Objective for a microscope

Abstract

An objective for a microscope includes a displaceable lens group for correcting a spherical aberration. The displaceable lens group is designed in so that an offset of same in the direction perpendicular to the optical axis leads to only a small coma.

Claims

1. An objective, comprising: a plurality of lenses disposed along an optical axis, wherein: the plurality of lenses comprises a lens group that is displaceable along the optical axis; the displaceable lens group has a focal length; the objective is configured so that, during use of the objective, an object produces a first paraxial intermediate image in a half-space upstream of the displaceable lens group and a second paraxial intermediate image in a half-space downstream of the displaceable lens group; the following condition is satisfied for at least one beam ray imaging a point on the optical axis from the first paraxial intermediate image into the second paraxial intermediate image: $\frac{\sin \sigma }{\sin {\sigma }^{\prime }}\times \frac{s^{\prime }p}{s^{\prime }p-\Delta s^{\prime }}-\frac{{\beta }^{″}}{{\beta }^{\prime }}=0;$ σ denotes an angle of inclination of the beam ray imaging the first paraxial intermediate image into the second paraxial intermediate image, upstream of the displaceable lens group; σ′ denotes an angle of inclination of the beam ray imaging the first paraxial intermediate image into the second paraxial intermediate image, downstream of the displaceable lens group; s′p denotes the distance between the second paraxial intermediate image and the intermediate image of the entrance pupil, lying at infinity, in the half-space downstream of the displaceable lens group; Δs′ denotes a longitudinal aberration of the beam ray with respect to the second paraxial intermediate image; β′ denotes a paraxial magnification of the object imaged into the first paraxial intermediate image; β″ denotes a paraxial magnification of the object imaged into the second paraxial intermediate image; and for at least one beam ray imaging a point on the optical axis in the first paraxial intermediate image into the second paraxial intermediate image, the longitudinal aberration Δs′ is greater than or equal to 0.3 times the focal length of the displaceable lens group.

2. The objective of claim 1, wherein the displaceable lens group is configured so that, during use of the objective, a spherical aberration produced by displacing of the displaceable lens group along the optical axis has an absolute value that is identical to a predetermined spherical aberration produced in an object space.

3. The objective of claim 2, wherein a sign of the spherical aberration produced by displacing the displaceable lens group along the optical axis is opposite a sign of the predetermined spherical aberration produced in the object space.

4. The objective of claim 1, wherein the objective is configured so that, during displacement of the lens group along the optical axis, the lens group has a play of no more than 10 micrometers in a direction perpendicular to the optical axis.

5. The objective of claim 1, wherein the displaceable lens group comprises two triple cemented members.

6. The objective of claim 1, wherein the displaceable lens group comprises a triple cemented member and a single lens.

7. The objective of claim 6, wherein: the triple cemented member comprises a central lens; and the single lens and the central lens comprise the same material.

8. The objective of claim 7, wherein: the objective is configured so that, during displacement of the lens group along the optical axis, the lens group has a play of no more than 10 μm in a direction perpendicular to the optical axis; and the displaceable lens group comprises a triple cemented member and a single lens.

9. The objective of claim 1, wherein the displaceable lens group comprises a first triple cemented member, a second triple cemented member, and a single lens along a direction of the beam path.

10. The objective of claim 9, wherein the second triple cemented member is configured so that, during use of the objective, a beam emanating from the object has a waist in a region of the second triple cemented member.

11. The objective of claim 1, wherein the objective has a numerical aperture of at least 0.8.

12. The objective of claim 1, wherein the objective has a magnification of at least 25.

13. The objective of claim 1, wherein displaceable lens group comprises seven lenses (L.sub.4 to L.sub.10) with the following optical design data: TABLE-US-00007 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e L.sub.4 8 14.453 6.200 1.51976 52.14 L.sub.5 9 −9.716 0.950 1.64132 42.20 L.sub.6 10 16.549 4.500 1.53019 76.58 11 −16.549 0.060 L.sub.7 12 15.645 0.900 1.75844 52.08 L.sub.8 13 8.004 7.400 1.43985 94.49 L.sub.9 14 −8.004 0.900 1.75844 52.08 15 93.058 0.170 L.sub.10 16 29.639 4.750 1.43985 94.49

14. The objective of claim 1, wherein the objective has the following design data: TABLE-US-00008 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e DG 1 Infinite Variable 1.52559 54.30 2 Infinite Variable 1.33419 55.88 L.sub.1 3 Infinite 0.820 1.46008 67.68 L.sub.2 4 −0.918 3.710 1.88815 40.52 5 −3.760 0.060 L.sub.3 6 −15.910 3.000 1.59446 98.02 7 −6.633 Variable L.sub.4 8 14.453 6.200 1.51976 52.14 L.sub.5 9 −9.716 0.950 1.64132 42.20 L.sub.6 10 16.549 4.500 1.53019 76.58 11 −16.549 0.060 L.sub.7 12 15.645 0.900 1.75844 52.08 L.sub.8 13 8.004 7.400 1.43985 94.49 L.sub.9 14 −8.004 0.900 1.75844 52.08 15 93.058 0.170 L.sub.10 16 29.639 4.750 1.43985 94.49 17 −10.903 Variable L.sub.11 18 6.774 5.529 1.43985 94.49 L.sub.12 19 −23.884 0.900 1.64132 42.20 20 4.940 4.510 L.sub.13 21 −4.371 0.800 1.59446 68.02 L.sub.14 22 −10.071 2.280 1.72539 34.47 23 6.400 0.287 24 Infinite

15. The objective of claim 1, wherein the displaceable lens group comprises seven lenses (L.sub.4 to L.sub.10) with the following design data: TABLE-US-00009 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e L.sub.4 8 14.277 6.000 1.51976 52.14 L.sub.5 9 −9.858 0.950 1.64132 42.20 L.sub.6 10 17.277 4.150 1.58794 84.07 11 −16.078 0.060 L.sub.7 12 16.908 0.950 1.75844 52.08 L.sub.8 13 7.885 7.650 1.43985 94.49 L.sub.9 14 −7.717 0.950 1.73234 54.45 15 −865.320 0.159 L.sub.10 16 51.212 4.554 1.43985 94.49

16. The objective of claim 1, wherein the objective has the following design data: TABLE-US-00010 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e DG 1 Infinite Variable 1.52559 54.30 2 Infinite Variable 1.33419 55.88 L.sub.1 3 Infinite 0.820 1.46008 67.68 L.sub.2 4 −0.918  3.7350 1.88815 40.52 5 −3.760 0.060 L.sub.3 6 −18.040 3.154 1.59446 68.02 7 −6.876 Variable L.sub.4 8 14.277 6.000 1.51976 52.14 L.sub.5 9 −9.858 0.950 1.64132 42.20 L.sub.6 10 17.277 4.150 1.58794 84.07 11 −16.078 0.060 L.sub.7 12 16.908 0.950 1.75844 52.08 L.sub.8 13 7.885 7.650 1.43985 94.49 L.sub.9 14 −7.717 0.950 1.73234 54.45 15 −865.320 0.159 L.sub.10 16 51.212 4.554 1.43985 94.49 17 −10.592 Variable L.sub.11 18 6.895 5.869 1.43985 94.49 L.sub.12 19 −22.548 0.900 1.64132 42.20 20 4.940  4.4036 L.sub.13 21 −4.371 1.000 1.59446 68.02 L.sub.14 22 −9.039 2.070 1.72539 34.47 23 −6.312 0.220 24 Infinite

17. The objective of claim 1, wherein: the objective is configured so that, during displacement of the lens group along the optical axis, the lens group has a play of no more than 10 μm in a direction perpendicular to the optical axis; and the displaceable lens group comprises two triple cemented members.

18. The objective of claim 1, wherein: the displaceable lens group is configured so that, during use of the objective, a spherical aberration produced by displacing of the displaceable lens group along the optical axis has an absolute value that is identical to a predetermined spherical aberration produced in an object space; and the objective has a numerical aperture of at least 0.8.

19. The objective of claim 1, wherein: the displaceable lens group is configured so that, during use of the objective, a spherical aberration produced by displacing of the displaceable lens group along the optical axis has an absolute value that is identical to a predetermined spherical aberration produced in an object space; and the objective has a magnification of at least 25.

20. A microscope, comprising: an objective according to claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further details and advantages of the disclosure will become apparent from the description of exemplary embodiments with reference to the figures, in which:

(2) FIG. 1 shows, schematically and in simplified form, the profile of a few beam rays for paraxial imaging of an object y into an intermediate image y′ upstream of the correction group and for imaging the intermediate image y′ into an intermediate image y″ in the space downstream of the correction group, for the purposes of explaining the disclosure;

(3) FIG. 2 shows a schematic longitudinal section through the optical components of an objective according to a first variant;

(4) FIG. 3 schematically shows the beam path for imaging the paraxial intermediate image y′ in the space upstream of the correction group into the paraxial intermediate image y″ in the space downstream of the correction group, for the correction group of the objective according to FIG. 2;

(5) FIG. 4 shows the dependence of the parameter A, defined above, on the sine of the inclination of the beam ray for imaging y′ into y″ in the objective according to FIG. 2;

(6) FIG. 5 shows a schematic longitudinal section through the optical components of an objective according to a first variant;

(7) FIG. 6 schematically shows the beam path for imaging the paraxial intermediate image y′ in the space upstream of the correction group into the paraxial intermediate image y″ in the space downstream of the correction group, for the correction group of the objective according to FIG. 5; and

(8) FIG. 7 shows the dependence of the parameter A, defined above, on the sine of the inclination of the beam ray for imaging y′ into y″ in the objective according to FIG. 5.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) For the purposes of describing the disclosure, paraxial imaging of an object y into a first paraxial intermediate image y′ in the half-space upstream of the correction group 2 and imaging the object y into a second paraxial intermediate image y″ in the half-space downstream of the correction group 2 and imaging the first intermediate image y′ into the second intermediate image y″ are explained first. Here, an aberration-free intermediate image y′ is assumed.

(10) Moreover, the position of the image AP of the entrance pupil, lying at infinity, is illustrated in FIG. 1.

(11) Moreover, FIG. 1 illustrates the position of the front side Fl.sub.3 the front-most lens L.sub.1 of the objective 1. In particular, the two principal planes of the front objective part are illustrated schematically in FIG. 1.

(12) Further, the following labels are used in FIG. 1: oA: Optical axis of the objective 1; σ°: Angle of inclination of a marginal ray 3 of the beam for imaging y′ onto y″, relative to the optical axis; σ: Angle of inclination of a beam ray 4 of the beam for imaging y′ onto y″, relative to the optical axis in the space upstream of the correction group 2; the following holding true: 0≤σ≤σ°; σ′: Angle of inclination of a beam ray 4 of the beam for imaging y′ onto y″, relative to the optical axis in the space downstream of the correction group 2; Δs′: Longitudinal aberration of the beam ray 4 in relation to the position of the second paraxial intermediate image y″; and s′p: Distance between the second paraxial intermediate image y″ and the position of the image AP of the entrance pupil.

(13) Further, β′ denotes the paraxial magnification when imaging the object y into the half-space upstream of the correction group 2, and β″ denotes the paraxial magnification when imaging the object y into the half-space downstream of the correction group 2.

(14) F′ denotes the focal length of the correction group 2.

(15) A dimensionless parameter

(16) $A=\frac{\sin \sigma }{\sin {\sigma }^{\prime }}\times \frac{{s^{\prime }}_p}{{s^{\prime }}_p-\Delta s^{\prime }}-\frac{{\beta }^{″}}{{\beta }^{\prime }}$
can be defined from the quantities listed above.

(17) For the objective 1, still to be described in more detail below, the following applies to at least one beam ray 4, i.e., to at least one value of σ between 0 and σ°: A=0 and, for at least one beam ray 4: Δs′≥0.3 F′. Here, the two conditions need not necessarily relate to the same beam ray.

(18) A first variant of the objective 1 is described in detail below, with reference being made to FIGS. 2 and 3.

(19) To provide a better overview, mechanical constituent parts of the objective 1 are not illustrated in the figures.

(20) The figure illustrates the profiles of chief rays HS and marginal rays RS1, RS2 at different wavelengths for an object point lying slightly off axis.

(21) Moreover, a cover slip DG is illustrated in the figure.

(22) In particular, the objective 1 is an immersion objective. In particular, this is an apochromatic objective.

(23) The objective 1 includes 14 lenses L.sub.1 to L.sub.14.

(24) The lenses L.sub.4 to L.sub.10 form the correction group 2. In particular, they are displaceable in the direction of the optical axis oA.

(25) The front-most lens L.sub.1 has a planar front side Fl.sub.3. In particular, it can be manufactured from a material that has a refractive index ne in the range of 1.3 to 1.6 at a wavelength of e=546 nm. In particular, it can be manufactured from a glass with a refractive index ne of 1.46008.

(26) Two double cemented members are disposed in the beam path downstream of the correction group 2.

(27) The correction group 2 includes seven lenses L.sub.4 to L.sub.10.

(28) In particular, the lenses L.sub.4 to L.sub.6 of the correction group 2 form a first triple cemented member. The lens L.sub.4 has a biconvex embodiment. The lens L.sub.5 has a biconcave embodiment. The lens L.sub.6 has a biconvex embodiment. In particular, the lens L.sub.6 has a mirror-symmetric embodiment. In terms of absolute value, its front side Fl.sub.10 and its back side Fl.sub.11 have the same radius of curvature.

(29) The lenses L.sub.7 to L.sub.9 form a second triple cemented member. The lens L.sub.7 is embodied as a meniscus lens. The lens L.sub.8 has a biconvex embodiment. The lens L.sub.8 has a symmetric embodiment. In terms of absolute value, its front side Fl.sub.13 and its back side Fl.sub.14 have the same radius of curvature.

(30) The beam path in the objective 1 has a waist in the region of the second triple cemented member, in particular in the region of the lens L.sub.8.

(31) The lens L.sub.9 has a biconcave embodiment.

(32) The single lens L.sub.10 has a biconvex embodiment.

(33) The lenses L.sub.8 and L.sub.10 are manufactured from the same glass.

(34) The lenses L.sub.7 and L.sub.9 are manufactured from the same glass.

(35) The design data of the objective 1 according to FIG. 2 are once again listed in detail in Table 1.

(36) TABLE-US-00001 TABLE 1 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e DG 1 Infinite Variable 1.52559 54.30 2 Infinite Variable 1.33419 55.88 L.sub.1 3 Infinite 0.820 1.46008 67.68 L.sub.2 4 −0.918 3.710 1.88815 40.52 5 −3.760 0.060 L.sub.3 6 −15.910 3.000 1.59446 98.02 7 −6.633 Variable L.sub.4 8 14.453 6.200 1.51976 52.14 L.sub.5 9 −9.716 0.950 1.64132 42.20 L.sub.6 10 16.549 4.500 1.53019 76.58 11 −16.549 0.060 L.sub.7 12 15.645 0.900 1.75844 52.08 L.sub.8 13 8.004 7.400 1.43985 94.49 L.sub.9 14 −8.004 0.900 1.75844 52.08 15 93.058 0.170 L.sub.10 16 29.639 4.750 1.43985 94.49 17 −10.903 Variable L.sub.11 18 6.774 5.529 1.43985 94.49 L.sub.12 19 −23.884 0.900 1.64132 42.20 20 4.940 4.510 L.sub.13 21 −4.371 0.800 1.59446 68.02 L.sub.14 22 −10.071 2.280 1.72539 34.47 23 6.400 0.287 24 Infinite

(37) In conjunction with the tube lens described below in Table 2, the objective 1 has a 40× magnification. The objective 1 has a numerical aperture of 1.2. The objective 1 has an object field size of 0.625 mm. The objective 1 has a focal length of 4.12 mm. The objective 1 has a distance from the first tube lens of 126.50 mm.

(38) A selection of the details for designing the tube lens unit provided for the objective 1 are summarized in Table 2 below.

(39) TABLE-US-00002 TABLE 2 Radius of Surface curvature r Thickness d Refractive Abbe No. [mm] [mm] index n.sub.e number v.sub.e 1 189.417 10.900 1.58212 53.59 2 −189.417 60.000 7 Infinite 80.000 1.51872 63.96 8 Infinite 48.200 9 Intermediate image plane

(40) The tube lens unit has a focal length of 164.5 mm.

(41) Table 3 specifies displacement data for the correction group 2 when using cover slips with different thicknesses.

(42) TABLE-US-00003 TABLE 3 Thin cover Normal cover Thick cover Variant slip slip slip Thickness 1 (DG) 0.130 0.170 0.200 [mm] Thickness 2 (Distance) 0.311 0.281 0.259 [mm] Thickness 7 [mm] 0.347 0.253 0.173 Thickness 17 [mm] 0.036 0.130 0.210

(43) The lenses L.sub.1 to L.sub.3 and L.sub.11 to L.sub.14 remain stationary relative to one another when the correction group 2 is displaced. The sum of the distances d.sub.7 and d.sub.17 is constant.

(44) When use is made of a cover slip with a thickness of 0.170 mm, the magnification β′ when imaging the object y into the first paraxial intermediate image y′ is 4.177. With the further values specified in Table 3, the distance b′ from the first paraxial intermediate image y′ to the correction group 2, in particular to the front side Fl.sub.8 of the lens L.sub.4, is −21.058 mm.

(45) The magnification β″ when imaging the object y into the second paraxial intermediate image y″ in the half-space downstream of the correction group 2 is −7.273. The distance between the second paraxial intermediate image y″ and the correction group 2, in particular the back side Fl.sub.17 of the lens L.sub.10, is 40.887 mm.

(46) The distance between the image AP of the entrance pupil and the second paraxial intermediate image y″ is −47.774 mm.

(47) FIG. 4 illustrates the dependence of the parameter A on the sine of the ray inclination of a beam ray for imaging y′ onto y″. The curve has a zero at σ≈16°.

(48) The longitudinal aberration Δs′ of the marginal ray 3 is 7.66 mm. The focal length f′ of the correction group 2 of the objective 1 is 19.87 mm. Hence, Δs′>0.3 f′ applies.

(49) In-depth analysis has shown that the correction group 2 is in fact insensitive to an offset in the direction perpendicular to the optical axis.

(50) A further variant of the objective 1 is described below, with reference being made to FIGS. 5 and 6.

(51) To provide a better overview, mechanical constituent parts of the objective 1 are not illustrated in the figures. With respect to general details, reference is made to the description of the objective according to FIGS. 2 and 3.

(52) The objective 1 includes 14 lenses L.sub.1 to L.sub.14.

(53) The lenses L.sub.4 to L.sub.10 form the correction group 2. In particular, they are displaceable in the direction of the optical axis oA.

(54) The front-most lens L.sub.1 has a planar front side Fl.sub.3. In particular, it can be manufactured from a material that has a refractive index ne in the range of 1.3 to 1.6 at a wavelength of e=546 nm. In particular, it can be manufactured from a glass with a refractive index ne of 1.46008.

(55) Two double cemented members are disposed in the beam path downstream of the correction group 2.

(56) The correction group 2 includes seven lenses L.sub.4 to L.sub.10.

(57) In particular, the lenses L.sub.4 to L.sub.6 of the correction group 2 form a first triple cemented member. The lens L.sub.4 has a biconvex embodiment. The lens L.sub.5 has a biconcave embodiment. The lens L.sub.6 has a biconvex embodiment. The absolute values of the radii of curvature of its front side Fl.sub.10 and its back side Fl.sub.11 deviate from one another by less than 10%.

(58) The lenses L.sub.7 to L.sub.9 form a second triple cemented member. The lens L.sub.7 is embodied as a meniscus lens. The lens L.sub.8 has a biconvex embodiment. The absolute values of the radii of curvature of its front side Fl.sub.13 and its back side Fl.sub.14 deviate from one another by less than 10%, in particular by less than 5%, in particular by less than 3%, in particular by less than 2%.

(59) The beam path in the objective 1 has a waist in the region of the second triple cemented member, in particular in the region of the lens L.sub.8.

(60) The lens L.sub.9 has a biconcave embodiment.

(61) The single lens L.sub.10 has a biconvex embodiment.

(62) The lenses L.sub.8 and L.sub.10 are manufactured from the same glass.

(63) The design data of the objective 1 according to FIG. 5 are once again listed in detail in Table 4.

(64) TABLE-US-00004 TABLE 4 Radius of Area curvature r Thickness d Refractive Abbe FL [mm] [mm] index n.sub.e number v.sub.e DG 1 Infinite Variable 1.52559 54.30 2 Infinite Variable 1.33419 55.88 L.sub.1 3 Infinite 0.820 1.46008 67.68 L.sub.2 4 −0.918  3.7350 1.88815 40.52 5 −3.760 0.060 L.sub.3 6 −18.040 3.154 1.59446 68.02 7 −6.876 Variable L.sub.4 8 14.277 6.000 1.51976 52.14 L.sub.5 9 −9.858 0.950 1.64132 42.20 L.sub.6 10 17.277 4.150 1.58794 84.07 11 −16.078 0.060 L.sub.7 12 16.908 0.950 1.75844 52.08 L.sub.8 13 7.885 7.650 1.43985 94.49 L.sub.9 14 −7.717 0.950 1.73234 54.45 15 −865.320 0.159 L.sub.10 16 51.212 4.554 1.43985 94.49 17 −10.592 Variable L.sub.11 18 6.895 5.869 1.43985 94.49 L.sub.12 19 −22.548 0.900 1.64132 42.20 20 4.940  4.4036 L.sub.13 21 −4.371 1.000 1.59446 68.02 L.sub.14 22 −9.039 2.070 1.72539 34.47 23 −6.312 0.220 24 Infinite

(65) In conjunction with the tube lens described below in Table 5, the objective 1 has a 40× magnification. The objective 1 has a numerical aperture of 1.2. The objective 1 has an object field size of 0.625 mm. The objective 1 has a focal length of 4.12 mm. The objective 1 has a distance from the first tube lens of 126.50 mm.

(66) A selection of the details for designing the tube lens unit provided for the objective 1 are summarized in Table 5 below.

(67) TABLE-US-00005 TABLE 5 Radius of Surface curvature r Thickness d Refractive Abbe No. [mm] [mm] index n.sub.e number v.sub.e 114.400 1 189.417 10.900 1.58212 53.59 2 −189.417 60.000 7 Infinite 80.000 1.51872 63.96 8 Infinite 48.200 9 Intermediate image plane

(68) The tube lens unit has a focal length of 164.5 mm.

(69) Table 6 specifies displacement data for the correction group 2 when using cover slips with different thicknesses.

(70) TABLE-US-00006 TABLE 6 Thin cover Normal cover Thick cover Variant slip slip slip Thickness 1 (DG) 0.140 0.170 0.190 [mm] Thickness 2 (Distance) 0.303 0.281 0.266 [mm] Thickness 7 [mm] 0.316 0.239 0.181 Thickness 17 [mm] 0.106 0.183 0.241

(71) The lenses L.sub.1 to L.sub.3 and L.sub.11 to L.sub.14 remain stationary relative to one another when the correction group 2 is displaced. The sum of the distances d.sub.7 and d.sub.17 is constant.

(72) When use is made of a cover slip with a thickness of 0.170 mm, the magnification β′ when imaging the object y into the first paraxial intermediate image y′ is 4.325. With the further values specified in Table 6, the distance b′ from the first paraxial intermediate image y′ to the correction group 2, in particular to the front side Fl.sub.8 of the lens L.sub.4, is −21.974 mm.

(73) The magnification β″ when imaging the object y into the second paraxial intermediate image y″ in the half-space downstream of the correction group 2 is −7.257. The distance between the second paraxial intermediate image y″ and the correction group 2, in particular the back side Fl.sub.17 of the lens L.sub.10, is 42.001 mm.

(74) The distance between the image AP of the entrance pupil and the second paraxial intermediate image y″ is −51.100 mm.