JP2002341249A - Immersion microscope objective lens - Google Patents

Abstract

(57) [Summary] An immersion system having a large numerical aperture and capable of satisfactorily correcting fluctuations in various aberrations caused by a change in a refractive index due to a temperature of an immersion liquid or a change in a thickness of a cover glass. A microscope objective is provided. SOLUTION: In order from an object side, a front lens group Gf including a plano-convex lens and having a positive refractive power and a rear lens group Gr having a negative refractive power are provided on the rear side of the front lens group Gf. An immersion microscope objective lens for correcting aberration variation by relatively moving the lens group Gr in the optical axis direction and changing the air gap between the front lens group Gf and the rear lens group Gr, wherein the front lens Let the focal length of the group Gf be f
f, when the total length of the rear lens group Gr is dr, the focal length of the entire immersion microscope objective is F, and the total length of the immersion microscope objective is D, the following conditions are satisfied. (1) 0.4 <dr / D <0.6 (2) 0.3 <F / ff <0.6

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a change in the refractive index of an immersion liquid with temperature and a change (variation) in the thickness of a cover glass.
The present invention relates to an immersion microscope objective lens capable of correcting fluctuations of various aberrations caused by the above.

[0002]

2. Description of the Related Art Some immersion type objective lenses are provided with a mechanism capable of correcting aberration fluctuations called a so-called correction ring. In general, most of immersion microscope objective lenses having a correction ring use water as an immersion liquid. The reason is that there is a large difference between the refractive index of water and the refractive index of the cover glass, and the state of spherical aberration varies depending on the thickness of the cover glass.

On the other hand, in the case of an oil immersion microscope objective lens, unlike water, the refractive index of oil is close to that of a cover glass. Therefore, there is little need to provide a mechanism such as a correction ring.

However, with recent diversification of microscope inspection methods and improvement in required performance, there has been a demand for an oil immersion microscope objective lens having an aberration correcting mechanism for various causes of performance deterioration. Is growing. The first factor that causes deterioration of the performance of the microscope objective lens is a change in spherical aberration due to a change in oil temperature. For example, a standard microscope observation is performed at a temperature of about 23 ° C. However, in the case of ecological cells and the like, the specimen may be observed with the temperature of the sample raised to about 37 ° C., which is close to the body temperature. For this reason, the standard observation state (23 ° C.) is 1
Observation is performed at a high temperature near 0 ° C. The change rate of the refractive index according to the temperature of the oil is about −400 × 10 ⁻⁶ /.
° C. Therefore, even with a temperature change of about 10 ° C.,
The refractive index of oil changes significantly compared to water.
For this reason, if the temperature changes by 10 ° C. when oil is used, the state of aberration will be greatly affected. Further, in the case of an objective lens having a high numerical aperture, a large variation in the variation in the thickness of the cover glass may also cause a large performance degradation.

[0005] Japanese Patent Application Laid-Open Nos. Hei 6-281864 and Hei 7
No. 230038, JP-A-9-258107 and the like. However, these are all water immersion microscope objective lenses having a numerical aperture of about 1.15 to 1.2.
Thus, to date, oil immersion microscope objectives,
There is no disclosure of a lens having a numerical aperture exceeding 1.35.

The present invention has been made in view of the above-mentioned problems, and has a large numerical aperture, and is capable of suppressing fluctuations in various aberrations caused by a change in a refractive index due to a temperature of an immersion liquid or a change in a thickness of a cover glass. It is an object of the present invention to provide an immersion microscope objective lens that can be corrected to a minimum.

[0007]

In order to solve the above-mentioned problems, the present invention includes a plano-convex lens in order from the object side,
The front lens group Gr includes a front lens group Gf having a positive refractive power and a rear lens group Gr having a negative refractive power. The rear lens group Gr is relatively moved in the optical axis direction with respect to the front lens group Gf. An immersion microscope objective lens that corrects aberration variation by changing an air gap between the front lens group Gf and the rear lens group Gr, wherein the focal length of the front lens group Gf is ff, When the total length of the rear lens group Gr is dr, the focal length of the entire immersion microscope objective is F, and the total length of the immersion microscope objective is D, the following conditions are satisfied. An immersion microscope objective lens is provided.

(1) 0.4 <dr / D <0.6 (2) 0.3 <F / ff <0.6

In a preferred aspect of the present invention, the front lens group Gf includes a cemented lens of a plano-convex lens component having a flat surface facing the object side and a meniscus lens component having a convex surface facing the image side. The radius of curvature of the convex surface of the component is rf, and the d-line (58
When the refractive index with respect to (7.6 nm) is defined as nf, the following condition is satisfied: (3) 0.55 <| nf / rf | <0.65.

In a preferred aspect of the present invention, in the rear lens group Gr, the radius of curvature of the cemented surface of the cemented lens closest to the object side is rr, and the d-line of the negative (concave) lens component constituting the cemented lens (587.6 nm) with a refractive index of nrn, and the positive (convex) lens component of the cemented lens with a d-line (587.6 nm) with a refractive index of nr.
When each of p is satisfied, the following condition is satisfied: (4) 0.15 <F / rr <0.35 (5) 0.15 <nrn−nrp <0.25

As described above, the immersion microscope objective according to the present invention includes, in order from the object side, a plano-convex lens, a front lens group Gf having a positive refractive power, and a front lens group Gf. Rear lens group Gr having a negative refractive power capable of relatively moving the interval in the optical axis direction
It is constituted by.

The front lens group Gf has the positive refractive power and converts a divergent light beam from the object plane into a convergent light beam. The cemented surface rr closest to the object side of the rear lens group Gr has a negative refractive power, and generates a positive spherical aberration as the incident light beam moves away from the optical axis. The height of the convergent light flux emitted from the front lens group Gf also changes from the optical axis when the rear lens group Gr is relatively incident on each surface by moving in the optical axis direction. Thereby, the state of the spherical aberration can be changed, and the fluctuation of the spherical aberration caused by the temperature or the like can be corrected.

More specifically, for example, when the temperature of the immersion liquid (oil) increases, the refractive index decreases, and negative spherical aberration occurs. Therefore, the rear lens group G
In the case where r is a system in which spherical aberration is excessively corrected, when the rear lens unit Gr is moved closer to the optical axis direction with respect to the front lens unit Gf, the height of a light beam incident on each surface becomes relatively high, and Spherical aberration increases. Thereby, it is possible to cancel spherical aberration caused by a change in the temperature of the immersion liquid, and prevent the imaging performance from deteriorating.

Next, the above conditional expressions will be described. Conditional expression (1) defines the total length of the movable group. In a microscope objective lens with a high numerical aperture, the eccentricity of the lens may greatly deteriorate the imaging performance. If the lower limit of conditional expression (1) is not reached, the total length of the movable group will be shorter than the total length of the microscope objective lens. For this reason, a long fitting length of the sliding portion cannot be ensured, which is disadvantageous for rotation (tilt) with respect to the optical axis. Conversely, when the value exceeds the upper limit of conditional expression (1), the portion where the air gap is variable becomes closer to the object side,
It is more likely that the light flux is a strong divergent light. For this reason,
The fluctuation of the spherical aberration becomes too sensitive, and it becomes difficult to appropriately correct the spherical aberration.

The conditional expression (2) satisfies the following.
Stipulates an appropriate refractive power. As described above, the front lens group Gf has a function of converting a light beam from an object into convergent light. When the light beam emitted from the front lens group Gf is close to parallel light, the height of the light beam at the joint surface rr does not change when the rear lens group Gr is moved in the optical axis direction. For this reason,
The spherical aberration cannot be corrected. Conditional expression (2)
When the value is below the lower limit, the refractive power of the front lens group Gf becomes small, so that the light beam cannot be sufficiently bent. For this reason, the light emitted from the front lens group Gf becomes nearly parallel. As a result, spherical aberration cannot be corrected. Conversely, when the value exceeds the upper limit of conditional expression (2), the refractive power of the front lens group Gf increases. For this reason, the inclination of the light beam emitted from the front lens group Gf becomes steep. As a result, the imaging performance tends to deteriorate with respect to the eccentricity (shift) in the direction perpendicular to the optical axis of the movable group.

The conditional expression (3) satisfies the following condition.
Is related to the radius of curvature of the convex surface of the cemented plano-convex lens closest to the object side. When the value exceeds the upper limit of conditional expression (3),
The refractive power of the convex surface increases. As a result, the Petzval sum increases and the flatness of the image surface deteriorates. Also,
Difficulty also increases in workability of the lens. Conversely, when the value goes below the lower limit of conditional expression (3), the luminous flux becomes too wide, and the incident height at the subsequent lens group increases. As a result, it becomes difficult to correct spherical aberration, especially for higher-order colors.

Conditional expression (4) is satisfied by the following expression.
The preferred range of the radius of curvature of the first joint surface is determined. At the first cemented surface of the rear lens group Gr, the light beam converted to the convergent light beam is still at a relatively high stage of the incident height. If the upper limit of conditional expression (4) is exceeded, the refractive power of the cemented surface will increase,
When this group is moved, the chromatic spherical aberration varies greatly. Conversely, when the value goes below the lower limit of conditional expression (4), the contribution of chromatic aberration correction decreases, and the angle of incidence on the surface increases. For this reason, adverse effects such as an imbalance in spherical aberration and coma aberration are caused.

The conditional expression (5) relates to the bonding surface shown by the conditional expression (4) and defines an appropriate range of the difference in the refractive index of the glass material forming the bonding surface. If the value exceeds the upper limit value of the conditional expression (5) or falls below the lower limit value, it becomes difficult to satisfy the condition defined by the conditional expression (4). If the condition (4) is not satisfied while the condition defined by the condition (5) is not satisfied, it is not possible to maintain a proper refractive power of the cemented surface as a correction group, and the variation in aberrations is reduced. The correction ability decreases.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. (First Embodiment) FIG. 1 is a diagram showing a lens configuration of a microscope objective lens according to a first embodiment. A front lens group Gf including a plano-convex lens and having a positive refractive power in order from the object side
And a lens configuration including a rear lens group Gr having a negative refractive power capable of correcting the distance between the front lens group Gf and the optical axis direction and correcting aberration fluctuation. I have. By changing the air interval d11, it is possible to cope with aberration fluctuations such as a change in the temperature of the immersion liquid.

Table 1 shows the specification values of the first embodiment. In the overall specifications, F is the focal length of the microscope objective,
A. denotes the numerical aperture, β denotes the magnification, and d0 denotes the distance on the optical axis from the object plane to the first plane. In the lens data, r is the radius of curvature of each lens surface, d is the surface interval, nd, ν
d is the d-line (587.6n) of the glass material used for each lens.
m) and the Abbe number. The refractive index of air is 1.0000, and the description is omitted. Further, “∞” in the r column indicates a plane.

The cover glass used has nd = 1.52216 and vd = 58.8 d = 0.16 mm.

Further, the temperature of the immersion liquid (oil) used is 30 ° C.
Are listed below. In this embodiment, the aberration can be corrected within a range of ± 7 ° C. Here, the rate of change of the refractive index of the oil according to the temperature is calculated as −400 × 10 ⁻⁶ / ° C.

Nd = 1.51299 nC = 1.50931 nF = 1.52192 ng = 1.30230

The same reference numerals as in the specification table of this embodiment are used in all the embodiments. In general, the unit of the focal length, the radius of curvature, the surface interval, and other lengths in the specification table are “m”.
m ”is used, but the optical system is not limited to this, since the same optical performance can be obtained even if the optical system is enlarged or reduced proportionally.

[0025]

[Table 1]

FIGS. 2A, 2B and 2C are respectively spherical aberration diagrams of the present embodiment. 2A shows the spherical aberration when the temperature of the immersion liquid is 23 ° C., FIG. 2B shows the spherical aberration when the temperature of the immersion liquid is 30 ° C., and FIG. In each spherical aberration diagram, the solid line is the d line (587.6 nm), the broken line is the C line (656.3 nm), and the dashed line is the F line (486.nm).
1 nm), and the two-dot chain line indicates the g line (435.8 nm). As is clear from the figure, the temperature was 23 ° C to 37 ° C.
It can be seen that the spherical aberration is favorably corrected over ° C.

(Second Embodiment) FIG. 3 is a view showing the arrangement of an immersion microscope objective according to a second embodiment. In order from the object side, a front lens group Gf including a plano-convex lens and having a positive refractive power, and the distance between the front lens group Gf and the front lens group Gf can be relatively moved in the optical axis direction to correct aberration fluctuations. The lens configuration includes a rear lens group Gr having a negative refractive power. By changing the air gap d14, it is possible to cope with aberration fluctuations such as a change in the temperature of the immersion liquid. Table 2 shows the specification values of the present embodiment.

[0028]

[Table 2]

FIGS. 4A, 4B and 4C are respectively spherical aberration diagrams of the present embodiment. 4A shows the spherical aberration when the temperature of the immersion liquid is 23 ° C., FIG. 4B shows the spherical aberration when the temperature of the immersion liquid is 30 ° C., and FIG. As is clear from the figure, it is understood that the spherical aberration is favorably corrected over a range of 23 ° C. to 37 ° C.

Since the immersion microscope objective lens according to each of the above embodiments is a lens of the infinity type correction type, it is used using an imaging lens. The spherical aberration diagrams in the above embodiments are aberrations when combined with an imaging lens whose lens configuration is shown in FIG. Table 3 shows the specification values of the imaging lens.

[0031]

[Table 3]

[0032]

As described above, according to the present invention, the numerical aperture is large, and the variation of various aberrations caused by the change in the refractive index and the thickness of the cover glass due to the temperature of the immersion liquid is excellent. Thus, an immersion microscope objective lens that can be corrected to a minimum can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an immersion microscope objective according to a first embodiment of the present invention.

FIGS. 2A, 2B, and 2C are spherical aberration diagrams of the first embodiment.

FIG. 3 is a sectional view of an immersion microscope objective according to a second embodiment of the present invention.

FIGS. 4A, 4B, and 4C are spherical aberration diagrams of the second embodiment.

FIG. 5 is a cross-sectional view of an imaging lens used with the immersion microscope objective according to the present invention.

[Explanation of symbols]

 Gf Front lens group Gr Rear lens group

Claims (3)

[Claims] 1. In order from the object side, a front lens group Gf including a plano-convex lens and having a positive refractive power and a rear lens group Gr having a negative refractive power are provided. The rear lens group Gr is moved relatively in the optical axis direction, and the front lens group Gf is moved.
An immersion microscope objective lens that corrects aberration fluctuations by changing an air gap between the rear lens unit Gr and the rear lens unit Gr, wherein the focal length of the front lens unit Gf is ff, and the total length of the rear lens unit Gr is dr, wherein the focal length of the entire immersion microscope objective lens system is F, and the total length of the immersion microscope objective lens is D, wherein the following conditions are satisfied: (1) 0.4 <dr / D <0.6 (2) 0.3 <F / ff <0.6 2. The front lens group Gf includes a cemented lens of a plano-convex lens component having a flat surface facing the object side and a meniscus lens component having a convex surface facing the image side, and has a radius of curvature of the convex surface of the meniscus lens component. rf, where nf is the refractive index of the meniscus lens component with respect to the d-line (587.6 nm), and the following condition is satisfied: 0.55 <| nf / rf | <0.65. Item 2. An immersion microscope objective lens according to item 1. 3. In the rear lens unit Gr, the radius of curvature of the cemented surface of the cemented lens closest to the object side is rr, and the d-line (58) of the negative lens component forming the cemented lens
7.6 nm) to nrn, and the d-line (58) of the positive lens component forming the cemented lens.
(4) 0.15 <F / rr <0.35 (5) 0.15 <nrn−nrp <0.25, where nrp is the refractive index for 7.6 nm). 3. The immersion microscope objective lens according to claim 1, wherein