JPH04313714A - Inclination correcting device for sample table - Google Patents

Abstract

PURPOSE:To exactly set the inclination of a sample table against an optical system with simple constitution, in the inclination correcting device for the sample table used for a measuring instrument provided with a confocal optical system such as a laser microscope. CONSTITUTION:The relation of a working distance and brightness of an image is stored in an image memory 5 in advance. Based on the position of a sample point in the surface image of an obtained sample 3 and brightness information, the inclination of the present sample table 9 is calculated, and the inclination of the sample table 9 is controlled by a table driving device 8. In such a manner, the inclination of the sample table can be corrected exactly with the simple constitution which does not use an external sensor.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for correcting the inclination of a sample table, and relates to an apparatus used, for example, in an apparatus for measuring minute patterns or surface profile profiles.

0002

BACKGROUND OF THE INVENTION In a measuring device such as a laser microscope, which consists of a confocal optical system and a sample table that can tilt its optical axis, in order to accurately set the sample tilt angle, it is necessary to Conventionally, external optical or electrostatic sensors were required.

On the other hand, as a technique for correcting the inclination of the sample table using information from the microscope image itself,
There was one disclosed in Japanese Unexamined Patent Publication No. 61-223551. FIG. 4 is a block diagram showing the configuration of an ultrasonic microscope. In the figure, 3 is a sample, 21 is a sonic lens, and 2
2 is a receiver for a high frequency signal obtained by converting an ultrasonic wave, 23 is a sample tilt controller, 23a and 23b are an image memory and an arithmetic processing unit that constitute the sample tilt controller 23, and 24 is a receiver for moving the sample table 25 in the X and Y directions. The sample table drive units 26a and 26b for scanning the sample 3 are piezoelectric elements for tilting the sample 3.

Next, the operation will be explained. sonic lens 2
A video signal obtained from the receiver 22 from the receiver 22 is taken into the image memory 23a. The amount of change in the video signal increases or decreases depending on the degree of inclination of the sample 3, and the calculation processing unit 23b calculates the amount of change in the video signal and the maximum brightness point at a reference position in the two-dimensional scanning direction of the sample 3, that is, in the X or Y direction. Let's do it. Based on this calculation result, the piezoelectric elements 26a and 26b are operated so that the inclination of the sample 3 is minimized.

[0005]

[Problems to be Solved by the Invention] Conventional sample table tilt correction devices are constructed as described above, and those that use an external sensor use the output value from the sensor to calculate the actual tilt of the sample table. There was a problem in that the device configuration had to be calibrated to match the corners, making the device configuration complicated. Furthermore, the method disclosed in Japanese Patent Application Laid-Open No. 61-223551 does not require an external sensor, but requires moving the sample table 25 to obtain an image, which slows down the process.
Further, there was a problem in that although the inclination of the sample 3 could be made small, it was not possible to set it to an arbitrary inclination angle.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a sample table tilt correction device that can correct the sample table tilt with a simple configuration. It is said that

[0007]

[Means for Solving the Problems] A sample table tilt correction device according to the present invention includes a confocal optical system for observing a sample on a sample table, and a storage means for storing the relationship between work distance and image brightness. , a calculation means for calculating the inclination angle of the sample table based on the position and brightness information of the sample point in the surface image of the sample, and a sample table driving means for controlling the inclination of the sample table, and the obtained surface image of the sample is provided. The present invention is characterized in that the present tilt angle of the sample table is calculated based on the position and brightness information of the sample point, and the tilt is controlled.

[0008]

[Operation] In the sample table inclination correction device according to the present invention, there is a close relationship between the work distance and the image brightness, and based on the position and brightness information of the sample point, the inclination angle of the sample table can be determined. can be calculated accurately.

[0009]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a measuring device using a sample table tilt correction device according to an embodiment of the present invention. In the figure, 1 is a laser microscope equipped with a confocal optical system, 2 is a finely focused laser beam that scans over the sample and obtains a sample image using reflected light, 3 is a sample, and 4 is a laser beam obtained from laser microscope 1. 5 is an image memory; 6 is an arithmetic processing unit that calculates the inclination of the sample; 7 is a table controller that controls the sample table 9; Reference numeral 8 denotes a table driving device for driving the sample table 9.

FIG. 2 is a graph showing the relationship between the work distance d and the image brightness f(d) at that time, and if the material of the sample 3 is the same, the relationship will be constant. df is the focus position. This relationship is stored in advance in the arithmetic processing unit 6 for each material. When observing the sample 3 while tilting it, the following procedure is used. First, an area on the sample 3 whose surface shape is within the depth of focus of the optical system is positioned in the field of view of the laser microscope 1. Therefore, the video signal is taken into the image memory 5 via the A/D converter 4. FIG. 3 shows the captured input image 10, in which the arithmetic processing unit 6 has 11, 12, 1
Sample point 1, sample point 2, and sample point 3 of 3 are extracted. The reason why three points are extracted is that, as shown in FIG. 2, the brightness of the image does not change monotonically with respect to the work distance d, but has an extreme value. The brightness of the three points f(d1), f(
d2), f(d3) and distances L1 and L2, two points that do not include the focal position df are selected. For example, if the two points are sample point 1 and sample point 2, then the current slope θ of the sample can be found from the following formula.

[0011]

[Math 1]

When the desired inclination angle and the current sample inclination θ are transferred to the table controller 7, the table controller 7 instructs the table driving device 8 to correct the sample table 9 to an appropriate angle. L1 and L2 need to be sufficiently large within the input image 10 to improve the correction accuracy. In this way, the relationship between work distance and image brightness is stored in advance, and the current tilt angle of the sample table is calculated based on the position and brightness information of the sample point in the obtained sample surface image. Since feedback is applied, it is possible to correct the inclination of the sample table with a simple configuration without using an external sensor, and it is possible to obtain a device for correcting the inclination of the sample table at a low cost. . Furthermore, in order to increase reliability, the value of each sample point may be determined not only from one point but also from the average of nearby points.

Example 2. In Example 1 above, the relationship between the work distance d and the image brightness f(d) at that time is stored for each material, but it may also be multiplied by a coefficient based on the reflectance of the material. .

Example 3. In the first embodiment described above, an area on the sample 3 to be observed whose surface shape is within the depth of focus of the optical system is selected. good.

Example 4. In the first embodiment described above, three sample points are extracted, and two points that do not include the focus position df are selected between them. Alternatively, only one sample point 2 may be extracted to determine the slope.

[0016]

As described above, according to the present invention, there is provided a confocal optical system for observing a sample on a sample table, a storage means for storing the relationship between work distance and image brightness, and a sample surface image of the sample. Equipped with a calculation means for calculating the tilt angle of the sample table based on the position and brightness information of the point, and a sample table driving means for controlling the tilt of the sample table, the position and brightness of the sample point in the obtained surface image of the sample is provided. Since the current tilt angle of the sample table is calculated based on the tilt information and the tilt is controlled, the sample table tilt can be corrected with a simple configuration without using an external sensor. This has the effect of providing a bull tilt correction device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a tilt correction device for a sample table according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between work distance and image brightness according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a captured input image according to an embodiment of the present invention.

FIG. 4 is a block diagram showing the configuration of a conventional sample table tilt correction device.

[Explanation of symbols]

1 Laser microscope 2 Laser beam 3 Sample 4 A/D converter 5 Image memory 6 Arithmetic processing unit 7 Table controller 8 Table drive device 9 Sample table 10 Input image 11 Sample point 1 12 Sample point 2 13 Sample point 3

Claims (1)

[Claims] Claims: 1. A confocal optical system for observing a sample on a sample table, a storage means for storing the relationship between the work distance and image brightness, and a storage means for storing the relationship between the work distance and image brightness, based on the position and brightness information of the sample point on the surface image of the sample. It is equipped with a calculation means for calculating the inclination angle of the sample table, and a sample table driving means for controlling the inclination of the sample table. A tilt correction device for a sample table, characterized in that the tilt angle of the sample table is calculated and the tilt is controlled.