JP4504153B2 - Immersion objective optical system - Google Patents

Description

  The present invention relates to an elongated objective high-numerical objective optical system, and more particularly to an immersion objective optical system suitable for being inserted into an animal such as a mammal and observing while 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, thereby observing the behavior of a molecule in a biological cell or tissue. Has been done.
The behavior of molecules in a living state of a mammal such as a mouse may be different from that of a cultured cell, and living tissues and cells are observed while the individual is alive (in vivo).

  When observing the inside of a living individual, since the outer diameter of the objective lens is large in a conventional microscope, it is necessary to open and observe the living body greatly. However, since the invasion is high when the living body is greatly opened, long-term observation is impossible.

Since a general endoscope has a small outer diameter, the invasion to a living body is low. However, since the magnification is low, it is insufficient for observing the behavior of molecules in living tissue or cells.
Although the magnifying endoscope has a high magnification, the numerical aperture (NA) on the object side is low, so that the resolution and brightness are insufficient.

On the other hand, an objective optical system having a large numerical aperture, a small outer diameter, and a relatively long overall length is also disclosed (for example, Patent Document 1). According to the objective optical system disclosed in Patent Document 1, the inside of the living body can be observed with minimal invasiveness by making a small hole in the living body and inserting the optical system through the hole.
US Patent Application Publication No. 2004/0051957

However, in the objective optical system described in Patent Document 1, chromatic aberration is not sufficiently corrected, and when observing with white light or observing fluorescence, the excitation light and the wavelength of fluorescence emitted from the sample However, there is a problem that the resolution is lowered.
In particular, in the case of fluorescence observation using a confocal optical system, there is a problem that the brightness of the detected fluorescence is lowered unless the chromatic aberration is corrected.

  The present invention has been made in view of the above-mentioned circumstances, and has a thin outer diameter, a long overall length, a well-corrected chromatic aberration, a high numerical aperture, and an immersion objective optical suitable for in vivo observation. The purpose is to realize the system.

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 of positive power, a second group of positive power, a third group of negative power, a fourth group of positive power, and a fifth group of positive power. Includes a plano-convex lens L1 having a convex surface facing the image surface side, the most object-side surface is substantially flat, and the second group has the most object-side surface of the second group convex toward the object side. And a lens L3 having a surface closest to the image plane of the second group with a concave surface facing the image plane. The third group includes a biconvex lens L4 and a biconcave lens L5 from the object side. It includes a cemented lens in which, the fourth group includes a positive lens L6 having a convex surface directed toward the object side, the fifth group, saw including at least one cemented lens, the following conditional expression (1) A satisfactory immersion objective optical system is provided.
(1) 0.03 <| F ₁₂ / F ₃ | <0.13
Here, F ₃ is the focal length of the third group, and F ₁₂ is the focal length of the first group to the second group.

  According to the present invention, in the first group of positive power, it is possible to prevent bubbles from entering between them by making the most object side a substantially flat surface. In addition, by including the plano-convex lens L1 with the 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 with positive power, the most object side surface of the second group is the lens L2 having a convex surface facing the object side, and this surface causes large spherical aberration and coma aberration. Instead, the divergence of the light beam can be reduced to prevent the light ray height from becoming higher on the image plane side than the second group. As a result, the lens outer diameter can be reduced.
Further, since the most image side surface of the second group includes the lens L3 with the concave surface facing the image surface side, the light beam is slightly diverged by the concave surface facing the image surface side of the lens L3, and the second group lens. The coma and axial chromatic aberration generated in L2 can be corrected.

  Further, the third group of negative power includes a cemented lens in which the biconvex lens L4 and the biconcave lens L5 are cemented from the object side, so that the light beam slightly diverged by the surface on the image plane side of the lens L3 is a biconvex lens. The light beam is gently converged by the convex surface on the object side of L4. Thereby, it is possible to prevent the height of light rays from increasing in the cemented lens, and to reduce the lens outer diameter.

  Further, spherical aberration generated on the object surface side of the first group, the second group, and the biconvex lens L4 at the cemented surface of the biconvex lens L4 and the biconcave lens L5, and an axis generated by the lens L2 of the first group and the second group. Upper chromatic aberration can be corrected. By diverging the light beam by the concave surface on the image surface side of the biconcave lens L5, it is possible to correct the spherical aberration that has been insufficiently corrected, and further to correct the axial chromatic aberration. Further, coma aberration generated in the lens L2 and the biconvex lens L4 can be corrected on this surface.

  In addition, since the fourth group of positive power includes the positive lens L6 having a convex surface directed toward the object side, the divergent light beam exiting the third group can be made a substantially parallel light beam. By directing the convex surface toward the object side of the fourth group, it is possible to prevent the light beam height from increasing in the positive lens L6 and to reduce the lens outer diameter.

  In the fifth group, positive power is given as a whole in order to collect the light beams that are substantially parallel after passing through the fourth group. At that time, by using a cemented lens in the fifth group, it is possible to correct spherical aberration, axial chromatic aberration, and coma aberration generated in the fourth group on the cemented surface.

  Therefore, according to the immersion objective optical system according to the present invention configured as described above, the outer diameter is narrow, the total length is long, the chromatic aberration is well corrected, and the living object is alive with a high numerical aperture (in An immersion objective optical system suitable for observation in vivo) can be realized.

In the said invention, it is preferable to satisfy the following conditional expressions (1).
(1) 0.03 <| F ₁₂ / F ₃ | <0.13
Here, F ₃ is the focal length of the third group, and F ₁₂ is the focal length of the first group and the second group.
When | F ₁₂ / F ₃ | is 0.03 or less, the Petzval sum increases and the curvature of field increases. When | F ₁₂ / F ₃ | is 0.13 or more, the negative power of the third group becomes too strong, and the positive power of the first group and the second group becomes too weak. In either case, since the light beam diameter is increased, it is necessary to increase the outer diameter of the lens, which causes a problem that the optical system is highly invasive to a living body.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (2).
(2) 0.8 <| β · F ₁₄ / F ₅ | <1.2
Where β is the magnification of the immersion objective optical system, F ₁₄ is the focal length of the first group to the fourth group, and F ₅ is the focal length of the fifth group.
When | β · F ₁₄ / F ₅ | is 0.8 or less, the power between the first group and the fourth group becomes too strong, and the amount of various aberrations increases. Therefore, aberration correction is performed in the fifth group. Becomes difficult. _{Moreover, | β · F 14 / F} 5 | If is less than 1.2, the amount of aberrations because the power is weakened between the first group of the fourth group can be reduced, the luminous flux diameter Therefore, it is necessary to increase the outer diameter of the lens, which causes a problem that the invasion to the living body increases.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (3), (4), (5).
(3) ν ₄ −ν ₅ > 40
(4) 0.12 <n ₅ −n ₄ <0.22
(5) 1.4 <| R _4O / R ₄₅ | <1.9
Where ν ₄ and ν ₅ are respectively the Abbe numbers of the biconvex lens L4 and the biconcave lens L5 with respect to the d line, and n ₄ and n ₅ are the refractive indices of the biconvex lens L4 and the biconcave lens L5 with respect to the d line, R _4O and R ₅ , respectively. Reference numerals ₄₅ denote the radius of curvature of the object side of the biconvex lens L4 and the cemented surface of the biconvex lens L4 and the biconcave lens L5.

The cemented lens between the biconvex lens L4 and the biconcave lens L5 in the third group corrects the spherical aberration, thereby reducing the refractive index difference and further reducing the radius of curvature of the cemented surface between the biconvex lens L4 and the biconcave lens L5. It is desirable. Therefore, it is desirable that n ₅ −n ₄ is smaller than 0.22. When n ₅ -n ₄ is 0.22 or more, the radius of curvature of the joint surface becomes large, so that spherical aberration and axial chromatic aberration are insufficiently corrected. However, if n ₅ -n ₄ is 0.12 or less, the radius of curvature of the joint surface becomes too small and the workability of the lens deteriorates, so n ₅ -n ₄ is preferably larger than 0.12. Therefore, it is desirable that the refractive index difference between the biconvex lens L4 and the biconcave lens L5 satisfies the conditional expression (4).

For the radius of curvature of the cemented surface, it is desirable to satisfy conditional expression (5) in order to optimize the correction amount of spherical aberration. If | R ₄₀ / R ₄₅ | is 1.4 or less, the amount of spherical aberration generated is too large, and cannot be corrected sufficiently when considered in the entire system. If | R ₄₀ / R ₄₅ | is 1.9 or more, the spherical aberration is overcorrected on the joint surface, and the spherical aberration is overcorrected when the entire system is considered.
In order to correct axial chromatic aberration, it is desirable to use a material having a small dispersion for the biconvex lens L4 and a material having a large dispersion for the biconcave lens L5. More specifically, it is desirable to satisfy conditional expression (3). Satisfying this can sufficiently correct axial chromatic aberration, but if this is not satisfied, axial chromatic aberration is insufficiently corrected.

Moreover, in the said invention, it is preferable to satisfy the following conditional expressions (6), (7), (8).
(6) n ₃ <1.65
(7) ν ₃ <50
(8) 3 <| R _3I / F ₁₂ | <5
Where n ₃ is the refractive index of the lens L3 with respect to the d-line, ν ₃ is the Abbe number of the lens L3 with respect to the d-line, R _3I is the radius of curvature of the lens L3 on the image plane side, and F ₁₂ is the first group and the second group. The combined focal length.

  It is desirable to use a material having a low refractive index and high dispersion as the material of the second lens group L3. By using a low-refractive-index and high-dispersion material for the lens L3 and making the image-side surface concave, it is possible to satisfactorily correct coma and axial chromatic aberration. Specifically, it is desirable to satisfy the conditional expressions (6) and (7).

  When the lens L3 does not satisfy the conditional expression (7), the axial chromatic aberration generated from the first group to the fourth group cannot be corrected, and the axial chromatic aberration is insufficiently corrected in the entire optical system. When the condition (6) is satisfied, the light flux after passing through the second group does not diverge so much even if the curvature radius on the image plane side of the lens L3 is reduced in order to increase the correction amount of coma aberration and axial chromatic aberration. It is possible to prevent the diameter of the light beam incident on the third group from increasing. If the conditional expression (6) is not satisfied, the radius of curvature on the image plane side of the lens L3 becomes too large to correct coma aberration and axial chromatic aberration sufficiently, or even if the radius of curvature is small, the image plane of the lens L3. The negative power on the side is too strong, the light beam after passing through the second group is too divergent, and the light beam diameter in the third group becomes too large.

Further, in order to balance the correction of coma and axial chromatic aberration generated in the first group and the second group and the divergence of the light beam after passing through the second group, the curvature radius R _3I on the image plane side of the lens L3 is: It is desirable to satisfy the conditional expression (8). When | R _3I / F ₁₂ | is 3 or less, the divergence angle of the light beam after passing through the second group becomes large, so that there is a problem that the light beam diameter in the third group becomes large and the lens outer diameter becomes large. When | R _3I / F ₁₂ | is 5 or more, the negative power on the image plane side of the lens L3 becomes small, so that the coma aberration and the longitudinal chromatic aberration are insufficiently corrected.

In the above invention, it is preferable that the most object side lens in the fifth group is a cemented lens in which the negative lens L7 and the positive lens L8 are cemented, and the following conditional expression (9) is satisfied.
(9) 0.2 <F ₁₄ ² · {(n ₅ −1) / R _5I ² + (n ₇ −n ₈ ) / R ₇₈ ² } <0.4
Where F ₁₄ is the focal length of the first group to the fourth group, n ₅ , n ₇ , and n ₈ are the refractive indices of the biconcave lens L5, the negative lens L7, and the positive lens L8 with respect to the d line, and R _5I. , R ₇₈ is the radius of curvature of the biconcave lens L5 on the image plane side, and the radius of curvature of the cemented surface of the negative lens L7 and the positive lens L8.

  Spherical aberration is corrected by the image surface side of the biconcave lens L5 and the cemented surface of the negative lens L7 and the positive lens L8. Conditional expression (9) satisfies the image surface side surface of the biconcave lens L5 and the negative lens L7. This is a condition for making the amount of spherical aberration corrected at the cemented surface with the lens L8 appropriate. Below the conditional expression, the spherical aberration becomes undercorrected, and when above the conditional expression, the spherical aberration becomes overcorrected.

In the invention described above, the fifth lens unit has a cemented lens in which the negative lens L7 and the positive lens L8 closest to the object side are cemented from the object side, and the concave surface is directed to the positive lens L9 and the positive lens L10 from the image surface side. It is preferable that a cemented lens in which the negative lens L11 is cemented is included.
On the cemented surface between the negative lens L7 and the positive lens L8, spherical aberration, axial chromatic aberration, and coma aberration generated in the fourth group are corrected. Further, astigmatism can be corrected at the cemented surface between the positive lens L10 and the negative lens L11.

  According to the present invention, there is an effect that it is possible to realize an objective optical system suitable for in vivo observation with a small outer diameter, a long overall length, a well corrected chromatic aberration, and a high numerical aperture.

Hereinafter, an immersion objective optical system 1 according to a first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the immersion objective optical system 1 according to this embodiment includes, in order from the object side, a first group G1 having a positive power, a second group G2 having a positive power, a third group G3 having a negative power, It is composed of a positive power fourth group G4 and a positive power fifth group G5.

The first group G1 includes a plano-convex lens L1 having a convex surface facing the image plane. That is, the plano-convex lens L1 has a substantially flat surface disposed on the object side.
The second group G2 includes a lens L2 disposed on the object side and a lens L3 disposed on the image plane side. The lens L2 is disposed with the convex surface facing the object side. The lens L3 is arranged with the concave surface facing the image plane side.

The third group G3 includes a cemented lens in which a biconvex lens L4 disposed on the object side and a biconcave lens L5 disposed on the image plane side are cemented.
The fourth group G4 includes a positive lens L6 having a convex surface directed toward the object side.
The fifth group G5 includes, from the object side, a cemented lens of a negative meniscus lens L7 and a biconvex lens L8, a planoconvex lens L9 having a convex surface facing the object side, and a planoconvex lens L10 and a biconcave lens L11 having a substantially flat surface facing the object side. And has a positive power as a whole.

  According to the immersion objective optical system 1 according to the present embodiment configured as described above, in the first group G1, a substantially flat surface on the object side of the plano-convex lens L1 is provided between the immersion objective optical system 1 and the object. It is possible to prevent bubbles from entering. Further, the convex surface on the image plane side of the plano-convex lens L1 can be made close to an aplanatic condition to suppress the occurrence of spherical aberration and coma aberration.

In the second group G2, the light is refracted by the convex surface on the object side of the lens L2, the divergence angle of the light beam is reduced inside the lens L2, and the light beam height is prevented from increasing. Can be reduced. Further, the light can be further refracted by the convex surface on the image plane side of the lens L2, and the divergence of the light beam can be further reduced inside the lens L2.
Further, coma aberration and axial chromatic aberration generated in the lens L2 can be corrected by slightly diverging the light beam on the concave surface on the image plane side of the lens L3.

In the third group G3, the light beam slightly diverged in the second group G2 is gently converged on the object-side convex surface of the biconvex lens L4, thereby preventing the height of light rays from increasing in the cemented lens. it can. The cemented surface can correct the spherical aberration generated on the object side of the first group G1, the second group G2, and the biconvex lens L4 and the axial chromatic aberration generated in the first group G1 and the biconvex lens L4. .
Further, by diverging the light beam on the concave surface on the image plane side of the biconcave lens L5, it is possible to correct spherical aberration that has been insufficiently corrected from the plano-convex lens L1 to the biconvex lens L4, and further to correct axial chromatic aberration. Further, coma aberration generated in the lens L2 and the biconvex lens L4 can be corrected on this surface.

In the fourth group G4, the divergent light beam exiting the biconcave lens L5 is made into a substantially parallel light beam. The convex surface on the object side of the biconvex lens L6 can prevent the light beam height from increasing in the biconvex lens L6 and prevent the lens outer diameter from increasing.
Further, in the fifth group G5, the light beam that has become substantially parallel after passing through the biconvex lens L6 is converged by a cemented lens of a negative meniscus lens L7 and a biconvex lens L8 and a planoconvex lens L9. On the cemented surface between the negative meniscus lens L7 and the biconvex lens L8, it is possible to correct spherical aberration, axial chromatic aberration, and coma aberration generated in the fourth group G4.
Further, astigmatism can be corrected at the cemented surface between the planoconvex lens L10 and the biconcave lens L11.

According to the immersion objective optical system 1 according to the present embodiment configured as described above, the outer diameter is narrow, the total length is long, the chromatic aberration is well corrected, the numerical aperture is high, and it is suitable for in vivo observation. An objective optical system can be realized.
In particular, it is preferable that the following conditional expressions (1) to (9) are satisfied.

That is,
(1) 0.03 <| F ₁₂ / F ₃ | <0.13
(2) 0.8 <| β · F ₁₄ / F ₅ | <1.2
(3) ν ₄ −ν ₅ > 40
(4) 0.12 <n ₅ −n ₄ <0.22
(5) 1.4 <| R _4O / R ₄₅ | <1.9
(6) n ₃ <1.65
(7) ν ₃ <50
(8) 3 <| R _3I / F ₁₂ | <5
(9) 0.2 <F ₁₄ ² · {(n ₅ −1) / R _5I ² + (n ₇ −n ₈ ) / R ₇₈ ² } <0.4
It is.

Here, F ₃ is the focal length of the third group, F ₁₂ is the focal length of the first group and the second group, β is the magnification of the immersion objective optical system, and F ₁₄ is the first group to the fourth group. F ₅ is the focal length of the fifth group, ν ₄ and ν ₅ are respectively the biconvex lens L4, the Abbe number of the biconcave lens L5 with respect to the d line, and n ₄ and n ₅ are each the biconvex lens L4. , the refractive index for the d-line of the biconcave lens _L5, each R. _{4O, R 45} is the object side, the radius of curvature, _{n 3} of the cemented surface of the biconvex lens L4 and a biconcave lens L5 of the biconvex lens L4 is refracted to the d-line of the lens L3 Ν ₃ is the Abbe number of the lens L3 with respect to the d-line, R _3I is the radius of curvature of the lens L3 on the image plane side, F ₁₂ is the focal length of the first group and the second group, and F ₁₄ is from the first group. The focal lengths up to the fourth group, n ₅ , n ₇ , and n ₈ are the lens L5, The refractive indexes of the lens L7 and the lens L8 with respect to the d-line, R _5I and R ₇₈ are the radius of curvature on the image plane side of the lens L5 and the radius of curvature of the cemented surface between the lens L7 and the lens L8.

When | F ₁₂ / F ₃ | is 0.03 or less, the Petzval sum increases and the curvature of field increases. When | F ₁₂ / F ₃ | is 0.13 or more, the negative power of the third group becomes too strong, and the positive power of the first group and the second group becomes too weak. In either case, since the light beam diameter is increased, it is necessary to increase the outer diameter of the lens, which causes a problem that the optical system is highly invasive to a living body.

In addition, when | β · F ₁₄ / F ₅ | is 0.8 or less, the power between the first group and the fourth group becomes too strong, and the amount of various aberrations increases. Aberration correction becomes difficult. When | β · F ₁₄ / F ₅ | is 1.2 or more, the power between the first group and the fourth group becomes weak, so that the amount of various aberrations can be reduced, but the beam diameter Therefore, it is necessary to increase the outer diameter of the lens, which causes a problem that the invasion to the living body increases.

Further, the cemented lens of the third group of biconvex lens L4 and biconcave lens L5 has a smaller refractive index difference in order to correct spherical aberration, and further increases the radius of curvature of the cemented surface between biconvex lens L4 and biconcave lens L5. It is desirable to make it smaller. Therefore, it is desirable that n ₅ −n ₄ is smaller than 0.22. When n ₅ -n ₄ is 0.22 or more, the radius of curvature of the joint surface becomes large, so that spherical aberration and axial chromatic aberration are insufficiently corrected. However, if n ₅ -n ₄ is 0.12 or less, the radius of curvature of the joint surface becomes too small and the workability of the lens deteriorates, so n ₅ -n ₄ is preferably larger than 0.12. Therefore, it is desirable that the refractive index difference between the biconvex lens L4 and the biconcave lens L5 satisfies the conditional expression (4).

For the radius of curvature of the cemented surface, it is desirable to satisfy conditional expression (5) in order to optimize the correction amount of spherical aberration. If | R ₄₀ / R ₄₅ | is 1.4 or less, the amount of spherical aberration generated is too large, and cannot be corrected sufficiently when considered in the entire system. If | R ₄₀ / R ₄₅ | is 1.9 or more, the spherical aberration is overcorrected on the joint surface, and the spherical aberration is overcorrected when the entire system is considered.
In order to correct axial chromatic aberration, it is desirable to use a material having a small dispersion for the biconvex lens L4 and a material having a large dispersion for the biconcave lens L5. More specifically, it is desirable to satisfy conditional expression (3). Satisfying this can sufficiently correct axial chromatic aberration, but if this is not satisfied, axial chromatic aberration is insufficiently corrected.

  Further, the material of the second group plano-concave lens L3 is desirably a low refractive index and high dispersion material. By using a material having a low refractive index and high dispersion as the material of the plano-concave lens L3 and making the image side surface concave, coma and axial chromatic aberration can be favorably corrected. Specifically, it is desirable to satisfy the conditional expressions (6) and (7).

  When the plano-concave lens L3 does not satisfy the conditional expression (7), the axial chromatic aberration generated from the first group to the fourth group cannot be corrected, and the axial chromatic aberration is insufficiently corrected in the entire optical system. When the condition (6) is satisfied, the light flux after passing through the second group does not diverge too much even if the curvature radius on the image plane side of the plano-concave lens L3 is reduced in order to increase the correction amount of coma aberration and axial chromatic aberration. Therefore, it is possible to prevent the diameter of the light beam incident on the third group from increasing. When the conditional expression (6) is not satisfied, the curvature radius on the image plane side of the plano-concave lens L3 becomes too large to sufficiently correct the coma aberration and the axial chromatic aberration, or even if the curvature radius is small, the plano-concave lens L3 The negative power on the image plane side is too strong, the light beam after passing through the second group is too divergent, and the light beam diameter in the third group becomes too large.

Further, in order to balance the correction of coma aberration and axial chromatic aberration generated in the first group and the second group and the divergence of the light beam after passing through the second group, the curvature radius R _3I on the image plane side of the plano-concave lens L3. It is desirable to satisfy the conditional expression (8). When | R _3I / F ₁₂ | is 3 or less, the divergence angle of the light beam after passing through the second group becomes large, so that there is a problem that the light beam diameter in the third group becomes large and the lens outer diameter becomes large. When | R _3I / F ₁₂ | is 5 or more, the negative power on the image plane side of L3 becomes small, so that coma and axial chromatic aberration are undercorrected.

  Spherical aberration is corrected by the image surface side of the biconcave lens L5 and the cemented surface of the negative meniscus lens L7 and the biconvex lens L8. Conditional expression (9) indicates that the image surface side surface of the biconcave lens L5 and the negative meniscus lens L7 Is a condition for making the amount of spherical aberration corrected at the cemented surface between the lens and the biconvex lens L8 appropriate. Below the conditional expression, the spherical aberration becomes undercorrected, and when above the conditional expression, the spherical aberration becomes overcorrected.

FIG. 2 shows an example in which the immersion objective optical system 1 according to this embodiment is connected to a small laser scanning confocal optical system 2.
An excitation laser light source (not shown) is provided in the optical unit 4. The laser light is guided to the scanning unit 3 through the optical fiber 8 and collimated by the collimator optical system 10, and then the optical scanning unit 11. Then, the light exit direction is scanned, and an image is formed at the intermediate image forming position by the pupil projection optical system 12. The pupil projection optical system 12 and the immersion objective optical system 1 are connected, and an image formed by the pupil projection optical system 12 is converted into an object ( The image is re-imaged on the observation target part B) of the living body 7 to excite an object (biological tissue, pigment, etc.).

Fluorescence generated in the object B passes through the immersion objective optical system 1, the pupil projection optical system 12, the optical scanning unit 11, the collimator optical system 10, and the optical fiber 8, and is excited with excitation light by a dichroic mirror (not shown) in the optical unit 4. After being separated, the light is detected by a photodetector through an excitation light cut filter and displayed on a monitor 7 via a computer 6.
In this embodiment, the core of the optical fiber 8 serves as a confocal pinhole, and when observing an object, light from a portion other than the vicinity of the focused portion is cut, so the SN ratio is high. Observation is possible. Further, by operating the drive unit 13 in the scanning unit 3 by the operation of the control unit 5 and changing the distance between the collimator lens 10 and the optical fiber 8, the longitudinal direction (Z direction) of the immersion objective optical system 1 is changed. The observation position can be adjusted. Therefore, three-dimensional image acquisition is also possible by combining with scanning in the horizontal direction (X, Y direction) by the optical scanning unit 11.

Next, an immersion objective optical system 20 according to the second embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 3, the immersion objective optical system 20 according to this embodiment includes, in order from the object side, a first group G1 having a positive power, a second group G2 having a positive power, a third group G3 having a negative power, It is the same as in the first embodiment in that the fourth group G4 of positive power and the fifth group G5 of positive power are configured. The immersion objective optical system 20 according to the present embodiment is different in the components of each lens group.

  The first group G1 is composed of a cemented lens of a parallel plate P1 and a plano-convex lens L1. The parallel plate P1 is disposed on the object side, and the plano-convex lens L1 is disposed with the convex surface facing the image plane side. Thereby, the first group has positive power as a whole.

The second group G2 includes a biconvex lens L2 and a plano-concave lens L3. The plano-convex lens L2 is disposed on the object side, and the second group G2 has a positive power as a whole.
The third group G3 is constituted by a cemented lens in which a biconvex lens L4 and a biconcave lens L5 are cemented. The biconvex lens L4 is disposed on the object side, and the third group as a whole has negative power.
The fourth group G4 includes a biconvex lens L6 and has positive power.
The second group G2 to the fourth group G4 are the same as the immersion objective optical system 1 according to the first embodiment.

  The fifth group G5 includes a cemented lens composed of a plano-concave lens L7 and a plano-convex lens L8, and a cemented lens composed of a plano-convex lens L9 and a biconvex lens L10 and a biconcave lens L11, which are arranged in order from the object side. The plano-concave lens L7 has a substantially flat surface on the object side. The fifth group G5 has a positive power as a whole.

  According to the immersion objective optical system 20 according to the present embodiment configured as described above, in the first group G1, the refractive index of the plano-convex lens L1 is larger than that of the immersion objective optical system 1 according to the first embodiment. Thus, the radius of curvature of the convex surface on the image plane side can be increased, and the thickness of the plano-convex lens L1 itself can be increased. Thereby, the processability of the lens becomes better than that of the first embodiment, and the manufacturing cost can be reduced.

  Further, as compared with the first embodiment, the generation of astigmatism can be reduced by increasing the refractive index of the plano-convex lens L1. For this reason, a wider observation range than the immersion objective optical system 1 according to the first embodiment can be secured. Furthermore, when the resistance of the plano-convex lens L1 to water or a living body is not high, the plano-convex lens L1 can be protected by bonding P1 having good resistance to the tip.

In the fifth group, the light beam that has become substantially parallel light after passing through the biconvex lens L6 of the fourth group is converged by the planoconvex lens L9 and the cemented lens of the biconvex lens L10 and the biconcave lens L11. In addition, spherical aberration, axial chromatic aberration, and coma generated in the fourth group G4 can be corrected on the cemented surface between the plano-concave lens L7 and the plano-convex lens L8. Furthermore, astigmatism can be corrected on the cemented surface between the biconvex lens L10 and the biconcave lens L11.
The operation of the other lens groups G2 to G4 is the same as that of the first embodiment.

According to the immersion objective optical system 20 according to the present embodiment configured as described above, like the immersion objective optical system 1 according to the first embodiment, the outer diameter is narrow, the entire length is long, and the chromatic aberration is good. Thus, an objective optical system suitable for in vivo observation can be realized with a high numerical aperture. In particular, it is preferable that the conditional expressions (1) to (9) are satisfied.
Further, the immersion objective optical system 20 according to the present embodiment can be connected to the laser scanning confocal optical system 2 as in the first embodiment.

Next, an immersion objective optical system 30 according to a third embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 4, the immersion objective optical system 30 according to the present embodiment also includes, in order from the object side, a first group G1 having a positive power, a second group G2 having a positive power, and a third group G3 having a negative power. It is the same as the first and second embodiments in that the fourth group G4 of positive power and the fifth group G5 of positive power are configured. The immersion objective optical system 30 according to this embodiment is different from the constituent elements of each lens group, and is different from the first and second embodiments in that the working distance is increased.

The first group G1 includes a cemented lens in which a parallel plate P1 and a plano-convex lens L1 are cemented. The plano-convex lens L1 is arranged with the convex surface facing the image surface side. The first group G1 has a positive power as a whole.
The second group G2 includes a cemented lens in which a biconvex lens L2 and a biconcave lens L3 are cemented. The biconvex lens L2 is disposed on the object side, and the biconcave lens L3 is disposed on the image plane side, with the convex surface facing the object side and the concave surface facing the image plane side.

The third group G3 includes a cemented lens in which a biconvex lens L4 and a biconcave lens L5 are cemented. The third group G3 has negative power as a whole.
The fourth group G4 includes a biconvex lens L6.
The fifth group G5 includes a cemented lens of a negative meniscus lens L7 and a planoconvex lens L8, a planoconvex lens L9, a parallel plate P2, and a cemented lens of a biconvex lens L10 and a biconcave lens L11. The fifth group G5 has a positive power as a whole. The biconvex lens L10 is provided to ensure a long overall length.

  According to the immersion objective optical system 30 according to the present embodiment configured as described above, in the second group G2, light is refracted by the convex surface on the object side of the biconvex lens L2, and the light beam is reflected inside the biconvex lens L2. It is possible to reduce the divergence angle and prevent the light beam height from increasing. As a result, the lens outer diameter can be reduced.

  Further, the coma aberration and the axial chromatic aberration generated by the biconvex lens L2 can be corrected by slightly diverging the light beam on the concave surface on the image plane side of the biconcave lens L3. Further, since the biconvex lens L2 and the biconcave lens L3 are cemented, it is not necessary to provide a spacing tube between the biconvex lens L2 and the biconcave lens L3, and the number of parts can be reduced, and spherical aberration due to an error in surface spacing. Can be prevented. Furthermore, even if the surface accuracy tolerance of the cemented surface between the biconvex lens L2 and the biconcave lens L3 is relaxed, the influence on the aberration can be reduced. Therefore, the manufacturing accuracy can be reduced by loosening the surface accuracy tolerance of the lens.

Further, in the fifth group G5, the light beam which has become substantially parallel light after passing through the biconvex lens L6 of the fourth group is cemented with the negative meniscus lens L7 and the plano-convex lens L8, and between the plano-convex lens L9 and the parallel plate P2. It can be made to converge by the lens and the cemented lens of the biconvex lens L10 and the biconcave lens L11.
On the cemented surface between the negative meniscus lens L7 and the plano-convex lens L8, it is possible to correct spherical aberration, axial chromatic aberration, and coma aberration generated in the fourth group G4. Further, astigmatism can be corrected on the cemented surface between the biconvex lens L10 and the biconcave lens L11.
The operation of the other lens groups G1, G3, G4 is the same as in the second embodiment.

According to the immersion objective optical system 30 according to the present embodiment configured as described above, the outer diameter is small and the overall length is the same as the immersion objective optical systems 1 and 20 according to the first and second embodiments. It is possible to realize an objective optical system that is long, has a well corrected chromatic aberration, has a high numerical aperture, and is suitable for in vivo observation. In particular, it is preferable that the conditional expressions (1) to (9) are satisfied.
Further, the immersion objective optical system 30 according to the present embodiment can also be connected to the laser scanning confocal optical system 2 as in the first embodiment.

[First embodiment]
An example of the immersion objective optical system 1 according to the first embodiment will be described below with reference to FIGS. 1 and 5 and Table 1. FIG.
1 and Table 1, symbol r is a radius of curvature (mm), symbol d is a surface separation (mm), and in Table 1, symbol n is a refractive index of the d-line (587.56 nm), symbol ν is an Abbe number ν = (n-1) shows a _{/ (n} F -n _C). Here, n _F and n _C are the refractive indexes of the F line and the C line, respectively.

In the aberration diagram of FIG. 5, the symbol NA is the numerical aperture on the image plane side, the symbol y is the image height, the symbol M is the meridional surface, the symbol S is the sagittal surface, and the chromatic aberration of magnification is the d-line (587. 56 nm).
The wavelength of the C line is 656.27 nm, the wavelength of the d line is 587.56 nm, the wavelength of the e line is 546.07 nm, the wavelength of the F line is 486.13 nm, and the wavelength of the g line is 435.84 nm.

The diameter of the lens is 0.9 mm for the plano-convex lens L1, 1 mm from the biconvex lens L2 to the biconcave lens L5, and 1.3 mm from the biconvex lens L6 to the biconcave lens L11, and is composed of only a very small diameter lens. Yes. For this reason, the immersion objective optical system 1 of the present embodiment is an optical system suitable for observing the deep part in the body of a small animal such as a mouse with minimal invasiveness.
Further, the immersion objective optical system 1 of the present embodiment has a total length of the optical system from the tip to the imaging surface of 10.44 mm, and a relay lens or CCD is connected behind the immersion objective optical system 1; Even if the image is monitored at a distance from the living body, the relay lens and the CCD are not easily in contact with the living body (such as its head).

Further, in the immersion objective optical system 1 according to the present embodiment, the numerical aperture on the object side of the immersion objective optical system 1 is ensured to be 0.5 in order to obtain a bright fluorescent image and high resolution. Further, since the longitudinal chromatic aberration and the lateral chromatic aberration are corrected well, the objective optical system is suitable as an objective optical system for white light observation and fluorescence observation, particularly a laser scanning confocal microscope.
The working distance (WD) is 0.098 mm, and the inside of the living body can be observed without blur by bringing the tip of the immersion objective optical system into close contact with the living body.

  Further, by connecting the immersion objective optical system 1 of this embodiment to the laser scanning confocal microscope system shown in FIG. 2, even if a pupil projection optical system or a scanning unit is connected behind the objective optical system, The pupil projection optical system and the scanning unit can be arranged without contacting a position away from the living body.

[Second Embodiment]
Next, an example of the immersion objective optical system 20 according to the second embodiment will be described below with reference to FIGS. 2 and 6 and Table 2. FIG.
2 and Table 2, the symbol r is the radius of curvature (mm), the symbol d is the surface interval (mm), the symbol n is the refractive index of the d-line (587.56 nm), and the symbol ν is the Abbe number ν = (n-1) shows a _{/ (n} F -n _C). Here, n _F and n _C are the refractive indexes of the F line and the C line, respectively.

In addition, in the aberration diagram of FIG. 6, symbol NA represents the numerical aperture on the image plane side, symbol y represents the image height, symbol M represents the meridional surface, symbol S represents the sagittal surface, and the chromatic aberration of magnification is the d-line (587. 56 nm).
The wavelength of the s-line is 852.11 nm, the wavelength of the C-line is 656.27 nm, the wavelength of the d-line is 587.56 nm, the wavelength of the e-line is 546.07 nm, the wavelength of the F-line is 486.13 nm, The wavelength is 435.84 nm.
Compared with the first embodiment, this embodiment corrects chromatic aberration from the visible light region to the near-infrared region in the vicinity of 900 nm, and further secures a wider range of observation than the first embodiment.

The diameter of the lens is 1 mm from the parallel plate P1 to the biconcave lens L5, and 1.4 mm from the biconvex lens L6 to the biconcave lens L11. The lens is composed of only a very small diameter lens.
For this reason, the immersion objective optical system 20 of the present embodiment is an optical system suitable for observing deep parts in the body of a small animal such as a mouse with minimal invasiveness.

Further, in the immersion objective optical system 20 of this embodiment, the total length of the optical system from the tip portion to the imaging surface is 11.55 mm, and a relay lens or CCD is connected behind the immersion objective optical system 20. Even if the image is monitored at a distance from the living body, the relay lens or CCD is difficult to come into contact with an animal (such as its head).
Further, in order to obtain a bright fluorescent image and high resolution, the numerical aperture on the object side of the immersion objective optical system 20 is set to 0.5.

Further, since the axial chromatic aberration and the lateral chromatic aberration are corrected well, it is suitable for white light observation and fluorescence observation, particularly as the immersion objective optical system 20 of the laser scanning confocal optical microscope.
Furthermore, since the aberration is corrected up to the near-infrared region where the scattering is small in the living body, the optical system can observe deeper from the tissue surface more clearly.
This embodiment can also be connected to the laser scanning confocal optical system 2 in the same manner as the first embodiment.

[Third embodiment]
Next, an example of the immersion objective optical system 30 according to the third embodiment will be described below with reference to FIGS. 3 and 7 and Table 3. FIG.
3 and 7 and Table 3 are the same as those in the second embodiment.
In the present embodiment, the working distance WD is increased as compared with the second embodiment.

The diameter of the lens is 1 mm from the parallel plate P1 to the biconcave lens L5, and 1.4 mm from the biconvex lens L6 to the biconcave lens L11. The lens is composed of only a very small diameter lens.
For this reason, the immersion objective optical system 30 of the present embodiment is an optical system suitable for observing deep parts in the body of a small animal such as a mouse with minimal invasiveness.

Further, the immersion objective optical system 30 of the present embodiment has a total length of 11.71 mm from the tip portion to the imaging surface, and a relay lens or CCD is connected behind the objective lens, so that it is slightly from the living body. Even if the image is monitored at a distance, the relay lens or CCD is difficult to contact with an animal (such as its head).
In order to obtain a bright fluorescent image and high resolution, the numerical aperture NA on the object side of the immersion objective optical system 20 is 0.5.

Further, since the longitudinal chromatic aberration and the lateral chromatic aberration are corrected well, it is suitable as the immersion objective optical system 30 of white light observation and fluorescence observation, particularly a laser scanning confocal optical microscope.
Furthermore, since the aberration is corrected up to the near-infrared region where the scattering is small in the living body, the optical system can observe deeper from the tissue surface more clearly.

The working distance WD is 0.2 mm, and even when the tip of the immersion objective optical system 20 is pressed against the living tissue, a deeper place can be observed from the pressed living tissue surface.
Similarly to the first and second embodiments, this embodiment can be connected to the laser scanning confocal optical system 2.

Table 4 shows data of conditional expressions (1) to (9) in the first to third embodiments.

In addition, it is also possible to perform bright field observation by connecting an image fiber bundle and a CCD to the immersion objective optical systems 1, 20, and 30 of the present invention (all of the first to third embodiments).
At that time, an illumination fiber is provided just outside the immersion objective optical system 1, 20, 30 to illuminate the living body, or a relay lens and a half mirror are provided behind the objective optical system to illuminate the illumination light. There is a method of making it incident coaxially with the optical systems 1, 20 and 30.

It is a lens arrangement | sequence which shows the immersion objective optical system which concerns on the 1st Embodiment of this invention. It is a whole block diagram which shows the laser scanning confocal microscope system provided with the immersion objective optical system of FIG. It is a lens arrangement | sequence which shows the immersion objective optical system which concerns on the 2nd Embodiment of this invention. It is a lens arrangement | sequence which shows the immersion objective optical system which concerns on the 3rd Embodiment of this invention. It is a figure which shows each aberration by the Example of the immersion objective optical system of FIG. It is a figure which shows each aberration by the Example of the immersion objective optical system of FIG. FIG. 5 is a diagram illustrating aberrations according to the embodiment of the immersion objective optical system in FIG. 4.

Explanation of symbols

G1 1st group G2 2nd group G3 3rd group G4 4th group G5 5th group L1 Plano-convex lens L2 Biconvex lens (lens)
L3 Plano-concave lens (lens)
L4 Biconvex lens L5 Biconcave lens L6 Biconvex lens (positive lens)
L7 Negative meniscus lens (junction lens)
L8 Biconvex lens (Bonded lens)
L9 Plano-convex lens L10 Plano-convex lens (junction lens)
L11 Biconcave lens (Bonded lens: negative lens)
1, 20, 30 were combined focal length F ₁₂ first lens group G1 and the second lens group G2 of the immersion objective focal length of the optical system β immersion objective optical system magnification F ₃ third group G3 F ₅ fifth group G5 focal length F ₁₄ focal length [nu ₃ from the first group G1 combined to the fourth group G4, [nu _4, [nu ₅ respectively, the Abbe number n ₃ with respect to the d line of the lens L3~ lens L5, _{n 4, n} 5, n ₇ , n ₈ , the refractive index with respect to the d-line of the lenses L 3 to L ₈ , and the curvature radius R _4O , R ₄₅ on the image plane side of the R _3I lens L 3, respectively, the object side of the biconvex lens L 4, and the joint of the biconvex lens L 4 and the biconcave lens L 5 Radius of curvature of the surface R radius of curvature of the image plane side of the _5I lens L5 R ₇₈ radius of curvature of the joint surface between the lens L7 and the lens L8

Claims (6)

In order from the object side, the first group of positive power, the second group of positive power, the third group of negative power, the fourth group of positive power, the fifth group of positive power,
The first group includes a plano-convex lens L1 having a convex surface facing the image surface side, and the most object-side surface is substantially flat;
The second group includes a lens L2 in which the surface closest to the object side of the second group faces a convex surface toward the object side, and a lens L3 in which the surface closest to the image surface in the second group faces a concave surface toward the image surface side. Including
The third group includes a cemented lens in which a biconvex lens L4 and a biconcave lens L5 are cemented from the object side,
The fourth group includes a positive lens L6 having a convex surface facing the object side,
The fifth group, saw including at least one cemented lens,
An immersion objective optical system that satisfies the following conditional expression (1) .
(1) 0.03 <| F ₁₂ / F ₃ | <0.13
However,
F ₃ : focal length of the third group,
F ₁₂ : Focal length combining the first group to the second group
It is. Immersion objective optical system according to claim 1 which satisfies the following conditional expression (2).
(2) 0.8 <| β · F ₁₄ / F ₅ | <1.2
However,
β: magnification of the immersion objective optical system,
F ₁₄ : focal length combining the first group to the fourth group,
F ₅ is the focal length of the fifth group. The following conditional expression (3), (4), an immersion objective optical system according to claim 1 or claim 2, satisfying the expression (5).
(3) ν ₄ −ν ₅ > 40
(4) 0.12 <n ₆ −n ₄ <0.22
(5) 1.4 <| R _4O / R ₄₅ | <1.9
However,
ν ₄ , ν ₅ : Abbe numbers of the biconvex lens L4 and the biconcave lens L5 with respect to the d line,
n ₄ , n ₅ : Refractive index of the biconvex lens L4 and the biconcave lens L5 with respect to the d line,
R _4O and R ₄₅ are the radius of curvature of the object side of the biconvex lens L4 and the cemented surface of the biconvex lens L4 and the biconcave lens L5, respectively. The immersion objective optical system according to any one of claims 1 to 3 , wherein the following conditional expressions (6), (7), and (8) are satisfied.
(6) n ₃ <1.65
(7) ν ₃ <50
(8) 3 <| R _3I / F ₁₂ | <5
However,
n ₃ : the refractive index of the lens L3 with respect to the d-line,
ν ₃ : Abbe number of the lens L3 with respect to the d-line,
R _3I : radius of curvature on the image plane side of the lens L3,
F ₁₂ is a focal length obtained by combining the first group and the second group. Of the fifth group, the most object side lens is a cemented lens in which a negative lens L7 and a positive lens L8, any one of claims 1 to 4 which satisfies the following conditional expression (9) The immersion objective optical system according to 1.
(9) 0.2 <F ₁₄ ² · {(n ₅ −1) / R _5I ² + (n ₇ −n ₈ ) / R ₇₈ ² } <0.4
However,
F ₁₄ : focal length combining the first group to the fourth group,
n ₅ , n ₇ , n ₈ : Refractive indexes of the lens L5, the lens L7, and the lens L8 with respect to the d-line,
R _5I , R _{78 are the} radius of curvature of the lens L5 on the image plane side and the radius of curvature of the cemented surface between the lens L7 and the lens L8. The fifth group includes a cemented lens obtained by cementing the negative lens L7 and the positive lens L8 closest to the object side from the object side, a positive lens L9, a positive lens L10, and a negative lens L11 having a concave surface facing the image surface side. immersion objective optical system according to any one of claims 1 to 5 which comprises bonding the cemented lens.

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