JPH0460524B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides an imaging means such as a television camera,
Measures geometric features, including distance from a predetermined position or angle of inclination, of an object with a square cross section or an equivalent pattern using an image processing device consisting of an image signal (video signal) arithmetic processing circuit. Regarding the measurement method.

[Conventional technology]

As a conventional measurement method of this type, the one shown in FIG. 6 is known as the simplest configuration.
In this example, the object to be processed 3 is imaged by a television camera 1, the image is processed by the arithmetic processing circuit 2, and the position of the object to be processed 3 is measured, for example, with respect to the origin on the screen of the camera 1. The object 3 is fixedly supported by a fixture 11 which is a holding means. Therefore, as shown in FIG. 7, the television camera 1 must include the entire part of the object to be processed 3 within its field of view 12. However, in this case, because the resolution of the television camera is low, the expected measurement accuracy is often not achieved.

Therefore, a device as shown in FIG. 8, which has a somewhat complicated configuration, is also known. In this case, the fixing jig 11 in FIG. 6 is replaced with an XY transport device 13. That is, the object to be processed 3 can be transported in both directions of two orthogonal axes. Therefore, by setting the field of view of the television camera 1 so that a part of the object 3 to be processed is included in the field of view, and repeating moving the XY conveyance device 13 while taking images, the object 3 to be processed can be sufficiently close-up and the resolution can be improved. Since this increases, the position measurement accuracy as described above is improved. For example, FIG. 9 sequentially shows the state of each field of view 12 when the entire part of the object to be processed 3 is covered by imaging four times. This is an example in which the object to be processed 3 is imaged in the order of upper right A, upper left B, lower left C, and lower right D.

[Problem that the invention seeks to solve]

However, in such a configuration, since the transfer device requires movement on two axes, it is mechanically complicated and large-scale, and there are problems in that the cost is high. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for measuring the position of an object, which has a small and simple configuration, is inexpensive, and can obtain good measurement accuracy.

[Means for solving problems]

An imaging means for imaging an object having a square cross section or a pattern substantially equivalent thereto, a driving means for relatively rotating the imaging means and the object, and a predetermined calculation based on an image signal from the imaging means. A processing means for performing the processing is provided.

[Effect]

The driving means rotates the relative angle between the object and the imaging means one rotation by a predetermined amount, and the imaging means divides and extracts one object image into predetermined parts. The position of each vertex of the object is determined by the processing means from the image information of demand.

〔Example〕

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
FIG. 2 is a perspective view showing an example of an object to be processed, FIG. 3 is a reference drawing showing an example of an image of a pin pattern, FIG. 4 is a reference drawing showing a partial extracted image of a pin pattern, and FIG.
The figure is a reference diagram for explaining a method for determining the position coordinates of the vertices of an object. In FIG. 1, 1 is an imaging device such as a television camera, 2 is an arithmetic processing circuit, 3 is an object, 4 is a rotating hand, 5 is an optical axis of the television camera 1, 6 is a central axis of the rotating hand, and 7
is the displacement V between the optical axis 5 and the rotating hand central axis 6. Further, as the object 3, an electronic component (such as an LSi) having a plurality of pins 31 regularly arranged in a square shape as shown in FIG. 2 is considered here.

The object 3 is held by suction by the rotating hand 4 and rotated. At this time, TV camera 1
The optical axis 5 of the rotary hand 4 and the central axis 6 of the rotary hand 4 are arranged so as to form a constant displacement 7, so that the origin on the screen of the camera 1 (for example, the lower left corner of the screen)
and the center axis 6 of the rotating hand. However, the object 3 is not necessarily held so that its center coincides with the center of the rotating hand 4, and deviations (Δx, Δy,
Δθ) occurs. In addition, in Fig. 3, P ₀ is the above origin, P _x is the center of the object 3, 31 is the pin image,
P ₁ to _{P 4} indicate the vertices of the pin pattern, and this is an example in which point P _x is shifted from point P ₀ by Δx and Δy. Note that Δθ is the inclination angle of the object with respect to the x-axis. Therefore, when an object having the relationship as shown in FIG.
Image data such as those shown in Figures A, B, C, and D are obtained. The arithmetic processing circuit 2 processes, for example, each vertex P ₁ ,
From the coordinate positions of P ₂ , P ₃ and P ₄ , Δx, Δy, Δθ and l (the length of the side of the square pattern) are determined using the following equations (1) to (4). Note that the position coordinates of each vertex can be immediately determined by image processing for objects with a square cross section, but for pin patterns (patterns equivalent to squares) as shown in Figure 2, they can be determined directly. In that case, the pin pattern is divided into four groups, the straight line that best fits each group is found by the method of least squares, and the intersection points of these straight lines are calculated.

l=√2/8(√( ₄₁ − ₂₃ ) ² +( ₄₁ − ₂₃ ) ² +√( ₁₂ − ₃₄ ) ² +( ₁₂ − ₃₄ ) ² ...(1) Δx=1/4(x ₄₁ +x ₂₃ +x ₁₂ +x ₃₄ ) ...(2) Δy=1/4 (y ₄₁ +y ₂₃ +y ₁₂ +y ₃₄ ) ...(3) Δθ=1/2 (tan ^-1 (-x ₄₁ +x ₂₃ +y ₁₂ -y ₂₃ ) / x ₄₁ +
x ₂₃ +y ₁₂ −y ₂₃ +tan ^-1 x ₁₂ −x ₃₄ −y ₁₂ +y ₃₄ )／x ₁₂ −x ₃₄ +y ₁₂ −y ₃₄
)...(4) However, the vertex coordinates actually obtained from the image are 0°, 90°, 180°, and 270° in the order of A, B, C, and D in Figure 4.
rotation is added, so if the vertex coordinate values of each screen are (x _a , y _a ), (x _b , y _b ), (x _c , y _c ), (x _d , y _d ) in order, then Comparison with Figure 3 shows that x _a = x ₄₁ , y _a = y ₄₁ x _b = -x ₁₂ , y _b = y ₁₂ x _c = -x ₂₃ , y _c = -y ₂₃ x _d = x ₃₄ , y The relationship is _d = -y ₃₄ . Therefore, l, Δx, Δy, and Δθ can be rewritten as shown in the following equation.

l=√2/8(√( _a , _c ) ² + ( _a + _c ) ² +√( _b + _d ) ² + ( _b + _d ) ² ...(1)' Δx=1/4(x _a −x _c −y _b +y _d ) …(2)′ Δy=1/4(x _b −x _d +y _a −y _c ) …(3)′ Δθ=1/2(tan ⁻¹ −x _a −x _c +y _a +y _c /x _a +x _c +y _a +y
_c ＋tan ^-1 x _b ＋x _d ＋y _b ＋y _d ／−x _b −x _d ＋y _b ＋y _d ……(4)′ In other words, the arithmetic processing circuit 2 processes the object including the amount of deviation by performing the following processing. Measure the position of objects.

(1) The rotating hand 4 is rotated, for example, by 90 degrees to capture images a, b, c, and d of the objective 3.

(2) From each pin image, for example, use the least squares method to find the 4
Find straight lines and find the intersection of the four straight lines (x _a , y _a ),
Find (x _b , y _b ), (x _c , y _c ), (x _d , y _d ).

(3) Determine Δx, Δy, and Δθ (l if necessary) from the above equations (1)′ to (4)′.

In this way, highly accurate position measurement with increased resolution is possible. Therefore, the present invention drives the rotary hand by a drive system such as another robot, corrects the above deviations (Δx, Δy, Δθ) at a predetermined position, and mounts the electronic component on the printed circuit board. It is suitable for use in precision work such as Although the object is rotated by the rotary hand in the above example, it goes without saying that the object may be fixed and the imaging device may be rotated by some other method.

Furthermore, although the object is rotated by 90 degrees in Figure 4, the relative rotation rate between the object and the imaging device depends on the size of the object and the size of the field of view of the imaging device. It is determined. For example, the field of view 1 of an imaging device having a size as shown in FIG.
2, when the object 3 to be processed is imaged, if the object 3 is rotated by 90 degrees, there will be a portion that cannot be covered in the field of view. Therefore, by rotating the object 3 by 60 degrees as shown in FIGS. 10A to 10F, the entire part of the object 3 can be imaged six times.

Next, how to calculate the amount of deviation from the position coordinates of the vertices will be explained in detail.

The square formed by the pin pattern as shown in Fig. 3 has a straight line L 1 with an inclination tan Δθ passing through the point P ₅ Δx Δy + l-sin Δθ cos Δθ and a straight line L ₁ passing through the point P ₅ Δx Δy + l-cos Δθ/-sin Δθ as shown in the same figure. A square surrounded by a straight _{line L2} with a through slope of -cosΔθ, a straight line _L3 with a slope of tanΔθ passing through the point _P7ΔxΔy +lsinΔθ−cosΔθ, and a straight line _L4 with a slope of −cotΔθ passing through the point P8ΔxΔy+lcosΔθ sinΔθ. It can be written as That is, four straight lines L ₁ :y=tanΔθ[x-(Δx−lsinΔθ)]+(Δy+lcosΔθ) _L2 :y=−cotΔθ[x−(Δx−lcosΔθ)]+(Δy−lsinΔθ) _L3 :y= It is a square surrounded by tanΔθ[x−(Δx+lsinΔθ)]+(Δy−lcosΔθ) L ₄ :y=−cotΔθ[x−(Δx+lcosΔθ)]+(Δy+lsinΔθ).

Next, by setting x=0 in the equation for L ₁ , the y-intercept y ₁ of L ₁ is y ₁ = −tanΔθ・(Δx−lsinΔθ)+(Δy+lcosΔθ
) = -ΔxtanΔθ + Δy + lcosecΔθ Also, the x-intercept x ₂ of L ₂ can be obtained by setting y = 0 in the equation of L _{2, x 2 =} tanΔθ・(Δy−lsinΔθ) + (Δx−lcosΔθ) = ΔytanΔθ + Δx−lcosecΔθ Similarly, , the y-intercept y ₃ of L ₃ is set as x=0 in the equation of L ₃ , y ₃ = −tanΔθ・(Δx+lsinΔθ)+(Δy−lcosΔ
θ) = -ΔxtanΔθ+Δy−lcosecΔθ Similarly, the x-intercept x ₄ of L ₄ is set as y=0 in the equation of L 4, and x ₄ = tanΔθ・(Δy+lsinΔθ ₎ +(Δx+lcosΔθ
)=ΔytanΔθ+Δx+lcosecΔθ.

Next, to find the intersection point P ₂ (x ₁₂ , y ₁₂ ) of L ₁ and L ₂ , set L ₁ = L ₂ , tanΔθ[x ₁₂ −(Δx−lsinΔθ)] + (Δy+lcosΔθ)=−cotΔθ [x ₁₂ −(Δx−
lcosΔθ)] +(Δy−lsinΔθ) ∴(tanΔθ+cotΔθ)x ₁₂ = cotΔθ(Δx−lcosΔθ)+(Δy−lsinΔθ) +tanΔθ(Δx−lsinΔθ)−(Δy+lcosΔθ) = (tanΔθ+cotΔθ)Δx−lsecΔθcosΔθ−
lsinΔθ −ltanΔθsinΔθ−lcosΔθ = (tanΔθ+cotΔθ)Δx−lsecΔθ −lcosecΔθ ∴x ₁₂ =Δx−l(cosΔθ+sinΔθ) ∴y ₁₂ =tanΔθ [Δx−l(cosΔθ+sinΔθ) −(Δx−lsinΔθ)]+Δy+lcosΔθ =Δy+l(cosΔθ−sinΔθ ) ∴x ₁₂ y ₁₂ = Δx−l(cosΔθ+sinΔθ) Δy+l(cosΔθ−sinΔθ).

Similarly, the intersection point P ₃ (x ₂₃ , y ₂₃ ) of L ₂ and L ₃ , L ₃
The intersection point P ₄ (x ₃₄ , y ₃₄ ) between L ₄ and L ₄ and the intersection P ₁ (x ₄₁ , y ₄₁ ) between L ₄ and L 1 are determined by the following equations.

x ₂₃ y ₂₃ =Δx−l(cos′Δθ−sinΔθ) Δy+l(cosΔθ+sinΔθ) x ₃₄ y ₃₄ =Δx+l(cosΔθ+sinΔθ) Δy ₋ l(cosΔθ− _sinΔθ ) Δθ ) Note that FIG. 5 shows these points and their coordinate positions. Here, we will focus on the vertices P ₁ and P ₃ in the first and third quadrants. That is, x ₄₁ = Δx + l ( _cos Δθ ₋ sin Δθ) y ₄₁ = Δy + l (cos _Δθ + _sin Δθ) ∴Δx=1/2 (x ₄₁ +x ₂₃ ) y ₄₁ +y ₂₃ =2Δy ∴Δy=1/2 (y ₄₁ +y ₂₃ ). Also, since (x ₄₁ −x ₂₃ ) ² =4l ² (l−2cosΔθsinΔθ) (y ₄₁ −y ₂₃ ) ² =4l ² (1+2cosΔθsinΔθ), l is ∴l=1/4√2[( ₄₁ − ₂₃ ) ² + ( ₄₁ - ₂₃ ) ²
] becomes. Also, x ₄₁ −x ₂₃ /y ₄₁ −y ₂₃ = 2l(cosΔθ−sinΔθ)/2l(co
Since sΔθ+sinΔθ) = 1−tanΔθ/1+tanΔθ, ∴(x ₄₁ −x ₂₃ )(1+tanΔθ) =(y ₄₁ −y ₂₃ )(1−tanΔθ) ∴(x ₄₁ −x ₂₃ +y ₄₁ −y ₂₃ )tanΔθ =−x ₄₁ +x ₂₃ +y ₄₁ −y ₂₃ ∴Δθ=tan ^-1 −x ₄₁ +x ₂₃ +y ₄₁ −y ₂₃ /x ₄₁ −x ₂₃ +y ₄₁ −
y becomes ₂₃ . To summarize the above, l = 1/4√2 [( ₄₁ − ₂₃ ) ² + ( ₄₁ − ₂₃ ) ² ] Δx = 1/2 (x ₄₁ + x ₂₃ ) Δy = 1/2 (y ₄₁ + y ₂₃ ) Δθ = tan ^-1 −x ₄₁ +x ₂₃ +y ₄₁ −y ₂₃ /x ₄₁ −x ₂₃ +y ₄₁ −y _2
3 is obtained.

On the other hand, if the vertices P ₂ and P ₄ of the second and fourth quadrants are used, x ₁₂ = Δx−l(cosΔθ+sinΔθ) y ₁₂ =Δy+l(cosΔθ−sinΔθ) x ₃₄ =Δy+l(cosΔθ+sinΔθ) y ₃₄ =Δy− l(cosΔθ−sinΔθ), so first, x ₁₂ + x ₃₄ = 2Δx ∴Δx = 1/2 (x ₁₂ + x ₃₄ ) y ₁₂ + y ₃₄ = 2Δy ∴Δy = 1/2 (y ₁₂ + y ₃₄ ) . Also, (x ₁₂ - x ₃₄ ) ² = 4l ² (1 + 2cosΔθsinΔθ) (y ₁₂ - y ₃₄ ) ² = 4l ² (1-2cosΔθsinΔθ), so l is l = 1/4√2 [( ₁₂ - ₃₄ ) ² + ( ₁₂ − ₃₄ ) ² ]. Also, x ₁₂ −x ₃₄ /y ₁₂ −y ₃₄ = −2l(cosΔθ+sinΔθ)/2l(
cosΔθ−sinΔθ) = −1−tanΔθ/1−tanΔθ, so ∴(x ₁₂ −x ₃₄ )(1−tanΔθ) = (y ₁₂ −y ₃₄ )(−1−tanΔθ) ∴(x ₁₂ −x ₃₄ −y ₁₂ +y ₃₄ ) tanΔθ = x ₁₂ −x ₃₄ +y ₁₂ −y ₃₄ ∴Δθ=tan ^-1 x ₁₂ −x ₃₄ +y ₁₂ −y ₃₄ /x ₁₂ −x ₃₄ −y ₁₂ +y ₃
It becomes ₄ . To summarize the above, l=1/4√2 [( ₁₂ − ₃₄ ) ² + ( ₁₂ − ₃₄ ) ²
] Δx=1/2(x ₁₂ +x ₃₄ ) Δy=1/2(y ₁₂ +y ₃₄ ) Δθ=tan ^-1 x ₁₂ −x ₃₄ +y ₁₂ −y ₃₄ /x ₁₂ −x ₃₄ −y ₁₂ +y ₃₄ can get.

As above, from points P ₁ and P ₃ and points P ₂ and P ₄ ,
l, Δx, Δy, and Δθ can be determined independently. Therefore, if we take the average value to further improve the measurement accuracy, we can obtain the results (1) to (4) shown earlier.
This means that the formula or formulas (1)' to (4)' are obtained.

〔Effect of the invention〕

According to this invention, the object and the imaging means are rotated relative to each other, and one object image is divided into multiple parts for measurement, so it is smaller than the conventional orthogonal two-axis mechanism. This not only simplifies and lowers the cost, but also enables sufficient close-up (higher resolution) and further improves measurement accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention;
FIG. 2 is a perspective view showing an example of an object to be processed, FIG. 3 is a reference drawing showing an example of an image of a pin pattern, and FIG. 4 is a reference drawing showing an example of each partial extracted image of the pin pattern.
Fig. 5 is a reference diagram showing the position coordinates of each vertex of the object, Fig. 6 is a schematic diagram showing a conventional example of the position measurement method, Fig. 7 is a reference diagram showing the field of view of the television camera in Fig. 6, Figure 8 is a schematic diagram showing another conventional example of the position measurement method, Figure 9 is a reference diagram showing the field of view of the television camera in Figure 8, and Figure 10 is an explanatory diagram of the relative rotation of the imaging device and the object. be. Code explanation, 1...TV camera (imaging device),
2... Arithmetic processing circuit, 3... Target, 4... Rotating hand, 5... Optical axis, 6... Central axis of rotating hand, 7... Displacement, 11... Fixing jig, 12... Television Camera field of view, 13...XY transport device, 13
...XY transport device, 31...pin.

Claims (1)

[Claims] 1. An imaging means for imaging an object having a square cross section or a pattern equivalent thereto, a driving means for relatively rotating the imaging means and the object, and a predetermined calculation based on the image signal from the imaging means. processing means for performing processing, and by rotating the relative angle once by a predetermined number of degrees by the driving means, one object image is divided into predetermined parts and taken out via the imaging means, and each of the The processing means determines the position of each vertex of the object from the image information for each part, and performs a predetermined calculation based on the coordinates of the vertex position, thereby determining the amount of deviation of the object from a predetermined reference point and the predetermined standard. A method for measuring the position of an object, which is characterized by measuring the angle of inclination with respect to an axis.