JPS60220307A - Polarizing microscope - Google Patents

Abstract

PURPOSE:To prevent degradation of an extinction factor E.F. by arranging a cross-shaped aperture stop in the pupil of an object lens or a position conjugate to it and permitting only rays, where the polarization direction is not rotated, to pass through efficiently but intercepting rays where the polarization direction will be rotated or is rotated. CONSTITUTION:When an exit pupil 23 of an object lens 16 is observed through an analyzer 19, a dark cross line 22 is observed. A harmful light which reduces the E.F. is the luminous flux which passes through a light part which is seen in the exit pupil 23 when it is observed through the analyzer 19, and the luminous flux which passes through the part of the dark cross line 22 is intercepted by the analyzer 19 and does not reduce the E.F. A cross-shaped aperture stop 13 is arranged in the conjugate position in the front of a condenser lens 14. The aperture stop 13 can be rotated around the optical axis in accordance with rotation of a polarizer 12 and the analyzer 19 so that the dark cross line 22 and the aperture of the cross-shaped aperture stop 13 coincide with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a highly sensitive polarizing microscope with large extinction coefficients (hereinafter abbreviated as E and F).

Ideally, E and F of the conventional polarizing microscope should be infinite, but in reality they are finite. Therefore, there is a limit to the observation of specimens that have only weak birefringence, and this has been a major problem for a long time. The main reason why E and F are small is that the direction of polarization is rotated and shuffled due to boundary birefringence that occurs on the surfaces of the illumination optical system and objective lens located between the polarizer and analyzer. there were. Especially when using a high magnification objective lens, E, F,
There is a strong tendency to decrease.

A rectifier optical system (optical rectifier) is known as an optical system that solves this problem. This optical system, as shown in FIG. 7, is constructed by incorporating a rectifier optical element into an ordinary polarizing microscope. That is, l is a field stop, 2 is a polarizer, 3 is a first rectifier optical element, 4 is a condenser lens, 5 is a slide glass, 6 is an objective lens, 7 is a second rectifier optical element, 8 is a compensator, 9 is an analyzer, 10 is an eyepiece lens, and the first rectifier optical element 3 has the function of rotating the polarization direction of incident polarized light by the same amount in the opposite direction to the rotation of the polarization direction caused by the condenser lens 4. It is a zero power (no refractive index) optical element. Therefore, the polarization direction of the light beam incident on the first rectifier optical element 3 is rotated by the optical element 3, and the polarization direction is rotated in the opposite direction by the condenser lens 4, so that the light beam has almost the same polarization plane as that at the time of incidence. It becomes polarized light and exits the condenser lens 4. The second rectifier optical element 7 is a zero-power optical element that rotates the plane of polarization by the same amount in the opposite direction to the rotation of the plane of polarization caused by the objective lens 6, and rotates the plane of polarization rotated by the objective lens 6. It works to restore it. in this way,
In the rectifier optical system, countermeasures are taken against the main cause of reducing i by using two rectifier optical elements, but the basic configuration of the rectifier optical element is one concave lens and one convex lens. /2 wavelength plate, it is complicated and expensive. However, since a different rectifier optical element is required for each condenser lens or each objective lens, there is a problem that the entire optical system becomes more expensive.

Purpose In view of the above-mentioned problems, the present invention aims to provide a highly sensitive polarizing microscope in which E and F can be increased simply by using simple and inexpensive optical elements.

Overview The polarizing microscope according to the present invention uses a surface that includes the optical axis of each lens surface and extends in the vibration direction of the polarizer or in a direction perpendicular thereto as an incident surface (a surface that includes the normal to the lens surface and the traveling direction of the light ray). Taking advantage of the fact that the light ray or the light rays near it undergoes no rotation of the polarization direction on the lens surface, a cross-shaped aperture stop is placed at the pupil of the objective lens or at a position conjugate to it, so that the light ray does not undergo rotation of the polarization direction. This system is designed to efficiently pass only the light beams and block the light rays whose polarization direction is rotated or whose polarization direction has been rotated, thereby preventing deterioration of E and F.

EXAMPLE Below, the present invention will be explained in detail based on an example shown in FIGS. 1 and 2. FIG. 1 shows the entire optical system of a transmission type polarizing microscope according to the present invention, excluding the light source section. ing. 1
Reference numeral 1 denotes a field stop arranged at a position conjugate with the specimen surface on the slide glass 15, and determines the illumination range of the specimen. Reference numeral 12 is a polarizer whose vibration direction is orthogonal to that of the analyzer 19, and has the function of converting illumination light into linearly polarized light. Reference numeral 13 is located at a position conjugate with the entrance pupil of the objective lens 16 with respect to the condenser lens 14;
It is a cross-shaped aperture stop having an opening as shown in the figure, and its axis of symmetry AA' coincides with the vibration direction of the polarizer 12. Although not shown, the field stop 1
1 has a light source and a collector lens that focuses the light beam emitted by the light source, and the illumination light beam focused by the collector lens fills the field diaphragm 11 and then passes through the aperture diaphragm 1.
A light source image is formed at the aperture 3. 17 is a pupil of the objective lens 16, 18 is a compensator, 20 is an eyepiece, and 21 is a field stop of the eyepiece 20.

The optical system of the polarizing microscope according to the present invention is configured as described above, but if a circular aperture stop is placed in place of the cross-shaped aperture stop 13, the configuration can be exactly the same as that of a normal transmission type polarizing microscope using Koehler illumination. The functions of each part except the cross-shaped aperture diaphragm 13 are exactly the same as those of a normal transmission type polarizing microscope, so we will omit a detailed explanation of these functions and refer to E.
The principle of increasing F will be explained.

First, in order to explain why the E and F of conventional polarizing microscopes are so small, we placed a circular aperture diaphragm (brightness diaphragm) used in ordinary polarizing microscopes in place of the cross-shaped aperture diaphragm 130. Think about the case. In this case, the linearly polarized light exiting the polarizer 12 is transferred to the condenser lens 14.
．． While passing through the objective lens 16 and reaching the analyzer 19, the polarization direction of some of the light beams is rotated. The light beam whose polarization direction has been rotated is not perpendicular to the vibration direction of the analyzer 19, so the analyzer 19
9 and makes E and F smaller.

This tendency becomes particularly strong when a high-magnification objective lens is used. Rotation and rotation of the polarization direction mainly occurs on each surface of the condenser lens 14 and the objective lens 16. The plane of incidence of the meridional rays that enter each point on the lens surface is a plane that includes the optical axis and its point of incidence, and if this plane and the polarization direction are not perpendicular or parallel, the polarization component can be separated into the P component and the S component. Since there is a difference in the reflectance of each component on the lens surface, there is also a difference in transmittance, and as a result, the two components are combined and the total polarized light component is rotated. That is, as shown in FIG. 3, meridional rays that are incident on the cross area of the lens surface that extend from the point of intersection with the optical axis of each lens surface in the vibration direction of the polarizer 12 or in a direction perpendicular to the vibration direction of the polarizer 12 are However, for light rays incident on other regions, rotation of the polarization direction occurs on the lens surface. or,
Regarding the spherical ray, the rotation of the plane of polarization is the smallest when it is incident near the cross area, and the rotation of the plane of polarization is large when it is incident on other areas. Therefore, when the exit pupil of the objective lens 16 is observed through the analyzer 19,
Dark crosshair (isogyer) 22 as shown in Figure 4
has been observed and this is known. However, in FIGS. 3 and 4, 23 is the exit pupil of the objective lens 16, and 24 is the exit pupil of the objective lens 16.
is the vibration direction of the polarizer 12, and 25 is the vibration direction of the polarized light within the exit pupil 23.

Incidentally, the position of the dark cross line 22 does not necessarily coincide with the exit pupil plane of the objective lens 16, but may be located at a position conjugate with each lens surface of the condenser lens 14 and the objective lens 16 with respect to the subsequent lenses of the objective lens 16. Dark crosshair images are formed by the rotation of the polarization direction caused by each plane. Therefore, when observing the exit pupil plane of the objective lens 16,
You are looking at a superimposed image of them. However, many of the above conjugate positions where individual dark crosses are formed are
Located near the exit pupil plane of the objective lens 16, especially E and F:
In the case of a high-magnification objective lens that is small and easy to move, the conjugate position is often located closer to the exit pupil plane. This is because when a high-magnification objective lens is divided into a front group and a rear group based on the pupil position within the lens, the front group power of the high-magnification objective lens is generally large, so the conjugate position in the object space before that is the front group. The rear focal point of the group is located near the pupil position of the objective lens, and the distance between the rear group and the front group is generally not very wide, and the rear group lens is located near the rear focal point of the front group. It is located. Therefore, the conjugate position where the dark cross line is formed is often near the exit pupil of any objective lens with high magnification.

Furthermore, in the case of a high magnification objective lens, the depth of each dark crosshair image is deeper than that of a low magnification objective lens. This is because, in high-magnification observation, the field diaphragm 11 is used with a small aperture. Therefore, for example, an arbitrary point P on the surface of the first lens of the condenser lens 14
The light beam incident on the point P is sharp, and the depth of the dark cross line image generated at the point P becomes deep.

At the same time, since the aperture in the spherical direction of the spherical rays incident on the cross region on the lens becomes smaller, the contrast of the dark cross line increases. Even if you do not narrow down the field diaphragm 11,
Since the field diaphragm fi21 of the eyepiece lens 20 and the field diaphragm 11 are in a conjugate relationship, when observing a dark cross line through the field diaphragm 21, the same effect is obtained as using the field diaphragm 11 with the field diaphragm stopped down.

As described above, the dark crosshair image can be considered to be formed on the exit pupil plane of the objective lens 16, especially when a high magnification objective lens is used.

Now, the harmful light to be reduced by E, F, i is Analyzer 1
The bright part (dark cross line 2) visible in the exit pupil 23 when
This is the light flux that passes through the portions other than the portion 2 (Fig. 4). On the other hand, the light beam passing through the dark cross line 22 is blocked by the analyzer 19, and E, F, 'i is not reduced. Therefore, exit pupil 23
A cross-shaped aperture diaphragm is placed over the E and F to block harmful light.
If we use only light that does not reduce , then E, F,
A large polarizing microscope is possible. Of course, this cross-shaped aperture stop can provide the same effect no matter where it is placed in the optical system as long as it is conjugate with the exit pupil 23.

In this embodiment, a cross-shaped aperture stop 13 is placed at a conjugate position in front of the condenser lens 14 (a position where an aperture stop is normally placed).

Note that the polarizer 12 and analyzer 19 are adjusted so that the dark cross line 22 and the aperture of the cross-shaped aperture stop 13 match.
It is necessary to enable the aperture stop 13 to rotate around the optical axis in accordance with the rotation of the aperture stop 13. In addition, in order to use objective lenses with different N, A, (numerical apertures) interchangeably, it is necessary to be able to change the aperture size of the cross-shaped aperture stop 13 according to the pupil diameter. be.

Thus, according to the polarizing microscope according to the present invention, E and F can be increased simply by using a simple and inexpensive optical element such as the cross-shaped aperture diaphragm 13, thereby making it possible to increase E and F for specimens with only weak birefringence. Observation becomes possible.

FIG. 5 shows the entire optical structure of a reflective polarizing microscope as a second embodiment. 28 is a cross-shaped aperture stop as shown in FIG.
6 and is located in a position conjugate with the exit pupil of the objective lens 16 with respect to the illumination lens 30. Reference numeral 29 denotes a field stop, which is located at a position conjugate with the specimen surface 32 with respect to the illumination lens 30 and the objective lens 16. The vibration directions of the polarizer 12 and the analyzer 19 are perpendicular to each other. 31 is a half mirror. In this embodiment, if a circular aperture diaphragm is placed in place of the cruciform aperture diaphragm 28, the configuration is exactly the same as that of a normal reflection type polarizing microscope, and the functions of each part except the cruciform aperture diaphragm 28 are also normal. This is exactly the same as in the case of a reflective polarizing microscope. Also, compared to the first embodiment, the difference is that the illumination light flux travels backward through the objective lens 16 instead of the condenser lens 14 to illuminate the specimen, and that it is reflected at the specimen surface 32 instead of passing through the specimen. However, due to the principle that E and F decrease, the countermeasure against this is the cross-shaped aperture diaphragm 28.
Since the principle behind this process is exactly the same, detailed explanation thereof will be omitted.

Effects of the Invention As mentioned above, the highly sensitive light microscope according to the present invention has the extremely important practical advantage of being able to detect E, F, and i signals simply by using simple and inexpensive optical elements.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the optical system of an embodiment of a highly sensitive light microscope according to the present invention, Figure 2 is a front view of the cross-shaped aperture stop of the above embodiment, and Figure 3 is the polarization direction on the lens surface. FIG. 4 is a diagram showing the dark cross line observed in the exit pupil of the objective lens, FIG. 5 is a diagram showing the optical system of the second embodiment, and FIG. 6 is a diagram showing the optical system of the second embodiment. A front view of the cross-shaped aperture stop of the embodiment of
FIG. 7 is a diagram showing the optical system of a conventional polarizing microscope. 11...Field diaphragm, 12...Polarizer, 1
3...Cross-shaped aperture diaphragm, 14...Two condenser lenses, 15...Slide glass, 16...
・Objective lens, 17...pupil, 18...compensator 19...analyzer, 20...° eyepiece, 21...field diaphragm. Figure 3 23 Figure 5 Figure 16

Claims (4)

[Claims] (1) A polarizing microscope comprising a cross-shaped aperture stop located at the pupil of the objective lens or at a position conjugate thereto. (2) The polarizing microscope according to claim (1), wherein the cross-shaped aperture stop is arranged near a position conjugate with the pupil of the objective lens in the illumination optical system. (3) The polarizing microscope according to claim (1), wherein the cross-shaped aperture stop is rotatable around the optical axis. (4) The polarizing microscope according to claim (1), wherein the size of the aperture of the cross-shaped aperture stop is adjustable.