JPH0448202B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a dark field illumination device for an epi-illumination type microscope, and particularly to a so-called epidark objective lens.

(Background of the invention) Epidark illumination is an epi-illuminated microscope in which a ring-shaped light beam coaxial with the optical axis of the objective lens is supplied from around the objective lens, and this is condensed into a ring-shaped light beam provided near the tip of the objective lens. This is dark field illumination that is guided to the object plane by a member. Recently, the numerical aperture and working distance of objective lenses have become larger.
Along with this, the lens aperture of the objective lens is also becoming larger. For this reason, in conventional epidark illumination systems, it has become difficult to supply sufficient dark-field illumination light from around the objective lens.

(Objective of the Invention) The object of the present invention is to provide an objective lens for epidark which has a simple structure and can provide sufficient epidark illumination even with an objective lens having a large aperture without changing the structure of the microscope main body. It is about providing.

(Summary of the Invention) In order to achieve the above object, the present invention is arranged near the tip of an objective lens coaxially with the optical axis of the objective lens, and condenses a ring-shaped light beam that wraps around the objective lens to create an object. In an epidark objective lens having a ring-shaped light condensing member for detecting a surface, the ring-shaped light beam is directed outward between the ring-shaped light condensing member and the incident light side end of the lens barrel of the objective lens. A ring-shaped hollow lens member having a negative refractive power is provided to enlarge the diameter of the ring-shaped light beam by refraction.
This ring-shaped lens member refracts the ring-shaped light flux supplied to the incident light side end of the objective lens outward by the diverging action of its negative refractive power, thereby expanding the ring diameter of the ring-shaped light flux, and The light is guided to a ring-shaped light condensing member provided near the tip. Therefore, even if the objective lens has a large aperture, the ring-shaped light beam can be guided to the tip of the objective lens, and the ring-shaped condensing member can supply sufficient dark-field illumination light to the object surface. can.

In the present invention, in order to expand the aperture of the ring-shaped light beam, at least a ring-shaped lens member with a negative refractive power is required, and this ring-shaped lens member with a negative refractive power and a ring-shaped condensing member near the tip of the objective lens are required. It is possible to further provide a ring-shaped lens member with a positive refractive power between the two and convert the diverging light beam from the ring-shaped member with a negative refractive power into a parallel light beam parallel to the optical axis of the objective lens. According to this, the aperture of the ring-shaped light beam around the objective lens is not unnecessarily expanded, and even when the length of the objective lens is large, the aperture of the entire objective lens to accommodate the ring-shaped light beam is not unnecessarily enlarged. There is no need to increase the size, and it becomes possible to construct a compact objective lens for epidark.

(Example) FIG. 1 is a schematic sectional view showing the structure of a first example of an objective lens for epidark according to the present invention. Ring-shaped illumination light supplied from a light source (not shown) is
The light is reflected by an apertured reflecting mirror 12 provided obliquely within the microscope main body, and is directed toward the objective lens 10 . and,
The light is diverged by a ring-shaped lens member 1 with a negative refractive power provided in the objective lens barrel 11 near the end of the incident light side of the objective lens 10, and as a ring-shaped condensing member provided near the tip of the objective lens. It is guided to the object plane O by the ring-shaped concave reflecting mirror 2. As shown in the cross-sectional view A and the plan view B of FIG. 2, the negative refractive power ring-shaped member 1 is a hollow ring-shaped negative lens, and its inner diameter is slightly larger than the effective aperture of the entrance surface of the objective lens. There is. The ring-shaped light flux incident on the negative refractive power ring-shaped lens member 1 is subjected to a divergence effect here, and its aperture is enlarged to reach the ring-shaped concave reflector 2. Therefore, the aperture of the ring-shaped concave reflector is enlarged. Yes, objective lens 10
Even if the aperture is quite large, it is possible to supply sufficient dark field illumination light to the object plane O.

FIG. 3 is a sectional view showing a schematic configuration of a second embodiment of the present invention, and members having the same functions as those in FIG. 1 are given the same reference numbers. In this second embodiment, a ring-shaped lens member 4 having a positive refractive power is provided between a ring-shaped lens member 3 having a negative refractive power and a ring-shaped concave reflecting mirror 5 serving as a ring-shaped condensing member. Here, the negative refractive power ring-shaped lens member 3 and the positive refractive power ring-shaped lens member 4 have shapes as shown in FIGS. 4A, B and 5A, B, respectively. In each figure, A is a sectional view, and B is a plan view.
As shown, a positive refractive power ring-shaped lens member 4
has a larger aperture than the negative refractive power ring-shaped lens member 3, and receives the ring-shaped light beam diverged by the negative refractive power ring-shaped lens member 3 and converts it into a parallel light beam. Therefore, in the configuration of the second embodiment, the cross-sectional shape of the ring-shaped light beam from the ring-shaped lens member 4 with positive refractive power to the ring-shaped concave reflective member 5 as the ring-shaped condensing member is a ring with a constant radius. Therefore, the overall aperture of the objective lens can be kept constant during this period, and the overall configuration can be made compact.
Furthermore, by combining ring-shaped lens members with negative refractive power and positive refractive power as in this example,
It becomes possible to correct aberrations in the illumination light flux, particularly chromatic aberration, and to supply a better dark-field illumination light flux.

The ring-shaped lens members 1, 3, and 4 with negative refractive power and positive refractive power used in each of the above embodiments are similar to those of ordinary negative lenses and positive lenses, as shown in FIGS. 2, 4, and 5, respectively. Since the center is hollowed out, it has the advantage of being relatively easy to manufacture with high precision. In the above embodiment, a ring-shaped concave reflective member is used as the ring-shaped condensing member, but the present invention is not limited to this, and a ring-shaped hollow positive lens can also be used. Furthermore, the ring-shaped condensing member does not necessarily have to have a converging effect, but only has the function of concentrating the ring-shaped light beam onto the object plane. It can also be a conical reflecting mirror or a convex ring-shaped reflecting surface with a diverging effect.

(Effects of the Invention) As described above, according to the present invention, even for a large-diameter objective lens, the ring-shaped light flux supplied around the objective lens can be efficiently transferred to the object surface without making any changes to the microscope body. It is possible to lead to
Bright darkfield illumination is possible. Moreover,
Since a ring-shaped lens member with negative refractive power is used, the width of the ring-shaped light beam becomes large, which is advantageous in the case of a low-magnification objective lens with a wide actual field of view. Furthermore, the aperture of the ring-shaped light beam at the tip of the objective lens can be made larger than that of the conventional one, which is advantageous for increasing the working distance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a schematic configuration of a first embodiment according to the present invention, FIGS. 2A and B are a sectional view and a plan view of a negative refractive power ring-shaped lens member used in the first embodiment, and FIG. 3 4A, B and 5A, B are schematic cross-sectional views showing the configuration of the second embodiment according to the present invention.
These are a sectional view and a plan view, respectively, of a negative refractive power ring-shaped lens member and a positive refractive power ring-shaped lens member used in the second embodiment. [Description of symbols of main parts], 1, 3...Negative refractive power ring-shaped lens member, 2, 5... Ring-shaped condensing member, 4... Positive refractive power ring-shaped lens member, 10
...Objective lens, O...object surface.

Claims (1)

[Scope of Claims] 1. A ring-shaped condensing member disposed near the tip of the objective lens coaxially with the optical axis of the objective lens, for condensing a ring-shaped light flux that wraps around the objective lens and illuminating the object surface. In the objective lens for epidark, the diameter of the ring-shaped light flux is expanded by refracting the ring-shaped light flux outward between the ring-shaped condensing member and the end of the incident light side of the lens barrel of the objective lens. An objective lens for epidark, characterized in that it is provided with a ring-shaped hollow lens member having a negative refractive power.