JP2009205007A - Finite system objective optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a finite system objective optical system which excels in workability of a lens, and has a small outside diameter and long entire length, whose spherical aberration, chromatic aberration and coma aberration are satisfactorily corrected, and which is suitable for in-vivo observation. <P>SOLUTION: The finite system objective optical system 1 comprises, from an object side, a first group G<SB>1</SB>having positive power, a second group G<SB>2</SB>including a cemented lens, a third group G<SB>3</SB>comprising a biconvex lens L<SB>3</SB>, a fourth group G<SB>4</SB>including a cemented lens, and a fifth group G<SB>5</SB>having positive power, wherein cemented surfaces of the second group G<SB>2</SB>and the fourth group G<SB>4</SB>have negative refractive power. The objective optical system 1 satisfies following conditional expressions (1) to (7). The expression (1): 0.05<¾(1/F<SB>2</SB>+1/F<SB>5</SB>)/(1/F<SB>1</SB>+1/F<SB>3</SB>+1/F<SB>5</SB>)¾<0.25, the expression (2): ν<SB>2L</SB><75, the expression (3): 8<ν<SB>2L</SB>-ν<SB>2H</SB><30, the expression (4): 0.05<n<SB>2H</SB>-n<SB>2L</SB><0.15, the expression (5): ν<SB>4L</SB><75, the expression (6): 8<ν<SB>4L</SB>-ν<SB>4H</SB><30, and the expression (7): 0.05<n<SB>4H</SB>-n<SB>4L</SB><0.15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a finite objective optical system.

  Conventionally, in order to realize an optical system capable of observing a living body with minimal invasiveness, an appropriate arrangement of lens groups having a small outer diameter, a long total length, and good correction of chromatic aberration has been disclosed (for example, Patent Document 1). reference.).

JP 2006-227310 A

In the field of cranial nerve research and the like, it has been found that the outer diameter needs to be further reduced in order to further reduce the degree of invasiveness.
On the other hand, the lens group disclosed in Patent Document 1 proposes that the Abbe number difference of the cemented lens of the second group be 35 or more in order to correct chromatic aberration. However, in order to increase the Abbe number difference to 35 or more, anomalous dispersion glass having an Abbe number on the low dispersion side of greater than 80 must be used. Generally, anomalous dispersion glass often has a high degree of wear, and particularly has a small diameter. In the case of this lens, there is a disadvantage that processing is extremely difficult.

  The present invention has been made in view of the above-described circumstances, and has good workability of the lens, a small outer diameter, a long overall length, and well corrected spherical aberration, chromatic aberration, and coma aberration, and is suitable for in vivo observation. The object is to provide a finite objective optical system.

In order to achieve the above object, the present invention provides the following means.
The present invention includes, from the object side, a positive power first group, a second group including a cemented lens, a third group composed of biconvex lenses, a fourth group including a cemented lens, and a fifth positive power. There is provided a finite objective optical system that is configured by a group, the joint surfaces of the second group and the fourth group have negative refractive power, and satisfy the following conditional expressions (1) to (7).
(1) 0.05 <| (1 / F ₂ + 1 / F ₅ ) / (1 / F ₁ + 1 / F ₃ + 1 / F ₅ ) | <0.25
(2) ν _2L <75
(3) 8 <ν _2L −ν _2H <30
(4) 0.05 <n _2H -n _2L <0.15
(5) ν _4L <75
(6) 8 <ν _4L −ν _4H <30
(7) 0.05 <n _4H -n _4L <0.15
here,
F ₁ , F ₂ , F ₃ , F ₄ , F ₅ : first group, second group, third group, fourth group, fifth group focal length,
n _2H : d-line refractive index of the lens having the higher refractive index of the second group,
n _2L : d-line refractive index of the lens having the lower refractive index of the second group,
ν _2H : Abbe number of the lens having the higher refractive index of the second group,
ν _2L : Abbe number of the lens having the lower refractive index of the second group,
n _4H : d-line refractive index of the lens having the higher refractive index of the fourth group,
n _4L : d-line refractive index of the lens having the lower refractive index of the fourth group,
ν _4H : Abbe number of the lens having the higher refractive index of the fourth group,
ν _4L : Abbe number of the lens having the lower refractive index of the fourth group.

  According to the present invention, the light from the object is made substantially parallel by the convex surfaces on the object side of the first group and the third group of positive power, and the intermediate image is formed by converging the light on the image side and the fifth group of the third group. Let it form. The axial chromatic aberration and spherical aberration generated in these groups can be corrected by the negative power cemented surfaces of the second and fourth group cemented lenses.

  By satisfying conditional expression (1), it is possible to correct spherical aberration and longitudinal chromatic aberration in a balanced manner without increasing the beam diameter. If it is 0.05 or less, spherical aberration and axial chromatic aberration are undercorrected, and if it is 0.25 or more, the diameter of the light beam in the third group becomes large and the degree of invasiveness to animals increases, but conditional expression (1 ) Can be prevented from occurring.

By satisfying conditional expression (2), the workability of the second lens group can be improved. There are many glass materials with poor workability in the region of 75 or less.
By satisfying conditional expression (3), axial chromatic aberration can be corrected. If it is 8 or less, the chromatic aberration cannot be sufficiently corrected, and if it is 30 or more, it becomes necessary to use difficult-to-process glass material.
By satisfying conditional expression (4), it is possible to correct the longitudinal chromatic aberration and the spherical aberration by reducing the curvature radius of the joint surface without increasing the negative power.
By satisfying conditional expression (5), the workability of the fourth lens group can be improved. There are many glass materials with poor workability in the region of 75 or more.
By satisfying conditional expression (6), axial chromatic aberration can be corrected. If it is 8 or less, the chromatic aberration cannot be corrected sufficiently, and if it is 30 or more, it becomes necessary to use difficult-to-process glass material.
The axial chromatic aberration and the spherical aberration can be corrected by reducing the radius of curvature of the joint surface without increasing the negative power, which is preferable to satisfy the conditional expression (7).

In the above invention, it is preferable that the third group satisfies the following conditional expression (8).
(8) ν ₃ > 60
Here, ν3 is the Abbe number of the third group.
By doing so, it is possible to reduce the occurrence of axial chromatic aberration in the third group. In the case of 60 or less, it is difficult to correct axial chromatic aberration.

Moreover, in the said invention, it is preferable that the said 5th group is a biconvex lens, and satisfies the following conditional expressions (9).
(9) 1.5 <| R _5i / R _5o | <2.5
here,
R _5i : radius of curvature of the fifth group on the image side,
R _5o is the radius of curvature of the fifth group on the object side.
By doing so, the occurrence of spherical aberration and coma aberration can be reduced, and the position of the intermediate image can be separated from the end surface of the image side lens of the fifth group. When the ratio is 1.5 or less, the spherical aberration and the coma aberration are undercorrected. When the ratio is 2.5 or more, the distance between the position of the intermediate image and the end surface of the image side lens of the fifth group becomes too short. There is a problem that minute coating defects of the lens are easily reflected in the observation image.

  According to the present invention, there is an effect that it is possible to provide a finite objective optical system in which the workability of the lens is good, the outer diameter is small, the total length is long, and spherical aberration, chromatic aberration, and coma aberration are well corrected.

A finite objective optical system 1 according to an embodiment of the present invention will be described below with reference to FIGS.
A finite objective optical system 1 according to the present embodiment is provided in a microscope 2 shown in FIG. The microscope 2 is a laser scanning microscope, and includes a laser light source 3 that emits laser light, a coupling optical system 4 that condenses the laser light from the laser light source 3, and a light collected by the coupling optical system 4. An optical fiber 5 for guiding the emitted laser light and a microscope main body 6 connected to the laser light source 3 by the optical fiber 5 are provided.

  The laser light source 3 includes a plurality of light sources 3a and 3b that emit laser beams having different wavelengths, a mirror 3c, and a dichroic mirror 3d.

  The microscope body 6 includes a collimating optical system 7 that converts laser light emitted from the optical fiber 5 into substantially parallel light, a dichroic mirror 8 that deflects laser light that has been made substantially parallel light by the collimating optical system 7, A proximity galvanometer mirror 9 that two-dimensionally scans the laser beam deflected by the dichroic mirror 8, a pupil projection optical system 10, an imaging optical system 11, and a tip that condense the laser beam scanned by the proximity galvanometer mirror 9 And an optical system 12.

The tip optical system 12 includes a working distance adjustment optical system 13, an intermediate optical system 14, and the finite objective optical system 1 according to the present embodiment.
As shown in FIG. 2, the working distance adjusting optical system 13 includes a negative lens group 13a, a positive lens group 13b, and a lens driving unit 13c that drives the positive lens group 13b. Parallel laser light incident from the imaging optical system 11 side is emitted from the negative lens group 13a side of the working distance adjusting optical system 13, but the positive lens group 13b is moved in the optical axis direction by the lens driving means 13c. Then, the divergence or convergence angle of the light beam emitted from the working distance adjusting optical system 13 changes.

The intermediate optical system 14 condenses the light incident from the working distance adjustment optical system 13. The condensing position varies depending on the position of the positive lens group 13b of the working distance adjusting optical system 13.
The finite objective optical system 1 according to this embodiment illuminates the sample A by condensing the light collected by the intermediate optical system 14 into the sample A again.

  In this embodiment, the focused point becomes the observation point, but the distance in the optical axis direction from the most advanced portion of the finite objective optical system 1 to this point, that is, the working distance (abbreviated WD) is the working point. Since it changes depending on the position of the positive lens group 13b of the distance adjustment optical system 13, a three-dimensional image is formed by observing an image of an arbitrary depth in the sample A or acquiring an image while changing the working distance. Can be done.

As shown in FIG. 3, the finite objective optical system 1 according to the present embodiment is a first positive-power first lens in which a parallel plane plate L ₁₁ and a plano-convex lens L ₁₂ are joined along the optical axis direction from the object side. A group G ₁ , a second group G _{2 formed} by joining a plano-concave lens L ₂₁ and a plano-convex lens L ₂₂ , a third group G ₃ composed of a biconvex lens L ₃ , a plano-convex lens L ₄₁ and a plano-concave lens L ₄₂ are joined. a fourth group G ₄ which is, and a fifth group G ₅ Metropolitan of positive power having a biconvex lens L _5.

Since the flat refractive index of the concave lens L ₂₁ is higher than the refractive index of the plano-convex lens L _22, the bonding surfaces of the second group G ₂ has a negative power. Further, since the refractive index of the plano-convex lens L ₄₁ is lower than the refractive index of the plano-concave lens L ₄₂ , the cemented surface of the fourth group G ₄ also has a negative power. Further, the finite objective optical system according to the present embodiment satisfies the following conditional expressions (1) to (7).

(1) 0.05 <| (1 / F ₂ + 1 / F ₅ ) / (1 / F ₁ + 1 / F ₃ + 1 / F ₅ ) | <0.25
(2) ν _2L <75
(3) 8 <ν _2L −ν _2H <30
(4) 0.05 <n _2H -n _2L <0.15
(5) ν _4L <75
(6) 8 <ν _4L −ν _4H <30
(7) 0.05 <n _4H -n _4L <0.15
Here, F ₁ , F ₂ , F ₃ , F ₄ , F ₅ : focal lengths of the first group G ₁ , the second group G ₂ , the third group G ₃ , the fourth group G ₄ , and the fifth group G ₅ , N _2H : d-line refractive index of the plano-concave lens L _{21 with} the higher refractive index of the second group G ₂ , n _2L : d-line refractive index of the plano-convex lens L _{22 with} the lower refractive index of the second group G ₂ Refractive index, ν _2H : Abbe number of the plano-concave lens L _{21 with} the higher refractive index of the second group G ₂ , ν _2L : Abbe number of the plano-convex lens L _{22 with} the lower refractive index of the second group G ₂ , n _4H: d-line refractive index of the fourth group _G plano _{L 42} of the higher refractive index of _{4, n 4L:} refractive index of d-line of the four groups _{G 4} refractive index is lower plano _{L 41} , [nu _4H: the four group _{G 4} refractive index higher plano Abbe number of _{L 42,} ν _4L: Abbe number of the plano-convex lens _{L 41} having the lower refractive index of the fourth group _{G 4} A.

In this way, the light from the sample A is made substantially parallel by the object-side convex surfaces of the first group G ₁ and the third group G ₃ having positive power, and the image side and the fifth group G of the third group G _{3. 5} converges the light to form an intermediate image. Then, chromatic aberration and spherical aberration generated in the groups G ₁ , G ₃ , and G ₅ can be corrected by the negative power cemented surfaces of the cemented lenses of the second group G ₂ and the fourth group G ₄ .

By satisfying conditional expression (1), it is possible to correct spherical aberration and longitudinal chromatic aberration in a balanced manner without increasing the beam diameter. 0.05 corrected insufficiently spherical aberration and axial chromatic aberration is not more than, if it is 0.25 or more beam diameter is increased in the third group G _3, but invasive for the sample A is higher, the condition The occurrence of such inconvenience can be prevented by satisfying Expression (1).

By satisfying conditional expression (2), it is possible to improve the workability of the second group G ₂ of the lens. There are many glass materials with poor workability in the region of 75 or less.
By satisfying conditional expression (3), axial chromatic aberration can be corrected. If it is 8 or less, the chromatic aberration cannot be sufficiently corrected, and if it is 30 or more, it becomes necessary to use difficult-to-process glass material.
By satisfying conditional expression (4), it is possible to correct the longitudinal chromatic aberration and the spherical aberration by reducing the curvature radius of the joint surface without increasing the negative power.

By satisfying the conditional expression (5), it is possible to improve the processability of the fourth group G ₄ lens. There are many glass materials with poor workability in the region of 75 or more.
By satisfying conditional expression (6), axial chromatic aberration can be corrected. If it is 8 or less, the chromatic aberration cannot be corrected sufficiently, and if it is 30 or more, it becomes necessary to use difficult-to-process glass material.
The axial chromatic aberration and the spherical aberration can be corrected by reducing the radius of curvature of the joint surface without increasing the negative power, which is preferable to satisfy the conditional expression (7).

  The microscope body 6 is condensed by the tip optical system, returns through the imaging optical system 11, the pupil projection optical system 10, and the proximity galvanometer mirror 9, and the fluorescence or reflected light from the sample A transmitted through the dichroic mirror 8. A coupling optical system 15 is provided. The microscope 2 is connected to the microscope body 6 through the optical fiber 16 that guides fluorescence or reflected light from the sample A collected by the coupling optical system 15, and is guided by the optical fiber 16. A detection optical system 17 for detecting the fluorescence or reflected light, a control unit 18 for controlling them, and a display unit (not shown) for displaying an image of the fluorescence or reflected light detected by the detection optical system 17. Yes. The microscope body 6 is provided so as to be movable in directions of three axes (XYZ) orthogonal to each other, and is provided so as to be rotatable around each axis, and arbitrarily adjusts the position and angle of the tip of the detection optical system 17. Be able to.

The proximity galvanometer mirror 9 scans the observation position in a direction substantially perpendicular to the optical axis of the finite objective optical system 1. The intensity distribution of light from the sample A in a range corresponding to the swing angle of the proximity galvanometer mirror 9 is displayed on the display unit.
The finite objective optical system 1 is configured to suppress blurring of an observation image due to respiration or pulsation of the sample A by bringing its tip into close contact with the sample A.

  The detection optical system 17 includes a collimating optical system 19 that converts the fluorescence or reflected light guided by the optical fiber 16 into substantially parallel light, a plurality of dichroic mirrors 20 and 21 that are branched for each wavelength, and a barrier filter 22. The condenser lens 23 and the photodetector 24 are provided.

The operation of the finite objective optical system 1 according to this embodiment configured as described above will be described below.
In order to observe the sample A using the microscope 2, a laser beam is emitted from the laser light source 3 with the tip of the finite objective optical system 1 being in close contact with the sample A, and is passed through the optical fiber 5. The laser light guided to the microscope body 6 is deflected by the dichroic mirror 8 and scanned two-dimensionally by the proximity galvanometer mirror 9, and the sample is passed through the pupil projection optical system 10, the imaging optical system 11, and the tip optical system 12. A is irradiated.

  In the sample A irradiated with the laser light, fluorescence is generated by exciting the fluorescent material, and the generated fluorescence is collected by the finite objective optical system 1, and the intermediate optical system 14 and the working distance adjusting optical system are collected. 13, returns through the imaging optical system 11, the pupil projection optical system 10, and the proximity galvanometer mirror 9, passes through the dichroic mirror 8, and is condensed at the end of the optical fiber 16 by the coupling optical system 15. Is detected by the detection optical system 17.

In this case, for example, when the positive lens group 13b is moved in the optical axis direction by the lens driving unit 13c, the working distance of the finite objective optical system 1 (the distance at which the focal point is focused on the tip of the finite objective optical system 1) is obtained. Change.
Therefore, an image having an arbitrary depth in the sample A can be observed without moving the finite objective optical system 1. Furthermore, if a plurality of images are acquired while moving the positive lens group 13b, a three-dimensional image of the sample A can be acquired.

  According to the finite objective optical system 1 according to the present embodiment, by satisfying the conditional expressions (1) to (7), the processability of the lens is improved, the outer diameter is reduced, the overall length is increased, and the spherical surface is increased. Aberration, chromatic aberration, and coma can be corrected well. As a result, the finite objective optical system 1 suitable for in vivo observation can be provided.

Example 1
Hereinafter, a first example of the finite objective optical system 1 according to the present embodiment will be described with reference to FIGS.
FIG. 3 shows the arrangement of the lenses of the finite objective optical system 1 according to this example, and Table 1 shows the lens data.

In Table 1 (hereinafter, the same applies to each table), S is the surface number, R is the radius of curvature, D is the surface spacing, nd is the refractive index of the d-line, and ν is the Abbe number.
In addition, each aberration when the object side of the finite objective optical system 1 of this embodiment is filled with water (d-line refractive index 1.33304, Abbe number 55.79) and the working distance is 0.2 mm is shown in FIG. To FIG.
In the aberration diagrams, NA represents the numerical aperture on the object side, and FIY represents the object height.
According to this example, it can be seen that spherical aberration, chromatic aberration, and coma are well corrected.

(Example 2)
Next, a second example of the finite objective optical system 1 according to the present embodiment will be described with reference to FIGS.
FIG. 7 shows the arrangement of the lenses of the finite objective optical system 1 according to this example, and Table 2 shows the lens data.

The finite objective optical system 1 according to the present embodiment is obtained by changing the glass types of the second group G ₂ and the fourth group G ₄ of the finite objective optical system 1 according to the first embodiment.
Each aberration of the finite objective optical system 1 according to the present example under the same conditions as in the first example is shown in FIGS.
According to this aberration diagram, it can be seen that axial chromatic aberration and spherical aberration are corrected better than in the first embodiment.

(Example 3)
Next, a third example of the finite objective optical system 1 according to the present embodiment will be described with reference to FIGS.
The arrangement of the lenses of the finite objective optical system 1 according to the present example is shown in FIG.

Finite-system objective optical system 1 according to this embodiment, a finite system first group G ₁ of the power of the objective optical system 1 without greatly lowering the NA by raising a little according to the second embodiment, the distal end side of the lens The diameter is reduced. Thereby, a less invasive objective optical system can be realized.
Each aberration of the finite objective optical system 1 according to this example under the same conditions as those of the first example is shown in FIGS.

Example 4
Next, a fourth example of the finite objective optical system 1 according to the present embodiment will be described with reference to FIGS.
FIG. 15 shows the arrangement of the lenses of the finite objective optical system 1 according to this example, and Table 4 shows the lens data.

Finite-system objective optical system 1 according to this embodiment is obtained by dividing the parallel plate glass L ₁₁ independent of the first group G1 of a finite-system objective optical system 1 according to the second embodiment in a biconvex lens L ₁₂ is there. By doing so, the biconvex lenses L ₁₂ and L ₅ , the plano-concave lenses L ₂₁ and L ₄₂ , and the plano-convex lenses L ₂₂ and L ₄₁ can be made common parts, and there is an advantage that the manufacturing cost can be reduced.
Each aberration of the finite objective optical system 1 according to the present example under the same conditions as in the first example is shown in FIGS.

  Moreover, in the said Example 1- Example 4, it is clear from Table 5 that the said conditional expression (1)-(9) is satisfy | filled.

It is a whole block diagram which shows a microscope provided with the finite system objective optical system which concerns on one Embodiment of this invention. It is a figure which shows the finite objective optical system which concerns on one Embodiment of this invention. FIG. 3 is a diagram illustrating a lens arrangement of a first example of the finite objective optical system in FIG. 2. It is a figure which respectively shows (a) spherical aberration and (b) astigmatism of the finite system objective optical system of FIG. It is a figure which respectively shows (a) distortion aberration and (b) magnification chromatic aberration of the finite system objective optical system of FIG. It is a figure which respectively shows (a) coma aberration (M) and (b) coma aberration (S) of the finite system objective optical system of FIG. FIG. 4 is a diagram illustrating a lens arrangement of a second example of the finite objective optical system in FIG. 2. FIG. 8 is a diagram showing (a) spherical aberration and (b) astigmatism of the finite objective optical system in FIG. 7, respectively. FIG. 8 is a diagram illustrating (a) distortion and (b) chromatic aberration of magnification of the finite objective optical system in FIG. 7. It is a figure which shows (a) coma aberration (M) and (b) coma aberration (S) of the finite system objective optical system of FIG. 7, respectively. It is a figure which shows the lens arrangement | sequence of the 3rd Example of the finite system objective optical system of FIG. It is a figure which shows (a) spherical aberration and (b) astigmatism of the finite system objective optical system of FIG. 11, respectively. FIG. 12 is a diagram illustrating (a) distortion and (b) lateral chromatic aberration of the finite objective optical system in FIG. 11, respectively. It is a figure which shows (a) coma aberration (M) and (b) coma aberration (S) of the finite system objective optical system of FIG. 11, respectively. It is a figure which shows the lens arrangement | sequence of the 4th Example of the finite system objective optical system of FIG. It is a figure which shows (a) spherical aberration and (b) astigmatism of the finite system objective optical system of FIG. 15, respectively. FIG. 16 is a diagram showing (a) distortion and (b) lateral chromatic aberration of the finite objective optical system of FIG. It is a figure which shows (a) coma aberration (M) and (b) coma aberration (S) of the finite system objective optical system of FIG. 15, respectively.

Explanation of symbols

A Sample (object)
G ₁ 1st group G ₂ 2nd group G ₃ 3rd group G ₄ 4th group G ₅ 5th group L ₃ , L ₅ biconvex lens 1 finite objective optical system

Claims (3)

From the object side, a first group of positive power, a second group including a cemented lens, a third group composed of a biconvex lens, a fourth group including a cemented lens, and a fifth group of positive power And
The finite objective optical system in which the cemented surfaces of the second group and the fourth group have negative refractive power and satisfy the following conditional expressions (1) to (7).
(1) 0.05 <| (1 / F ₂ + 1 / F ₅ ) / (1 / F ₁ + 1 / F ₃ + 1 / F ₅ ) | <0.25
(2) ν _2L <75
(3) 8 <ν _2L −ν _2H <30
(4) 0.05 <n _2H -n _2L <0.15
(5) ν _4L <75
(6) 8 <ν _4L −ν _4H <30
(7) 0.05 <n _4H -n _4L <0.15
here,
F ₁ , F ₂ , F ₃ , F ₄ , F ₅ : first group, second group, third group, fourth group, fifth group focal length,
n _2H : d-line refractive index of the lens having the higher refractive index of the second group,
n _2L : d-line refractive index of the lens having the lower refractive index of the second group,
ν _2H : Abbe number of the lens having the higher refractive index of the second group,
ν _2L : Abbe number of the lens having the lower refractive index of the second group,
n _4H : d-line refractive index of the lens having the higher refractive index of the fourth group,
n _4L : d-line refractive index of the lens having the lower refractive index of the fourth group,
ν _4H : Abbe number of the lens having the higher refractive index of the fourth group,
ν _4L : Abbe number of the lens having the lower refractive index of the fourth group. The finite objective optical system according to claim 1, wherein the third group satisfies the following conditional expression (8).
(8) ν ₃ > 60
Here, ν3 is the Abbe number of the third group. 3. The finite objective optical system according to claim 1, wherein the fifth group is a biconvex lens and satisfies the following conditional expression (9).
(9) 1.5 <| R _5i / R _5o | <2.5
here,
R _5i : radius of curvature of the fifth group on the image side,
R _5o is the radius of curvature of the fifth group on the object side.

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