Optical: systems and elements – Compound lens system – Microscope
Reexamination Certificate
2001-03-05
2002-06-04
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Compound lens system
Microscope
C359S368000, C359S385000, C359S821000
Reexamination Certificate
active
06400501
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical microscope having an objective lens interchanging mechanism.
When observing a specimen such as a vital cell, observation is performed while manipulating the specimen with a manipulator and measuring the potential with an electrode. In this case, the entire portion of the specimen is observed with a low-magnification objective lens to determine the portion to be observed. Thereafter, the low-magnification lens is switched to a high-magnification lens, and observation is performed in detail.
Conventionally, an optical microscope having an objective lens interchanging mechanism is proposed in order to use, by switching, objective lenses having different magnifications in this manner. For example, optical microscopes disclosed in Jpn. UM Appln. KOKAI Publication No. 6-40910 and No. 6-4720 and Jpn. Pat. Appln. KOKAI Publication No. 8-338940 are known. In each of these optical microscopes, a plurality of objective lenses having the same mount screw diameter that complies with the international standards (parfocal distance: 45 mm; mount screw diameter W: 20.32; and thread height: 36) and different magnifications are mounted to the support. An objective lens having an optimum magnification can be inserted on the observation optical axis in accordance with a change in observation magnification.
When the objective lenses are to be used in fluorescence observation by switching their magnification in this manner, as a low-magnification objective lens for observing the entire portion of the specimen, one having a magnification as low as possible is usually preferable. Conventionally, the lower limit of the magnification that can be employed is about 10×. This is because the lower the magnification, the darker the observation image. To observe a fluorescent image which is originally dark, the magnification must be at least about 10×. If not, observation becomes impossible.
To allow fluorescence observation at a low magnification, the observation image must be made bright. The fluorescent intensity may be increased by increasing the intensity of excitation light. If the intensity of the excitation light is excessively increased, the specimen may be damaged or discolored with fluorescence, causing a trouble in observation.
To eliminate this, as a low-magnification objective lens, for example, one having a magnification lower than 10× and capable of ensuring a sufficiently high brightness for the observation image may be used. According to the optical microscope having the objective lens interchanging mechanism described above, the objective lenses to be mounted to the support must comply with the same standards and have the same mount screw diameter. If the objective lenses have different mount screw diameters, they cannot be mounted to the objective lens interchanging mechanism simultaneously and cannot be interchangeably used. If the objective lenses have different parfocal distances, when they are replaced, the focal point is largely displaced from the specimen surface due to the parfocal difference, and focusing must be performed again, leading to inconveniences in use.
For this reason, an optical microscope which can stably perform fluorescence observation with a low-magnification objective lens is sought for. Particularly, the following requirements are desired. A conventional illumination optical system must be used to suppress an increase in manufacturing cost, the compactness of the microscope must be maintained, and the microscope must be excellent in operability.
The objective lens switching operation described above poses the following problems.
Generally, in a microscope, a plurality of objective lenses are detachably held by an objective lens revolver which performs a switching operation among the plurality of objective lenses such that they can be inserted in and removed from the observation optical axis. Observation at a desired magnification is performed by turning the objective lens revolver to switch the objective lens on the observation optical axis.
In a microscope, since the height of eye point (the distance from the desktop surface to the operator's eye) with which the operator can perform observation with a natural posture is substantially fixed, the sizes of the respective portions of the microscope are limited. For example, the distance from the mounting surface of the objective lens, with which the objective lens is to be mounted to the objective lens revolver, to the sample surface (this distance will be referred to as the parfocal distance hereinafter) is usually designed to be about 45 mm. In an objective lens having a very low magnification of 1× or less, its parfocal distance is as very long as about 200 mm. If such an objective lens is used, its entire length cannot be accommodated within the parfocal distance. Therefore, it is impossible to change the observation magnification by only turning the objective lens revolver to switch the objective lens.
In order to solve this problem, conventionally, a microscope disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-54253 is known. According to this reference, one of a plurality of first objective lenses is defined as a very-low-magnification objective lens. The second objective lens fixed in an optical path is arranged with respect to a revolver means that performs a switching operation among the plurality of first objective lenses so that the selected one is located in the optical path. An observation image of an object is formed through the first objective lens selected by the revolver means and the second objective lens. A very-low-magnification auxiliary lens, which is to be inserted in an interlocked manner with selection of the very-low-magnification objective lens done by the revolver means, is arranged in the optical path between the first and second objective lenses. The first very-low-magnification objective lens is constituted by the very-low-magnification auxiliary lens and the very-low-magnification objective lens. More specifically, the very-low-magnification objective lens, the entire length of which cannot be accommodated within the parfocal distance, is divided into two portions, i.e., the first objective lens mounted to the revolver means, and the very-low-magnification auxiliary lens, and is constituted such that its synthetic focal distance becomes about 200 mm. The observation magnification, including the very low magnification, can be changed by inserting and removing the very-low-magnification auxiliary lens in and from the optical path in an interlocked manner with selection of the very-low-magnification objective lens by the revolver means.
In the microscopes disclosed in the above references, merely the very-low-magnification auxiliary lens is arranged in the optical path between the first and second objective lenses, and no description is made concerning the practical arrangement of the very-low-magnification auxiliary lens. For this reason,
(1) For example, when an extra space is newly prepared exclusively for the very-low-magnification auxiliary lens, not only the eye point described above becomes high, but also the entire microscope becomes large.
(2) The switching mechanism for inserting and removing the very-low-magnification auxiliary lens in and from the optical path must be prepared exclusively for the very-low-magnification objective lens, and must be interlocked with the turning operation of the revolver means. This leads to a complicated arrangement and an increase in cost, which is not preferable.
(3) Although the observation magnification can be changed, the microscopic method must be switched by separately providing a switching mechanism, resulting in a degradation in operability.
Generally, a very-low-magnification objective lens has a long focal distance and a large radius of lens curvature. Particularly, when performing observation with reflected light, noise such as flare, ghost, or the like which affects original image formation tends to be caused by repeated surface
Adachi Sadashi
Fujiwara Masaru
Tsuchiya Atsuhiro
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Nguyen Thong
Olympus Optical Co,. Ltd.
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