JP6546544B2 - Objective lens and microscope - Google Patents

Description

  The present invention relates to an objective lens and a microscope.

  In the case of an epi-illumination dark field illumination (also referred to as “epi-dark illumination”), a ring-shaped luminous flux whose center coincides with the optical axis of the lens system from the periphery of the lens system that forms an image of reflected light from a specimen , And guides the luminous flux onto the sample by a condensing member (for example, a perforated paraboloid mirror) provided near the tip of the lens system. Here, the whole including the dark field illumination optical system is referred to as an "objective lens", and the inner lens system contributing to image formation is referred to as an "objective optical system". In recent years, the objective lens has been increasing in numerical aperture and working distance, and the outer diameter of the lens of the objective optical system tends to be larger along with this, so that it is standard in the conventional epi-illumination type microscope It is difficult to perform effective dark field illumination with the illumination system (ring light flux supply system) equipped with the Therefore, an outward deflection member, an inward deflection member, and a light collection member, which are disposed concentrically with the optical axis of the objective optical system, can be provided to enable incident dark field illumination corresponding to the objective optical system having a large aperture. An objective lens for incident dark field illumination is disclosed (see, for example, Patent Document 1).

  In addition, although the objective optical system has a large diameter for high numerical aperture and long working distance, the outer lens barrel has limitations, so the space that can be used for light flux for dark field is limited. It is necessary to dispose the optical member of the dark field illumination optical system in the space, and the placement is difficult, and the light is incident in the optical path between the optical members (deflection member, light collecting member) disposed around the objective optical system. The light beam having an angle (a light beam other than a light beam parallel to the optical axis at the time of incidence) strikes the inner wall surface of a lens barrel provided around the optical member and is reflected to the outside of the light path to cause loss of light quantity. In particular, in the dark field illumination optical system, the pupil position of the incident light beam is generally located at a distance from the objective lens. For example, a diaphragm in the vicinity of a perforated mirror that separates the illumination light and the imaging light It often corresponds. In this case, since the pupil position is apart in the radial afocal system, the light beam having the angle spreads, and the light amount loss easily occurs.

Japanese Examined Patent Publication No. 4-048203

  In the dark-field observation with a microscope, it is necessary to supply strong illumination light because of the characteristics of the observation method. Therefore, if the light quantity of the illumination light can not be secured sufficiently, the problem is that good dark-field observation can not be performed. is there.

  The present invention has been made in view of such problems, and it is also possible to reduce the light quantity loss and supply effective epi-illumination dark-field illumination to an objective optical system having a high numerical aperture and a long working distance. It is an object of the present invention to provide an objective lens of a possible configuration and a microscope provided with this objective lens.

In order to solve the above problems, an objective lens according to the present invention is an objective lens having an objective optical system, a light shielding member, an objective lens case, and a dark field optical system, wherein the dark field optical system Has a first optical member and a second optical member, and the first optical member condenses incident light at a condensing position between the first optical member and the second optical member And the second optical member deflects the light diverging from the light collecting position and irradiates the specimen with the light shielding member, the first light shielding portion and the first light shielding portion with respect to the specimen side. The second light-shielding portion provided in the second light-shielding portion, and the surface of the second light-shielding portion facing the objective lens housing is smaller than the surface of the first light shielding portion facing the objective lens housing Provided on an objective lens housing side, the first optical member is a space between the first light shielding portion and the objective lens housing It is located.
A microscope according to the present invention is characterized by having the above-described objective lens.

  According to the present invention, an objective lens configured to be capable of providing effective incident dark field illumination with reduced light amount loss even for a high numerical aperture, long working distance objective optical system, and this objective lens Can be provided with a microscope.

It is an explanatory view showing composition of a microscope. It is an explanatory view showing a part of composition of a microscope. It is explanatory drawing which shows the structure of the objective lens which concerns on 1st Example. It is explanatory drawing which shows the structure of a 1st optical member, Comprising: (a) shows a front view, (b) shows IIIb-IIIb sectional drawing. It is explanatory drawing which shows the structure of the objective lens which concerns on 2nd Example. It is explanatory drawing which shows the structure of the dark field illumination system which concerns on 3rd Example.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the microscope 1 according to the present embodiment includes a lamp house 11 storing a light source, an illumination optical system 12, a revolver 19, and an objective lens 30 attached to the revolver 19. , And an imaging optical system 17 having an objective optical system 31 and a second objective lens 23 stored in the objective lens 30, and an optical path between the illumination optical system 12 and the imaging optical system 17 so as to be insertable and removable. A mirror block 13 including a dark field lens 21 and a dark field observation mirror (hereinafter referred to as "dark field block 13"), and an eyepiece lens 18 for observing an image formed by the imaging optical system 17. , And a stage 15 on which the sample 16 is placed.

  As shown in FIG. 2, the illumination light from the lamp house 11 is converted into a ring-shaped luminous flux by the illumination optical system 12 and the dark field lens 21 included in the dark field block 13 and enters the dark field hollow mirror 22. . The light beam reflected by the dark field hollow mirror 22 is transmitted from the tip of the objective lens 30 through the dark field illumination optical system 35 disposed so as to surround the objective optical system 31 in the objective lens 30. The specimen 16 is obliquely irradiated from the outer peripheral portion. The observation light from the sample 16 is collimated by the objective optical system 31 into a substantially parallel light beam, condensed by the second objective lens 23, imaged on the primary image plane 24, and observed by the eyepiece lens 18. Incidentally, by attaching a mirror block 41 for bright field observation having a half mirror 42 to the microscope 1 instead of the dark field block 13, bright field observation becomes possible.

  Now, the configuration of such an objective lens 30 and the dark field illumination optical system 35 disposed in the objective lens 30 will be described using FIG. 3 to FIG. 5 together. The objective lens 30 according to the present embodiment is disposed so as to surround the cylindrical light shielding member 32 in which the objective optical system 31 is stored, and the light shielding member 32, as shown in FIGS. An objective lens housing 34 for forming a space (hereinafter, referred to as “dark-field optical path 33”) around the light shielding member 32, and a dark-field illumination optical system 35 disposed in the dark-field optical path 33 , Composed of In addition, the dark field illumination optical system 35 is configured of a first optical member 36 disposed on the light source side and a second optical member 37 disposed on the sample side tip. The ring-shaped illumination light beam reflected by the dark field hollow mirror 22 described above is guided from the light source side of the objective lens 30 into the dark field optical path 33, and the first optical member 36 of the dark field illumination optical system 35. Incident to

  The first optical member 36 has a ring shape when viewed from the light source side as shown in FIG. 4A, and the optical axis AX of the objective optical system 31 of the objective lens 30 (the light of the imaging optical system 17 So that at least one of the two surfaces R1 and R2 extending in the radial direction of the circle has a positive refracting power when the optical axis AX is at the center of the circle in the section including the axis) It is constructed and has positive refractive power as a whole. For example, in FIG. 4B, these surfaces R1 and R2 are formed by two arcs having vertices on a symmetry axis SAX extending substantially in parallel from the optical axis AX of the objective optical system 31 at a distance h2. A toroidal lens formed as a locus obtained by rotating these circular arcs about the optical axis AX is used. The first optical member 36 shown in FIG. 3 has a convex surface on the light source side and a flat surface on the sample side. Besides this, the surface on the light source side may be convex, and the surface on the sample side may be concave, or the surface on the light source side may be concave and the surface on the sample side may be convex. Furthermore, the cross-sectional shape of the surfaces R1 and R2 of the first optical member 36 may be any line other than a circular arc as long as it is line symmetrical with respect to the axis SAX, and may be a hyperbolic curve, a parabola, an elliptical shape, or a high order aspheric surface.

  As described above, the first optical member 36 has a positive refractive power in the radial direction of a circle centered on at least the optical axis AX of the objective optical system 31, and the illumination light flux (ring shape Light flux) in the radial direction. Since the first optical member 36 has a shape of a locus obtained by rotating the cross-sectional shape shown in FIG. 4B about the optical axis, there is no refractive power in the circumferential direction (the focal length is Infinity). Here, as shown in FIG. 3, in the objective lens 30 according to the present embodiment, most of the illumination light flux passes through the inner portion (portion on the optical axis side) of the ring-shaped first optical member 36. It is configured. That is, the distance h2 is configured to be larger than the central radius of the ring-like light beam (the distance from the optical axis AX to the center of the ring-like light beam). Therefore, in an arbitrary cross section including the optical axis AX of the objective optical system 31, the first optical member 36 has the light beam on the side closest to the optical axis AX among the light fluxes in the radial direction larger than the light farthest from the optical axis AX. And light in the most optical axis side (inner side) is radially refracted away from the optical axis AX. Thereby, as shown in FIG. 3 or FIG. 5, the light shielding member 32 is formed in a double cylindrical shape, for example, when a lens with a large aperture is disposed in the middle part of the objective optical system 31. Even if the dark field optical path 33 is narrowed, the light flux can pass through the narrowed dark field optical path 33 without interfering with the step 32a.

  On the other hand, the second optical member 37 deflects the light beam emitted from the first optical member 36 in the direction of the optical axis AX to irradiate a predetermined illumination area including the optical axis AX on the sample surface 16 a of the sample 16. It is configured. As shown in FIG. 3, this second optical member 37 has a perforated mirror (reflection surface 37 a that has a reflection surface 37 a that is a concave surface of a high-order aspheric shape whose central axis is the optical axis AX of the objective optical system 31). A concave surface formed in a high-order aspheric shape, and a mirror in which a cylindrical opening 37b is formed in a portion including the optical axis, or, as shown in FIG. 5, at least one lens surface is aspheric A lens formed into a shape, and having a cylindrical opening at a portion including the optical axis is used. In addition, since it is necessary to design this second optical member 37 in accordance with the working distance and numerical aperture of the objective lens 30 (objective optical system 31), it is difficult to share the objective lenses having different magnifications.

  According to the dark field illumination optical system 35 having such a configuration, the illumination light collected in the radial direction by the first optical member 36 is once collected at the light collection position B in the radial direction of the first optical member 36. Then, it becomes divergent light and is incident on the second optical member 37. Then, the light is reflected or refracted by the second optical member 37, deflected in the direction of the optical axis AX of the objective optical system 31, and irradiated onto the sample surface 16a.

  In order to miniaturize the dark field illumination optical system 35, the radial focusing position B of the illumination light focused by the first optical member 36 is the first optical member 36 and the second optical member. It is desirable that the distance between the first optical member 36 and the second optical member 37 be greater than one-third of the distance between the first optical member 36 and the second optical member 37 with the first optical member 36 as a base point. In general, the first optical member 36 is disposed in the vicinity of the cylinder attachment surface, and the second optical member 37 is disposed at the position where the working distance can be secured. Therefore, it is desirable that the dark field illumination optical system 35 satisfy the condition of the following expression (1). When the objective lens 30 is configured as described above, the illumination light flux becomes the narrowest at a portion where the diameter of the objective optical system 31 becomes large, and the light collecting position B away from the optical axis AX is located, thereby increasing the efficiency of the illumination light. It is because it can be well led to the sample surface 16a.

1/3 ≦ fr / (fp−WD) <1 (1)
However,
fr: radial focal length of first optical member 36 fp: same focal length of objective lens 30 WD: working distance of objective lens 30

  In the conditional expression (1), the working distance represents the distance from the tip of the objective lens 30 to the sample surface 16a, and the same focal length is the cylinder attachment surface 34a (when the objective lens 30 is attached to the revolver 19) Of the sample surface 16a). Further, the focal length (the same focal length and the focal length in the radial direction) is a value for the main wavelength used in the objective lens 30. That is, when the objective lens 30 is used for visible light, the main wavelength is d-line, and when it is used for near infrared light or ultraviolet light, the main wavelength corresponding to that is used. The radial focal length fr of the first optical member 36 has the following relationship (2).

但し、
Ｒｒ１：光源側面Ｒ１の径方向の曲率半径
Ｒｒ２：標本側面Ｒ２の径方向の曲率半径
ｄ：面Ｒ１，Ｒ２の軸ＳＡＸ上の距離
ｎ：媒質の主波長に対する屈折率

However,
Rr1: Radius of curvature radius of light source side surface R1 Rr2: Radius of radius of curvature of specimen side R2 d: Distance on the axis SAX of the surfaces R1, R2 n: Index of refraction with respect to the main wavelength of the medium

  Further, as described above, since the passing area of the ring-shaped illumination light is biased to the inner area (portion on the optical axis side) of the ring-shaped first optical member 36, the first optical member 36 It can be miniaturized by making it the shape which the outside part (part of the broken line of FIG. 4) which does not pass through is scraped off.

  In the above description, the case where each of the first optical member 36 and the second optical member 37 is configured as a rotationally symmetric shape with the optical axis AX of the objective optical system 31 of the objective lens 30 as the rotation axis has been described. This is because the illumination light beam incident on the dark field illumination optical system 35 has a ring shape. However, the illumination beam is not limited to this ring shape. For example, a combination of a plurality of light sources (for example, an LED or an end face of an optical fiber for guiding light from a light source device) and a micro lens for collimating illumination light from the light source Are arranged along the ring-shaped opening, and illumination light from each light source is irradiated onto the sample surface 16a by the dark field illumination optical system 35 including the first optical member 36 and the second optical member 37. You may. In this case, the first and second optical members 36 and 37 may be arranged along the circumference only at the portion through which the illumination light passes among the members of the rotationally symmetric shape.

  As described above, even when the second optical member 37 is formed of a plurality of optical members, it is included in the perforated mirror or the perforated lens in Examples 1 and 2 described later.

  Hereinafter, examples of the dark field illumination optical system 35 provided in the objective lens 30 will be described based on the drawings. 3, 5 and 6 show the configurations of the first to third embodiments.

[First embodiment]
FIG. 3 is a cross-sectional view showing the configuration of the objective lens 30 having the dark field illumination optical system 35 according to the first embodiment. The objective lens 30 according to the first embodiment is a high power objective lens. In the objective lens 30, the dark field illumination optical system 35 sequentially arranges, from the light source side, a ring-shaped illumination light beam incident from the surface (surface R1 in FIG. 4B) on the light source side (optical axis AX). The first optical member 36 that condenses in the radial direction of the circle when it is the center of the circle, and the illumination light flux collected by the first optical member 36 are deflected in the optical axis direction of the objective optical system 31 And a second optical member 37 for irradiating a predetermined illumination area of the sample surface 16a. Here, the first optical member 36 refracts the illumination light flux so that the light beam inside in the radial direction is separated from the optical axis AX of the objective optical system 31, and the first optical member 36 and the second optical member 37 It is comprised so that it may condense light at the condensing position B between. Further, the second optical member 37 is a perforated mirror formed by a part of a high-order aspheric surface having an apex on the optical axis AX of the objective optical system 31. Since the objective lens 30 according to the first embodiment is an objective lens with a high magnification, the second optical member 37 has the above-described high-order non-linearity as the second optical member 37 to condense illumination light on a narrow illumination area on the sample surface 16a. The illumination light flux which has become divergent light from the above-described focal position B is collected using a spherical mirror and configured to be irradiated onto the sample surface 16a.

  Table 1 below shows values of various items of the dark field illumination optical system 35 according to the first embodiment. In Table 1, f, NA, WD and β respectively indicate the focal length, numerical aperture, working distance and magnification of the objective lens 30 (objective optical system 31). Further, h2 represents the distance from the optical axis AX of the objective optical system 31 (imaging optical system 17) to the symmetry axis SAX of the surfaces R1 and R2 of the first optical member 35. Further, m indicates the number (surface number) of each optical surface along the traveling direction of the light beam, r indicates the radius of curvature (may be the radius of curvature in the radial direction) of each optical surface, and d indicates each optical Indicates the distance on the optical axis AX (sometimes on the symmetry axis SAX) from the surface to the next optical surface, nd indicates the refractive index to the d-line of the medium, and d d indicates the Abbe number (= (nd-1) / (NF-nC)) is shown. Here, nF and nC represent the refractive index to the F line and the C line, respectively.

Here, the aspheric surface has a height in the direction perpendicular to the optical axis as y, and the distance (sag amount) along the optical axis from the tangent plane of the vertex of each aspheric surface at height y to each aspheric surface is S Assuming that the radius of curvature (paraxial radius of curvature) of the reference spherical surface is r, the conic constant is K, and the n-th-order aspheric coefficient is An, the following equation (3) is used. Therefore, in the following data tables, for aspheric surfaces, aspheric surface data, that is, the values of the conical constant K and the respective aspheric constants A4 to A8 are shown. Here, “E-n” indicates “× 10 ⁻ⁿ ”.

^{S (y) = (y 2} / r) / [1+ {1- (1 + K) (y 2 / r 2)} 1/2]
+ A 4 x y ⁴ + A 6 x y ⁶ + A 8 x y ⁸ (3)

  In the tables of the respective embodiments, an aspheric surface (a surface whose shape is represented by the aspheric surface expression (3)) is given an asterisk * on the right side of the surface number.

  In addition, although the unit of curvature radius r, surface separation d, and other lengths listed in all the specification values below is generally “mm”, the optical system is equivalent even if it is scaled up or down proportionally The optical performance of is not limited to this. In addition, the refractive index 1.00000 of air is omitted. The above description is the same in the following specification tables.

(Table 1)
f = 2 mm
NA = 0.8
WD = 4.5 mm
β = 100x
h2 = 14.2 mm

m r d nd d d
Light source surface ∞ ∞
1 17.00000 3.500000 1.5251 56
2 6 62.900000
3 * -9.20000 -4.400000
Sample plane ∞

Aspheric data
K A4 A6 A8
Third surface -0.900000 0.100000E-03 -0.340000E-06 0.350000E-09

  The surface numbers 1 to 3 shown in Table 1 correspond to the numbers 1 to 3 shown in FIG. Specifically, the first surface corresponds to the surface on the light source side of the first optical member 36 (the surface R1 in FIG. 4B), and the second surface corresponds to the surface on the sample side of the first optical member 36 (FIG. 4) It corresponds to the surface R2) of (b). The radius of curvature r in the first surface and the second surface is shown as an arc centered on a symmetry axis SAX extending substantially in parallel from the optical axis AX of the objective optical system 31 by a distance h2, Is indicated as a distance from a position where the vertex of each surface on the symmetry axis SAX is lowered perpendicularly to the optical axis AX. The radius of curvature r shown on the first surface and the second surface of Table 1 is a value in the radial direction of a circle centered on the optical axis AX, and the circumferential direction is infinite. The third surface corresponds to the reflection surface 37 b of the second optical member 36. The third surface is a part of the surface obtained by rotating the curve represented by the aspheric surface data shown in Table 1 and the aspheric surface formula (3) around the optical axis AX of the objective optical system 31 as a central axis. The apex of the aspheric reference sphere is located farther from the light source than the sample surface 16 on the optical axis AX. In FIG. 3, an aspheric surface, a part of which forms the third surface, is indicated by a broken line. The sample surface 16a is also a plane (curvature radius r = r).

  When the dark field illumination optical system 35 according to the first embodiment and the objective lens 30 having the illumination optical system are configured as described above, it is possible to minimize the light amount loss of the illumination light and achieve efficient illumination. . Further, the number of parts is small, and cost reduction can be achieved.

Second Embodiment
FIG. 5 is a cross-sectional view showing the configuration of the objective lens 30 having the dark field illumination optical system 35 according to the second embodiment. The objective lens 30 according to the second embodiment is a low power objective lens. In the objective lens 30, the dark field illumination optical system 35 radially condenses the ring-shaped illumination light flux incident from the light source side surface (surface R1 in FIG. 4B) from the light source side. 1 optical member 36, and a second optical member 37 for deflecting the illumination light beam collected by the first optical member 36 in the direction of the optical axis of the objective optical system 31 and irradiating a predetermined illumination area of the sample surface 16a , Is composed of. Here, the first optical member 36 is the same member as that of the first embodiment, and in an arbitrary cross section including the optical axis AX of the objective optical system 31, the light on the optical axis AX side of the luminous flux is the most light While refracting in the radial direction more than light away from the axis AX, the light (inner side in the radial direction) on the optical axis side (inner side) is refracted away from the optical axis AX of the objective optical system 31, It is configured to once condense light at a condensing position B between the first optical member 36 and the second optical member 37. The second optical member 37 is a holed lens whose lens surface is part of a lens having a vertex on the optical axis AX of the objective optical system 31 and whose surface on the light source side has a high-order aspheric shape. Yes (the sample side is a paraboloid).

  Table 2 below shows values of various items of the dark field illumination optical system 35 according to the second embodiment.

(Table 2)
f = 10 mm
NA = 0.4
WD = 19 mm
β = 20x
h2 = 14.2 mm

m r d nd d d
Light source surface ∞ ∞
1 17.00000 3.500000 1.5251 56
2 2 28.100000
3 * 17.00000 12.000000 1.5251 56
4 * -41.00000 18.400000
Sample plane ∞

Aspheric data
K A4 A6 A8
Third surface -1.000000 -0.200000E-05 -0.200000E-07 0.000000E + 00
Fourth side -1.000000 0.000000E + 00 0.000000E + 00 0.000000E + 00

  The surface numbers 1 to 4 shown in Table 2 correspond to the numbers 1 to 4 shown in FIG. Specifically, the first surface and the second surface correspond to the surface of the first optical member 36 (the same as in the first embodiment). The third surface is the surface on the light source side of the second optical member 37, and the curve represented by the aspheric surface data shown in Table 2 and the aspheric surface formula (3) is centered on the optical axis AX of the objective optical system 31. A part of the surface rotated as an axis, and the vertex of the reference spherical surface of this aspheric surface is on the optical axis AX of the objective optical system 31. The fourth surface is the surface on the sample surface side of the second optical member 37, and the curve represented by the aspheric surface data shown in Table 2 and the aspheric surface formula (3) is taken as the optical axis AX of the objective optical system 31. The apex of the reference spherical surface of this aspheric surface, which is a part of the surface rotated as the central axis, lies on the optical axis AX of the objective optical system 31. In addition, in FIG. 5, the part which was notched among the lens surfaces of the 2nd optical member 37 which forms a 3rd surface and a 4th surface is shown with a broken line. The other descriptions are the same as in the first embodiment.

  When the dark field illumination optical system 35 according to the second embodiment and the objective lens 30 having the illumination optical system are configured as described above, the loss of light quantity of the illumination light can be minimized and efficient illumination can be performed. . Further, the number of parts is small, and cost reduction can be achieved. The first optical member 36 of the second embodiment has the same shape as the first optical member 36 of the first embodiment, and the cost can be further reduced by using the same first optical member 36 at different magnifications. It becomes.

Third Embodiment
In the first embodiment described above, a case where a part of the high-order aspheric surface having the vertex of the reference spherical surface on the optical axis AX of the objective optical system 31 as the second optical member 37 is used as a perforated mirror The reflective surface is not limited to this shape. For example, as shown in FIG. 6, it is an ellipse whose major axis is tilted with respect to the optical axis AX of the objective optical system 31, and one of the two focal points (focal point Fa) is illuminated by the first optical member 36 The ellipse having the focusing position of the light beam and disposed on the symmetry axis SAX of the first optical member 36 and the other (focus Fb) disposed at the position where the sample surface intersects the optical axis AX is rotated about the optical axis AX A part (concave surface) of the rotationally symmetric surface may be used as a reflection surface of the second optical member 37.

  In the third embodiment shown in FIG. 6, the first optical member 36 is an arc having a height h2 of 13.9 mm from the optical axis AX of its symmetry axis SAX and a radius of curvature of 17.2 mm of the surface R1. The surface R2 is a flat surface, and the distance d between the surface R1 and the surface R2 on the symmetry axis SAX is set to 3.5 mm. The medium of the first optical member 36 has a refractive index nd for the d-line of 1.5251 and an Abbe number dd of 56. The ellipse constituting the reflection surface of the second optical member 37 has a major axis radius a of 19.17831 mm, a minor axis radius b of 10.72451 mm, and an inclination angle θ of the major axis with respect to the optical axis AX of 25 It is .9204 degrees.

  Also with the dark field illumination optical system 35 according to the third embodiment and the objective lens 30 having this illumination optical system, it is possible to minimize the light amount loss of the illumination light and achieve efficient illumination. Further, the number of parts is small, and cost reduction can be achieved.

  Although the focal point Fa is disposed on the symmetry axis SAX in FIG. 6, the focal point Fa may be shifted in the direction perpendicular to the optical axis AX from the position of FIG. 6 within the range of 1 mm or less. . In the third embodiment, the illumination light has a spread angle of about 1 ° in half angle, and the focusing position in the radial direction of the first optical member 36 which is a toroidal lens has a width of about 1 mm. Specifically, assuming that the incident angle of the illumination light to the first optical member 36 is 1 °, and the focal length fr of the first optical member 36 in the radial direction is 32.375 mm, The shift amount in the direction perpendicular to the optical axis is fr × tan (1 °) = 0.565 mm, and the width is about 1 mm.

In order to solve the above-mentioned problem, the objective lens illuminates a specimen through a light path disposed so as to surround the objective optical system and light substantially parallel to the optical axis of the objective optical system. It is an objective lens having an optical system, and the dark field illumination optical system has positive refractive power in the radial direction of a circle centered at least on the optical axis of the objective optical system, and condenses light in this radial direction And a second optical member for deflecting the light diverged from the light collection point in the direction of the optical axis to irradiate the specimen with the first light member.
In such an objective lens, the first optical member refracts the light closest to the optical axis among the light in the radial direction more than the light most distant from the optical axis in any cross section including the optical axis. In addition, light on the side closest to the optical axis is refracted in the radial direction so as to be away from the optical axis.
Further, such an objective lens preferably satisfies the condition of the following equation.
1/3 ≦ fr / (fp−WD) <1
However,
fr: radial focal length of first optical member fp: same focal length of objective lens WD: working distance of objective lens Further, in such an objective lens, the second optical member has a reflecting surface with a high-order aspheric shape It is preferable that the holed mirror is a concave surface formed in and having a cylindrical opening in a portion including the optical axis.
Further, in such an objective lens, it is preferable that the second optical member is a perforated lens in which at least one lens surface is formed in an aspheric shape and an opening is provided in a portion including the optical axis.
In addition, in such an objective lens, the second optical member is a concave surface formed by rotating a part of an ellipse whose major axis is inclined with respect to the optical axis of the objective lens around the optical axis. Preferably, the mirror is a perforated mirror having a cylindrical opening in a portion including the optical axis.
A microscope according to the present invention is characterized by having any one of the above-mentioned objective lenses.

Reference Signs List 1 microscope 30 objective lens 31 objective optical system 35 illumination optical system for dark field 36 first optical member 37 second optical member

Claims (7)

An objective optical system,
A light shielding member,
An objective lens case,
Dark field optical system,
An objective lens having
The dark field optical system
A first optical member,
A second optical member,
Have
The first optical member condenses incident light at a condensing position between the first optical member and the second optical member,
The second optical member deflects light which has become diverging light from the light collecting position and irradiates the specimen with the light;
The light shielding member is
A first light shielding portion,
And a second light shielding portion provided closer to the sample than the first light shielding portion,
The surface of the second light shielding portion facing the objective lens housing is provided closer to the objective lens housing than the surface of the first light shielding portion facing the objective lens housing.
The objective lens, wherein the first optical member is disposed in a space between the first light shielding portion and the objective lens housing. The objective lens housing is
A first housing unit,
And a second casing provided closer to the sample than the first casing.
The objective lens according to claim 1, wherein a surface of the first housing unit facing the light shielding member is provided closer to the light shielding member than a surface of the second housing unit facing the light shielding member. . The distance between the surface of the second light shielding portion facing the first housing portion and the surface of the first housing portion facing the second light shielding portion is the first housing portion of the first light shielding portion. The objective lens according to claim 2, wherein a distance between a surface facing the lens unit and a surface facing the first light shielding unit of the first housing unit is smaller than a distance between the surface facing the lens unit and the surface facing the first light shielding unit. The distance between the surface of the first housing portion facing the second light shielding portion and the surface of the second light shielding portion facing the first housing portion is the second light shielding portion of the second housing portion. 4. The objective lens according to claim 2, wherein the distance between the surface facing the second light shielding portion and the surface facing the second housing portion of the second light shielding portion is smaller than the distance between the second light shielding portion and the surface facing the second housing portion. The objective lens according to any one of claims 1 to 4, wherein the second optical member is a mirror. The objective lens according to any one of claims 1 to 5, wherein the first optical member is a toroidal lens.   The microscope which has an objective lens of any one of Claims 1-6.

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