JP2001264637A - Spherical aberration compensating optical system and device, and optical observation device equipped with compensating optical system or device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system that is disposed on the rear side of an existing objective lens (on an image side) so that amount of spherical aberration caused by the change of the thickness or the like of cover glass can be optionally controlled, and to provide an optical observation device using the system. SOLUTION: The optical system is disposed on the image side of the objective lens, and a lens group L1 nearest to an object side has negative refractive power and a movable lens group G1 includes a doublet consisting of a positive lens and a negative lens. The spherical aberration is compensated by moving the movable lens group in the direction of an optical axis AX.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spherical aberration correcting optical system, and more particularly to a spherical aberration correcting optical system which is inserted on the image side of an objective lens and responds to changes in the thickness and refractive index of a parallel plane between the object and the objective lens. The present invention relates to an optical system, an optical observation device, and the like that correct a generated spherical aberration by moving some lens groups in an optical axis direction.

[0002]

2. Description of the Related Art A microscope objective lens for biological observation and the like is designed so that the thickness and the refractive index of a cover glass or a glass petri dish on a specimen surface are constant. Therefore, when the thickness or the refractive index of the cover glass or the like changes, spherical aberration or the like occurs, thereby deteriorating the imaging performance and significantly deteriorating the image contrast. In addition, since the microscope objective lens for metal observation for observing the surface of the semiconductor IC is observed without using a cover glass or the like, it is designed without considering the thickness of the glass. However, an actual IC sample or the like may have a glass surface for surface protection, and in such a case, spherical aberration occurs as in the case of the biological observation, and good observation cannot be performed.

Further, even in an immersion microscope objective lens using oil or the like, if the refractive index of water, oil, or the like changes, spherical aberration similarly occurs, and good observation cannot be performed. For this reason, conventionally, a mechanism (a so-called correction ring) for correcting aberration fluctuation by changing a lens interval in an objective lens according to a spherical aberration generated due to a thickness of a cover glass or the like is known. As such a microscope objective lens, an objective lens described in JP-B-60-205521 and JP-B-60-247613 has been proposed.

[0004]

However, in the conventional method, in order to move a part of the lens group in the objective lens, it is necessary to widen the air gap before and after the moving group. The degree of freedom was reduced, which was a major constraint. For this reason, it has often been difficult to sufficiently improve the basic performance of the objective lens. In addition, since a mechanism for moving the lens must be provided in the objective lens, the objective lens itself becomes too large, and there is a problem that it is inconvenient to handle. Furthermore, by using an objective lens that is not designed for observation by inserting a cover glass between the observation object and the objective lens,
When it is desired to observe a specimen on which a cover glass is mounted, for example, the contrast of the observed image is reduced due to spherical aberration or the like due to the thickness of the cover glass, and it has been impossible to perform good observation.

The present invention has been made in view of such a situation, and is inserted behind an existing objective lens (on the image side) to freely control the amount of spherical aberration caused by a change in the thickness of a cover glass or the like. It is an object of the present invention to provide an optical system and an optical observation device that can be controlled at a high speed.

[0006]

In order to solve the above-mentioned problems, the present invention is directed to an object lens which is inserted on the image side of an objective lens, a lens unit closest to the object side has a negative refractive power, and a positive lens and a negative lens. And a movable lens group including a cemented lens for correcting spherical aberration by moving the movable lens group in the optical axis direction. In such a configuration, the refractive power of the cemented surface in the cemented lens is
It can be either positive or negative.

More preferably, the refractive index satisfies the following conditional expressions (1) and (1) .vertline. (Nn-Np) /r1.vertline.> 0.01. Here, r1 indicates the radius of curvature of the joint surface, Np indicates the refractive index of the positive lens, and Nn indicates the refractive index of the negative lens.

Conditional expression (1) defines an appropriate degree of contribution of the cemented surface of the movable lens group to spherical aberration. If the value is below the lower limit of the expression (1), it becomes difficult to sufficiently correct spherical aberration. According to the features of the present invention, unlike the correction ring mechanism incorporated in the conventional objective lens, the spherical aberration correction optical system can be handled as an optical system separate from the existing optical system. That is, the spherical aberration correcting optical system according to the present invention is detachable from the objective lens. Further, the present invention includes a state in which the spherical aberration correction optical system is inserted in the optical path, that is, a state in which the spherical aberration correction optical system is fixed, in addition to the case where the optical path is detachable.

Then, between the objective lens and the revolver,
Alternatively, a spherical aberration correction optical system (hereinafter, referred to as an “adapter”) is inserted somewhere between the revolver and the objective image, and a part of the lens group in the adapter is moved in the optical axis direction, thereby forming a cover glass. It can be adjusted with an arbitrary correction amount of spherical aberration generated due to a change in thickness or the like.

FIG. 1 is a diagram showing the principle of the present invention. When the movable lens group G1 moves, for example, from (a) to (a ′) in the optical path where light emitted from one point of the object converges or diverges, the incident height of the light beam on the joint surface S changes from H to H ′. And change. Thereby, the correction amount of the spherical aberration is changed. When the adapter according to the present invention is applied between the first objective lens and the second objective lens for infinity correction, since the light flux between the first and second objective lenses is parallel, even if the movable lens group is moved as it is. The incident height of the light beam on the lens surface is constant, and the spherical aberration does not change.

Therefore, the light flux is inclined by adding a lens group having a refractive power (power) closer to the first objective lens side than the movable lens group, so that the movable lens group has a spherical aberration as shown in FIG. A function capable of variably controlling the correction amount can be provided.

The power of the cemented surface in the cemented lens is not limited to a negative refractive power, but a lens having a positive refractive power can also be manufactured. When the joining surface S moves in the optical path where light converges or diverges, the incident height H of the light beam on the joining surface S changes and the spherical aberration generation amount changes regardless of the power of the joining surface. In addition, when changing the sign of the power of the joint surface, the direction of the amount of spherical aberration can be maintained by reversing the direction of movement of the movable part.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, numerical embodiments of the present invention will be described with reference to the accompanying drawings.

(First Embodiment) FIG. 2 shows a lens configuration of an adapter according to a first embodiment. The adapter includes, in order from the object side, a lens group L1 having a negative refractive power, a movable group G1 composed of a junction of a positive lens and a negative lens, and movable in the optical axis AX direction, and a lens group having a positive refractive power. L2,
L3 having a negative refractive power. FIG. 3 shows a lens configuration when the adapter is used for a microscope objective lens for infinite system correction. In this embodiment, the first objective lens has a focal length f = 10 mm, the second objective lens has f = 200 mm, and the magnification of the entire system is 20 times (numerical aperture NA =
The microscope objective lens for infinity correction of 0.75) is used. Table 1 below lists the optical specifications of the microscope objective before the adapter is inserted. In the table, r (i) is the radius of curvature of the i-th lens surface in order from the object side, d is the surface interval, and n (d) and V (d) are d of glass of the i-th lens in order from the object side. The refractive index and Abbe number for the line (λ = 587.6 nm). The numerical value 0.0 in the lens data indicates a plane, and d0 indicates a working distance. These symbols are the same in other tables.

In Table 1, the cover glass covers the first to second surfaces, the first objective lens covers the third to eighteenth surfaces, the second objective lens covers the nineteenth to twenty-fourth surfaces, and the second cover lens.
From the fifth surface to the twenty-sixth surface, lens barrel prisms are shown.

[0016]

[Table 1]

The first objective lens has a cover glass thickness t =
It is designed for 0.17 mm, and its spherical aberration diagram is shown in FIG. In all the aberration diagrams below, the C line is λ = 656.28 nm, and the d line is λ = 587.
56 nm, F line λ = 486.13 nm, g line λ = 4
35.84 nm. Here, the air gap between the first objective lens and the second objective lens is 100 m.
m. Next, when the cover glass thickness is t = 0.2
FIG. 4B shows an aberration diagram at the time of 2 mm. When the spherical aberration is t = 0.17 mm (FIG. 4A),
It can be seen that large spherical aberration occurs.

Next, Table 2 below shows optical data when the adapter according to the first embodiment is inserted into the microscope objective lens. In Table 2, the cover glass is provided from the first surface to the second surface, the first objective lens is provided from the third surface to the 18th surface, the adapter is provided from the 19th to 28th surfaces, and the adapter is provided from the 29th to 34th surfaces. The second objective lens, the third from the 35th surface
Lens prisms are shown on each of the six surfaces.

[0019]

[Table 2]

FIG. 4 shows aberration diagrams when the cover glass thickness t = 0.17 mm and t = 0.22 mm when the adapter of the first embodiment is inserted between the first objective lens and the second objective lens. These are shown in (c) and (d), respectively. As described above, the thickness of the cover glass is changed from t = 0.17 mm to t = 0.2.
When it changes to 2 mm, spherical aberration etc. occur greatly,
As is clear from the aberration diagrams in FIGS. 4C and 4D,
It can be seen that the spherical aberration is dramatically corrected by inserting the adapter of this embodiment and moving it to an appropriate position.

(Second Embodiment) FIG. 5 is a diagram showing a configuration of an adapter according to a second embodiment. In order from the object side, a lens unit L1 having a positive refractive power and an optical axis A
This is a five-group adapter composed of a movable group G1 movable in the X direction, a lens group L2 having a negative refractive power, and a lens group L3 having a positive refractive power. The feature of this embodiment is that an aspherical surface is introduced. An adapter using an aspheric surface has a large spherical aberration correction capability. Further, it is difficult to correct spherical aberration for all of a plurality of optical systems having different back apertures with a spherical adapter. On the other hand, an adapter using an aspherical surface can satisfactorily correct spherical aberration for such a plurality of optical systems.

The adapter according to the present embodiment has NA = 1.
It is used for 30 or more oil immersion objective lenses. For example, when observing a specimen such as a living cell at a high magnification in a living state, it is desired to use water instead of oil.
However, an oil immersion objective lens generates an enormous amount of spherical aberration when water is used instead of oil. Therefore,
In such a case, observation is difficult. This embodiment has been made in view of the above problem, and similarly to the above-described first embodiment, it is inserted between the first objective lens and the second objective lens, and water when observing a biological specimen or the like is observed. Corrects spherical aberration caused by layers. Further, in this embodiment, it is possible to correct spherical aberration for both the 60 × objective lens and the 40 × objective lens.

FIG. 6 shows a lens configuration when such an adapter is used for a microscope objective lens for infinite system correction. In this embodiment, the focal length f = 3.3 as the first objective lens.
mm, a microscope objective lens of f = 200 mm, a magnification of the whole system of 60 times (numerical aperture NA = 1.3), an infinite system correction, was used as a second objective lens. In this example, spherical aberration that occurs when water is used instead of oil to seal the sample is corrected. Table 3 below shows the specifications of the adapter of this embodiment, and Table 4 shows its specifications. The aspheric surface is represented by the following equation.

[0024]

X = cy^Two/ ｛1+ (1-κc)^Twoy^Two)^1/2｝ + C
2 ・ y^Two+ C4 · y^Four+ C6 · y ⁶+ C8 · y⁸+ C10 ・
y^Ten+ C12 · y¹²+ C14 · y¹⁴

Where y is the height from the optical axis, x is the amount of sag, c is the radius of curvature, κ is the cone coefficient, and C2, C4... Here, the sag amount x is
It refers to the amount of displacement of the radius of curvature r from the reference plane in the optical axis direction at a height Y from the optical axis.

[0026]

[Table 3] Distance from object = 75 mm Field of view = 25 When used for a plan apo 60 × objective lens NA: 1.30 (reference time) 1.05 (for water layer) Water layer: 100 μm planful When used for all 40x objective lens Corresponding NA: 1.05 (standard time) 1.05 (for water layer) Water layer: 100 μm

[0027]

[Table 4] (Lens data) Surface rdn (d) 1) 15.62997 1.90000 1.4342500 2) -171.87226 1.76909 1 3) -361.11971 0.90000 1.4342500 4) 12.37328 1.20000 1.6727000 5) 18.92332 4.47557 1 6) -15.33351 0.85000 1.6200400 7) 28.57843 4.56333 1 8) 140.00000 1.84201 1.5182300 9) -16.61358 1 (Aspherical surface) Surface κ C2 C4 C6 C8 2) 1.0000 0.00000 -9.62061 × 10 ^-6 -1.30894 × 10 ^-07 1.73152 × 10 ^-7 C10 C12 C14 -7.44408 × 10 ^-9 1.00711 × 10 ^-10 1.93479 × 10 ^-21 κ C2 C4 C6 C8 3) 1.0000 0.00000 -1.23028 × 10 ^-6 -6.66367 × 10 ^-7 2.27993 × 10 ^-7 C10 C12 C14 -9.07959 × 10 ^-9 1.14423 × 10 ^-10 4.39274 × 10 ^-21 (variable interval data) Objective lens Water layer d0 d1 d2 Evaluation NA 60X None 0.215 0.46 5.78 1.30 60X 100μm 0.052 4.68 1.56 1.05 40X None 0.197 0.40 5.84 1.05 40X 100μm 0.049 1.77 4.47 1.05

Table 5 shows lens data when the adapter is applied to a 60 × objective lens, and Table 6 shows lens data when the adapter is applied to a 40 × objective lens. In Table 5, the cover glass, the layer of water and the oil are on the 0th to 3rd surfaces, and the 1st is on the 4th to 25th surfaces.
Objective lens, adapter from 26th to 34th surface,
The 35th to 40th surfaces indicate the second objective lens, and the 41st to 42nd surfaces indicate the lens barrel prism. Table 6
, The cover glass, water and oil layers from the 0th surface to the 3rd surface, the first objective lens from the 4th to 27th surfaces, the adapter from the 28th to 36th surfaces, and the 37th to 37th surfaces. The second objective lens up to the 42nd surface, the 4th
Up to four surfaces indicate a lens barrel prism.

[0029]

[Table 5]

[0030]

[Table 6] Here, d0 indicates the thickness of the oil layer, and dw indicates the thickness of the water layer.

In Tables 5 and 6, a water layer is arranged on the second surface so that ray tracing can be easily performed. However, in an actual microscope, the water layer is first (the 0th surface). ), And the 0th and 1st planes in Tables 5 and 6 fall down to the 1st and 2nd planes.

FIG. 7 is a spherical aberration diagram when the present adapter is applied to a 60 × objective lens. 7 (a) shows a state where no adapter is used when no water layer is present, FIG. 7 (b) shows a state where no adapter is used when a water layer is present, and FIG. Each of the figures shows a state where an adapter is used when a water layer is present. As is apparent from the figure, even when water is used instead of oil, it is understood that the spherical aberration is favorably corrected by using this adapter. FIG. 8 is a spherical aberration diagram when the present adapter is applied to a 40 × objective lens. 8A shows a state where no adapter is used when no water layer is present, and FIG. 8B shows a state where no adapter is used when there is a water layer.
(C) shows a state where an adapter is used when a water layer is present. As is apparent from the figure, even when water is used instead of oil, it is understood that the spherical aberration is favorably corrected by using this adapter.

In the above embodiment, the case where water is used instead of oil has been described, but the present invention is not limited to this case. For example, in an oil immersion objective lens, even when the refractive index of the oil changes due to a change in the oil temperature and spherical aberration occurs, the present adapter can be applied. In the above embodiment, the negative lens and the positive lens are cemented. However, as long as chromatic aberration is not taken into consideration, a single aspherical lens may be used.

(Third Embodiment) FIG. 9 is a diagram showing a schematic configuration of a microscope system according to a third embodiment. The light from the halogen lamp HL is transmitted through the collector lens L4 and the adiabatic filter F1, and is transmitted through the filter F2 for obtaining almost perfect white light. Next, the light passes through the diffusion plate D, and the field stop F
After the field of view is limited by S, the optical path is almost 9
Folded 0 degrees. Then, the light passes through the field lens FL and is focused on the condenser lens CL. Further, after passing through the aperture stop and limiting the brightness, the light passes through the objective lens OL. On the observer side of the objective lens OL,
The spherical aberration correction optical system AD having the same configuration as that of each of the above embodiments can be attached to and detached from the optical path in the revolver by an attachment / detachment mechanism (not shown). Finally, the light passes through the eyepiece lens EP through the lens barrel prism, and the sample image is observed.

In the present system, spherical aberration caused by, for example, changing the thickness of the cover glass near the specimen (not shown) can be easily corrected by the spherical aberration correcting optical system AD. Further, as described above, the spherical aberration correction optical system AD may be configured to be fixed in the optical path without being detachable.

The present invention can take various configurations without being limited to the above-described embodiments without departing from the spirit thereof. For this reason, it is not limited to a microscope system,
It goes without saying that the present invention can be applied to other optical observation devices.

[0037]

As described above, according to the present invention,
It is possible to provide a spherical aberration correction optical system capable of satisfactorily correcting various aberrations, particularly spherical aberration, with respect to a change (variation) in the thickness of a transparent parallel plane plate disposed on the object side. Further, in the optical observation apparatus provided with the above-mentioned spherical aberration correcting optical system, since various aberrations, especially spherical aberration, are satisfactorily corrected, good observation can always be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an optical path diagram in which an adapter according to the present invention corrects spherical aberration.

FIG. 2 is a diagram illustrating a lens configuration of the adapter according to the first embodiment.

FIG. 3 is a diagram showing a lens configuration when the adapter according to the first embodiment is used for a microscope objective lens.

FIG. 4 is a spherical aberration diagram of the adapter according to the first example.

FIG. 5 is a diagram illustrating a lens configuration of an adapter according to a second example.

FIG. 6 is a diagram showing a lens configuration when the adapter according to the second embodiment is used for a microscope objective lens.

FIG. 7 is a spherical aberration diagram when the adapter according to the second example is used for a 60 × objective lens.

FIG. 8 is a spherical aberration diagram when the adapter according to the second example is used for a 40 × objective lens.

FIG. 9 is a diagram of a microscope system according to a third embodiment.

[Explanation of symbols]

 L1 to L3 Each lens component G1 Movable group AX Optical axis S Joint surface HL Halogen lamp L4 Collector lens F1 Adiabatic filter F2 Filter D Diffusion plate FS Field stop M Reflector FS Field lens CL Condenser lens AS Aperture stop OL Objective lens AD Adapter P Barrel prism EP eyepiece

Claims (5)

[Claims] 1. A movable lens group inserted on the image side of an objective lens, wherein a lens group closest to an object has a negative refractive power, and includes a movable lens group including a cemented lens of a positive lens and a negative lens. A spherical aberration correcting optical system wherein the group moves in the optical axis direction to correct spherical aberration. 2. A spherical aberration correcting optical device comprising an objective lens and a spherical aberration correcting optical system having a movable lens group including a cemented lens of a positive lens and a negative lens, wherein the spherical aberration correcting optical system comprises: A spherical aberration correcting optical device which is detachably attached to the image side of the objective lens, wherein the lens group closest to the object side has negative refractive power, and corrects spherical aberration by moving in the optical axis direction. . 3. A spherical aberration correcting optical system comprising a movable lens group having an aspherical lens inserted on the image side of an objective lens, and correcting a spherical aberration by moving in a direction of an optical axis. 4. The spherical aberration correcting optical system according to claim 3, wherein said movable lens group includes a cemented lens of a positive lens and a negative lens. 5. An optical observation apparatus comprising the spherical aberration correcting optical system according to claim 1, 3 or 4, or the spherical aberration correcting optical apparatus according to claim 2.