JP5281873B2 - Immersion objective optical system with an intermediate imaging plane and designed at infinity - Google Patents

Description

  The present invention relates to a microscope objective unit used for applications such as elucidation of cell functions and imaging, and relates to a microscope objective unit suitable for observing a mammal, particularly an animal alive.

Conventionally, a dye or fluorescent marker is attached to a specific molecule, tissue, cell, etc., and this is observed with a fluorescence microscope or a confocal laser scanning microscope to observe the behavior of molecules in living cells and tissues. Has been done.
Molecular behavior in the living state of a mammal such as a mouse may be different from that of a cultured cell, and observation of living tissues and cells is performed while the individual is alive (in vivo) (for example, , See Patent Document 1).

JP 2006-119300 A

  Microscopes such as conventional laser scanning confocal microscopes do not assume that various organs of small experimental animals such as rats and mice are observed in a living state (in vivo). However, when observing the inside of a living organism, the conventional microscope objective lens has a large outer diameter. However, since the invasiveness is high when the living body is greatly opened, long-time observation is impossible.

  That is, in order to observe various organs of these experimental small animals, it is necessary to incise the epidermis and muscle tissue or to pierce the skull to expose the internal organs. Since the size is larger than that of an experimental small animal or an observation target, when observing an internal organ or the like, it is necessary to make a large incision or open a large hole in the epidermis or muscle tissue.

  On the other hand, although the optical system of Patent Document 1 with a reduced tip diameter is disclosed, when observing the deep part of a relatively small organ such as the brain of a mouse, it is still highly invasive and considering damage to the living body. There is an inconvenience that observation in a normal state is difficult. Furthermore, in this optical system, there is a problem that the S / N is not good because the numerical aperture is small and the resolution is lowered when observing by multiphoton excitation, and the detection light is weak.

  The present invention has been made in view of the above-described circumstances, and remains alive in mammalian tissues including experimental small animals, living tissues such as muscles, or various organs such as heart and liver, particularly brain tissues. It is possible to provide a liquid immersion small-diameter objective optical system having an intermediate image plane with an infinite design for use in multiphoton excitation, while enabling low-invasive observation over a relatively long period of time. It is aimed.

In order to achieve the above object, the present invention provides the following means.
The present invention includes, in order from the object side, a first group having positive refractive power, a second group having positive refractive power, a third group having negative refractive power, a fourth group having positive refractive power, and a fifth group having positive refractive power. The first group includes a plano-convex lens having a convex surface directed toward the image side , converts a divergent light beam from the object surface into a light beam having a smaller divergent property, and the second group has a lens surface closest to the object side. a cemented lens having a convex surface on the object side, the third group, most lens surface on the image side is a cemented lens having a concave surface on the image side, the fourth group disposed closest to the object side A lens having a convex surface facing the image side and a lens disposed closest to the image side and having a convex surface facing the object side, the diverging light beam from the third group being a convergent light beam. was converted to the fifth group, convex and concave lenses are bonded, and include a cemented lens wherein the bonding surface is a negative refractive power It is larger than the beam diameter of light flux diameter in until the fourth group from the first group in the bonding surface, an intermediate image plane between the fourth group at infinity design and the fifth group An immersion small-diameter objective optical system is provided.

  According to the present invention, in the first group having positive refracting power, the most object side becomes a substantially flat surface, so that bubbles can be prevented from entering therebetween. Further, by including a plano-convex lens having a convex surface facing the image surface side, it is possible to reduce the occurrence of spherical aberration and coma aberration close to the aplanatic condition.

  In the second group having positive refracting power, when the lens surface closest to the object side has a convex surface facing the object side, spherical aberration and coma aberration are greatly generated. Can be prevented, and the lens outer diameter can be reduced.

  In the third group of negative refractive power, the Petzval sum can be reduced without increasing the ray height in the third group by the lens surface closest to the image surface facing the concave surface toward the image surface side. And curvature of field can be corrected.

  In the fourth group having positive refractive power, the image surface side lens surface of the lens disposed closest to the object side has a convex surface facing the image surface side, so that it approaches the aplanatic condition. The divergent light can be made substantially convergent without increasing the generation of spherical aberration and coma. Furthermore, the object-side lens surface of the lens arranged closest to the image side has a convex surface directed toward the object side, so that it is close to the aplanatic condition, and convergent light can be obtained without increasing the generation of spherical aberration and coma aberration. it can.

In the fifth group having positive refractive power, in order to convert divergent light into parallel light, the whole group has positive refractive power, and includes a cemented lens having a negative refractive power joint surface. It is possible to correct spherical aberration and chromatic aberration that could not be corrected by the group.
In addition, by providing the intermediate imaging plane in the liquid immersion objective optical system, the exit pupil position on the image side can be arranged outside the lens.

  Therefore, according to the immersion infinity objective optical system having an intermediate image plane in the infinity design according to the present invention configured as described above, the outer diameter is thin, the total length is long, and various aberrations are well corrected. Thus, it is possible to realize an immersion small-diameter objective optical system having an intermediate imaging plane with an infinity design suitable for in vivo observation with a high numerical aperture that can also be used for multiphoton excitation.

In the said invention, it is preferable to satisfy the following conditional expressions (1).
_{(1) 0.15 <F 12 /} (L 13 · NA) <0.25
Where F ₁₂ is the focal length of the first group to the second group, L ₁₃ is the optical axis distance from the object plane to the most image side surface of the third group, and NA is an intermediate at an infinite design. This is the object-side numerical aperture of an immersion small-diameter objective optical system having an image plane.

Condition (1) is the focal length F ₁₂ decreases the combined second group from the first group falls below 0.15, the refractive power of the first group and the second group becomes strong, the spherical aberration is largely generated However, the correction becomes difficult and the object-side NA becomes large, so that the light beam heights of the first group and the second group become large, so that the diameter cannot be reduced. Further, L ₁₃ is long, narrow portion of the immersion small-diameter objective optical system becomes longer, since the field of view vignetting occurs off-axis light is such narrow, is disadvantageous.

Conversely, if the conditional expression (1) exceeds 0.25, the refractive power focal length F ₁₂ from the first group the combined second group becomes large decreases. As a result, divergent light from the object cannot be converged, and the light heights of the first group and the second group become large, which is inconvenient. In addition, since the object-side numerical aperture NA is small, inconveniences such as a reduction in resolution occur. Further, since the L ₁₃ is shortened, it shortens the length of the small-diameter portion of the immersion small-diameter objective optical system, when observing a small animal biological deep, such as a mouse, to observe more deep minimally invasive Becomes difficult.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (2) to (5).
_{(2) 12 <F 5 /} F 12 <14
_{(3) 1.7 <φ 5 /} φ 12 <2.5
_{(4) 1.75 <n 12 <} 1.90
(5) 80 <ν ₅ <95

Where F ₁₂ is the focal length of the first group to the second group, F ₅ is the focal length of the fifth group, and φ ₁₂ is the smallest lens diameter among the lenses of the first group and the second group. , Φ ₅ is the largest lens diameter among the lenses of the fifth group, n ₁₂ is the largest refractive index (d line) of the lenses of the first group and the second group, and ν ₅ is the negative of the fifth group. It is the Abbe number (d line) of the convex lens of the cemented lens having the cemented surface of refractive power.

If conditional expression (2) is below 12, the focal length F ₁₂ from the first group the combined second group becomes large, the refractive power of the first and second group decreases, converge the diverging light from the object This is inconvenient because the beam height in the first and second groups becomes large.
Conversely, if the conditional expression (2) exceeds 14, the focal length F ₅ of the fifth group becomes large, which is inconvenient because divergent light from the fourth group cannot be converted into convergent light. the refractive power of the first and second group focal length F ₁₂ obtained by combining the second group becomes smaller increases from a large spherical aberration occurs inconvenience in the first and second group.

When conditional expression (3) is below 1.7, because the largest lens diameter phi ₅ of the fifth lens group becomes small, various aberrations including such as a spherical aberration generated in the fourth group from the first group together it becomes difficult to correct, for the smallest lens diameter phi ₁₂ of the first group and the second lens group becomes large, which is undesirable can not be thin.

Conversely, if the conditional expression (3) exceeds 2.5, the largest lens diameter phi ₅ is increased out of the fifth lens group, the smallest lens diameter of the first group and the second lens group phi ₁₂ since smaller, but in terms of aberration correction it is advantageous, when the lens diameter phi ₁₂ is too small off-axis light in such vignetting, since the inconvenience, such as the object-side numerical aperture NA and field of view becomes smaller It is preferable to keep it at an appropriate value.

When the conditional expression (4) is less than 1.75, the refractive powers of the first and second groups become small, the diverging light from the object cannot be converged, the light beam height becomes high and the diameter cannot be reduced. Therefore, it is inconvenient.
On the other hand, if conditional expression (4) exceeds 1.90, the radius of curvature of the first and second lens groups becomes large, which is inconvenient because the correction of spherical aberration becomes excessive.

When the conditional expression (5) is less than 80, the concave lens of the normal cemented lens uses a flint glass material with high refraction and high dispersion, so that the difference in Abbe number on the cemented surface becomes small and occurs in the first group to the fourth group. It becomes difficult to correct the chromatic aberration.
On the other hand, if conditional expression (5) exceeds 95, the correction of chromatic aberration becomes excessive, which is inconvenient.

  According to the present invention, living tissue of mammalian cells including small experimental animals, muscles and other biological tissues, or various organs such as the heart and liver, particularly brain tissues, remain alive for a relatively long period of time. This makes it possible to observe the image and to use it for multiphoton excitation.

[First embodiment]
FIG. 1 shows a lens configuration of a first example of the present invention, and an embodiment thereof will be described below.
The immersion small-diameter objective optical system 1 having an intermediate image plane with an infinity design according to the present embodiment includes a lens having a substantially flat object-side lens surface disposed on the most object side, and an image plane side. A first lens unit G1 having a positive refractive power including a plano-convex lens having a convex surface facing the lens, a second lens group G2 having a positive refractive power having the lens surface closest to the object side facing the convex surface toward the object side, and a lens surface closest to the image surface side. The third lens group G3 having negative refractive power with the concave surface facing the image surface side, the image surface side lens surface of the lens disposed closest to the object side is directed convex toward the image surface side, and further disposed closest to the image side A fourth lens group G4 having a positive refractive power, wherein the object side lens surface of the lens has a convex surface facing the object side, and a positive refractive power including a cemented lens of a convex lens having a negative refractive power cemented surface and a concave lens. The fifth lens group G5 is composed of an intermediate image plane disposed between the fourth lens group G4 and the fifth lens group G5.

More specifically, the first lens group G1 includes a parallel flat plate L1, and a planoconvex lens L2 having a convex surface facing the image surface and a refractive index of d-line of 1.883, and has positive refractive power.
The second lens group G2 includes a cemented lens in which a biconvex lens L3 having a convex surface facing the object side and a biconcave lens L4 are cemented, and has positive refractive power.

The third lens group G3 includes a cemented lens obtained by cementing a biconvex lens L5 and a biconcave lens L6 having an image-side surface facing the concave surface toward the image surface side, and has negative refractive power.
In the fourth lens group G4, the image side lens surface of the biconvex lens L7 disposed closest to the object side has the convex surface facing the image side, and the object side lens surface of the planoconvex lens L8 disposed closest to the image side is the object side. The convex surface is directed to the surface, and has positive refractive power as a whole.

The fifth lens group G5 includes a biconvex lens L9, a negative refractive power meniscus lens L10 having a concave surface directed toward the image side, and a planoconvex lens L11 having a positive refractive power toward the object side, and a cemented surface having a negative refractive power. And a positive refractive power plano-convex lens L12 having a convex surface facing the image side and a negative refractive power meniscus lens L13 having a concave surface facing the object side, and a cemented surface having a negative refractive power. As a whole, it has positive refractive power, and the Abbe number of the plano-convex lens L11 and the plano-convex lens L12 is 94.9.
The position of the exit pupil on the image side is arranged 1.3 mm from the meniscus lens L13.

In the present embodiment, the lenses L1 to L13 are configured to satisfy the following conditional expressions (1) to (5).
_{(1) 0.15 <F 12 /} (L 13 · NA) <0.25
_{(2) 12 <F 5 /} F 12 <14
_{(3) 1.7 <φ 5 /} φ 12 <2.5
_{(4) 1.75 <n 12 <} 1.90
(5) 80 <ν ₅ <95

Here, F ₁₂ is the focal length of the first group G 1 to the second group G 2, L ₁₃ is the optical axis distance from the object plane to the most image side of the third group G 3, and NA is an infinite design. in object-side numerical aperture of the immersion small-diameter objective optical system 1 having an intermediate image plane, _{F 5} is the focal length of the fifth lens group G5, phi _12, the first lens group G1 and the second lens group G2 lens L1~ smallest lens diameter of L4, phi ₅ is the largest lens diameter of the fifth lens group G5 lens _{L9~L13, n 12} is the largest among the first group G1 and the lens L1~L4 of the second group G2 Refractive index (d-line), ν ₅ is the Abbe number (d-line) of the plano-convex lens L11 of the cemented lens having the cemented surface having the negative refractive power of the fifth group G5.

  Table 1 shows lens data of the immersion small-diameter objective optical system 1 according to the present example, and FIG. 3 shows aberration diagrams of the present example.

For symbols in the table,
r: radius of curvature, d: spacing, nd: refractive index (d line), νd: Abbe number (d line)
It has become.

In the present embodiment, each value in the conditional expressions (1) to (5) is as follows.
F ₁₂ = 0.418
F ₅ = 5.50
L ₁₃ = 3.70
NA = 0.62
φ ₁₂ = 0.80
φ ₅ = 1.80
n ₁₂ = 1.883
ν ₅ = 94.9
(1) F ₁₂ / (L ₁₃ · NA) = 0.18
(2) F ₅ / F ₁₂ = 13.2
(3) φ ₅ / φ ₁₂ = 2.25
(4) n ₁₂ = 1.883
(5) ν ₅ = 94.9

  In the immersion small-diameter objective optical system 1 according to this example, the lens diameters of the lenses L1 to L6 are 0.8 mm, the lens diameters of the lenses L7 and L8 are 1.2 mm, and the lens diameters of the lenses L9 to L13 are 1. The front end portion from the lens L1 to the lens L6 is composed of only a lens having a very small diameter.

  For this reason, it is suitable for in vivo observation of a deep inside of a small experimental animal such as a mouse for a relatively long time with minimal invasiveness. In addition, the present embodiment corrects aberrations up to the near-infrared region, and the near-infrared light can be used to observe not only the surface of the sample but also the inside of the living body relatively without being affected by scattering. Furthermore, since the object-side numerical aperture is relatively large, it can also be used for multiphoton excitation.

[Second Embodiment]
FIG. 2 shows a lens configuration of a second example of the present invention, and an embodiment thereof will be described below.
In addition, the same code | symbol shall be attached | subjected about the structure which is common in 1st Example.
The immersion small-diameter objective optical system 1 having an intermediate image plane with an infinity design according to the present embodiment includes a lens having a substantially flat object-side lens surface disposed on the most object side, and an image plane side. A first lens unit G1 having a positive refractive power including a plano-convex lens having a convex surface facing the lens, a second lens group G2 having a positive refractive power having the lens surface closest to the object side facing the convex surface toward the object side, and a lens surface closest to the image surface side. The third lens group G3 having negative refractive power with the concave surface facing the image surface side, the image surface side lens surface of the lens disposed closest to the object side is directed convex toward the image surface side, and further disposed closest to the image side Fourth lens group G4 having a positive refractive power in which the object-side lens surface of the lens has a convex surface facing the object side, and a fifth lens group G5 having a positive refractive power including a cemented lens of a convex lens having a cemented surface having a negative refractive power and a concave lens. , And an intermediate imaging plane disposed between the fourth group G4 and the fifth group G5.

More specifically, the first group G1 includes a parallel flat plate L31 and a plano-convex lens L32 having a convex surface facing the image surface and a refractive index of d-line of 1.883, and has positive refractive power.
The second group G2 includes a cemented lens in which a biconvex lens L33 having a convex surface facing the object side and a plano-concave lens L34 are cemented, and has positive refractive power.

The third group G3 includes a cemented lens in which a biconvex lens L35 and a biconcave lens L36 having an image-side surface facing a concave surface on the image surface side and has negative refractive power.
In the fourth group G4, the image side lens surface of the plano-convex lens L37 disposed closest to the object side has the convex surface facing the image side, and the object side lens surface of the plano-convex lens L38 disposed closest to the image side is directed to the object side. It has a convex surface and has positive refractive power as a whole.

The fifth group G5 includes a positive refractive power meniscus lens L39 having a convex surface facing the image side, a positive refractive power plano-convex lens L40 having a convex surface facing the image side, and a negative refractive power meniscus having a convex surface facing the image side. The lens L41 is cemented and the cemented surface is composed of a cemented lens having a negative refractive power, and has a positive refractive power as a whole. The Abbe number of the plano-convex lens L40 is 94.9.
The position of the exit pupil on the image side is arranged on the 4.8 mm image side from the meniscus lens L41.

In the present embodiment, the lenses L31 to L41 are configured to satisfy the following conditional expressions (1) to (5).
_{(1) 0.15 <F 12 /} (L 13 · NA) <0.25
_{(2) 12 <F 5 /} F 12 <14
_{(3) 1.7 <φ 5 /} φ 12 <2.5
_{(4) 1.75 <n 12 <} 1.90
(5) 80 <ν ₅ <95

Here, F ₁₂ is the focal length of the first group G 1 to the second group G 2, L ₁₃ is the optical axis distance from the object plane to the most image side of the third group G 3, and NA is an infinite design. in object-side numerical aperture of the immersion small-diameter objective optical system 1 having an intermediate image plane, _{F 5} is the focal length of the fifth lens group G5, phi _12, the first lens group G1 and the second lens group G2 lens L31~ smallest lens diameter of L34, phi ₅ is the largest lens diameter of the lens L39~L41 the fifth group _{G5, n 12} is the greatest refractive among lenses L31~L34 the first lens group G1 and the second lens group G2 The ratio (d line), ν ₅ is the Abbe number (d line) of the convex lens L40 of the cemented lens having the cemented surface having the negative refractive power of the fifth group G5.

  Table 2 shows lens data of the immersion small-diameter objective optical system 1 according to the present example, and FIG. 4 shows aberration diagrams of the present example.

The immersion small-diameter objective optical system 1 according to the present embodiment is basically the same as the first embodiment, but corrects distortion aberration and reduces image distortion than the first embodiment. It is an example.
Furthermore, also in this embodiment, the lens diameters of the lenses L31 to L36 are 0.8 mm, the lens diameters of the lenses L37 and L38 are 1.2 mm, and the tip portion is composed of only a lens having a very small diameter. .

  For this reason, it is suitable for in vivo observation of a deep inside of a small experimental animal such as a mouse for a relatively long time with minimal invasiveness. In addition, aberrations are corrected up to the near-infrared region, and not only the surface of the sample but also the inside of the living body can be observed relatively unaffected by scattering, and the object-side numerical aperture can be Since it is relatively large, it can also be used for multiphoton excitation.

In the present embodiment, each value in the conditional expressions (1) to (5) is as follows.
F ₁₂ = 0.470
F ₅ = 6.07
L ₁₃ = 3.72
NA = 0.61
φ ₁₂ = 0.80
φ ₅ = 1.60
n ₁₂ = 1.883
ν ₅ = 94.9
(1) F ₁₂ / (L ₁₃ · NA) = 0.20
(2) F ₅ / F ₁₂ = 12.9
(3) φ ₅ / φ ₁₂ = 2.00
(4) n ₁₂ = 1.883
(5) ν ₅ = 94.9

  In both the first and second embodiments, the light emitted to the image side becomes parallel light, so that no image is formed by itself. Therefore, the lens data shown in Table 3 below is used, and the lens data is used in combination with the imaging lens whose lens configuration is shown in FIG.

It is a block diagram of the immersion small diameter objective optical system based on the 1st Example of this invention. It is a block diagram of the immersion small diameter objective optical system which concerns on the 2nd Example of this invention. FIG. 4 is an aberration diagram of the immersion small-diameter objective optical system according to the first example of the present invention. (A) Spherical aberration, (b) Sine condition violation amount, (c) Astigmatism, (d) shows distortion aberration. Represents. FIG. 6 is an aberration diagram of the immersion small-diameter objective optical system according to the second example of the present invention. (A) Spherical aberration, (b) Sine condition violation amount, (c) Astigmatism, (d) Distortion aberration Represents. It is a block diagram which shows an example of an imaging lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid immersion objective optical system G1 1st group G2 2nd group G3 3rd group G4 4th group G5 5th group L1, L31 Parallel flat plate L2, L32 Planoconvex lens L3, L33 Biconvex lens L4 Biconcave lens L5, L35 Both Convex lens L6, L36 Biconcave lens L7 Biconvex lens L8, L38 Planoconvex lens L9 Biconvex lens L10 Meniscus lens (concave lens)
L11 Plano-convex lens L12 Plano-convex lens L13 Meniscus lens L34 Plano-concave lens L37 Plano-convex lens L39 Meniscus lens L40 Plano-convex lens L41 Meniscus lens (concave lens)

Claims (3)

In order from the object side, the first group of positive refractive power, the second group of positive refractive power, the third group of negative refractive power, the fourth group of positive refractive power, and the fifth group of positive refractive power,
The first group includes a plano-convex lens having a convex surface facing the image side, and converts a divergent light beam from the object surface into a light beam having a smaller divergence;
The second group includes a cemented lens in which the lens surface closest to the object side has a convex surface facing the object side,
The third group is composed of a cemented lens in which the lens surface closest to the image side has a concave surface facing the image side,
The fourth group includes a lens arranged closest to the object side and having an image side lens surface having a convex surface facing the image side, and a lens arranged closest to the image side and having the object side lens surface having a convex surface facing the object side, Converting the divergent beam from the third group into a convergent beam,
The fifth group includes a cemented lens in which a convex lens and a concave lens are cemented and the cemented surface has a negative refractive power, and a beam diameter at the cemented surface is larger than a beam diameter between the first group and the fourth group. Is also growing,
An immersion small-diameter objective optical system having an intermediate imaging plane between the fourth group and the fifth group with an infinity design. The immersion small-diameter objective optical system having an intermediate imaging surface with an infinity design according to claim 1, which satisfies the following conditional expression (1).
_{(1) 0.15 <F 12 /} (L 13 · NA) <0.25
However,
F ₁₂ : Focal length of the first group to the second group L ₁₃ : Optical axis distance from the object surface to the image side surface of the third group NA: Object side numerical aperture of the main immersion immersion objective optical system The immersion small-diameter objective optical system having an intermediate image plane with an infinity design according to claim 1 or 2, wherein the following conditional expressions (2) to (5) are satisfied.
_{(2) 12 <F 5 /} F 12 <14
_{(3) 1.7 <φ 5 /} φ 12 <2.5
_{(4) 1.75 <n 12 <} 1.90
(5) 80 <ν ₅ <95
However,
F ₁₂ : Focal length of the first group to the second group F ₅ : Focal length of the fifth group φ ₁₂ : The smallest lens diameter among the lenses of the first group and the second group φ ₅ : of the fifth group Largest lens diameter among lenses n ₁₂ : The largest refractive index (d-line) among the lenses of the first group and the second group
ν ₅ : Abbe number (d line) of the convex lens of the cemented lens having the cemented surface having the negative refractive power of the fifth group

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