JP2006171183A - Condenser lens for microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condenser lens for a microscope which secure a high numerical aperture (≥0.75) and a relatively long working distance (≥0.4f), while suppressing the aberrations of the visual field and aberrations of pupil. <P>SOLUTION: The condenser lens for the microscope is constituted, by arranging a cemented negative meniscus lens (L1) which is concave to a light source side and three single-body positive lenses (L2, L3, and L4), in this order, from the light source side to an observed body side. The cemented negative meniscus lens (L1) functions to raise the incident light beam from the light source side to a high position (distant from the optical axis), to thereby increase the operating distance. Further, the cemented negative meniscus lens (L1) serves to correct the chromatic aberration of the condenser lens as a whole and also correct aberrations of the visual field, in cooperation with the three single-body correct lenses (L2, L3, and L4). The single-body positive lenses L2, L3, and L4 function to correct the aberrations of the visual field, while suppressing the aberrations of the pupil. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a condenser lens for a microscope that is suitable for observation of a biological sample by transmitted illumination, particularly observation accompanied by manipulation, and observation of a transparent sample such as differential interference observation and phase difference observation.

  It is desirable that the working distance of this type of condenser lens (eg, Patent Document 1) be as long as possible (in this specification, “working distance” refers to the distance between the condenser lens and the surface to be observed of the sample). Of geometric distance.) This is because the biological sample is stored in a transparent container and illuminated through the container, so that if the working distance of the condenser lens is not secured long, the field stop image is displayed when the container is thick. This is because the image cannot be projected to the surface to be observed, and the contrast of the image may be lowered.

In addition, it is desirable that the numerical aperture NA of this type of condenser lens is ensured to be as high as (for example, 0.75 or more) the same as the numerical aperture NA (for example, 0.8) of the objective lens used therewith. This is because if the numerical aperture NA of the condenser lens is insufficient, the performance (resolution) of the objective lens cannot be sufficiently exhibited.
Further, the aberration when the condenser lens projects the light source image onto the pupil plane of the objective lens (hereinafter referred to as “pupil aberration”) is the aberration (when the condenser lens projects the field stop image onto the surface to be observed). Hereinafter, it is desirable that it is sufficiently suppressed together with “field aberration”. This is because differential interference observation methods and phase contrast observation methods are often applied to the observation of transparent biological specimens, and pupil surface manipulation is involved in the formation of observation images at that time. This is because it directly affects the image.
JP 2003-156691 A

However, since it is difficult for a single condenser lens to satisfy all of the above requirements, a short working distance is allowed when a high numerical aperture is required, and a low numerical aperture is required when a long working distance is required. I must tolerate that.
FIG. 3A shows an example of the configuration of a conventional condenser lens having a high numerical aperture and a short working distance. In FIG. 3, a sample is indicated by a symbol O. The specifications of the condenser lens having this configuration are, for example, a focal length f = 17 mm, a numerical aperture NA = 0.8, and a working distance OD = 0.3f = 5.1 mm.

FIG. 3B shows an example of the configuration of a conventional condenser lens having a low numerical aperture and a long working distance. The specifications of the condenser lens having this configuration are, for example, a focal length f = 17 mm, a numerical aperture NA = 0.55, and a working distance OD = f = 17 mm. Incidentally, in this configuration, even if various aberrations are sacrificed, the numerical aperture NA can be increased only to about 0.6.
Accordingly, an object of the present invention is to secure a high numerical aperture (0.75 or more) and a relatively long working distance (0.4 f or more) while suppressing the aberration of the field of view and the aberration of the pupil to the same level as the conventional one. An object of the present invention is to provide a microscope condenser lens that can be used.

The microscope condenser lens according to claim 1 is formed by arranging, in order from the light source side toward the object to be observed, a cemented negative meniscus lens having a concave surface facing the light source side and three single positive lenses. It is characterized by.
The microscope condenser lens according to claim 2 is the microscope condenser lens according to claim 1, wherein the three single positive lenses are arranged in order from the light source side to the object to be observed, Two positive meniscus lenses having a convex surface on the side are arranged.

A condenser lens for a microscope according to a third aspect is characterized in that in the condenser lens for a microscope according to the first aspect or the second aspect, a parallel plate-shaped protective glass is disposed closest to the object to be observed.
A condenser lens for a microscope according to a fourth aspect is characterized in that in the condenser lens for a microscope according to any one of the first to third aspects, the lens surfaces of all the lenses are spherical surfaces.

The microscope condenser lens according to claim 5 is the microscope condenser lens according to any one of claims 1 to 4, wherein the single-side positive lens disposed closest to the object to be observed is disposed on the light source side. The curvature radius r4 of the lens surface and the focal length f of the entire condenser lens satisfy the expression 0.7f <r4 <f.
The condenser lens for a microscope according to claim 6 is the condenser lens for a microscope according to any one of claims 1 to 5, wherein the numerical aperture NA, the working distance OD, and the focal length f of the entire condenser lens are: The condition of NA> 0.75 and OD> 0.4f is satisfied.

  According to the present invention, a microscope capable of ensuring a high numerical aperture (0.7 or more) and a relatively long working distance (7 mm or more) while suppressing the aberration of the field of view and the aberration of the pupil to the same level as the conventional one. Realizes condenser lenses.

Embodiments of the present invention will be described below.
This embodiment is an embodiment of a condenser lens.
FIG. 1 is a conceptual diagram of a microscope on which the condenser lens is mounted.
Reference numeral 16 in FIG. 1 denotes this condenser lens (concept). The object to be observed is a sample O such as a living cell in a solution O ′ (such as physiological saline or culture solution) contained in a transparent container O ″ (such as a petri dish).

The container O ″ is fixed for manipulation, and instead, the objective lens 17 is movable in the optical axis direction. By the movement, the focus of the objective lens 17 is adjusted to the observation surface of the sample O. .
Here, a differential interference observation method is applied to the microscope in order to observe the transparent sample O. That is, the illumination light emitted from the light source 11 illuminates the sample O through the collimator lens 12, the field stop 13, the analyzer 14 </ b> A, the DIC prism 14, the aperture stop 15, and the condenser lens 16. Light emitted from the sample O enters the observation eye 22 via the objective lens 17, the DIC prism 19, the analyzer 20, and the eyepiece lens 21.

After passing through the analyzer 14A, the illumination light is split into a pair of lights by the DIC prism 14, and separately passes through the sample O and then reintegrated by the DIC prism 19, and passes through the analyzer 20 together. Light that can interfere. The interference light generated thereby forms an observation image (differential interference image) of the sample O on the retina of the observation eye 22.
In this microscope, as the objective lens 17, a finder objective lens having a magnification of 10 times or a finder objective lens having a magnification of 4 times and an immersion objective lens having a magnification of 40 to 60 times are mounted.

At the time of observation, one of these objective lenses is selectively inserted into the optical path of the microscope. Particularly, the tip of the immersion objective lens is immersed in the solution O ′ in a focused state.
The numerical aperture NA of the immersion objective lens is set to a value within a range where manipulation is possible. Here, in order to obtain as high a resolving power as possible, the numerical aperture NA of the immersion objective lens is set to a maximum value within a manipulatable range. That is, the numerical aperture NA of the immersion objective lens is 0.8.

On the other hand, since a high resolution is not required for the finder objective lens, the numerical aperture NA of the finder objective lens is assumed to be lower than that of the immersion objective lens.
Hereinafter, among these objective lenses, the objective lens being inserted into the optical path of the microscope is simply referred to as “objective lens 17”.
Next, the specifications of the condenser lens 16 will be described.

The illumination field size of the condenser lens 16 is set to a value corresponding to the maximum value of the field of view of the objective lens 17. That is, it is set to a value corresponding to the field of view of the 4 × finder objective lens.
Further, the numerical aperture NA of the condenser lens 16 is set to a value corresponding to the maximum value of the numerical aperture NA of the objective lens 17. That is, the value (0.7 or more) corresponding to the numerical aperture NA (= 0.8) of the immersion objective lens is set.

Further, the working distance OD of the condenser lens 16 is set as large as possible. Here, the working distance OD of the condenser lens 16 is 7 mm or more.
Hereinafter, the numerical aperture NA and the working distance OD of the condenser lens 16 are referred to as “illumination-side numerical aperture NA” and “illumination-side working distance OD”, respectively.
Further, the aberration of the pupil and the aberration of the visual field of the condenser lens 16 can be suppressed to the same extent as in the conventional case.

Next, the premise for designing the condenser lens 16 will be described.
One method of increasing the working distance of the condenser lens 16 is to increase the focal length f of the condenser lens 16, but the condenser lens 16 requires not only a longer working distance but also a higher numerical aperture. As a result, this method leads to enlargement of the pupil surface and, consequently, enlargement of the illumination optical system (reference numerals 11 to 16 in FIG. 1). Needless to say, the DIC prism 14 is also enlarged, which is inconvenient. Therefore, in the present condenser lens 16, it is assumed that the focal length f is suppressed to be equivalent to that of the conventional condenser lens (17 mm).

In addition, as one of the methods of increasing the working distance and aberration correction of the condenser lens 16, there is a method of making the lens surface aspherical. With this method, a pair of light beams for forming a differential interference image is used. Since the polarization state is disturbed, the interference condition is deteriorated, and hence the differential interference image is deteriorated. Therefore, it is assumed that the condenser lens 16 does not use an aspheric lens.
Next, the configuration of the condenser lens 16 will be described in detail.

FIG. 2 is a configuration diagram of the condenser lens 16. In addition, in FIG. 2, the sample O was shown notionally.
As shown in FIG. 2, the condenser lens 16 includes a first lens group G1, a second lens group G2, and a protective glass CG in order from the light source side to the sample O side.
The first lens group G1 includes a cemented negative meniscus lens L1 having a concave surface facing the light source, the second lens group G2 includes three single positive lenses L2, L3, and L4, and the protective glass CG is a parallel plate. Consists of. The protective glass CG seals the tip (sample O side) of the condenser lens 16.

The single positive lens L2 is a biconvex lens, and the single positive lenses L3 and L4 are positive meniscus lenses each having a convex surface facing the light source.
Next, the function of each element of the condenser lens 16 will be described.
(Protective glass CG)
The protective glass CG has a role of protecting the condenser lens 16.

  Specifically, when the objective lens 17 of the microscope of FIG. 1 is an immersion objective lens, the solution O ′ (physiological saline, culture solution, etc.) adheres to the tip portion thereof. For this reason, when the objective lens 17 is switched, the attached solution O ′ may drop and reach the condenser lens 16. Further, the solution O ′ may overflow from the container O ″ and reach the condenser lens 16 directly.

If the protective glass CG is not provided, the final surface of the condenser lens 16 is a concave surface with the concave surface facing the sample O, so that the liquid tends to stay and cleaning is difficult. However, if there is the protective glass CG, the final surface becomes a flat surface, so that the liquid does not easily accumulate and cleaning becomes easy. Therefore, the protective glass CG protects the condenser lens 16 from a liquid such as the solution O ′.
The protective glass CG also has a role of aberration correction.

  Specifically, the protective glass CG has a function of generating a spherical aberration component of the field aberration on the plus side. By this function, the curvature of the lens surfaces of the single positive lenses L3 and L4 (both positive meniscus lenses) can be reduced. By reducing the curvature of these lens surfaces, it is possible to ensure both a long working distance OD on the illumination side and correction of pupil aberration. Further, the reduction in curvature also has an effect of facilitating the manufacture of these single positive lenses L3 and L4.

(Junction negative meniscus lens L1)
The cemented negative meniscus lens L1 works to increase the working distance by lifting the incident light from the light source side to a high position (a position away from the optical axis).
The cemented negative meniscus lens L1 has a role of correcting the entire chromatic aberration of the condenser lens 16 and a role of correcting the spherical aberration component of the field aberration together with the three single positive lenses L2, L3, and L4. .

(Single positive lenses L2, L3, L4)
The single positive lenses L2, L3, and L4 function to correct aberrations related to light rays (light rays having a large angle with the optical axis) for increasing the numerical aperture NA on the illumination side. It works to correct the components.
Here, if only the aberration correction of the visual field is considered, it is desirable that the curvature of the lens surfaces of the single positive lenses L3 and L4 (both positive meniscus lenses) is large. This brings about the contradictory effect of making the aberration worse and making it difficult to ensure the working distance OD on the illumination side.

Specifically, when the radius of curvature r4 of the surface of the single positive lens L4 on the light source side is smaller than 0.7f, the aberration of the pupil is deteriorated and it is difficult to ensure the working distance OD on the illumination side. On the other hand, when the radius of curvature r4 is larger than the focal length f of the condenser lens 16, the field aberration correction is insufficient.
For this reason, it is desirable that the curvature radius r4 satisfies the following formula (1).

0.7f <r4 <f (1)
Next, the effect of the condenser lens 16 will be described.
According to the above configuration, the condenser lens 16 that satisfies the following expressions (2) and (3) can be realized while suppressing the aberration of the pupil and the aberration of the visual field to the same extent as in the conventional example.
NA> 0.75 (2)
OD> 0.4f (3)
If Expression (2) is satisfied, observation can be performed with the maximum resolving power within the range where manipulation is possible.

If equation (3) is satisfied, a good differential interference image can be obtained regardless of the type of container O ″ (type of petri dish). That is, if equation (3) is satisfied, various bottom thicknesses can be obtained. In each case where various containers O ″ are used, the field stop image can be reliably projected onto the sample O.
Further, in the above configuration, when the curvature radius of each lens surface, the interval between each surface, and the refractive index of each member are optimized, the aberration of the pupil and the aberration of the field of view are suppressed to the same level as the conventional example, and the focal length is reduced. The condenser lens 16 with f = 17, illumination-side numerical aperture NA = 0.8, and illumination-side working distance OD = 0.48f = 8.2 mm is realized.

  Examples of the condenser lens described above are shown in Tables 1 and 2. Table 1 shows lens data, and Table 2 shows specifications. In Table 1, “R” is a radius of curvature, “d” is a surface interval, and “nd” is a refractive index with respect to the d-line.

なお、本実施形態の顕微鏡には、微分干渉観察法が適用されているが、位相差観察法が適用されていてもよい。位相差観察も微分干渉観察と同様に、瞳の収差補正の必要性が高いので、本コンデンサレンズ１６は、好適である。

In addition, although the differential interference observation method is applied to the microscope of the present embodiment, a phase difference observation method may be applied. The phase difference observation is suitable for the aberration correction of the pupil as in the case of the differential interference observation. Therefore, the condenser lens 16 is suitable.

  Further, in the condenser lens 16 of the present embodiment, the protective glass CG may be omitted. However, the provision of the protective glass CG is advantageous in terms of aberration correction and protection.

It is a schematic block diagram of the microscope in which this condenser lens is mounted. It is a block diagram of this condenser lens. It is a block diagram of the conventional condenser lens.

Explanation of symbols

11 Light source 12 Collimator lens 13 Field stop 14, 19 DIC prism 14A Analyzer 15 Aperture stop 16 Condenser lens O Sample O 'Solution O "Container 17 Objective lens 20 Analyzer 21 Eyepiece 22 Observation eye G1 First lens group G2 Second Lens group CG Protective glass L1 Joint negative meniscus lens L2 Biconvex lens L3, L4 Positive meniscus lens

Claims (6)

From the light source side to the object side,
A cemented negative meniscus lens with a concave surface facing the light source;
A condenser lens for a microscope, comprising three single positive lenses. The microscope condenser lens according to claim 1,
The three single positive lenses are
A microscope condenser lens comprising a biconvex lens and two positive meniscus lenses having a convex surface facing the light source in order from the light source side toward the object to be observed. In the condenser lens for microscopes according to claim 1 or 2,
A microscope condenser lens, characterized in that a parallel plate-shaped protective glass is disposed on the most object side. In the condenser lens for microscopes as described in any one of Claims 1-3,
A condenser lens for microscopes, characterized in that the lens surfaces of all lenses are spherical. In the condenser lens for microscopes as described in any one of Claims 1-4,
The radius of curvature r4 of the lens surface on the light source side of the single positive lens arranged closest to the object to be observed, and the focal length f of the entire condenser lens are:
0.7f <r4 <f
A condenser lens for a microscope characterized by satisfying the formula: In the condenser lens for microscopes as described in any one of Claims 1-5,
The numerical aperture NA, the working distance OD, and the focal length f of the entire condenser lens are
NA> 0.75, OD> 0.4f
A condenser lens for a microscope characterized by satisfying the formula:

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