigonometric function.
  • the width of the line projected onto the object surface determines the accuracy, the finer the line the higher the accuracy; the length of the line projected onto the object surface determines the measurement speed, under the promise of all pixels in the longitudinal direction of the camera can be fully utilised, the longer the line the faster the measurement.
  • laser projection that onto a highly reflective object surface can cause speckle, which affects the accuracy of the measurement, and all hardware and software methods to reduce laser speckle that have been applied to this segment so far have significantly reduced the measurement speed.
  • incoherent light sources instead of using laser light sources can overcome the influence of speckle on accuracy and repeatability, but it is not possible to project line with same width, brightness and sharpness as laser source do under the same conditions, the accuracy and speed are very limited.
  • the accuracy of triangulation is influenced by angle between camera and light source, the greater the angle between camera and light source, the better the height accuracy of the measurement.
  • angle between camera and light source the greater the angle between camera and light source, the better the height accuracy of the measurement.
  • the present invention aims to realize high-speed and high-accuracy 3D measurement for micro objects with diffuse-reflective surfaces, such as wafer bump and chip solder ball in the semiconductor packaging field, solder paste and micro component in the SMT field.
  • the invention is to be achieved by a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, as follows.
  • the invention provides a incoherent line light source module that using a high power LED point light source witch can be RGB-LED or monochrome-LED, for dual-wavelength differential, RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength, while the monochrome-LED can be selected according to the desired wavelength , a collimator needs to be installed in front of the light source to ensure that the field of view of the light source is as small as possible in order to increase the utilization of light, collimator can either be convex lens, doublet lens, single lens such as a free-form-surface prism, or lens-set capable of achieving a similar effect, the light source may place at the focus of the collimator.
  • the invention provides a incoherent line light source module, which uses split-projection to generate a scan-line by means of point source light.
  • the invention provides a incoherent line light source module which mounts a focusing and shaping optic element behind a slit
  • the optic element can either be a single lens such as a cylindrical lens or a combination of optical elements capable of achieving a similar effect
  • the optic element can suppress stray light that passing through the slit to ensure the focusing effect of the projected rays within the depth of field, and it also can modulate the line length which increases with the working distance.
  • the invention provides a incoherent line light source differential module which contains two incoherent line light source modules, the two modules are set to different wavelengths and slit widths, combine the lights by spectroscope, the fused light is projected through lens to object surface, if the telecentric lens can provide a large depth of field and ensure that the line width remains constant within the depth of field range, the camera captures the corresponding image, in order to meet the actual 3D measurement scene requirements, the angle between camera and light source needs to balance the measurement range of height and measurement accuracy and consider the influence of shadow occlusion.
  • the invention provides a incoherent dual-wavelength differential technique, the technique can get a narrower and sharper line profile by subtraction of two line profiles with different wavelength, it requires proper adjustment, alignment and calibration of the light source to ensure that the centre of the two line profiles are overlapping, the angle between camera and light source need to be able to cover the full height measurement range of the image, and ensure not be out of focus because of the depth limitations of the lens, the calculation of the contour uses triangulation contouring, the formula is as follows:
  • ⁇ z is the height difference
  • ⁇ x is lateral shift in the image plane
  • ⁇ magnification of the imaging lens
  • ⁇ is angle between the light source and the capture system.
  • the invention provides a incoherent dual-wavelength differential based capture module, in addition to the choice of a colour camera, the module provides a dual-monochrome-camera module, use two monochrome-cameras simultaneous capture through the spectroscope can improve the accuracy, in order to not decrease the measurement speed, increase LED brightness to ensure that will not have to increase the exposure time of camera because of the using of spectroscope.
  • two monochrome-cameras can capture simultaneous to increase the accuracy of the measurement or can alternately expose to increase the measurement speed without increasing the exposure time.
  • the overall capture speed can exceed the maximum frame rate of a single camera and can be up to twice as fast.
  • the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it uses coaxial or near-coaxial line light source module for projection, together with multi-angle capture modules for simultaneous exposure to avoid shadow occlusion and the reduction in measurement speed caused by multiple projections.
  • the invention provides another embodiment, it uses a coaxial or near-coaxial capture module for exposure and multi-angle line light source modules for projection, the method increases the exposure time because of each projection is separately exposed for capture, but it does not require point-cloud fusion, the data processing is simple, the image is easy to capture and the cost is lower than the coaxial method.
  • the invention provides another embodiment, it uses both multi-angle projection and multi-angle capture, the line light source modules and the capture modules are installed in a number of different angular positions, each capture module can capture after any line light source module projected, if there are m line light source modules, n capture modules, there will be a total of m *n combinations.
  • FIG. 1 is a diagram of the incoherent line light module of one embodiment of the present invention.
  • FIG. 2 is a diagram of the device based on capturing with two sides and dual-wavelength differential projection of one embodiment of the present invention
  • FIG. 3 is a distribution diagram of the dual-wavelength differential luminous intensity of one embodiment of the present invention.
  • FIG. 4 is diagram of device combines coaxial or near-coaxial projection with multi-angle capture of one embodiment of the present invention
  • FIG. 5 is diagram of device combines coaxial or near-coaxial capture with multi-angle projection of one embodiment of the present invention
  • FIG. 6 is diagram of device combines multi-angle capture with multi-angle projection of one embodiment of the present invention.
  • 200a, 200b two line light source modules with different wavelengths
  • 210a, 210b two monochrome-cameras with different angles
  • 220a, 220b two cameras with different angles
  • 60, 62, 64, 66 muti-angle line light source modules
  • 61, 63, 65, 67 muti-angle capture modules
  • the invention provides a incoherent line light source module that using a high power LED point light source [10] witch can be RGB-LED or monochrome-LED, for dual-wavelength differential, RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength, while the monochrome-LED can be selected according to the desired wavelength , a collimator [11] needs to be installed in front of the light source to ensure that the field of view of the light source is as small as possible in order to increase the utilization of light, collimator can either be convex lens, doublet lens, single lens such as a free-form-surface prism, or lens-set capable of achieving a similar effect, the light source may place at the focus of the collimator.
  • a high power LED point light source witch can be RGB-LED or monochrome-LED, for dual-wavelength differential
  • RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength
  • the monochrome-LED can be selected according to the desired wavelength
  • the invention provides a incoherent line light source module, which uses split [12] -projection to generate a scan-line by means of point source light.
  • the invention provides a incoherent line light source module which mounts a focusing and shaping optic element [13] behind a slit
  • the optic element can either be a single lens such as a cylindrical lens or a combination of optical elements capable of achieving a similar effect
  • the optic element can suppress stray light that passing through the slit to ensure the focusing effect of the projected rays within the depth of field, and it also can modulate the line length which increases with the working distance.
  • the invention provides a incoherent line light source differential module which contains two incoherent line light source modules [200a, 200b] , the two modules are set to different wavelengths and slit widths, combine the lights by spectroscope [201] , the fused light is projected through lens to object surface, if the telecentric lens [202] can provide a large depth of field and ensure that the line width remains constant within the depth of field range, the camera captures the corresponding image, in order to meet the actual 3D measurement scene requirements, the angle between camera and light source needs to balance the measurement range of height and measurement accuracy and consider the influence of shadow occlusion.
  • the invention provides a incoherent dual-wavelength differential technique, the technique can get a narrower and sharper line profile [32] by subtraction of two line profiles with different wavelength [30, 31] , it requires proper adjustment, alignment and calibration of the light source to ensure that the centre of the two line profiles are overlapping, the angle between camera and light source need to be able to cover the full height measurement range of the image, and ensure not be out of focus because of the depth limitations of the lens, the calculation of the contour uses triangulation contouring, the formula is as follows :
  • ⁇ z is the height difference
  • ⁇ x is lateral shift in the image plane
  • ⁇ magnification of the imaging lens
  • ⁇ is angle between the light source and the capture system.
  • the invention provides a capture module based on incoherent dual-wavelength differential, in addition to the choice of a colour camera, the module provides a dual-monochrome-camera module, use two monochrome-cameras [210a, 210b] simultaneous capture through the spectroscope can improve the accuracy, in order to not decrease the measurement speed, increase LED brightness to ensure that will not have to increase the exposure time of camera because of the using of spectroscope.
  • two monochrome-cameras can capture simultaneous to increase the accuracy of the measurement or can alternately expose to increase the measurement speed without increasing the exposure time.
  • the overall capture speed can exceed the maximum frame rate of a single camera and can be up to twice as fast.
  • the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it uses coaxial or near-coaxial line light source module [40] for projection, together with multi-angle capture modules [41 ⁇ 46] for simultaneous exposure to avoid shadow occlusion and the reduction in measurement speed caused by multiple projections.
  • the invention provides another embodiment, it uses a coaxial or near-coaxial capture module [50] for exposure and multi-angle line light source modules [51 ⁇ 56] for projection, the method increases the exposure time because of each projection is separately exposed for capture, but it does not require point-cloud fusion, the data processing is simple, the image is easy to capture and the cost is lower than the coaxial method.
  • the invention provides another embodiment, it uses both multi-angle projection and multi-angle capture, the line light source modules and the capture modules are installed in a number of different angular positions, each capture module can capture after any line light source module projected, if there are m line light source modules, n capture modules, there will be a total of m *n combinations.
  • the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it provides a incoherent line light source module and its light-path to in place of conventional laser light source, it can overcome the influence of height measurement accuracy caused by speckle which caused by laser projection that onto a highly reflective object surface. And then based on incoherent line light source module, the invention provides a dual-wavelength differential module and its light-path, it can project brighter and sharper scan-line to improve the measurement speed and accuracy. In order to overcome the influence of shadow occlusion to take complete 3D reconstruction for micro objects such as bump, solder ball, the invention provides a method that combines multi-angle capture with multi-angle projection.

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Abstract

A differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources (200a, 200b) is provided. It can realize high-speed and high-accuracy measurement. A incoherent line light source (10) and its light-path are provided in place of conventional laser light source. It can solve the problem of the low measurement accuracy caused by speckle which caused by laser projection onto high reflectance object surface. A dual-wavelength differential module (20) and its light-path are provided. It can project brighter and sharper scan-line to improve the measurement speed and accuracy. In order to overcome influence of shadow occlusion, multi-angle capture modules (61, 63, 65, 67) are integrated with multi-angle projection modules (60, 62, 64, 66). It can take complete 3D reconstruction for micro objects such as bump, solder ball.

Description

A differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources Technical Field
The present invention relates to the field of 3D optical measurement technology, in particular, to a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources which can perform high-speed and high-accuracy 3D measurement for micro objects with diffuse-reflective surface.
Background Art
In the field of optical high-accuracy measurement, it is challenging to use laser line-scanning measurement for micro objects with diffuse-reflective surface, such as wafer bump, chip solder ball, solder paste and micro component in surface mount technology (SMT) . Take wafer bump for example, in the field of advanced packaging, the bump on the wafer will be used for IO connection and its height and coplanarity are the key to ensure reliable connection. A bump that is not high enough will not be connected effectively, while a bump that is too tall will prevent the connection with adjacent bumps, it may even lead to damage to the electrical test instrument during subsequent electrical testing. Therefore the 3D measurement of wafer bumps is a guarantee of reliable connection and is the most important matter in wafer-level measurement and inspection. Along with the increasing miniaturisation and densification of wafer bumps, products with a bump pitch of 40 μm or less are in mass production already. These micro bumps typically range from 2-24 μm in height and 15-25 μm in diameter and the count on a single wafer can be as high as 5-10 million. These trends are making high-speed, high-accuracy measurement of bump height and coplanarity an increasingly demanding challenge.
The laser-based triangulation method uses a laser light source to project a laser line onto the object to be measured and extracts the centre line of the corresponding distorted profile line due to surface undulations and calculates the height information based on the trigonometric function. The width of the line projected onto the object surface determines the accuracy, the finer the line the higher the accuracy; the length of the line projected onto the object surface determines the measurement speed, under the promise of all pixels in the longitudinal direction of the camera can be fully utilised, the longer the line the faster the measurement. However, laser projection that onto a highly reflective object surface can cause speckle, which affects the accuracy of the measurement, and all hardware and software methods to reduce laser speckle that have been applied to this segment so far have significantly reduced the measurement speed.
Using incoherent light sources instead of using laser light sources can overcome the  influence of speckle on accuracy and repeatability, but it is not possible to project line with same width, brightness and sharpness as laser source do under the same conditions, the accuracy and speed are very limited.
The accuracy of triangulation is influenced by angle between camera and light source, the greater the angle between camera and light source, the better the height accuracy of the measurement. As wafer bumps become increasingly dense, large angle can easily produce shadow and thus erroneous-data or dead spots of measurement, but complete 3D reconstruction of the top surface-profile of wafer bump requires a measurement system with large range of measurement angle.
Technical Solution
The present invention aims to realize high-speed and high-accuracy 3D measurement for micro objects with diffuse-reflective surfaces, such as wafer bump and chip solder ball in the semiconductor packaging field, solder paste and micro component in the SMT field. The invention is to be achieved by a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, as follows.
S1, the invention provides a incoherent line light source module that using a high power LED point light source witch can be RGB-LED or monochrome-LED, for dual-wavelength differential, RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength, while the monochrome-LED can be selected according to the desired wavelength , a collimator needs to be installed in front of the light source to ensure that the field of view of the light source is as small as possible in order to increase the utilization of light, collimator can either be convex lens, doublet lens, single lens such as a free-form-surface prism, or lens-set capable of achieving a similar effect, the light source may place at the focus of the collimator.
S2, the invention provides a incoherent line light source module, which uses split-projection to generate a scan-line by means of point source light.
S3, the invention provides a incoherent line light source module which mounts a focusing and shaping optic element behind a slit, the optic element can either be a single lens such as a cylindrical lens or a combination of optical elements capable of achieving a similar effect, the optic element can suppress stray light that passing through the slit to ensure the focusing effect of the projected rays within the depth of field, and it also can modulate the line length which increases with the working distance.
S4, the invention provides a incoherent line light source differential module which contains two incoherent line light source modules, the two modules are set to different wavelengths and slit widths, combine the lights by spectroscope, the fused light is projected through lens to object  surface, if the telecentric lens can provide a large depth of field and ensure that the line width remains constant within the depth of field range, the camera captures the corresponding image, in order to meet the actual 3D measurement scene requirements, the angle between camera and light source needs to balance the measurement range of height and measurement accuracy and consider the influence of shadow occlusion.
S5, the invention provides a incoherent dual-wavelength differential technique, the technique can get a narrower and sharper line profile by subtraction of two line profiles with different wavelength, it requires proper adjustment, alignment and calibration of the light source to ensure that the centre of the two line profiles are overlapping, the angle between camera and light source need to be able to cover the full height measurement range of the image, and ensure not be out of focus because of the depth limitations of the lens, the calculation of the contour uses triangulation contouring, the formula is as follows:
Figure PCTCN2022138508-appb-000001
Δz is the height difference, Δx is lateral shift in the image plane, β is magnification of the imaging lens, θ is angle between the light source and the capture system.
S6, the invention provides a incoherent dual-wavelength differential based capture module, in addition to the choice of a colour camera, the module provides a dual-monochrome-camera module, use two monochrome-cameras simultaneous capture through the spectroscope can improve the accuracy, in order to not decrease the measurement speed, increase LED brightness to ensure that will not have to increase the exposure time of camera because of the using of spectroscope.
S7, two monochrome-cameras can capture simultaneous to increase the accuracy of the measurement or can alternately expose to increase the measurement speed without increasing the exposure time. By setting the cameras to expose alternately, the overall capture speed can exceed the maximum frame rate of a single camera and can be up to twice as fast.
S8, the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it uses coaxial or near-coaxial line light source module for projection, together with multi-angle capture modules for simultaneous exposure to avoid shadow occlusion and the reduction in measurement speed caused by multiple projections.
S9, the invention provides another embodiment, it uses a coaxial or near-coaxial capture module for exposure and multi-angle line light source modules for projection, the method increases the exposure time because of each projection is separately exposed for capture, but it does not require point-cloud fusion, the data processing is simple, the image is easy to capture and the cost is lower than the coaxial method.
S10, the invention provides another embodiment, it uses both multi-angle projection and multi-angle capture, the line light source modules and the capture modules are installed in a number of different angular positions, each capture module can capture after any line light source module projected, if there are m line light source modules, n capture modules, there will be a total of m *n combinations. The larger the angle, the better the height resolution, but the more influence from shadow, for slender and densely distributed measurement objects such as copper pillar bumps, there will be a large number of shadows, you can choose a projection-capture combination with small angle, for micro and sparse distributed measurement objects such as micro solder bumps, there will be less effect from shadow, if it is more important to accuracy of height, you can choose a projection-capture combination with large angle, you can use different modules at the same time or optionally to improve the wide applicability of device.
Description of Drawings
FIG. 1 is a diagram of the incoherent line light module of one embodiment of the present invention;
FIG. 2 is a diagram of the device based on capturing with two sides and dual-wavelength differential projection of one embodiment of the present invention;
FIG. 3 is a distribution diagram of the dual-wavelength differential luminous intensity of one embodiment of the present invention;
FIG. 4 is diagram of device combines coaxial or near-coaxial projection with multi-angle capture of one embodiment of the present invention;
FIG. 5 is diagram of device combines coaxial or near-coaxial capture with multi-angle projection of one embodiment of the present invention;
FIG. 6 is diagram of device combines multi-angle capture with multi-angle projection of one embodiment of the present invention;
Drawing marks description:
10: high-power LED light source;
11: collimating lens;
12: slit;
13: focusing and shaping optical element;
14: objective plane;
20: dual-wavelength differential module;
200a, 200b: two line light source modules with different wavelengths;
201: spectroscope;
202: telecentric lens;
21, 22: two dual-camera capture modules with different angles;
210a, 210b: two monochrome-cameras with different angles;
211: spectroscope;
212: telecentric lens;
220a, 220b: two cameras with different angles;
221: reflector;
222: telecentric lens;
30: luminous intensity distribution curve of wavelength-1;
31: luminous intensity distribution curve of wavelength-2;
32: distribution curve of dual-wavelength differential luminous intensity;
40: coaxial or near-coaxial light source module;
41, 42, 43, 44, 45, 46: muti-angle capture modules;
50: coaxial or near-coaxial capture module;
51, 52, 53, 54, 55, 56: muti-angle line light source modules;
60, 62, 64, 66: muti-angle line light source modules;
61, 63, 65, 67: muti-angle capture modules
68: angle-1;
69: angle-2.
Best Mode
The specific embodiments of the invention are further described below in conjunction with the drawings to illustrate the technical solutions of the invention in detail.
S1, with reference to FIG. 1, the invention provides a incoherent line light source module that using a high power LED point light source [10] witch can be RGB-LED or monochrome-LED, for dual-wavelength differential, RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength, while the monochrome-LED can be selected according to the desired wavelength , a collimator [11] needs to be installed in front of the light source to ensure that the field of view of the light source is as small as possible in order to increase the utilization of light, collimator can either be convex lens, doublet lens, single lens such as a free-form-surface prism, or lens-set capable of achieving a similar effect, the light source may place at the focus of the  collimator.
S2, with reference to FIG. 1, the invention provides a incoherent line light source module, which uses split [12] -projection to generate a scan-line by means of point source light.
S3, with reference to FIG. 1, the invention provides a incoherent line light source module which mounts a focusing and shaping optic element [13] behind a slit, the optic element can either be a single lens such as a cylindrical lens or a combination of optical elements capable of achieving a similar effect, the optic element can suppress stray light that passing through the slit to ensure the focusing effect of the projected rays within the depth of field, and it also can modulate the line length which increases with the working distance.
S4, with reference to FIG. 2, the invention provides a incoherent line light source differential module which contains two incoherent line light source modules [200a, 200b] , the two modules are set to different wavelengths and slit widths, combine the lights by spectroscope [201] , the fused light is projected through lens to object surface, if the telecentric lens [202] can provide a large depth of field and ensure that the line width remains constant within the depth of field range, the camera captures the corresponding image, in order to meet the actual 3D measurement scene requirements, the angle between camera and light source needs to balance the measurement range of height and measurement accuracy and consider the influence of shadow occlusion.
S5, with reference to FIG. 3, the invention provides a incoherent dual-wavelength differential technique, the technique can get a narrower and sharper line profile [32] by subtraction of two line profiles with different wavelength [30, 31] , it requires proper adjustment, alignment and calibration of the light source to ensure that the centre of the two line profiles are overlapping, the angle between camera and light source need to be able to cover the full height measurement range of the image, and ensure not be out of focus because of the depth limitations of the lens, the calculation of the contour uses triangulation contouring, the formula is as follows :
Figure PCTCN2022138508-appb-000002
Δz is the height difference, Δx is lateral shift in the image plane, β is magnification of the imaging lens, θ is angle between the light source and the capture system.
S6, with reference to FIG. 2, the invention provides a capture module based on incoherent  dual-wavelength differential, in addition to the choice of a colour camera, the module provides a dual-monochrome-camera module, use two monochrome-cameras [210a, 210b] simultaneous capture through the spectroscope can improve the accuracy, in order to not decrease the measurement speed, increase LED brightness to ensure that will not have to increase the exposure time of camera because of the using of spectroscope.
S7, two monochrome-cameras can capture simultaneous to increase the accuracy of the measurement or can alternately expose to increase the measurement speed without increasing the exposure time. By setting the cameras to expose alternately, the overall capture speed can exceed the maximum frame rate of a single camera and can be up to twice as fast.
S8, with reference to FIG. 4, the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it uses coaxial or near-coaxial line light source module [40] for projection, together with multi-angle capture modules [41～46] for simultaneous exposure to avoid shadow occlusion and the reduction in measurement speed caused by multiple projections.
S9, with reference to FIG. 5, the invention provides another embodiment, it uses a coaxial or near-coaxial capture module [50] for exposure and multi-angle line light source modules [51～56] for projection, the method increases the exposure time because of each projection is separately exposed for capture, but it does not require point-cloud fusion, the data processing is simple, the image is easy to capture and the cost is lower than the coaxial method.
S10, with reference to FIG. 6, the invention provides another embodiment, it uses both multi-angle projection and multi-angle capture, the line light source modules and the capture modules are installed in a number of different angular positions, each capture module can capture after any line light source module projected, if there are m line light source modules, n capture modules, there will be a total of m *n combinations. The larger the angle, the better the height resolution, but the more influence from shadow, for slender and densely distributed measurement objects such as copper pillar bumps, there will be a large number of shadows, you can choose a projection-capture combination with small angle [68] such as 60, 61, for micro and sparse distributed measurement objects such as micro solder bumps, there will be less influence from shadow, if it is more important to accuracy of height, you can choose a projection-capture combination with large angle [69] such as 60, 67, you can use different modules at the same time or optionally to improve the wide applicability of device.
As mentioned before, the invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, it provides a incoherent line light source module and its light-path to in place of conventional laser light source, it can  overcome the influence of height measurement accuracy caused by speckle which caused by laser projection that onto a highly reflective object surface. And then based on incoherent line light source module, the invention provides a dual-wavelength differential module and its light-path, it can project brighter and sharper scan-line to improve the measurement speed and accuracy. In order to overcome the influence of shadow occlusion to take complete 3D reconstruction for micro objects such as bump, solder ball, the invention provides a method that combines multi-angle capture with multi-angle projection.
Although the above describes specific embodiments of the invention, it should be understood that these are merely illustrative example, the scope of protection of the invention is limited by the appended claims. A person skilled in the art may make various changes or modifications to these embodiments without departing from the principle and substance of the invention, these changes and modifications all fall within the scope of protection of the invention.

Claims (6)

  1. The present invention aims to perform high-speed and high-accuracy 3D measurement for micro objects with diffuse-reflective surface, such as wafer bump, chip solder ball, solder paste and micro component in surface mount technology (SMT) , to be specific by a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, to achieve the aim, the invention provides a non-coherent line light source module, its characteristics are as follows:
    S1, use a incoherent line light source module that using a high power LED point light source witch can be RGB-LED or monochrome-LED, for dual-wavelength differential, RGB-LED can choose one of the monochrome-LED or multiple LED mixed into the desired wavelength, while the monochrome-LED can be selected according to the desired wavelength , a collimator needs to be installed in front of the light source to ensure that the field of view of the light source is as small as possible in order to increase the utilization of light, collimator can either be convex lens, doublet lens, single lens such as a free-form-surface prism, or lens-set capable of achieving a similar effect, the light source may place at the focus of the collimator;
    S2, use split-projection to generate a scan-line by means of point source light;
    S3, mount a focusing and shaping optic element behind a slit, the optic element can either be a single lens such as a cylindrical lens or a combination of optical elements capable of achieving a similar effect, the optic element can suppress stray light that passing through the slit to ensure the focusing effect of the projected rays within the depth of field, and it also can modulate the line length which increases with the working distance.
  2. The invention provides a incoherent line light source differential module, its characteristics are as follows:
    S4, it contains two incoherent line light source modules, the two modules are set to different wavelengths and slit widths, combine the lights by spectroscope, the fused light is projected through lens to object surface, if the telecentric lens can provide a large depth of field and ensure that the line width remains constant within the depth of field range, the camera captures the corresponding image, in order to meet the actual 3D measurement scene requirements, the angle between camera and light source needs to balance the measurement range of height and measurement accuracy and consider the influence of shadow occlusion;
    S5, get a narrower and sharper line profile by subtraction of two line profiles with different wavelength, it requires proper adjustment, alignment and calibration of the light source to ensure that the centre of the two line profiles are overlapping, the angle between camera and light source need to be able to cover the full height measurement range of the image, and ensure not be out of focus because of the depth limitations of the lens, the calculation of the contour uses triangulation  contouring, the formula is as follows:
    Figure PCTCN2022138508-appb-100001
    Δz is the height difference, Δx is lateral shift in the image plane, β is magnification of the imaging lens, θ is angle between the light source and the capture system.
  3. The invention provides a incoherent dual-wavelength differential based capture module, its characteristics are as follows:
    S6, in addition to the choice of a colour camera, the module provides a dual-monochrome-camera module, use two monochrome-cameras simultaneous capture through the spectroscope can improve the accuracy, in order to not decrease the measurement speed, increase LED brightness to ensure that will not have to increase the exposure time of camera because of the using of spectroscope;
    S7, two monochrome-cameras can capture simultaneous to increase the accuracy of the measurement or can alternately expose to increase the measurement speed without increasing the exposure time, by setting the cameras to expose alternately, the overall capture speed can exceed the maximum frame rate of a single camera and can be up to twice as fast.
  4. The invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, its characteristics are as follows:
    S8, use coaxial or near-coaxial line light source module for projection, together with multi-angle capture modules for simultaneous exposure to avoid shadow occlusion and the reduction in measurement speed caused by multiple projections.
  5. The invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, its characteristics are as follows:
    S9, use a coaxial or near-coaxial capture module for exposure and multi-angle line light source modules for projection, the method increases the exposure time because of each projection is separately exposed for capture, but it does not require point-cloud fusion, the data processing is simple, the image is easy to capture and the cost is lower than the coaxial method.
  6. The invention provides a differential light-section line-scanning profilometry based on multi-angle projection of incoherent light sources, its characteristics are as follows:
    S10, use both multi-angle projection and multi-angle capture, the line light source modules and the  capture modules are installed in a number of different angular positions, each capture module can capture after any line light source module projected, if there are m line light source modules, n capture modules, there will be a total of m *n combinations, the larger the angle, the better the height resolution, but the more influence from shadow, for slender and densely distributed measurement objects such as copper pillar bumps, there will be a large number of shadows, you can choose a projection-capture combination with small angle, for micro and sparse distributed measurement objects such as micro solder bumps, there will be less effect from shadow, if it is more important to accuracy of height, you can choose a projection-capture combination with large angle, you can use different modules at the same time or optionally to improve the wide applicability of device.
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