WO2018072434A1

WO2018072434A1 - Three-dimensional scanning method containing multiple lasers with different wavelengths and scanner

Info

Publication number: WO2018072434A1
Application number: PCT/CN2017/083919
Authority: WO
Inventors: 郑俊; 陈尚俭
Original assignee: 杭州思看科技有限公司
Priority date: 2016-10-19
Filing date: 2017-05-11
Publication date: 2018-04-26
Also published as: CN106500627A; CN106500627B

Abstract

A three-dimensional scanning method containing multiple lasers with different wavelengths and a scanner. The scanner for implementing the three-dimensional scanning method comprises a camera and at least two laser projectors with fixed positions, wherein the at least two laser projectors correspond to at least two different wavelengths, and positional relationships between spatial positions of light curtains projected by the laser projectors and the camera are all calibrated and known. The three-dimensional scanning method is as follows: recognizing and acquiring a highlighted center two-dimensional line according to a 2D pattern, which is photographed by the camera, of a laser contour line projected onto the surface of a scanned object, and then calculating according to a triangle method principle to acquire three-dimensional point cloud data. The scanning method and the scanner have good applicability, increase the reusability of a single scanner, and improve the cost performance ratio.

Description

Three-dimensional scanning method and scanner with multiple different wavelength lasers

[0001] The present invention relates to three-dimensional scanning technology, and more particularly to a three-dimensional scanning method and a scanner.

Background technique

[0002] The principle of three-dimensional measuring instruments such as handheld laser three-dimensional scanners and laser three-dimensional contour sensors that have appeared in recent years is to obtain three-dimensional data of the surface of an object according to the triangulation method by using a combination of a laser and a camera. Widely, it has become one of the main measurement methods in the field of high-precision 3D measurement, and is widely used in machinery, automotive, aviation, sculpture, medical and other industries.

[0003] This laser-based and camera-based three-dimensional measurement method commonly used in the laser band is a 405 nm purple laser, a 450 nm blue laser, a 532 nm green laser, a 650 nm red laser, etc. The impact is not the same. For example, the speckle phenomenon of the red laser is relatively obvious and affects the accuracy of the scanning, but the red laser is relatively stable and relatively safe to the human eye; in contrast, the speckle phenomenon of the blue laser is not obvious, and the accuracy of the camera recognition is high. This results in good scanning results, but the blue laser is harmful to the human eye and requires the use of goggles, which limits its three-dimensional scanning applications. Therefore, how to choose the right wavelength of the laser to meet the needs of different three-dimensional scanning occasions is a very difficult thing.

technical problem

[0004] In order to overcome the shortcomings of the existing handheld laser three-dimensional scanner, which only contain a single wavelength, poor applicability, and high cost, the present invention provides a single scanner with multiple different wavelengths, good applicability, and good applicability. Reusability, cost-effective 3D scanning method and scanner with multiple different wavelength lasers. Problem solution

Technical solution

[0005] The technical solution adopted by the present invention to solve the technical problem thereof is:

[0006] A three-dimensional scanning method comprising a plurality of lasers of different wavelengths, wherein the scanner implementing the three-dimensional scanning method comprises a camera fixed in position and at least two laser projectors, wherein the at least two laser projectors correspond to at least Two different wavelengths, the spatial position of the light curtain projected by the laser projector and the camera's The positional relationship is nominally known; the three-dimensional scanning method is as follows:

[0007] According to the 2D pattern of the laser contour projected by the camera to the surface of the scanned object, the two-dimensional line of the highlight center is acquired, and the spatial three-dimensional point cloud data is calculated according to the trigonometric principle.

[0008] Further, using a camera with a known positional relationship and the original camera to form a binocular stereo camera to capture feature points in the field of view to obtain relative position change information, and then use the camera to capture position change information of the frame before and after the frame. The three-dimensional contour point cloud data of the scanner is obtained in a continuous coordinate frame to obtain a complete surface three-dimensional contour point cloud data of the scanned object, thereby realizing continuous scanning.

[0009] Alternatively: using a pipeline with a position signal or a linear slide, a rotating platform with an angle signal to directly display the change information of the relative position of the scanner and the scanned object, and then use the camera to capture the front and rear frames. The position change information is obtained by splicing the three-dimensional contour point cloud data in a continuous frame of the scanner in a coordinate system, and obtaining the complete surface three-dimensional contour point cloud data of the scanned object to realize continuous scanning.

[0010] Further, the three-dimensional scanning method includes the following steps:

[0011] 1) pre-calibrating the camera and the distortion coefficient in the camera of different wavelengths;

[0012] 2) separately calibrating the spatial position between the light surface projected by the at least two laser projectors and the camera

[0013] 3) Before scanning, select the corresponding band laser projector to scan according to the accuracy of the scene and the scanning surface requirement, select the camera calibration internal reference and distortion coefficient corresponding to the wavelength according to the setting and output to the 2D image laser contour line extraction. And a 3D constructor; selecting a positional parameter of the laser and the camera corresponding to the wavelength according to the setting and outputting to the 3D constructor;

[0014] 4) scanning 吋, the camera inputs the captured surface contour laser contour image into the 2D image laser contour extractor, and the 2D image laser contour extractor according to the selected intra-camera internal reference and distortion coefficient The two-dimensional image is corrected for distortion, and the connected region of the line contour in the corrected image is extracted according to the difference of the pixel gray scale, and the two-dimensional line set of the sub-pixel-level highlight center is obtained according to the gray center of gravity in the connected region; The dimensional line set is output to the 3D constructor. According to the selected camera internal parameters, the distortion coefficient and the selected current working laser and the camera position calibration parameters, the three-dimensional contour point cloud data is obtained and output by the trigonometric principle.

[0015] In the step 1), the calibration method of the camera uses the Zhang Zhengyou calibration method to obtain the focal length of the camera, Heart offset and radial distortion and tangential distortion coefficients.

[0016] In the step 2), the specific calibration method of the spatial position between the light surface projected by the laser projector and the camera utilizes a flat plate having a known feature on the surface as a calibration plate, and the camera captures the line projected onto the calibration plate. The laser obtains a two-dimensional laser line image, and then uses the principle of affine transformation to "stretch" the calibration plate in the two-dimensional image into the true size in the three-dimensional coordinates, and obtain the three-dimensional laser contour in the camera coordinate system. Converting the scanner to a plurality of distances relative to the calibration plate to obtain a three-dimensional laser contour line in a plurality of camera coordinate systems, and the plane equation in the camera coordinate system fitting the point cloud of the three-dimensional contour line is projected by the laser The position of the spatial position between the glossy surface and the camera is calibrated.

[0017] A three-dimensional scanner comprising a plurality of lasers of different wavelengths, the scanner comprising at least two laser projectors, at least one camera for capturing a laser pattern projected onto a surface of the object to be inspected, and a connected camera for image recognition And a three-dimensional reconstruction computing processing unit; the at least two laser projectors correspond to at least two different wavelengths, and the spatial position of the light curtain projected by the laser projector and the positional relationship of the camera are both calibrated, the output of the camera The terminal is coupled to the calculation processing unit, the calculation processing unit includes a 2D image laser contour extractor, a 3D constructor, a first band switching determiner for selecting an internal parameter and a distortion coefficient of the calibration camera at a selected wavelength, and a second band switching determiner for selecting a spatial position between a light surface projected by one of the laser projectors and the camera, the output end of the camera being connected to the 2D image laser contour extractor, the 2D image a laser contour extractor and the 3D constructor, the first band switching judgment Respectively the 2D image contour extractor laser, 3D structure is connected, said second band switching determiner connected with the 3D builder.

[0018] Further, the laser projector and the trigger end of the camera are both connected to a synchronous trigger unit for selectively triggering one or more laser projectors of the same wavelength to operate synchronously with the camera.

Further, a multi-band pass filter is mounted on the camera, and a band pass band of the filter corresponds to at least two wavelengths of the at least two laser projectors.

[0020] Further, the laser projectors of at least two different wavelengths include a laser projector of a blue band and a laser projector of a red band.

[0021] The technical idea of the present invention is: installing a laser with a shorter wavelength band and a laser with a longer wavelength band in a scanner, because the refractive indices of different wavelengths of the two media are different, the fixed focal length and The aperture's camera has different focus points for different wavelengths of light, and captures the subject that reflects light in the shorter band. The focus is closer to the camera than the focus of the subject that reflects longer wavelengths of light. Taking the red and blue bands as an example, in order to get the correct focus, the blue object is closer to the camera than the red object, and when the camera resolution is the same, shooting closer objects means smaller. Partial projection is on the same area of the photosensitive component, that is, the blue object is smaller in size, but the resolution is higher, and the red object is larger in size, but the resolution is lower. In addition, since the laser is a monochromatic light, it will appear as an interference image when it is reflected on the surface of the object, and a non-uniformly distributed particle spot will appear on the laser contour of the surface of the object captured by the camera, that is, the laser Speckle. The speckle phenomenon of a shorter-wavelength laser is weaker than that of a longer-band laser, and the laser contour of the surface of the object captured by the camera is sharper, which is more favorable for obtaining surface details.

Advantageous effects of the invention

Beneficial effect

[0022] The beneficial effects of the present invention are mainly manifested in: Compared with a conventional single-wavelength laser-only three-dimensional scanner, it can be applied to both high-precision measurement occasions and efficient and safe use in ordinary three-dimensional scanning occasions. Greatly increase the reusability of a single scanner and increase its cost performance.

Brief description of the drawing

DRAWINGS

1 is a schematic diagram of a three-dimensional scanner containing a plurality of lasers of different wavelengths.

2 is a schematic diagram of an internal working principle of a synchronous trigger unit.

[0025] FIG. 3 is a schematic diagram of a computational processing unit.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is further described below in conjunction with the accompanying drawings.

Embodiment 1

[0028] Referring to FIG. 1 to FIG. 3, a three-dimensional scanning method including a plurality of lasers of different wavelengths, the scanner implementing the three-dimensional scanning method includes a camera fixed in position and at least two laser projectors, at least The two laser projectors correspond to at least two different wavelengths, and the spatial position of the light curtain projected by the laser projector and the positional relationship of the camera are both calibrated; the three-dimensional scanning method is as follows: [0029] The 2D line of the highlight center is acquired according to the 2D pattern of the laser contour projected by the camera to the surface of the scanned object, and the spatial 3D point cloud data is calculated according to the trigonometric principle.

[0030] Further, using a camera with a known positional relationship and the original camera to form a binocular stereo camera to capture feature points in the field of view to obtain relative position change information, and then using the camera to capture position change information of the frame before and after the frame The three-dimensional contour point cloud data of the scanner is obtained in a continuous coordinate frame to obtain a complete surface three-dimensional contour point cloud data of the scanned object, thereby realizing continuous scanning.

[0031] Alternatively: using a pipeline with a position signal or a linear slide, a rotating platform with an angle signal to directly display the change information of the relative position of the scanner and the scanned object, and then use the camera to capture the front and rear frames. The position change information is obtained by splicing the three-dimensional contour point cloud data in a continuous frame of the scanner in a coordinate system, and obtaining the complete surface three-dimensional contour point cloud data of the scanned object to realize continuous scanning.

[0032] Further, the three-dimensional scanning method includes the following steps:

[0033] 1) calibrating the camera and the distortion coefficient of the camera at different wavelengths in advance;

[0034] 2) separately calibrating the spatial position between the light surface projected by the at least two laser projectors and the camera

[0035] 3) Before scanning, select the corresponding band laser projector to scan according to the accuracy of the scene and the requirements of the scanning surface, select the internal calibration and distortion coefficient of the camera under the corresponding wavelength according to the setting and output to the 2D image laser contour extraction. And a 3D constructor; selecting a positional parameter of the laser and the camera corresponding to the wavelength according to the setting and outputting to the 3D constructor;

[0036] 4) scanning 吋, the camera inputs the captured laser surface image of the object surface into the 2D image laser contour extractor, and the 2D image laser contour extractor according to the selected camera internal parameter and distortion coefficient of the current band The two-dimensional image is corrected for distortion, and the connected region of the line contour in the corrected image is extracted according to the difference of the pixel gray scale, and the two-dimensional line set of the sub-pixel-level highlight center is obtained according to the gray center of gravity in the connected region; The dimensional line set is output to the 3D constructor. According to the selected camera internal parameters, the distortion coefficient and the selected current working laser and the camera position calibration parameters, the three-dimensional contour point cloud data is obtained and output by the trigonometric principle.

[0037] In the step 1), the calibration method of the camera uses the Zhang Zhengyou calibration method to obtain the focal length, the center offset, and the radial distortion and the tangential distortion coefficient of the camera. [0038] In the step 2), the specific calibration method of the spatial position between the light surface projected by the laser projector and the camera utilizes a flat plate having a known feature on the surface as a calibration plate, and the camera captures the line projected onto the calibration plate. The laser obtains a two-dimensional laser line image, and then uses the principle of affine transformation to "stretch" the calibration plate in the two-dimensional image into the true size in the three-dimensional coordinates, and obtain the three-dimensional laser contour in the camera coordinate system. Converting the scanner to a plurality of distances relative to the calibration plate to obtain a three-dimensional laser contour line in a plurality of camera coordinate systems, and the plane equation in the camera coordinate system fitting the point cloud of the three-dimensional contour line is projected by the laser The position of the spatial position between the glossy surface and the camera is calibrated.

[0039] Taking a linear laser projector with two cameras and two red and blue bands as an example, the implementation principle of obtaining three-dimensional contour data of the surface of the object is specifically described. As shown in Fig. 1, the band 1 laser projector is a red linear laser, the band 2 laser projector is a blue linear laser; the synchronous trigger unit is connected to the external trigger interface of one camera and the driving control of two laser projectors. The interface and the laser projector of the current working band are synchronously triggered; the image captured by the camera is sent to the calculation processing unit for stereoscopic three-dimensional reconstruction calculation and the final three-dimensional point cloud is output. The specific implementation is shown in Figure 3. The steps are as follows:

[0040] Step 1. Pre-calibrate the camera internal parameters and distortion coefficients of the camera at wavelength 1 and wavelength 2 (wavelength 1 and wavelength 2 are the wavelengths of laser No. 1 and laser No. 2, respectively), and save them in the calculation processing unit of the system. . The camera calibration method can obtain the focal length, center offset, and radial distortion and tangential distortion coefficient of the camera using the widely used Zhang Zhengyou calibration method.

[0041] Step 2. Priorly separately calibrate the spatial position between the light surface projected by the No. 1 laser and the No. 2 laser and the camera, and save the calibration laser calibration parameters No. 1 and No. 2 in the calculation processing unit of the system. . The specific calibration method of the spatial position between the light surface projected by the laser projector and the camera may preferably use a flat plate having a known feature on the surface as a calibration plate, and the camera captures a linear laser projected onto the calibration plate to obtain a two-dimensional image. The laser line image is then "stretched" into the true size of the three-dimensional coordinates by using the principle of affine transformation, and the three-dimensional laser contour line in the camera coordinate system is obtained. The three-dimensional laser contour line in multiple camera coordinate systems can be obtained by transforming the scanner with a plurality of distances relative to the calibration plate, and the plane equation in the camera coordinate system fitting the point cloud of these three-dimensional contour lines is projected by the laser. The position of the spatial position between the glossy surface and the camera is calibrated.

[0042] Step 3. Before scanning, select the red band or the blue band according to the accuracy of the scene and the demand of the scanning surface. The scan is performed and recorded in the band switching judger. The first band switching determiner selects the camera calibration internal reference and the distortion coefficient at the corresponding wavelength according to the setting and outputs the same to the 2D image laser contour extractor and the 3D constructor; the second band switching determiner selects the laser of the corresponding wavelength according to the setting. The position parameters of the camera are output to the 3D constructor.

[0043] Step 4.

After scanning, the camera inputs the captured laser contour image of the object surface into the 2D image laser contour extractor of the calculation processing unit, and the 2D image laser contour extractor switches the intra-camera reference of the current band selected by the first band according to the first band. Distortion coefficient corrects the two-dimensional image, and extracts a connected region of the line contour in the corrected image according to the pixel gray difference, and then calculates a sub-pixel-level highlight center two-dimensional line according to the gray center of gravity in the connected region set. The obtained two-dimensional line set is output to the 3D constructor, according to the camera internal parameter, the distortion coefficient of the current band selected by the first band switching determiner, and the position calibration parameter of the current working laser and the camera selected by the second band switching determiner. The three-dimensional contour point cloud data is obtained by the trigonometric principle and output.

Embodiment 2

1 to 3, a three-dimensional scanner including a plurality of lasers of different wavelengths, the scanner comprising at least two laser projectors, at least one camera for photographing a laser pattern projected onto a surface of the object to be inspected And a computing processing unit for connecting the camera for image recognition and three-dimensional reconstruction; the at least two laser projectors correspond to at least two different wavelengths, and the spatial position of the light curtain projected by the laser projector and the positional relationship of the camera are both calibrated. The output end of the camera is connected to the calculation processing unit, and the calculation processing unit includes a 2D image laser contour extractor, a 3D constructor, and an internal parameter and a distortion coefficient for selecting a calibration camera at a selected wavelength. a first band switching determiner and a second band switching determiner for selecting a spatial position between the light surface projected by the one of the laser projectors and the camera, the output end of the camera, and the 2D image laser contour extraction Connected, the 2D image laser contour extractor and the 3D constructor, the A band switching judging device is respectively connected to the 2D image laser contour extractor and the 3D constructor, and the second band switching judging device is respectively connected to the 3D fabric.

[0046] Further, the laser projector and the trigger end of the camera are both connected to a synchronous trigger unit for selectively triggering one or more laser projectors of the same wavelength to operate synchronously with the camera. Further, a multi-band pass filter is mounted on the camera, and a band pass band of the filter corresponds to at least two wavelengths of the at least two laser projectors.

[0048] Further, the laser projectors of at least two different wavelengths include a laser projector of a blue band and a laser projector of a red band.

[0049] The system and principle of the present invention will be described by taking a three-dimensional scanner equipped with a red-blue two-band linear laser projector as an example. The working principle of the present invention is shown in FIG. 1. The band 1 laser projector is a red linear laser, the band 2 laser projector is a blue linear laser, and the synchronous trigger unit is connected to an external trigger interface of one or two cameras. The driving interface of the two laser projectors is synchronously triggered by the camera and a laser projector of the current working band; the image captured by the camera is sent to the calculation processing unit for stereoscopic three-dimensional reconstruction calculation and the final three-dimensional point cloud is output.

[0050] The synchronous trigger unit may internally control the working beat by the micro control unit MCU, and output the synchronous control signal to the power device MOS through the isolation device OC to finally control the synchronous operation of the laser projector LASER1/LA SER2 and the camera CAMERA. . The firmware of the MCU is determined according to the user's choice to synchronize the trigger band at a certain moment. LASER1 and CAMERAl (and CAMERA2) of the red light are synchronized or LASER2 and CAMERAl (and CAMERA2) of the band 2 are synchronized.

[0051] Of course, if continuous scanning is performed, the MCU cyclically triggers the laser and the camera according to the set frame rate, and the camera continuously inputs the captured image into the calculation processing unit for three-dimensional stereoscopic three-dimensional reconstruction calculation, and finally continuously outputs the three-dimensional point cloud. data.

Claims

Claim

[Claim 1] A three-dimensional scanning method comprising a plurality of lasers of different wavelengths, wherein: the scanner implementing the three-dimensional scanning method comprises a camera fixed in position and at least two laser projectors, at least two The laser projectors correspond to at least two different wavelengths, and the spatial position of the light curtain projected by the laser projector and the positional relationship of the camera are both calibrated; the three-dimensional scanning method is as follows:

According to the 2D pattern of the laser contour projected by the camera to the surface of the scanned object, the two-dimensional line of the highlight center is obtained, and the spatial three-dimensional point cloud data is calculated according to the trigonometric principle.

[Claim 2] The three-dimensional scanning method comprising a plurality of lasers of different wavelengths according to claim 1, wherein: a camera with a known positional relationship is used to form a binocular stereo camera with the original camera to capture the field of view. The feature points are used to obtain the change information of the relative position, and then the camera captures the position change information of the front and rear frames, and the three-dimensional contour point cloud data of the scanner continuous frame is spliced in a coordinate system to obtain a complete surface three-dimensional contour of the scanned object. Point cloud data for continuous scanning.

[Claim 3] The three-dimensional scanning method comprising a plurality of lasers of different wavelengths according to claim 1, wherein: the scanned object is placed on a rotating platform with a position signal using a pipeline or a linear sliding table or an angled signal. Directly obtain the change information of the relative position of the scanner and the scanned object, and then use the camera to capture the position change information of the front and rear frame 将 to obtain the three-dimensional contour point cloud data of the continuous frame of the scanner and splicing it in a coordinate system to obtain the complete object to be scanned. Surface 3D contour point cloud data for continuous scanning.

The method of claim 3, wherein the three-dimensional scanning method comprises the following steps:

1) Pre-calibrate the camera and the distortion coefficient of the camera at different wavelengths;

2) separately calibrating the spatial position between the light surface projected by at least two laser projectors and the camera;

3) Before scanning, select the corresponding band laser projector for scanning according to the accuracy of the scene and the scanning surface. Select the camera calibration internal distortion and distortion system according to the setting. And outputting to the 2D image laser contour extractor and the 3D constructor; selecting the position parameters of the laser and the camera corresponding to the wavelength according to the setting and outputting to the 3D constructor;

4) After scanning, the camera inputs the captured laser contour image of the object surface into the 2D image laser contour extractor, and the 2D image laser contour extractor pairs the two-dimensional image according to the selected camera internal parameter and distortion coefficient of the current band. Distortion correction is performed, and a connected region of the line contour in the corrected image is extracted according to the pixel gray difference, and then a sub-pixel-level highlight center two-dimensional line set is obtained according to the gray center of gravity in the connected region; the obtained two-dimensional line set is obtained. It is output to the 3D constructor, and according to the selected camera internal parameters, the distortion coefficient and the selected current working laser and the position calibration parameters of the camera, the three-dimensional contour point cloud data is obtained by the trigonometric principle and output.

[Claim 5] The three-dimensional scanning method of the laser containing a plurality of different wavelengths according to claim 4, wherein: in the step 1), the calibration method of the camera uses the Zhang Zhengyou calibration method to obtain the focal length and center offset of the camera. Volume and radial distortion and tangential distortion coefficients.

[Claim 6] The three-dimensional scanning method of the laser containing a plurality of different wavelengths according to claim 4, wherein: in the step 2), the spatial position between the light surface projected by the laser projector and the camera The specific calibration method utilizes a flat plate having a known feature on the surface as a calibration plate, and the camera captures a linear laser beam projected onto the calibration plate to obtain a two-dimensional laser line image, and then uses the affine transformation principle to calibrate the plate in the two-dimensional image. "Stretching" is the true size in the three-dimensional coordinates, and the three-dimensional laser contour line in the camera coordinate system is obtained at the same time; the scanner is converted into multiple distances relative to the calibration plate to obtain the three-dimensional laser contour line in multiple camera coordinate systems, The plane equations in the camera coordinate system fitted by the point cloud of these three-dimensional contours are the calibration parameters of the spatial position between the light surface projected by the laser and the camera.

[Claim 7] A scanner for realizing a three-dimensional scanning method comprising a plurality of lasers of different wavelengths according to claim 1, wherein: said scanner comprises at least two laser projectors, at least one for photographing a camera that projects a laser pattern on the surface of the detected object and a calculation processing unit that connects the camera for image recognition and three-dimensional reconstruction; the at least two laser projectors correspond to at least two different wavelengths, and the light curtain projected by the laser projector The positional relationship between the spatial position and the camera is nominally known, the output of the camera and the calculation The processing unit is connected, and the calculation processing unit comprises a 2D image laser contour extractor, a 3D constructor, a first band switching determiner for selecting an internal parameter and a distortion coefficient of the calibration camera at a selected wavelength, and for selecting one of the a second band switching determiner for spatial position between the light surface projected by the laser projector and the camera, the output end of the camera being connected to the 2D image laser contour extractor, the 2D image laser contour extractor And the 3D constructor, the first band switching determiner is respectively connected to the 2D image laser contour extractor and the 3D constructor, and the second band switching determiner is respectively connected to the 3D constructor.

[Claim 8] The scanner according to claim 7, wherein: the laser projector and the trigger end of the camera are both associated with one or more laser projectors for selectively triggering the same wavelength The sync trigger unit is connected to the camera synchronously.

[Claim 9] The scanner according to claim 7 or 8, wherein: a multi-band pass filter is mounted on the camera, and a band pass band of the filter is at least two The laser projector corresponds to at least two wavelengths.

[Claim 10] The scanner according to claim 7 or 8, wherein: at least two laser projectors of different wavelengths include a blue band laser projector and a red band laser projector.