JPH10115782A - Lighting optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a light source image with a uniform light intensity distribution at the aperture of an objective lens with a large numerical aperture even when the objective is used and to light a wide field. SOLUTION: This lighting optical system which lights a sample O through a condenser lens 5 is equipped with a 1st lighting optical system includes a 1st light source LS1, a 2nd lighting optical system including a 2nd light source LS2, and a switching means M which guides illumination light from the 1st or 2nd light source to the condenser lens. Then when the sample O is lit by the 1st lighting optical system, the illumination light from the 1st light source LS1 is guided to the sample in the order of a convergence optical system 1, an optical fiber F, and a 1st relay optical system (2 to 4, and Z) forming an image of the projection end surface of the optical fiber F, and a condenser lens 5. When the sample O is lit by the 2nd lighting optical system, the illumination light from the 2nd light source LS2 is guided to the sample in the order of a 2nd relay optical system (6 and 4) forming an image of the 2nd light source and the condenser lens 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination optical system for illuminating a specimen, and is particularly suitable for use in a microscope.

[0002]

2. Description of the Related Art An example of an illumination optical system of a conventional microscope is shown in FIG.
Shown in As shown in FIG. 2, the conventional light source LS
A collector lens 6 arranged such that the front focal point is located at the position of the light source LS; a field stop FS arranged at the rear focal point of the collector lens 6; And a condenser lens 5 arranged so that the front focal point is located at the position of the aperture stop AS. With this configuration, the sample O is subjected to Koehler illumination.

[0003]

The numerical aperture (NA)
When an objective lens having a large aperture is used, a large aperture diameter of the aperture stop AS in the illumination optical system is required. In the illumination optical system of the microscope, a halogen lamp is usually used as the light source LS. In such a halogen lamp, since the size of the light source (the size of the filament) is small, it is difficult to make the light intensity distribution of the light source image formed thereon uniform when the aperture diameter of the aperture stop AS is large. is there. Here, when the light intensity distribution of the light source image at the aperture stop AS is not uniform, there is a problem that the contrast of the observed image is reduced and the resolution is reduced.

In the conventional illumination optical system shown in FIG.
In order to make the light intensity distribution of the light source image at the aperture stop AS close to uniform, a diffusion plate is provided between the collector lens 6 and the field stop FS. Cannot make the light intensity distribution of the light source image at the position of the aperture stop AS uniform. Therefore, as shown in FIG. 3, the illumination light from the light source LS is guided by the optical fiber F, and the emission end face Fb of the optical fiber F
It is conceivable that a surface light source having a uniform light intensity distribution is formed, and this surface light source is replaced with the light source LS of FIG.

As described above, when an objective lens having a large numerical aperture is used, it is necessary to form an image of the surface light source formed on the exit end face of the optical fiber over the entire aperture of the aperture stop AS in the illumination optical system. For this purpose, it is conceivable to form an image of a surface light source under a magnification B (magnification light source magnification B) by a relay optical system composed of a collector lens 6 and a condenser lens 4. The numerical aperture on the incident side of the condenser lens (the numerical aperture of the light beam incident on the condenser lens 5) is obtained by multiplying the numerical aperture of the optical fiber by the reciprocal of the light source magnification B (1 / B).

Therefore, considering that the light source image is formed by multiplying the aperture diameter of the large aperture stop AS by the enlarged light source magnification B, the illuminated field on the specimen surface becomes narrow and the field of view of the objective lens can be included. There is a problem that disappears. Therefore, the present invention provides an illumination optical system capable of forming a light source image having a uniform light intensity distribution in an aperture even when an objective lens having a large numerical aperture is used and capable of illuminating a wide illumination field. With the goal.

[0007]

In order to achieve the above-mentioned object, an illumination optical system according to the present invention comprises, for example, as shown in FIG.
An illumination optical system for illuminating a sample (O) via a condenser lens (5), wherein the first illumination optical system includes a first light source (LS1) and the second illumination optical system includes a second light source (LS2). And a switching means (M) for selectively guiding any one of the illumination light from the first light source and the illumination light from the second light source to the condenser lens.

Then, the sample (O) is provided by the first illumination optical system.
When illuminating the light source, the illumination light from the first light source (LS1) is used to form an image on the light-collecting optical system (1), the optical fiber (F), and the exit end face of the optical fiber (F).
When the sample (O) is guided to the sample in the order of the relay optical system (2 to 4, Z) and the condenser lens (5) and the sample (O) is illuminated by the second illumination optical system, the illumination light from the second light source (LS2) To the sample in the order of the second relay optical system (6, 4) for forming an image of the second light source and the condenser lens (5).

[0009] In a preferred embodiment of the present invention,
The first relay optical system re-images the primary image by the first partial optical system (2, Z) for forming a primary image of the exit end face of the optical fiber, and forms a secondary image by the first partial optical system. And a second partial optical system (3, 4) to be formed, and a field stop (FS1) is arranged in the second partial optical system. In a preferred aspect of the present invention, an on-axis ray in an optical path between the first partial optical system (2, Z) and the second partial optical system (3, 4) is parallel to the optical axis. , The first and second partial optical systems are configured, and a polarizing element (P) made of a birefringent crystal is disposed in an optical path between the first and second partial optical systems so as to be insertable and removable. It is. According to the present invention, it is preferable that the first partial optical system (2, Z) in the first relay optical system includes a zoom optical system (Z).

Further, according to the present invention, it is preferable that the switching means (M) is constituted by a mirror (M) provided in an optical path on the first light source side of the condenser lens (5) so as to be insertable and removable. In other words, this configuration is a mirror (M) provided in the optical path on the second light source side of the condenser lens (5) so as to be insertable and removable. Further, according to a preferred aspect of the present invention, the condenser lens (5) is larger than the field stop (FS) in the second partial optical system (3, 4) in the first relay optical system.
The lens group (4) on the side is configured so that light from the second light source (LS2) passes when the sample (O) is illuminated by the second illumination optical system.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view schematically showing a configuration when an illumination optical system according to the present invention is applied to an illumination optical system of a microscope. The illumination optical system shown in FIG.
This illuminates the sample O, which is an object to be illuminated, via the condenser lens 5. In the following description, an optical system arranged in the optical path from the first light source LS1 to the sample O is referred to as a first illumination optical system. The optical system arranged in the optical path from the second light source LS2 to the sample O is referred to as a second illumination optical system.
In FIG. 1, the mirror M that constitutes the switching means is located in the optical path. However, the light beam for explanation is in a state where the mirror M is located in the optical path (when the second illumination optical system is used). 2) and a state where the mirror M is located outside the optical path (a state when the first illumination optical system is used).

First, the configuration of the first illumination optical system will be described. In FIG. 1, a first light source LS1 is formed of, for example, a mercury lamp, a halogen lamp, or the like, and supplies illumination light having a predetermined wavelength. The illumination light from the first light source LS1 is condensed by the condenser lens 1 to form a light source image.
The entrance end face Fa of the optical fiber F is located near the position of the light source image by the condenser lens 1. In the present embodiment, a single fiber is used as the optical fiber F instead of a bundle fiber in order to prevent a light quantity loss.

Now, the emission end face F of the optical fiber F
From b, the illumination light repeatedly reflected inside the optical fiber F is emitted. At this time, on the exit end face Fb, a surface light source (secondary light source) having a uniform light intensity distribution is formed by repeated reflection inside. The illumination light from the surface light source formed on the exit end face Fb of the optical fiber F is conjugated to the conjugate plane AS1 (a plane conjugate with the front focal plane AS2 of the condenser lens 5 described later) by the action of the condenser lens 2 and the zoom lens Z. Then, an image of a surface light source (a tertiary light source) is formed. Here, as the zoom lens Z, for example, positive / negative /
A type having a positive refractive power arrangement, in which the second group is a variator and the third group is a compensator, can be used, but another type may be used.

Next, the illumination light from the image of the surface light source formed at the position of the conjugate plane AS1 is condensed by the action of the condenser lenses 3 and 4.
A secondary image (quaternary light source) of the surface light source is formed on the front focal plane AS2 of the condenser lens 5. Illumination light from the secondary image of the surface light source illuminates the sample O via the condenser lens 5 with Koehler illumination. An aperture stop can be arranged on at least one of the conjugate plane AS1 and the front focal plane AS2 of the condenser lens 5. The aperture diameter of the aperture stop is determined according to the (sample-side) numerical aperture of the objective lens that forms the image of the sample O to be illuminated.

In the first illumination optical system, the condenser lens 2
And the zoom lens Z constitute a first partial optical system,
The condenser lenses 3, 4 constitute a second partial optical system. Further, these first and second partial optical systems (condensing lenses 2 to 2)
4. The zoom lens Z) forms a first relay optical system. Here, the first and second partial optical systems are both-side telecentric optical systems when an on-axis light beam (hereinafter, simply referred to as an on-axis light beam) that intersects the optical axis on the specimen O is regarded as a principal light beam. In other words, on the optical fiber F side of the first partial optical system, between the first and second partial optical systems, and in the optical path on the side of the condenser lens 5 of the second partial optical system, the axial ray is parallel to the optical axis. I have.

In the second partial optical system, the focal positions of the condenser lenses 3 and 4 are made coincident, and the coincident focal positions are conjugate with the sample O. Here, a field stop FS1 is arranged. Further, in the present embodiment, the first partial optical system can be changed in magnification by the zoom lens 2 under the magnification, and the second partial optical system has a fixed magnification.

When illuminating the sample O using the second illumination optical system, a mirror M is inserted obliquely in the optical path between the condenser lens 3 and the field stop FS1. In the present embodiment, the mirror M is provided so as to be movable in a direction perpendicular to the paper surface of FIG. 1 with a constant tilt angle with respect to the optical axis. However, the configuration in which the mirror M can be inserted and removed is not limited to the above-described configuration.

Next, the configuration of the second illumination optical system will be described. In FIG. 1, the second light source LS2 is formed of, for example, a mercury lamp, a halogen lamp, or the like, and supplies illumination light having a predetermined wavelength. The illumination light from the second light source LS2 is condensed by a collector lens 6 provided so that the front focal position substantially matches the second light source LS2, and is reflected by a mirror M located in the optical path. Condensing lens 4
And reaches the front focal plane AS2 of the condenser lens 5 through. At this time, the rear focal position of the collector lens 6 matches the front focal position of the condenser lens 4, and the light source image of the second light source LS2 is formed on the front focal plane AS2 of the condenser lens 5. Here, the collector lens 6 and the condenser lens 4 constitute a second relay optical system.
The relay optical system is a two-sided telecentric optical system when an on-axis light ray is regarded as a principal ray, and has a magnification.

Therefore, on the front focal plane AS2 of the condenser lens 5, an image of the second light source LS2 is formed at an enlarged magnification. The light from the image of the second light source LS2 is condensed by the condenser lens 5 and Koehler-illuminates the sample O. In the illumination optical system for a microscope as in this embodiment, the size of the light source image at the position of the front focal plane AS2 of the condenser lens determines the size of the usable numerical aperture of the objective lens. That is, in order to use an objective lens having a large numerical aperture, the front focal plane AS2 of the condenser lens is required.
The size of the light source image at the position is increased to fill the entire aperture of the objective lens with the luminous flux. In this embodiment, at this time, the mirror M is positioned outside the optical path, and the first illumination optical system causes the exit end face Fb of the optical fiber F to be positioned at the front focal plane AS2 of the condenser lens.
Is formed. At this time, the size of the field of view is narrow, but a high-magnification objective lens having a large numerical aperture generally does not have a wide field of view, so that a problem hardly occurs.

On the other hand, when using a wide-field objective lens, the mirror M is inserted into the optical path and the sample is illuminated by the second illumination optical system. Here, the angle formed by the optical axis of the principal ray reaching the outermost edge of the field of view of the sample O on the exit end face Fb of the optical fiber F is the angle formed by the optical axis of the main ray reaching the outermost edge of the field of view of the sample O in the light source LS2. By comparison,
Due to the characteristics of the optical fiber, it becomes smaller.

Since the second illumination optical system does not use an optical fiber, the angle between the second light source LS2 and the optical axis of the principal ray reaching the outermost periphery of the field of view of the sample O can be made larger, and Can be realized. The second
When an illumination optical system is used, it is not possible to fill the entire aperture of the objective lens with a large numerical aperture with a light beam. However, in general, a low-magnification objective lens with a wide field of view has a small numerical aperture, so that a problem hardly occurs.

In the present embodiment as described above, there is an advantage that a wide illumination field can be obtained without increasing the diameter of the optical fiber F, the cost of the optical fiber F itself is reduced, and the entire apparatus is reduced. There is also an effect that the cost can be reduced. In the present embodiment, a polarizing element P made of a birefringent crystal is provided in an optical path between the first and second partial optical systems, which are double-sided telecentric optical systems, so as to be insertable and removable. As the polarizing element P, for example, a Gran Thompson prism or the like can be applied.

Between these first and second partial optical systems,
Since the on-axis ray crossing the optical axis on the specimen O is parallel to the optical axis and further on the reduction side of the second partial optical system, the second
The polarizing element P itself can be made smaller than when a polarizing element is arranged on the condenser lens 5 side of the partial optical system. Considering that the polarizing element P is disposed on the condenser lens 5 side of the second partial optical system, a crystal having a large light beam diameter and constituting the polarizing element P cannot be obtained at this position,
It cannot be actually placed.

The polarizing element P is provided with a field stop FS1.
Since it is arranged closer to the light source LS1 than the light source LS1, there is an advantage that the field of view is not doubled. Therefore, it is possible to adopt a configuration in which a polarizing plate that covers a part of the opening area of the field stop FS1 is movably arranged in the direction orthogonal to the optical axis at the position of the field stop FS1 conjugate with the sample O. If the polarizing element P is located closer to the condenser lens 5 than the field stop,
This configuration cannot be taken because the field of view is doubled.

Now, in the embodiment of the present invention as described above,
A mirror M for switching between the first and second illumination optical systems is provided so as to be insertable into and removable from the second partial optical system in the first illumination optical system, and the condenser lens 4 and the condenser lens 5 are connected to the first and second illumination optical systems. The system is configured to be shared. At this time, mirror M
Is closer to the first light source LS1 than the field stop FS1 (the second light source L
(S2 side), the field of view of the first and second illumination optical systems can be defined by one field stop FS1.

However, the arrangement of the mirror M as the switching means is not limited to the above example. For example, in FIG. 1, it may be provided between the condenser lens 4 and the position AS2, or may be provided between the condenser lens 3 and the position AS1. The switching means is not limited to the insertion / removal of the mirror M, but the second light source LS2 and the collector lens 6
The optical axis of the optical system is arranged so as to be parallel to the optical axis of the first illumination optical system. When the first illumination optical system is used, the optical axes of the condenser lens 3 and the condenser lens 4 coincide with each other. When the second illumination optical system is used, the optical axis of the collector lens 6 and the optical axis of the condenser lens 4 are made to coincide with each other.
An optical system including the second light source LS2 and the collector lens 6 and an optical system from the condenser lens 3 to the optical fiber F may be movably provided.

In the embodiment of the present invention, the optical path of the second illumination optical system is deflected by the mirror M. However, the optical path of the first illumination optical system and the mirror M may be deflected. Further, in the embodiment of the present invention, the first light source LS1 and the second light source LS2 may be shared.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, numerical examples of the illumination optical system according to the present invention will be compared with the configurations (Comparative Examples 1 and 2) described in the prior art. For comparison with the first illumination optical system of the present invention, a comparative example 2 in which a zoom lens is added to the configuration shown in FIG. 3 is used. [Numerical Example of Illumination Optical System According to the Present Invention] The size of the surface light source formed on the exit end face Fb of the optical fiber F in the first illumination optical system is φFb, and the light source magnification (position AS2 in the first illumination optical system). The lateral magnification of the formed surface light source image is B1, the numerical aperture at the exit end face of the optical fiber F is NAf, the filament size of the second light source LS2 is φL, and the light source magnification (position AS) in the second illumination optical system.
Assuming that the lateral magnification of the image of the second light source LS2 formed at 2) B2 and the numerical aperture of the light beam from the second light source LS2 is NAL, φFb = 1.0 (mm) φL = 3.2 × 4.8 (mm) B1 = 6 × 2828 × B2 = 4 × NAf = 0.2 NAL = 0.7

Here, the focal length f of the condenser lens 5
Assuming that con = 10 (mm), the sample-side numerical aperture NAobj10 =
When a 10 × objective lens having a 0.3 and a visual field of 2 (mm) on the specimen is used, a 100 × objective lens having a numerical aperture NAobj100 of 1.4 on the specimen side and a visual field of 0.2 (mm) on the specimen is used. The following shows whether or not the effect has been achieved when using.

When a 10 × objective lens is used (second illumination optical system is used) At the front focal position AS2 of the condenser lens 5,
In order to satisfy the numerical aperture NAobj10 = 0.3 of the 0 × objective lens, the size φAS of the light source image at this position AS2
2 at least φAS2 = fcon × NAobj10 × 2 = 10 × 0.3 ×
It is necessary to set 2 = 6 (mm).

Here, since the filament size φL of the second light source LS2 is 3.2 × 4.8 (mm) and the light source magnification B2 is 4 × in the second illumination optical system, the size of the light source image at the position AS2 is large. φAS2 = 13 × 19, and illumination satisfying the numerical aperture NAobj10 = 0.3 of the 10 × objective lens is performed. At this time, the size φi of the illumination field by the condenser lens 5 is: φi = (NAL / B2) × fcon × 2 = (0.7 / 4) × 10
× 2 = 3.5 (mm), which satisfies the field of view 2 (mm) of the 10 × objective lens.

When a 100 × objective lens is used (first
At the front focal position AS2 of the condenser lens 5, 1 is used.
To satisfy the numerical aperture NAobj100 = 1.4 of the 00 × objective lens, the size φA of the light source image at this position AS2
S2 is at least φAS2 = fcon × NAobj10 × 2 = 10 × 1.4 ×
2 = 28 (mm).

Here, the size of the surface light source formed on the exit end face Fb of the optical fiber F is φFb = 1.0 (mm),
Since the light source magnification B1 = 28 × in the relay optical system, the size φAS2 of the light source image at the position AS2 = 28
(mm), and the numerical aperture NAobj10 of the 100 × objective lens =
Lighting that satisfies 1.4 is provided. At this time, the size of the illumination field φi by the condenser lens 5 is as follows: φi = (NAF / B1) × fcon × 2 = (0.2 / 28) × 10
× 2 = 0.14 (mm), which does not satisfy the field of view of the 100 × objective lens of 0.2 (mm), but for a high-magnification objective lens in which resolution is more important than the field of view, practically, There is no problem.

As described above, in the numerical embodiment according to the present invention, a 10 × objective lens having a wide field of view and a high numerical aperture of 10 × are used.
Suitable illumination can be achieved up to the 0x objective lens. [Comparative Example 1 (according to the configuration in FIG. 2)] The filament size of the light source LS is φL, the light source magnification of the collector lens 6 and the condenser lens 4 (the lateral magnification of the image of the light source LS formed at the position AS) B, the light source If the numerical aperture of the light beam from the LS is NAL, then φL = 3.2 × 4.8 (mm) B = 4 × NAL = 0.7.

Here, the focal length f of the condenser lens 5
Assuming that con = 10 (mm), the sample-side numerical aperture NAobj10 =
When a 10 × objective lens having a 0.3 and a visual field of 2 (mm) on the specimen is used, a 100 × objective lens having a numerical aperture NAobj100 of 1.4 on the specimen side and a visual field of 0.2 (mm) on the specimen is used. The following shows whether or not the effect has been achieved when using.

When a 10 × Objective Lens is Used At the front focal position AS of the condenser lens 5,
In order to satisfy the numerical aperture NAobj10 = 0.3 of the double objective lens, the size φAS of the light source image at this position AS must be at least φAS = fcon × NAobj10 × 2 = 10 × 0.3 × 2
= 6 (mm).

Here, the filament size φ of the light source LS
Since L = 3.2 × 4.8 (mm) and the light source magnification B = 4 × by the collector lens 6 and the condenser lens 4, the size φAS of the light source image at the position AS = 13 × 19, and
Illumination that satisfies the numerical aperture NAobj10 = 0.3 of the double objective lens is performed. At this time, the size φi of the illumination field by the condenser lens 5 is: φi = (NAL / B) × fcon × 2 = (0.7 / 4) × 10 × 2
= 3.5 (mm), which satisfies the field of view 2 (mm) of the 10 × objective lens.

When a 100 × objective lens is used At the front focal position AS2 of the condenser lens 5, 1
To satisfy the numerical aperture NAobj100 = 1.4 of the 00 × objective lens, the size φA of the light source image at this position AS2
Let S be at least φAS = fcon × NAobj10 × 2 = 10 × 1.4 × 2
= 28 (mm).

As described above, in Comparative Example 1, φAS = 13 ×
19 (mm) and the numerical aperture NAobj1 of the 100 × objective lens
No illumination that satisfies 0 = 1.4 is not performed. As described above and in Comparative Example 1, a 10 × objective lens can be used but a 100 × objective lens cannot be used. [Comparative Example 2 (with a zoom lens added to the configuration in FIG. 3)] The size of the surface light source formed on the exit end face Fb of the optical fiber F is φFb, and the light source magnification by the relay optical systems 3 and 4 (to the position AS Lateral magnification of the formed surface light source image)
B, the numerical aperture at the exit end face of the optical fiber F is N
Assuming that Af, φFb = 1.0 (mm) B = 6 × to 28 × NAf = 0.2

Here, the focal length f of the condenser lens 5
Assuming that con = 10 (mm), the sample-side numerical aperture NAobj10 =
When a 10 × objective lens having a 0.3 and a visual field of 2 (mm) on the specimen is used, a 100 × objective lens having a numerical aperture NAobj100 of 1.4 on the specimen side and a visual field of 0.2 (mm) on the specimen is used. The following shows whether or not the effect has been achieved when using.

When a 10 × objective lens is used At the front focal position AS of the condenser lens 5,
In order to satisfy the numerical aperture NAobj10 = 0.3 of the double objective lens, the size φAS of the light source image at this position AS must be at least φAS = fcon × NAobj10 × 2 = 10 × 0.3 × 2
= 6 (mm).

Here, the filament size φ of the light source LS
L = 1.0 (mm) The size φAS of the light source image at the position AS
= 6 (mm), if the light source magnification B by the relay optical systems 3 and 4 is set to B = 6 by zooming, illumination that satisfies the numerical aperture NAobj10 of the 10 × objective lens is 0.3. At this time, the size of the illumination field φi by the condenser lens 5 is as follows: φi = (NAL / B) × fcon × 2 = (0.2 / 6) × 10 × 2
= 0.66 (mm), which does not satisfy the field of view 2 (mm) of the 10 × objective lens.

When a 100 × objective lens is used At the front focal position AS2 of the condenser lens 5, 1
To satisfy the numerical aperture NAobj100 = 1.4 of the 00 × objective lens, the size φA of the light source image at this position AS2
S2 is at least φAS2 = fcon × NAobj10 × 2 = 10 × 1.4 ×
2 = 28 (mm).

Here, the size φFb of the surface light source formed on the exit end face Fb of the optical fiber F is 1.0 (mm),
Assuming that the light source magnification B in the relay optical systems 3 and 4 is B = 28 × by zooming and the light source image size φAS = 28 (mm) at the position AS, the numerical aperture NAobj10 of the 100 × objective lens is 1.4. There is lighting to fill.

At this time, the size φi of the illumination field by the condenser lens 5 is as follows: φi = (NAL / B) × fcon × 2 = (0.2 / 28) × 10 ×
2 = 0.14 (mm), which does not satisfy the field of view of the 100 × objective lens of 0.2 (mm), but has a practical problem in the case of a high-magnification objective lens in which resolution is more important than the field of view. There is no range.

As described above and above, in Comparative Example 2, a 100 × objective lens can be used but a 10 × objective lens cannot be used.

[0047]

According to the structure of the present invention as described above, when an objective lens having a large numerical aperture is used, a light source image having a uniform light intensity distribution can be formed by an optical fiber in the first illumination optical system. Therefore, an observation image can be obtained with high contrast by utilizing the resolution of the objective lens having the large numerical aperture. Furthermore, when an objective lens having a large field of view is used, a wide illumination field can be obtained because the second illumination optical system that does not use an optical fiber is used. According to the configuration of the present invention,
Since the first and second illumination optical systems share at least the condenser lens, it is possible to simplify the configuration around the stage where the arrangement is restricted.

Further, if a zoom lens is arranged in the first illumination optical system, a light source image satisfying the numerical aperture required for the objective lens can be obtained, so that the resolution of the objective lens can be utilized. Further, if the polarizing element made of a birefringent crystal is arranged closer to the light source than the position of the field stop, there is an advantage that the field of view is not doubled. In this case, the position of the field stop covers a part of the field region. There is an advantage that a polarizing plate can be arranged. If the polarizing element is arranged closer to the light source than the second partial optical system having the magnification, the diameter of the light beam at the position of the polarizing element becomes smaller, so that the size of the polarizing element can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an embodiment of an illumination optical system according to the present invention.

FIG. 2 is a diagram illustrating an example of a conventional illumination optical system.

FIG. 3 is a diagram showing another example of a conventional illumination optical system.

[Explanation of symbols]

 LS1: First light source LS2: Second light source F: Optical fiber M: Mirror (switching means)

Claims (6)

[Claims] 1. An illumination optical system for illuminating a sample via a condenser lens, a first illumination optical system including a first light source, a second illumination optical system including a second light source, and illumination from the first light source. Switching means for selectively guiding any one of light and illumination light from the second light source to the condenser lens, when illuminating the sample with the first illumination optical system,
Guiding the illumination light from the first light source to the sample in the order of a condensing optical system, an optical fiber, a first relay optical system for forming an image of an exit end face of the optical fiber, and the condenser lens; When illuminating the sample with an optical system,
An illumination optical system configured to guide illumination light from the second light source to the sample in the order of a second relay optical system that forms an image of the second light source and the condenser lens. 2. The first relay optical system re-images a first partial optical system for forming a primary image of the exit end face of the optical fiber, and a primary image formed by the first partial optical system. The illumination optical system according to claim 1, further comprising: a second partial optical system that forms a secondary image, wherein a field stop is disposed in the second partial optical system. 3. The first and second partial optical systems are configured such that an axial ray in an optical path between the first partial optical system and the second partial optical system is parallel to an optical axis. 3. The illumination optical system according to claim 2, wherein a polarizing element made of a birefringent crystal is arranged in an optical path between the first and second partial optical systems so as to be insertable and removable. 4. The optical system according to claim 2, wherein the first partial optical system in the first relay optical system includes a zoom optical system.
Or the illumination optical system according to 3. 5. An illumination according to claim 1, wherein said switching means comprises a mirror provided in an optical path of said condenser lens on a side of said first light source so as to be insertable and removable. Optical system. 6. A lens group closer to the condenser lens than the field stop in the second partial optical system in the first relay optical system, the second illumination optical system illuminates the sample with the second partial optical system. The illumination optical system according to any one of claims 2 to 5, wherein light from a light source is configured to pass therethrough.