JPH08210803A - Straightness measuring instrument - Google Patents

Abstract

PURPOSE: To provide a straightness measuring instrument for easily and inexpensively improving measurement accuracy by compensating a measurement error. CONSTITUTION: While a movable body 5 as well as a displacement sensor 6 are moved by operating a traveling device, the traveling distance is detected by a distance detection part 20 to obtain a variable (x), an approximate expression is subjected to operation by an operation control part 15 with the variable (x) as a base to obtain a measurement error value (z), and a measurement error value (z) is subtracted from an actual measured value (y) by the displacement sensor 6 to obtain a compensated measured value S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a straightness measuring device applied to the measurement of the surface straightness and waviness of a polishing plate made of, for example, a silicon wafer or liquid crystal glass.

[0002]

2. Description of the Related Art Conventionally, the following constitution has been provided as a straightness measuring device of this type. That is, by providing a movable body that moves in contact with a ceramic guide, attach a displacement sensor that measures the distance to the surface to be measured to the movable body, and move the displacement sensor on the surface to be measured. A structure for measuring the straightness of the surface to be measured and a structure using an air slide as a guide are provided.

Of these, the latter straightness measuring device having a structure using an air slide as a guide is commercially available with high accuracy, but on the other hand, it requires an air source, is expensive, and is heavy (measurement length is long). Since there are many disadvantages such as about 50 kg per 1 m), the straightness measuring device with a displacement sensor attached to the former movable body is often used.

[0004]

In the former straightness measuring device described above, the measurement accuracy is determined by the accuracy of the guide and the supporting position. At that time, the measurement accuracy of straightness (measurement error).
If the length of the guide is 1 m or less, 5 μm or more,
It will be about 10 to 20 μm. This is mainly due to the deflection and waviness of the guide, resulting in inaccurate measurements.

It is an object of the present invention to provide a straightness measuring device capable of correcting such a measurement error and improving the measurement accuracy easily and inexpensively.

[0006]

In order to achieve the above object, a straightness measuring device of the first aspect of the present invention moves with a guide member placed on a surface to be measured and guided by the guide member. A straightness measuring device having a movable body which is movable by a device and a displacement sensor which is provided on the movable body and measures a displacement of a surface to be measured. An arithmetic control unit that is approximated by a mathematical expression that uses the moving distance as a variable and that inputs the approximate expression, and a distance detecting unit that detects the moving distance of the movable body are provided, and the arithmetic control unit detects by the distance detecting unit. An approximate expression is calculated from the calculated moving distance to obtain a measurement error value, and the actual measurement value of the displacement sensor is corrected by the measurement error value to obtain the measurement value.

The straightness measuring device according to the second aspect of the present invention comprises a guide member placed on the surface to be measured, a movable member guided by the guide member and movable by a moving device. A straightness measuring device provided with a movable body and a displacement sensor for measuring the displacement of a surface to be measured, wherein a measurement error value of the straightness measuring device is obtained by previously measuring a reference gauge and input, An arithmetic control unit is provided for correcting the actual measurement value of the displacement sensor by the measurement error value to obtain the measurement value.

The straightness measuring device according to the third aspect of the present invention comprises a guide member placed on the surface to be measured, and a movable body which is guided by the guide member and is movable by a moving device. A straightness measuring device having a first displacement sensor provided on a movable body for measuring the displacement of a surface to be measured, wherein the straightness measuring device comprises a master gauge along a guide member,
A second displacement sensor provided on the movable body for measuring the displacement amount with respect to the master gauge, and a calculation for obtaining a measurement value by correcting the actual measurement value of the first displacement sensor using the displacement amount detected by the second displacement sensor as a measurement error value. A control unit is provided.

[0009]

According to the configuration of the first aspect of the invention described above, while the displacement sensor is moved together with the movable body by the operation of the moving device, the distance detected by the distance detection unit is used to obtain a variable, and calculation is performed based on this variable. The control unit can calculate the measurement error value by calculating an approximate expression, and subtract the measurement error value from the actual measurement value of the displacement sensor to obtain the corrected measurement value.

According to the structure of the second aspect of the present invention, while the displacement sensor is moved together with the movable body by the operation of the moving device in the state where the center line of the displacement output value of the reference gauge is set as the measurement error value, the displacement sensor is used. By subtracting the measurement error value from the actual measurement value, the corrected measurement value can be obtained.

According to the structure of the third aspect of the present invention, the displacement of the surface to be measured is measured by the first displacement sensor by moving the first displacement sensor and the second displacement sensor together with the movable body by the operation of the moving device. At the same time as obtaining the actual measurement value, the displacement amount with respect to the master gauge is measured by the second displacement sensor to obtain the measurement error value. Then, the calculation control unit calculates the actual measurement value and the measurement error value to obtain the actual measurement value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
It will be described based on. 1 and 2, reference numeral 1 denotes a straightness measuring device according to the present invention, which has a rail-shaped guide member 2 made of, for example, ceramics. The mounting legs 3 and 4 mounted on the surface 26 are attached. A movable body (sensor carriage) 5 is provided which is guided by the guide member 2 and is movable in the horizontal direction. The movable body 5 has a surface to be measured.
A displacement sensor 6 for measuring the displacement of 26 is attached.

A linear guide system (LM) is used as a slide mechanism for the movable body 5 with respect to the guide member 2. As the displacement sensor 6, a contact type displacement sensor 6 of a linear encoder type is used.
For example, a non-contact type displacement sensor such as an eddy current type, an optical type, or an air sensor may be used.

A moving device 10 for moving the movable body 5 is provided between the two mounting legs 3 and 4 and the guide member 2. The moving device 10 includes a drive pulley 11 provided on one end of the guide member 2 outside one of the mounting legs 3 and a driven pulley 12 provided on the other mounting leg 4. And a cord body (for example, a wire or the like) 13 having both ends thereof connected to the movable body 5 while being wound around these pulleys 11 and 12, and one end portion of the guide member 2. It is composed of a motor 14 and the like which is attached to rotate the drive pulley 11. Therefore, by rotating the motor 14, the displacement sensor 6 attached to the movable body 5 can be moved in the horizontal direction along the guide member 2.

An arithmetic control unit (microcomputer, etc.) 15 which is obtained by approximating the measurement error of the straightness measuring device 1 in advance by a mathematical expression in which the moving distance of the movable body 5 is a variable x, and inputting the approximate expression. A moving distance of the movable body 5, that is, a distance detecting unit 20 for detecting the variable x is provided. The approximate expression differs depending on the measuring device, but in this case, it is set to the following expression 1.

[0016]

[Equation 1]

The arithmetic control unit 15 calculates the approximate number 1 by the moving distance detected by the distance detecting unit 20, that is, the variable x to obtain the measurement error value z, and the first arithmetic unit 16. A second calculation unit 17 for obtaining the measured value S by correcting the measured value y of the displacement sensor 6 with the measured error value z from 16.
Also, it has a storage unit 18 for inputting the measured value S and a variable x which is the moving distance of the movable body 5. The distance detecting section 20 is composed of, for example, an encoder 21 that takes out the rotation speed of the motor 14 as a pulse, and a moving distance detector 22 that changes the detection pulse of the encoder 21 into a variable x and outputs it.

In the following, in the above-mentioned first embodiment,
The measurement work of straightness and waviness on the surface 26 to be measured will be described assuming that the measurement length is 1450 mm. First, when the master prototype was measured by the straightness measuring device 1, a straight shape as shown in FIG. 3 was obtained. The straightness of this master prototype is 1
Although it is μm, if the straightness is further deteriorated, it can be regarded as a measurement error. Further, since the output value of the displacement sensor 6 varies, the straightness will be considered by its center line. Then, the straightness in FIG. 3 is 19.1 μm, which is almost a measurement error. This measurement error is due to the accuracy of the guide member 2 and the supporting method (supporting position) via the legs 3 and 4.

Therefore, this measurement error is approximated by the above-mentioned equation 1 as shown in FIG. Then, the master prototype is measured as a measurement value S obtained by subtracting the measurement error value (approximate value of error) z from the actual measurement value y by the displacement sensor 6, and as a result, the straightness (measurement accuracy) is as shown in FIG. It was improved to 6.9 μm. The measurement accuracy improves as the number 1 approaches the measurement error in FIG.

Therefore, while the displacement sensor 6 is moved together with the movable body 5 by the operation of the moving device 10, the moving distance is detected by the distance detecting unit 20 to obtain the variable x, and the first computing unit is based on this variable x. In 16, the equation 1 is calculated to obtain the measurement error value z, and the measured value y by the displacement sensor 6 is obtained.
Then, by subtracting this measurement error value z, the corrected measurement value S can be obtained.

6 to 8 show a second embodiment of the present invention. That is, the arithmetic control unit 30 obtains and inputs the measurement error value z of the straightness measuring device 1 by measuring a reference gauge (such as a stone surface plate) in advance, and inputs the measurement error value setting unit 31.
The calculation unit 32 for correcting the actual measurement value y of the displacement sensor 6 to obtain the measurement value S by the measurement error value z from the measurement error value setting unit 31, and the measurement value S and the distance detection unit 20. The storage unit 33 into which the measured moving distance value L of the movable body 5 is input.
And so on.

That is, in the second embodiment, the center line (FIG. 7) of the displacement output value of the master prototype is used as the measurement error. Then, the master prototype was measured as a measurement value S obtained by subtracting the measurement error value (approximate value of error) z from the actual measurement value y of the displacement sensor 6, and the straightness was 1.
It was improved to 7 μm.

Therefore, while the displacement sensor 6 is moved together with the movable body 5 by the operation of the moving device 10, the moving distance is detected by the distance detecting section 20 to obtain the moving distance value L, and at the same time, the displacement sensor 6 is actually measured. The corrected measurement value S can be obtained by subtracting the measurement error value z from the value y.

9 and 10 show a third embodiment of the present invention. That is, the guide member 2 is provided between the mounting legs 3 and 4.
A master gauge 40 is arranged along (parallel to). The movable body 5 guided by the guide member 2 has a first displacement sensor 41 that measures the displacement of the surface 26 to be measured and a second displacement sensor 42 that measures the amount of displacement with respect to the master gauge 40.
Are provided.

The calculation control unit 45 corrects the measured value y of the first displacement sensor 41 by using the displacement amount detected by the second displacement sensor 42 as a reference, that is, the displacement amount as a measurement error value z, and obtains the measured value S. It has a calculation unit 46 for obtaining it, a storage unit 47 to which the measured value S from this calculation unit 46 and the moving distance value L of the movable body 5 are input.

Next, the work of measuring the straightness and waviness of the surface to be measured 26 in the third embodiment will be described. Here, in the actual measurement value y that is the output of the first displacement sensor 41 that measures the displacement of the measured surface 26 and the measurement error value z that is the output of the second displacement sensor 42 that measures the displacement amount with respect to the master gauge 40, The actual measured value S is

[0027]

## EQU00002 ## Calculated as S = yz.

Therefore, when the moving device 10 is operated, the movable body 5 and the first displacement sensor 41 and the second displacement sensor 41 are moved.
The surface to be measured by the first displacement sensor 41 while moving 42.
The 26 displacements are measured to obtain the measured value y, and at the same time, the displacement amount with respect to the master gauge 40 is measured by the second displacement sensor 42 to obtain the measurement error value z. The actual measurement value S can be obtained by calculating the error value z based on the above-described equation 2. The measured value S is input to the storage unit 47 and stored together with the moving distance value L from the distance detecting unit 20.

[0029]

According to the first aspect of the present invention having the above-described structure, by moving the displacement sensor together with the movable body by the operation of the moving device, it is possible to detect the moving distance by the distance detecting section and obtain a variable. A calculation error value can be obtained by calculating an approximate expression in the calculation control unit based on this variable, and a corrected measurement value can be obtained by subtracting the measurement error value from the actual measurement value by the displacement sensor. Therefore, the straightness of the entire surface to be measured can be measured easily, inexpensively and accurately.

Further, according to the second aspect of the present invention having the above-mentioned structure, while the displacement sensor is moved together with the movable body by the operation of the moving device in a state where the center line of the displacement output value of the reference gauge is the measurement error value, the displacement sensor is moved. By subtracting the measurement error value from the actual measurement value obtained by, the corrected measurement value can be easily and inexpensively obtained with high accuracy.

Further, according to the third aspect of the present invention having the above structure, the displacement of the surface to be measured is measured by the first displacement sensor by moving the first displacement sensor and the second displacement sensor together with the movable body by the operation of the moving device. It is possible to obtain an actual measurement value and at the same time obtain a measurement error value by measuring the displacement amount with respect to the master gauge by the second displacement sensor, and the arithmetic control unit calculates the actual measurement value and the measurement error value. Thus, the actual measurement value can be easily and inexpensively obtained with high accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic overall configuration of a straightness measuring device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a main configuration of the straightness measuring device.

FIG. 3 is an explanatory diagram showing a result of measuring the master prototype.

FIG. 4 is an explanatory diagram showing an example of approximation of an error by the same mathematical expression.

FIG. 5 is an explanatory diagram showing a result of measuring a master prototype using the same mathematical expression as a correction value.

FIG. 6 is an explanatory diagram showing a main configuration of a straightness measuring device according to a second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing an actual measurement value of the measurement error.

FIG. 8 is an explanatory diagram showing a result of measuring a master prototype with the same measurement values.

FIG. 9 is a perspective view showing a schematic overall configuration of a straightness measuring device according to a third embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a main configuration of the straightness measuring device.

[Explanation of symbols]

 1 Straightness measuring device 2 Guide member 3, 4 Mounting leg 5 Movable body 6 Displacement sensor 10 Moving device 15 Arithmetic control unit 20 Distance detecting unit 26 Measured surface 30 Arithmetic control unit 31 Measurement error value setting unit 40 Master gauge 41 1st displacement sensor 42 2nd displacement sensor 45 Arithmetic control unit x variable (moving distance of movable body) z measurement error value y measured value of displacement sensor S measured value L moving distance value

Claims (3)

[Claims] 1. A guide member placed on a surface to be measured,
A straightness measuring device having a movable body which is guided by the guide member and is movable by a moving device, and a displacement sensor which is provided on the movable body and measures a displacement of a surface to be measured. , The measurement error of this straightness measuring device is approximated in advance by a mathematical expression in which the moving distance of the movable body is a variable,
An arithmetic control unit that inputs the approximate expression and a distance detection unit that detects the moving distance of the movable body are provided, and the arithmetic control unit calculates the approximate expression based on the moving distance detected by the distance detecting unit. A straightness measuring device characterized in that a measurement error value is obtained, and an actual measurement value of a displacement sensor is corrected by the measurement error value to obtain a measurement value. 2. A guide member mounted on the surface to be measured,
A straightness measuring device having a movable body which is guided by the guide member and is movable by a moving device, and a displacement sensor which is provided on the movable body and measures a displacement of a surface to be measured. , The measurement error value of this straightness measuring device,
Input and obtain by measuring the reference gauge in advance,
A straightness measuring device comprising an arithmetic control unit for correcting a measured value of a displacement sensor by the measured error value to obtain a measured value. 3. A guide member mounted on the surface to be measured,
A straightness measuring device having a movable body which is guided by the guide member and is movable by a moving device, and a first displacement sensor which is provided on the movable body and measures a displacement of a surface to be measured. The straightness measuring device includes a master gauge along a guide member, a second displacement sensor provided on the movable body for measuring a displacement amount with respect to the master gauge, and a displacement detected by the second displacement sensor. A straightness measuring device comprising an arithmetic control unit for correcting a measured value of the first displacement sensor to obtain a measured value by using a quantity as a measurement error value.