JPS5837614A - Reflection type differential interference microscope - Google Patents

Abstract

PURPOSE:To obtain a uniform visual field when the surface of an object having curvature such as the cornea is observed by disposing a double refractive prism in the position conjugate with the central point of curvature of an object to be inspected having a spherical surface with respect to an object lens or making said disposition possible. CONSTITUTION:A Wollaston prism 5 is disposed at the conjugate point C' with the center C of curvature of an object surface 17 with respect to an objective lens 6 in such a way that the branching points of an ordinary ray (o) and an extraordinary ray (e) by the prism 5 coincide. Consequently, the two rays (o) and (e) out from the prism 5 are made incident vertically to the surface 17 so as to be concentrated at the center C of the surface 17 by the lens 6 and are reflected by tracing the same route reversely. Then the differences in brightness and darkness in the visual field for observation are eliminated, hues are made constant and the differential interference image of the surface 17 is observed satisfactorily and accurately within the uniform visual field.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflection type differential interference microscope for observing the surface of an object having a convex or concave uniform curvature.

General reflective differential interference microscopes are well known. Figure 1 shows the principle. The light emitted from the light source 1 is converted into a parallel light beam by the condenser lens 2, converted into linearly polarized light by the polarizer 3, reflected by the leaf mirror 4, and incident on the Wollaston prism 5. As is well known, the Wollaston prism 5 is made by laminating two (pear-shaped) crystal plates whose optical axes are perpendicular to each other. Here, the incident light beam 11 has vibration directions that are mutually different due to the birefringence of the crystal. The ordinary ray 0 and the extraordinary ray e, which are perpendicular to each other, come out divided by 1ζ・1[. Since the focal point on the image side of the objective lens 6 coincides with the focal point on the image side of the objective lens 6, each of the rays becomes parallel to the original axis after exiting the objective lens 6.The two rays reflected by the plane object 7 each follow the same path in reverse. , in the analyzer 8, only the polarized light components are transmitted through parallel lines in the direction of the polarization axis.The binary lines then interfere with each other to form an image corresponding to the minute 111 unevenness of the object surface, and this interference image is The eyepiece lens 9 is used for magnification observation.In this case, the reflection source gland passes through the optical path of the incident -11 line, becomes a ray of light that travels in the same direction again at the Wollaston prism 5, and the wavefront associated with it EO and E@ are parallel to each other, and the distance between them is uniform over the entire space, and the field of view is uniform.

Next, when this reflection type differential interference microscope is applied to observation of the surface of an object having curvature, f is shown in FIG. 2. In FIG. 2, the illumination system and eyepiece are omitted for simplicity. In this case, the reflected light rays do not intersect at the Wollaston prism 5 due to the curvature of the object surface 17, so the two light beams travel in the same direction. If, t, fc
The wavefronts Eo and Ee are not parallel and have different intervals depending on the location. For this reason, bright and dark stripes or differences in hue occur in the observation field, making it impossible to obtain a uniform field of view. In this way, the surface of the object being tested is not a flat surface, but has a certain curvature, like a square leg.
In the case of ``'f'' stones, it is difficult to observe them because it is not possible to obtain a uniform background in the observation field using a conventional reflection type differential interference microscope.

The present invention solves the above-mentioned problems and provides a uniform reflection field when observing the entire surface of an object with curvature! ! , the objective is to obtain a model of interference acupuncture needle γ8.

In the reflection type differential interference microscope according to the present invention, the branching point between the ordinary ray and the extraordinary ray by a birefringent prism such as a Wollaston prism is conjugated with the center of curvature of the surface of the Fji-shaped object to be examined in the objective lens. Wollaston prisms are arranged to match the points.

The present invention will be explained based on diagram ψ73 below.

No. 31yl shows the configuration of the reflective interferometer according to the present invention. No. 4 is a schematic diagram, and No. 11l shows the illumination system and eyepiece necessary for the reflection type f1 interferometer. You can use all the conventional ones in that size. As shown in the figure, the object surface 170 is conjugate with the center of curvature (C) with respect to the objective lens 6, and the Wollaston prism 5 is located in (C').
The Wollaston prism 5 is arranged so that the branch point between the line 0 and the extraordinary light ii$i1a coincides with each other. With this j4%, the two light beams O and e exiting the Wollaston prism 5 are focused by the objective lens at the center of curvature C 170 facing the object surface, and enter the object surface directly ("f-").

Therefore, the reflected rays follow the same path in reverse and become the source of traveling in the same direction at the Wollaston prism 5, adding 1! to the ordinary ray! +′ wavefront Eo and wavefront Ee associated with the extraordinary ray
are parallel to each other. Therefore, there is no difference in brightness and darkness in the image, the hue is constant, and the differential interference image of the object surface 17 can be observed satisfactorily and accurately within a -4-like field of view.

Here, 1@point distance Fffp of objective lens 6? f s
If the radius of curvature of the object surface 11 is 'f: r s, the distance between the object surface 17 and the objective lens is ##'f-d, then the distance between the branch point of the two rays by the Wollaston prism 5 and the objective lens is ll
#t is given by In a Wollaston prism, the branch point between the ordinary ray and the extraordinary ray is generally located inside the prism, so in reality, the Wollaston prism may be placed at a distance t given by the above equation from the objective lens. 11. When using the Nomarski prism, which is known as an improvement on the Wollaston prism, the prism and the branching point of the two light beams are far apart.4. Therefore, the distance between the prism and the objective lens is larger than the value of t in the above equation.

Figure 3 shows the case where the object surface is a convex surface, but the object [f
The present invention is equally effective even if ji is a concave surface, and the optical path diagram of the main part in this case is shown in Figure 2t54. In this case as well, a Wollaston prism is placed at a point C' that is conjugate with respect to the center of curvature C of the object surface 170 and the objective lens 6.
The branch points of the luminous flux match. The distance t between the branching point of the two light beams and the objective lens 6 can be calculated in the same way by setting the radius of curvature r to be negative in the above equation, and even if the object surface is concave, it is possible to obtain a uniform background in the observation field. You can do it.

Even if the surface shape of the curved object surface is not a perfect sphere, the shape of the center to be observed is made to resemble a spherical surface with a certain radius, and at this radius of curvature, the arrangement of the Wollaston prism is If IW' is determined, it is possible to obtain a uniform field of view.

Furthermore, in the embodiments shown in FIGS. 3 and 4, a means is provided to change the optical path length between the Wollaston prism 5 and the objective lens 6, so that the length of the optical path between the Wollaston prism 5 and the objective lens 6 can be adjusted depending on the object to be examined.
, it is preferable to enable one section of the microscope, and such a means may be provided in a conventional reflection scanning microscope as shown in FIG. 1 to carry out the entire invention.

As described above, according to the present invention, like the cornea! I't
+ Even if the body surface has the entire curvature, a reflective differential interference -g mirror can be obtained that allows observation with a uniform field of view. In addition, in this device a, as mentioned above, instead of the Wollaston prism, it is also possible to use a Nomarski prism which has the same function and whose branching point between the ordinary ray and the extraordinary ray is outside the prism, and is equally effective. Needless to say.

[Brief explanation of the drawing]

Figures 1 and 2 are optical path diagrams of conventional equipment, Figures 3 and 4
The figure is an optical path diagram of a reflection me interference microscope according to the present invention. [Explanation of symbols of main parts] 5...Wollaston prism (birefringent prism) 6...Objective lens O...ordinary ray e...extraordinary ray output 1 person 2 Nippon Kogaku Kogyo Co., Ltd. No. 1st ward O 8th ward-G

Claims (1)

[Claims] The birefringent prism is arranged so that the branch point of the ordinary ray and the extraordinary ray by the birefringent prism is located at a position on the principal axis of the objective lens and at a position conjugate with the center of curvature of the spherical surface of the object to be examined with respect to the nuclear objective lens. A reflection type differential interference microscope and a mirror, characterized in that a mirror is arranged or can be arranged.