JP2017037276A - Microscope objective lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microscope objective lens which comprises an optical system with a relatively small number of constituent lenses, is compact, and allows for observing high resolution images.SOLUTION: An objective lens for optical microscopes of the present invention comprises a first lens group having positive refractive power as a whole and a second lens group arranged in order from the object side. The first lens group comprises a meniscus lens having a concave surface on the most object side and negative refractive power cemented together with a lens having a convex surface on the image side and positive refractive power. The second lens group comprises a biconvex lens having positive refractive power cemented together with a meniscus lens having a convex surface on the image side and negative refractive power.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an objective lens for a mobile optical microscope, and more particularly to an objective lens having a sufficient working distance, which is an optical system including two sets of cemented lenses as elements of an optical system.

  A microscope objective lens must have various aberrations (spherical aberration, coma aberration, field curvature aberration, astigmatism, etc.) corrected sufficiently, but at the same time, various requirements to limit the degree of freedom in aberration correction Must be satisfied. For example, in order to obtain a high resolving power, the numerical aperture (NA) must be large, and in order to avoid contact between the subject and the objective lens, it is desirable to have a long working distance (WD). On the other hand, considering that various objective lenses are used in exchange, there are restrictions on the length of the lens system and restrictions such as keeping the optical total length constant. Furthermore, in a normal microscope optical system, if chromatic aberration is not corrected sufficiently well, an image becomes difficult to be seen due to the influence of color blur.

  It is very difficult to satisfy all these conditions, and in order to overcome the problem and construct a microscope objective lens that satisfies the above requirements, an extremely complicated optical system that uses many lenses with strong curvature In addition, an extraordinary partially dispersive optical material such as fluorite or a large number of cemented lenses must be used, which increases costs.

  In general, an optical system is configured by combining a large number of lenses, but it is known that not only a spherical lens but also an aspherical lens or a gradient index lens can be used in order to enhance aberration correction capability.

JP 2010-014856 A

  The present invention provides a microscope objective lens in which various aberrations are favorably corrected in the visible region while having a small and relatively simple configuration.

In order to solve the above-described problem, the microscope objective lens of the present invention includes a first lens group having a positive refractive power as a whole and a second lens group in order from the body side, and the first lens group is concave on the most object side. A biconvex lens L3 having a negative refractive power and a meniscus lens L1 having a negative refractive power and a lens L2 having a positive refractive power with a convex surface facing the image surface. The second lens group has a positive refractive power. And a meniscus lens L4 having negative refractive power with a convex surface facing the image surface side, the focal length of the entire lens system is f, the working distance is WD, the back focus is BF, and the total optical length is OL. and when
WD / f> 1.95 (1)
BF / OL> 0.40 (2)
It satisfies the following condition.

  Since the number of components of the optical system is relatively small, a small microscope objective lens can be realized, and various aberrations can be sufficiently corrected by the combination of the cemented lenses. In addition, since a sufficient working distance is ensured, it is possible to provide a microscope objective lens that improves user operability and enables clear and bright observation.

Lens configuration diagram of Example 1 Various aberration diagrams of Example 1 Lens configuration diagram of Example 2 Various aberration diagrams of Example 2 Lens configuration diagram of Example 3 Various aberration diagrams of Example 3

  Examples 1 to 3 of the present invention will be described. Cross-sectional views showing the lens configurations of Examples 1 to 3 are shown in FIGS. 1, 3, and 5, respectively.

  Examples 1 to 3 include a first lens group having a positive refractive power as a whole and a second lens group in order from the object side, and the first lens group has a negative refractive power with the concave surface facing the most object side. Consists of a meniscus lens L1 and a lens L2 having a positive refractive power with the convex surface facing the image surface. The second lens unit has a biconvex lens L3 having a positive refractive power and a convex surface facing the image surface side. In addition, a meniscus lens L4 having a negative refractive power is cemented.

  The aberration diagrams of Examples 1 to 3 are shown in FIG. 2, FIG. 4, and FIG. From the left side of the aberration diagram, spherical aberration, field curvature aberration, and distortion are shown.

  The data of an Example are shown below. f is the focal length of the entire optical system, BF is the back focus, R is the radius of curvature of the lens, D is the distance between the optical systems, N is the refractive index, and ν is the Abbe number.

Example 1

(Example 2)

(Example 3)

L1: First lens
L2: Second lens
L3: Third lens
L4: Fourth lens G1: First lens group G2: Second lens group
STO: Aperture ΔS: Sagittal image plane ΔM: Meridional image plane
WD: Working distance BF: Back focus
OL: Optical total length
OBJ: Object position
IMG: Image plane position

Claims (3)

A meniscus lens L1 having a negative refractive power, the first lens group having a positive refractive power as a whole in order from the object side, and a second lens group, the first lens group having a concave surface closest to the object side, and an image Consists of a cemented lens L2 having a positive refractive power with the convex surface facing the surface, and the second lens group has a negative refractive power with the convex surface facing the image surface side and a biconvex lens L3 having a positive refractive power. Consists of a joint with a meniscus lens L4, where the focal length of the entire lens system is f, the working distance is WD, the back focus is BF, and the total optical length is OL.
WD / f> 1.95 (1)
BF / OL> 0.40 (2)
A microscope objective lens characterized by satisfying the following conditions: When the combined focal length of the first lens group is f _g1 , the combined focal length of the second lens group is f _g2 , and the focal length of the entire lens system is f
6.33 <f _g1 / f <9.36 (3)
1.45 < _fg2 / f <2.97 (4)
A microscope objective lens characterized by satisfying the following conditions: The refractive power of the first lens is φ ₁ , the refractive power of the second lens is φ ₂ , the refractive power of the third lens is φ ₃ , the refractive power of the fourth lens is φ ₄ , and the focal length of the entire lens system is f. When
1.68> | φ ₁ | ・ f> 2.39 (5)
1.42> | φ ₂ | ・ f> 1.99 (6)
1.64> | φ ₃ | ・ f> 1.72 (7)
0.93> | φ ₄ | ・ f> 0.99 (8)
The microscope objective lens according to claim 1, wherein the following condition is satisfied.

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