JP2000266992A - Automatic focusing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify focusing work. SOLUTION: An objective lens 6 or a stage 7 is moved along an optical axis direction, a focusing evaluation is executed based on a digital signal from an A/D converter 23a in accompaniment to the moving therein, and focusing control for an observing object 8 on the stage 7 is conducted based on a result thereof. For example, the stage 7 is moved along an XY direction to move the observing object 8, and the focusing control for the object 8 is temporarily stopped until a factor of detected movement of the object 8 is removed, when a condition moved hereinbefore is detected by a stage-movement detecting part 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focusing device used for an optical instrument such as a microscope and an optical measuring device.

[0002]

2. Description of the Related Art Conventionally, an optical instrument such as a microscope or an optical measuring instrument has used an automatic focusing device for automatically focusing on an observation object.

[0003] As such an automatic focusing device, there have been conventionally known Japanese Patent Application Laid-Open No. 58-217909 and Japanese Patent Application Laid-Open
An apparatus disclosed in Japanese Patent Application No. 0-42725 is known.

FIG. 4 shows an automatic focusing apparatus disclosed in these publications. A linear luminous flux emitted from a measurement light source 1 is regulated to a parallel luminous flux via a collimator lens 2 and then polarized. The light passes through the beam splitter 3 and the λ / 4 plate 4 and is converted into circularly polarized light.
Then, only the measurement light beam having a predetermined wavelength is reflected and irradiates the observation object 8 on the stage 7 via the objective lens 6. The reflected light flux reflected on the surface of the observation object 8 is again passed through the objective lens 6 to the dichroic mirror 5.
, And transmits a part of the light to form an image at an imaging position 10 via the observation imaging lens 9, while reflecting the remaining part by the dichroic mirror 5 and transmitting the λ / 4 plate 4. And reflected by the polarizing beam splitter 3 as linearly polarized light shifted by 90 ° from the first linearly polarized light.
The light is received by the light receiving element 12 via 1. Then, the image forming state of the reflected light beam received by the light receiving element 12 is detected by the arithmetic and control unit 13, and its output is input to the drive unit 14, which causes the stage 7 or the objective lens 6 to move in the optical axis direction. The optical system is focused by moving it.

[0005]

By the way, in such an automatic focusing apparatus, the focusing operation is performed during the focusing operation due to, for example, replacement of the objective lens or switching of the microscope. Since it is no longer possible to continue, it is necessary to switch off and automatically stop the focusing operation. Then, in order to restart the focusing operation after the necessary operation is completed, the start switch of the focusing operation is operated again.

However, when the focusing operation is stopped in the middle of the focusing operation, the focusing operation is restarted by operating the focusing operation start switch again each time the cause of the stoppage is eliminated. When applied to an observation microscope in the wafer substrate surface inspection process performed in the above, the start switch is re-operated each time, the tact time for this is added, and the work efficiency is reduced. There was a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an automatic focusing apparatus which can simplify a focusing operation.

[0008]

According to the first aspect of the present invention,
Automatic focusing operation means for automatically moving the objective lens or the stage in the optical axis direction to perform focusing control on the observation target on the stage, and detecting a factor that makes the focus evaluation impossible or impossible. It comprises a factor detecting means and a control means for temporarily stopping the focusing control on the observation object until the factor is removed by the output from the factor detecting means.

According to a second aspect of the present invention, in the first aspect of the present invention, the control means focuses on the observation target object on condition that the focus evaluation can be performed even if there is an output from the factor detection means. It is characterized by enabling control.

As a result, according to the present invention, when there is a factor that makes it impossible or impossible to perform focusing for automatic focusing, automatic focusing is temporarily stopped, and these factors are eliminated. Then, the focusing operation can be automatically resumed, so that the focusing operation can be simplified.

Further, according to the present invention, even if there is a factor that makes it impossible or impossible to perform focusing for automatic focusing, if there is a possibility of focusing, it is possible to shift to focusing if there is a possibility of focusing. A good focusing operation can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an epi-illumination type microscope to which the focusing device of the present invention is applied. In the figure,
Reference numeral 21 denotes a focusing optical system. The focusing optical system 21 has the same configuration as that described with reference to FIG. 4 described above, and the same parts as those in FIG.

The focusing optical system 21 has a display unit 2
2 are connected. The display unit 22 is provided with the CCD camera 2
2a and a monitor 22b, a CCD camera 22a is arranged at an imaging position 10 of the focusing optical system 21 via the observation imaging lens 9, and the observation object 8 is imaged.
The captured image of the observation object 8 is displayed on the monitor 22b.

A control unit 23 is connected to the focus optical system 21. The control unit 23 includes an A / D converter 23
a and a CPU 23b, of which the CPU 23
b, an objective lens switching detection unit 25 and a speculum change detection unit 26 as factor detection means for detecting a factor that makes it impossible or impossible to perform focusing evaluation for automatic focusing in addition to the driving device 24. , A stage movement detecting section 27 and a loader / unloader operation detecting section 28 are connected.

The A / D converter 23a converts an electric signal corresponding to the reflected light beam condensed by the light receiving element 12 of the focusing optical system 21 into a digital signal, and inputs the digital signal to the CPU 23b. I am trying to do it.

The objective lens switching detecting section 25 detects the operating state of a revolver (not shown) for switching the magnification of the objective lens 6 in the focusing optical system 21 and the like. The speculum change detection unit 26 detects a switching operation state such as a change in the microscopic method of the microscope. The stage movement detection unit 27 detects a state in which the stage 7 is moved in the X and Y directions to move the observation target object 8. The loader / unloader operation detection unit 28 detects a state of replacement of the observation target 8 on the stage 7.

As the factor detecting means, focus control evaluation such as detection of a drive control signal of each optical element or stage or an output signal from a sensor for detecting switching or movement, and further detecting a command signal of an operation section are provided. What is necessary is just to be able to detect a factor that makes it impossible or impossible to focus.

The CPU 23b evaluates the focus based on the digital signal from the A / D converter 23a to determine whether or not the focusing operation is possible, and based on the result, the driving device 24 drives the stage 7 or the objective. The lens 6 is moved in the optical axis direction to perform automatic focusing of the optical system, and the objective lens switching detection unit 25, the speculum change detection unit 26, the stage movement detection unit 27, the loader / unloader operation detection unit 2
When an output corresponding to various factors that make it impossible to perform focusing evaluation or disable focusing for automatic focusing is given from FIG. 8, the result of focusing evaluation on the digital signal from the A / D converter 23a at this time indicates that: The automatic focusing is temporarily stopped until these factors are eliminated.

Here, the focus evaluation means whether or not the positional relationship between the objective lens 6 and the observation object 8 is in a focused state, and in which direction and how far from the focused state if not in a focused state. It is evaluation such as whether it is.

Next, the operation of the embodiment configured as described above will be described.

First, the observation object 8 is placed on the stage 7, and an automatic focusing operation for automatically performing focusing is set.

From this state, in the focusing optical system 21,
The observation object 8 on the stage 7 is irradiated with a measurement light beam, and the light beam reflected on the surface of the observation object 8 is reflected by the light receiving element 12.
, The electric signal output from the light receiving element 12 is converted into a digital signal by the A / D converter 23a and input to the CPU 23b.

Then, in the CPU 23b, focusing evaluation is performed based on the digital signal from the A / D converter 23a, and it is determined whether or not the focusing operation is possible, and this determination result is output to the driving device 24. . As a result, the stage 7 or the objective lens 6 is moved in the direction of the optical axis, and automatic focusing is performed. The observation image of the observation object 8 obtained by such an automatic focusing operation is transmitted to the CC arranged at the imaging position 10 via the observation imaging lens 9 of the focusing optical system 21.
The image is captured by the D camera 22a and the monitor 22
b.

Next, in such an automatic focusing operation,
A case where the stage 7 is moved in the X and Y directions to move the observation target object 8, for example, which is a cause of the suspension, will be described.

In this case, the flowchart shown in FIG. 2 is executed.

First, in step 201, the focusing optical system 21
It is assumed that the focusing operation by the automatic focusing is performed. In order to move the observation object 8 in step 202 from the state of the focusing operation, the stage 7
May move in the X and Y directions, the stage movement detection unit 27 detects the movement of the stage 7 and outputs a detection output to the CPU 23 b of the control unit 23.

In step 203, the CPU 23b determines whether or not focus evaluation is possible or whether or not focus is possible based on the output from the stage movement detection unit 27. The focus evaluation here is an evaluation of whether the positional relationship between the objective lens 6 and the observation target object 8 is in a focused state, and in which direction and how far away from the focused state if the object lens 6 is not in the focused state. is there.

Here, if it is determined that the focus can be evaluated,
Returning to step 201, the driving operation for focusing is continued. On the other hand, when it is determined that the focus evaluation cannot be performed, the process proceeds to step 204, and the CPU 23b outputs a command to temporarily stop the automatic focusing.

In step 205, even if the focusing operation is temporarily stopped due to the occurrence of a factor that makes the focusing evaluation impossible or impossible, the focusing evaluation is determined. , Cancel the pause of the focusing operation,
The focusing operation is started. This step 205
If it is determined that focus evaluation cannot be performed, step 206
Thus, it is determined from the output of the stage movement detecting section 27 whether or not the movement of the observation target 8 has been completed. Here, if it is determined that the movement of the observation target object 8 is continuing, step 20 is performed.
Continue to maintain the paused state of 4. In addition, the observation object 8
When the end of the movement is determined, the process proceeds to step 207, and shifts to a focusing start sequence.

In this focusing start sequence, the flowchart shown in FIG. 3 is executed.

First, in step 301, the observation object 8 on the stage 7 is irradiated with a measurement light beam, and the light beam reflected on the surface of the observation object 8 is received by the light receiving element 12. The electric signal output from the light receiving element 12 is A /
When input to the CPU 23b via the D converter 23a,
In step 302, it is determined based on the digital signal of the A / D converter 23a whether or not the signal level allows focus evaluation.
Here, if it is determined that the signal level can be evaluated for focusing, the process proceeds to step 303, and an operation for driving into focus is executed based on the result of the focusing evaluation at this time. The operation of driving into focus here means that when the focus has not been reached by the focus evaluation, the objective lens 6 and the observation object 8 are used by utilizing the result (in which direction and how far from the focus). Is operated so that the positional relationship of (2) is in focus.

On the other hand, when it is determined in step 302 that the signal level is not a signal level that can be evaluated for focus, the process proceeds to step 304 to search for a position where a signal level that can be evaluated for focus is obtained. The search here refers to searching for a point at which focus evaluation can be performed while moving the entire range of possible positions of the objective lens 6 and the observation target 8.

Returning to step 302, it is determined again whether the signal level can be evaluated for focusing.

Therefore, in this case, the objective lens 6
Alternatively, the stage 7 is moved in the optical axis direction, focus evaluation is performed from a digital signal from the A / D converter 23a accompanying this movement, and focus control for the observation target 8 on the stage 7 is performed based on the result. For example, a stage 7 for changing the observation position on the observation object 8
Are moved in the X and Y directions, and when the stage movement detection unit 27 detects this state, the focusing control on the observation target 8 is temporarily stopped until the detected factor of the movement of the observation target 8 is removed. So, the operator
It is possible to finally obtain the in-focus state without considering the focusing operation at all when observing the observation object and without any knowledge of the focusing operation, and to simplify the focusing operation. realizable. And such an automatic focusing device, for example,
When applied to the observation microscope in the wafer substrate surface inspection process performed in the assembly line operation, the troublesome operation of re-operating the start switch every time the focusing operation is restarted can be omitted, so the tact time can be reduced, Work efficiency can be improved.

Even if there is a factor that makes it impossible to perform focus evaluation for automatic focusing, if there is a possibility of focusing, focus control for the observation object 8 can be continued. There is no need to pause the focusing operation when necessary,
An efficient focusing operation can be obtained.

In the above description, the case where the observation object 8 is moved by moving the stage 7 in the X and Y directions detected by the stage movement detection unit 27 as a factor for temporarily stopping the automatic focusing operation has been described. Detection unit 25
When a revolver (not shown) is operated to switch the magnification of the objective lens 6 detected by the microscope, when a change such as a change in the microscope inspection method detected by the microscope change detection unit 26 is performed, a loader / unloader operation detection is performed. In the case of replacing the observation target object 8 on the stage 7 detected by the unit 28, the automatic focusing operation is temporarily stopped in the same manner, and after the cause of the temporary stop is eliminated, the automatic focusing operation is stopped. The focusing operation is performed again.

Further, in the above-described embodiment, as an example for detecting a factor that makes it impossible to perform focusing evaluation for automatic focusing, an objective lens switching detection unit 25, a microscope change detection unit 26, a stage movement detection Although the unit 27 and the loader / unloader operation detecting unit 28 have been described, it goes without saying that the present invention can be applied to a unit that detects other factors. Also,
Factors that make it impossible to evaluate the focus for automatic focusing based on the control state of the controller for the objective lens switching, the change of the microscope, the movement of the stage, and the operation of the loader / unloader without using such various detection means. Can be detected.

Furthermore, in the above-described embodiment, an example has been described in which the focusing device of the present invention is applied to an epi-illumination type microscope. However, application to an optical instrument such as an optical measuring device is also possible.

[0040]

As described above, according to the present invention, when there is a factor that makes it impossible to evaluate the focus for automatic focusing, the automatic focusing is temporarily stopped, and these factors are eliminated. Then, the focusing operation can be automatically resumed, so that the focusing operation is not considered at all when observing the object to be observed, and even if there is no knowledge about the focusing operation, the focusing state is finally reached. And the focusing operation can be simplified.

Even if there is a factor that makes it impossible to perform focusing evaluation for automatic focusing, if there is a possibility of focusing, it is possible to shift to focusing, so that it is unnecessary to temporarily stop the focusing operation. As a result, an efficient focusing operation can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the embodiment;

FIG. 3 is a flowchart for explaining the operation of the embodiment;

FIG. 4 is a diagram showing a schematic configuration of an example of a conventional automatic focusing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measurement light source 2 ... Collimator lens 3 ... Polarization beam splitter 4 ... λ / 4 plate 5 ... Dichroic mirror 6 ... Objective lens 7 ... Stage 8 ... Observation target 9 ... Observation imaging lens 10 ... Imaging position 11 ... Imaging Image lens 12 ... Light receiving element 13 ... Calculation control device 14 ... Drive device 21 ... Focal optical system 22 ... Display unit 22a ... CCD camera 22b ... Monitor 23 ... Control unit 23a ... A / D converter 23b ... CPU 24 ... Drive unit 25 ... Objective lens switching detector 26. Microscope change detector 27. Stage movement detector 28. Loader / unloader operation detector

Claims (2)

[Claims] 1. An automatic focusing operation means for moving an objective lens or a stage in an optical axis direction to automatically perform focusing control on an observation target on the stage, and a focusing evaluation is impossible or the focusing can be performed. A factor detecting means for detecting a cause of disappearance; and a control means for temporarily stopping focusing control on the observation target object until the cause is removed by an output from the factor detecting means. Burning device. 2. The apparatus according to claim 1, wherein the control means enables focus control on the observation target object on condition that focus evaluation can be performed even when there is an output from the factor detection means. Automatic focusing device.