JP4791155B2 - Focusing method, focusing device, and measuring apparatus using the same - Google Patents

Description

  The present invention relates to an image processing apparatus for capturing an enlarged subject image and measuring the size of the subject, and more particularly to autofocus (hereinafter abbreviated as AF) processing.

FIG. 3 is a block diagram showing a schematic configuration of the line width measuring apparatus. The line width measuring device is a device mainly for inspecting the mask pattern width and defects of a semiconductor TFT (Thin Film Transistor) substrate.
As shown in FIG. 3, the line width measuring device mainly includes an XY stage 45, a Z moving mechanism 44, an X moving mechanism 42, a Y moving mechanism 43, a camera 40, a light source 46, a microscope 41, an AF device 52, a PC 50, Consists of monitor 51.
Here, the direction of X movement is the left and right direction on the page, the Y movement direction is the depth direction on the page that intersects the X movement direction at right angles, and the Z movement direction is a plane formed by the X movement and Y movement directions ( It is a direction (vertical direction on the paper surface) perpendicular to the (horizontal direction).

The XY stage 45 is a sample stage on which a mask of a subject (for example, a TFT substrate) is placed, and the horizontal position control is performed by the X moving mechanism 42 and the Y moving mechanism 43. The XY stage 45 performs vertical position control by the Z moving mechanism 44.
The PC 50 uses the application software to control the X driver 47, the Y driver 48, and the Z driver 49, and through the X driver 47, the Y driver 48, and the Z driver 49, the X moving mechanism. 42, the Y moving mechanism 43, and the Z moving mechanism 44 are driven.
The XY stage 45 is installed on a vibration-proof fixed base.

For example, the microscope 41 is a reflective microscope, and the PC 50 controls the light source 46 to irradiate the subject with illumination light.
When the irradiated light is reflected from the subject, the subject image enters the microscope 41 and is enlarged through the microscope 41, and the enlarged subject image enters the photoelectric conversion surface of the camera 40.
The camera 40 captures the incident enlarged subject image, converts it into a video signal, and outputs it to the PC 50.
The PC 50 performs image processing on the input video signal using predetermined application software.

When measuring the line width of a pattern such as a mask formed on a TFT substrate, the flow is as follows.
The mask, which is the subject, is placed on the XY stage 45, and the PC 50 controls the X driver 47, Y driver 48, and Z driver 49 to move to a certain pattern position on the mask.

The depth of focus of the microscope 41 decreases as the magnification increases. For example, in order to measure and inspect with an accuracy of several μm, the microscope 41 is set to a high magnification, so that a focusing (autofocus, hereinafter referred to as AF) process is required.
The AF process moves the XY stage 45 up and down and determines the focus value output from the AF device 52 with the application software of the PC 50, so that the in-focus position (the height of the XY stage 45 in the Z direction) And the vertical movement of the XY stage 45 is stopped at the detected in-focus position.
The subject image at the position in the Z direction, which is the focal point in this way, is input to the PC 50 as a video signal by the camera 40 via the microscope 41.
The PC 50 measures the pattern width and the like by performing image processing with application software.

AF processing is control for detecting the in-focus position of the image from the microscope 41 by moving the XY stage 45 up and down, and is an important control that greatly affects pattern width measurement accuracy.
For AF processing used in line width measuring equipment, for example, laser AF that measures the distance using a beam such as a laser, AF that uses the contrast of the video signal, and image processing that uses application software in the computer There are methods such as AF. Among them, AF using video signals, which is inexpensive and fast, is generally used. AF using a video signal calculates a focus position from a luminance value of a video obtained by moving up and down the Z movement mechanism of the apparatus (see, for example, Patent Document 1).

In calculating the focus value, the luminance signal of a certain video area designated by the operator is differentiated and the integrated value is used. Then, the height (movement position) of Z with a large integral value (that is, with a large focus value) is set as the in-focus height.
Also, this means that the luminance signal contains a lot of high-frequency components (those with a strong waveform amplitude after differentiation), the focus value is large, and the luminance waveform contains few high-frequency components (the amplitude of the waveform after differentiation processing is large). The smaller one) means that the focus value becomes smaller. For this reason, since the focused image contains a lot of high-frequency components, it is possible to detect the focused point by capturing a place where the focus value increases.

A conventional AF control method will be described with reference to FIGS. FIG. 2 is a flowchart showing an example of conventional AF processing.
First, in the Z movement range setting step 1, the movement amount in the vertical (height) direction of the XY stage 45 is specified by the application software of the PC 50.
Next, in the Z initial value moving step 6, the height of the XY stage 45 is moved to the initial position for AF.
Thereafter, the movement start step 7 starts the movement of the XY stage 45 in the vertical direction.
In the camera image capturing step 8, while the XY stage 45 is moving in the vertical direction, the camera 40 captures a subject image in the image area, and the image is continuously captured by the AF device 52.

In a differentiation processing step 24, a high-frequency component is extracted by performing differentiation on the captured video luminance signal, and the value is integrated within a certain video region, thereby calculating a focus value.
This focus value increases as the number of high frequency components increases. That is, the larger the focus value, the closer to the focal point, and the smaller the focal value, the farther from the focal point.
In the focus value creation step 10, these high-frequency components are converted into focus values within a range that can be discriminated by the application software of the PC 50 and output to the PC 50.

  In the peak value update step 11, the PC 50 operates the application software to determine whether or not the focus value is the maximum value. That is, the maximum focus value stored in the PC 50 is compared with the focus value input from the AF device 52 to the PC 50. If the maximum focus value stored in the PC 50 is larger or the same, the original maximum focus value stored is maintained. If the input focus value is larger than the maximum focus value stored in PC 50, the input focus value is changed to the focus value instead of the original stored maximum focus value. The maximum focus value is updated as the maximum value.

In the movement range determination step 12, the Z position set in the Z movement range setting 1 is determined. If it is outside the movement range, the process proceeds to the Z movement stop step 13, and if it is within the movement range, the process returns to the video capturing step 8.
In the Z movement stop step 13, the vertical movement of the XY stage 45 is stopped.
In Z initial position moving step 14, the XY stage 45 is moved again to the initial position for AF.
Further, in the image capturing step 16, the image from the camera 40 is captured by the AF device 52. In a differentiation process step 25, a high frequency component of the luminance signal of the video is extracted, and in a focus value creation step 18, a focus value is generated.

In the peak value vicinity determination step 19, it is determined whether or not the focus value is a value near the maximum focus value stored or updated in the peak value update step 11. If it is determined that it is not near, the process proceeds to the video capture step 16, and if it is determined that it is close, the process proceeds to the Z movement stop step 20.
In the Z movement stop step 20, the movement of the XY stage 45 is stopped on the assumption that AF processing has been completed (focused).
The neighborhood means, for example, within a predetermined value with respect to the maximum value.

After focusing, in the video capturing step 21, the video is captured in the PC 50, and in the line width measuring step 22, the pattern width is measured by image processing.
Finally, in the result display step 23, the measurement result is displayed on the monitor 51.

Japanese Patent Laid-Open No. 8-211281

In the above-described prior art, in the case of a subject having a plurality of in-focus positions, such as when the subject has a step in the height direction, where the in-focus position is included in the area for calculating the focus value, where is the in-focus position? I didn't know. Further, if the setting area is reduced to narrow down the area for calculating the focus value, the contrast of the luminance signal is lowered, the S / N is deteriorated, and there is a problem that the focal point is not converged.
An object of the present invention is to provide a focusing method and a focusing device that can solve the above-described problems, are not easily affected by unevenness on the surface of a subject, and can be focused at the most suitable position, and a measuring device using the focusing method. is there.

  In order to achieve the above object, according to the present invention, in the generation of the focus value, the inclination of the waveform of the designated area of the video luminance signal (hereinafter referred to as the luminance waveform) is used as the focus value.

That is, in the focusing method of the present invention, in the focusing method of a measuring apparatus having a stage on which a subject is placed and having a moving mechanism for adjusting the distance between the microscope and the camera and the stage, an image from the microscope is input to the camera, The inclination of the luminance waveform in a predetermined range is calculated as the focus value while moving the distance by the moving mechanism, and if the calculated focus value is within the range of the predetermined maximum focus value, the distance when the focus value is calculated is calculated. It is characterized by focusing.
Preferably, the range of the predetermined maximum focus value is obtained by inputting the video from the microscope to the camera, calculating the inclination of the luminance waveform of the predetermined range as the focus value while moving the distance by the moving mechanism, and calculating the calculated focus value. Is the maximum value.

Further, the focusing device of the present invention is a focusing device of a measuring device having a stage on which a subject is placed, a microscope, a camera, a moving mechanism for adjusting a distance between the microscope and the camera, and the stage, and an image processing unit. The image processing unit of the apparatus inputs the video from the microscope to the camera, calculates the inclination of the luminance waveform in a predetermined range as the focus value while moving the distance between the microscope and the camera and the stage by the moving mechanism, and calculates the calculated focus If the value is within the range of a predetermined maximum focus value, the distance when the focus value is calculated is set as the focal point.
Preferably, when the predetermined maximum focus value is obtained, the image processing unit displays a locus of inclination of the calculated luminance waveform on the monitor, and calculates a locus of inclination of the luminance waveform calculated according to the parameter set by the operator. Is displayed on the monitor.

  In addition, the measuring apparatus of the present invention includes an image processing unit in a measuring apparatus including a stage on which a subject is placed, a microscope, a camera, a moving mechanism that adjusts a distance between the microscope and the camera, and the stage, and an image processing unit. Inputs the image from the microscope to the camera, calculates the inclination of the luminance waveform in the predetermined range as the focus value while moving the distance by the moving mechanism, and the calculated focus value is within the range of the predetermined maximum focus value If there is, the distance when the focus value is calculated is the focal point.

According to the present invention, AF processing can be performed at a place where the focal point is most desired to be affected by the unevenness of the surface.
Also, with the maximum focus value set as a reference, the Z height at the point when the focus value falls within the predetermined range is recognized as the in-focus position when performing AF processing on other subjects. , AF processing becomes faster. For this reason, inspection time can also be shortened.

  The present invention has a function of calculating the inclination of a certain range of luminance waveform of a video signal of a camera in image processing of a line width measuring apparatus having an XY stage and having a Z movement mechanism, and a certain range while performing Z movement. This is an AF method and apparatus, and a line width measuring device, which has a function of setting the maximum inclination of the luminance waveform as a focal point by calculating the inclination of the luminance waveform, and using the inclination of the luminance waveform as a focus value for autofocus.

In general, the luminance signal has a steep waveform near the focal point. However, when there are a plurality of irregularities and steps on the surface of the subject, there may be several focal points in the height direction. Therefore, depending on the subject, if there are minute irregularities, it was impossible to predict which height would be the focal point, depending on the type of AF and the location where AF was performed.
By applying the present invention, the focus value is set to the inclination of the luminance waveform at the same location as the image area where the line width measurement is performed, so that it can be focused at the most suitable position without being affected by surface irregularities.

  FIG. 5 is a diagram showing that a mask of a TFT substrate on which a pattern (pattern 601 is formed) is placed as an object (subject 501) on the XY stage. FIG. 7 is a diagram for explaining an optical path, an image, and a luminance waveform of the subject 501. FIG. 7 shows a microscope image and a luminance waveform of the Nth line when a subject 501 having a strip-like pattern with a high reflectivity as shown in FIG. 5 (the part other than the pattern has a low reflectivity) is placed. It is a thing.

7 (1) and 7 (2), (a) is a cross-sectional view schematically showing how light irradiated from a microscope is reflected on a pattern formed on a mask of a TFT substrate.
Fig. 7 (1) is at a height close to the focal point, and the image of the subject magnified by the microscope and captured by the camera reflects light at a highly reflective part (pattern 601) as shown in (b). Therefore, the luminance is increased, and the luminance is decreased in other portions because the reflection of light is weak. This luminance waveform is steep as shown in (c).

Fig. 7 (2) shows a case where the height is almost out of focus. The image of the subject magnified by the microscope and captured by the camera is shown in Fig. 7 (1) ( Compared with b), the image is blurred and the luminance waveform is also smooth as shown in (c).
Thus, the luminance waveform has a steep waveform at the focal point.

  FIG. 6 is a diagram showing that a mask of a TFT substrate on which a pattern is formed (formation of patterns 601 and 602) is placed on the XY stage as a subject (subject 502). FIG. 8 is a diagram for explaining the optical path, image, and luminance waveform of the subject 502. In FIG. 8, as shown in FIG. 6, when a subject having two strip-shaped patterns 601 and 602 with different reflectivities with different heights (low reflectivity other than the pattern) is placed on the XY stage. It shows the microscope image and the luminance waveform of the Nth line.

Fig. 8 (1) shows the case where the pattern 601 is in focus, and the image of the subject magnified by the microscope and captured by the camera is a fine image around the pattern 601 as shown in (b). However, the area around the pattern 602 is blurred.
As shown in (c), this luminance waveform has a steep waveform around the pattern 601 and a gentle waveform around the pattern 602.

Fig. 8 (2) shows the case where the pattern 602 is in focus, and the image of the subject magnified by the microscope and captured by the camera is a blurred image around the pattern 601 as shown in (b). However, the area around the pattern 602 is a fine image.
As shown in (c), this luminance waveform has a gentle waveform around the pattern 601 and a sharp waveform around the pattern 602.

If the image area setting for creating the autofocus value is a setting that includes both pattern 601 and pattern 602, the conventional method will converge to the in-focus height of pattern 601 or pattern 602. I do not understand.
It is also possible to set the image area for creating the autofocus value so that either the pattern 601 or the pattern 602 can be accommodated. Change will be less, S / N will be poor, and it will be difficult to accurately focus.

Therefore, in the present invention, as shown in FIG. 9, an area to be subjected to AF processing is set in the horizontal direction of the luminance waveform, and the maximum value and the minimum value are detected. FIG. 9 is a diagram for explaining a method of detecting a focal position according to an embodiment of the present invention.
In FIG. 9, assuming that the maximum value of the luminance waveform is 100% and the minimum value is 0%, for example, 70% and 30% positions are calculated (hereinafter 70%, ie, the upper slice level, 30%, ie, the lower side). The focus value is the slope of a straight line connecting the two points.

In this way, even if a very small area is set as a focus value calculation area, the maximum value can be set as the focus value as long as there is a gradient of the luminance waveform.
Note that the luminance waveform is for the Nth line of the image. However, in actual line width measurement, it is usually the case that multiple lines are selected and the width is measured from the average edge position of those lines. There are many.
Accordingly, in the case of the present invention, as in the case of line width measurement, stable AF processing can be performed by calculating the average inclination of not only one line but a plurality of lines.

  An embodiment of the present invention will be described with reference to FIGS. 1 and 3. FIG. 1 is a flowchart showing an embodiment of AF processing of the present invention. In FIG. 1, an upper / lower slice level determination step is added between the Z movement range setting step 1 and the Z initial value movement step 6 to the flowchart of FIG. 2, and an inclination detection step 9 is performed instead of the differentiation processing step 24. It is what was used.

In FIG. 1, as a preparation before measurement, the operator moves to the Z movement range setting step 1 through the interface shown in FIG. 4 (details will be described later) of the PC 50 application software. Set the Z movement range upper limit and Z movement range lower limit, which are the amount of movement in the vertical direction (Z direction).
Further, in the upper and lower slice level setting step 2, similarly, the upper slice level and the lower slice level are set using the interface as shown in FIG. 4 of the application software of the PC 50 and measurement is started.

When measurement starts, first, in Z initial value movement step 6, the Z movement range setting step 1 moves to the upper or lower limit of the Z movement range. That is, the XY stage 45 is driven by the Z moving mechanism 44 and moved to the initial position for AF processing.
Thereafter, in the movement start step 7, the XY stage 45 is moved in the vertical direction from the initial position for AF processing. Whether to move to the upper limit value or to the lower limit value in the initial value movement step 6 is determined by the “upper to lower” or “lower to upper” parameters in the search direction of FIG. When “top to bottom” is set).
In addition, whether to move in the vertical direction at the start of movement 7 is determined by the parameters “from top to bottom” and “from bottom to top”. “From top to bottom” moves to the upper limit with initial value movement 6 and then moves downwards with movement start 7. “From bottom to top” moves to the lower limit and then moves upward.

While the XY stage 45 is moving, the camera image capturing step 8 continues to capture the camera 40 image into the AF device 52.
For the captured image, the inclination of the luminance waveform in the area specified in the inclination detection step 9 is calculated, and the focus value is generated in the focus value generation step 10 from this inclination.
In the peak value update step 11, the application software of the PC 50 determines whether or not the focus value is the maximum value based on these focus values, and if it is the maximum value, the maximum value of the focus value is updated.
That is, the PC 50 operates the application software to determine whether the focus value is the maximum value. That is, the maximum focus value stored in the PC 50 is compared with the focus value input from the AF device 52 to the PC 50. If the maximum focus value stored in the PC 50 is larger or the same, the original maximum focus value stored is maintained. If the input focus value is larger than the maximum focus value stored in PC 50, the input focus value is changed to the focus value instead of the original stored maximum focus value. The maximum focus value is updated as the maximum value.

In the movement range determination step 12, the Z position set in the Z movement range setting 1 is determined. If it is outside the movement range, the process proceeds to the Z movement stop step 13, and if it is within the movement range, the process returns to the video capturing step 8.
In the Z movement stop step 13, the vertical movement of the XY stage 45 is stopped.
With the processing so far, the target maximum focus value has been determined. Next, a process for searching for the maximum focus value is performed.

  In the Z initial position moving step 14, the XY stage 45 is moved again to the initial position for AF processing, that is, the upper limit value or lower limit value of the Z movement range. Then, in the movement start step 15, the robot moves upward or downward. The upper limit value or lower limit value, or the upward or downward direction, is the same as the Z initial movement step 6 and the movement start step 7.

Further, in the video capturing step 16, the video acquired by the camera 40 is captured into the AF device 52.
In the inclination detection step 17, the inclination of the luminance waveform in the designated area is calculated, and the focus value generation step 18 generates a focus value from this inclination.

In the peak value vicinity determination step 19, it is determined whether or not the focus value is a value near the maximum focus value stored or updated in the peak value update step 11. If it is not near, move to video capture step 16 and repeat the process. If it is determined that it is in the vicinity, the process proceeds to Z movement stop step 20.
In the Z movement stop step 20, the movement of the XY stage 45 is stopped on the assumption that AF processing has been completed (focused).

“Near” means that the focus value enters the range between the absolute value of the maximum focus value calculated in the process of steps 7 to 13 and a certain percentage (coefficient) of 100% or less and the maximum focus value. is there.
After capturing the focal point, in the video capturing step 21, the video is captured again in the PC 50, and in the line width measuring step 22, the pattern width is measured by image processing.
Finally, the measurement result is displayed in the result display step 23.
This completes the sequence of line width measurement using a series of tilt AF.

  FIG. 4 is a view showing an embodiment of an AF parameter setting screen of the application software of the PC 50 using the AF processing method of the present invention. The setting screen of FIG. 4 is displayed on the display screen of the monitor 51 of FIG. 3, for example, and is set by the GUI (Graphical User Interface) operation by the operator using a pointing device such as a mouse or a keyboard (not shown). Is possible.

As shown in FIG. 4, the Z movement range setting Z movement range upper limit and Z movement range lower limit, upper slice level and lower slice level, speed, search direction, etc. are set in the parameter setting unit 102 of the AF parameter setting screen 101. Enter in the box part.
For example, enter the numerical value of the upper limit of the Z movement range in the box 103 using the keyboard. Similarly, enter the lower limit of the Z movement range in box 104. Also, box 105 is the value of the upper slice level, box 106 is the value of the lower slice level, box 107 is the vertical movement speed of the XY stage, and box 108 is the search direction, that is, from the top or bottom. Select whether to move the XY stage from the menu displayed by input or mouse operation. Further, the maximum focus value is displayed on the right side of FIG. 4 by re-searching the maximum inclination by pressing the test button 110 by GUI operation or the like.

  The focus curve display unit 111 in FIG. 4 can use the tilt AF before actually measuring the line width. To try it out, press the test button 110 to color-code the locus of focus values calculated in steps 7 to 13 in Fig. 1 as a solid line and the locus of focus values calculated in steps 15 to 20 as a broken line. It is easy to distinguish by displaying the thickness, thickness, and other decorations. Note that the horizontal axis of the focus curve display unit 111 is the movement distance in the Z direction, and the vertical axis is the focus value.

In FIG. 4, when the AF parameter setting is completed, the operator presses an OK button 112 to end the AF parameter setting screen.
Also, if the operation is not satisfactory with the AF parameter settings that have been made so far, press the CANCEL button to delete the previous settings.
Whether the parameter setting is good or bad can be determined easily because the larger the size of the focus curve of the focus curve display unit 111 is, the wider the range is in the upper and lower ranges and the left and right ranges.

After completing the AF parameter setting as described above, if the same lot or pattern is used, the same AF parameter setting value can be used to repeatedly focus. And measurement can be repeated. That is, it can be repeated by executing Step 14 to Step 23 from the step of FIG.
Also, when focusing is performed in the present invention and used for line width measurement, appearance inspection, etc., the line width and the like are calculated by image processing in the above-described prior art and the embodiments of the invention, but the subject is set. Therefore, by automatically focusing on the microscope image, the microscope image can be directly observed or the image can be observed on the monitor.

As described with reference to FIG. 9, parameter setting can be performed quickly by setting parameters according to the procedure shown in FIG. 4 using the gradient of the luminance waveform as the focus value. Further, since the setting result can be tested (trially used) and viewed visually while viewing the display screen, the skill level of the operator is also unnecessary.
In addition, the AF processing time is used for measurement and observation, and the slope of the luminance waveform in a limited area is obtained and used as the focus value, enabling high-speed processing and shortening the measurement and observation time. .

The flowchart which shows an example of AF process of this invention. The flowchart which shows an example of the conventional AF process. The block diagram which shows the schematic structure of a line | wire width measuring apparatus. The figure which shows one Example of the AF parameter setting screen of this invention. The figure which showed having put the subject on the XY stage. The figure which showed having put the subject on the XY stage. The figure for demonstrating the optical path of a to-be-photographed object 1, an image, and a luminance waveform. The figure for demonstrating the optical path of the to-be-photographed object 2, an image, and a luminance waveform. The figure for demonstrating the method to detect the focus position of one Example of this invention.

Explanation of symbols

  40: Camera, 41: Microscope, 42: X movement mechanism, 43: Y movement mechanism, 44: Z movement mechanism, 45: XY stage, 46: Light source, 50: PC, 51: Monitor, 52: AF device, 101: AF parameter setting screen, 102: Parameter setting section, 103 to 109: Box, 110: Test button, 111: Focus curve display section, 112: OK button, 113: CANCEL button, 501, 502: Subject, 601, 602: Pattern .

Claims (5)

In a focusing method of a measuring apparatus having a stage on which a subject is placed and having a moving mechanism for adjusting a distance between the microscope and the camera and the stage,
While moving a predetermined distance by the moving mechanism, a luminance waveform is obtained from the image of the subject magnified by the microscope and imaged by the camera, and the maximum value and the minimum value of the luminance waveform of the predetermined range of the subject are detected. A straight line connecting two intersection points at the upper slice level and the lower slice level that are selected and set in advance from 0 to 100%, with the maximum value of the luminance waveform being 100% and the minimum value being 0%. The focus method is characterized in that if the calculated focus value is within a range of a predetermined maximum focus value, the distance when the focus value is calculated is used as the in-focus point. . 2. The focusing method according to claim 1, wherein the range of the predetermined maximum focus value is a luminance waveform from an image of the subject enlarged by the microscope and imaged by the camera while moving a predetermined distance by the moving mechanism. the determined, detects the maximum value and the minimum value of the luminance waveform in the predetermined range of the subject, the maximum value of the luminance waveform 100% the minimum value 0% is selected from among previously 0-100% An in- focus method characterized in that an inclination of a straight line connecting two intersections at a set upper slice level and lower slice level is calculated as a focus value, and the calculated focus value is a maximum value. In a focusing apparatus of a measuring apparatus having a stage on which a subject is placed, a microscope, a camera, a moving mechanism that adjusts the distance between the microscope and the camera and the stage, and an image processing unit,
The image processing unit obtains a luminance waveform from the image of the subject magnified by the microscope and imaged by the camera while moving a predetermined distance by the moving mechanism, and calculates the maximum luminance waveform of the predetermined range of the subject. Value and minimum value are detected, the maximum value of the luminance waveform is 100%, the minimum value is 0%, and the intersection between the upper slice level and the lower slice level selected and set in advance from 0 to 100% The inclination of a straight line connecting two points is calculated as a focus value, and if the calculated focus value is within the range of a predetermined maximum focus value, the distance when the focus value is calculated is set as the focal point. Feature focusing device.   4. The focusing apparatus according to claim 3, wherein the image processing unit displays a locus of inclination of the calculated luminance waveform on the monitor when obtaining the predetermined maximum focus value, and according to a parameter set by an operator. An in-focus device characterized in that the calculated inclination trajectory is displayed on the monitor. In a measuring apparatus having a stage for placing a subject, a microscope, a camera, a moving mechanism for adjusting a distance between the microscope and the camera and the stage, and an image processing unit,
The image processing unit obtains a luminance waveform from the image of the subject magnified by the microscope and imaged by the camera while moving a predetermined distance by the moving mechanism, and calculates the maximum luminance waveform of the predetermined range of the subject. Value and minimum value are detected, the maximum value of the luminance waveform is 100%, the minimum value is 0%, and the intersection between the upper slice level and the lower slice level selected and set in advance from 0 to 100% The inclination of a straight line connecting two points is calculated as a focus value, and if the calculated focus value is within the range of a predetermined maximum focus value, the distance when the focus value is calculated is set as the focal point. Characteristic measuring device.

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