JP2006259548A - Microscope objective lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an immersion system microscope objective lens which can correct aberration caused by the difference in the refractive indexes of a cover glass and a sample. <P>SOLUTION: The objective lens is provided with a first lens group G1, a second lens group G2 and a third lens group G3 which are successively arranged in that order from an object side. The second lens group G2 is placed in a diverging luminous flux and the group G2 can relatively be moved with respect to the first and the third lens groups G1 and G3 along the optical axis. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an objective lens for an immersion microscope that observes or measures an object in a cell.

  In recent years, in the field of biology, studies have been conducted to elucidate the structure and function of cells by observing the movement and activity of molecules in living cells using an optical microscope. Among them, total internal reflection fluorescence microscopy (hereinafter referred to as TIRFM) has attracted attention as an important research tool. In order to perform TIRFM, the illumination light must be totally reflected at the interface between the cover glass and the sample. In order to cause total reflection at the boundary surface, the objective lens used needs to have a high NA. For example, if the refractive index of the cover glass is 1.52 to 1.79 and the refractive index of the intracellular medium is 1.37, the NA of the objective lens needs to be larger than 1.37.

An objective lens having an NA larger than 1.37 is proposed in the following document, for example.
JP-A-6-160721 Japanese Patent Laid-Open No. 7-035983 JP-A-7-230039 Japanese Patent Application Laid-Open No. 7-281097 JP 2000-035541 A JP 2002-148519 A JP 2002-350347 A JP 2003-015046 A JP 2003-021786 A JP 2003-337285 A JP 2004-061589 A JP-T-2004-522185 (priority claim number DE10108796) JP 2002-098903 A JP, 2002-341249, A The objective lens indicated in patent documents 2, patent documents 5, patent documents 6, patent documents 9, and patent documents 10 is an objective lens whose magnification is 60 times and NA is 1.4. .

  In addition, the objective lenses described in Patent Literature 1, Patent Literature 3, Patent Literature 6, Patent Literature 9, and Patent Literature 11 are objective lenses having a magnification of 100 times and an NA of 1.4.

  The objective lens described in Patent Document 8 is an objective lens having a magnification of 59.6 and NA of 1.4, and an objective lens having a magnification of 55.9 and NA of 1.4. A correction lens group that corrects aberrations that occur depending on the glass thickness and aberrations that occur due to temperature changes is provided.

  The objective lens described in Patent Document 14 is an objective lens having a magnification of 60 times and an NA of 1.4, and includes a correction lens group that corrects aberrations due to changes in cover glass thickness and temperature. ing.

  Moreover, the objective lens described in Patent Document 7 is an objective lens having a magnification of 60 times and an NA of 1.45.

  The objective lenses described in Patent Document 7, Patent Document 9, and Patent Document 12 are objective lenses having a magnification of 100 times and an NA of 1.45.

  The objective lens described in Patent Document 7 is an objective lens having a magnification of 100 times and an NA of 1.46.

  The objective lens described in Patent Document 4 is an objective lens optimally designed for oil with nd = 1.78035 and a cover glass with nd = 1.865, with a magnification of 100 times and an NA of 1.65. is there.

  In addition, the objective lens described in Patent Document 13 is optimally designed for an oil of nd = 1.80911 and a cover glass of nd = 1.804, and has a magnification of 100 and an NA of 1.65 to 1.67. Objective lens.

  These objective lenses can satisfactorily observe a sample in the vicinity of the cover glass surface by using oil or cover glass suitable for the design. Moreover, if it judges only from NA, there is a possibility that it can be used for TIRFM.

  However, the objective lenses of Patent Documents 1 to 14 are unsuitable for observing deeper portions (portions separated by 1 μm or more) than the cover glass surface when observing cells. The refractive index of the cover glass is 1.52 to 1.8, whereas the intracellular refractive index is about 1.33 to 1.5. When observing a deeper part of the cell than the cover glass surface, spherical aberration occurs due to the difference in refractive index between the two, and the imaging performance deteriorates. Degradation in imaging performance is more remarkable as the difference in refractive index between the two is greater, and the more the focusing surface to be observed or measured is farther from the cover glass surface.

  For example, FIG. 16 shows spherical aberration when observing a deep part in a cell using the objective lens described in Example 2 of Patent Document 9. In FIG. 16, (a) is a spherical aberration at a focus position 0 mm away from the cover glass surface, (b) is a spherical aberration at a focus position 0.002 mm away, and (c) is a focus position 0.005 mm away. (D) represents spherical aberration at a focus position separated by 0.01 mm. Here, it is assumed that the refractive index of the intracellular medium is 1.38. As can be seen from FIG. 16, the amount of spherical aberration generated increases as the focus surface moves away from the cover glass surface. Further, when the appearance of spherical aberration is observed, it is greatly curved from around 70% of NA. The generation of spherical aberration that is greatly curved from around 70% of NA significantly deteriorates the imaging performance, and satisfactory imaging cannot be obtained.

  The objective lenses of Patent Document 8 and Patent Document 14 have a correction function for correcting aberrations, and this function corrects aberrations due to changes in cover glass thickness and operating temperature. Remarkable aberrations caused by the rate difference cannot be corrected. If an attempt is made to move the correction lens group excessively to correct it, the vicinity of 70% of the spherical aberration swells to the plus side, degrading the imaging performance.

  Of course, when observing a deeper part (several hundred nm or more) than the cover glass surface, TIRFM cannot be used. However, if the biomolecules on the surface of the cover glass can be observed by TIRFM and the intracellular biomolecules separated from the cover glass can be observed with the same apparatus, it can provide a new research means for biological research. It becomes possible.

  An object of the present invention is to provide an immersion microscope objective lens capable of correcting an aberration caused by a difference in refractive index between a cover glass and a sample.

  In the present invention, a sample represented by a living cell (refractive index nd is 1.33 to 1.5) is covered with a cover glass (refractive index nd is 1.4 to 1.6) and an immersion liquid (refractive index nd is 1). .33 to 1.6) is an immersion microscope objective lens for observation or measurement, depending on the aberration caused by the refractive index difference between the sample and the cover glass or the thickness of the sample In order to correct the generated aberration, a moving lens group is provided that is movable along the optical axis placed in the divergent light beam.

  ADVANTAGE OF THE INVENTION According to this invention, the immersion type | system | group microscope objective lens which can correct | amend the aberration which arises due to the refractive index difference of a cover glass and a sample is provided.

  Hereinafter, in describing the embodiments of the present invention, first, the basic configuration of the objective lens of the present invention common to all the embodiments will be described, and then the objective lens of the embodiments of the present invention with reference to the drawings. explain.

  The objective lens of the present invention includes a first lens group having a positive refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power, which are arranged in order from the object side. It has.

  The objective lens of the present invention is an infinitely corrected objective lens, and the objective lens converts a divergent light beam from a sample into a parallel light beam. The first lens group reduces the divergence angle of the divergent light beam incident on the objective lens and transmits it to the second lens group. The second lens group transmits the divergent angle of the divergent light beam that has passed through the first lens group to the third lens group by further reducing the divergence angle. The third lens group converges the loose divergent light beam that has passed through the first lens group and the second lens group into a parallel light beam.

  The second lens group is a moving lens group for correcting spherical aberration, and is movable along the optical axis of the objective lens relative to the first lens group and the third lens group. Further, the second lens group is placed in the divergent light beam. Here, the phrase “the second lens group is placed in the divergent light beam” means that the light beam has a divergence angle with respect to the optical axis both before and after passing through the second lens group.

  In a conventional objective lens, it has been assumed that the moving lens group is not placed in a significantly divergent beam or a significantly convergent beam. The reason is that the amount of spherical aberration generated depending on the thickness of the cover glass is small and the correction amount is small.

  As described above, when there is a difference in refractive index between the sample and the cover glass, significant spherical aberration occurs. The refractive index of the medium in the living cell is 1.33 to 1.5, and in most cases is about 1.4 or less. The cover glass has a refractive index of 1.52 to 1.79. For this reason, a refractive index difference arises between a sample and a cover glass, and remarkable spherical aberration occurs. In addition, higher-order spherical aberration occurs. For this reason, the moving lens group in the conventional objective lens has insufficient correction amount or cannot completely correct higher-order spherical aberration.

  On the other hand, in the objective lens of the present invention, the second lens group which is a moving lens group is arranged in a significantly divergent light beam, that is, a place where the angle between the light beam and the optical axis is large. For this reason, it is possible to obtain a larger correction action than in the prior art.

  For example, when the second lens group is moved to the first lens group side, the air gap d3 between the first lens group and the second lens group is decreased, and the air gap d4 between the second lens group and the third lens group. Will increase. The phenomenon of air spacing d3 generates large positive spherical aberration, and the increase of air spacing d4 also generates large positive spherical aberration. By combining each positive spherical aberration, a larger positive spherical aberration can be obtained. Thereby, the remarkable negative spherical aberration which generate | occur | produced by the refractive index difference of a sample and a cover glass can be canceled. On the other hand, in order to cancel a significant positive spherical aberration, the second lens group may be moved to the third lens group side.

  Aberration correction by moving the second lens group, which is a moving lens group, not only corrects spherical aberration caused by the refractive index difference between the sample and the cover glass, but also aberrations that depend on the thickness of the sample. The present invention may be applied to correction of spherical aberration that occurs depending on the thickness of a conventional cover glass, and correction of spherical aberration that occurs due to temperature changes between the sample and the immersion liquid.

  The first lens group includes a cemented lens including a plano-convex lens having a plane facing the object side and a meniscus lens having a concave surface facing the object side in order from the object side. The cemented surface of this cemented lens has negative refractive power and corrects the Petzval sum. The convex surface on the image side of the meniscus lens of the cemented lens of the first lens group satisfies the non-play condition (aplanatic condition) and suppresses the occurrence of spherical aberration and coma. As described above, since the first lens group includes the cemented lens, it is possible to satisfactorily correct the aberration even when the NA is higher than 1.37.

  The second lens group has at least one positive lens. This positive lens preferably has a strong convex surface on the image side, and may be a meniscus lens having a concave surface facing the object side or a plano-convex lens having a flat surface facing the object side.

  The third lens group has at least three cemented lenses, and spherical aberration and chromatic aberration are corrected by these cemented lenses. In order to correct chromatic aberration more satisfactorily, the third lens group desirably includes at least one three-piece cemented lens. Further, in order to correct Petzval sum and coma aberration more satisfactorily, it is desirable that a lens having a strong negative refractive power is placed near the image side. The lens having a strong negative refractive power is preferably a biconcave lens, a plano-concave lens, a meniscus lens, or a cemented meniscus lens having a strong concave surface facing the image side.

The objective lens according to the present invention preferably has the following conditional expression: 4 <f (G2) / f <10 (1)
More preferably, the following conditional expression 4 <f (G2) / f <8 (2)
Is satisfied. Here, f (G2) is the focal length of the second lens group, and f is the focal length of the entire objective lens system.

  Conditional expression (1) defines the power of the second lens group, and is intended to give the second lens group a relatively strong power. If the conditional expression (1) is satisfied, a large correcting action can be obtained. If the lower limit 4 of conditional expression (1) is not reached, the power of the second lens group becomes too strong, and various aberrations occurring in the second lens group cannot be corrected by other lens groups, and the entire lens system can be corrected. It becomes difficult to maintain the magnification. If the upper limit value 10 of conditional expression (1) is exceeded, sufficient correction action cannot be obtained. If the conditional expression (2) is further satisfied, the design is further balanced.

In the objective lens according to the present invention, preferably, the following conditional expression 0.1 <θ1 / θ2 <0.4 (3)
More preferably, the following conditional expression 0.15 <θ1 / θ2 <0.3 (4)
Is satisfied. Here, θ1 is an angle formed between the optical beam and the maximum NA marginal ray incident on the moving lens group, and θ2 is an angle formed between the optical axis and the maximum NA marginal ray emitted from the moving lens unit.

  Conditional expression (3) defines the balance of the lens powers of the first lens group, the second lens group, and the third lens group by defining the light rays that enter and exit the second lens group. Yes. Below the lower limit of 0.1, the combined lens power of the first lens group and the second lens group becomes too strong, making it difficult to correct aberrations in the third lens group. If the upper limit of 0.4 is exceeded, the lens power of the first lens group or the second lens group becomes too weak, the lens outer diameter of the third lens group becomes large, and the lens processing becomes difficult. The overall length of the entire lens tends to be long, which is undesirable in the system. Therefore, if the conditional expression (3) is satisfied, the design has a good balance of various aberrations, workability, and overall length. Further, if the conditional expression (4) is satisfied, the balance between various aberrations, workability, and the overall length becomes a better design.

  The objective lens of the present invention preferably has a numerical aperture greater than 1.37, more preferably 1.4 or higher.

  In the medium in a living cell, the refractive index nd of the cell fluid is about 1.37 to 1.38. If the numerical aperture of the objective lens is larger than 1.37, it can be used in TIRFM in most cases. In addition, since the NA is large, it is easy to obtain an image of weak fluorescence emitted from the sample, and high resolution can be obtained. When NA is below 1.37, the objects that can be observed by TIRFM are considerably limited, and it becomes difficult to obtain an image of weak fluorescence. When NA is 1.37, the refractive index nd of the immersion liquid needs to be 1.37 or more. When NA is 1.4, the refractive index nd of the immersion liquid needs to be 1.4 or more. If the numerical aperture of the objective lens is 1.4 or more, it can be used in TIRFM for almost all intracellular media (refractive index: 1.33 to 1.4).

[First embodiment]
As shown in FIG. 1, the objective lens according to the first embodiment of the present invention includes a first lens group G1, a second lens group (correction lens group) G2, and a third lens group G3 arranged in order from the object side. It has. The first lens group G1 includes, in order from the object side, a cemented lens including a plano-convex lens L1 having a plane facing the object side and a meniscus lens L2 having a concave surface facing the object side. The second lens group G2 includes a meniscus lens L3 having a concave surface directed toward the object side, and is movable along the optical axis. The third lens group G3 includes a three-piece cemented lens including a positive lens L4, a negative lens L5, and a positive lens L6, a positive lens L7, a negative lens L8, a positive lens L9, and a negative lens L10. A cemented lens composed of a positive lens L11 and a negative lens L12, a cemented lens composed of a positive lens L13 and a negative lens L14, a negative lens L15 having a concave surface facing the image side, and an object side It is composed of a double-junction lens composed of a negative lens L16 and a positive lens L17 having a concave surface.

The data of the objective lens of the first embodiment is as follows.

The variable amount (unit: mm) of the lens surface interval for correcting the aberration is as follows. d1 is the distance from the focus position to the cover glass surface. Cells are composed of various media (nd = 1.33 to 1.5), but here, cell fluid (about nd = 1.38) was assumed. Of course, even with a medium other than nd = 1.38, practical imaging performance can be obtained by moving the correction lens group. d2 is WD and is filled with oil. d3 and d4 are variable amounts of the distance before and after the second lens group G2.

  The cover glass used in the first embodiment has a thickness of 0.17 mm, nd = 1.51637, and νd = 64.2. The oil has nd = 1.511 and νd = 43.1. In this embodiment, it is assumed that a sample at 37 ° C. is observed, and nd and νd at 37 ° C. are used for the cover glass and oil close to the sample.

  Here, in the lens data, r is a radius of curvature (unit: mm) of each lens surface, d is an interval (unit: mm) between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is d of each lens. Abbe number on the line. In addition, f is a focal length (unit: mm), f (G1) is a focal length (unit: mm) of the first lens group G1, f (G2) is a focal length (unit: mm) of the second lens group G2, and f (G3). ) Is the focal length (unit: mm) of the third lens group G3, θ1 is the angle (unit: °) between the marginal ray of the maximum NA incident on the second lens group G2 and the optical axis, and θ2 is from the second lens group G2. An angle (unit degree) formed by the marginal ray having the maximum NA emitted and the optical axis, β is a magnification, NA is a numerical aperture, and WD is a working distance (unit mm). Θ1 and θ2 are defined as a divergent light beam when the value is positive and as a convergent light beam when the value is negative.

[Second Embodiment]
As shown in FIG. 2, the objective lens according to the second embodiment of the present invention includes a first lens group G1, a second lens group (correction lens group) G2, and a third lens group G3 arranged in order from the object side. It has. The first lens group G1 includes, in order from the object side, a cemented lens including a plano-convex lens L1 having a plane facing the object side and a meniscus lens L2 having a concave surface facing the object side. The second lens group G2 includes a meniscus lens L3 having a concave surface directed toward the object side, and is movable along the optical axis. The third lens group G3 includes a three-piece cemented lens including a positive lens L4, a negative lens L5, and a positive lens L6, a positive lens L7, a negative lens L8, a positive lens L9, and a negative lens L10. A cemented lens composed of a positive lens L11 and a negative lens L12, a cemented lens composed of a positive lens L13 and a negative lens L14, a negative lens L15 having a concave surface facing the image side, and an object side It is composed of a double-junction lens composed of a negative lens L16 and a positive lens L17 having a concave surface.

The data of the objective lens of the second embodiment is as follows.

The variable amount (unit: mm) of the lens surface interval for correcting the aberration is as follows. d1 is the distance from the focus position to the cover glass surface. Cells are composed of various media (nd = 1.33 to 1.5), but here, cell fluid (about nd = 1.38) was assumed. Of course, even with a medium other than nd = 1.38, practical imaging performance can be obtained by moving the correction lens group. d2 is WD and is filled with oil. d3 and d4 are variable amounts of the distance before and after the second lens group G2.

  The cover glass used in the second embodiment has a thickness of 0.17 mm, nd = 1.48748, and νd = 70.2. The oil has nd = 1.43792 and νd = 56.4. In this embodiment, it is assumed that a sample at 37 ° C. is observed, and nd and νd at 37 ° C. are used for the cover glass and oil close to the sample.

  Here, in the lens data, r is a radius of curvature (unit: mm) of each lens surface, d is an interval (unit: mm) between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is d of each lens. Abbe number on the line. In addition, f is a focal length (unit: mm), f (G1) is a focal length (unit: mm) of the first lens group G1, f (G2) is a focal length (unit: mm) of the second lens group G2, and f (G3). ) Is the focal length (in mm) of the third lens group G3, θ1 is the angle (unit °) between the marginal ray of the maximum NA incident on the second lens group G2 and the optical axis, and θ2 is from the second lens group G2. An angle (unit degree) formed by the marginal ray having the maximum NA emitted and the optical axis, β is a magnification, NA is a numerical aperture, and WD is a working distance (unit mm). Θ1 and θ2 are defined as a divergent light beam when the value is positive and as a convergent light beam when the value is negative.

[Third embodiment]
As shown in FIG. 3, the objective lens according to the third embodiment of the present invention includes a first lens group G1, a second lens group (correction lens group) G2, and a third lens group G3 arranged in order from the object side. It has. The first lens group G1 includes, in order from the object side, a cemented lens including a plano-convex lens L1 having a plane facing the object side and a meniscus lens L2 having a concave surface facing the object side. The second lens group G2 includes a meniscus lens L3 having a concave surface directed toward the object side, and is movable along the optical axis. The third lens group G3 includes a three-piece cemented lens including a positive lens L4, a negative lens L5, and a positive lens L6, a positive lens L7, a negative lens L8, a positive lens L9, and a negative lens L10. A cemented lens composed of a positive lens L11 and a negative lens L12, a cemented lens composed of a positive lens L13 and a negative lens L14, a negative lens L15 having a concave surface facing the image side, and an object side It is composed of a double-junction lens composed of a negative lens L16 and a positive lens L17 having a concave surface.

The data of the objective lens of the third embodiment is as follows.

The variable amount (unit: mm) of the lens surface interval for correcting the aberration is as follows. d1 is the distance from the focus position to the cover glass surface. Cells are composed of various media (nd = 1.33 to 1.5), but here, cell fluid (about nd = 1.38) was assumed. Of course, even with a medium other than nd = 1.38, practical imaging performance can be obtained by moving the correction lens group. d2 is WD and is filled with oil. d3 and d4 are variable amounts of the distance before and after the second lens group G2.

  The cover glass used in the third embodiment has a thickness of 0.17 mm, nd = 1.45861, and νd = 67.7. The oil has nd = 1.43792 and νd = 56.4. In this embodiment, it is assumed that a sample at 37 ° C. is observed, and nd and νd at 37 ° C. are used for the cover glass and oil close to the sample.

  Here, in the lens data, r is a radius of curvature (unit: mm) of each lens surface, d is an interval (unit: mm) between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is d of each lens. Abbe number on the line. In addition, f is a focal length (unit: mm), f (G1) is a focal length (unit: mm) of the first lens group G1, f (G2) is a focal length (unit: mm) of the second lens group G2, and f (G3). ) Is the focal length (unit: mm) of the third lens group G3, θ1 is the angle (unit °) between the marginal ray of the maximum NA incident on the second lens group G2 and the optical axis, and θ2 is from the second lens group G2. An angle (unit degree) formed by the marginal ray having the maximum NA emitted and the optical axis, β is a magnification, NA is a numerical aperture, and WD is a working distance (unit mm). Θ1 and θ2 are defined as a divergent light beam when the value is positive and as a convergent light beam when the value is negative.

[Fourth embodiment]
As shown in FIG. 4, the objective lens according to the fourth embodiment of the present invention includes a first lens group G1, a second lens group (correction lens group) G2, and a third lens group G3 arranged in order from the object side. It has. The first lens group G1 includes, in order from the object side, a cemented lens including a plano-convex lens L1 having a plane facing the object side and a meniscus lens L2 having a concave surface facing the object side. The second lens group G2 includes a meniscus lens L3 having a concave surface directed toward the object side, and is movable along the optical axis. The third lens group G3 includes a triplet cemented lens including a positive lens L4, a negative lens L5, and a positive lens L6, a triplet cemented lens including a negative lens L7, a positive lens L8, and a negative lens L9, and a positive lens L10. And a double-junction lens composed of a negative lens L11 having a concave surface facing the image side.

The data of the objective lens of the fourth embodiment is as follows.

The variable amount (unit: mm) of the lens surface interval for correcting the aberration is as follows. d1 is the distance from the focus position to the cover glass surface. Cells are composed of various media (nd = 1.33 to 1.5), but here, cell fluid (about nd = 1.38) was assumed. Of course, even with a medium other than nd = 1.38, practical imaging performance can be obtained by moving the correction lens group. d2 is WD and is filled with oil. d3 and d4 are variable amounts of the distance before and after the second lens group G2.

  The cover glass used in the fourth embodiment has a thickness of 0.17 mm, nd = 1.48748, and νd = 70.2. The oil has nd = 1.43792 and νd = 56.4. In this embodiment, it is assumed that a sample at 37 ° C. is observed, and nd and νd at 37 ° C. are used for the cover glass and oil close to the sample.

  Here, in the lens data, r is a radius of curvature (unit: mm) of each lens surface, d is an interval (unit: mm) between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is d of each lens. Abbe number on the line. In addition, f is a focal length (unit: mm), f (G1) is a focal length (unit: mm) of the first lens group G1, f (G2) is a focal length (unit: mm) of the second lens group G2, and f (G3). ) Is the focal length (in mm) of the third lens group G3, θ1 is the angle (unit °) between the marginal ray of the maximum NA incident on the second lens group G2 and the optical axis, and θ2 is from the second lens group G2. An angle (unit degree) formed by the marginal ray having the maximum NA emitted and the optical axis, β is a magnification, NA is a numerical aperture, and WD is a working distance (unit mm). Θ1 and θ2 are defined as a divergent light beam when the value is positive and as a convergent light beam when the value is negative.

[Fifth embodiment]
As shown in FIG. 5, the objective lens according to the fifth embodiment of the present invention includes a first lens group G1, a second lens group (correction lens group) G2, and a third lens group G3 arranged in order from the object side. It has. The first lens group G1 includes, in order from the object side, a cemented lens including a plano-convex lens L1 having a plane facing the object side and a meniscus lens L2 having a concave surface facing the object side. The second lens group G2 includes a meniscus lens L3 having a concave surface facing the object side and a plano-convex lens L4 having a flat surface facing the object side, and is movable along the optical axis. The third lens group G3 includes a three-piece cemented lens including a positive lens L5, a negative lens L6, and a positive lens L7, a positive lens L8, a negative lens L9, a positive lens L10, and a negative lens L11. A double-junction lens comprising a positive lens L12 and a negative lens L13, a negative lens L14 having a tight concave surface on the image side, and a negative lens L15 and a positive lens L16 having a concave surface on the object side It consists of a lens.

The data of the objective lens of the fifth embodiment is as follows.

The variable amount (unit: mm) of the lens surface interval for correcting the aberration is as follows. d1 is the distance from the focus position to the cover glass surface. Cells are composed of various media (nd = 1.33 to 1.5), but here, cell fluid (about nd = 1.38) was assumed. Of course, even with a medium other than nd = 1.38, practical imaging performance can be obtained by moving the correction lens group. d2 is WD and is filled with oil. d3 and d4 are variable amounts of the distance before and after the second lens group G2.

  The cover glass used in the fifth embodiment has a thickness of 0.17 mm, nd = 1.45861, and νd = 67.7. The oil has nd = 1.43792 and νd = 56.4. In this embodiment, it is assumed that a sample at 37 ° C. is observed, and nd and νd at 37 ° C. are used for the cover glass and oil close to the sample.

  Here, in the lens data, r is a radius of curvature (unit: mm) of each lens surface, d is an interval (unit: mm) between the lens surfaces, nd is a refractive index of d-line of each lens, and νd is d of each lens. Abbe number on the line. Further, f is a focal length (unit: mm), f (G1) is a focal length (unit: mm) of the first lens group G1, f (G2) is a focal length (unit: mm) of the second lens group G2, and f (G3). ) Is the focal length (in mm) of the third lens group G3, θ1 is the angle (unit °) between the marginal ray of the maximum NA incident on the second lens group G2 and the optical axis, and θ2 is from the second lens group G2. An angle (unit degree) formed by the marginal ray having the maximum NA emitted and the optical axis, β is a magnification, NA is a numerical aperture, and WD is a working distance (unit mm). Θ1 and θ2 are defined as a divergent light beam when the value is positive and as a convergent light beam when the value is negative.

  Each optical glass used in the first embodiment to the fifth embodiment is selected from optical glasses having excellent transmittance in the ultraviolet region and low autofluorescence, and each embodiment is an objective lens that is optimal for fluorescence observation. It has become. Each optical glass is selected from environmentally friendly glass (lead-free glass), and each embodiment is an objective lens in consideration of the environment.

Each of the first to fifth embodiments is an infinity correction type objective lens in which light emitted from the objective lens becomes a parallel light beam, and does not form an image by itself. Therefore, for example, the lens data shown in Table 16 is used in combination with the imaging lens (focal length 180) having the lens cross section shown in FIG.

  In this lens data, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, nd is the refractive index of the d-line of each lens, and νd is the Abbe number of the d-line of each lens.

  In this case, the interval between the objective lens and the imaging lens of the first to fifth embodiments may be any position between 50 mm and 170 mm. FIGS. 6 and 7 show aberration diagrams of the objective lens of the first embodiment when the distance is 120 mm, FIGS. 8 and 9 show aberration diagrams of the objective lens of the second embodiment, and FIG. 10 and 11 are aberration diagrams of the lenses, FIGS. 12 and 13 are aberration diagrams of the objective lens of the fourth embodiment, and FIGS. 14 and 15 are aberration diagrams of the objective lens of the fifth embodiment. In these drawings, (a) is a spherical aberration at d1 = 0, (b) is a spherical aberration at d1 = 0.002, (c) is a spherical aberration at d1 = 0.005, (d) is d1. = Spherical aberration at 0.01, (e) shows sine condition violation amount, (f) shows astigmatism, (g) shows distortion, and (h) shows coma. When observing the inside of a cell, light rays exceeding 1.38 do not contribute to image formation. Therefore, in (b), (c), and (d), the NA is slightly reduced for display.

  As can be seen by comparing the aberration diagrams of the first to fifth embodiments and the aberration diagram of the conventional example of FIG. 16, the objective lens of the embodiment of the present invention is a sample having a low refractive index as in a cell. It is possible to satisfactorily correct spherical aberration that occurs when observing or measuring the above. Therefore, practical imaging performance can be obtained even when the inside of a cell is observed or measured.

It is lens sectional drawing of the objective lens of 1st embodiment of this invention. It is a lens sectional view of the objective lens of a second embodiment of the present invention. It is lens sectional drawing of the objective lens of 3rd embodiment of this invention. It is lens sectional drawing of the objective lens of 4th embodiment of this invention. It is lens sectional drawing of the objective lens of 5th embodiment of this invention. It is an aberration diagram of the objective lens of the first embodiment of the present invention. It is an aberration diagram of the objective lens of the first embodiment of the present invention. It is an aberration diagram of the objective lens of the second embodiment of the present invention. It is an aberration diagram of the objective lens of the second embodiment of the present invention. It is an aberration diagram of the objective lens of the third embodiment of the present invention. It is an aberration diagram of the objective lens of the third embodiment of the present invention. It is an aberration diagram of the objective lens of the fourth embodiment of the present invention. It is an aberration diagram of the objective lens of the fourth embodiment of the present invention. It is an aberration diagram of the objective lens of the fifth embodiment of the present invention. It is an aberration diagram of the objective lens of the fifth embodiment of the present invention. It is an aberration diagram of the objective lens disclosed in Japanese Patent Application Laid-Open No. 2003-021786. 6 is a lens cross-sectional view of an imaging lens combined with the objective lens of FIGS.

Explanation of symbols

G1 ... first lens group, G2 ... second lens group, G3 ... third lens group.

Claims (11)

  A sample represented by a living cell (refractive index nd is 1.33 to 1.5) is covered with a cover glass (refractive index nd is 1.4 to 1.6) and an immersion liquid (refractive index nd is 1.33 to 1). .6) an immersion microscope objective lens for observation or measurement through, wherein aberrations caused by a difference in refractive index between the sample and the cover glass or aberrations depending on the thickness of the sample An immersion microscope objective lens comprising a moving lens group movable along an optical axis placed in a divergent light beam for correction.   In order from the object side, a first lens group having a positive refractive power having a cemented lens composed of a plano-convex lens having a plane facing the object side and a meniscus lens having a concave surface facing the object side, is placed in a divergent light beam, Consists of a second lens group having at least one positive lens and positive refractive power, and a third lens group having at least three cemented lenses and having positive refractive power for converting a divergent light beam into a parallel light beam An immersion microscope characterized in that the second lens group is movable along the optical axis relative to the first lens group and the third lens group in order to correct aberrations. Objective lens. The immersion microscope objective lens according to claim 2, wherein the following conditional expression 4 <f (G2) / f <10 (1)
(Where f (G2) is the focal length of the second lens group, and f is the focal length of the entire objective lens system)
An immersion microscope objective lens characterized by satisfying The immersion microscope objective lens according to claim 3, wherein the following conditional expression 4 <f (G2) / f <8 (2)
An immersion microscope objective lens characterized by satisfying   A sample represented by a living cell (refractive index nd is 1.33 to 1.5) is covered with a cover glass (refractive index nd is 1.4 to 1.6) and an immersion liquid (refractive index nd is 1.33 to 1). .6) An immersion microscope objective lens for observation or measurement through a positive lens having, in order from the object side, a cemented lens consisting of a plano-convex lens having a plane facing the object side and a meniscus lens having a concave surface facing the object side. A first lens group having a refractive power of 2; a second lens group having at least one positive lens and having a positive refractive power; and at least three cemented lenses. A third lens group having a positive refractive power for conversion into a parallel light beam, and the second lens group has an aberration caused by a difference in refractive index between the sample and the cover glass or a thickness of the sample. For the correction of aberrations generated depending on Immersion microscope objective characterized in that it is movable along the relative optical axis with respect to the third lens group and first lens group. 6. The immersion microscope objective lens according to claim 5, wherein the following conditional expression 4 <f (G2) / f <10 (1)
(Where f (G2) is the focal length of the second lens group, and f is the focal length of the entire objective lens system)
An immersion microscope objective lens characterized by satisfying The immersion microscope objective lens according to claim 6, wherein the following conditional expression 4 <f (G2) / f <8 (2)
An immersion microscope objective lens characterized by satisfying The immersion microscope objective lens according to any one of claims 1 to 7, wherein the following conditional expression: 0.1 <θ1 / θ2 <0.4 (3)
(Where θ1 is the angle formed by the marginal ray of maximum NA incident on the moving lens group and the optical axis, and θ2 is the angle formed by the marginal ray of maximum NA emitted from the moving lens group and the optical axis. )
An immersion microscope objective lens characterized by satisfying The immersion microscope objective lens according to claim 8, wherein the following conditional expression: 0.15 <θ1 / θ2 <0.3 (4)
An immersion microscope objective lens characterized by satisfying   10. The immersion microscope objective lens according to claim 1, wherein a refractive index nd of the immersion liquid is 1.37 or more and a numerical aperture is larger than 1.37. Immersion microscope objective lens.   The immersion microscope objective lens according to claim 10, wherein the refractive index nd of the immersion liquid is 1.4 or more and the numerical aperture is larger than 1.4. .

Images