CN100573040C - The scaling method of object surface three-dimensional contour structure light measurement system - Google Patents

The scaling method of object surface three-dimensional contour structure light measurement system Download PDF

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CN100573040C
CN100573040C CNB200810019813XA CN200810019813A CN100573040C CN 100573040 C CN100573040 C CN 100573040C CN B200810019813X A CNB200810019813X A CN B200810019813XA CN 200810019813 A CN200810019813 A CN 200810019813A CN 100573040 C CN100573040 C CN 100573040C
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target plate
target
projector
black
camera
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CNB200810019813XA
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CN101245994A (en
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程筱胜
戴宁
廖文和
崔海华
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南京航空航天大学
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Abstract

A kind of scaling method of object surface three-dimensional contour structure light measurement system belongs to method for three-dimensional measurement and Instrument technology field.It is made up of following steps: (1) black and white camera calibration; (2) projector calibrating; (3) many plane references method obtains the required parameter of total system; It is characterized in that: (4) described target plate is colored target plate, and the prospect on the target plate and background colour are two kinds of two kinds of colors that the black and white camera had same reflecting properties; (5) when (1) goes on foot the black and white camera calibration, throw a kind of colorama to the target plate, this colorama is identical with one of background colour with target plate prospect.The inventive method has higher stability, reliability than traditional use black and white target plate, has improved stated accuracy, accurately important effect is arranged aspect the measurement at object surface three-dimensional contour structure light.

Description

The scaling method of object surface three-dimensional contour structure light measurement system

Affiliated technical field

A kind of scaling method of object surface three-dimensional contour structure light measurement system relates to the computer vision measurement field, belongs to method for three-dimensional measurement and Instrument technology field, relates in particular to the demarcation occasion to structured light measurement system.

Background technology

The three-dimensional measurement technology of object should have very general in fields such as product design and manufacturing, quality testing and control, robot vision.The structural light measurement technology is the branch of a very important and development prospect in the three-dimensional measurement technology, and whether the accurate demarcation of measuring system is prerequisite and the key condition that can system accurate reconstruction.It is exactly geometry and the optical characteristics of obtaining video camera and projector inside that measuring system is demarcated, i.e. the coordinate system of inner parameter, and two instruments is with respect to the position relation of space coordinates, i.e. external parameter.

The demarcation of structured light measurement system comprises two parts, the one, and to the demarcation of camera, the 2nd, to the demarcation of projector.To the present Tsa i of the demarcation of camera based on radial constraint unanimity (RAC) [R.Y.Tsai, " A Versatile CameraCalibration Technique for High-Accuracy 3D Machine Vision Metrology Using Off-the-shelf TVCameras and Lenses; " IEEE Joumal of Robotics Automation.Vol.RA-3.No.4, August 1987.] the most commonly used, this method is earlier by the linear dimensions that radially collimates the constraint solving camera model, introduce nonlinear parameter then, adopt process of iteration to obtain whole parameter.Demarcation to projector has also had certain research at present, is the most widely the reverse model that projector is used as camera is demarcated scaling method and similar to the demarcation of camera.But to the structural light measurement that camera and projector integrate is that body is demarcated, and just has a lot of restrictive conditions.With the circular index point is the target pattern, concrete scaling method is: at first to camera calibration, camera is gathered known coordinate space target dot image, by the noise filtering to image, Threshold Segmentation, profile extracts, oval identification, extract at ellipse fitting and center, obtains the two dimensional image coordinate of three-dimensional target punctuate, corresponding each the 3-d and 2-d point of coupling adopts the scaling method of Tsai that camera is demarcated to as the input data; Then, projector is demarcated: because projector do not have image collecting function, therefore, it is right to adopt auxiliary structured light or other coding mode to obtain to be used for the two-dimentional three-dimensional target punctuate of projector calibrating indirectly to the demarcation of projector.Mode one, the target Board position that assurance is used for camera calibration is known, the circle of projector projects known coordinate or square pattern are to being used for camera calibration target plate, camera collects the pattern of projection, detect central coordinate of circle, utilize the camera parameter of demarcation and the coordinate of target plate Z direction, reconstruct the space three-dimensional target point coordinate of the pattern of projector projects, the corresponding two-dimentional three-dimensional point of coupling is demarcated conduct and is imported data; Mode two, the target Board position that assurance is used for camera calibration is known, the strip encoding of projector projects structured light is to the target plate, camera collects strip encoding, utilize (Gray+phase) Gray code+phase-shifting technique decoding technique to obtain the encoded radio of each target point two-dimensional pixel coordinate, the encoded radio of each target point is matched in the projector, and the pixel coordinate in the projector is exactly the two-dimensional pixel coordinate of three-dimensional target punctuate, has realized the function of " extracting " image of projector.The two-dimentional three-dimensional point of coupling correspondence is to carrying out the demarcation of projector as the input data.Find from above method, in the demarcation to projector, guarantee the location aware of target, the projector projects image, the camera images acquired, it is exactly the demarcation that target point on the target is used for camera and projector simultaneously, and the demarcation pattern that is used for camera and projector is different, when the projection coding mode is used for projector calibrating on traditional black and white target pattern so, the target image of gathering will be subjected to being used to demarcating the influence of the target pattern of camera, can not obtain good target pattern, seriously influence the precision of demarcating.

Summary of the invention

Deficiency at existing method, a kind of scaling method that utilizes the object surface three-dimensional contour structure light measurement system of colored target pattern has been proposed, characteristic according to optics has well solved above problem, and guaranteed that the target pattern of gathering is the very high black of contrast, make table fixed more reliable and more stable.

A kind of scaling method of object surface three-dimensional contour structure light measurement system, form by following steps:

(1), black and white camera calibration: camera collects and is used for camera calibration target image clearly, utilize image process method, extract the two-dimensional pixel coordinate of target point, known target point three-dimensional coordinate and corresponding two-dimensional pixel coordinate are stored in the demarcation input data of this locus as the target plate;

(2), projector calibrating: keep the target plate in this locus, the target plate is under the irradiation of white light, projector projects black and white encode grating is to the target plate, the camera collection has the target image of grating fringe, utilize decoding technique to obtain the encoded radio of each pixel, correspond to the pixel coordinate that has the same-code value in the projector according to encoded radio, obtain this pixel coordinate in projector.The three-dimensional coordinate of this point and in projector corresponding one dimension pixel coordinate store in the demarcation input data of this locus as the target plate;

(3), the target plate is accurately moved a certain distance repetition (1), (2) step along the direction perpendicular to the target plate, at least move three times, the multi-group data that obtains is imported data as demarcating, use many plane references method to carry out system calibrating, obtain the parameter of camera and the final required demarcation of projector;

It is characterized in that:

(4), described target plate is colored target plate, and the prospect on the target plate and background colour are two kinds of two kinds of colors that the black and white camera had same reflecting properties.During projector calibrating: colored target plate is under the irradiation of white light, and the projector projects grating pattern is to the target plate, and black-white CCD phase function collects and not influenced by the pattern of scaling board own, the good grating encoding stripe pattern of half-tone information;

(5), when (1) step black and white camera calibration, throw a kind of colorama to the target plate, this colorama is identical with one of background colour with target plate prospect.During the black and white camera calibration: because a kind of color target pattern only reflects the light that has same color with it, the colour demarcation pattern of taking in the black-white CCD camera so is the good black white image of black white contrast.Wherein identical with projection light color target pattern presents white in soot-and-whitewash, the target patterns different with the projection light color present black in soot-and-whitewash.Can utilize projector to finish with the described projection colorama of this step, to have avoided the complicated of device.

The present invention adopts two kinds the black and white camera had same emanative two kinds of colors respectively as target plate foreground and background colour.Tradition black and white target plate, when projector calibrating, black and white target image has interference to the half-tone information collection of encode grating image, and it is influential to find the solution phase decoding.And adopt colored target to avoid this problem.

On the basis of adopting colored target plate, utilize a kind of colorama the same of optical characteristics projection to colored target plate, in the black and white camera, can obtain and the strong black white image of contrast that traditional black and white target plate has the equal in quality effect with target plate prospect or background colour.

The inventive method has higher stability, reliability than traditional black and white target plate method, has improved stated accuracy.

Description of drawings

Fig. 1 is used for the circular colored target synoptic diagram of system calibrating for the present invention, and the target disc thing is that foreground is red, and target backboard scenery be a blueness.

Fig. 2 is the colored target plate of the present invention target plate image that the black and white camera collects under the irradiation of ruddiness.

The grating fringe target image that Fig. 3 presents in camera for the conventional target target.

Fig. 4 is the colored target plate of the present invention projector projects that camera collects under white light grating fringe target image to the target plate.

Fig. 5 sets up the schematic diagram of 3 d space coordinate for target plate of the present invention.

Specific embodiments

Below the inventive method is described in further details in conjunction with the accompanying drawings.The present invention uses simple color plane target first, and all parameters of structure light vision measuring systems camera and two parts of projector are demarcated.

The target plate is made.Fig. 1 is a colored target of the present invention, and the target disc thing is that foreground is red, and target plate background color is that background colour is blue.This target is a printing color target round dot on an irreflexive viscose paper, be attached to flatness less than on 0.01 the flat board, this target dot matrix is classified M * N as, ranks are strict vertical, the centre distance of circular hole equates and known (Δ x, Δ y), is that with traditional target difference target of the present invention is colored, under certain illumination, can obtains and the black and white gray scale target image of traditional black and white target effect same.The straight line at place, the horizontal center of circle of target image is an X-axis, and vertically the straight line at place, the center of circle is a Y-axis, is the Z axle with vertical target target direction, sets up space coordinates, and coordinate system meets the right-hand rule.Among the figure near the center big radius of circle be 1.5 or 2 times of roundlet, guarantee obviously to distinguish out both use so that detect ordering.

Demarcation pre-treatment work.Open camera and projector, adjust the target plate in the common visual field of camera and projector and the best depth of field, the projector projects red light source adjusts camera lens and make the phase function see a good target pattern of contrast, and the target image is enough clear to the target plate.The projector projects grating fringe makes the phase function see that a half-tone information well has grating fringe target pattern by adjusting camera aperture.

Camera calibration input data are obtained.The projector projects red light source is to the target plate, red identical with foreground in the target plate, because the characteristic of optics, because a kind of color target pattern only reflects the light that has same color with it, the colour demarcation pattern of taking in the black-white CCD camera so is black and white.Camera collects the good and target image clearly of black white contrast, to the picture noise filtering, and Threshold Segmentation, profile extracts, oval identification, extract at ellipse fitting and center, obtains the two dimensional image sub-pix central coordinate of circle of the target point of known three-dimensional coordinate on the target plate.Three peacekeeping two-dimensional coordinates of mark on the target plate to as demarcating the input data storage.The black and white that collects is demarcated pattern such as Fig. 2.

Projector calibrating input data are obtained.Projector does not have the function of images acquired, therefore, obtain the picture point of calibration point at projector by round-about way.The projector projects encode grating utilizes the method for encoded light and phase shift to obtain the encoded radio of every bit on the photographic images to target, finds the picture point of calibration point in projector according to encoded radio.For the same pixel coordinate point that guarantees camera calibration and twice shooting of projector calibrating corresponding to same three-dimensional target punctuate, guarantee that the target plate is constant in this locus, projector projects encode grating striped light is to the target plate, camera capturing and coding grating pattern such as Fig. 4, the raster image that camera collects is not subjected to the influence of the alternate target plate that is used for camera calibration of the red indigo plant of bottom, obtain good grating fringe half-tone information, avoided traditional black and white bottom that is subjected to be used for the influence of the target pattern of camera calibration, by Flame Image Process raster image is carried out coding-decoding operation, obtain the encoded radio of each picture element, because during the projector projects raster image, on projecting apparatus screen to identical encoded radio should be arranged, the pixel coordinate that has the same-code value in camera and the projector is mapped, just realized the coupling of picture in camera and projector of same three-dimensional coordinate point, make projector have the function of " extracting " image, thereby obtained the picture point of three-dimensional target punctuate in projector.So just realized the acquisition function of a position target image.

Obtain a plurality of position calibration input data.Promptly (the z distance repeats above step, collects the picture point of the demarcation input data of the camera of a reposition and projector perpendicular to the direction running target target of target plate along the z direction of principal axis.In order to obtain more accurate calibrating parameters, the target plate should cover bigger area of space such as Fig. 5 in the position in space as far as possible.

Systematic parameter is obtained in demarcation.As the input data, use many plane references of RAC method of Tsai to carry out system calibrating three-dimensional target punctuate corresponding in many planes, space and corresponding picture point, obtain the systematic survey parameters needed.So just realized the accurate demarcation of object surface three-dimensional contour structure light measurement system.

Claims (3)

1, a kind of scaling method of object surface three-dimensional contour structure light measurement system, form by following steps:
(1), black and white camera calibration: camera collects and is used for camera calibration target image clearly, utilize image process method, extract the two-dimensional pixel coordinate of target point, known target point three-dimensional coordinate and corresponding two-dimensional pixel coordinate are stored in the demarcation input data of this locus as the target plate;
(2), projector calibrating: keep the target plate motionless in this locus, the target plate is under the irradiation of white light, projector projects black and white encode grating striped is to the target plate, the camera collection has the target image of grating fringe, utilize decoding technique to obtain the encoded radio of each pixel, correspond to the pixel coordinate that has the same-code value in the projector according to encoded radio, obtain this pixel coordinate in projector, the three-dimensional coordinate of this point and in projector corresponding one dimension pixel coordinate store in the demarcation input data of this locus as the target plate;
(3), the target plate is accurately moved a certain distance along the direction perpendicular to the target plate, repetition (1), (2) step, at least move three times, the multi-group data that obtains is imported data as demarcating, use many plane references method to obtain the parameter of camera and the final required demarcation of projector;
It is characterized in that:
(4), described target plate is colored target plate, and the prospect on the target plate and background colour are two kinds of two kinds of colors that the black and white camera had same reflecting properties;
(5), in (1) step during the black and white camera calibration, throw a kind of colorama to the target plate, this colorama is identical with one of background colour with target plate prospect.
2, the scaling method of object surface three-dimensional contour structure light measurement system according to claim 1 is characterized in that: described (3) step many plane references method be Tsai based on radial constraint unanimity (RAC) method.
3, the scaling method of object surface three-dimensional contour structure light measurement system according to claim 1 and 2 is characterized in that: the described projection of (5) step is colored to utilize projector to finish.
CNB200810019813XA 2008-03-17 2008-03-17 The scaling method of object surface three-dimensional contour structure light measurement system CN100573040C (en)

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