JPH0843041A - Method and apparatus for measuring three-dimensional shape - Google Patents

Abstract

PURPOSE:To stabilize a Z-axis control system and measure at a high velocity with high accuracy when a three dimensional shape of an object to be measured is measured with the use of a non-contact displacement sensor. CONSTITUTION:At least two displacement sensors 4 and 5 are set to Z-axis 3 of a triaxial moving mechanism 10. While the sensors 4 and 5 are continuously scanned within X-Y plane on an object 20 to be measured, a distance in Z direction is measured for every measuring point set beforehand. Outputs of the displacement sensors are taken into a data-processing device 16, where an inclination of the object 20 is obtained. An optimum control condition for the Z axis is determined from the obtained inclination and a scanning speed. The height of the Z-axis is controlled to be constant under the optimum control condition. Z coordinate and, X and Y coordinates of the measuring point at the time are synchronously stored in a memory device 18, thereby, three dimensional shape of the object is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning type three-dimensional shape for measuring a three-dimensional shape of an object to be measured placed on a surface plate constituting an XY plane while continuously scanning it in a non-contact manner. The present invention relates to a measuring method and device.

[0002]

2. Description of the Related Art There are the following conventional three-dimensional shape measuring methods.

The first method is a combination of a contact type displacement sensor and a three-axis moving mechanism.
While scanning in the plane, when the X and Y coordinates of the touch sensor reach a predetermined position, the X and Y movements are temporarily stopped, then the touch sensor is lowered in the Z direction, and the tip of the touch sensor is measured. This is a method of reading the coordinate values of the three-axis moving mechanism when it comes into contact with the surface and obtaining the three-dimensional coordinates of X, Y, Z of one measurement point. However, this method has a drawback that it takes a long time to measure because it is necessary to stop the movement of X and Y at a predetermined measurement point and repeat the descent in the Z direction, and continuous measurement cannot be performed.

The second method is a combination of a non-contact type displacement sensor and an X, Y bi-axial moving mechanism. While the displacement sensor continuously scans in the XY plane, a predetermined X,
This is a method of reading the output of the displacement sensor at the Y coordinate and obtaining the X, Y, Z coordinates of the object to be measured. Since this method is non-contact and continuous measurement, the measurement time can be shortened, but there is a problem that it cannot be applied to an object to be measured having a height difference exceeding the measurement range of the displacement sensor.

In the third method, a non-contact displacement sensor is attached to the Z axis of the X, Y, Z triaxial moving mechanism, and the Z axis is controlled so that the output of this displacement sensor becomes constant. By detecting the position of the axis with an encoder or the like, the Z coordinate at a predetermined X, Y coordinate is obtained, and the X, Y, Z of the object to be measured is obtained.
It is to find the coordinates. However, this method causes a so-called servo delay when the moving speed of the X and Y axes is high, or when the shape of the object to be measured is complicated and the unevenness is severe.
The control of the Z axis does not follow well, it becomes difficult to make the output of the displacement sensor constant, and there is a problem that an accurate Z coordinate cannot be obtained.

The fourth method is a combination of the second method and the third method, as shown in Japanese Patent Laid-Open No. 2-311705, in which Z is used to keep the output of the non-contact displacement sensor constant. The axis is controlled, the position of the Z axis at this time is detected by an encoder, etc., and the output of the displacement sensor is also detected at the same time, and the values of both are added to eliminate the error due to the servo delay. is there. However, even with this method, when the shape of the object to be measured changes in the positive direction or the negative direction of the Z axis in the same direction, the servo delay accumulates and eventually exceeds the measurement range of the displacement sensor. Further, in order to avoid this, if the moving speed of the Z-axis in the axial direction is increased, the control becomes too sensitive, causing a problem that vibration or oscillation of the Z-axis control system occurs.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and the non-contact displacement sensor is continuously scanned in the XY plane, and Z
An object of the present invention is to provide a three-dimensional shape measuring method and apparatus capable of measuring the three-dimensional shape of an object to be measured at high speed and with high accuracy without causing control delay of the axis and vibration and oscillation of the Z-axis control system. I am trying.

[0008]

The three-dimensional shape measuring method according to the present invention is characterized by including the following steps (1) to (5). (1) At least two non-contact displacement sensors attached to the Z-axis of the three-axis moving mechanism are continuously scanned in the XY plane, and one displacement sensor is set at a preset measurement point. Each time when the two match, measuring the distance in the Z direction to the object to be measured by the displacement sensor,
(2) A step of obtaining the inclination of the object to be measured from the two distances in the Z direction measured in the step, (3) Optimizing the Z axis from the preset scanning speed and the inclination of the object to be measured obtained in the step. Different control conditions, (4) controlling the Z axis by the optimum control conditions determined in the process so that the height from the object to be measured is constant,
(5) A step of calculating a three-dimensional shape of the object to be measured from the Z coordinate and the X and Y coordinates of the measurement point when the height of the Z axis is controlled to be constant in the step.

The three-dimensional shape measuring device used in the measuring method of the present invention is attached to the Z-axis of a three-axis moving mechanism,
At least two non-contact type displacement sensors for measuring the distance in the Z direction to the object to be measured, a positioning control device for the three-axis moving mechanism, and an inclination calculation for obtaining the inclination of the object to be measured from the output of the displacement sensor. Means, a control condition determining means for determining the optimum control condition of the Z axis from the determined inclination of the measured object and a preset scanning speed, and the Z axis from the measured object according to the determined optimum control condition. Data processing device having control means for controlling the X-axis to be constant, and a storage device for storing the X, Y and Z coordinates of the displacement sensor and the positioning control device when the height of the Z-axis is controlled to be constant. It is characterized by having and.

[0010]

According to the present invention, at least two non-contact type displacement sensors are arranged at a constant distance in the scanning direction Z.
These displacement sensors are attached to the X
-While continuously scanning in the Y plane, when one of the displacement sensors coincides with a preset measurement point, by measuring the distance in the Z direction to the object to be measured by these displacement sensors, The size and direction of the inclination of the DUT can be known. Inclination of this object (size and direction of inclination)
By detecting and predicting for each measurement point, the height of the Z axis from the object to be measured can be kept constant. That is, from the inclination of the object to be measured and the preset scanning speed, Z
Determine the optimum control condition for the axis, and use the optimum control condition for Z
The height of the shaft is controlled to be constant. The tilted state of the object to be measured can be represented by, for example, a control parameter. By obtaining the optimum condition of this control parameter, the acceleration or velocity in the axial direction of the Z axis is controlled according to the tilted state of the object to be measured, and Z Keep the shaft height constant. Therefore, the Z-axis control system is stable, and control delay, vibration, oscillation, etc. do not occur. Therefore, the Z axis can be made to accurately follow the surface state of the object to be measured, and the output of the displacement sensor can be kept constant. The three-dimensional shape of the measured object can be calculated by obtaining the Z coordinate when the height of the Z axis is controlled to be constant and the X and Y coordinates of the measurement point.

[0011]

1 is a schematic diagram of a three-dimensional shape measuring apparatus used in the measuring method of the present invention. In this embodiment, the X-axis rail 1
The triaxial moving mechanism 10 is configured by providing the Z-axis 3 movable in the Y-direction and the Z-direction on the gate-shaped moving body 2 that moves in the X-direction along the Z-axis, and at the lower end of the Z-axis 3. The two non-contact type displacement sensors 4 and 5 for measuring the distance in the Z direction to the object to be measured 20 are mounted close to each other. The triaxial movement mechanism 10 is composed of X, Y, and Z axis movement mechanisms that are configured by conventional means. The DUT 20 is placed on a surface plate (not shown) installed between the two X-axis rails 1. This surface plate constitutes an XY plane for scanning the non-contact type displacement sensors 4 and 5.

In this embodiment, the maximum movement amount of the triaxial moving mechanism 10 is 10,000 mm in the X direction, 4,000 mm in the Y direction, and in the Z direction.
2,000 mm, maximum movement speed of each axis is 500 mm / sec,
The positioning accuracy is 0.1mm.

There are several types of non-contact displacement sensors, such as a helium / neon gas laser and a CCD.
The one using an element, the one using a semiconductor laser and a CCD element, or the one using an ultrasonic wave is typical.

FIG. 2 is a block diagram showing the configuration of a measuring system using the above measuring apparatus. Z-axis movement mechanism 1 including Z-axis 3 equipped with the two non-contact displacement sensors 4 and 5
2 further includes the displacement sensors 4 and 5 together with the Z axis 3 in the X-
It is mounted on an X, Y scanning moving mechanism 11 which is an X, Y axis moving mechanism that moves continuously in the Y plane. The outputs of the displacement sensors 4 and 5 are amplified by the amplifiers 13 and 14, respectively, and the outputs of the amplifiers 13 and 14 are the interface 15
Is taken into the data processing device 16 through. The data processing device 16 is a positioning device 1 for an X, Y, Z axis moving mechanism.
7, which controls the operation of the three-axis moving mechanism 10, and has an inclination calculation unit, a comparison calculation unit, a control condition determination unit, a speed control unit, and a three-dimensional shape calculation unit for the object to be measured 20, which are not shown. It has a function as a CPU. A position detector (not shown) such as an encoder is provided in the moving mechanism of each axis, and the positioning device 17 positions each axis by feeding back the outputs of these position detectors. In addition, the data processing device 16
As will be described later, the control conditions of the three-axis moving mechanism 10,
In particular, a storage device 18 for storing the relationship between the scanning speed of the Z axis, the control parameter and the acceleration or the moving speed, and the output of the displacement sensors 4 and 5 and the position information of the X and Y scanning moving mechanism 11 is connected. Has been done.

The data processing device 16 performs the following processing. First, FIG. 3 shows a method of obtaining the inclination of the DUT 20 from the outputs of the two displacement sensors 4 and 5. The distance between the two displacement sensors 4 and 5 is ΔL, and the sensor A
(4) The distance between the sensor B (5) and the object to be measured 20 is Z1 and Z2, respectively. At this time, the height difference H of the object to be measured 20 is H = Z1 −Z2 (1) Further, the inclination angle θ of the object to be measured 20 with respect to the absolute plane (surface plate surface) 30 is θ = tan ⁻¹ {(Z1 − Z2) / ΔL} (2) That is, from the equations (1) and (2), the size and direction of the inclination of the DUT 20 at the measurement point can be known.

Further, if the scanning speed of the Z-axis 3 in the XY plane is V, C1 = V / H (θ ≠ 0) (3) C2 = V / θ (θ ≠ 0) (4) The given parameters C1 and C2 can be defined as parameters indicating the degree of inclination of the object to be measured with respect to the scanning speed V.

In the data processor 16, the above (1)
The equation (4) is calculated from the equation, and the positioning control device 17 controls the height of the Z-axis 3 from the measured object 20 to be constant for each measurement point. FIG. 4 shows an algorithm for controlling the height of the Z-axis 3 to be constant by the above-mentioned parameter C1 or C2. The outputs of the two displacement sensors 4 and 5 are constantly referred to and the Z-axis 3 is controlled under optimum control conditions. It is decided to control the height of the constant. First, in step S1, when one displacement sensor, for example, the sensor A, coincides with one preset measurement point, the outputs of the sensors A and B are fetched. The X- and Y-coordinates of the measurement points are set in advance at constant pitches, and are set as grid points, for example. Next, the inclination calculation unit of the data processing device 16 causes the above equation (1) to
From the equation (2), the inclination of the DUT 20 at that time is calculated (step S2). Further, the comparison calculation unit calculates the parameters C1 and C2 from the above formulas (3) and (4), and the scanning speed V and the object to be measured 20 are calculated with the calculated values.
The degrees of inclination of the two are compared (step S3). Then, the control condition determining unit determines the optimum condition of the control parameter C1 or C2 of the Z axis 3 (step S4), and the control unit determines the control parameter C1 or C2 of the determined optimum condition for the positioning control device of the Z axis 3. Then, the height of the Z-axis 3 is controlled (step S5). As a result, the Z-axis 3 follows the surface condition of the object to be measured 20 and is always held at a constant height. The Z coordinate which is the output of the sensor A at this time and the X and Y coordinates of each measurement point are synchronously stored in the storage device 18, and these X, Y and Z coordinates are later taken out to obtain the data processing device. The three-dimensional shape of the DUT 20 is calculated by 16 three-dimensional shape calculation units or a separately provided calculation device (not shown).

A method of determining the optimum condition of the control parameter C1 or C2 is, for example, as follows. FIG. 5 shows an example of how to give control parameters for optimizing the control conditions. As shown in (a) and (b) of FIG.
Assuming the axial acceleration αz and the moving speed Vz of the Z-axis 3 as a function of C1 or C2, αz = F1 (C1) or αz = F2 (C2) (5) Vz = G1 (C1) or Vz = G2 (C2) (6) According to the equations (5) and (6), for example, when the control parameter C1 or C2 is large, the acceleration αz or moving speed Vz of the Z-axis 3 is decreased, and conversely, when C1 or C2 is small, αz and Vz are increased. Then, the moving speed of the Z-axis 3 is controlled according to the degree of inclination of the DUT 20. Therefore, the outputs of the sensors A and B can be kept constant, and the control system can be stabilized without causing control delay of the Z-axis 3, vibration of the control system, oscillation, and the like. Therefore, the three-dimensional shape of the DUT 20 can be measured at high speed and with high accuracy.

In the above embodiment, the case where the number of non-contact type displacement sensors is two has been described, but the number of non-contact type displacement sensors may be three or more.
In this case, it is convenient to dispose the displacement sensor at the apex of a triangle rather than to arrange it in a straight line because scanning can be performed in a plane.

[0020]

As described above, according to the present invention, it is possible to detect the magnitude and direction of the inclination of the object to be measured from the outputs of at least two non-contact type displacement sensors, and it is possible to detect the inclination and the degree of inclination. The height of the Z-axis is controlled to be constant, so that the Z-axis can be controlled optimally according to the shape of the object to be measured at any scanning speed, and the output of the displacement sensor can be kept constant. You can Moreover, at any scanning speed from low speed to high speed, the control system is stable without causing Z-axis control delay, control system vibration, oscillation, etc., so that the object to be measured can be measured at high speed and with high accuracy. It is possible to measure a three-dimensional shape.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a three-dimensional shape measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the entire measuring system of the present invention.

FIG. 3 is an explanatory diagram showing a method for obtaining the inclination of the object to be measured from the outputs of two displacement sensors in the present invention.

FIG. 4 is a flowchart showing an algorithm of Z-axis control in the present invention.

FIG. 5 is a graph showing a relationship between a control parameter and Z-axis acceleration or moving speed in the present invention.

[Explanation of symbols]

 1 X-axis rail 2 Moving body 3 Z-axis 4,5 Displacement sensor 10 3-axis moving mechanism 11 X, Y scanning moving mechanism 12 Z-axis moving mechanism 13, 14 Amplifier 15 Interface 16 Data processing device 17 Positioning control device 18 Storage device 20 DUT

Claims (2)

[Claims] 1. At least two non-contact type displacement sensors attached to the Z-axis of a three-axis moving mechanism are continuously scanned in an XY plane while one at a preset measurement point. Each time the displacement sensors match each other, the step of measuring the distance in the Z direction to the object to be measured by the displacement sensor, and the step of obtaining the inclination of the object to be measured from the two distances in the Z direction measured in the step. A step of determining an optimum control condition of the Z axis from a preset scanning speed and an inclination of the object to be measured obtained in the step, and the Z axis from the object to be measured according to the optimum control condition determined in the step. Of the object to be measured is calculated from the Z coordinate and the X and Y coordinates of the measurement point when the height of the Z axis is controlled to be constant in the step. And the process Three-dimensional shape measuring method consists of. 2. A non-contact type displacement sensor, which is attached to the Z-axis of a three-axis moving mechanism and measures a Z-direction distance to an object to be measured, and a positioning control device for the three-axis moving mechanism. An inclination calculating means for obtaining the inclination of the object to be measured from the output of the displacement sensor, a control condition determining means for determining the optimum control condition of the Z axis from the obtained inclination of the object to be measured and a preset scanning speed, A data processing device having a control means for controlling the Z-axis so that the height from the object to be measured becomes constant under the determined optimum control condition, the displacement sensor when the Z-axis height is controlled to be constant, and A storage device for storing the X, Y, Z coordinates of the positioning control device, and a three-dimensional shape measuring device.