JP3746703B2 - Focus detection device and optical microscope or optical inspection device provided with the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a focus detection device used in an optical device that observes, measures, or inspects an object via an optical system, and an optical microscope or an optical inspection device including the focus detection device.
[0002]
[Prior art]
As an optical device that observes, measures, or inspects an object via an optical system, for example, there is an optical microscope. In such an apparatus, a person who observes, measures or inspects (observer) adjusts the distance between the objective lens and the object for focusing so that the image of the object can be clearly observed. There is a need. In many cases, this interval adjustment is performed by moving the stage up and down.
At that time, when the magnification of the objective lens is high, the depth of focus is shallow, so that the in-focus position cannot be found if the stage is moved greatly. In this case, the observer has to move the stage little by little, and it takes time to find the in-focus position.
On the other hand, when the magnification of the objective lens is low, the depth of focus is deep, so that the sharpness of the image does not change much even if the stage is moved a little larger. In this case, it may be difficult for the observer to find the stage position in focus.
[0003]
In order to solve such problems, in recent years, focus detection devices have been combined with these optical devices.
There are various types of focus detection devices, and one of them is an active focus detection device. In this method, light is irradiated toward an object, reflected light reflected from the object is detected by a photodetector, and it is determined whether the light is in focus or in focus depending on the state of the reflected light.
[0004]
FIG. 7A shows a basic configuration example of an active focus detection apparatus. In FIG. 7, 2 is a light source, 3 is a collimating lens, 4 is a light shielding plate, 58 is a polarizing beam splitter, 6 is a quarter wavelength plate, 7 is a dichroic mirror, 1 is an objective lens, and S is a specimen that is an object. 8 is an imaging lens, and 9 is a photodetector.
[0005]
The light source 2 is a semiconductor laser and emits laser light in the infrared wavelength region. The polarization state of the laser light is linearly polarized light. The laser light emitted from the light source 2 becomes a parallel light beam through the collimator lens 3 and enters the polarization beam splitter 8. At that time, half of the light beam is shielded by the light shielding plate 4 disposed between the collimating lens 3 and the polarization beam splitter 8. The polarization beam splitter 5 has a characteristic of reflecting P-polarized linearly polarized light and transmitting S-polarized linearly polarized light. Therefore, if the semiconductor laser is arranged in advance so that the polarization direction of the emitted laser light coincides with the P-polarization direction, all of the laser light incident on the polarization beam splitter 5 is reflected by the reflection surface of the polarization beam splitter 5. Therefore, no loss of light intensity (light quantity) occurs.
[0006]
The laser beam reflected by the reflecting surface of the polarization beam splitter 5 enters the quarter wavelength plate 6. The quarter-wave plate 6 is arranged so that the incident linearly polarized light is emitted as circularly polarized light, and the laser light emitted from the quarter-wave plate 6 becomes circularly polarized light and is reflected by the dichroic mirror 7 to be objective. The light enters the lens 1. The objective lens 1 condenses the incident laser light on the sample S.
[0007]
The laser light reflected by the sample S passes through the objective lens 1 again, but does not return the same optical path as when it was incident at this time, but returns to the opposite optical path across the optical axis. Then, it is reflected by the dichroic mirror 7 and enters the quarter-wave plate 6. Here, the circularly polarized laser light is emitted as linearly polarized light, but this time, the direction of linearly polarized light is the S-polarized light direction, so that all of the laser light incident on the polarizing beam splitter 5 is transmitted through the polarizing beam splitter 5. Then, the light enters the imaging lens 8. The imaging lens 8 condenses the incident laser light. The light detector 4 is disposed at the condensing position and generates an electrical signal corresponding to the light intensity of the laser light. The photodetector 9 has a structure in which two independent light receiving portions A and B are arranged close to each other, and is configured using, for example, a two-divided photodiode.
[0008]
In the focus detection apparatus having the configuration shown in FIG. 7, the laser beam condensed on the sample S via the objective lens 1 has a substantially circular shape and a very small area (hereinafter referred to as a spot). Light). The number of spot lights is one. Therefore, the configuration shown in FIG. 7 is referred to as a single spot projection method.
[0009]
How to determine (detect) the in-focus state or the out-of-focus state in the single spot projection method will be described with reference to FIG. 8A, 8B and 8C are views seen from the direction of the arrow in the upper view. Further, the diagram on the right side is a diagram showing the state of the light beam condensed on the photodetector 9.
The photodetector 9 includes two light receiving portions A and B having the same shape. There is a slight gap (simply shown here as a solid line) between the light receiving part A and the light receiving part B, and the boundary formed by this gap intersects the optical axis.
[0010]
In the focused state, the reflected light from the sample S is collected on the optical axis of the photodetector 9, so that the spot light formed on the photodetector 9 is optical axis as shown in FIG. 8B. The light intensity distribution is symmetrical to the left and right. That is, since half of the spot light is formed in the light receiving part A and the other half is formed in the light receiving part B, the area (light intensity) of the spot light formed in the light receiving part A and the light receiving part B is Will be equal. Therefore, in the in-focus state, the electric signals generated from the two light receiving parts A and B are also equal.
[0011]
Next, there are two out-of-focus states: a state where the sample S is located farther from the objective lens 1 than the focal position, and a state where the sample S is located closer to the objective lens 1 than the focal position. In the present application, the former case is referred to as a rear pin state, and the latter case is referred to as a front pin state.
In the rear pin state, as shown in FIG. 8A, the laser light reflected from the specimen is condensed before the photodetector 9, so that the photodetector 9 is compared with FIG. 8B. Thus, a light beam with a large diameter is formed. Moreover, the light beams formed in the two light receiving portions A and B are not symmetrical, and a large light beam is formed in one light receiving portion, here the light receiving portion B. Therefore, in the rear pin state, the electrical signal generated in the light receiving unit A is smaller than the electrical signal generated in the light receiving unit B.
On the other hand, in the front pin state, as shown in FIG. 8C, a large light beam is formed in the light receiving part A, so that the electrical signal generated in the light receiving part A is larger than the electrical signal generated in the light receiving part B. Become.
[0012]
In this way, the magnitude relationship between the electrical signals generated in the light receiving part A and the light receiving part B changes depending on the difference in the distance between the objective lens 1 and the sample S, and thus a signal (hereinafter referred to as a focus error signal) that takes the difference. Whether the in-focus state or the out-of-focus state can be determined based on the value of, and further, it can be determined whether the front pin state or the rear pin state.
[0013]
FIG. 9 is a graph showing the relationship between the signal intensity from the light receiving unit A and the light receiving unit B and the defocus amount in the single spot light projection type focus detection apparatus having the configuration shown in FIG. FIG. 10 is a graph showing a focus error signal obtained by taking the difference between the signal intensity from the light receiving part A and the signal intensity from the light receiving part B. FIG. 11 further shows a normalized focus error by dividing the difference between the signal intensity from the light receiving part A and the signal intensity from the light receiving part B by the sum of the signal intensity from the light receiving part A and the signal intensity from the light receiving part B. It is a graph which shows a signal. If normalization as shown in FIG. 11 is performed, the focus error signal pattern does not change much even when the sample reflectance is low and the signal intensity of the light receiving unit is weak, so that a more accurate in-focus state or in-focus state Judgment can be made.
[0014]
If such a focus detection device is combined with an optical device such as a microscope and a moving means for moving the stage up and down so that the focus error signal becomes zero or moving the objective lens up and down automatically, Can focus on the specimen. In the present application, the above-mentioned means for automatically focusing is referred to as automatic focusing means.
[0015]
By the way, the focus detection apparatus of the single spot projection method as described above has a problem that the focus detection becomes unstable and the accuracy deteriorates when it is used for a sample having many uneven steps. As a solution for such a problem, the present applicant has proposed a multi-spot projection method as shown in Japanese Patent Application No. 2000-112388. FIG. 12A shows a basic configuration example of a multi-spot projection type focus detection apparatus. In a multi-spot projection type focus detection apparatus, a plurality of light beams are emitted from a light source unit. In the example of FIG. 12A, the light source unit is configured by combining the light source 2 and the diffraction grating 10 as means for generating a plurality of light beams.
[0016]
A plurality of light fluxes from the light source section follow the same optical path as the above-described single spot type focus detection device, pass through the objective lens 1, and as shown in FIG. It becomes light. Thereafter, the plurality of light beams are reflected by the sample surface S, pass through the objective lens 1 again, and follow the same optical path as that of the single spot type focus detection device described above, and form an image on the photodetector 9 of the focus detection device. Is done. On the photodetector 9, as shown in FIG. 12C, spot lights are imaged in a line in a slight gap between the light receiving part A and the light receiving part B. As such, the diffraction grating 10 and the photodetector 9 are arranged with their positions adjusted.
As means for generating a plurality of light beams, a plurality of single light sources may be arranged in a line or an acousto-optic element may be used instead of the diffraction grating.
[0017]
As described above, it is desirable to use a single-spot projection type or multi-spot projection type focus detection device in accordance with each application. It is desirable to use a single spot projection type focus detection device when you want to detect the focus accurately with a sample with few irregularities, and with a multi-spot projection type focus when you want to perform stable focus detection with a sample with many irregularities. It is desirable to use a detection device.
[0018]
[Problems to be solved by the invention]
However, in both the single-spot projection method and the multi-spot projection method, when the specimen S is extremely defocused, the light beam is finally received as shown in FIGS. 13 (a) and 13 (e). The part will stick out.
In this case, as is apparent from the graph shown in FIG. 9, the signal intensity obtained from the light receiving part A and the light receiving part B is considerably reduced.
[0019]
If the signal intensity obtained from the light receiving portions A and B is considerably reduced, the electric noise of the electric circuit, light leakage or stray light is buried in the noise that hits the light receiving portion, and a normal focus error signal cannot be obtained. That is, it becomes impossible to determine the front pin state and the rear pin state.
As shown in FIGS. 10 and 11, when defocusing is performed in the plus direction or the minus direction, the focus error signal is finally buried in the noise.
[0020]
For this reason, there is a limit to the amount of defocus that can be detected. This is called an AF capture range.
For example, when a high-magnification objective lens having a magnification of 100 to 250 is used, it is immediately shown in FIGS. 13A and 13E due to the high signal magnification in addition to the low original signal intensity. Since such a light beam protrudes from the light receiving portion, the AF capture range is considerably narrowed.
[0021]
As a method for widening the AF capture range, it is conceivable to lower the imaging magnification of the optical system of the focus detection device. However, with this method, for example, when a low-power objective lens having a magnification of 4 to 10 is used, the focus error signal near the focus becomes too insensitive (that is, the inclination of the focus error signal near the focus is gentle). This is not preferable because the accuracy of focus detection deteriorates.
[0022]
For this reason, the imaging magnification of the focus detection device is determined so as to balance the magnification of the objective lens to be used, the accuracy of focus detection, and the AF capture range. However, the conventional focus detection device tends to narrow the AF capture range of the high-magnification objective lens.
[0023]
In the multi-spot projection method, the effective range of multi-spot light on the sample surface is determined by the imaging magnification of the optical system used in the focus detection device and the size of the photodetector.
For this reason, it is desirable to perform stable focus detection by making the effective range of multi-spot light as wide as possible for a sample with many irregularities.
[0024]
Therefore, in the conventional multi-spot projection method, a photodetector having a larger light receiving area than that of the single spot projection method is used. This can be clearly seen by comparing the photodetector in the single-spot projection method of FIG. 7C with the photodetector in the multi-spot projection method of FIG. However, a photodetector with a large area is expensive and has a low response speed, and further, there is a problem in that the metal frame where the photodetector is placed is enlarged and the entire apparatus is enlarged. .
[0025]
Further, although a solution means of lowering the imaging magnification of the focus detection device is conceivable, as described above, there is a problem that the accuracy of focus detection with a low magnification objective lens of 4 to 10 times deteriorates. It is not preferable.
[0026]
The present invention has been made in view of the above problems, and is a focus detection device that is suitable for objective lenses from low magnification to high magnification and that can widen the AF capture range of the high magnification objective lens, and the focus detection device An object of the present invention is to provide an optical microscope or an optical inspection apparatus including
The present invention also includes a focus detection device capable of preventing an increase in the size of the photodetector while ensuring an effective multi-spot projection range on the sample surface in the multi-spot projection method, and the same. An object is to provide an optical microscope or an optical inspection apparatus.
[0027]
[Means for Solving the Problems]
In order to achieve the above object, a focus detection apparatus according to the first aspect of the present invention includes a light source section, a light blocking member that blocks a part of the light beam from the light source section, and a light split having a surface that reflects or transmits the incident light beam. Light detection comprising a member, a condensing optical system for condensing an incident light beam, and at least one boundary line in a plane orthogonal to the optical axis, and a plurality of light receiving portions provided across the boundary line The light source unit and the light shielding member are arranged in a first optical path divided through the light dividing member, and the light collecting optical system and the photodetector are arranged through the light dividing member. The focus detection device is arranged in the second optical path divided in such a manner that the photodetector is arranged at the condensing position of the condensing optical system, and the condensing optical system has a focal point in the boundary line direction. The distance is different from the focal length in the direction perpendicular to the boundary line, One, the imaging position of the boundary direction, characterized in that the imaging position in a direction perpendicular to the boundary line is configured to conform substantially.
[0028]
The focus detection apparatus according to the second invention is characterized in that, in the first invention, the condensing optical system has at least two toric surfaces.
[0029]
An optical microscope or a focus detection device provided with the focus detection device according to the third invention is a focus detection device according to the first or second invention, or a multi-light generating member from which the light source emits a plurality of light beams. And a focus detection device according to the first or second aspect of the present invention, and automatic focusing means for performing automatic focusing based on a focus error signal output from the photodetector.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Prior to the description of the embodiments, the operation of the present invention will be described.
First, the operation of the first invention will be described.
In the focus detection apparatus according to the first aspect of the invention, the configuration and operational effects of the condensing optical system are different from those of the conventional focus detection apparatus shown in FIG. Other basic configurations and operations are substantially the same as those in FIG.
[0031]
A conventional condensing optical system is shown as an imaging lens 8 in FIG. The refracting surfaces (the light incident surface and the light exiting surface) of the imaging lens are both spherical surfaces that are rotationally symmetric with respect to an axis (center axis) passing through the center of the lens. As shown in FIG. 14, the condensing optical system may be composed of one positive lens or may be composed of a positive lens group in which a plurality of lenses are combined. In such a case, as the spot on the photodetector is defocused on the specimen surface, FIG. 13 (c) → (b) → (a) or FIG. 13 (c) → (d) → ( As shown to e), it spreads in a substantially semicircle shape.
[0032]
On the other hand, in the first invention, as shown in FIG. 1, the condensing optical system is different from the focal length in the plane E and the focal length in the plane F, and the imaging position and the plane in the plane E are different. The image forming position of F is configured to substantially coincide. That is, in the first invention, when the condensing optical system is regarded as one lens, the refracting surface is a surface having a rotationally asymmetric shape with respect to the central axis of the lens.
In addition, the focal distance in the plane E is a focal distance in the boundary line XY direction of two light-receiving parts. On the other hand, the focal length in the plane F is a focal length in a direction perpendicular to the boundary line XY direction. The imaging position on the plane E is an imaging position in the boundary line XY direction. On the other hand, the imaging position on the plane F is an imaging position in a direction perpendicular to the boundary line XY direction.
The focal lengths in the plane E and the plane F are different from each other, that is, the imaging magnifications in the plane E and the plane F are different. In the following description, a configuration in which the focal length on the plane E is reduced (that is, the imaging magnification is reduced) and the focal length on the plane F is increased (that is, the imaging magnification is increased) will be described. And
[0033]
With this configuration, when the sample surface is defocused, the spot on the photodetector is changed from FIG. 2 (c) → (b) → (a) or FIG. 2 (c) → (d) → As shown in (e), it spreads in a substantially elliptical shape in a direction orthogonal to the boundary line XY. When this state is compared with the conventional example (FIG. 13), the spot is not so long in the first invention in the direction orthogonal to the boundary line XY between the light receiving part A and the light receiving part B.
For this reason, according to the first aspect of the invention, the signal intensity from the light receiving part A and the light receiving part B does not decrease much as compared with the conventional example even when defocused. Comparing the first invention (FIG. 3) and the conventional example (FIG. 9), the signal intensity IX of the first invention is the conventional signal intensity at the same defocus position (defocus amount) X. Is larger than the signal intensity I′X.
Therefore, according to the first invention, the focus error signal is not buried in noise as compared with the conventional example.
[0034]
In the first invention, the spread of the spot in the direction of the boundary line XY is smaller than that of the conventional example. Therefore, the defocus amount when the spot protrudes from the light receiving unit becomes larger than that in the conventional example. In the first invention (FIG. 4) and the conventional example (FIG. 10), when the width when the signal intensity reaches a peak is compared, the width L in the first invention is compared with the width L ′ in the conventional example. Is getting bigger. In the range indicated by the width L and the width L ′, the defocus amount and the focus error signal correspond to each other on a one-to-one basis. Therefore, the first invention can have a wider range in which the autofocus is activated than the conventional example.
[0035]
Further, when the normalized focus error signal is compared between the first invention (FIG. 5) and the conventional example (FIG. 11), there are the following differences. In the first invention, the focus error signals in the range from the center to the left are all positive values, and the focus error signals in the range from the center to the right are all negative values. In this case, the following can be performed in the first invention. For example, the range from the center to the left is in a state where the distance between the stage and the object is separated, and the range from the center to the right is in a state where the distance between the stage and the object is close. Then, if the defocus signal is positive, it can be seen that the focus position is in a direction in which the distance between the stage and the object is approached. That is, the amount of movement of the stage (or objective lens) to the focus position is unknown, but the direction of moving the stage is known. On the other hand, in the conventional example, the signal in the range from the center to the right is almost a negative value, but is partially a positive value. Similarly, the signal in the range from the center to the left is almost a positive value, but partly a negative value. Therefore, in the conventional example, the direction in which the stage is moved can be determined only within the range indicated by D. As described above, when the range in which the movement amount is unknown but the direction in which the movement direction is known (referred to as AF supplementary range) is compared, the AF supplementary range that is wider in the first invention can be obtained.
[0036]
Next, the operation of the second invention will be described.
In the second invention, the condensing optical system in the first invention is configured to have at least two toric surfaces as shown in FIG.
If comprised in this way, the focal distance in the plane E and the plane F can be made into a respectively different value, and it becomes possible to make the image formation position of the plane E and the plane F substantially correspond.
When the condensing optical system is configured with one toric surface, the focal lengths on the plane E and the plane F can be set to different values, but the imaging positions of the plane E and the plane F are matched. I can't do that. This is because astigmatism cannot be removed with one toric surface.
[0037]
In the second invention, at least one of the toric surfaces used in the condensing optical system is a surface having a positive power, and at least one surface is a surface having a negative power. If more toric surfaces are used than two surfaces, a condensing optical system from which aberrations are removed is obtained, and precise focus detection is possible.
Further, if a cylindrical surface is used as a toric surface used in the condensing optical system, the configuration is simple, so that it can be manufactured at low cost.
[0038]
The focus detection apparatus of the present invention using the above-described condensing optical system is configured such that, in the first or second invention, the light source unit includes a multi-beam generating member that emits a plurality of light beams. It is also applicable to.
[0039]
If the light source unit is configured to emit a plurality of light beams, multi-spot projection can be performed. The configuration and operation of the multi-spot projection method in the present invention are substantially the same as those in FIG.
If the configuration of the first or second aspect of the invention is used for the multi-spot projection configuration as in the third aspect of the invention, the spread of the light flux in the boundary line XY direction on the photodetector can be suppressed. Therefore, as shown in FIG. 6, the interval on the photodetector can be reduced. This eliminates the use of a large photodetector as used in the conventional focus detection apparatus shown in FIG.
[0040]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a conceptual diagram of a condensing optical system used in a focus detection apparatus according to an embodiment of the present invention. The other configuration of the focus detection apparatus is substantially the same as the configuration shown in FIG.
The condensing optical system 8 ′ of the present embodiment includes, in order from the side opposite to the photodetector, a positive lens 11 having a convex toric surface 11a, a negative lens 12 having a concave toric surface 12a, and a spherical surface. And a positive lens 13 having a shape. The image formation position on the E plane of the condensing optical system and the image formation position on the F plane substantially coincide. Further, the focal length in the E plane is smaller than the focal length in the F plane, and therefore the imaging magnification in the E plane is smaller than the imaging magnification in the F plane.
[0041]
The light beam reflected and returned from the sample enters the condensing optical system 8 ′ as a semicircular light beam. Then, by passing through the condensing optical system 8 ′, the light beam becomes a semi-elliptical light beam that is long on the E plane and short on the F plane. The semi-elliptical light beam forms an image on the photodetector 9 and becomes a minute spot light.
At this time, according to the condensing optical system 8 ′ of the present embodiment, since the imaging magnification in the E plane is smaller than the imaging magnification in the F plane, when the specimen is defocused, as shown in FIG. Even if the spot on the photodetector 9 becomes longer in the direction orthogonal to the boundary line XY between the light receiving part A and the light receiving part B, it does not become so long in the boundary line XY direction and spreads in a semi-elliptical shape. To go.
For this reason, according to the focus detection apparatus of the present embodiment, it is possible to widen the AF capture range of the high-magnification objective lens.
[0042]
As described above, the focus detection apparatus according to the present invention and the optical microscope or optical inspection apparatus including the focus detection apparatus have the following features in addition to the invention described in the claims.
[0043]
(1) The focus detection apparatus according to claim 1, wherein the condensing optical system has at least one positive toric surface and at least one negative toric surface.
[0044]
(2) The condensing optical system includes at least one positive cylindrical lens, at least one negative cylindrical lens, and at least one spherical positive lens. The focus detection apparatus described.
[0045]
(3) The focus detection apparatus according to claim 1 or 2, wherein the light source unit includes a multi-beam generation member that emits a plurality of beams.
[0046]
【The invention's effect】
As described above, according to the focus detection device of the present invention and the optical microscope or optical inspection device using the same, it can be adapted to a low-magnification to high-magnification objective lens and can widen the AF capture range with the high-magnification objective lens. .
Further, in the multi-spot projection method, it is possible to prevent an increase in the size of the photodetector while ensuring an effective multi-spot projection range on the specimen surface.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a condensing optical system according to a first example of a focus detection apparatus according to the present invention.
FIG. 2 is an explanatory diagram showing a state of a light beam on a photodetector at the time of defocusing using the condensing optical system of the present invention.
FIG. 3 is a graph showing an example of the relationship between the signal intensity from the light receiving unit A and the light receiving unit B and the defocus amount when the configuration of the present invention is used.
FIG. 4 is a graph showing an example of a relationship between a focus error signal (BA) and a defocus amount when the configuration of the present invention is used.
FIG. 5 is a graph showing an example of a relationship between a normalized focus error signal (BA) / (B + A) and a defocus amount when the configuration of the present invention is used.
FIG. 6 is an explanatory diagram of the state of a photodetector during multi-spot projection using the condensing optical system of the present invention.
7A and 7B are schematic diagrams of an active focus detection apparatus using a single spot projection method, in which FIG. 7A is a schematic configuration diagram, FIG. 7B is a diagram of the objective lens in FIG. FIG. 5A is a view of the light receiving unit in (a) as viewed in the direction of arrow V.
FIGS. 8A and 8B are explanatory views showing the state of a spot on a photodetector of a focus detection apparatus using a single spot light projection method, in which FIG. 8A is a state at a rear pin position, and FIG. 8B is a focus position; The state, (c) shows the state at the front pin position.
FIG. 9 is a graph showing an example of the relationship between the signal intensity from the light receiving unit A and the light receiving unit B and the defocus amount when the conventional configuration is used.
FIG. 10 is a graph illustrating an example of a relationship between a focus error signal (BA) and a defocus amount when a conventional configuration is used.
FIG. 11 is a graph showing an example of a relationship between a normalized focus error signal (BA) / (B + A) and a defocus amount when a conventional configuration is used.
12A and 12B are schematic views of an active focus detection apparatus using a multi-spot projection method, where FIG. 12A is a schematic configuration diagram, FIG. 12B is a view of the objective lens in FIG. FIG. 5A is a view of the light receiving unit in (a) as viewed in the direction of arrow V.
FIG. 13 is an explanatory diagram showing a state of a light beam on a photodetector at the time of defocus using a conventional condensing optical system.
FIG. 14 is a schematic configuration diagram of a condensing optical system used in a conventional focus detection apparatus.
FIG. 15 is an explanatory diagram of a state of a photodetector at the time of multi-spot projection using a conventional condensing optical system.
[Explanation of symbols]
1 Objective lens
2 Light source
3 Collimating lens
4 Shading plate
5 Polarizing beam splitter
6 1/4 wave plate
7 Dichroic mirror
8 Condensing optical system (imaging lens)
8 'Condensing optical system
9 Photodetector
10 Diffraction grating
11 Positive lens
11a Convex toric surface
12 Negative lens
12a Concave toric surface
13 Positive lens

Claims (3)

A light source unit;
A light shielding member for shielding a part of the light flux from the light source unit;
A light splitting member having a surface for reflecting or transmitting an incident light beam;
A condensing optical system that condenses the incident light beam;
A detector having at least one boundary line in a plane orthogonal to the optical axis, and having a plurality of light receiving portions provided across the boundary line;
The light source unit and the light shielding member are arranged in a first optical path divided through the light dividing member,
The condensing optical system and the photodetector are arranged in a second optical path divided through the light dividing member,
The light detector is a focus detection device arranged at a condensing position of the condensing optical system,
In the condensing optical system, a focal length in the boundary line direction is different from a focal length in a direction perpendicular to the boundary line, and an imaging position in the boundary line direction is perpendicular to the boundary line. A focus detection apparatus configured to substantially coincide with an imaging position in a direction. The focus detection apparatus according to claim 1, wherein the condensing optical system has at least two toric surfaces. The focus detection apparatus according to claim 1 or 2, or the focus detection apparatus according to claim 1 or 2, wherein the light source unit includes a multi-light generation member that emits a plurality of light beams. An optical microscope or an optical inspection apparatus provided with an automatic focusing means for performing automatic focusing based on a focus error signal output from the instrument.

Images