JP2016139007A - microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microscope that can easily change over angle dependency of an intensity distribution of illumination light.SOLUTION: A microscope comprises: a stop member (33) that has an aperture part (34); a first polarizer (31) that covers a part of the aperture; a second polarizer (32) that is relatively rotatable with respect to the first polarizer; and a condenser lens and objective lens that irradiate a sample with illumination light passing through the first polarizer and second polarizer. The aperture part is arranged at a position apart from an optical axis (AX) of the condenser lens in only one part of a pair of areas sandwiching a surface including the optical axis thereof, and when the shortest distance from the optical axis of the condenser lens to an edge of the aperture part is denoted as h1, the shortest distance from the optical axis thereof to an edge of the first polarizer in the aperture part is denoted as h2, the longest distance from the optical axis thereof to the edge of the aperture part is denoted as h4, a focal length of the condenser lens is denoted as f, and a numerical number of the objective lens is denoted as NA1, h1<f×NA1≤h2<h4 is satisfied.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a microscope.

  In the field of the microscope, a microscope that can switch observation methods such as phase difference observation, dark field observation, and oblique illumination observation has been proposed (for example, see Patent Document 1 below). The microscope of Patent Document 1 includes a diaphragm member in which a plurality of openings having different shapes are formed. In this microscope, the aperture arranged in the optical path can be selected by sliding the diaphragm member, and switching between phase difference observation and oblique illumination observation is possible.

U.S. Pat. No. 4,407,569

  By the way, when the diaphragm member is slid, a configuration and labor for positioning the diaphragm member may be required. An object of this invention is to provide the microscope which can switch easily the angle dependence of the intensity distribution of the illumination light irradiated to a sample.

  According to the aspect of the present invention, a diaphragm member having an opening through which illumination light can pass, a first polarizing plate covering a part of the opening, a first polarizing plate disposed in the optical path of the illumination light, A relatively rotatable second polarizing plate, a condenser lens that irradiates the sample with illumination light passing through the first polarizing plate and the second polarizing plate, an objective lens disposed on the observation side of the sample, The opening is disposed only in one of the pair of regions sandwiching the surface including the optical axis of the condenser lens at a position away from the optical axis of the condenser lens. The shortest distance to the edge is h1, the shortest distance from the optical axis to the edge of the first polarizing plate at the opening is h2, and the longest distance from the optical axis of the condenser lens to the edge of the opening is h4. Let f be the focal length of Lens of a numerical aperture when the NA1, satisfy h1 <f × NA1 ≦ h2 <h4, microscopes, wherein provided that.

  ADVANTAGE OF THE INVENTION According to this invention, the microscope which can switch easily the angle dependence of the intensity distribution of the illumination light irradiated to a sample can be provided.

It is a figure which shows the microscope which concerns on embodiment. It is a figure which shows the aperture | diaphragm | squeeze part which concerns on 1st Embodiment. It is a figure which shows the optical path of the microscope which concerns on 1st Embodiment. It is a figure which shows the aperture | diaphragm | squeeze part which concerns on a modification. It is a figure which shows the aperture_diaphragm | restriction part which concerns on 2nd Embodiment. It is a figure which shows the optical path of the microscope which concerns on 2nd Embodiment. It is a table | surface which shows evaluation of the imaging performance at the time of changing the parameter of a light reduction area | region. It is a figure for demonstrating the numerical simulation which changed the transmittance | permeability. It is a figure which shows the aperture | diaphragm | squeeze part which concerns on a modification.

[First Embodiment]
A first embodiment will be described. FIG. 1 is a diagram showing a microscope MS according to the present embodiment. The microscope MS is an upright microscope that magnifies and observes the sample S, for example. The microscope MS is, for example, a transmission type microscope that performs observation using light transmitted and scattered by the sample S, but may be a reflection type microscope that performs observation using light reflected and scattered by the sample S.

  The microscope MS includes, for example, a light source unit 10, a base 11, an upright base 12, an arm 13, an illumination lens unit 14, a sample stage 15, a stage driving unit 16, a revolver 17, a plurality of objective lenses 18, an observation lens barrel 19, and An eyepiece lens barrel 20 is provided. The optical system disposed in the optical path from the light source unit 10 to the inside of the eyepiece lens barrel 20 includes, for example, a rotationally symmetric lens member such as a spherical lens or an aspheric lens. Hereinafter, in the optical system of the microscope MS, an axis connecting the rotational symmetry axes of the lens members is referred to as an optical axis AX. The optical axis AX is determined according to the rotationally symmetric axis of the original rotationally symmetric shape even in a lens member using a part of the rotationally symmetric shape such as a cut lens.

  The base 11 can be placed on, for example, a desk or table, and its lower surface is formed flat. The upright base 12 is a member extending in the vertical direction with the base 11 as a base end, for example. The arm 13 is a member extending in the horizontal direction with the upright base 12 as a base end, for example. Hereinafter, the tip side of the arm 13 is referred to as the front side of the microscope MS, and the opposite side is referred to as the rear side.

  For example, the light source unit 10 is disposed on the rear surface side of the base 11 and connected to the rear surface of the base 11. The illumination lens unit 14 is fixed to the front side of the upright base 12. The stage driving unit 16 is disposed above the illumination lens unit 14 and is fixed to the front side of the upright base 12. The stage driving unit 16 holds the sample stage 15 on which the sample S is placed. The stage drive unit 16 moves the sample stage 15 up and down in a direction parallel to the optical axis AX, moves the sample stage 15 in a direction perpendicular to the optical axis AX, and rotates the sample stage 15 around the optical axis AX. You can do that.

  The revolver 17 is disposed above the sample stage 15 and attached to the lower end of the tip of the arm 13. The revolver 17 holds, for example, a plurality of objective lenses 18 (for example, the objective lens 18a and the objective lens 18b) having different magnifications. The microscope MS can switch the objective lens (for example, the objective lens 18 a) arranged on the optical path (around the optical axis AX) among the plurality of objective lenses 18 by the rotation of the revolver 17.

  The observation barrel 19 is arranged above the revolver 17 and is attached to the upper end of the arm 13. The observation barrel 19 extends upward with the arm 13 as a base end, and the tip end side is bent and inclined with respect to the base end side. The eyepiece lens barrel 20 is connected to the distal end side of the observation barrel 19.

  Hereinafter, each part of the optical system of the microscope MS will be described in the order from the light source unit 10 toward the eyepiece lens barrel 20. The light source unit 10 emits illumination light. The light source unit 10 includes a light source 21 accommodated in the housing. The light source 21 may be a solid light source such as an LED or a lamp light source. The microscope MS may not include at least a part of the light source unit 10. For example, the light source unit 10 may be externally attached during observation.

  The microscope MS includes a collector lens 22 and a mirror 23 accommodated in the base 11 on the light emitting side of the light source unit 10. For example, the collector lens 22 has its optical axis set coaxially with the optical axis AX, and makes the illumination light beam from the light source unit 10 parallel. For example, the reflecting surface of the mirror 23 is arranged at an angle of 45 ° with the optical axis AX. The illumination light from the collector lens 22 is reflected by the mirror 23 and travels upward.

  The illumination lens unit 14 includes a plurality of apertures 24 (eg, apertures 24a and 24b), a turret 25, and a condenser lens 26. Each of the plurality of diaphragms 24 is provided in one-to-one correspondence with any one of the plurality of objective lenses 18. For example, the diaphragm unit 24a corresponds to the objective lens 18a, and the diaphragm unit 24b corresponds to the objective lens 18b. The turret 25 holds a plurality of throttle portions 24 and can rotate around a predetermined axis 25a. For example, the predetermined axis 25a is set at a position that is parallel to the optical axis AX and shifted from the optical axis AX in a direction perpendicular to the optical axis AX. The microscope MS can switch a diaphragm unit (for example, the diaphragm unit 24 a) arranged on the optical path (around the optical axis AX) among the plurality of diaphragm units 24 by rotating the turret 25. In the following description, one diaphragm part arranged in the optical path of the illumination light L among the plurality of diaphragm parts 24 is appropriately denoted by reference numeral 24.

  The condenser lens 26 condenses the illumination light that has passed through the diaphragm 24 (for example, the diaphragm 24a) and irradiates the sample S. The optical axis of the condenser lens 26 is coaxial with the optical axis AX. Hereinafter, light emitted from the sample S by irradiation of illumination light is referred to as observation light. In the case of a transmission type microscope, the observation light includes light transmitted and scattered by the sample S, and in the case of a reflection type microscope, the observation light includes light reflected and scattered by the sample S.

  For example, the sample S is disposed on a plane that includes the rear focal point of the condenser lens 26 and is orthogonal to the optical axis AX. Each of the plurality of aperture portions 24 is disposed on a plane that includes the front focal point of the condenser lens 26 and is orthogonal to the optical axis AX, for example.

  Each of the plurality of objective lenses 18 is disposed such that its front focal plane coincides with the rear focal plane of the condenser lens 26. In the following description, one objective lens arranged in the optical path of the illumination light among the plurality of objective lenses 18 is appropriately referred to as a first objective lens 18.

  The microscope MS includes a second objective lens 27 and a prism 28 held by the observation lens barrel 19 and an eyepiece lens held by the eyepiece lens barrel 20 on the light emission side of the first objective lens (for example, the objective lens 18a). 29. The first objective lens 18 and the second objective lens 27 form an image of the sample S. The prism 28 guides the observation light from the second objective lens 27 to the eyepiece lens 29. The eyepiece lens 29 relays an image formed by the first objective lens 18 and the second objective lens 27, for example.

  Note that the number of objective lenses included in the microscope MS may be one or any number of two or more. When the number of objective lenses is one, the number of apertures 24 may be one. Further, the prism 28 may guide at least a part of the observation light to an imaging element that captures an image of the sample S. In addition, the prism 28 may branch the observation light so as to guide a part of the observation light to the imaging element and guide another part of the observation light to the eyepiece lens 29. The microscope MS may or may not include the above-described imaging element. For example, the image sensor may be externally attached to the microscope MS during observation.

  In this embodiment, the microscope MS has an oblique illumination observation mode (hereinafter referred to as an oblique mode) and a dark field observation mode (hereinafter referred to as a dark field mode), and these modes are switched. Is possible. The microscope MS can vary the intensity distribution of the illumination light that passes through the diaphragm unit 24, and can thereby change the angle distribution of the illumination light toward the sample S.

  FIG. 2A is a perspective view showing the diaphragm portion 24, and FIG. 2B is a plan view showing the diaphragm portion 24. In the following description, a direction parallel to the optical axis AX is a Z direction, one direction orthogonal to the Z direction is an X direction, and a direction orthogonal to the X direction and the Z direction is a Y direction. As shown in FIG. 2A, the diaphragm unit 24 includes a first polarizing plate 31, a second polarizing plate 32, and a diaphragm member 33.

  The diaphragm member 33 has an opening 34 through which the illumination light L can pass. The aperture member 33 has a light shielding portion that shields the illumination light L around the opening 34. The diaphragm member 33 is, for example, a disk-shaped member, and is arranged perpendicular to the optical axis AX. The opening 34 is disposed only in one region A4 (region in the + Y direction) of the pair of regions (region A4 and region A5) sandwiching the surface Pxz including the optical axis (optical axis AX) of the condenser lens 26. . The opening 34 is disposed at a position away from the optical axis (optical axis AX) of the condenser lens, and the diaphragm member 33 blocks the illumination light L on the optical axis AX. The opening 34 has, for example, a rectangular edge shape.

  The first polarizing plate 31 is disposed so as to cover a part of the opening 34 when viewed in plan from the direction of the optical axis AX. The first polarizing plate 31 is disposed so as to overlap a part of the region inside the opening 34. In the area inside the opening 34 (see FIG. 2B), the dimming area A1 through which the illumination light L that passes through the first polarizing plate 31 passes and the illumination light L that does not pass through the first polarizing plate 31 are present. And a passing area A2.

  The first polarizing plate 31 is disposed so as to cover a portion of the opening 34 that is relatively close to the optical axis AX and not cover a portion of the opening 34 that is relatively far from the optical axis AX. . That is, the light control area A1 is disposed closer to the optical axis AX than the passage area A2. The first polarizing plate 31 is, for example, a plate-like member whose shape is a rectangular shape with rounded corners, and is arranged so that one side thereof is parallel to one side of the edge of the opening 34.

  The first polarizing plate 31 is fixed to the diaphragm member 33 and is unitized with the diaphragm member 33. The first polarizing plate 31 is provided on the surface of the diaphragm member 33 on the incident side of the illumination light L. A part of the unit including the first polarizing plate 31 and the diaphragm member 33 is disposed, for example, on the front focal plane of the condenser lens 26 or in the vicinity thereof. For example, a part of the first polarizing plate 31 may be disposed on the front focal plane of the condenser lens 26, or a part of the diaphragm member 33 may be disposed.

  For example, the first polarizing plate 31 and the diaphragm member 33 are held so as not to rotate around the optical axis AX in a state where the first polarizing plate 31 and the diaphragm member 33 are disposed in the optical path of the illumination light (eg, during observation). The first polarizing plate 31 may be rotatable around the optical axis AX in a state where the first polarizing plate 31 is disposed in the optical path of the illumination light L. For example, the first polarizing plate 31 may be rotatable together with the diaphragm member 33. Although the direction of the transmission axis 31a of the first polarizing plate 31 is arbitrarily set, it is assumed here to be parallel to the Y direction. The polarizing plate is an optical member through which linearly polarized light in a predetermined direction passes. Hereinafter, an axis parallel to the predetermined direction is referred to as a transmission axis.

  The second polarizing plate 32 is disposed in the optical path of the illumination light L. For example, the second polarizing plate 32 is disposed on the incident side of the illumination light L with respect to the first polarizing plate 31. The second polarizing plate 32 is a disk-shaped member, for example, and is disposed so as to be orthogonal to the optical axis AX. The second polarizing plate 32 can be rotated relative to the first polarizing plate 31. Here, the rotational position of the first polarizing plate 31 is fixed, and the second polarizing plate 32 can rotate around the optical axis AX with respect to the first polarizing plate 31. The 1st polarizing plate 31 and the 2nd polarizing plate 32 can be arrange | positioned in the rotation position which satisfy | fills the relationship of an open Nicol mutually, and the rotation position which satisfy | fills the relationship of cross Nicol. As shown in FIG. 2A, the second polarizing plate 32 has, for example, a transmission axis 32a from the rotational position where the transmission axis 32a is parallel to the transmission axis 31a of the first polarizing plate 31. The polarizing plate 31 can be rotated to a rotational position perpendicular to the transmission axis 31a.

  The microscope MS adjusts the amount of illumination light L incident on the sample S as the first polarizing plate 31 and the second polarizing plate 32 rotate relatively. In the declination mode, the first polarizing plate 31 and the second polarizing plate 32 are disposed at a rotational position where the transmission axis 31a and the transmission axis 32a are non-perpendicular (eg, parallel). For example, in the declination mode, the angle between the transmission axis 31a and the transmission axis 32a is set to 0 ° or more and less than 90 °. Further, in the dark field mode, the first polarizing plate 31 and the second polarizing plate 32 are in a rotational position where the angle between the transmission axis 31a and the transmission axis 32a is close to 90 ° compared to the declination mode, or the transmission. The shaft 31a and the transmission shaft 32a are arranged at a rotational position where the angle is 90 °. Therefore, in the dark field mode, the amount of the illumination light L passing through the first polarizing plate 31 is smaller than that in the oblique mode, and the incident angle with respect to the sample S of the illumination light L passing through the diaphragm 24 is relatively small. The light intensity of the component is reduced.

  Further, the first polarizing plate 31 may be attached to a member different from the diaphragm member 33 and supported by this member. In this case, the first polarizing plate 31 may be rotatable around the optical axis AX, or may be fixed so as not to rotate around the optical axis AX. Further, when the first polarizing plate 31 is rotatable, the second polarizing plate 32 may be rotatable so that the relationship of the rotational position with the first polarizing plate 31 changes, It may be fixed so as not to rotate.

Here, in the radial direction with respect to the optical axis AX (the radial direction of the circle centering on the optical axis AX on the diaphragm member 33), the side approaching the optical axis AX is referred to as the inner side, and the side away from the optical axis AX is referred to as the outer side. . As shown in FIG. 2B, the shortest distance from the optical axis AX to the inner edge of the opening 34 is h1, and the shortest distance from the optical axis AX to the outer edge of the first polarizing plate 31 in the opening 34. The distance is h2, and the longest distance from the optical axis AX to the outer edge of the opening 34 is h4. The shortest distance h1 and the shortest distance h2 satisfy the following formula (1) when the focal length of the condenser lens 26 is f and the numerical aperture of one objective lens selected from the plurality of objective lenses 18 is NA1. Is set as follows.
h1 <f × NA1 ≦ h2 <h4 (1)

  In FIG. 2B, the shape of the opening 34 is rectangular, and the shortest distance h1 is a distance from the side closest to the optical axis AX to the optical axis AX among the four sides of the opening 34. The longest distance h4 is the distance from the vertex farthest from the optical axis AX to the optical axis AX among the four vertices of the opening 34. In FIG. 2B, symbol h5 is a distance from the opposite side of the side corresponding to the shortest distance h1 to the optical axis AX, and the distance h5 satisfies a relationship of h2 <h5 <h4.

  As shown in FIG. 1, when a plurality of pairs of aperture units and objective lenses are provided, the aperture unit satisfies the above formula (1) between the pair of objective lenses. For example, h1, h2, and h4 in the aperture section 24a are set so as to satisfy the above formula (1) with respect to the numerical aperture of the objective lens 18a. Further, h1, h2, and h4 of the diaphragm portion 24b are set so as to satisfy the above formula (1) with respect to the numerical aperture of the objective lens 18b.

  FIG. 3A is a diagram illustrating an optical path in the declination mode, and FIG. 3B is a diagram illustrating an optical path in the dark field mode. 3A and 3B, the optical system closer to the light source unit 10 than the diaphragm 24 and the optical system closer to the image plane Vp than the objective lens 18 are not shown.

The oblique mode refers to a case where the transmission axis of the first polarizing plate 31 and the transmission axis of the second polarizing plate 32 are not perpendicular to each other. The dark field mode refers to the first polarizing plate 31. This refers to the case where the transmission axis and the transmission axis of the second polarizing plate 32 are perpendicular or nearly perpendicular to each other. As shown in FIG. 3A, a part of the illumination light L incident on the diaphragm portion 24 in the oblique mode passes through the passage area A2 in the opening 34 of the diaphragm member 33, and the other part is adjusted. It passes through the light region A1. In FIG. 3A, a case where f × NA1 = h2 is shown as an example.
Here, of the illumination light L, light whose direct light is incident on the objective lens 18 is referred to as a low NA component L1, and light of the illumination light L whose direct light is not incident on the objective lens 18 is referred to as a high NA component L2. In the example shown in FIGS. 3A and 3B, the case of f × NA1 = h2 is shown. Therefore, the light passing through the dimming region A1 in the illumination light L becomes the low NA component L1, and the illumination light L The light passing through the passage area A2 becomes a high NA component L2. The sample NA is irradiated with the low NA component L1 and the high NA component L2 through the condenser lens 26, respectively.

  In the declination mode, as described above, the transmission axis of the first polarizing plate 31 and the transmission axis of the second polarizing plate 32 are in a rotational position that is not perpendicular to each other, and as shown in FIG. The low NA component L1 and the high NA component are incident on the sample S. In the dark field mode, as described above, the transmission axis of the first polarizing plate 31 and the transmission axis of the second polarizing plate 32 are in a vertical position or a rotation position close to perpendicular to each other. As described above, the low NA component L1 is configured not to enter the sample. The user rotates the first polarizing plate 31 or the second polarizing plate 32 to adjust the relative positional relationship between the transmission axis of the first polarizing plate 31 and the transmission axis of the second polarizing plate 32. It is possible to adjust the light amount of the low NA component L1. That is, the user can switch between the declination mode and the dark field mode, and can also adjust the light amount of the low NA component L1 in the declination mode. Therefore, the user can observe the sample S while finely adjusting the light amount of the low NA component L1.

  Since the microscope MS according to the present embodiment as described above changes the relative rotational positions of the first polarizing plate 31 and the second polarizing plate 32 in the diaphragm unit 24 that satisfies the condition of the expression (1), The angle dependency of the intensity distribution of the illumination light L irradiated to the sample S can be easily changed. When the first polarizing plate 31 and the second polarizing plate 32 are relatively rotated, for example, the light amount of the low NA component L1 can be adjusted without sliding the diaphragm member 33 in the direction intersecting the optical axis AX. it can. Therefore, for example, the positioning of the opening 34 when the diaphragm member 33 is slid can be omitted, and the amount of light of the low NA component L1 can be easily adjusted.

  When the second polarizing plate 32 is disposed on the incident side of the illumination light L with respect to the first polarizing plate 31, the light amount of the low NA component L 1 can be adjusted by the first polarizing plate 31. Here, when the first polarizing plate 31 is disposed in the vicinity of the opening 34 of the diaphragm member 33, the angle dependency of the intensity distribution of the illumination light L when entering the sample S can be adjusted with high accuracy. it can.

  Next, a modification of the diaphragm unit 24 will be described. FIGS. 4A to 4D are diagrams each showing a diaphragm unit 24 according to a modification.

  As for the aperture | diaphragm | squeeze part 24 of the 1st modification shown to FIG. 4 (A), the planar shape of the opening part 34 of the aperture_diaphragm | restriction member 33 is fan shape (a part of ring zone). The edges of the opening 34 are, for example, a part of two circles (arc 35a and arc 35b) having different diameters centered on the optical axis AX and a radial direction (radial direction) with respect to the optical axis AX to extend the arc 35a and arc. And a straight line 36 connecting 35b. In the first modification, the planar shape of the portion of the first polarizing plate 31 covering the opening 34 is a fan shape. The first polarizing plate 31 has, for example, a disk shape centered on the optical axis AX, but the shape of the portion disposed outside the opening 34 in a state viewed from the direction of the optical axis AX is arbitrarily changed. May be.

  In the diaphragm 24, the planar shape of the opening 34 may be a fan shape, and the planar shape of the portion of the first polarizing plate 31 that covers the opening 34 may be a rectangle or other shapes. Further, in the diaphragm 24, the planar shape of the opening 34 is rectangular (slit), and the planar shape of the portion of the first polarizing plate 31 covering the opening 34 is fan-shaped or other shapes. Also good.

  In the diaphragm unit 24 of the second modified example shown in FIG. 4B, the first polarizing plate 31 is arranged inside the opening 34 of the diaphragm member 33. Note that the thickness of the first polarizing plate 31 may be the same as the thickness of the diaphragm member 33, may be less than the thickness of the diaphragm member 33, or may exceed the thickness of the diaphragm member 33. The entire first diaphragm member 33 may be disposed inside the opening 34, or a part thereof may be disposed outside the opening 34.

  In the diaphragm unit 24 of the third modified example shown in FIG. 4C, the first polarizing plate 31 is disposed on the opposite side of the second polarizing plate 32 with respect to the diaphragm member 33. 4D, the second polarizing plate 32 is disposed on the exit side of the illumination light L with respect to the diaphragm member 33. In the fourth modification shown in FIG. In this case, the low NA component L1 is blocked by the second polarizing plate 32.

[Second Embodiment]
A second embodiment will be described. In the present embodiment, the same components as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. FIG. 5A is a perspective view showing the diaphragm unit 24 according to the second embodiment, and FIG. 5B is a plan view showing the diaphragm unit 24.

  The diaphragm unit 24 includes a neutral density filter (ND filter 41) that covers a part of the opening 34. The ND filter 41 is attached to the upper surface of the first polarizing plate 31 and is unitized with the diaphragm member 33 via the first polarizing plate 31. The ND filter 41 is, for example, a plate-shaped member having a rectangular planar shape, and is arranged so that one side thereof is parallel to one side of the edge of the opening 34.

  As shown in FIG. 5B, when viewed from the direction of the optical axis AX, for example, the ND filter 41 covers at least a part of the light control area A1 and does not cover the passage area A2. The For example, when the shortest distance between the outer edge of the opening 34 in the ND filter 41 and the optical axis AX is h6, the shortest distance h6 is set to satisfy h1 <h6 ≦ h2. When the planar shape of the ND filter 41 is rectangular as shown in FIG. 5B, the longest distance h3 from the optical axis AX to the ND filter 41 is the farthest from the optical axis AX among the four vertices of the ND filter 41. This is the distance from the apex to the optical axis AX. The shortest distance h6 is the distance from the opposite side of the side corresponding to the longest distance h3 to the optical axis AX, and the shortest distance h6 satisfies the relationship of h6 <h3. Hereinafter, a region that overlaps the ND filter 41 in the dimming region A1 is referred to as a dimming region A3. The dimming area A3 is set at a position relatively close to the optical axis AX in the dimming area A1.

  FIG. 6 is a diagram illustrating an optical path in the declination mode. In FIG. 6, the optical system closer to the light source 10 than the diaphragm 24 and the optical system closer to the image plane Vp than the objective lens 18 are not shown. The dark field mode is the same as the dark field mode shown in FIG. 3B because the illumination light L that has passed through the ND filter 41 is shielded by the first polarizing plate 31.

  In the declination mode, the low NA component L1 and the high NA component L2 of the illumination light L incident on the diaphragm unit 24 are irradiated to the sample S through the condenser lens 26, respectively. Here, since the amount of light is reduced when the low NA component L1 passes through the dimming region A3, it is possible to suppress an increase in the brightness of the background of the structure in the sample S.

  By the way, if the illumination light L incident on the sample S is biased toward the high NA side, unevenness may easily occur due to the structure of the sample S, for example. In order to reduce such unevenness, for example, a component on the low NA side in the illumination light L emitted from the aperture section 24 may be increased. In order to increase the component on the low NA side, for example, the shortest distance h1 from the optical axis AX to the edge of the opening 34 may be decreased. On the other hand, when the component on the low NA side increases, the background of the structure in the sample S becomes bright, and the contrast of the image of the structure may decrease.

  Therefore, in the present embodiment, a part of the low NA side component of the illumination light L passing through the diaphragm unit 24 is removed by the ND filter 41. For example, the shortest distance h1 is reduced as compared with the case where the ND filter 41 is not used, and the light amount of the component on the low NA side is reduced by the ND filter 41, whereby the illumination light L when entering the sample S is reduced to the low NA side. The increase in the amount of light of the low NA component L1 can be suppressed. Thereby, the unevenness of the image can be reduced while ensuring the contrast of the image of the structure in the sample S.

  As a result of research and development, the inventors of the present application have found that the imaging performance changes according to the setting of the dimming area A3. When the parameter α is defined by α = (h6−h1) / (h2−h1), the inventor of the present application tends to increase the shading effect as α decreases, and the edge of the sample S is emphasized as α increases. It was found that there was a tendency to obtain an image. The inventor of this application evaluated the imaging performance while changing h1 and h6. The shading referred to here is a phenomenon in which the brightness of illumination in the field of view becomes non-uniform. In particular, in the present embodiment, it is a phenomenon that changes one-dimensionally.

  FIG. 7 is a table showing α values and imaging performance evaluation results when h1 and h6 are changed. In this evaluation, h2 was a fixed value of 0.65 × f [mm], and h1 and h6 were changed in steps of 0.05 × f [mm]. In FIG. 7, the unit of h1 and h6 is mm. In each cell, the upper row shows the value of α, and the lower row shows the evaluation result of the imaging performance by ◯ or x. As shown in FIG. 7, when α is 0.22 or more, the influence of shading is suppressed to a predetermined level or less, and the imaging result is good (◯). Further, when α is 0.75 or less, the edge enhancement of the sample S is suppressed from being excessive, and the imaging result is good (◯). From such a viewpoint, h1 and h6 may be set so as to satisfy 0.22 ≦ (h6−h1) / (h2−h1) ≦ 0.75.

  The inventors of the present application have also found that the imaging performance changes according to the transmittance T [%] of the ND filter 41. The inventor of this application performed numerical simulation by changing the transmittance T, and evaluated the imaging performance.

  8A to 8C are explanatory diagrams showing calculation conditions. As shown in FIG. 8A, the shape of the opening 34 is a fan shape, the shape of the first polarizing plate 31 in the opening 34 and the shape of the ND filter 41 in the opening 34 are centered on the optical axis AX. It is a part of a concentric circle (fan shape). The radius of the arc on the side close to the optical axis AX in the opening 34 is h1, the radius of the arc on the side farther from the optical axis AX in the first polarizing plate 31 is h2, and the optical axis AX in the ND filter 41 is from the optical axis AX. The radius of the far arc is h6. H1, h2, and h6 shown in FIG. 8A correspond to h1, h2, and h6 described in FIGS. The fan-shaped opening angle θ was 60 °.

As shown in FIG. 8B, the sample Sx for numerical simulation was a one-dimensional periodic pattern. In the sample Sx, unit structures are periodically arranged in the direction Ds, and the interval between the edges of the sample Sx in the direction Ds is represented by p. p is an amplitude object of about 2 μm, and the wavelength of the illumination light is 550 nm. The transmission of the sample S, as shown in FIG. 8 (C), located in the direction Ds is 0 100% In (represented by symbol _{S 0).} The position S ₀ is the center position between the edges in the sample Sx shown in FIG. In FIG. 8 (C), the position of the end of the range the transmittance is 100% expressed by symbol _{S 2,} showing the intermediate position between the position _{S 0} and the position _{S 2} by reference numeral _{S 1.}

FIG. 8D is a diagram showing an image intensity distribution when the transmittance T is reduced, and FIG. 8E is a diagram showing an image intensity distribution when the transmittance T is increased. 8D and 8E, symbols I ₀ , I ₁ , and I ₂ denote light intensities (arbitrary units, respectively) corresponding to the positions S ₀ , S ₁ , and S ₂ shown in FIG. 8C, respectively. a.u.).

As shown in FIG. 8D, the light intensity I ₀ decreases as T decreases, and it appears that there are two peaks. As shown in FIG. 8E, the light intensity I ₀ increases as T increases, and three peaks are visible. The inventor of the present application newly found the above phenomenon and found an appropriate range of T. That is, the transmittance T [%] may be set in a range of 30% ≦ T ≦ 70%.

  Next, a modified example will be described. FIGS. 9A to 9D are diagrams showing a diaphragm unit 24 according to a modification.

  In the diaphragm unit 24 of the fifth modified example shown in FIG. 9A, the ND filter 41 has a fan-like planar shape at the portion covering the opening 34. For example, the ND filter 41 has a disk shape centered on the optical axis AX, but the shape of the portion arranged outside the opening 34 in the state viewed from the direction of the optical axis AX may be arbitrarily changed. Good.

  In the diaphragm 24, the planar shape of the opening 34 may be a fan shape, and the planar shape of the portion of the ND filter 41 that covers the opening 34 may be a rectangle or other shapes. Further, in the diaphragm 24, the planar shape of the opening 34 may be rectangular (slit), and the planar shape of the portion of the ND filter 41 covering the opening 34 may be a fan shape or other shapes.

  In the diaphragm unit 24 of the sixth modified example shown in FIG. 9B, the first polarizing plate 31 is disposed inside the opening 34 of the diaphragm member 33, and the ND filter 41 is the first polarizing plate. 31 is provided on the incident side of the illumination light L with respect to the diaphragm member 33 over the diaphragm member 33 and the diaphragm member 33.

  Note that the thickness of the ND filter 41 may be the same as the thickness of the diaphragm member 33, may be less than the thickness of the diaphragm member 33, or may exceed the thickness of the diaphragm member 33. The ND filter 41 may be in contact with the first polarizing plate 31 or may not be in contact with the first polarizing plate 31. The entire ND filter 41 may be disposed inside the opening 34, or a part thereof may be disposed outside the opening 34.

  In the diaphragm portion 24 of the seventh modification shown in FIG. 9C, the ND filter 41 is disposed inside the opening 34 of the diaphragm member 33, and the first polarizing plate 31 is disposed on the ND filter 41. It is provided over the diaphragm member 33. The first polarizing plate 31 is provided on the incident side of the illumination light L with respect to the ND filter 41.

  In the diaphragm section 24 of the eighth modification shown in FIG. 9D, the first polarizing plate 31 is disposed on the surface on the incident side of the illumination light L in the diaphragm member 33, and the ND filter 41 is composed of the diaphragm member. It is arranged on the surface on the exit side of the illumination light L in 33.

  In the diaphragm section 24 of the ninth modification shown in FIG. 9E, the ND filter 41 is disposed on the surface of the diaphragm member 33 on the incident side of the illumination light L, and the first polarizing plate 31 is composed of the diaphragm member. It is arranged on the surface on the exit side of the illumination light L in 33.

  As in the above-described modification, the ND filter 41 may be disposed on the incident side of the illumination light L with respect to the first polarizing plate 31, or on the emission side of the illumination light L from the first polarizing plate 31. It may be arranged. Further, the ND filter 41 may not be unitized with the diaphragm member 33, and may be supported by a member different from the diaphragm member 33 and the first polarizing plate 31. Further, when the diaphragm unit 24 includes the ND filter 41, for example, as illustrated in FIG. 3D, the second polarizing plate 32 is disposed on the emission side of the illumination light L from the first polarizing plate 31. May be.

  The technical scope of the present invention is not limited to the aspects described in the above-described embodiments. One or more of the requirements described in the above embodiments and the like may be omitted. In addition, the requirements described in the above-described embodiments and the like can be combined as appropriate. In addition, as long as it is permitted by law, the disclosure of all documents cited in the above-described embodiments and the like is incorporated as a part of the description of the text.

18 ... objective lens, 24 ... aperture stop, 26 ... condenser lens,
31 ... 1st polarizing plate, 31a ... absorption axis, 32 ... 2nd polarizing plate,
32a ... absorption axis, 33 ... diaphragm member, 34 ... opening, AX ... optical axis,
h1 ... shortest distance, h2 ... shortest distance, h6 ... shortest distance, L ... illumination light,
MS ... Microscope, S ... Sample

Claims (10)

A diaphragm member having an opening through which illumination light can pass;
A first polarizing plate covering a part of the opening;
A second polarizing plate disposed in the optical path of the illumination light and rotatable relative to the first polarizing plate;
A condenser lens that irradiates a sample with the illumination light that has passed through the first polarizing plate and the second polarizing plate;
An objective lens disposed on the observation side of the sample,
The opening is disposed at a position away from the optical axis of the condenser lens only in one of the pair of regions sandwiching the surface including the optical axis of the condenser lens,
The shortest distance from the optical axis of the condenser lens to the edge of the opening is h1, and the shortest distance from the optical axis to the edge of the first polarizing plate in the opening is h2, and the optical axis of the condenser lens When the maximum distance from the edge of the aperture to the edge of the aperture is h4, the focal length of the condenser lens is f, and the numerical aperture of the objective lens is NA1,
A microscope satisfying h1 <f × NA1 ≦ h2 <h4.   The amount of light incident on the sample is adjusted at an angle equal to or smaller than the opening angle of the objective lens by relatively rotating the first polarizing plate and the second polarizing plate. The microscope according to claim 1.   The first polarizing plate and the second polarizing plate are relatively rotatable from a rotational position where the respective transmission axes are parallel to each other to a rotational position where the respective transmission axes are perpendicular to each other. The microscope according to claim 1 or 2, wherein   The microscope according to claim 1, wherein the second polarizing plate is disposed on the incident side of the illumination light with respect to the first polarizing plate.   The microscope according to claim 4, wherein the first polarizing plate is unitized with the diaphragm member.   The microscope according to claim 5, wherein a part of the first polarizing plate and the diaphragm member are disposed on a front focal plane of the condenser lens.   The rotation position of the first polarizing plate is fixed, and the second polarizing plate is rotatable with respect to the first polarizing plate. microscope.   The microscope according to claim 1, further comprising an ND filter that covers a part of the opening.   The microscope according to claim 8, wherein h1 <h6 ≦ h2 is satisfied, where h6 is a shortest distance from the optical axis to the edge of the ND filter in the opening.   When the transmittance of the illumination light with respect to the ND filter is T, 0.22 ≦ (h6-h1) / (h2-h1) ≦ 0.75 and 30% ≦ T ≦ 70% are satisfied. The microscope according to claim 9, wherein the microscope is characterized.

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