JPH10260363A - Microscope equipped with focus detecting means, and displacement measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a focus detecting device which can detect focus excellently even if the pupil diameter of the objective of a microscope varies. SOLUTION: Optical detection surfaces of optical detectors 18 and 19 of the focus detecting device are divided into >=3 optical detection parts outwardly from the center. When the pupil diameter of the object is small, a focus error signal is found by using the difference between the output of a more inside optical detection part 18a and the sum of outputs of more outside optical detection parts 18b and 18c. When the pupil diameter of the objective is large, a focus error signal is found by using the difference between the sum of the output of the two inside optical detection parts 18a and 18b and the sum of the output of the more outside optical detection part 18c. Consequently, at least two kind of focus error signals can be obtained according to the pupil diameter of the objective, so a better signal can be selected and used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the displacement of the surface of an object to be measured in a non-contact manner, which is used for automatic focusing of a microscope.

[0002]

2. Description of the Related Art Conventionally, focus detection methods include, for example,
A method called a differential beam size method is known.

FIG. 20 is a schematic configuration diagram of a conventional epi-illumination type microscope when a differential beam size type focus detection device is used for focus detection of the microscope and the focus detection device. FIG.
The device No. 0 includes an observation optical system of a microscope, an illumination optical system, and an autofocus optical system.

The observation optical system of the microscope includes a first objective lens 1
02, a second objective lens 103, and a bird's-eye view prism 104
And an eyepiece 105. First objective lens 10
A parallel optical path is formed between the second objective lens 103 and the second objective lens 103. In this parallel light path, a dichroic mirror 107 and a beam splitter 108 are installed at an angle of 45 degrees with respect to the optical axis 101 of the parallel light path. The dichroic mirror 107 has a characteristic of reflecting infrared light and transmitting visible light.

[0005] The illumination optical system of the microscope has an illumination light source 110 for emitting visible light and a condenser lens 111, and the illumination light beam is reflected by the beam splitter 108 and guided to the above-mentioned parallel optical path.

The autofocus optical system includes a light source 113 for emitting infrared light, a collimator lens 114, a beam splitter 115, a condenser lens 116, a beam splitter 117, a first photodetector 118, It has two photodetectors 119. The first photodetector 118 is located farther from the object 124 than the convergence point 120. On the other hand, the second photodetector 119 is installed closer to the test object 124 than the convergence point 121. Convergence point 1
Reference numeral 20 denotes a point where light converged by the condenser lens 116 and transmitted through the beam splitter 117 converges. The convergence point 121 is a point at which light converged by the condenser lens 116 and reflected by the beam splitter 117 converges.

As shown in FIG. 21, a light detecting section of the first light detector 118 and a light detecting section of the second light detector 119 have square central light detecting sections 118a and 119a, respectively.
It has photodetectors 118b and 119b surrounding it. In addition, these light detection units 118a, 118b, 1
19a and 119b are connected to operational amplifiers 129 and 130, respectively.
It is connected to the.

[0008] The operational amplifiers 129, 130 and 131 are arranged in the control unit 126. The test object 124 is mounted on a moving stage 125 that can move in the direction of the optical axis 101. The control device 126 controls the operation of the moving stage 125.

In the configuration shown in FIG. 20, a light beam emitted from a light source 113 and passing through a collimator lens 114 is reflected by a beam splitter 115, further reflected by a dichroic mirror 107, and
And forms an image on the test object 124. Test object 12
The light beam reflected from the test surface 123 passes through the objective lens 102, is reflected by the dichroic mirror 107, passes through the beam splitter 115, and enters the beam splitter 117.

As shown in FIG. 21, light spots 132 and 13 are formed on the photodetectors 118 and 119 by the first and second light beams split by the beam splitter 117.
3 are formed respectively. The light spot 132 formed on the first photodetector 118 increases when the objective lens 102 and the object 124 are separated from each other, and decreases when the object lens 102 and the object 124 approach each other. On the other hand, the light spot 133 formed on the second photodetector 119 becomes smaller when the objective lens 102 and the test object 124 are separated from each other, and becomes larger when they are closer to each other. (118a-118b)-(119a-119b) from the detection signals of both photodetectors 118, 119 by operational amplifiers 129, 130, 131.
If this signal is used as a focus error signal,
A focus error signal having an S-shaped characteristic is obtained.

Therefore, when the focus error signal is positive, it is possible to determine the front focus state, when the focus error signal is negative, it is possible to determine the rear focus state, and when the focus error signal is zero, it is possible to determine the focus state. It is possible to determine the position of the surface to be inspected from this differential signal and move the moving stage 125 up and down by the control device 126 to automatically adjust the position to the focused state.

Further, the displacement amount of the test object 124 can be measured from the focus error signal.

[0013]

When changing the observation magnification in a microscope, the microscope may be replaced with an objective lens having a different magnification (focal length). However, the pupil diameter of the objective lens of the microscope is usually different for each magnification. The diameter of the parallel light beam changes depending on the type of the objective lens, and the light spot diameter on the photodetector changes.

For this reason, depending on the objective lens, the light spot diameter is too small with respect to the size of the light detecting section and smaller than the diameter of the inner light detecting section, or the light spot diameter is too large. There may be a case where the diameter becomes larger than the diameter of the outer light detection unit. If the light spot diameter is too small or too large, focus detection cannot be performed properly. Specifically, when the light spot diameter is too small with respect to the size of the light detection unit, a flat area appears near the focal point of the S-shaped curve of the focus error signal. If the diameter of the light spot is too large with respect to the size of the light detection unit, the linear area near the focal point of the S-shaped curve of the focus error signal becomes narrow, the focus detection range becomes narrow, and The sensitivity of detection decreases.

Therefore, the focus detection device of the differential beam size type used in the conventional microscope has a problem that the type of objective lens of the microscope which can be used for focus detection is limited by the pupil diameter.

It is an object of the present invention to solve this problem and to provide a microscope which is provided with a focus detecting means even when the pupil diameter of the objective lens of the microscope changes.

[0017]

According to the present invention, there is provided a microscope having the following focus detecting device.

That is, an observation optical system including an objective lens, a stage for mounting the test object, and focus detecting means for detecting a displacement of the test object from a focal position of the objective lens are provided. An illumination optical system for irradiating the test object with illumination light through the objective lens, and a condensing optical system for converging a reflected light beam of the illumination light from the test object. Dividing means for dividing the reflected light beam into first and second light beams, first and second detecting means for detecting the first and second light beams, respectively, and first and second detecting means. Calculating means for calculating at least two types of focus error signals by calculating the detection result of
The first detection unit is disposed at a position farther from the object than a convergence point at which the first light beam is converged by the light-collecting optical system, and the second detection unit is configured such that the second light beam is The first and second light sources are arranged at a position closer to the test object than a convergence point converged by the light collecting optical system;
Detecting means for detecting a light flux of an optical axis portion, a light flux outside the light flux portion, and a light flux of a portion further away from the optical axis in the order outside the light flux portion among the first and second light fluxes, respectively, in total of three or more. And the calculating means includes the detecting unit
The difference between the output of the detection unit located at the center of the above detection units and the sum of the outputs of all the detection units located outside it is obtained for the first and second detection means, respectively. And a sum of outputs of two detectors near the center among the three or more detectors, and outputs of all detectors located outside of the first and second detectors. And a second calculation unit for obtaining a difference between the first focus error signal and the second focus error signal using the first and second detection means, respectively, and a microscope having focus detection means. It is.

[0019]

Embodiments of the present invention will be described below.

First, a microscope provided with a focus detection device according to a first embodiment of the present invention will be described with reference to FIG. The microscope shown in FIG. 1 includes an observation optical system, an illumination optical system, and an autofocus optical system.

The observation optical system includes a first objective lens 2 and a second objective lens 2.
It has an objective lens 3, a bird's-eye view prism 4, and an eyepiece 5. A parallel optical path is formed between the first objective lens 2 and the second objective lens 3. In this parallel optical path, a dichroic mirror 7 and a beam splitter 8 are installed at an angle of 45 degrees with respect to the optical axis 1 of the parallel optical path. The dichroic mirror 7 has a characteristic of reflecting infrared light and transmitting visible light.

The illumination optical system has an illumination light source 10 that emits visible light and a condenser lens 11. The illumination light beam emitted from the illumination optical system is reflected by the beam splitter 8 and guided to the above-mentioned parallel optical path.

The autofocus optical system includes a light source 13 for emitting infrared light, a collimator lens 14, a beam splitter 15, a condenser lens 16, and a beam splitter 1.
7, a first light detector 18, and a second light detector 19. As the light source 13, a semiconductor laser that emits infrared light was used. The first photodetector 18 is installed farther from the object 24 than the convergence point 20. On the other hand, the second photodetector 19 is installed closer to the test object 24 than the convergence point 21. The convergence point 20 is a point at which light converged by the condenser lens 16 and transmitted through the beam splitter 17 converges. The convergence point 21 is a point where the light is converged by the condenser lens 16 and the light reflected by the beam splitter 17 converges.

As shown in FIG. 2, the light detecting section of the first light detector 18 and the light detecting section of the second light detector 19 each have a light detecting section 18a having a square detection area at the center. 1
9a. Outside the photodetectors 18a, 1
Photodetectors 18b and 19b having a detection area surrounding 9a are arranged. Further, on the outside thereof, a light detecting unit 18 is provided.
b, light detecting portions 18c, 1 having a detection area surrounding 19b
9c is arranged. The respective light detection areas of the light detection units 18a to 18c and the light detection units 19a to 19c are:
The semiconductor substrate is formed by doping impurities. In FIG. 2, the adjacent light detection units are drawn so as to be in contact with each other. However, in practice, a dead area where light is not detected is formed between the adjacent light detection units.

Light detectors 18a to 18c, 19a to 19c
Are operational amplifiers 27, 28, 29, 30, 31, 32,
33, 34, 35 and 36. The operational amplifiers 27, 28, 29, and 30 are amplifiers that add two input signals, and are operational amplifiers 31, 32, 33, and 3,
Reference numerals 4, 35 and 36 denote amplifiers for differentiating the two input signals.

The operational amplifier 27 includes light detection units 18a, 18
The output of b is added. The operational amplifier 28 is connected to the light detector 18
b, 18c are added. The operational amplifier 31 makes a difference between the output of the photodetector 18a and the output of the operational amplifier 28. The operational amplifier 32 makes a difference between the output of the operational amplifier 27 and the output of the light detector 18c. On the other hand, the operational amplifier 29
Adds the outputs of the photodetectors 19a and 19b. The operational amplifier 30 adds the outputs of the light detectors 19b and 19c. The operational amplifier 33 makes a difference between the output of the photodetector 19a and the output of the operational amplifier 30. The operational amplifier 34 makes a difference between the output of the operational amplifier 29 and the output of the light detection unit 19c.

The operational amplifier 35 makes a difference between the output of the operational amplifier 31 and the output of the operational amplifier 33. Operational amplifier 36
Subtracts the output of the operational amplifier 32 from the output of the operational amplifier 34. Photodetectors 18a-18c, photodetectors 19a-
19c are | 18a | to | 18c |, |
When expressed as 19a | to | 19c |, the output of the operational amplifier 35 is (| 18a |-(| 18b | + | 18c |)).
− (| 19a | − (| 19b | + | 19c |)). Similarly, the output of operational amplifier 36 is
((| 18a | + | 18b |)-| 18c |)-((|
19a | + | 19b |)-| 19c |).

The operational amplifiers 27 to 36 are arranged in the control device 26. The test object 24 is mounted on a moving stage 25 that can move in the optical axis 1 direction. Control device 26
Controls the operation of the moving stage 25.

Next, the operation of each part of the microscope provided with the focus detecting device shown in FIG. 1 will be described.

The collimator lens 1 is emitted from the light source 13
The light beam passing through 4 is reflected by the beam splitter 15, further reflected by the dichroic mirror 7, enters the objective lens 2, and forms an image on the test object 24. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, passes through the beam splitter 15, and
And enters the beam splitter 17.

On the photodetectors 18 and 19, the first and second light beams split by the beam splitter 17 are used.
As shown in FIG. 2, light spots 37 and 38 are respectively formed. The spot diameter of the light spot 37 formed on the first photodetector 18 increases when the objective lens 2 and the object 24 are separated, and decreases when the object lens 2 and the object 24 approach each other. on the other hand,
Contrary to the light spot 37, the spot diameter of the light spot 38 formed on the second photodetector 19 becomes smaller when the objective lens 2 and the object 24 are separated from each other, and becomes larger when the object lens 2 and the object 24 come closer.

The pupil diameter of the objective lens 2 is small,
Is moved in the direction of the optical axis 1 so that the test surface 23 is
When the objective lens 2 having a pupil diameter such that the light spot 38 enters the inside of the light detection unit 19b and the light spot does not fall on the light detection unit 19c when the objective lens 2 is disposed at the focal position of 35 output (| 18a |-(|
18b | + | 18c |))-(| 19a |-(| 19b
| + | 19c |)) and using this signal as a focus error signal, a focus error signal having S-characteristics can be obtained.

On the other hand, the pupil diameter of the objective lens 2 is large, and the test surface 23 is moved in the direction of the optical axis 1 so that the test surface 23
When the light spot 38 is disposed at the focal position, the spot diameter of the light spot 38 is larger than the diameter of the light
When using the objective lens 2 having a pupil diameter such that light is irradiated onto the entire surface of the optical amplifier 36, the output of the operational amplifier 36 ((| 18a | +
| 18b |)-| 18c |)-((| 19a | + | 19)
If b |)-| 19c |) is used as a focus error signal, a focus error signal having an S-shaped characteristic can be obtained.

As described above, by selectively using the output of the operational amplifier 35, an S-shaped curve is drawn regardless of whether the pupil diameter of the objective lens 2 is small or large, and the vicinity of the focal point of the S-shaped curve is obtained. Can obtain a focus error signal having a wide linear region and good focus detection sensitivity.
When the focus signal is positive, it is possible to determine the front focus state, when the focus signal is negative, it is possible to determine the rear focus state, and when the focus signal is zero, it is possible to determine the focus state. It is possible to determine the position of the surface to be inspected from the focus error signal, and to move the moving stage 25 up and down by the control device 26 to adjust the position to a focused state. In this state, by observing the light emitted from the illumination light source 10 to the test object 24 with the observation optical system, the image of the test object 24 can be observed in a focused state.

Further, the displacement amount of the test object 24 can be measured from the focus error signal.

In the microscope with the focus detecting device of FIG. 1 of the first embodiment, the device is manufactured under the following conditions.
An experiment was performed to obtain focus error signals for a plurality of objective lenses having different pupil diameters.

The focal length of the condenser lens 16 is 40 mm, the distance between the convergence point 20 and the photodetector 18 is 6000 μm, the distance between the convergence point 21 and the photodetector 19 is 6000 μm, and the light detection of the photodetector 18 is performed. The size of the portion 18a is 350 μm × 350
μm, the size of the light detecting portion 18b is 950 μm × 950 μm,
The size of the light detecting portion 18c is 6000 μm × 6000 μm, and the size of the light detecting portion 19a of the light detector 19 is 350 μm × 35.
0 μm, the size of the photodetector 19b is 950 μm × 950 μm
m, the size of the light detection unit 19c is 6000 μm × 6000 μm
And

Then, as the objective lens 2, six types of lenses having different focal lengths and pupil diameters are used.
5 or the output of the operational amplifier 36, a focus error signal was obtained. FIGS. 3A to 3F show focus error signals at this time. In addition, FIG.
In (f), the horizontal axis indicates the amount of displacement of the test surface 23, and the vertical axis indicates the intensity of the focus error signal.

Under this condition, when the pupil diameter of the objective lens 2 is 3.6 mm or less, the output of the operational amplifier 35 is closer to the focal point of the S-shaped curve than the output of the operational amplifier 36 in the linear region. When a focus error signal close to a straight line is obtained and the pupil diameter of the objective lens 2 is 6.4 mm or more, the output of the operational amplifier 36 is closer to the focal point of the S-shaped curve than the output of the operational amplifier 35. A focus error signal having a wide linear range was obtained. Therefore, FIGS. 3A and 3B show focus error signals output from the operational amplifier 35, and FIGS. 3C to 3F show focus error signals output from the operational amplifier 36.

More specifically, FIG. 3A shows a case where an objective lens having a focal length of 1.33 mm and a pupil diameter of 2.4 mm is used as the objective lens 2 of the microscope, and the focus error obtained from the operational amplifier 35 is shown. It is a graph of a signal.

FIG. 3B shows a case where an objective lens having a focal length of 2 mm and a pupil diameter of 3.6 mm is used as the objective lens 2 of the microscope.
This is a graph of the focus error signal obtained from the operational amplifier 35.

FIG. 3C shows a case where an objective lens having a focal length of 4 mm and a pupil diameter of 6.4 mm is used as the objective lens 2 of the microscope.
Since the pupil diameter is large, the focus error signal obtained from the operational amplifier 36 is graphed.

FIG. 3D is a graph in which a focus error signal obtained from the operational amplifier 36 is graphed when an objective lens having a focal length of 10 mm and a pupil diameter of 9.2 mm is used as the objective lens 2 of the microscope. is there.

FIG. 3E shows a case where an objective lens having a focal length of 20 mm and a pupil diameter of 12 mm is used as the objective lens 2 of the microscope.
This is a graph of the focus error signal obtained from the operational amplifier 36.

FIG. 3F is a graph showing a focus error signal obtained from the operational amplifier 36 when an objective lens having a focal length of 40 mm and a pupil diameter of 10.4 mm is used as the objective lens 2 of the microscope. .

In the control device 26, in order to select either the output of the operational amplifier 35 or the output of the operational amplifier 36 as a focus error signal used for control, the control device 26 accepts an external selection. Means can be provided. Further, when a revolver that can be provided with a plurality of objective lenses and one of which can be selectively disposed on the optical axis 1 as the objective lens 2 is used, the revolver is disposed on the optical axis 1. The operational amplifier 3 is provided to the control device 26 in accordance with the objective lens 2 that has been set.
It is also possible to attach a means for transmitting the selection signal of 5 or the operational amplifier 36 to the revolver.

As described above, in the microscope with the focus detecting device according to the first embodiment, the electric signal processing circuit can be implemented by using the photodetector having the photodetector having the configuration as shown in FIG. With a simple operation of switching, a good focus error signal can be obtained for the objective lens 2 having a wide range of pupil diameters.

In the configuration of FIG. 1, a quarter-wave plate is provided between the dichroic mirror 7 and the beam splitter 15, the light source 13 is used as a light source for emitting linearly polarized light, and the beam splitter 15 is used as a polarized beam. With the configuration as the splitter, all the light reflected on the surface to be detected can be detected by the photodetectors 18 and 19, and the photodetector 1
Since the amounts of received light 8 and 19 increase, a focus error signal can be obtained with higher sensitivity even with a sample having a low reflectance.

Next, a microscope with a focus detection device according to a second embodiment of the present invention will be described with reference to FIG.

The configuration of FIG. 4 is similar to the configuration of FIG. 1 of the first embodiment in the observation optical system and the illumination optical system, but differs in the autofocus optical system.
The photodetectors 18 and 19 are directly fixed to the beam splitter 17 with an adhesive or the like. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals.

The autofocus optical system according to the second embodiment comprises a light source 13 for emitting infrared light, a collimator lens 14, a beam splitter 15, a condenser lens 16,
It has a beam splitter 17, a first photodetector 18 fixed to the beam splitter 17 with an adhesive, and a second photodetector 19. The first photodetector 18 is installed at a position farther from the object 24 than the convergence point 20, and the second photodetector 19 is provided.
Is positioned closer to the test object 24 than the convergence point 21, the beam splitter 17 is configured such that the convergence point 20 is located inside the beam splitter 17 and the convergence point 21 is located outside the beam splitter 17. Shape.

The form of the light detecting section of the first light detector 18 and the form of the light detecting section of the second light detector 19 are the same as those of the first embodiment, so that the description will be omitted.

The focus detection operation of the microscope with the focus detection device shown in FIG. 4 is the same as that of the first embodiment, and the description is omitted.

In the configuration of FIG. 4 of the second embodiment, since the photodetectors 18 and 19 are fixed to the beam splitter 17, alignment of optical elements can be easily performed. Therefore, there is an advantage that the focus error signal is not adversely affected by the positional deviation between the photodetectors 18 and 19 and the beam splitter optical element.

Next, a microscope with a focus detection device according to a third embodiment of the present invention will be described with reference to FIG.

The configuration of FIG. 5 differs from the configuration of FIG. 1 in the autofocus optical system. This will be described below. Note that the illumination optical system and the observation optical system are the same as those in FIG. In FIG. 5, the same parts as those in FIG. 1 are denoted by the same reference numerals.

The autofocus optical system according to the third embodiment comprises a light source 13 for emitting infrared light, a collimator lens 16, a prism 40, first and second photodetectors 18,
It has a Si substrate 41 on which the 19 is formed and a table 42.
In this embodiment, the light source 13 uses a semiconductor laser.
The prism 40 is fixed to the Si substrate 41 by an adhesive, and the light source 13, the collimator lens 16, and the Si substrate 4
1 is fixed to the base 42. The surface 44 of the prism 40 is coated with an optical thin film having a transmittance of 66.7% and a reflectance of 33.3%. The surface 43 of the prism 40 is coated with an optical thin film having a transmittance of 50% and a reflectance of 50%.

In the configuration shown in FIG. 5, the light emitted from the light source 13 passes through the surfaces 43 and 44 of the prism 40, and the light collimated by the collimator lens 16 is reflected by the dichroic mirror 7 to the objective lens 2. The light enters and is imaged on the test object 24 placed on the movable stage 25 movable in the optical axis 1 direction by the control device 26.

The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, passes through the collimator lens 16, and enters the surface 44 of the prism 40. Since the surface 44 of the prism 40 is coated with an optical thin film having a transmittance of 66.7% and a reflectance of 33.3%, 1/3 of the incident light is
The light is reflected at 4 and enters the photodetector 19. The remaining ／ of the light passes through the surface 44 and enters the surface 43 of the prism 40. The surface 43 of the prism 40 has a transmittance of 50% and a reflectance of 5
Since the optical thin film of 0% is coated, half of the incident light is incident on the photodetector 18.

The light detector of the first light detector 18 and the light detector of the second light detector 19 are the same as in the first embodiment, and the operation of focus detection is also the first embodiment. Therefore, the description is omitted.

The autofocus optical system having the structure shown in FIG.
Since the number of condensing lenses is one less than in the configuration of FIG. 1, the number of optical components is small. Moreover, since the photodetectors 18 and 19 are formed on one Si substrate 41, the photodetector 1
There is an advantage that the trouble of alignment between 8 and 19 can be omitted and the price can be reduced. Further, since the Si substrate 41, the light source 13, and the collimator lens 16 are fixed to the table 42, there is an advantage that the influence of the positional shift of the optical element on the focus error signal can be reduced.

The operational amplifiers 27, 28, 29, 3
0, 31, 32, 33, 34, 35 and 36 can be formed in the Si substrate 41 by a semiconductor process technology. This can further reduce the cost of the device.

Next, a microscope with a focus detection device according to a fourth embodiment of the present invention will be described with reference to FIG.

FIG. 6 shows that the light source 13 is a light source for emitting linearly polarized light,
Quarter-wave plate 45 between 6 and dichroic mirror 7
Is the same as the configuration of the third embodiment shown in FIG. 5 except that the optical film is provided and the characteristics of the optical thin films on the surfaces 43 and 44 are different. Specifically, a light source that emits linearly polarized light in the X direction is used as the light source 13. Prism 40
The surface 44 transmits 100% of linearly polarized light in the X direction,
50% transmittance and 5 reflectance for linearly polarized light in the Y direction
0% of the optical thin film is coated. The surface 43 of the prism 40 is coated with an optical thin film that transmits 100% of linearly polarized light in the X direction and reflects 100% of linearly polarized light in the Y direction. 6, the same components as those in FIG. 5 are denoted by the same reference numerals.

The linearly polarized light in the X direction emitted from the light source 13 that emits linearly polarized light passes through the surfaces 43 and 44 of the prism 40, is made parallel by the collimator lens 16, and becomes a quarter-wave plate. The light is converted into circularly polarized light by passing through 45, reflected by the dichroic mirror 7, incident on the objective lens 2, and placed on a movable stage 25 movable in the optical axis 1 direction by the controller 26. An image is formed on the object 24. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, and passes through the quarter-wave plate 45 again to be converted into linearly polarized light in the Y direction. And
After passing through the collimator lens 16, the surface 44 of the prism 40
Incident on. The surface 44 receives 100 linearly polarized light in the X direction.
%, And a transmittance of 50 for linearly polarized light in the Y direction.
%, And an optical thin film having a reflectivity of 50% is coated. The light reflected on the surface 44 is incident on the photodetector 19, and the light transmitted on the surface 44 is incident on the surface 43 of the prism 40.
10 linearly polarized light in the X direction is applied to the surface 43 of the prism 40.
An optical thin film that transmits 0% and reflects 100% of linearly polarized light in the Y direction is coated, and the light reflected by the surface 43 enters the photodetector 18. The form of the light detecting section of the first light detector 18 and the light detecting section of the second light detector 19 are the same as those in the first embodiment. The focus detection operation is the same as in the first embodiment, and a description thereof will be omitted.

In the configuration of FIG. 6, as in FIG. 5, the number of optical components of the autofocus optical system is small, and the photodetectors 18 and 19 are formed on one Si substrate 41. This has the advantage that the trouble can be saved and the price can be reduced. In addition, S
Since the i-substrate 41, the light source 13, and the collimator lens 16 are fixed, there is an advantage that the influence of the positional shift of the optical element on the focus error signal can be reduced.

The operational amplifiers 27, 28, 29, 3
0, 31, 32, 33, 34, 35, and 36 can be formed on the Si substrate 41 by a semiconductor process technique, so that the cost of the device can be further reduced.

Further, in the fourth embodiment, all the light reflected on the surface to be detected can be detected by the photodetectors 18 and 19, and the amount of light received by the photodetectors 18 and 19 increases. Even with a sample having a low reflectance, a focus error signal can be obtained with higher sensitivity. In addition, since there is no return light to the light source 13, the emission wavelength of the light source 13 can be stabilized even when a semiconductor laser is used as the light source 13.

Next, a microscope with a focus detection device according to a fifth embodiment of the present invention will be described with reference to FIG.

Since the configuration of the observation optical system and the illumination optical system in the configuration of FIG. 7 is the same as that of the first embodiment, FIG. 7 shows all of the illumination optical system and one of the observation optical systems. The parts are omitted. FIG. 7 of the fifth embodiment
In the configuration described above, the autofocus optical system includes a light source 13 that emits infrared light, a collimator lens 16, and a prism 4.
6 and the S on which the first and second photodetectors 18 and 19 are formed.
It has an i-substrate 41 and a table 42. A semiconductor laser was used as the light source 13. The prism 49 is fixed to the Si substrate 41 with an adhesive, and the light source 13 and the Si substrate 41 are
It is fixed to. An optical thin film having a transmittance of 50% and a reflectance of 50% is coated on the photodetectors 19 on the surfaces 47 and 48 of the prism 46. The surface 49 is coated with an optical thin film having a reflectance of 100%.

The light emitted from the light source 13 and the surface 4 of the prism 46
The light reflected by 7 and made parallel by the collimator lens 16 is reflected by the dichroic mirror 7, enters the objective lens 2, and forms an image on the test object 24. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, passes through the collimator lens 16, and enters the surface 47 of the prism 46. The surface 47 is coated with an optical thin film having a transmittance of 50% and a reflectance of 50%, so that one
/ 2 is transmitted through the surface 47 and enters the surface 48 of the prism 46. Since the optical detector 19 on the surface 48 is coated with an optical thin film having a transmittance of 50% and a reflectance of 50%, half of the light incident on this surface is transmitted through the surface 48,
The light enters the photodetector 19. The light reflected by the surface 48 is incident on the surface 49 of the prism 46. 100% reflectance on surface 49
The light reflected by the surface 49 is incident on the photodetector 18. The convergence point 20 of the lens 16 is aligned so as to be located on the surface 49.

The form of the light detecting section of the first light detector 18 and the form of the light detecting section of the second light detector 19 are the same as in the first embodiment, and a description thereof will be omitted. The operation of focus detection is the same as in the first embodiment, and a description thereof will be omitted.

As described above, in the fifth embodiment, the number of optical components of the autofocus optical system is small, and the photodetectors 18 and 19 are formed on one Si substrate 41. There is an advantage that labor can be saved and the price can be reduced. In addition, S
Since the i-substrate 41 and the light source 13 are fixed, there is an advantage that the influence on the focus error signal due to the displacement of the optical element can be reduced. Light source 1
Since the illumination light emitted from 3 to the object 24 does not pass through the inside of the prism 46, it is possible to irradiate the object 24 with strong light.

The operational amplifiers 27, 28, 29, 3
0, 31, 32, 33, 34, 35, and 36 can be formed on the Si substrate 41 by a semiconductor process technique, so that the cost of the device can be further reduced.

Next, the configuration of a microscope with a focus detection device according to a sixth embodiment of the present invention will be described with reference to FIG.

FIG. 8 is a schematic configuration diagram of a microscope focus detection apparatus according to a sixth embodiment of the present invention.

In the configuration of FIG. 8, since the configurations of the observation optical system and the illumination optical system are the same as those of the first embodiment, FIG. 8 shows all of the illumination optical system and one of the observation optical systems. The parts are omitted. In FIG. 8, the same parts as those in FIG. 5 are given the same numbers.

In the configuration of FIG. 8 of the sixth embodiment, the autofocus optical system includes a light source 13 for emitting infrared light,
Si substrate 4 on which collimator lens 16, beam splitter 50, and first and second photodetectors 18 and 19 are formed
1 and a table 42. The beam splitter 50 is fixed to the Si substrate 41 by an adhesive, and the light source 13, the collimator lens 16, and the Si substrate 41 are fixed to the base 42. On the photodetectors 19 on the surfaces 51 and 52 of the beam splitter 50, an optical thin film having a transmittance of 50% and a reflectance of 50% is coated.

The light emitted from the light source 13 passes through the beam splitter 50, is made parallel by the collimator lens 16, is reflected by the dichroic mirror 7, and
The light enters the objective lens 2 and is imaged on a test object 24 placed on a movable stage 25 movable in the direction of the optical axis 1 by a control device 26. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, and enters the surface 51 of the beam splitter 50. The surface 51 is coated with an optical thin film having a transmittance of 50% and a reflectance of 50%, and the light reflected on the surface 51 is incident on the surface 52 of the beam splitter 50. An optical thin film having a transmittance of 50% and a reflectance of 50% is coated on the photodetector 19 on the surface 52 of the beam splitter 50, and the light transmitted through the surface 52 enters the photodetector 19, The light reflected by the surface 52 of the beam splitter 50 is incident on the surface 53 of the beam splitter 50. The surface 53 is coated with an optical thin film having a reflectance of 100%.
The light reflected by 3 enters the photodetector 18. The lens and the prism 46 are positioned so that the convergence point of the lens 16 is located on the surface 53.

In the configuration of FIG. 8, the first photodetector 18
The form of the photodetector of the second photodetector 19 is as follows.
The description is omitted because it is the same as that of the first embodiment. The operation of focus detection is the same as in the first embodiment, and a description thereof will be omitted.

In the configuration of FIG. 8 of the sixth embodiment, the number of optical components of the autofocus optical system is small, and
Since the photodetectors 18 and 19 are formed on one Si substrate 41, there is an advantage that the labor for alignment can be omitted and the cost can be reduced. Further, since the Si substrate 41, the light source 13, and the collimator lens 16 are fixed to the table 42, there is an advantage that the influence of the positional shift of the optical element on the focus error signal can be reduced.

The operational amplifiers 27, 28, 29, 3
0, 31, 32, 33, 34, 35, and 36 can be formed on the Si substrate 41 by a semiconductor process technique, so that the cost of the device can be further reduced.

In the fifth and sixth embodiments, the fourth
A light source that emits linearly polarized light is used as the light source 13, a quarter-wave plate is inserted between the collimator lens 16 and the dichroic mirror 7, and the optical surface 47 of the prism 46 is When polarization separation is performed by making the thin film and the optical thin film on the surface 51 of the beam splitter 50 an optical thin film having polarization dependency, the photodetectors 18 and 19 can receive all the reflected light from the surface to be measured, and have high sensitivity. To obtain a focus error signal.

Next, a microscope with a focus detection device according to a seventh embodiment of the present invention will be described with reference to FIG. 9, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the configuration shown in FIG. 9, a multiple reflection plate 60 is provided between the condenser lens 16 and the beam splitter 17, and the other configuration is the same as that of the first embodiment. The surfaces 61 and 62 of the multiple reflection plate 60 are coated with a reflection film. By installing the multiple reflection plate 60 in this manner, even if the focal length of the condenser lens 16 is long, the distance between the condenser lens 16 and the beam splitter 17 can be shortened. Can be

In FIG. 9, the photodetector of the first photodetector 18 and the photodetector of the second photodetector 19 are the same as those in the first embodiment, so that the description is omitted. The operation of the focus detection is the same as that of the first embodiment, and the description is omitted.

Next, a microscope with a focus detection device according to an eighth embodiment of the present invention will be described with reference to FIG.
In FIG. 10, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the configuration of FIG. 10, the collimator lens 14
A diffraction grating 70 is provided between the beam splitter 15 and the beam splitter 15. Further, the shape of the light detectors of the light detectors 71 and 72 is different from the light detectors of the light detectors 18 and 19 of the first embodiment. The other configuration is the same as that of the first embodiment.

In the configuration of FIG. 10 according to the eighth embodiment, the autofocus optical system includes a light source 13 for emitting infrared light.
, A collimator lens 14, a diffraction grating 70, a beam splitter 15, a condenser lens 16, a beam splitter 17, a first photodetector 71, and a second photodetector 72.
And A semiconductor laser was used as the light source 13. First
The photodetector 71 of 3 is separated by the diffraction grating 70
The convergence points 20a, 20b, and 20c of the two lights are set apart from the object 24 to be measured. On the other hand, the second photodetector 72 is installed closer to the test object 24 than the convergence points 21a, 21b, and 21c.

The light detector of the first light detector 71 and the light detector of the second light detector 72 have three square light detectors 71a, 71b, 71c, 72a, as shown in FIG. 72
b and 72c are three sets each. Further, a signal processing circuit (not shown) is connected to these photodetectors.

The light emitted from the light source 13 and the collimator lens 1
The light beam passing through 4 is split by the diffraction grating 70 into three light beams (0-order light, -1st-order light, and + 1st-order light). The three light beams are reflected by the beam splitter 15, further reflected by the dichroic mirror 7, incident on the objective lens 2, and placed on a moving stage 25 movable by the control device 26 in the direction of the optical axis 1. The three light spots 73, 74, 75 are imaged on the object surface 23. Test object 24
The three light beams reflected by the test surface 23 pass through the objective lens 2, are reflected by the dichroic mirror 7, pass through the beam splitter 15, pass through the condenser lens 16,
The light enters the beam splitter 17.

On the photodetectors 71 and 72, light spots 76a, 76b, 76c, and 77a are formed by the first and second three light beams split by the beam splitter 17.
77b and 77c are respectively formed. First photodetector 71
The light spots 76a, 76b, 76c formed above are
The distance increases when the objective lens 2 and the object 24 are separated from each other, and decreases when the object lens 2 approaches the object 24. On the other hand, the second photodetector 72
The light spots 77a, 77b, 77c formed above are
Contrary to the light spots 76a, 76b and 76c, the distance decreases when the objective lens 2 and the object 24 are separated, and increases when the object lens 2 approaches the object.

By subjecting the signals of the photodetectors 76a and 77a to signal processing in the same manner as in the first embodiment, a focus error signal is obtained. Similarly, focus error signals are obtained from the photodetectors 76b and 77b and the photodetectors 76c and 77c, respectively.

In the configuration shown in FIG. 10, since the light beam separated by the diffraction grating 70 is applied to three different points on the surface 23 to be inspected, focus error signals of the surface 23 to be inspected for these three points are obtained. Can be Therefore, even when the surface 23 to be inspected has a step, if one of the three light spots on the surface 23 to be inspected hits the edge of the step, the focus error signal may be disturbed at that portion, but other portions may be disturbed. At two points, a normal focus error signal is obtained. Therefore, by averaging the three signals, it is possible to perform good focus detection even on a sample having a step. Further, the focus detection can be performed by selecting the best focus error signal among the three focus error signals.

The light detectors 71 and 72 are set at the convergence point 20.
a, 20b, 20c, 21a, 21b, 21c, the light spots 76a, 7
Adjacent light spots among 6b, 76c and 77a, 77b, 77c may partially overlap. When the light spots partially overlap each other, a photodetector having a multi-segment type photodetector as shown in FIG. 22 is used.

When the pupil diameter of the objective lens is small, the output of the light detecting unit 78e and the light detecting units 78a, 78b, 78c, 78d, 7d for the light spot 71a of the light detector 71 are determined.
8f, 78g, 78h, 78i, 78j, 78k, 78
The difference between the sum of the outputs of 1, 78m, 78n, 78o, 78p, and 78q is obtained by an operational amplifier. Also, the photodetector 72
Of the light spot 77a, the output of the light detection unit 79e and the light detection units 79a, 79b, 79c, 79d, 79
f, 79g, 79h, 79i, 79j, 79k, 79
The difference between the sum of the outputs of 1, 79m, 79n, 79o, 79p, and 79q is obtained by an operational amplifier. Then, the output difference between the two operational amplifiers is further obtained by the operational amplifier, thereby obtaining a focus error signal for the light spots 76a and 77a.

Further, regarding the light spot 76b of the light detector 71, the output of the light detection unit 78o and the light detection unit 78c,
78d, 78e, 78f, 78g, 78h, 78i, 7
8j, 78k, 78l, 78m, 78n, 78p, 78
q, 78r, 78s, 78t, 78u, 78v, 78
The difference from the sum of the outputs of w, 78x, 78y, 78z and 78A is obtained by an operational amplifier. Similarly, for the light spot 77b of the light detector 72, the output of the light detection unit 79o and the light detection units 79c, 79d, 79e, 79f, 79g, 79h,
79i, 79j, 79k, 79l, 79m, 79n, 7
9p, 79q, 79r, 79s, 79t, 79u, 79
The difference between the sum of the outputs of v, 79w, 79x, 79y, 79z, and 79A is obtained by an operational amplifier. Then, the output difference between the two operational amplifiers is further obtained by the operational amplifier, so that a focus error signal for the light spots 76b and 77b can be obtained.

Further, regarding the light spot 76c of the light detector 71, the output of the light detector 78y and the light detector 78m,
78n, 78o, 78p, 78q, 78r, 78s, 7
8t, 78u, 78v, 78w, 78x, 78z, 78
The difference between the sum of the outputs of A, 78B and 78C is obtained by an operational amplifier. In addition, regarding the light spot 77c of the light detector 72, the output of the light detection unit 79y and the light detection units 79m, 79m
n, 79o, 79p, 79q, 79r, 79s, 79
t, 79u, 79v, 79w, 79x, 79z, 79
The difference from the sum of the outputs of A, 79B and 79C is obtained by an operational amplifier. Then, the output difference of the good-matching amplifier is further obtained by the operational amplifier, thereby obtaining a focus error signal for the light spots 76c and 77c.

Thus, focus error signals for three light spots when the pupil diameter of the objective lens 2 is small are obtained.

On the other hand, when the pupil diameter of the objective lens is large,
Regarding the light spot 76a of the photodetector 71, the light detection unit 7
8b, 78d, 78e, 78f, 78i, 78j, 78
k and the sum of the outputs of the light detectors 78a, 78c, 78g, and 7
8h, 78l, 78m, 78n, 78o, 78p, 78
The difference between q and the sum of the outputs is obtained by an operational amplifier. Further, regarding the light spot 77a of the light detector 72, the light detecting section 79
b, 79d, 79e, 79f, 79i, 79j, 79k
And the photodetectors 79a, 79c, 79g, 79
h, 79l, 79m, 79n, 79o, 79p, 79q
The difference from the sum of the outputs is obtained by the operational amplifier. Then, the difference between the two operational amplifiers is further obtained by the operational amplifier to obtain a focus error signal for the light spots 76a and 77a.

Further, regarding the light spot 76b of the photodetector 71, the light detection units 78i, 78j, 78k, 78n, 7
8o, 78p, 78s, 78t, 78u,
Photodetectors 78c, 78d, 78e, 78f, 78g, 7
8h, 78l, 78m, 78q, 78r, 78v, 78
The difference from the sum of the outputs of w, 78x, 78y, 78z and 78A is obtained by an operational amplifier. Further, regarding the light spot 77b of the photodetector 72, the light detection units 79i, 79j, 79
k, 79n, 79o, 79p, 79s, 79t, 79u
And the photodetectors 79c, 79d, 79e, 79
f, 79g, 79h, 79l, 79m, 79q, 79
r, 79v, 79w, 79x, 79y, 79z, 79A
The difference from the sum of the outputs is obtained by the operational amplifier. Then, the difference between the outputs of the two operational amplifiers is further obtained by the operational amplifiers, thereby obtaining focus error signals for the light spots 76b and 77b.

Further, the light spot 76c of the photodetector 71
For the photodetectors 78s, 78t, 78u, 78x,
The sum of the outputs of 78y, 78z and 78B and the light detection unit 78
m, 78n, 78o, 78p, 78q, 78r, 78
The difference between the sum of the outputs of v, 78w, 78A, and 78C is obtained by the operational amplifier. Further, regarding the light spot 77c of the photodetector 72, the light detection units 79s, 79t, 79u,
The sum of the outputs of 79x, 79y, 79z, and 79B, and the photodetectors 79m, 79n, 79o, 79p, 79q, 79r,
The difference from the sum of the outputs of 79v, 79w, 79A, and 79C is obtained by an operational amplifier. Then, the difference between the outputs of the two operational amplifiers is further obtained by the operational amplifier, thereby obtaining a focus error signal for the light spots 76c and 77c.

As a result, focus error signals for three points on the test surface 23 when the pupil diameter of the objective lens 2 is large can be obtained.

In the configuration shown in FIG. 10 of the eighth embodiment, the light beam from the light source 13 is divided by the diffraction grating 70, and three points on the test surface 23 are irradiated with light. 1
By using a semiconductor laser in which three light emitting units are arranged in an array as 3 and without using the diffraction grating 70,
Light can be applied to three points on the test surface 23. The number of points on the surface 23 to be irradiated with light is not limited to three.
Four or more points can be provided. In this case as well, a focus error signal can be obtained for each point on the surface 23 to be detected by preparing the light detectors of the light detectors 71 and 72 in a number corresponding to the number of light spots.

In the first to eighth embodiments described above, the photodetector of the photodetector has a square shape at the center, but is not limited to this shape.
A circle as shown in FIGS. 12A and 12B or a rectangle as shown in FIG. In the case of FIG. 12C, the light detection unit 88c
2 is regarded as a signal from the light detection unit 18a in FIG. 2, and the sum signal of the signal from the light detection unit 88b and the signal from the light detection unit 88d in FIG. 12C, and the sum signal of the signal from the light detection unit 88a and the signal from the light detection unit 88e in FIG. 12C is regarded as the signal from the light detection unit 18c in FIG. And a focus error signal similar to that obtained by the photodetector of FIG. In addition, when the light detection unit is circular as shown in FIGS. 12A and 12B, there is no anisotropy. Therefore, the direction dependency on the focus error signal due to the placement of the test object is smaller than when the light detection unit is square. Has the effect of disappearing.

Next, the configuration of a microscope with a focus detection device according to a ninth embodiment of the present invention will be described with reference to FIG.

In the configuration shown in FIG. 13, a slit 80 is provided between the light source 13 and the collimator lens 14. Further, the form of the light detecting sections of the light detectors 81 and 82 has a configuration as shown in FIG. Other configurations are the same as those in FIG. In FIG. 13, the same components as those in FIG. 1 are denoted by the same reference numerals.

The autofocus optical system having the configuration shown in FIG. 13 comprises a light source 13 for emitting infrared light, a slit 80, a collimator lens 14, a beam splitter 15, a condenser lens 16, a beam splitter 17, It has one photodetector 81 and a second photodetector 82. As the light source 13, a semiconductor laser was used. FIG. 14 shows the slit 80 as viewed from the front. The first light detector 81 has a convergence point 20.
Rather than the test object 24. On the other hand, the second photodetector 82 moves the object 2
4 is installed in the vicinity. The photodetector of the first photodetector 81 and the photodetector of the second photodetector 82 have three rectangular photodetectors as shown in FIG. These photodetectors are connected to the same signal processing circuit as in the first embodiment.

In the configuration of FIG. 13 of the ninth embodiment, the slit light forms an image on the surface 23 to be measured. That is, the light source 1
A part of the light emitted from the light source 3 passes through the slit 80, and the light beam that has passed through the collimator lens 14
5, further reflected by the dichroic mirror 7, enters the objective lens 2, and forms a slit image on the test surface 23. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, passes through the beam splitter 15, passes through the condenser lens 16, and passes through the beam splitter 1.
7 is incident.

On the photodetectors 81 and 82, the first and second light beams split by the beam splitter 17 are used.
Each slit image is formed.

The focus detection method is the same as that of the first embodiment, and a description thereof will be omitted.

In the configuration of FIG. 13 of the ninth embodiment, since a linear image is irradiated onto the surface 23 to be inspected of the object 24, a part of the linear image is Even if it hits the step,
In other parts, a normal focus error signal can be obtained. Therefore, even when there is a step on the surface 23 to be detected, the focus error signal is less likely to be affected by the step.

Further, in the configuration of FIG. 13, a linear image is formed by the slit 80, but the light emitted from the light source 13 is condensed by a cylindrical lens so that it is located at the position of the slit 80 in FIG. Similar effects can be obtained by forming a linear image. In this case, the slit 80 becomes unnecessary.

Next, the configuration of a microscope with a focus detecting device according to a tenth embodiment of the present invention will be described with reference to FIG.

In the configuration of FIG. 16, the same parts as those of FIG. 1 are denoted by the same reference numerals.

In the configuration of FIG. 16 of the tenth embodiment,
Actuators 92 and 93 are connected to the light detectors 90 and 91, and can move the light detectors 90 and 91 in the optical axis direction. Further, the shape of the light detection unit is different from that of the first embodiment. Except for this, the configuration is the same as that of the first embodiment, and the description is omitted.

The autofocus optical system includes a light source 13 for emitting infrared light, a collimator lens 14, a beam splitter 15, a condenser lens 16, and a beam splitter 1.
7, a first light detector 90 and a second light detector 91. The first photodetector 90 is installed farther from the object 24 than the convergence point 20. On the other hand, the second photodetector 91 is installed closer to the test object 24 than the convergence point 21. The photodetector of the first photodetector 90 and the photodetector of the second photodetector 91 have two square photodetectors 90a, 90b, 91a and 91b as shown in FIG. I have. Further, these light detection units 90a, 90b, 91
a and 91b are connected to operational amplifiers 92, 93 and 94, respectively.

The collimator lens 1 is emitted from the light source 13
The light beam passing through 4 is reflected by beam splitter 15, further reflected by dichroic mirror 7, incident on objective lens 2, and placed on moving stage 25 movable by control device 26 in the direction of optical axis 1. An image is formed on the inspection object 24. The light beam reflected from the test surface 23 of the test object 24 passes through the objective lens 2, is reflected by the dichroic mirror 7, passes through the beam splitter 15, passes through the condenser lens 16, and enters the beam splitter 17.

On the photodetectors 90 and 91, the first and second light beams split by the beam splitter 17 are used.
As shown in FIG. 17, light spots 95 and 96 are respectively formed. The light spot 95 formed on the first photodetector 90 increases when the objective lens 2 and the test object 24 are separated from each other, and decreases when the object lens 2 approaches the object lens 2. On the other hand, the light spot 96 formed on the second photodetector 91 becomes smaller when the objective lens 2 and the test object 24 are separated from each other, and becomes larger when they are closer to each other. Operational amplifiers 92, 93, and 9 are obtained from the detection signals of
4, (90a-90b)-(91a-91b) is obtained, and this signal is used as a focus error signal.
A focus error signal having character characteristics is obtained.

At this time, if the pupil diameter of the objective lens is too large or the pupil diameter of the objective lens is too small, the actuators 92 and 93 are driven to drive the photodetectors 90 and 91.
Is moved in the optical axis direction, the dimensions of the light spots 95 and 96 on the photodetectors 90 and 91 at the in-focus position can be made constant, and a good focus error signal can be obtained.

When the focus signal is positive, the front focus state is set,
When it is negative, it can be determined that it is in the back focus state, and when it is zero, it can be determined that it is in focus. It is possible to determine the position of the surface to be inspected from this differential signal and move the moving stage 25 up and down by the control device 26 to automatically adjust the position to the focused state.

Further, the displacement amount of the test object 24 can be measured from the focus error signal.

In the tenth embodiment, the same effect can be obtained by changing the focal length of the zoom lens 16 by providing the condenser lens 16 as a zoom lens without providing the actuators 92, 92. Can be

Next, a displacement measuring apparatus according to an eleventh embodiment of the present invention will be described with reference to FIG.

In the displacement measuring apparatus shown in FIG. 18 according to the eleventh embodiment, the illumination optical system, the observation optical system, the dichroic mirror 7, and the stage 25 are removed from the microscope provided with the focus detecting device according to the first embodiment. Things. Other configurations are the same as those of the focus detection device according to the first embodiment.

In FIG. 18, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In the displacement measuring device shown in FIG.
Of the test surface 23 in the optical axis 1 direction is measured.

The operation of the displacement detection is the same as the operation of the focus detection of the first embodiment, and the description is omitted.

In the displacement measuring device shown in FIG.
The pupil diameter of the objective lens changes depending on the magnification (focal length) of the objective lens. However, in the displacement measuring device of FIG. 18, even when the magnification (focal length) of the objective lens is changed, a good focus error signal can be obtained. Therefore, the displacement of the test object 24 can be obtained from the focus error signal, and a displacement measuring device that can change the displacement measurement range by changing the magnification (focal length) of the objective lens 2 is realized. Since the resolution of displacement measurement changes as the displacement measurement range changes, a displacement measurement device with variable resolution can be provided.

Next, a displacement measuring apparatus according to a twelfth embodiment of the present invention will be described with reference to FIG.

In the displacement measuring apparatus according to the twelfth embodiment, the illumination optical system, the observation optical system, the dichroic mirror 7, and the stage 25 are removed from the microscope with a focus detection device according to the third embodiment. Other configurations are the same as those of the focus detection device according to the third embodiment. The displacement measuring device according to the twelfth embodiment measures the displacement of the test object 24 in the optical axis 1 direction. In FIG. 19, the same components as those in FIG. 5 are denoted by the same reference numerals.

The operation of detecting the displacement by the configuration shown in FIG. 19 is the same as the operation of detecting the focus in the third embodiment, so that the description is omitted.

The displacement measuring device shown in FIG. 19, similarly to the displacement measuring device shown in FIG. 18, changes the magnification (focal length) of the objective lens and provides a good focus error signal even when the pupil diameter of the objective lens changes. The displacement of the test object 24 can be obtained from the focus error signal. Therefore, a displacement measurement device that can change the displacement measurement range by changing the magnification (focal length) of the objective lens 2 is realized.

Further, in the displacement measuring apparatus shown in FIG. 19, the number of optical components is small, and the photodetectors 18 and 19 are formed on one Si substrate 41. It has the advantage that it can be reduced. Further, since the Si substrate 41, the light source 13, and the collimator lens 16 are fixed to the table 42, there is an advantage that the influence of the positional shift of the optical element on the focus error signal can be reduced.

The operational amplifiers 27, 28, 29, 3
It is possible to form 0, 31, 32, 33, 34, 35, 36 (not shown in FIG. 19) on the Si substrate 41 by a semiconductor process technology, thereby further reducing the cost of the device. it can.

Although the semiconductor laser is used as the light source 13 in each of the first to twelfth embodiments, a light emitting diode may be used.

Further, although a light source that emits infrared light is used as the light source 13, a visible light light source may be used. When using a visible light source, a beam splitter is used instead of a dichroic mirror.

In the first embodiment, as the photodetectors 18, 19, etc., a semiconductor substrate in which a detection region is formed by doping impurities is used. For example, a CCD can be used for 19 and the like.
In that case, an appropriate signal processing circuit is required to process the output of the CCD corresponding to each light detection unit such as the light detectors 18 and 19.

In each of the first to twelfth embodiments, the light detector 18 shown in FIG.
Although a photodetector divided into three photodetectors from the center to the outside as in a, 18b, and 18c was used, the present invention is not limited to this. It is also possible to use a photodetector having four or more photodetectors. Also in this case, according to the size of the light spot on the photodetector, the sum of the outputs of the arbitrary detection unit and the detection unit inside the detection unit and the detection unit outside the arbitrary detection unit are detected. The difference between the output and the sum is obtained by each photodetector, and the difference between these difference results is obtained.
A focus error signal can be obtained according to the pupil diameter of the objective lens.

In the above-described embodiment, for example, as shown in FIG. 2, the operational amplifier 35 outputs (| 18a |-(| 1
8b | + | 18c |))-(| 19a |-(| 19b |
+ │19c│)) is output, and the operational amplifier 36 outputs ((│18a│ + │18)
b |)-| 18c |)-((| 19a | + | 19b |)
− | 19c |), so that two types of focus error signals are always output. However, the present invention is not limited to a configuration in which two or more types of focus error signals are always calculated and output as described above.
Only the calculation to obtain the type of focus error signal is performed and 1
A configuration in which only the focus error signal of the type is output may be employed.

For example, an arithmetic circuit can be constituted by a selection circuit for selecting the output of the detection section, an addition circuit, and a difference circuit. Here, the first and second detectors 18, 19
, Are referred to as a first detection unit, a second detection unit,..., An m-th detection unit in order from the inside. The selection circuit selects the outputs of the first to i-th (i <m) detection units among the detection units of the first detector 18 and causes the addition circuit to add the outputs. Further, the sum of the outputs of the (i + 1) th to mth detection units is added to the addition circuit. Then, the difference circuit calculates the difference between the sum of the outputs of the first to i-th detection units and the sum of the outputs of the (i + 1) -th to m-th detection units. Similarly, the second detector 1
For No. 9, the selection circuit selects the outputs of the first to i-th detection units and causes the addition circuit to add them. Also, i +
The sum of the outputs of the first to m-th detection units is added to the adding circuit. Then, the difference circuit calculates the difference between the sum of the outputs of the first to i-th detection units and the sum of the outputs of the (i + 1) -th to m-th detection units. Then, the difference result obtained for the first detector 18 and the difference result obtained for the second detector 19 are further differentiated to obtain a focus error signal. Such an operation can be executed by assembling an operation circuit, or can be executed as software by causing a processing device to execute an operation program created in advance.

In this method, the value of i of the detection unit selected by the selection circuit is set by the user by referring to the curve shape of the output focus error signal graph, or the value of the output focus error signal is selected. It can be configured to be automatically set according to the shape of the curve of the graph.
As a result, although only one focus error signal is output, an optimal focus error signal for focus detection and displacement measurement can be obtained.

The value of i used for the operation of the first photodetector 18 and the value of i used for the operation of the second photodetector 19 can be set to different values. By setting i to different values in this manner, the photodetector 18 and the convergence point 20
The same effect can be obtained as when the distance between the photodetector 19 and the convergence point 21 is relatively adjusted with respect to the distance.

[0144]

As described above, even when the pupil diameter of the objective lens of the microscope changes, it is possible to provide a microscope having a good focus detecting means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a microscope with a focus detection device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a photodetector of a photodetector of the microscope with the focus detection device according to the first embodiment of the present invention.

FIGS. 3A to 3F are graphs showing focus error signals obtained by a microscope with a focus detection device according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a schematic configuration of a microscope with a focus detection device according to a second embodiment of the present invention.

FIG. 5 is a block diagram illustrating a schematic configuration of a microscope with a focus detection device according to a third embodiment of the present invention.

FIG. 6 is a block diagram illustrating a schematic configuration of a microscope with a focus detection device according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram illustrating a schematic configuration of a part of a microscope with a focus detection device according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram illustrating a schematic configuration of a part of a microscope with a focus detection device according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram illustrating a schematic configuration of a microscope with a focus detection device according to a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a schematic configuration of a microscope with a focus detection device according to an eighth embodiment of the present invention.

FIG. 11 is an explanatory diagram showing a configuration of a photodetector of a photodetector of a microscope with a focus detection device according to an eighth embodiment of the present invention.

FIGS. 12A to 12C are explanatory diagrams illustrating another configuration example of the light detection unit of the light detector of the microscope with the focus detection device according to the first to eighth embodiments of the present invention.

FIG. 13 is a block diagram illustrating a schematic configuration of a microscope with a focus detection device according to a ninth embodiment of the present invention.

FIG. 14 is a front view showing a shape of a slit used in a microscope with a focus detection device according to a ninth embodiment of the present invention.

FIG. 15 is an explanatory diagram illustrating a configuration of a light detection unit of a photodetector of a microscope with a focus detection device according to a ninth embodiment of the present invention.

FIG. 16 is a block diagram showing a schematic configuration of a microscope with a focus detection device according to a tenth embodiment of the present invention.

FIG. 17 is an explanatory diagram showing a configuration of a photodetector of a photodetector of a microscope with a focus detection device according to a tenth embodiment of the present invention.

FIG. 18 is a block diagram illustrating a schematic configuration of a displacement measuring device according to an eleventh embodiment of the present invention.

FIG. 19 is a block diagram showing a schematic configuration of a displacement measuring device according to a twelfth embodiment of the present invention.

FIG. 20 is a block diagram showing a schematic configuration of a conventional microscope with a focus detection device.

FIG. 21 is an explanatory diagram showing a configuration of a photodetector of a photodetector of a conventional microscope with a focus detection device.

FIG. 22 is an explanatory diagram showing another example of the light detection unit of the light detector of the microscope with the focus detection device according to the eighth embodiment of the present invention.

[Explanation of symbols]

2, 102 ... Objective lens 7, 107 ... Dichroic mirror 13, 113 ... Light source 14, 114 ... Collimator lens 16, 116 ... Condenser lens 15, 17, 50, 115, 117 ..Beam splitters 18, 19, 71, 72, 81, 82, 90, 91, 1
18, 119 ... photodetectors 18a, 18b, 19a, 19b, 71a, 71b, 7
1c, 72a, 72b, 72c, 88a, 88b, 88
c, 88d, 88e, 90a, 90b, 91a, 91
b, 118a, 118b, 119a, 119b... photodetector 23, 123... surface 24, 124... object 25, 125... stage 26, 126. 28, 29, 30, 31, 32, 33, 34, 3,
5, 36, 92, 93, 94, 129, 130, 131
... Operational amplifiers 37, 38, 76a, 76b, 76c, 77a, 77
b, 77c, 132, 133 ... light spot 40, 46 ... prism 41 ... Si substrate 42 ... table 45 ... quarter-wave plate 60 ... multiple reflection plate 70 ...・ Diffraction grating 80 ・ ・ ・ Slit 92, 93 ・ ・ ・ Actuator

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G03B 13/36 G03B 3/00 A (72) Inventor Kazuya Okamoto 3-2-3 Marunouchi, Chiyoda-ku, Tokyo Nikon Corporation Inside

Claims (9)

[Claims] An observation optical system including an objective lens, a stage for mounting a test object, and focus detection means for detecting a displacement of the test object from a focal position of the objective lens. An illumination optical system for irradiating the test object with illumination light through the objective lens; and a condensing optical system for converging a reflected light beam of the illumination light from the test object. Splitting means for splitting the reflected light beam into first and second light beams, first and second detecting means for detecting the first and second light beams, respectively,
And calculating the detection result of the second detection means,
Calculating means for obtaining at least two kinds of focus error signals, wherein the first detecting means is located at a position farther from the object than a convergence point at which the first light beam is converged by the light-collecting optical system. The second detection means is arranged at a position closer to the test object than a convergence point at which the second light beam is converged by the light-converging optical system. The first and second detection means Of the first and second light beams, three or more detectors are combined in order to detect the light beam in the optical axis portion, the light beam outside the light beam portion, and the light beam in a portion further away from the optical axis in order outside the light beam portion. The arithmetic means includes: a difference between the output of the detection unit located at the center of the three or more detection units and the sum of the outputs of all the detection units located outside the first detection unit;
And the second detecting means, and using these, the first
A first calculation unit for obtaining a focus error signal of
The difference between the sum of the outputs of the two detection units close to the center of the above detection units and the sum of the outputs of all the detection units located outside of them is obtained for the first and second detection means, respectively. And a second calculation unit for obtaining a second focus error signal using the above components. 2. A microscope provided with focus detecting means according to claim 1, wherein said first and second detecting means each have three detecting portions, and a detecting means located at the center of said first detecting means. A first detection unit, a detection unit outside the first detection unit as a second detection unit, a detection unit outside the second detection unit as a third detection unit, and a detection unit located at the center of the second detection unit. When the unit is a fourth detection unit, the detection unit outside the fourth detection unit is a fifth detection unit, and the detection unit outside the fifth detection unit is a sixth detection unit. The difference between the output of the first detection unit of the first detection unit and the sum of the outputs of all the detection units located outside the first detection unit of the first detection unit is determined. 3 The output of the detection unit and the second
Calculating a first focus error signal by obtaining a difference from the sum of outputs of all the detection units located outside the third detection unit of the detection means, and further obtaining a difference between the two difference results; The calculation unit is configured to calculate a sum of outputs of the first detection unit and the second detection unit of the first detection unit, and a sum of outputs of all detection units located outside the second detection unit of the first detection unit. And the sum of the outputs of the third and fourth detectors of the second detector and the sum of all detectors located outside the fourth detector of the second detector. And a second focus error signal is obtained by calculating a difference between the two difference results. 3. A microscope provided with focus detecting means according to claim 1, wherein said illumination optical system converts said illumination light beam into a plurality of light beams in order to irradiate said light beam onto a plurality of points on said test object. The light-collecting optical system and the splitting means collect and split the plurality of illumination light fluxes, respectively, and the first and second detection means are provided from a plurality of points on the test object. Wherein the calculating means obtains at least the first and second focus error signals for each of the reflected light fluxes from a plurality of points of the test object. Microscope with means. 4. The microscope provided with the focus detecting means according to claim 1, wherein the illumination optical system irradiates a linear light onto the object to be inspected, and the first and second detecting means A microscope provided with focus detection means, wherein the shape of the detection portion at the center is linear in order to receive the reflected light flux of the linear light. 5. An observation optical system including an objective lens, a stage for mounting a test object, and focus detection means for detecting a displacement of the test object from a focal position of the objective lens, The focus detection unit, an illumination optical system for irradiating the test object with illumination light through the objective lens, and a condensing optical system for converging the reflected light flux of the illumination light from the test object, Splitting means for splitting the reflected light beam into first and second light beams, first and second detecting means for detecting the first and second light beams, respectively,
And a calculating means for calculating a focus error signal by calculating a detection result of the second detecting means, wherein the first detecting means detects a first light beam that receives a light beam near an optical axis of the first light beam. And a second detection unit for detecting a light beam outside the first detection unit, wherein the second detection unit receives a light beam near an optical axis of the second light beam. At least a third detection unit, and a fourth detection unit for detecting a light beam outside the third detection unit, wherein the first detection unit converges the first light beam by the condensing optical system. And the second detecting means is arranged at a position closer to the test object than the convergence point at which the second light beam is converged by the condensing optical system. The first and second detection means are provided 1st and 2nd
A microscope equipped with a focus detecting means, wherein a moving means for moving the detecting means toward or away from the convergence point is attached. 6. An objective lens disposed at a position facing the object to be inspected, an illumination optical system for irradiating the object to be illuminated with illumination light through the objective lens, and A condensing optical system for converging the reflected light beam of the illumination light, a dividing means for dividing the reflected light beam into first and second light beams, and a first means for detecting the first and second light beams, respectively. And a second detecting means, and calculating means for calculating at least two kinds of focus error signals by calculating the detection results of the first and second detecting means, wherein the first detecting means comprises: The light beam is disposed at a position farther from the object than the convergence point at which the light beam is converged by the light-collecting optical system, and the second detector detects that the second light beam is converged by the light-converging optical system. The specimen than the point The first and second detection means are arranged at positions close to the body, respectively.
And three or more detectors in order to detect the light beam in the optical axis portion, the light beam outside the light beam portion, and the light beam portion in the order outside the light beam portion in the second light beam. Means for calculating a difference between an output of the detection unit located at the center of the three or more detection units and a sum of outputs of all detection units located outside the first detection unit, respectively,
And the second detecting means, and using these, the first
A first calculation unit for obtaining a focus error signal of
The difference between the sum of the outputs of the two detection units close to the center of the above detection units and the sum of the outputs of all the detection units located outside of them is obtained for the first and second detection means, respectively. A second calculation unit for obtaining a second focus error signal by using these. 7. The displacement measuring device according to claim 6, wherein each of the first and second detecting means has three detecting sections, and the first and second detecting sections each include a detecting section located at the center of the first detecting section. A detection unit, a detection unit outside the first detection unit is a second detection unit, a detection unit outside the second detection unit is a third detection unit, and a detection unit located at the center of the second detection unit is a fourth detection unit. When the detection unit, the detection unit outside the fourth detection unit is a fifth detection unit, and the detection unit outside the fifth detection unit is a sixth detection unit, the first calculation unit is a first detection unit. The difference between the output of the first detector and the sum of the outputs of all the detectors located outside the first detector of the first detector is determined, and the difference between the output of the third detector of the second detector is calculated. Output and said second
Calculating a first focus error signal by obtaining a difference from the sum of outputs of all the detection units located outside the third detection unit of the detection means, and further obtaining a difference between the two difference results; The calculation unit is configured to calculate a sum of outputs of the first detection unit and the second detection unit of the first detection unit, and a sum of outputs of all detection units located outside the second detection unit of the first detection unit. And the sum of the outputs of the third and fourth detectors of the second detector and the sum of all detectors located outside the fourth detector of the second detector. A displacement measurement apparatus for calculating a second focus error signal by calculating a difference between the two difference results. 8. An object lens arranged to face the object to be examined, an illumination optical system for irradiating the object with illumination light through the object lens, and the illumination from the object to be inspected. A condensing optical system for converging the reflected light flux of light,
Splitting means for splitting the reflected light beam into first and second light beams, first and second detecting means for detecting the first and second light beams, respectively, and the first and second light beams
Calculating means for calculating a focus error signal by calculating a detection result of the detecting means, wherein the first detecting means receives a light beam near the optical axis of the first light beam; A second detection unit for detecting a light beam outside the first detection unit, wherein the second detection unit receives a light beam near an optical axis of the second light beam And at least a fourth detection unit for detecting a light beam outside the third detection unit, wherein the first detection means includes a convergence point at which the first light beam is converged by the condensing optical system. And the second detecting means is arranged at a position closer to the test object than a convergence point at which the second light flux is converged by the light-collecting optical system. The first and second detecting means include the first and second detecting means. And second
A displacement measuring device comprising a moving means for moving the detecting means closer to or away from the convergence point. 9. An observation optical system including an objective lens, a stage for mounting a test object, and focus detection means for detecting a displacement of the test object from a focal position of the objective lens. An illumination optical system for irradiating the test object with illumination light through the objective lens; and a condensing optical system for converging a reflected light beam of the illumination light from the test object. Splitting means for splitting the reflected light beam into first and second light beams, first and second detecting means for detecting the first and second light beams, respectively,
And a calculating means for calculating a focus error signal by calculating a detection result of the second detecting means. The second detection means is disposed at a position distant from the test object, and the second detecting means is disposed at a position closer to the test object than a convergence point at which the second light flux is converged by the condensing optical system; The first and second detection means are respectively for detecting a light flux of an optical axis portion, a light flux outside the light flux portion, and a light flux of a portion further away from the optical axis in the order outside the light flux portion, of the first and second light fluxes, respectively. And three or more detection units in total, and the arithmetic unit selects one or more arbitrary detection units in order from the inside of the three or more detection units of the first detection unit, and selects And the sum of the outputs of the detectors In addition, a sum of all the detection units located outside the arbitrary detection unit is obtained, and a difference between the sums is obtained. Of the three or more detection units of the second detection unit, the sum is sequentially determined from the inside. To one or more arbitrary detectors, obtain the sum of the outputs of the selected detectors, determine the sum of all detectors located outside the arbitrary detector, and further calculate the sum of these sums. A focus detection method comprising: obtaining a difference; and further obtaining a focus error signal by further obtaining a difference between the difference result obtained for the first detection means and the difference result obtained for the second detection means. Microscope with means.