JPH0293309A - Thickness measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a thickness measuring apparatus which can highly accurately measure the distribution of thickness of a test specimen by preliminarily correcting a linearity error with the use of a correcting tool having the same reflection characteristic as said test specimen and having steps each at a predetermined height. CONSTITUTION:A correcting tool 24 is placed on a reference surface 22, and a pulse motor 19 is driven to move a distance sensor 18 to a point A, i.e., where the measuring position i=0. The distance from the original to the correcting tool 24 is input to a controlling computer 20 as an analog amount, and an original error DELTAy is obtained by an original error calculating unit 14. Then, the distance sensor 18 is moved to a point B, when an inclination error alpha1 is obtained by an inclination error calculating unit 15. Next, the sensor is moved to a position C to obtain a linearity error factor beta. After the correcting tool 24 is removed, test specimen is placed on the reference surface 22, and the distance sensor 18 is sequentially moved to the measuring position where i=0-n. By correcting the actually-measured value at respective measuring positions with the errors DELTAy, alpha1 and beta, the thickness of the test specimen can be measured with high accuracy.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to a distance 11t-
The present invention relates to a thickness measuring device that uses a sensor to measure the thickness distribution of an object with high precision.

(Prior art) Generally, in order to measure the thickness of an object, a light beam such as a semiconductor laser is irradiated onto the object based on the principle of triangulation.
A method is adopted that uses a distance sensor consisting of a photoelectric displacement meter that measures the distance to the object by receiving the reflected light with an optical position detection element.

When measuring the thickness distribution of an object to be measured using such a distance sensor υ, place the object to be measured on the measurement reference plane, move the distance sensor parallel to the measurement reference plane,
The thickness distribution is measured by measuring the distance from the origin of the distance sensor to the surface of the object to be measured for each moving position, and subtracting this from the origin distance between the origin of the distance sensor and the measurement reference plane. I have to.

FIG. 6 shows a conventional example of such a thickness measuring device. In the figure, 10 is a control computer, 11 to 13 are software blocks for the calculation 1110, 11 is an analog input thickness conversion section, 12 is a motor position control section, 1
3 is a thickness measuring section. Further, 18 is a distance sensor as a distance measuring means, 19 is a pulse motor for moving the position of the distance sensor 19, 21 is a ball screw portion for moving the distance sensor 19, and 2
Reference numeral 2 denotes a reference plane during measurement, which is made of a material such as white ceramic, and is located at the origin distance position of the distance sensor 18.

23 indicates the object to be measured, point A and point B are the measurement start position and measurement end position, respectively, and the sentence is the measurement width range, and the measurement object 23 consists of a unit width obtained by dividing this measurement width range intersection into n. The thickness is measured at each measuring portion fli -0 to fli-n.

L+ 12 indicates the movement axis of the distance sensor 18 and the horizontal axis of the reference plane 22 corresponding to the movement axis.

When measuring the thickness distribution of the object to be measured 23, first, the origin distance of the distance sensor 18 with respect to the reference plane 22 at points A and B and the parallelism are adjusted so that the moving axis L1 and the horizontal axis L2 are parallel to each other. After the adjustments are made, measurements begin. In the control computer 10, the rotation of the pulse motor 19 is controlled by the motor position control unit 12 in units of measurement positions i=Q to n, and the distance from the distance sensor 18 to the surface of the object to be measured 23 is input in analog form. The analog input thickness conversion section 11 converts it into thickness, and the thickness measurement section 13 converts it into thickness! fi=o
A thickness of ~n is measured.

(Problem to be Solved by the Invention) In a thickness measuring device in which a distance sensor is moved parallel to a reference plane, A It is necessary to make fine mechanical adjustments at two positions, point and B, but it is difficult to obtain highly accurate measurement results with only mechanical adjustment.In addition, with photoelectric distance sensors, If the material of the reference surface and the material to be measured are different, the difference in reflection characteristics will cause a linearity error that depends on the height of the object surface, that is, the measurement thickness, as will be explained later using FIG.
This affects measurement accuracy.

The compound error caused by the mechanical fine adjustment and linearity error cannot be ignored, especially when measuring a thin and wide object.

The present invention has been made based on the above circumstances, and an object of the present invention is to provide a thickness measuring device that can perform highly accurate thickness measurement by correcting complex errors caused by mechanical adjustment and linearity errors.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention moves an optical distance measuring means for optically measuring a distance in parallel to a reference plane, and A correction jig for measuring the thickness distribution of an object to be measured above, the correction jig having steps having the same reflection characteristics as the object to be measured and each step having a predetermined height. error calculating means for calculating in advance a linearity error caused by a mechanical error between the optical distance measuring means and the reference surface and a reflection characteristic of the object to be measured using the method; The gist of the present invention is to include a correction processing means for correcting each error obtained by the error correction means to the actual measured value.

(Function) In the above configuration, the linearity error caused by the mechanical error between the optical distance measuring means and the reference surface and the reflection characteristics of the object to be measured is determined in advance, and the actual measured value of the thickness distribution of the object to be measured is calculated in advance. Each of the above-mentioned errors is corrected to obtain a highly accurate thickness measurement.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

In FIG. 1, the same or equivalent components as those in FIG. 6 are designated by the same reference numerals, and redundant explanation will be omitted.

First, the configuration of the thickness measuring device will be explained. In this embodiment, - the control calculator 20 includes an error calculation section as an error calculation means consisting of an origin error calculation section 14, an inclination error calculation section 15, and a linearity error calculation section 16; 30, and a thickness measurement correction value calculation unit 1 as a correction processing means for correcting the actual measurement value based on each error determined in advance by the error calculation unit 30.
7 is provided.

24 is a correction jig which has the same reflection characteristics as the object to be measured and has two heights V+ within the measurement range of the distance sensor 18.
It has a step consisting of q'i'2, and its length has a size and shape j that is longer than the measurement width range.

Then, the error calculation unit 30 uses the correction jig 24 to calculate mechanical errors between the distance sensor 18 and the reference plane 22, such as origin errors and tilt errors, and linearity errors caused by reflection characteristics of the object to be measured. Each error can be determined in advance.

Point A, point B, and point 0 indicate respective measurement positions with respect to the correction jig 24 when determining the origin error, inclination error, and linearity error.

Next, using the correction jig 24, the origin error Δy1 inclination error α
, the linearity error rate β and the principle of determining the correction value $1 based on these errors will be explained using FIG.

Now, the measured values of the thickness and height of the correction jig 24 at the points A, B and 0 are respectively DA and DBlCC.
shall be.

First, FIG. 2(A) shows the origin error Δy of the distance sensor 18.
This shows the case where you want to find . The origin error Δy is the same error at any position on the correction jig 24, and the measured value D at point A
A and the height yl of the first stage of the correction jig 24 are used to find the following equation.

Δy=D^-y1...(1)
24a indicates the virtual position of the correction jig 24 at this time.

FIG. 2(B) shows the case where the slope error α1 is determined. The slope error α1 is a constant value on both sides between points A and B [)A
, [) By dividing the difference between B by n and multiplying by the value of each measurement position i, a value corresponding to each measurement position i as shown in the following equation can be obtained.

α+ = (DB - DA) ・i/n -
(2) 24b indicates the virtual position of the correction jig 24 at this time.

FIG. 2(C) shows the case where the linearity error rate β is determined.

The linearity error β is, as shown by the characteristic line in Figure 3,
Although the reflection characteristics differ depending on the material, different values will be shown, but it can be considered that it shows approximately linearity over the measurement thickness range. Therefore, the following two equations can be obtained by using the height yl of the first stage and its measured value DB and the height yl of the second stage and its measured value OA in the correction jig 24, and further by a linear proportional error. .

DB=β・yl...(3)
DC=β・(Vl+”)/2)...
・(4>Here, if we subtract equation (3) from equation (4) above, we get
The following equation is obtained and the proportional error, that is, the linearity error rate β is determined.

β= (Da-DB)/V2...(
5) 24G indicates the virtual position of the correction jig 24 at this time. In the above equation (5), the origin error Δy mentioned above is irrelevant, and the slope error α1 can also be ignored if the measurement value between points B and C is sufficiently short in the measurement width range.

In this way, the origin error Δy, the inclination error αI, and the linearity error rate β are obtained in advance, and the
By subtracting the origin error Δy and the slope error α1 from the actual measured value D1 and dividing the value by the linearity error rate β, a correction value S as shown in the following equation is obtained.

S+ = (actual measurement value - (origin error + tilt error)) / linearity error rate = (D + - (Δy + αl)) / β ... (6) In the above formula (6), (Δy + α1) is measured. 3 in advance as a table at position i! If you choose (), the above correction value S
1 becomes even easier.

Next, a method for measuring the thickness distribution of an object to be measured based on the above-mentioned principle will be described.

First, the correction jig 24 is placed on the reference plane 22. Then, in the control computer 20, the motor position control unit 12 drives the pulse motor 19, moves the distance sensor 18 to point A, that is, the measurement position i-〇, and calculates the distance from the origin to the correction jig 24 as an analog quantity. input. After this analog input value is converted into a thickness measurement value DA by the analog horn thickness conversion section 11, the origin error calculation section 14 calculates the equation (1) above to obtain the origin error Δy.

Next, the motor position i, IJ 111 unit 12 moves the distance sensor 18 to point B, that is, the measurement position i=n, and the inclination error calculation unit 15 calculates the measured value DB and the measurement W1DA obtained earlier at point A. Calculate the equation (2) by a to obtain the slope error α1.

Next, the distance sensor 18 is moved to the second stage position C point of the correction jig 24, and the linearity error rate is calculated by calculating the equation (5) from the measured value DC and the measured value DB previously obtained at point B. Find β.

Through the above processing, the origin error Δy, the tilt error α1, and the linearity error rate β are obtained in advance.

Next, after removing the correction jig 24, the object to be measured is placed on the reference plane 22, and the motor position control unit 12 moves the object to be measured at the measurement position ff1i.
The distance sensor 18 is sequentially moved from =o to n, and the correction value S1 is sequentially determined from the actual measurement 1inD+ of the corresponding measurement position using the above equation (6). This correction value S1 is the final value of the thickness to be determined.

In this way, in this embodiment, each error Δy, α1, and linearity error rate β can be easily determined in advance using the correction jig 24, and the origin between the distance sensor V and the reference plane can be easily determined in advance as in the conventional example. It is possible to realize a thickness measurement position that does not require fine adjustment or separate error correction processing based on the reflection characteristics of the object to be measured.

Further, in the above-described embodiment, the thickness distribution of the object to be measured is measured by moving the distance sensor, but a method may be used in which the distance sensor is fixed and the reference plane is moved.

Next, FIGS. 5 and 6 show examples of application of the present invention. This application example shows a case where thickness distribution is measured in multiple planes.

Note that FIG. 4 corresponds to the right side view of the distance sensor and other parts in FIG. 1.

In FIGS. 4 and 5, j indicates the measurement position in the depth direction, which is divided into m. Intersection 1 indicates the moving distance in the depth direction, and θ1 indicates the inclination of the sensor moving axis in the depth direction and the reference plane 22. In this application example, the object to be measured 23a is the correction jig 2.
Measurements were made under the conditions mounted on 4.

When measuring the thickness distribution of the object to be measured 23a also in the depth direction, since there is an inclination error in the depth direction, for each measurement position j in the depth direction, the origin is determined from the measured values at measurement positions i=Q and n. The method is to calculate the error and slope error and correct the actual measured value. However, when measuring the object to be measured 23a directly mounted on the correction jig 24 in this way, the final correction value is determined by calculating the height of the first stage of the correction jig 24 from the value obtained by the above formula (δ). It is necessary to subtract yl.

[Effects of the Invention] As explained above, according to the present invention, the linearity error caused by the mechanical error between the optical distance measuring means and the reference surface and the reflection characteristics of the object to be measured is calculated by the error calculation means. Since the above-mentioned errors are calculated in advance and then corrected to the actual measured value of the object by the correction processing means, complex errors caused by fine mechanical adjustment and linearity errors between the optical distance measuring means and the reference surface are eliminated. is corrected, making it easy to perform highly accurate thickness measurements.

Therefore, the thickness measuring device according to the present invention is highly effective when measuring the thickness distribution of particularly thin and wide objects such as semi-viscous materials, powders, and plates.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of the thickness measuring device according to the present invention. Figure 1 is a block diagram showing the overall configuration, and Figure 2 shows the principle for determining the origin error, inclination error, and linearity error. Figure 3 is a characteristic diagram showing an example of the linearity characteristic of an object, Figures 4 and 5 are diagrams showing an application example of the above embodiment, and Figure 4 is a configuration diagram of the distance sensor etc. , FIG. 5 is a plan view, and FIG. 6 is a configuration diagram of a conventional thickness measuring device. 14: Origin error calculation section, 15: Incline error calculation section, 16: Linearity error meter section, 17: Thickness measurement correction value meter n section (correction processing means), 18:
Distance sensor (optical distance measuring means), 22: reference plane,
24: Correction jig; 30: Error calculation unit (error calculation means).

Claims (1)

[Scope of Claims] A thickness measuring device that measures the thickness distribution of an object to be measured on the reference surface by moving an optical distance measuring means for optically measuring distance in parallel to a reference surface, comprising: The mechanical error between the optical distance measuring means and the reference surface is corrected by using a correction jig having steps having the same reflection characteristics as the object to be measured and each step having a predetermined height. an error calculation means for calculating in advance a linearity error caused by the reflection characteristics of the object to be measured; and a correction processing means for correcting each error calculated by the error calculation means to the actual measured value of the thickness distribution of the object to be measured. A thickness measuring device characterized by having: