JP2567923B2 - Distance measurement method - Google Patents

Description

The present invention relates to a measuring method for irradiating an object to be measured with slit light such as a laser to obtain a distance between a target surface of the object to be measured and a fixed point on an image pickup surface of a television camera. .

2. Description of the Related Art A typical prior art has a configuration in which a mechanical displacement position is converted into an electrical signal by a differential transformer using a contact type probe, and a shift amount is read.

In such a prior art, since the probe has a configuration of contacting the object to be measured, automation is difficult and the measurement work takes time.

Other prior arts are disclosed, for example, in JP-A-60-93424 and JP-B-62-26403, respectively. In these prior arts, the surface of the object to be measured is irradiated with slit light from a fixed position, and the slit light on the object to be measured is imaged by a camera.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Such a prior art uses a single slit light and does not disclose a configuration for measuring a distance.

An object of the present invention is to provide a distance measuring method capable of measuring a distance between a target surface of a measured object and an image pickup surface of a television camera in a non-contact manner.

Means for Solving the Problem The present invention irradiates a target surface P13, which is the surface 1 of an object to be measured, with two slit light beams 5 and 6 that intersect with each other, and cuts the slit light beams 5 and 6 on the target surface P13. In the method of capturing an image of a line on the imaging surface 8 of the television camera 7 and measuring the distance between the fixed point on the imaging surface 8 and the target surface P13, a line that passes through the principal point of the lens 9 of the television camera 7 and is perpendicular to the imaging surface 8. Is set as the Z axis, and the XYZ orthogonal coordinate system in which the image pickup surface 8 is the XY plane is set, and the image 30 of the light cutting line of one slit light 6 on the image pickup surface 8 and the plane P14 passing through the principal point of the lens 9, One slit light 6
From the normal vector with respect to the plane P15, the direction vector ₄ of the intersection of the planes P14 and P15 is obtained, and the plane P16 passing through the light cutting line 32 of the other slit light 5 on the imaging plane 8 and the principal point of the lens 9 is obtained. From the normal vector to the plane P17 of the other slit light 5, the direction vector ₈ of the line of intersection of the planes P16 and P17 is obtained, and from the direction vectors ₄ and ₈ the normal vector ₀ (s ₀ , t ₀ , 1) and find the point on the target plane P13 on the plane P1
4, P15, P17 intersections or planes P15, P16, P17 intersections (x ₀ , y ₀ ,
z ₀ ), and the distance d ₀ between the fixed point on the imaging surface 8 and the target surface P 13 is calculated by the following equation d ₀ = s ₀ x ₀ + t ₀ y ₀ + z ₀ Is the way.

Operation According to the present invention, the normal vector of the target surface ₀ = (s ₀ , t
₀ , 1) is obtained in a non-contact manner from the direction vector of the line of intersection between the two planes passing through the lines (X, Y axes) perpendicular to each other on the imaging surface and the lens principal point and the two planes of slit light. 2 passing through any one of the slit light planes and the lens principal point.
Since the intersection (x ₀ , y ₀ , z ₀ ) with two planes is on the target plane,
By using s ₀ , t ₀ , x ₀ , y ₀ , z ₀ , the distance between the fixed point (origin) on the imaging surface and the target surface can be quickly calculated by the above formula.

Embodiment FIG. 1 is a simplified perspective view of an embodiment of the present invention. A perfect circular hole 2 is formed to face a surface 1 which is a target surface of an object to be measured such as a work. Two slit lights 5 and 6 are emitted from the projectors 3 and 4 to the hole 2. The camera 7 and the two projectors 3 and 4 for irradiating the slit light are integrated. The slit light is a plane indicated by reference numerals 5 and 6, respectively. The light cutting line on the surface 1 of the object to be measured is missing in the hole 2, and these end points are referred to by reference symbols A, B,
Shown by C and D respectively. The surface 1 of the measured object is imaged by the industrial television camera 7. The camera 7 includes an image pickup surface 8 of a charge storage device (abbreviated as CCD) and a surface 1 of an object to be measured.
And a lens 9 for forming an image of each slit light beam on the imaging surface 8. Using the XYZ Cartesian coordinate system in which the imaging plane 8 is the XY plane, and the Z axis is a straight line that is perpendicular to the imaging plane 8 and passes through the principal point of the lens 9 of the camera 7, the point on the measured object surface 1 is (X, Y , Z), and the points on the imaging surface 8 are indicated by (Xc, Yc). The output from the camera 7 is given to the processing circuit 10.

FIG. 2 is a block diagram showing the electrical configuration of the embodiment shown in FIG. The projectors 3 and 4 are driven by drive circuits 11 and 12. The television camera controller 13 provided in the processing circuit 10 gives a synchronization signal to the image pickup surface 8 of the CCD via the line 14, and thereby processes the video signal imaged on the image pickup surface 8 via the line 15. It is given to the analog / digital conversion circuit 16 of the circuit 10 and converted into a digital value. The output from the analog / digital conversion circuit 16 thus obtained is compared with the threshold value which is the discrimination level from the threshold value setting device 17 in the comparator 18, and a binary signal is obtained from the line 19. . The binarized signal is stored in the frame memory 20. The contents of memory 20 are bus 21
Is provided to the processing means 22 via a communication controller
Data can be transferred to and from an external processing means via 23. In one embodiment of the present invention having such a basic configuration, first, the camera parameters are calculated, the equations of the two slit light planes are obtained, and then the inclination of the measured object surface 1, that is, the posture. The angle is calculated, and the distance between the measured object surface 1 and the camera 7 is measured.

I. Calculation of camera parameters As shown in FIG. 3, the slit light projector 3 and the camera 7 are arranged, and the coordinates of one point P on the slit light plane 5 are (X, Y, Z) and P. The coordinates of the image Q on the image plane 8 of (Xc, Y
c) The perspective transformation of the camera 7 is shown in the first equation.

The equation of the slit light plane 5 is shown in the second equation.

a * X + b * Y + Z = d (2) Therefore, the coordinates (X, Y, Z) of P are the first equation and the second equation.
It can be obtained by solving simultaneous equations. Basically,
The three-dimensional coordinates of all the points on the slit light plane 5 can be obtained. Similarly, the three-dimensional coordinates of all the points on the slit light plane 6 can be obtained.

C _{11 to} C ₃₄ in the first equation are called camera parameters. The camera parameter is a value determined depending on the focal length of the lens 9, the position of the principal point of the lens 9, the distance between the lens 9 and the light receiving surface, that is, the image pickup surface 8. Since it is difficult to measure these values, the following method is used.

Expanding the first equation and deleting the coefficient h, C ₁₁ * X + C ₁₂ * Y + C ₁₃ * Z + C ₁₄ −C ₃₁ * Xc * X−C ₃₂ * Xc * Y−C ₃₃ * Xc * Z−C
₃₄ * Xc = 0 (3-1) C ₂₁ * X + C ₂₂ * Y + C ₂₃ * Z + C _24- C ₃₁ * Xc * X-C ₃₂ * Xc * Y-C ₃₃ * Xc * Z-C
₃₄ * Xc = 0 (3-2). Therefore, 6 known points that are not on the same plane
The three-dimensional coordinates and the camera coordinates corresponding to the three-dimensional coordinates
By substituting the equations (1) and (3-2) and solving the 12-element simultaneous equations, 12 unknowns (C _{11 to} C ₃₄ ) can be obtained. Here, in order to improve the calculation accuracy of the camera parameters, three-dimensional coordinates are measured at known n points (n> 6) and are obtained by the least square method.

From the third equation, the following 12-element 2n simultaneous equations concerning the coefficients C _{11 to} C ₃₄ are obtained.

E * G = F (4) F = [Xc ₁ Yc ₁ ……………… Xc _n Yc _n ] ^t … (6) G ＝ [C ₁₁ C ₁₂ C ₁₃ C ₁₄ C ₂₁ C ₂₂ C ₂₃ C ₂₄ C ₃₁ C ₃₂ C ₃₃ ] ^t … (7
-1) However, _C34 = 1 ... (7-2) G = ( ^Et * E) ^-1 * ^Et * F ... (8) is calculated by the least squares method, G is calculated | required.

II. Calculation of the coefficients of the plane of slit light equation.

The second three-dimensional position of three known points on the plane of the slit light
By substituting in the equation, a three-dimensional simultaneous equation concerning a, b, d can be obtained, and by solving this, a, b, d can be calculated. Here, in order to improve accuracy, the known three-dimensional coordinates of n points (n> 3) are substituted into the second equation, and the following three-dimensional n simultaneous simultaneous equations are solved by the least squares method.

If this is written as J * K = L ... (10), it can be obtained from K = ( ^Jt * J) ^-1 * ^Jt * L ... (11). Similarly, the coefficient of the slit light surface 6 can be calculated.

III. Measurement of the posture angle α around the X axis and the posture angle β around the Y axis of the measured object surface, that is, the target surface P13.

In FIG. 4 (1), the target surface P13a is + around the X axis.
When it is angularly displaced by Δα to take the posture of the plane P13b, the light cutting line 26 on the target surface P13a of the slit light 5 is as the light cutting line 27 on the plane P13b. On the image plane 8 of the camera 7, the image of the light cutting line 26 at α = 0 is indicated by reference numeral 26a,
The image of the light section line 27 after its rotation is indicated by reference numeral 27a.
Further, as shown in FIG. 5 (1), when the target surface P13c is angularly displaced about the Y axis by an angle Δβ and becomes a plane P13d, the light cutting line 28 on the target surface P13c is illuminated on the plane P13d. It becomes the cutting line 29. Therefore, on the imaging surface 8 of the camera 7,
The image 28a of the light section line 28 becomes an image 29a of the light section line 29. In this way, the images 27a and 29a on the imaging surface 8 allow the target surface P13a and the plane P
The mutual angle Δα with 13b and the angle + Δβ between the target surface P13c and the plane P13d can be calculated and obtained. The definitions of Δα and Δβ are shown in FIGS. 4 and 5, and further in FIGS.
A method for obtaining the inclination of the plane will be specifically described with reference to FIG.

(1) In obtaining the posture angle α of the target surface P13 around the X axis and the posture angle β of the target surface P13 around the Y axis shown in FIG. 7, first, the H direction on the imaging surface 8 of the camera 7 is determined. The equation of the light cutting line 30 of the horizontal slit light is obtained in advance, and from the equation of the light cutting line 30 and the previously obtained camera parameters C _{11 to} C ₃₄ , the light cutting line 30 and the lens 9 are obtained. Find the equation of plane P14 passing through the principal points of (6th
(Steps m1, m2 in the figure). Also, the equation of the plane P15 of the slit light 6 is obtained by II (step m in FIG. 6).
3).

(2) The equation shown in the previous paragraph (1),
When the camera parameters and Niyotsute obtains the vector of each plane of the planes P14, P15, the normal vector _2,
3 and the direction vector of the intersection 31 of the planes P14 and P15 is ₄ (1, t ₄ , u ₄ ) ... (12), ₄ and ₂ and ₃ are orthogonal, so ₂ · ₄ = 0. Thus ₍₁₃₎ 3 _- 4 = 0 ... _{(14), 4} are obtained (in FIG. 6 step m
Four).

(3) Similarly, from FIG.
And the vertical direction, that is, the optical cutting line 32 of the vertical slit light in the V direction and the equation of the plane P16 from the camera parameters,
The equation of the plane P17 of the slit light 5 is obtained by II, and the normal vectors of the planes P16 and P17 are ₆ and ₇ , respectively, and the plane P1.
6, a direction vector of the P17 lines of intersection _33, 8 = (s _8, 1, u ₈₎ as _(15), so orthogonal to the ₈ and _{6, 7,} 6 _& 8 = 0 ... _{(16) 7}・₈ = 0 (17) As a result, ₈ is obtained (step m in FIG. 6).
7).

(4) the normal vector ₀ = the target surface P13 (s _0, t _0, 1) ... (18) is because orthogonal to _{4, 8, 0,} 4 = 0 ... ₍₁₉₎ 0 _· 8 = 0 ... ( 20) From this, ₀ is obtained (step m in FIG. 6)
8).

The attitude angles α (horizontal axis, rotation angle around the X axis) and β (rotation angle around the Y axis) of the imaging surface 8 with respect to the target surface P13 are determined by the following equations (step m9 in FIG. 6).

α = tan ^-1 (t ₀ ) ... (21) β = tan ^-1 (s ₀ ) ... (22) IV. Distance measurement method.

As shown in FIG. 9, when measuring the distance between the plane P13e and the imaging surface 8 of the camera 7, if the plane P13e is displaced within a detectable range as shown by P13f and P13g, FIG. As shown in (2), the projector 3 is placed on the imaging surface 8.
The light cutting lines 34, 35, 36 of the slit light 5 are detected as images 34a, 35a, 36a. In this way, the image 34a on the imaging surface 8
By detecting 35a, 36a, the plane P13e, P13f, P13g
The distance of can be measured. This method will be described more specifically with reference to FIGS. 10 and 11.

(1) The equation of the optical axis of the camera 7 is x = y = 0 (23), and the fixed point (origin) on the imaging surface 8 and the target surface P13
The distance d between the optical axis of the lens 9 of the camera 7 and the target surface P13
It is defined as the Z coordinate of the intersection point of.

If the coordinates of one point on the target surface P13 are calculated, this and the target surface P
The equation of the plane of the target plane P13 can be determined from the 13 normal vectors. That point is plane P14, P15, P17 or plane P15, P
It is obtained as the intersection of 16, P17, and if that point is (x ₀ , y ₀ , z ₀ ), the equation of the target surface P13 is s ₀ (x−x ₀ ) + t ₀ (y−y ₀ ) +1 • (z−z ₀ ) = 0 (24) (steps r1 and r2 in FIG. 10).

(2) The distance d ₀ is obtained as d ₀ = s ₀ x ₀ + t ₀ y ₀ + z ₀ (25) (steps r3, r4 in FIG. 10).

EFFECTS OF THE INVENTION As described above, according to the present invention, the distance d ₀ between the fixed point on the image pickup surface of the television camera and the target surface, which is the surface of the object to be measured, can be quickly measured without touching the object to be measured. It becomes possible to ask.

[Brief description of drawings]

FIG. 1 is a simplified perspective view of an embodiment of the present invention, FIG. 2 is a block diagram showing an electrical configuration, FIG. 3 is a perspective view showing a method for calculating camera parameters, and FIG. 4 is a target surface. P13a
Showing the definition of the posture angle α of FIG. 5, FIG. 5 is a simplified diagram showing the definition of the posture angle β of the target surface P13c, and FIG. 6 is the posture angles α and β.
FIG. 7 and FIG. 8 are simplified flowcharts showing a method for measuring the posture angle α around the X axis and the posture angle β around the Y axis of the target surface P13.
FIG. 9 is a simplified diagram showing the principle of measuring the distance of the planes P13e, P13f, P13g, FIG. 10 is a flow chart showing the procedure for calculating the distance d ₀ of the plane, and FIG. 11 is measuring the distance d ₀ . It is a figure which simplifies and shows the structure for. 1 ... Surface of object to be measured, 2 ... Hole, 3,4 ... Projector of slit light, 7 ... Camera, 8 ... Imaging surface, 9 ... Lens, 10 ... Processing circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masaaki Hirayama 1-1 Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries Ltd. Akashi Plant (72) Inventor Yasuo Nakano 1-1, Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries, Ltd. Akashi Plant (72) Inventor Hideaki Mizuno 1-1 Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Akashi Plant (72) Inventor Ken Koike 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries, Ltd., Akashi Plant (72) Inventor, Hobu Isobe 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Kawasaki Heavy Industries, Ltd., Akashi Plant (56) Reference JP 62-272106 (JP, A) Kai 60-200111 (JP, A) JP 60-183509 (JP, A)

Claims (1)

(57) [Claims] 1. A target surface P13, which is the surface 1 of an object to be measured, is irradiated with two slit lights 5 and 6 intersecting each other, and a cutting line of each slit light 5 and 6 on the target surface P13 is taken by a television camera 7. In the method of measuring the distance between a fixed point on the imaging surface 8 and the target surface P13 by imaging on the imaging surface 8, a line perpendicular to the imaging surface 8 as the principal point of the lens 9 of the TV camera 7 is set as the Z axis, and the imaging is performed. An XYZ orthogonal coordinate system with the surface 8 as the XY plane is set, and the image 30 of the light cutting line of one slit light 6 on the imaging surface 8 and the plane P14 passing through the principal point of the lens 9 and one slit light 6 are set. From the normal vector to the plane P15, the direction vector ₄ of the line of intersection of the planes P14 and P15 is obtained, and the light cutting line 32 of the other slit light 5 on the imaging plane 8 and the plane P16 passing through the principal point of the lens 9 are obtained. , The plane P of the other slit light 5
The direction vector ₈ of the line of intersection of the planes P16 and P17 is obtained from the normal vector with respect to 17, and the normal vector ₀ (s ₀ , t ₀ , 1) of the target plane P13 is obtained from the direction vectors ₄ and ₈ A point on the plane P13 is a plane P14,
The intersection of P15, P17 or the intersection of planes P15, P16, P17 (x ₀ , y ₀ ,
z ₀ ), and the distance d ₀ between the fixed point on the imaging surface 8 and the target surface P 13 is calculated by the following equation d ₀ = s ₀ x ₀ + t ₀ y ₀ + z ₀ Method.