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CN-115777055-B - Line scanning three-dimensional sensing system

CN115777055BCN 115777055 BCN115777055 BCN 115777055BCN-115777055-B

Abstract

A line scanning three-dimensional sensing system measures the surface profile of an object. In the system, a Dispersive Optical Module (DOM) performs a forward optical process, disperses a polychromatic linear beam into a graded narrow-band linear beam (CNLLB), and focuses CNLLB on different focal planes, forming a rainbow light pattern, to illuminate the scanned surface of an object. The illuminated object displays an informative color image (IBCI) containing information about the height of the scanning surface. The DOM captures IBCI and performs a backward optical process, optically converging the captured IBCI to form an elongated light pattern. The backward optical processing is a reverse processing of the forward processing. The slit spatially filters the elongated light pattern to form an output light ray. By analyzing the spectral content of each point on the output light, the height profile of the scanned surface can be obtained.

Inventors

  • JIANG JINBO
  • Xie Sifan
  • CHI YONG

Assignees

  • 香港应用科技研究院有限公司

Dates

Publication Date
20260508
Application Date
20220831
Priority Date
20220812

Claims (17)

  1. 1. A line scanning three-dimensional sensing system for measuring a surface profile of an object, the system comprising: the light source module is used for generating multi-color line light beams, is a color mixing light source module and comprises: a light source for generating original light rays which together provide polychromatic light, and A color mixing rod optically coupled to the first slit for spatially filtering the polychromatic light beam provided to the first slit, the color mixing rod having an elongated shape for mixing the original light rays to produce the polychromatic light beam such that at least a portion of the polychromatic light beam received by the first slit is substantially uniform in color; a first slit for spatially filtering the polychromatic light beam to form a polychromatic linear light beam; a dispersive optical module configured to: Performing a forward optical process to disperse the polychromatic linear beam received from the first slit into a graded narrow band linear beam and focus the graded narrow band linear beam onto different focal planes, respectively, to form a rainbow light pattern for illuminating a scan surface of the object during surface profile measurement, thereby causing the illuminated object to display an information-containing color image on the object, the information-containing color image containing height information of the scan surface; Capturing the information-containing color image, and Performing a backward optical process for optically converging the captured information-containing color image to form an elongated light pattern, wherein the backward optical process is a reverse of the forward optical process, and A second slit for spatially filtering the elongated light pattern to form an output light, whereby a height profile of the scanning surface is obtained by analyzing the spectral content of each point of the output light, whereby the surface profile is determined from the respective height profiles obtained for a plurality of scanning surfaces of the object.
  2. 2. The system of claim 1, wherein the dispersive optical module comprises: A first set of lenses aligned on a first optical axis, the first set of lenses configured to disperse the polychromatic linear beam into the graded narrowband linear beam and focus the graded narrowband linear beam onto the different focal planes distributed over a predetermined length of the first optical axis, respectively, to form the rainbow light pattern, and A second set of lenses configured to optically converge the captured information-containing color image to form the elongated light pattern, wherein the first set of filters and the second set of lenses share one or more shared lenses, at least one shared lens for simultaneously outputting the rainbow light pattern and inputting the information-containing color image, thereby avoiding the burden of aligning the first set of lenses and the second set of lenses to output the rainbow light pattern and input the information-containing color image.
  3. 3. The system of claim 2, wherein the dispersive optical module further comprises a beam splitter optically coupled to the one or more shared lenses and positioned in the first set of lenses to replicate the captured information-containing color image in two, one of which is directed to the second slit.
  4. 4. The system of claim 3, wherein the second set of lenses includes one or more additional lenses not shared with the first set of lenses, the one or more additional lenses disposed between the beam splitter and the second slit for optically processing the captured information-containing color image before the captured information-containing color image reaches the second slit, wherein the one or more additional lenses are replicas of the first set of lenses for optically processing the polychromatic linear beam and of the corresponding one or more lenses disposed between the beam splitter and the first slit.
  5. 5. The system of claim 2, wherein: the first slit is configured such that the polychromatic linear beam emitted to the dispersive optical module at any point on the first slit has a first set of chief rays having a divergence angle that is within 1 ° as measured based on the first optical axis; The first set of lenses is configured such that the graded narrowband linear beam received at any point on the rainbow light pattern has a second set of chief rays having a convergence angle within 1 ° as measured based on the first optical axis; the system further comprises a platform for positioning the object during the surface profile measurement, the platform comprising a reference plane on which the object is adapted to be placed, and The first set of lenses is oriented such that the first optical axis is perpendicular to the reference plane, causing the rainbow light pattern to be perpendicular to the reference plane, thereby also allowing the surface profile to be measured when the scanning surface comprises grooves.
  6. 6. The system of claim 1, wherein: The light source comprises one or more light emitting diodes for collectively generating the primary light, and The color mixing light source module further includes an asymmetric total internal reflection lens for guiding the original light generated from the one or more light emitting diodes to the color mixing rod, wherein the asymmetric total internal reflection lens has different lengths in an X direction and a Y direction.
  7. 7. The system of claim 1, wherein: the light source includes one or more light emitting diodes each deposited with a solar spectrum phosphor fill configured to produce a spectrum in a range of at least 400 nanometers to 700 nanometers, the one or more light emitting diodes configured to optically excite the solar spectrum phosphor fill to produce the primary light rays that collectively provide the polychromatic light, and The color mixing rod is optically coupled to the light source to directly receive the original light rays from the light source.
  8. 8. The system of claim 1, further comprising: A grating for diffracting the output light, thereby forming a spectral image of the output light; An imaging sensor for imaging the spectral image, the spectral content of each point of the output light being determinable from the spectral image; A collimating lens module positioned between the second slit and the grating for collimating the output light before the output light is diffracted by the grating, and And a condenser module positioned between the grating and the imaging sensor for focusing the spectral image onto the imaging sensor.
  9. 9. The system of claim 8, further comprising: And a prism for reflecting the spectral image emitted from the grating to the condenser module, the prism being configured to redirect the spectral image such that directions of the collimating lens module and the condenser module are perpendicular to each other, thereby facilitating alignment and assembly of the collimating lens module and the condenser module.
  10. 10. The system of claim 2, further comprising: a third slit for spatially filtering the copy of the elongated light pattern received at the third slit to form a second output light ray, and A two-dimensional line scanning camera for performing color imaging on the second output light, whereby a two-dimensional image of the object can be obtained after scanning the plurality of scanning surfaces for three-dimensional sensing; Wherein the dispersive optical module further comprises: A first beam splitter disposed in the first set of lenses to replicate the captured information-containing color image into two copies, one of which is directed to the second slit, and A second beam splitter disposed in the first set of lenses to replicate the captured information-containing color image into two copies, one of which is directed to the third slit.
  11. 11. The system of claim 10, further comprising: A grating for diffracting the output light, thereby forming a spectral image of the output light; An imaging sensor for imaging the spectral image, the spectral content of each point of the output light being determinable from the spectral image; A collimating lens module positioned between the second slit and the grating for collimating the output light before the output light is diffracted by the grating, and And a condenser module positioned between the grating and the imaging sensor for focusing the spectral image onto the imaging sensor.
  12. 12. A line scanning three-dimensional sensing system for measuring a surface profile of an object, the system comprising: The light source module is used for generating multicolor light beams, is a color mixing light source module and comprises: a light source for generating original light rays which together provide polychromatic light, and A color mixing rod optically coupled to the first slit for spatially filtering the polychromatic light beam provided to the first slit, the color mixing rod having an elongated shape for mixing the original light rays to produce the polychromatic light beam such that at least a portion of the polychromatic light beam received by the first slit is substantially uniform in color; a first slit optically coupled to the light source module for spatially filtering the polychromatic light beam to form a polychromatic linear light beam; A first dispersive optical module configured to perform a forward optical process, disperse the polychromatic linear beam received from the first slit into a converging narrow-band linear beam, and focus the converging narrow-band linear beam on different focal planes to form a rainbow light pattern, the rainbow light pattern being used to illuminate a scan surface of the object during surface profile measurement, thereby causing the illuminated object to display an information-containing color image on the object, the information-containing color image containing height information of the scan surface; A second dispersive optical module configured to capture the information-containing color image and to perform a backward optical process that optically condenses the captured information-containing color image to form an elongated light pattern, wherein the backward optical process is a reverse process of the forward optical process, and the first dispersive optical module and the second dispersive optical module are disposed side by side; A two-pass lens module configured to reposition the rainbow light pattern generated by the first dispersive optical module to an offset position where the object is adapted to be positioned and to direct the information-containing color image from the offset position to the second dispersive optical module to allow the second dispersive optical module to capture the information-containing color image, and A second slit for spatially filtering the elongated light pattern to form an output light, whereby a height profile of the scanning surface is obtained by analyzing the spectral content of each point of the output light, whereby the surface profile is determined from the respective height profiles obtained for a plurality of scanning surfaces of the object.
  13. 13. The system of claim 12, wherein: the first dispersive optics module comprises a first plurality of lenses, and The second dispersive optical module includes a second plurality of lenses, wherein the second plurality of lenses is a replica of the first plurality of lenses.
  14. 14. The system of claim 13, wherein the second dispersive optical module further comprises a reflector disposed in the second plurality of lenses.
  15. 15. The system of claim 12, wherein: The light source comprises one or more light emitting diodes for collectively generating the primary light, and The color mixing light source module further comprises an asymmetric total internal reflection lens for mixing the original light rays generated from the one or more light emitting diodes to form an intermediate light output such that the radiant power of the intermediate light output is substantially uniform, the original light rays in the intermediate light output being fed into the color mixing rod, wherein the asymmetric total internal reflection lens has different lengths in an X direction and a Y direction.
  16. 16. The system of claim 12, wherein: the light source includes one or more light emitting diodes each deposited with a solar spectrum phosphor fill configured to produce a spectrum in a range of at least 400 nanometers to 700 nanometers, the one or more light emitting diodes configured to optically excite the solar spectrum phosphor fill to produce the primary light rays that collectively provide the polychromatic light, and The color mixing rod is optically coupled to the light source to directly receive the original light rays from the light source.
  17. 17. The system of claim 12, further comprising: A grating for diffracting the output light, thereby forming a spectral image of the output light; An imaging sensor for imaging the spectral image, the spectral content of each point of the output light being determinable from the spectral image; A collimating lens module positioned between the second slit and the grating for collimating the output light before the output light is diffracted by the grating, and And a condenser module positioned between the grating and the imaging sensor for focusing the spectral image onto the imaging sensor.

Description

Line scanning three-dimensional sensing system List of abbreviated expressions 2D two-dimensional 3D three-dimensional CNLLB gradient narrow-band linear beam DOM dispersion optical module FOV field of view IBCI color image containing information LED light emitting diode NIR near infrared PLLB polychromatic linear beam TIR total internal reflection Technical Field The present invention relates generally to line scanning three-dimensional sensing systems for measuring the surface profile of an object. More particularly, the present invention relates to a system that disperses a polychromatic linear beam into a graded narrowband linear beam and focuses the graded narrowband linear beam at different heights above a reference surface to form a rainbow light pattern for surface profile measurement. Background Currently, bright surfaces, multi-layer transparent surfaces, and precision electronic surfaces are the most complex surfaces to be inspected, almost becoming the bottleneck in the machine vision field. Products such as electronic components, semiconductor wafers, cover glass for cellular phones, automotive metal parts, etc. are always difficult to detect. It has been noted that two-dimensional machine vision is not satisfactory and therefore rapid, accurate three-dimensional measurement techniques are required. Line scanning three-dimensional sensing is the most advanced technique for detecting such surfaces. Conventional line scanning three-dimensional sensing systems have problems in some cases. Shadow problems exist with tilt axis scanning three-dimensional sensing systems as disclosed in US 7,936,464 B2. Smaller features behind larger objects cannot be detected. Furthermore, the deep holes and grooves cannot be measured. Systems using pinhole arrays or digital micromirror device panels as disclosed in US 2020/0363619 A1 and DE 10200607172 B4 can be used for measuring deep holes and grooves. However, alignment is critical, resolution is limited by pinhole size, and crosstalk is a serious disadvantage. There are also various problems with systems using cylindrical lenses and diffractive elements as disclosed in US 8,654,352 B1. Since cylindrical lenses are used, rotational tolerances in the lens assembly process are critical, which results in stringent requirements for lens alignment. The diffraction element may also cause zero-order and higher-order diffraction noise. There is a need in the art to develop a new line-scan three-dimensional sensing system to address the shadow problem described above (so that the deep hole and groove can be measured) while making the system easier to align. Disclosure of Invention A first aspect of the present invention is to provide a line scanning three-dimensional sensing system for measuring a surface profile of an object. The system includes a light source module, a first slit, a DOM, and a second slit. The light source module is used for generating a polychromatic light beam. The first slit is used to spatially filter the polychromatic light beam to form PLLB. The DOM is configured to perform a forward optical process, disperse PLLB received from the first slit into CNLLB, and focus CNLLB on different focal planes, respectively, to form a rainbow light pattern for illuminating a scan surface of an object during surface profile measurement, causing IBCI to be displayed on the illuminated object. IBCI contains height information of the scanned surface. The DOM is further configured to capture IBCI and perform backward optical processing of the captured IBCI to form an elongated light pattern. The backward optical processing is the reverse of the forward optical processing. The second slit is used for spatially filtering the elongated light pattern to form an output light ray. By analyzing the spectral content of the points of the output light, the height profile of the scanned surface can be obtained, and thus from the respective height profiles obtained for a plurality of scanned surfaces of the object, the surface profile can be determined. Preferably, the DOM includes first and second sets of lenses. The first set of lenses are aligned on a first optical axis. The first set of lenses is configured to disperse PLLB into CNLLB and focus CNLLB onto different focal planes, respectively, distributed over a predetermined length of the first optical axis to form a rainbow light pattern. The second set of lenses is configured to optically converge the captured IBCI to form an elongated light pattern. The first and second groups of lenses share one or more shared lenses. At least one shared lens is used to output a rainbow light pattern and an input IBCI simultaneously. Thus, it avoids the burden of aligning the first and second sets of lenses to output the rainbow light pattern and input IBCI. Preferably, the DOM further comprises a beam splitter optically coupled to the one or more shared lenses and positioned in the first set of lenses such that the captured IBCI is repli