JPH0196505A - Measuring instrument for three-dimensional object - Google Patents

Abstract

PURPOSE:To quickly calculate which part of an object has been irradiated by laser slit light and to measure a three-dimensional coordinate with high accuracy by providing an address detecting circuit, a slit center calculating circuit and a polynomial converting circuit. CONSTITUTION:A laser beam 2 which has been emitted from a laser oscillator 1 passes through a focusing lens 3 and inputted to a scanner 4, converted to a slit light and projects an object 6, and photographed by a CCD camera 7. Thereafter, its video signal is converted 8 t a digital signal, stored in an image memory 9 by a command of a CPU 12, and simultaneously, inputted to an address detecting circuit 10, and at every one horizontal scan, an address at the time when image information is maximum is detected. Subsequently, this address information is inputted to a slit center calculating circuit 11, and a center position of a slit light image is calculated by using the image information of + or -(m) picture elements centering around a picture element shown by this address. In such a way, a three-dimensional space coordinate of a part to which the slit light on the object 6 can be calculated from the center position of the slit light image which has been calculated by the circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a three-dimensional object measuring device that measures the amount of movement or shape of a target object in a non-contact manner.

2. Description of the Related Art A conventional three-dimensional object measuring device, as shown in FIG.
After narrowing down the beam diameter, the scanner 4 illuminates the target object 6 in a slit shape, the target object 6 is photographed by the video camera 7, and the video signal is sent to the A/D converter 8.
After converting the image information into digital image information, this image information is stored in the image memory 9, and the 0PU12 converts the image information into digital image information.
Calculate the coordinates of the center of gravity while reading the image information of
After that, three-dimensional coordinates were calculated using the principle of triangulation based on the value of the center of gravity coordinates. Particularly recently, with the progress of semiconductor technology and because of its good stability, CCD cameras have been increasingly used as a means of photographing objects.

Generally speaking, for three-dimensional object measuring devices, how to accurately measure the three-dimensional coordinates of a target object is an important issue. Therefore, in order to improve the accuracy of coordinate measurement in the configuration shown in FIG. 8, the accuracy of detecting the barycentric coordinates of the slit image in the video signal from the camera must be made sufficiently high.

Problems to be Solved by the Invention However, when detecting the center of gravity coordinates using a CCD camera with the configuration shown in Fig. 8, there is a space on the CCD board, which is the imaging surface of the camera, as shown in Fig. 9 (a). The windows of the light receiving section 91 are arranged at intervals. Therefore, no light can be felt between the light receiving parts, and the laser slit light image 9
The video signal No. 2 is not continuous, and is given as a partial integral value (shaded area) 93 of the light intensity, as shown in FIG. 9(b).

Discrete image information on this CCD element, that is, brightness value (D
When calculating the center of gravity (Equation (1)) using As shown, the calculation result of the center of gravity position of the slit light image is not a continuous straight line, but a discontinuous curve 94 between the CCD elements, and a large error periodically occurs in the calculation of the center of gravity. Incidentally, the variance of the error from the straight line 95 indicating the true center of the slit optical image was 0.14 pixels in the example shown in FIG.

In addition, when three-dimensional coordinates were measured on the curved surface of the cylindrical object 6 as shown in FIG. 8 using a conventional three-dimensional object measuring device that uses gravity center calculation, the results are shown in FIG. 11. was gotten. In Figure 11, the three-dimensional coordinate measurement results are plotted on the Y-Z plane.
20mm) The arcuate portion of the side surface is not a smooth curve, but has a step. In order to solve the above problem, the present invention converts the video signal output from the imaging means into an A/D converter, and converts this image information into an image. address information detection means for detecting the maximum value of image information for each horizontal scan at the same time as storing it in the memory, and detecting the address information of the image memory indicating this maximum value; It is composed of a slit center calculation means for calculating the center position of a slit light image using a multiple regression model with N pieces of image information as variables, and a three-dimensional space coordinate calculation means.

Effect of the Invention With the above configuration, the present invention quickly and accurately detects where on the target object the slit light is hitting, and measures the three-dimensional spatial coordinates of the target object from the detection results.

Embodiment FIG. 1 is a block diagram showing an embodiment of the three-dimensional object measuring device of the present invention. In FIG. 1, 1 is a laser oscillator, 2
A laser beam emitted from the laser oscillator 1, 3 a focusing lens for focusing the laser beam 2, and 4 a scanner for converting the focused laser beam into a slit shape and deflecting the slit light. , 5 is a slit light,
6 is a target object whose shape is to be measured, 7 is a CCD camera for photographing the moat object 6, and 8 is for converting the video signal of the target object 6 photographed by the CCD camera 7 into t-bit digital image information. An A/D converter, 9 is an image memory for storing image information converted by the A/D converter 8, and 10 is a memory for storing the maximum value of the image information converted by the A/D converter in one horizontal scan. an address detection circuit for finding and detecting address information indicating its maximum value;
11 is a slit center calculation circuit that calculates the center of a slit optical image using a multiple regression model with image information of ±m pixels centered around the pixel with the maximum value and address information indicating the maximum value as variables; 12 is a slit center The three-dimensional coordinates of the target object 6 are calculated using the values obtained by the calculation circuit 11, and the device is controlled by a CPU memory 5 cpu, 13 a CPU memory for storing instructions and data of the 0PU 12, and an image memory 9 14. A CRT controller is used to output stored image information to a monitor, 15 is a monitor, and 16 is a scanner control circuit for controlling the scanner 4.

The operation will be explained below. A laser beam 2 emitted from a laser oscillator 1 passes through a focusing lens 3 and is input into a system scanner 4 . The scanner 4 has a function of converting a focused laser beam into slit light using a cylindrical lens or the like, and deflecting the slit light using a galvanometer mirror or the like.

The slit light 5 output from the scanner 4 is irradiated onto a target object 6. This target object 6 is photographed with a CCD camera 7. The video signal output from the CCD camera 7 is an A/D
The converter 8 converts it into a t-bit digital image signal. The image signal output from the A/D converter 8 is stored in the image memory 9 according to a command from the 0PU 12, and at the same time is input to the address detection circuit 10, which detects the address when the image information is maximum for each horizontal scan. . −
FIG. 2 shows the contents of the image memory 9. As shown in the figure, it consists of horizontal pixels, vertical V pixels, and t bits for each pixel, and the horizontal address is 1 (i=1
~h), and the vertical address is represented by j (j=t~V). This image memory 9 has visual field information of the CCD camera 7 arranged two-dimensionally.
It corresponds to each 00D element. Note that address 1 in the horizontal direction is used by the address detection circuit 10 and the slit center calculation circuit 11.

FIG. 3 is a block diagram showing the address detection circuit 10 in more detail. In the figure, 100 is a comparator for comparing input image information, 101 is a register that holds the input image information only when the newly input image information is larger as a result of comparing the image information. 102
103 is a register that holds an address indicating the input image information only when the newly input image information is larger as a result of comparing the image information in the same manner as the register 101;
104 and 105 are circuits that set a range for checking whether the address information output from the register 102 is a value suitable for calculating the slit center position; A comparator 106 is used to check whether the comparators 104 and 1
This is a gate for ORing the outputs of 05.

The operation will be explained below. Normally, the register 101 and the register 102 are reset to '0' during the horizontal blanking period. According to a command from the 0PU 12, the image information output from the A/D converter 8 is stored in the image memory 9 and at the same time The signal is input to the detection circuit 10.

In the address detection circuit 10, a comparator 100 compares the image information input for each pixel with the output of the register 101, and only when the input image information is large, the comparator 100 outputs a signal. The register 101 holds image information, and the register 102 holds address information indicating the image information held in the register 101.

Therefore, when the -horizontal scan ends, the register 102 has the following information:
Address information of the pixel with the largest value among the input image information is held.

The output of register 102 is input to comparators 104 and 105 to check whether the detected address is within a predetermined range. For example, when calculating the center position of a slit light image using image information of ±m pixels centered around the pixel indicated by this address, the address Ai detected here is:
Set the horizontal address of the image memory 9 to 1 (i=1 to h)
Then, 1+m≦Ai≦h −m ・
・−・−・(2) must be in a range that satisfies the above formula (2).

As a result, if the detected address is outside the range shown by equation (2), a signal is output from the gate 106, and the calculation of the slit center position and three-dimensional coordinates is not performed, as will be described later. Note that the address information output from the register 102 is input to the slit center calculation circuit 11.

When the address detector 10 detects the address information when the image information is maximum for each -horizontal scan, this address information is input to the slit center calculation circuit 11 during the horizontal blanking period, and the pixel indicated by this address is 10m in the center
Using the image information of the pixels, the center position of the slit light image is calculated for each -horizontal scan.

To calculate the center position, a multiple regression model (
Equation (2)) is used. In this embodiment, a regression model up to the third-order term is used, and a case will be described using image information of a total of three pixels, m=1, that is, a pixel showing the maximum value and pixels on both sides thereof.

Gj = I +Bo+B* Ih+B* Dl”+
BD-"+B4DO+BBDo+B@DO + B?Dt+ Bs D, i+ B@Dz...(
2) l Bo=B-...Preset coefficient J FIG. 4 is a block diagram showing the slit center calculation circuit 11 in more detail. In the same figure, 110
111 is a counter that indicates the address of the image memory 9; 112 is a subtracter for subtracting m from the address detected by the address detection circuit 10; 112 is a counter that indicates the address of the image memory 9; a switch circuit for selecting 113. 114° and 115 are polynomial conversion circuits A, B, and C!, respectively. 116 is an adder that adds the address information and the value of the register 117;
8 is an adder circuit for adding the output of the adder 116 and the output from the polynomial conversion circuit, and 119 is a memory for storing the result of the adder circuit.

The operation will be explained below. The address of the pixel showing the maximum value on the horizontal scan detected by the address detector 10 is
It is input to a subtracter 110. A subtracter 110 subtracts m from the address detected by the address detector and loads the result into a counter 111. The output of the counter 111 is an address of the image memory 9, and the output value is updated every time a clock is input. That is, based on this value, the maximum value in one horizontal scan and the image information of m pixels before and after the maximum value are read out from the image memory 9, and are inputted to each polynomial conversion circuit via the switch circuit 112.

Polynomial conversion circuit A113. B114. C! 11
5, the value of the polynomial with the input image information as a variable is (3), and the image information (D,) of the pixel on the left of the pixel showing the maximum value is sent to the polynomial conversion circuit A, and the value of the polynomial on the right is The image information (D2) of the pixel is input to the polynomial conversion circuit C, and the image information (Dl) of the pixel indicating the maximum value is input to the polynomial conversion circuit B. Therefore, the coefficients BKm, BK in each polynomial conversion circuit
The values of t, &m are respectively B, , Ba, and Be in the polynomial conversion circuit A113, and B1 . Bt, B-, and BeO values are set respectively for C115.

Further, the address information (, I > detected by the address detection circuit 10 is input to the adder 116, and is input to the register 117
is added to the value of coefficient B set in , and the addition result is output to the addition circuit 118. The addition circuit 118 sequentially adds the outputs of the adder 116 and each polynomial conversion circuit, and stores the final addition result, that is, the central coordinate value Gj of equation (2) in the memory 1.
19 to be memorized.

Here, the polynomial conversion circuit will be explained in more detail using the block diagram of the polynomial conversion circuit B shown in FIG.

In the figure, 120. 121. 122. 125
and 127 are multipliers, and 124 and 129 are adders. Also, 123, 126, and 128 are registers, and the (
2) B1. which is the coefficient of equation. Bt and B- are set in advance. 130 is a clock that takes the timing of addition. Regarding polynomial conversion circuits A and C, the above coefficients B, ~B, are 84 ~B・and B?, respectively. ~Bs, but the other configurations are the same.

The operation will be explained below. The image information (Dl) input to the polynomial conversion circuit B is transmitted to the multiplier 12o1 and the multiplier 121
2 and input to multiplier 122 .

The multiplier 120 multiplies the image information by the value of the coefficient B+, which is set in the register 123 in advance, and outputs the result to the adder 124. In this circuit, calculation of the first term (B, D,) of equation (3) is first completed.

Next, a multiplier 121 squares the image information and outputs the result to a multiplier 125 and a multiplier 122. In the multiplier 125,
Coefficient B2 and multiplier 1 which are set in register 126 in advance
21 and outputs the result to the adder 124. The adder 124 includes a multiplier 120 and a multiplier 125.
The respective outputs are added and output to adder 129.

The circuit described above completes the addition of the first and second terms of equation (3).

Then, the multiplier 122 multiplies the output of the multiplier 121 by the image information, that is, the value obtained by raising the cube of the image information to the multiplier 122.
Output to 27. In the multiplier 127, the register 12
The coefficient B3, which is set to 8, is multiplied by the output of the multiplier 122, and the result is output to the adder 129. Adder 12
At step 9, the output of the adder 124 and the output of the multiplier 127 are added and output to the outside of the circuit.

At this time, each adder has a timing clock 130
The operation is controlled by

With the above operations, the calculation of the polynomial of equation (3) is completed, and the center coordinate value of the slit light image for each horizontal scan of equation (2) is calculated within the slit center calculation circuit 11.

The above processing is performed during the horizontal blanking period.

Therefore, when a laser slit image is captured in response to a command from the 0PU 12, the slit center coordinates for each horizontal scan are stored in the memory 119. After that, C
Upon receiving the laser slit light capture end signal, the PU 12 reads out information from the memory 119 and calculates the three-dimensional coordinates of the target object 6 using the principle of triangulation. When this calculation is completed, the 0PU 12 issues a command to the scanner control circuit 16 to move the slit light and repeat the above process.

Note that the OR gate 106 in the address detection circuit 10
outputs a signal, that is, when the detected address is outside the range, the memory 1 in the slit center calculation circuit 11
A specific value is stored in 19 by a selection circuit (not shown), and when the CPU 12 detects this value, it does not calculate the three-dimensional coordinates.

With the above configuration and operation, when the center coordinates of the laser slit light as shown in FIG. 9(a) are calculated in the same way as in the conventional example, the coordinates of the center of the laser slit light as shown in FIG. 6 are compared to the conventional example in FIG. As such, the error is greatly reduced, and a nearly continuous straight line 61 is obtained. The variance of the error between the obtained center coordinate value and the straight line 62 indicating the true center position of the slit image is 0.04 pixels, which is about 1/1 of the conventional value of 0.14 pixels in the example.
The error can be reduced to 4. Therefore, since the three-dimensional coordinates of the target object are calculated based on this central coordinate value, the measured values of the three-dimensional coordinates can also be calculated with much higher precision than in the past.

FIG. 7 shows the results of three-dimensional coordinate measurement of the curved surface of the cylindrical object 6 as shown in FIG. 1 using the three-dimensional object measuring device of the present invention having the above configuration. . In Figure 7, the three-dimensional coordinate measurement results are plotted on the Y-Z plane, and the arc portion of the side surface of the cylinder (X 120 nun) appears as a step-like broken line like the conventional example shown in Figure 11. In comparison, a very smooth curve 71 is obtained, and it is clear that three-dimensional coordinates can be measured with higher precision than in the past. Note that the error variance during this measurement can be reduced to about 1/4 compared to the conventional example.

In addition, in this example, since the laser slit light is narrowed down by a focusing lens, the number of pixels used for center calculation can be ±1 pixel around the pixel showing the maximum value, a total of 3 pixels. It is not necessary to calculate the center of gravity using all pixels, and calculation time can be shortened.

Note that the A/D converter 8 is an 8-pit one, and the values of the coefficients Bo to B of equation (2) set in the 10 registers in the slit center calculation circuit are Bo = -2,678, respectively. B, = 0.032 Bt = -0,063 B3 = 0.078 B4 = -2,823X 10 BB = 6283 x 16° [3g = -5,482X xc B = 6.496 , 156×10 B·=1.528× 10 . These coefficients are set optimally according to the target object and measurement environment. When determining the coefficients, before measuring the three-dimensional coordinates, obtain a laser slit image as an inclined line whose true center position is known as shown in Figure 6, and use equation (4), which is a modification of equation (2). is obtained for each horizontal scan line. In this example, the coefficient 13o-B@ was determined by the least squares method using these plural equations (4).

Yi=GJ I=Ba+BiDm+B2Dz+BxD
++B-DO+BsDO+B-DO 1ByD*+BaDt+B*Dt - (4) The slope line used here is CC, which is the imaging surface of the CCD camera.
On the DCD substrate plate, the image of the slit light needs to be a straight line that is inclined with respect to the arrangement of the CCD elements, and is not parallel to the horizontal and vertical axes of the imaging plane. The multiple regression model used in the present invention is very effective for interpolation when sampling of data at the light receiving section is discontinuous, as shown in FIG. 9(a), for example, and the coefficients of the multiple regression model (Partial regression coefficient) can also be determined simply by imaging the slit light in a state where data sampling is discontinuous, such as the above-mentioned slope line.

Furthermore, in the multiple regression model used in this example, an approximation formula up to the third-order term was used with ±1 pixel centered on the pixel showing the maximum value, but these values do not limit the present invention. Even if these values are increased or decreased due to limitations in accuracy or hardware configuration, this does not depart from the spirit of the present invention.

Effects of the Invention As described above, according to the present invention, by providing a relatively simple circuit configuration of an address detection circuit, a slit center calculation circuit, and a polynomial conversion circuit, it is possible to determine where on the target object the laser slit light is hitting. can be calculated quickly and with high precision, and therefore three-dimensional coordinates can be measured with high precision, and the extremely large effect of reducing the variance of measurement errors to about 1/4 of that of conventional methods can be achieved. .

[Brief explanation of the drawing]

Fig. 1 is a block wiring diagram of a three-dimensional object measuring device according to an embodiment of the present invention, Fig. 2 is a conceptual diagram showing the storage state of an image memory, which is the main part of the device, and Fig. 3 is an address detection circuit of the same device. 4 is a block diagram of the slit center calculation circuit, FIG. 5 is a block diagram of the polynomial conversion circuit B, and FIG. 6 is a calculation result of the center position of the slit image in an embodiment of the present invention. , FIG. 7 is a diagram showing the three-dimensional coordinate measurement results of the curved surface of a cylindrical object in an embodiment of the present invention, FIG. 8 is a block diagram of a conventional three-dimensional object measuring device, and FIG. 9 is a CCD In the device light receiving model diagram, (a) is an overview diagram, (b) is a cross-sectional view along the scanning line, Figure 10 is a diagram showing the calculation results of the center of gravity of the slit image in the conventional example, and Figure 11 is the same three-dimensional diagram. FIG. 3 is a diagram showing the results of three-dimensional coordinate measurement of a curved surface portion of a cylindrical object using an object measuring device. 1... Laser oscillator, 3... Focusing lens, 4...
Scanner, 5... Slit light, 6... Target object, 7
...CCD camera, 8...A/D converter, 9.
...Image memory, 10...Address detection circuit, 11.
...Slit center calculation circuit, 12...CPU, 113
・114・115...Polynomial conversion circuit. Name of agent Patent attorney Satoshi Nakao and 1 other person No. 1
Fig. 2 Fig. 3 Fig. 4,..., Junkoho Fig. 6 Mizuko side + position Fig. 7 -→2 Fig. 8 Fig. 10 Horizontal drawing device Fig. 1I Fig. 111) 7J-

Claims (5)

[Claims] (1) A light conversion means for condensing the light emitted from the light emitting means and converting it into a slit shape, a deflection means for irradiating the slit light onto the target object and deflecting the slit light, and an imaging means for photographing an image of the slit light; an A/D converter for quantizing a luminance signal output from the imaging means; and a storage means for storing image information converted by the A/D converter. and address detection means for detecting a maximum value from among the image information for each horizontal scan of the imaging means and detecting address information of the storage means indicating the maximum value; slit center calculation means for calculating the center position of the slit light image using image information of N pixels on the horizontal scan including pixels of the imaging means; and the slit light image calculated by the slit center calculation means. and a three-dimensional spatial coordinate calculation means for calculating the three-dimensional spatial coordinates of a region on the target object onto which the slit light is projected from the center position of the inputted N pieces of said slit light. A three-dimensional object measuring device that calculates the center position of the slit light image using a multiple regression model using image information and address information of the pixel showing the maximum value as variables. (2) According to claim 1, the N pixels around the pixel showing the maximum value are ±m pixels centered around the pixel showing the maximum value, for a total of 2m+1 pixels. 3D object measuring device. (3) The three-dimensional object measuring device according to claim 1, wherein the imaging means is a two-dimensional CCD camera. (4) The three-dimensional object measuring device according to claim 1, wherein the light emitting means is a laser oscillator. (5) The partial regression coefficient of the multiple regression model used by the slit center calculation means is calculated by capturing a plurality of slit light images on the imaging surface of the imaging means in a straight line state that is not horizontal or vertical before measurement. The three-dimensional object measuring device according to claim 1, wherein the best unbiased estimated value is determined by the least power method based on the image information corresponding to the horizontal scanning line and the straight line equation of the slit light image. .