JP2012208486A - Optical element, microscope equipped with optical element and method for assembly of optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element capable of aligning an optical axis of a liquid crystal optical element with an optical axis of an objective lens.SOLUTION: An optical element (103 or 10) comprises a liquid crystal optical element (3, 12 or 13) and an optical axis adjusting mechanism (4 or 14). The liquid crystal optical element (3, 12 or 13) comprises: a liquid crystal layer that is arranged toward a light source (101) from an objective lens (104) and includes liquid crystal molecules; and two first transparent electrodes that are arranged in a manner facing each other across the liquid crystal layer, and the liquid crystal optical element controls a phase or polarization plane of linearly-polarized light with a predetermined wavelength, which passes through the liquid crystal layer after being emitted from the light source, by applying voltage between the first transparent electrodes according to the predetermined wavelength. The optical axis adjusting mechanism (4 or 14) can move the liquid crystal optical element (3, 12 or 13) relatively to the objective lens (104) so as to be capable of aligning an optical axis of the liquid crystal optical element (3, 12 or 13) with an optical axis of the objective lens (104).

Description

  The present invention relates to an optical element capable of aligning the optical axis of a liquid crystal optical element that controls the phase or polarization plane of linearly polarized light and the optical axis of an objective lens, a microscope apparatus including such an optical element, and such an optical device. The present invention relates to an element assembly method.

  Conventionally, devices such as laser microscopes, optical pickup devices, laser processing machines, etc. that detect information such as the shape of an object by irradiating the object with light or cause some change in the object are used. Has been. In such an apparatus, an optical element that adjusts the wavefront and the polarization direction of light incident on the objective lens may be used together with the objective lens in order to increase the resolution.

  For example, in order to obtain a super-resolution effect by condensing light to a spot diameter smaller than the beam spot diameter due to the diffraction limit of X or Y polarization, an optical element that changes the light beam incident on the objective lens to radial polarization is used. It has been proposed to be used with an objective lens. It has also been proposed to configure such an optical element using liquid crystal (see, for example, Patent Documents 1 and 2).

JP 2010-19630 A JP 2010-15877 A

  As described above, in order to obtain the effect of reducing the diameter of the focused spot, it is required that the optical axis of the optical element using liquid crystal and the optical axis of the objective lens are exactly matched. Further, there are individual differences between the objective lens and its optical element, and generally, the optical axis of the objective lens does not coincide with the center of the outer shape of the objective lens. Therefore, it is necessary to align the optical axis of the objective lens and the optical axis of the optical element for each optical system. In particular, in an apparatus in which the objective lens can be exchanged, each time the objective lens is exchanged, the user must perform an operation of aligning the optical axis of the objective lens with the optical axis of the optical element.

  However, in the optical system disclosed in Patent Document 1 or 2, another optical element is disposed between the objective lens and the optical element. Therefore, it is not possible to directly align the optical axis of the objective lens and the optical axis of the optical element, and it is necessary to adjust the position of the optical axis of each element as the entire optical system. Was cumbersome.

  Therefore, an object of the present invention is to provide an optical element that can align the optical axis of a liquid crystal optical element with the optical axis of an objective lens.

  According to one aspect of the present invention, an optical element is provided. The optical element is disposed on the light source side with respect to the objective lens, and includes a liquid crystal layer including liquid crystal molecules and two first transparent electrodes disposed so as to face each other with the liquid crystal layer interposed therebetween. A phase or polarization plane of linearly polarized light having a predetermined wavelength emitted from a light source that transmits through the liquid crystal layer is controlled by applying a voltage corresponding to the predetermined wavelength between the two first transparent electrodes. The first liquid crystal optical element and the first liquid crystal optical element can be moved relative to the objective lens so that the optical axis of the first liquid crystal optical element can be aligned with the optical axis of the objective lens. Mechanism.

  Here, the optical axis adjustment mechanism is parallel to a plane orthogonal to the optical axis of the objective lens and is capable of moving the first liquid crystal optical element in the first direction and the second direction orthogonal to each other. It is preferable to have an adjustment mechanism.

  The optical axis adjustment mechanism preferably has a tilt adjustment mechanism capable of adjusting the inclination of the optical axis of the first liquid crystal optical element with respect to the optical axis of the objective lens.

  The optical element preferably further includes a housing that integrally holds the objective lens and the first liquid crystal optical element.

  In this case, it is preferable that the housing further includes a mounting portion for attaching the housing to the microscope apparatus having the light source so that the first liquid crystal optical element is disposed closer to the light source than the objective lens.

  Further, the optical element can align the optical axis of the second liquid crystal optical element disposed on the light source side with respect to the first liquid crystal optical element and the optical axis of the objective lens. It is preferable to further include a second optical axis adjustment mechanism that can move the second liquid crystal optical element independently of the first liquid crystal optical element.

  Here, the second liquid crystal optical element transmits the phase of the incident light transmitted through a part of the plurality of concentric annular zones around the optical axis of the second liquid crystal optical element to the other ring. More preferably, it is inverted with respect to the phase of the incident light transmitted through the band.

  Furthermore, the liquid crystal layer of the first liquid crystal optical element has a plurality of regions arranged along a circumferential direction centering on the optical axis of the first liquid crystal optical element, and is included in each of the plurality of regions. The alignment directions of the liquid crystal molecules are different from each other, and each of the plurality of regions of the liquid crystal layer is a component that transmits the region of linearly polarized light by applying a voltage according to a predetermined wavelength between the two transparent electrodes. Is preferably rotated so as to be parallel to the radiation direction centered on the optical axis of the first liquid crystal optical element in accordance with the alignment direction of the liquid crystal molecules contained in the region.

  Alternatively, one of the two first transparent electrodes of the first liquid crystal optical element is arranged corresponding to each of a plurality of concentric annular zones centering on the optical axis of the first liquid crystal optical element. In the first liquid crystal optical element, a different voltage is applied to each of the plurality of annular electrodes between the annular electrode and the other of the two first transparent electrodes. Thus, it is preferable to control the amount of phase modulation of linearly polarized light that passes through each annular zone.

  In this case, the optical element is arranged in an optical system having a light source and an objective lens, and phase modulation of linearly polarized light that passes through each of the plurality of annular zones so as to cancel the phase distribution of wavefront aberration generated in the optical system. Preferably, each of the plurality of annular electrodes further includes a driving device that adjusts a voltage applied between the annular electrode and the other of the two first transparent electrodes so as to generate a quantity. . The driving device is preferably configured to be able to apply a voltage between the two first transparent electrodes even during operation of the optical axis adjusting mechanism.

  According to another aspect of the invention, a method for assembling an optical element is provided. This assembling method has a plurality of regions arranged along a circumferential direction centering on the optical axis, and a polarization plane of linearly polarized light emitted from a light source having a predetermined wavelength is divided into each of the plurality of regions. A liquid crystal optical element that is transmitted and rotated so as to be parallel to the radiation direction centered on the optical axis is disposed on the light source side of the objective lens, and images of a plurality of regions of the liquid crystal optical element are formed by a predetermined optical system. The liquid crystal optical element is moved relative to the objective lens so that it is formed on the image plane of the optical system and the center of the image of the plurality of areas coincides with the position on the image plane corresponding to the optical axis of the objective lens. To align the optical axis of the liquid crystal optical element with the optical axis of the objective lens.

  According to still another aspect of the present invention, a method for assembling an optical element is provided. The assembling method includes a first transparent electrode, a second transparent electrode that is disposed so as to face the first transparent electrode, and has a pattern in a predetermined positional relationship with respect to the first optical axis; A liquid crystal layer including liquid crystal molecules sandwiched between the first transparent electrode and the second transparent electrode, and having a phase of linearly polarized light emitted from a light source that transmits the liquid crystal layer and having a predetermined wavelength; A liquid crystal optical element that is controlled by applying a voltage corresponding to the predetermined wavelength between the first transparent electrode and the second transparent electrode, closer to the light source than the objective lens; A voltage is applied between the second transparent electrode and an image of the pattern of the first transparent electrode is formed on the image plane of the predetermined optical system by a predetermined optical system. The point in the positional relationship coincides with the position on the image plane corresponding to the second optical axis of the objective lens So that the, the liquid crystal optical element by relatively moving the objective lens, includes aligning the first optical axis of the liquid crystal optical element and a second optical axis of the objective lens.

  According to yet another embodiment of the present invention, a microscope apparatus is provided. This microscope apparatus includes a light source that outputs linearly polarized light having a predetermined wavelength, an optical element that controls the phase or plane of polarization of the linearly polarized light, and an objective lens that condenses the light beam that has passed through the optical element at a predetermined spot on the sample. And a light receiving element for receiving light from a predetermined spot. Here, the optical element has a liquid crystal layer containing liquid crystal molecules and two first transparent electrodes arranged so as to face each other with the liquid crystal layer interposed therebetween, and is emitted from a light source that transmits the liquid crystal layer. A liquid crystal optical element that controls the phase or plane of polarization of linearly polarized light having a predetermined wavelength by applying a voltage corresponding to the predetermined wavelength between the two first transparent electrodes, and the optical axis of the liquid crystal optical element An optical axis adjustment mechanism capable of moving the liquid crystal optical element relative to the objective lens so that the optical axis of the objective lens can be aligned with the optical axis of the objective lens, and a housing that integrally holds the objective lens and the liquid crystal optical element .

  The optical element according to the present invention has an effect that the optical axis of the liquid crystal optical element can be aligned with the optical axis of the objective lens.

It is a schematic block diagram of the laser microscope provided with the optical element which concerns on embodiment of this invention. (A) is the schematic front view which looked at the optical element which concerns on the 1st Embodiment of this invention from the objective-lens side, (b) is a schematic side view of an optical element, (c) is ( It is a schematic side sectional view of the optical element viewed from the direction of the arrow AA ′ along the dotted line in a). It is a schematic front view of a liquid crystal optical element. (A) is a schematic side cross-sectional view of the liquid crystal optical element when no voltage is applied, in the dotted line seen from the direction of the arrow XX ′ in FIG. 3, and (b) is a cross-sectional view of XX ′ in FIG. It is a schematic sectional side view of a liquid crystal optical element when a voltage is applied, in the dotted line seen from the direction of the arrow. It is a schematic front view of the liquid-crystal layer which shows the orientation direction of the liquid crystal in each sector area of the liquid-crystal layer of a liquid-crystal optical element, and the polarization direction of the linearly polarized light which permeate | transmitted each sector area. It is a figure which shows the orientation direction of the liquid crystal in each area | region of the liquid crystal layer of a liquid crystal optical element by a modification, and the polarization direction of the linearly polarized light component which permeate | transmitted each area | region. It is a figure which shows an example of the optical path length difference of the voltage applied to the liquid crystal layer between the transparent electrodes which a liquid crystal optical element has, and the normal ray and extraordinary ray which arise with the liquid crystal layer. It is a figure which shows the assembly procedure of the optical element by 1st Embodiment. (A) is a schematic side view of the optical element which concerns on the 2nd Embodiment of this invention, (b) is the optical element along the dotted line of the perpendicular direction seen from the direction of arrow BB 'of (a). (C) is a schematic sectional drawing of the optical element along the horizontal dotted line seen from the direction of arrow CC 'of (a). (A) is a schematic front view of an example of a phase inversion element, (b) is a schematic front view of another example of a phase inversion element. (A) is a schematic side cross-sectional view of a phase inversion element showing a state of liquid crystal molecules included in the phase inversion element when no voltage is applied to the phase inversion element, and (b) is a voltage across the phase inversion element. It is a schematic side sectional view of a phase inversion element showing a state of liquid crystal molecules contained in the phase inversion element when is applied. It is a schematic front view of the phase modulation element which shows an example of one structure of the two transparent electrodes which the phase modulation element of the optical element by 3rd Embodiment has. (A) And (b) is a figure which shows an example of the electrode to which a voltage is applied, respectively in the phase modulation element which has n circular electrodes and ring-shaped electrodes. (A) is a figure which shows an example of the distribution of the voltage applied between each annular electrode of a phase modulation element, and the transparent electrode which opposes, in order to correct | amend the wave aberration produced by the optical system containing an objective lens. FIG. 6B is a diagram illustrating an example of a distribution of phase modulation amounts generated by the phase modulation element in accordance with the voltage distribution shown in FIG. It is a schematic front view which shows another example of the structure of one of the two transparent electrodes which the phase modulation element of the optical element by a modification has.

  Hereinafter, optical elements having liquid crystal optical elements according to various embodiments will be described with reference to the drawings. This optical element is designed so that the optical axis of the liquid crystal optical element that controls the phase or plane of polarization of incident linearly polarized light coincides with the optical axis of the objective lens that collects the light beam that has passed through the liquid crystal optical element. An optical axis adjustment mechanism capable of adjusting the position of the liquid crystal optical element with respect to the optical axis is provided.

  FIG. 1 is a schematic configuration diagram of a laser microscope including an optical element according to an embodiment of the present invention. In the laser microscope 100, a light beam emitted from a laser light source 101, which is a coherent light source that outputs linearly polarized light, is converted into parallel light by a collimating optical system 102 and is transmitted through a beam splitter 106. The parallel light passes through the liquid crystal optical element of the optical element 103 and is condensed on the sample 105 by the objective lens 104. The optical element 103 and the objective lens 104 are integrated, and the liquid crystal optical element and the objective lens 104 are aligned so that the optical axis of the liquid crystal optical element included in the optical element 103 and the optical axis of the objective lens 104 coincide with each other. Adjustments have been made. A light beam including information on the sample 105 such as a light beam reflected or scattered by the sample 105 or a fluorescence generated from the sample follows the optical path in the reverse direction, is reflected by the beam splitter 106, and is a second optical system, ie, confocal optics. The light is condensed again on the confocal pinhole 108 by the system 107. Then, the light beam from other than the focal position of the sample contained in the light beam is cut, and only the light beam from the focal position is detected by the detector 109 having a photodiode or a photomultiplier tube. The detector 109 outputs an electrical signal corresponding to the detected light amount to the controller 110.

  The controller 110 includes, for example, a processor, a memory, and an interface circuit for connecting the controller 110 to each part of the laser microscope 100. The controller 110 controls the laser light source 101 and the light modulation element 103. Then, the controller 110 supplies predetermined power to the laser light source 101 to cause the laser light source 101 to output illumination light. In addition, when the laser light source 101 includes a plurality of light emitting elements, the controller 110 outputs illumination light to any one of the plurality of light emitting elements according to a user operation via a user interface (not shown), for example. A control signal is transmitted to the laser light source 101.

  Further, the controller 110 has a drive circuit 111 and controls the light modulation element 103 via the drive circuit 111. That is, the controller 110 controls the drive circuit 111 so that an applied voltage corresponding to the wavelength of light output from the laser light source 101 is applied to each liquid crystal layer included in the liquid crystal optical element of the optical element 103. Thereby, the optical element 103 can control the phase and polarization plane of linearly polarized light having a predetermined wavelength. Note that the drive circuit 111 may be provided independently of the controller 110. In this case, the controller 110 and the drive circuit 11 are connected by a signal line.

In particular, when the laser light source 101 includes a plurality of light emitting elements that output light having different wavelengths, the controller 110 applies the liquid crystal layer included in the liquid crystal optical element of the optical element 103 according to the light emitting elements that emit light. Adjust the applied voltage.
The drive voltage applied from the drive circuit 111 to the liquid crystal layer of the liquid crystal optical element of the optical element 103 is, for example, an AC voltage that has been pulse height modulated (PHM) or pulse width modulated (PWM). Also good. In addition, as described later, the drive circuit 111 can apply a voltage to the liquid crystal layer included in the liquid crystal optical element of the optical element 103 even during the operation of the optical axis adjustment mechanism included in the optical element 103.

Here, in order to increase the resolution in the direction parallel to the surface of the sample 105, the spot size of the light beam collected on the sample 105 is preferably as small as possible. On the other hand, by making the light beam condensed on the sample 105 into z-polarized light, the spot size of the light beam condensed on the sample 105 can be made smaller than the diffraction limit and the depth of focus can be increased. Then, the light beam transmitted through the objective lens 104 is converted to radial polarization, whereby the light beam can be converted to z polarization on the sample 105.
Therefore, in the first embodiment of the present invention, the optical element 103 is configured to change the light beam transmitted through the objective lens 104 into radial polarization.

  2A is a schematic front view of the optical element 103 according to the first embodiment of the present invention as viewed from the objective lens side, and FIG. 2B is a schematic side view of the optical element 103. FIG. 2C is a schematic cross-sectional side view of the optical element 103 viewed from the direction of the arrow AA ′ in the dotted line of FIG. The optical element 103 includes the liquid crystal optical element 3, the optical axis adjustment mechanism 4, and the housing 5, and is integrated with the objective lens 104.

  The objective lens 104 condenses the light that has been radially polarized by the liquid crystal optical element 3 onto a target object. For example, the objective lens 104 may be a single lens or a combination of a plurality of lenses. The imaging characteristics, lens configuration, shape, and size of the objective lens 104 may be determined according to the use of the objective lens, and are not limited to a specific configuration.

  One or more lenses of the objective lens 104 are fixed to the lens frame 21. Therefore, the objective lens 104 can handle all the lenses constituting the objective lens 104 as one body.

  The objective lens 104 is fixedly attached to the housing 5. Therefore, for example, screw grooves are formed in the outer periphery of the lens frame 21 of the objective lens 104 and the attachment port 51 of the housing 5 (illustration of the screw grooves is omitted). The objective lens 104 is fixed by screwing into the attachment port 51 of the housing 5. Alternatively, the objective lens 104 may be attached to the attachment port 51 of the housing 5 by any of various other fixing methods for fixing the lens to the apparatus main body using the lens. In this case, the lens frame 21 is provided with a mechanism corresponding to the fixing method.

  The liquid crystal optical element 3 is disposed in the housing 5 on the light source side relative to the objective lens 104, in other words, on the side on which the substantially parallel light beam is incident, and the optical axis adjustment mechanism 4 is configured with respect to the optical axis OA <b> 1 of the objective lens 104. It is supported so as to be relatively movable. The liquid crystal optical element 3 in the present embodiment is a polarization plane rotating element, and converts the incident linearly polarized light into radial polarized light having a radial linearly polarized light distribution centering on the optical axis OA2 of the liquid crystal optical element 3.

FIG. 3 is a schematic front view of the liquid crystal optical element 3. 4A and 4B are schematic side cross-sectional views of the liquid crystal optical element 3 taken along the dotted line viewed from the direction of the arrow XX ′ shown in FIG. 4A shows the state of the liquid crystal molecules contained in the liquid crystal optical element 3 when no voltage is applied to the liquid crystal optical element 3, and FIG. 4B shows the voltage applied to the liquid crystal optical element 3. Represents the state of liquid crystal molecules contained in the liquid crystal optical element 3 when is applied.
For convenience of explanation, it is assumed that the plane of polarization of linearly polarized light incident on the liquid crystal optical element 3 is perpendicular to the plane on which FIG. 3 is represented and is in a vertical plane, as indicated by an arrow A in FIG. .

The liquid crystal optical element 3 includes a liquid crystal layer 30 and transparent substrates 31 and 32 disposed substantially parallel to both sides of the liquid crystal layer 30 along the optical axis OA2. The liquid crystal optical element 3 includes a transparent electrode 33 disposed between the transparent substrate 31 and the liquid crystal layer 30, and a transparent electrode 34 disposed between the liquid crystal layer 30 and the transparent substrate 32. The liquid crystal molecules 37 contained in the liquid crystal layer 30 are sealed between the transparent substrates 31 and 32 and the seal member 38. The transparent substrates 31 and 32 are formed of a material that is transparent to light having a wavelength included in a predetermined wavelength range, such as glass or resin. In addition, the transparent electrodes 33 and 34 are formed of, for example, a material in which tin oxide is added to indium oxide called ITO. Further, an alignment film 35 is disposed between the transparent electrode 33 and the liquid crystal layer 30. An alignment film 36 is disposed between the transparent electrode 34 and the liquid crystal layer 30. These alignment films 35 and 36 align the liquid crystal molecules 37 in a predetermined direction. Note that the alignment films 35 and 36 may be omitted when alignment is performed by a method that does not use an alignment film, such as a structure alignment in which a structure is formed on the substrate side and the liquid crystal molecules 37 are aligned.
Further, a lens frame 39 is disposed on the outer periphery of each substrate, each transparent electrode, and each alignment film, and this lens frame 39 holds each substrate.

  The liquid crystal molecules sealed in the liquid crystal layer 30 are, for example, homogeneously aligned. Further, the liquid crystal layer 30 includes a plurality of fan-shaped regions arranged along the circumferential direction in a plane orthogonal to the optical axis OA2. The liquid crystal molecules 37 included in each fan-shaped region are aligned so that the plane of polarization of incident linearly polarized light is rotated so that the plane of polarization is substantially parallel to the radial direction centered on the optical axis OA2.

FIG. 5 is a schematic front view of the liquid crystal layer 30 showing the alignment direction of the liquid crystal in each sector region of the liquid crystal layer 30 and the polarization direction of linearly polarized light transmitted through each sector region.
In the present embodiment, the liquid crystal layer 30 includes eight sector regions 30a to 30h that are arranged clockwise and have different alignment directions, and the central angles of the sector regions 30a to 30h are set to be equal. . In FIG. 5, arrows 40 a to 40 h represent the alignment directions of the liquid crystal molecules included in the respective sector regions 30 a to 30 h. Moreover, the arrows 50a-50h represent the polarization planes of linearly polarized light emitted from the sector regions 30a-30h, respectively. Of the arrows 50a to 50h, the two arrows whose tips point in opposite directions indicate that the phases of the linearly polarized light represented by these arrows are shifted from each other by π.
A straight line that bisects the fan-shaped region through the intersection c ₁ between the optical axis OA2 and the liquid crystal layer 30 is referred to as a center line of the fan-shaped region.

The orientation direction of each of the sector regions 30a to 30h is determined so that, for example, the polarization plane of the linearly polarized component after passing through each sector region is parallel to the center line of the transmitted sector region. Therefore, through the intersection c _1, a fan-shaped region 30a that intersect the plane parallel to the polarization plane A of the incident linearly polarized light as the first region, the n-th sector area from the sector region 30a in a clockwise or counter-clockwise , The angle θ formed by the orientation direction of the sector region and the polarization plane A of the polarization component passing through the sector region 30a is set according to the following equation.
θ = 360 ° × (n-1) / (2N) (n = 1,2, ..., N) (1)
However, N is the total number of sector regions, and N = 8 in this embodiment.

  For example, in a sector region 30a where n = 1, θ = 0. That is, in the sector region 30a, the orientation direction of the liquid crystal molecules is set substantially parallel to the incident polarization plane A of the linearly polarized light so that the linearly polarized light is transmitted without rotating.

When the nth sector region is the nth region clockwise with the sector region 30a as the first region, the polarization direction of the polarization component passing through the orientation direction of each of the sector regions 30b to 30h and the sector region 30a. The angles formed by A are 22.5 °, 45 °, 67.5 °, 90 °, 112.5 °, 135 °, and 157.5 ° with the clockwise direction being positive, and the orientation directions of the sector regions 30b to 30h are respectively Is set.
Alternatively, when the nth sector region is the nth region counterclockwise from the sector region 30a, the orientation direction of each of the sector regions 30b to 30h and the polarization plane A of the polarization component passing through the sector region 30a are formed. Each of the sector regions 30b to 30h has an angle of -157.5 °, -135 °, -112.5 °, -90 °, -67.5 °, -45 °, and -22.5 ° with the clockwise direction being positive. The orientation direction is set.

The transparent electrodes 33 and 34 are disposed so as to face each other across the liquid crystal layer 30. A predetermined voltage is applied between the transparent electrodes 33 and 34 by the drive circuit 111 so that the fan-shaped regions 30a to 30h of the liquid crystal layer 30 function as a half-wave plate for wavelengths included in the predetermined wavelength region. Is done.
Here, when a voltage is applied between the transparent electrodes 33 and 34, the liquid crystal molecules are inclined in a direction parallel to the direction in which the voltage is applied according to the voltage. If the angle formed by the major axis direction of the liquid crystal molecules and the direction in which the voltage is applied is ψ, the light transmitted through the liquid crystal layer 30 forms an angle ψ with respect to the major axis direction. At this time, when the refractive index of the liquid crystal molecules with respect to a polarization component parallel to the direction in which liquid crystal molecules are oriented to the n _[psi, a _{n o ≦ n ψ ≦ n e} . Where n _o is the refractive index for the polarization component orthogonal to the major axis direction of the liquid crystal molecule (ie, ordinary ray), and _ne is the refraction for the polarization component parallel to the major axis direction of the liquid crystal molecule (ie, extraordinary ray). Rate.

Therefore, when the liquid crystal molecules contained in the liquid crystal layer 30 are homogeneously aligned and the thickness of the liquid crystal layer 30 is d, the polarization component parallel to the alignment direction of the liquid crystal molecules and the polarization component orthogonal to the alignment direction of the liquid crystal molecules An optical path length difference Δnd (= n _ψ dn _o d) occurs between Therefore, by adjusting the voltage applied between the transparent electrodes 33 and 34, the optical path length difference between the polarization component parallel to the alignment direction of the liquid crystal molecules and the polarization component orthogonal to the alignment direction of the liquid crystal molecules can be adjusted. . Therefore, for example, by adjusting the voltage applied between the transparent electrodes 33 and 34 by the drive circuit 111, each of the sector regions 30a to 30h functions as a half-wave plate for a desired wavelength.

  When each of the sector regions 30a to 30h functions as a half-wave plate, when linearly polarized light having a polarization plane having an angle θ with respect to the alignment direction of the liquid crystal molecules 37 is transmitted through the sector regions, the polarization plane is transmitted through the sector shape. Rotate to make an angle -θ with respect to the orientation direction of the region. That is, the polarization plane rotates by an angle 2θ with the orientation direction as the center.

In the example shown in FIG. 5, the orientation direction of the liquid crystal molecules in each of the sector regions 30 a to 30 h is such that the angle with respect to the polarization plane A of linearly polarized light incident on the sector region 30 a is the center line of each sector region and the sector of the liquid crystal layer 30. The angle is set to be ½ of the angle with the polarization plane A of linearly polarized light incident on the region 30a. Therefore, with respect to the direction facing upward from the intersection c ₁ along the polarization plane A of the incident linearly polarized light, when a positive clockwise angle of the polarization plane of the linearly polarized light component transmitted through the respective sector regions 30a~30h is , 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, and 315 °, respectively. As described above, the light beam emitted from the liquid crystal optical element 3 has a radial linearly polarized light component centered on the optical axis OA2.

Incidentally, the polarization plane polarized light component transmitted through the respective sector regions 30 a to 30 h, may be radially distributed around the intersection c _1, its plane of polarization, be non-parallel to the center line of the transmitted Sector Region Good. The alignment direction of respective sector regions 30a~30h may be set so that the polarization plane of the polarized light transmitted through the respective sector regions 30a~30h is parallel to the predetermined straight line passing through the fan-shaped area and the intersection c _1. For example, a value obtained by adding a predetermined offset value to the value obtained by the above formula (1), where the angle formed by the orientation direction of each of the sector regions 30a to 30h and the polarization plane A of linearly polarized light incident on the sector region 30a The orientation direction of each of the sector regions 30a to 30h may be set so that In this case, the predetermined offset value is an angle obtained by adding twice the offset value to the angle formed by the center line of each of the sector regions 30a to 30h and the polarization plane A (that is, the polarization plane of the polarization component transmitted through the sector region). And the plane of polarization of linearly polarized light incident on the sector region 30a) is set to ± 5 °, for example, so that the boundary between the adjacent sector region and the plane of polarization A does not exceed.

  Further, the number of regions having different alignment directions included in the liquid crystal layer 30 of the liquid crystal optical element 3 is not limited to eight. The number of regions having different alignment directions of the liquid crystal layer 30 may be any number necessary for obtaining the effect of radial polarization. For example, the liquid crystal layer 30 may have 4, 5, 6, or 16 regions having different alignment directions.

FIG. 6 is a schematic front view showing the alignment direction of the liquid crystal in each sector region and the polarization direction of linearly polarized light transmitted through each region when the liquid crystal layer 30 includes six sector regions 30i to 30n. Also in this modification, the transparent electrodes 33 and 34 are arranged so as to face each other across the liquid crystal layer 30.
In this modification, the arrows 40i to 40n represent the alignment directions of the liquid crystal molecules included in the sector regions 30i to 30n, respectively. Moreover, the arrows 50i-50n represent the polarization planes of linearly polarized light emitted from the sector regions 30i-30n, respectively. Of the arrows 50i to 50n, two arrows whose tip ends are directed in opposite directions indicate that the phases of the linearly polarized light represented by the arrows are shifted from each other by π.

Among the sector areas 30I～30n, the sector regions 30i located above the intersection c ₁ of the optical axis OA and the liquid crystal layer 30, and the polarization plane A of the incident linearly polarized light, and the center line of the fan-shaped region 30i coincides . Therefore, the sector area 30i is set as the first area. At this time, the orientation direction of the nth sector region in the clockwise direction is set so that, for example, an angle formed by the orientation direction and the polarization plane A is an angle calculated according to the above equation (1).
In this case, the angles formed by the orientation directions of the sector regions 30i to 30n and the polarization plane A of the polarization component passing through the sector region 30a are 0 °, 30 °, 60 °, 90 °, respectively, with the clockwise direction being positive. 120 ° and 150 °.

Also in this case, the wavelength of the incident light is between the transparent electrodes 33 and 34 sandwiching the sector regions 30i to 30n so that the liquid crystal layer 30 functions as a half-wave plate with respect to the linearly polarized light transmitted through the sector regions 30i to 30n. A voltage corresponding to is applied.
As a result, when the clockwise direction is defined as a positive direction with reference to the upward direction from the intersection c ₁ along the polarization plane of the incident linearly polarized light, the angle of the polarization plane of the linearly polarized component transmitted through each of the sector regions 30i to 30n is , 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °, respectively. As described above, the light beam emitted from the liquid crystal optical element 3 has a radial linearly polarized light component centered on the optical axis OA2.

FIG. 7 is a diagram illustrating an example of a voltage applied to the liquid crystal layer 30 between the transparent electrodes 33 and 34 and a difference in optical path length between an ordinary ray and an extraordinary ray generated by the liquid crystal layer 30.
In FIG. 7, the horizontal axis represents the voltage applied to the liquid crystal layer 30, and the vertical axis represents the optical path length difference. A graph 701 represents the relationship between applied voltage and optical path length difference for light having a wavelength of 405 nm. Graph 702 represents the relationship between applied voltage and optical path length difference for light having a wavelength of 650 nm. A graph 703 represents the relationship between the applied voltage and the optical path length difference for light having a wavelength of 780 nm.

For example, in order to make the liquid crystal layer 30 function as a half-wave plate for light having a wavelength of 405 nm, a voltage that causes an optical path length difference obtained by adding 202.5 nm to an integral multiple of 405 nm is applied between the transparent electrodes 33 and 34. It only has to be done. Therefore, referring to the graph 701, a voltage of about 1.4 Vrms corresponding to an optical path length difference of 1012.5 nm may be applied between the transparent electrodes 33 and.
In addition, for example, in order to make the liquid crystal layer 30 function as a half-wave plate for light having a wavelength of 650 nm, there is a voltage that causes an optical path length difference between the transparent electrodes 33 and 34 by adding 325 nm to an integral multiple of 650 nm. It may be applied. Therefore, referring to the graph 702, a voltage of about 1.5 Vrms corresponding to the optical path length difference of 975 nm may be applied between the transparent electrodes 33 and 34.
Furthermore, for example, in order to make the liquid crystal layer 30 function as a half-wave plate for light having a wavelength of 780 nm, a voltage that causes an optical path length difference between the transparent electrodes 33 and 34 by adding 390 nm to an integral multiple of 780 nm. It may be applied. Therefore, referring to the graph 703, a voltage of about 1.1 Vrms corresponding to the optical path length difference of 1170 nm may be applied between the transparent electrodes 33 and.

The optical axis adjustment mechanism 4 moves the liquid crystal optical element 3 relative to the objective lens 104 so that the optical axis OA2 of the liquid crystal optical element 3 coincides with the optical axis OA1 of the objective lens 104 attached to the housing 5. Support as possible.
Therefore, in the present embodiment, the optical axis adjustment mechanism 4 includes a translational movement mechanism 41 and a tilt adjustment mechanism 42.

  In the present embodiment, the translational movement mechanism 41 is configured by a so-called XY stage. The XY stage has two stages that are parallel to a plane orthogonal to the optical axis OA1 of the objective lens 104 attached to the housing 5 and can move independently along two axes orthogonal to each other. The liquid crystal optical element 3 is fixedly mounted on the XY stage. Further, in the substantially central part of the two stages of the XY stage, for example, a substantially circular penetration having a diameter larger than the pupil diameter of the objective lens 104 so as not to block the light beam passing through the objective lens 104 and the liquid crystal optical element 3. A hole is formed.

  The XY stage can be, for example, a cross roller type XY stage. However, the XY stage included in the optical axis adjusting mechanism 4 may be any of various other XY stages such as a screw feed type or a linear ball type. Further, for example, the XY stage is arranged so that adjustment members such as adjustment screws for adjusting the position of each stage of the XY stage are located outside the casing 5 through through holes provided in the side wall of the casing 5. Is done. Then, when the user operates the adjustment member, the liquid crystal optical element 3 on the XY stage moves in a plane orthogonal to the optical axis OA1 of the objective lens 104. The translation mechanism 41 may include an electric drive element such as a motor or a piezo element as an adjustment member for each stage. In this case, for example, each stage moves when the electric drive element operates according to a control signal from the controller 110 or the drive circuit 111.

  Further, the optical axis adjustment mechanism 4 includes a tilt adjustment mechanism 42 for adjusting the inclination of the optical axis OA2 of the liquid crystal optical element 3 with respect to the optical axis OA1 of the objective lens 104. In the present embodiment, the tilt adjusting mechanism 42 is a feed that is inserted into the through hole of the outer wall of the housing 5 arranged at the apex of the equilateral triangle with the center of the attachment port 51 as the approximate center of gravity around the attachment port 51. Screws 42a to 42c are provided. And the front-end | tip of each feed screw 42a-42c is fixed to the base of XY stage. When the feed screws 42 a to 42 c are rotated, the positions of the tips of the feed screws 42 a to 42 c are moved along a direction substantially parallel to the optical axis OA <b> 1 of the objective lens 104 according to the amount of rotation. Then, when any one of the feed screws 42a to 42c is rotated, the XY stage has the amount of movement of the tip of the feed screw with the straight line connected by the portion fixed by the other two feed screws as the rotation axis. Rotate by the corresponding amount. As a result, the optical axis OA2 of the liquid crystal optical element 3 disposed on the XY stage is inclined with respect to the optical axis OA1 by an angle corresponding to the rotation amount of the XY stage. Therefore, the user adjusts the inclination of the optical axis OA2 so that the optical axis OA2 of the liquid crystal optical element 3 is substantially parallel to the optical axis OA1 of the objective lens 104 by operating the feed screws 42a to 42c. it can.

  Note that the optical axis adjustment mechanism 4 may not have the tilt adjustment mechanism 42. In this case, the XY stage constituting the translation adjusting mechanism 41 may be fixed to the inside of the outer wall where the attachment port 51 of the objective lens 104 of the housing 5 is formed, for example, with a screw or an adhesive. Further, the optical axis adjustment mechanism 4 may not have the translation adjustment mechanism 41. In this case, the optical axis adjustment mechanism 4 has, for example, a stage having a substantially circular opening having a diameter larger than the pupil diameter of the objective lens 104 instead of the XY stage, and the liquid crystal optical element 3 is placed on the stage. Be placed.

  The housing 5 is formed in a hollow shape so that the liquid crystal optical element 3 and the optical axis adjusting mechanism 4 can be accommodated therein. For example, the housing 5 is made of metal or resin. As described above, the attachment port 51 for the objective lens 104 is formed on one outer wall of the housing 5. Further, the light beam passing through the objective lens 104 and the liquid crystal optical element 3 is not obstructed on the outer wall (the upper outer wall in FIGS. 2B and 2C) on the side facing the outer wall in which the attachment port 51 is formed. Thus, the through hole 52 having a diameter larger than the pupil diameter of the objective lens 104 is formed. Around the through hole 52, a substantially cylindrical protrusion 53 is formed with a thread groove formed on the outer periphery for attaching the housing 5 to a light irradiation device using the objective lens 104. In addition, the protrusion part 53 should just have a structure according to the attachment mechanism of the objective lens by the side of a light irradiation apparatus, for example, the attachment mechanism of a revolver.

  Further, the housing 5 may be formed by, for example, two members that are separated into an upper side and a lower side in FIG. 2B so that the liquid crystal optical element 3 can be placed on the XY stage in the housing 5. Alternatively, any one of the side walls of the housing 5 may be formed with an extraction port having a size that allows the liquid crystal optical element 3 to be inserted into the housing 5 or taken out from the housing 5.

Hereinafter, the assembly procedure of the optical element according to the present embodiment will be described with reference to FIG.
First, the objective lens 104 is attached to the attachment port 51 of the housing 5 (step S101). Next, the liquid crystal optical element 3 is attached to the optical axis adjusting mechanism 4 in the housing 5 (step S102). Note that the liquid crystal optical element may be attached before the objective lens is attached.
Then, the entire housing 5 is attached to an optical axis adjusting device having an observation optical system capable of observing the liquid crystal optical element 3 so that the liquid crystal optical element 3 is positioned closer to the observation optical system than the objective lens 104 (step S103). . For example, the optical axis adjusting device may be the laser microscope 100 itself shown in FIG. In this case, the housing 5 is attached to the attachment position of the objective lens of the laser microscope 100. The optical axis adjusting device has, for example, a mechanism capable of adjusting the position of the housing 5, and by operating the mechanism, the optical axis of the objective lens 104 is a predetermined position on the image plane of the observation optical system, for example, a field of view. The housing 5 is attached so as to be located at the center of the. The alignment of the optical axis of the objective lens 104 and the optical axis of the observation optical system may be performed in accordance with a general optical axis adjustment procedure used for adjusting the optical axis of the optical system. For example, the position of the housing 5 may be adjusted so that the position of the image of the light source placed at the object point of the observation optical system incorporating the objective lens 104 becomes a predetermined position.

  Then, for example, by illuminating the liquid crystal optical element 3 through the objective lens 104, the optical axis OA2 of the liquid crystal optical element 3 is objective while observing the image of the liquid crystal optical element 3 formed on the image plane of the observation optical system. The optical axis adjustment mechanism 4 is operated to adjust the relative position of the liquid crystal optical element 3 with respect to the objective lens 104 so as to coincide with the optical axis OA1 of the lens 104 (step S104). The optical axis OA1 of the objective lens 104 is, for example, the center of the field of view on the image plane.

Here, for example, when the liquid crystal optical element 3 is illuminated with linearly polarized light from the focal side of the objective lens 104 via the objective lens 104, the polarization direction is rotated for each sector region by transmitting the linearly polarized light through the liquid crystal optical element 3. Therefore, on the image plane of the observation optical system, the brightness differs for each sector region of the liquid crystal optical element 3. Therefore, the boundary of each sector area is observed on the image plane. Then, it can be seen that the center where the boundary intersects is the position of the optical axis OA2. The optical axis adjusting device may have an analyzer between the liquid crystal optical element 3 and the observation optical system. By disposing the analyzer, the difference in brightness of the image for each sector area on the image plane becomes clearer. Therefore, since it becomes easier for the user to observe the boundary of the fan-shaped region, the position of the optical axis OA2 of the liquid crystal optical element 3 can be specified more accurately. As a result, the optical axis OA1 of the objective lens 104 and the liquid crystal optical element 3 It becomes easy to match the optical axes OA2.
Further, the optical axis adjusting device may include a two-dimensional image sensor disposed on the image plane of the observation optical system. In this case, an image showing the image of the liquid crystal optical element 3 is generated by the image sensor. The user may adjust the position of the liquid crystal optical element 3 while observing the image on, for example, a display device connected to the optical axis adjusting device.

  Further, when the optical axis adjusting device is a laser confocal microscope such as the laser microscope 100, the inventor condenses the laser light emitted from the light source of the laser confocal microscope by the objective lens 104. When the condensing surface is scanned while changing the direction of the laser light emitted from the light source with a galvano mirror, for example, without placing anything on the surface, the intensity of light from each point on the condensing surface is changed to the value of the corresponding pixel. The knowledge that the image of each fan-shaped area | region of the liquid crystal optical element 3 was reflected in the image obtained by doing this was acquired. Therefore, while observing the image, the user overlaps the position of the pixel on the image corresponding to the optical axis OA1 of the objective lens 104 so that the image of the intersection of the centers of the fan-shaped regions corresponding to the optical axis OA2 overlaps. The position of the liquid crystal optical element 3 may be adjusted by operating the optical axis adjustment mechanism 4.

  As described above, the optical element according to the first embodiment of the present invention can align the optical axis of the liquid crystal optical element and the optical axis of the objective lens only by adjusting the position of the liquid crystal optical element. This facilitates alignment adjustment between the liquid crystal optical element and the objective lens. This optical element enables the user to handle the liquid crystal optical element and the objective lens having the same optical axis in an integrated manner. Therefore, this optical element can reduce the labor of alignment adjustment for incorporating the objective lens and the liquid crystal optical element into the microscope apparatus in which the objective lens and the liquid crystal optical element are incorporated.

Next, an optical element according to the second embodiment will be described. This optical element has a phase inversion element together with a polarization plane rotating element as a liquid crystal optical element. The optical axis adjustment mechanism of this optical element is arranged such that the position of the polarization plane rotating element and the phase inverting element is set so that the optical axis of the polarization plane rotating element and the optical axis of the phase inverting element are aligned with the optical axis of the objective lens, respectively. Can be adjusted independently.
In the following description, differences from the optical element according to the first embodiment among the optical elements according to the second embodiment will be described.

  FIG. 9A is a schematic side view of the optical element 10 according to the second embodiment of the present invention, and FIG. 9B is a vertical direction as viewed from the direction of the arrow BB ′ in FIG. FIG. 9C is a schematic cross-sectional side view of the optical element 10 taken along the dotted line, and FIG. 9C is a schematic cross-sectional view of the optical element 10 taken along the horizontal dotted line viewed from the direction of the arrow CC ′ in FIG. FIG. The optical element 10 includes a polarization plane rotating element 12, a phase inverting element 13, an optical axis adjusting mechanism 14, and a housing 15, and is integrated with the objective lens 104.

  Similar to the optical element 1 according to the first embodiment, the objective lens 104 is attached to an attachment port provided on one of the outer walls of the housing 15. Further, the pupil diameter of the objective lens 104 is not blocked on the outer wall of the housing 15 on the side facing the outer wall to which the objective lens 104 is attached so as not to block the light beam passing through the objective lens 104, the polarization plane rotating element 12, and the phase inverting element 13. A through hole having a larger diameter is formed. Around the through hole, there is formed a substantially cylindrical protrusion having a screw groove formed on the outer periphery for attaching the housing 15 to the laser microscope 100 shown in FIG.

In addition, guide grooves 151 and 152 for holding the polarization plane rotating element 12 and the phase inverting element 13 are formed inside the side wall of the housing 15. The guide groove 151 has a width along the inner periphery of the housing 15 so that the polarization plane rotating element 12 can be inserted so as to be parallel to a surface orthogonal to the optical axis OA1 of the objective lens 104 attached to the housing 15. Formed as follows. Similarly, the guide groove 152 is located farther from the objective lens 12 than the guide groove 151, and is parallel to a surface orthogonal to the optical axis OA <b> 1 of the objective lens 104 attached to the casing 15. And a width that allows the phase inversion element 13 to be inserted.
Also, one of the side walls of the housing 15 can be removed from the housing 15 body so that the polarization plane rotating element 12 and the phase inverting element 13 can be inserted into the housing 15 along the guide grooves 151 and 152. It may be.

  The polarization plane rotating element 12 is, for example, a liquid crystal optical element similar to the liquid crystal optical element 3 according to the first embodiment, and converts incident linearly polarized light into radial polarized light. The polarization plane rotating element 12 is inserted into the guide groove 151 so that its optical axis OA2 is substantially parallel to the optical axis OA1 of the objective lens 104 attached to the housing 15.

  The phase reversal element 13 is a part of a plurality of concentric annular zones centered on the optical axis OA3 of the phase reversal element 13 that emits linearly polarized light emitted from the light source of the light irradiation device and incident on the phase reversal element 13. The phase of the light passing through is reversed with respect to the phase of the light passing through the other annular zone. The phase inverting element 13 is inserted into the guide groove 152 so that the optical axis OA3 thereof is substantially parallel to the optical axis OA1 of the objective lens 104 attached to the housing 15. Therefore, the light emitted from the light source of the light irradiation device and transmitted through the phase inversion element 13 (in the example shown in FIG. 9B, light transmitted through the phase inversion element 13 from the upper side to the lower side) is rotated on the plane of polarization. After being converted into radial polarized light by the element 12, it is condensed through the objective lens 104. Thereby, the light condensed by the objective lens 104 becomes better z-polarized light than the light condensed by the radial polarized light generated only by the polarization plane rotating element.

  FIG. 10A is a schematic front view of an example of the phase inverting element, and FIG. 10B is a schematic front view of another example of the phase inverting element. Note that the phase inverting element shown in FIG. 10A and the phase inverting element shown in FIG. 10B are different only in the structure of the ring-shaped electrode. Details of the ring-shaped electrode will be described later. 11 (a) and 11 (b) are schematic side cross-sectional views of the phase inverting element 13 along the lines indicated by arrows Y and Y 'shown in FIG. 10 (a) or 10 (b), respectively. FIG. 11A shows a state of liquid crystal molecules included in the phase inverting element 13 when no voltage is applied to the phase inverting element 13, and FIG. 11B shows a voltage applied to the phase inverting element 13. Represents the state of liquid crystal molecules contained in the phase inversion element 13 when is applied.

The phase inverting element 13 inverts the phase of at least one annular zone centering on the optical axis OA3 with respect to the phase of the other portion of the incident linearly polarized light. For this purpose, the phase inverting element 13 includes a liquid crystal layer 130 and transparent substrates 131 and 132 disposed substantially parallel to both sides of the liquid crystal layer 130 along the optical axis OA3. Liquid crystal molecules 137 included in the liquid crystal layer 130 are sealed between the transparent substrates 131 and 132 and the seal member 138. The phase inverting element 13 includes a transparent electrode 133 disposed between the transparent substrate 131 and the liquid crystal layer 130, and a transparent electrode 134 disposed between the liquid crystal layer 130 and the transparent substrate 132. The transparent substrates 131 and 132 are formed of a material that is transparent to light having a wavelength included in a predetermined wavelength range, such as glass or resin. The transparent electrodes 133 and 134 are made of, for example, ITO. An alignment film 135 is disposed between the transparent electrode 133 and the liquid crystal layer 130. An alignment film 136 is disposed between the transparent electrode 134 and the liquid crystal layer 130. These alignment films 135 and 136 align the liquid crystal molecules 137 in a predetermined direction. Note that in the case where the liquid crystal molecules 137 are aligned by a method that does not use an alignment film, such as structural alignment, the alignment films 135 and 136 may be omitted.
Further, a lens frame 139 is arranged on the outer periphery of each substrate, each transparent electrode, and each alignment film, and this lens frame 139 holds each substrate.

  As shown in FIG. 11A, the liquid crystal molecules 137 sealed in the liquid crystal layer 130 are, for example, homogeneously aligned and aligned in a direction substantially parallel to the polarization plane of incident linearly polarized light.

Referring again to FIG. 10 (a) or FIG. 10 (b), the transparent electrode 133 includes at least a concentric circular center electrode 133a centered on the intersection c ₂ of the optical axis OA3 and the phase inversion element 2. One ring-shaped electrode. In this example, the transparent electrode 133 has five annular electrodes 133b to 133f around the center electrode 133a. Further, it is preferable that the gap between the electrodes is small. On the other hand, the transparent electrode 134 is formed so as to cover the entire liquid crystal layer 130. As a result, the liquid crystal layer 130 has a first ring-shaped portion sandwiched between the center electrode 133a, the even-numbered ring-shaped electrodes 133c and 133e from the center and the transparent electrode 134, and the odd-numbered ring-shaped electrodes from the center. Any one of 133b, 133d, and 133f and the second ring-shaped portion sandwiched between the transparent electrodes 134 are alternately formed concentrically.
The transparent electrode 134 may have the same shape as that of the transparent electrode 133, or the transparent electrode 134 has at least one ring-shaped shape that is concentric, and the transparent electrode 133 is the liquid crystal layer 130. You may form so that the whole may be covered.

  In the example shown in FIG. 10A, wirings are drawn from the respective ring-shaped electrodes so that the circular center electrode and each ring-shaped electrode can be controlled independently. It is connected. In the example shown in FIG. 10B, the even-numbered ring-shaped electrodes and the odd-numbered ring-shaped electrodes are electrically connected by the same wiring in order from the circular center electrode 133a. The wiring connected to the ring-shaped electrode and the wiring connected to the odd-numbered ring-shaped electrode are connected to the drive circuit 111, respectively. As a result, the even-numbered annular electrodes can be driven with the same potential. Similarly, each of the odd-numbered annular electrodes can be driven with the same potential. Further, in FIG. 10B, one of the odd-numbered ring-shaped electrode groups and the even-numbered ring-shaped electrode groups may not be electrically controlled. In this case, by applying a voltage between the other electrode group and the transparent electrode 134, the phase of light can be reversed by the liquid crystal layer sandwiched between the other electrode group and the transparent electrode 134. . Since the ring-shaped electrode is also thick, the phase of the light that has passed through the ring-shaped electrode is shifted from the phase of the light that does not pass through the ring-shaped electrode. Therefore, as shown in FIG. 10A and FIG. 10B, not only the ring-shaped electrodes used for voltage control but also the ring-shaped electrodes that do not require voltage control are arranged, thereby the phase inversion element 13. In the case where no voltage is applied to the liquid crystal layer 130, almost the entire light beam transmitted through the phase inverting element 13 can be in phase.

  Furthermore, the potential of the even-numbered or odd-numbered ring-shaped electrode group that does not need to be electrically controlled is the same reference potential as the transparent electrode 134 provided on the transparent substrate on the side facing the ring-shaped electrode group, Alternatively, it is preferable to set the threshold potential, which is the maximum potential at which the liquid crystal molecules in the liquid crystal layer 130 do not operate. The threshold potential is generally about 1 V to 2 V in terms of effective voltage. By setting the potential of the ring-shaped electrode group that does not need to be electrically controlled in this way, the phase inversion element 13 can control the potential of the liquid crystal layer 130 to be constant. It is possible to prevent the liquid crystal 137 from malfunctioning. Further, by setting the potential of the ring-shaped electrode group that does not need to be electrically controlled to the threshold potential, thermal fluctuation of the liquid crystal layer 130 can also be suppressed.

  As shown in FIG. 11B, the drive circuit 111 places between the center electrode 133a and the even-numbered ring-shaped electrodes 133c and 133e and the transparent electrode 134 disposed so as to face each other with the liquid crystal layer 130 interposed therebetween. When a voltage is applied, the major axis direction of the liquid crystal molecules contained in the first ring-shaped portion 130a sandwiched between the electrodes approaches from the direction perpendicular to the optical axis OA3 to the direction parallel to the optical axis OA3. The liquid crystal molecules tilt. On the other hand, if no voltage is applied between the odd-numbered ring-shaped electrodes 133b, 133d, 133f and the transparent electrode 134, the liquid crystal molecules contained in the second ring-shaped portion 130b sandwiched between these electrodes are Its long axis remains in the direction perpendicular to the optical axis OA3.

Here, when a voltage is applied between a part of the electrodes of the transparent electrode 133 and 134, the major axis direction of the liquid crystal molecules included in the first annular zone 130a, the direction in which the voltage is applied, That is, if the angle formed by the direction of the optical axis OA is ψ, the light transmitted through the liquid crystal layer 130 forms an angle ψ with respect to the major axis direction of the liquid crystal molecules 137. At this time, when the refractive index of the liquid crystal molecules with respect to a polarization component parallel to the direction in which the liquid crystal molecules 137 is oriented to n _[psi, a _{n o ≦ n ψ ≦ n e} . Therefore, when the liquid crystal molecules 137 included in the liquid crystal layer 130 are homogeneously aligned and the thickness of the liquid crystal layer 130 is d, the polarization component passing through the first annular portion 130a of the liquid crystal layer 130, and the first between the polarization components passing through the second annular portion 130b, the optical path length difference _{Δnd (= n ψ d- n e} d) occurs. The phase difference Δ generated between these two polarization components is 2πΔnd / λ. Note that λ is the wavelength of light incident on the liquid crystal layer 130.

  As described above, by adjusting the voltage applied between the transparent electrode 133 and the transparent electrode 134, the phase inversion element 13 can modulate the phase of light transmitted through the liquid crystal layer 130. Therefore, when a predetermined voltage corresponding to the wavelength of incident light is applied between the transparent electrode 133 and the transparent electrode 134, the phase inversion element 13 changes the phase of the light passing through the first annular zone portion 130a. The phase of the light passing through the second annular portion 130b can be shifted by π.

  The optical axis adjusting mechanism 14 includes a translation adjusting mechanism 141 for adjusting the position of the polarization plane rotating element 12 and a translation adjusting mechanism 142 for adjusting the position of the phase inverting element 13. Since the translation adjustment mechanisms 141 and 142 have the same structure, the translation adjustment mechanism 141 will be described below.

The translation adjustment mechanism 141 includes two elastic members 1411 and 1412 and two shaft position adjustment members 1413 and 1414.
The elastic member 1411 is inserted into a hole 151a formed in one of the side walls of the housing 5 in the guide groove 151 along a direction substantially parallel to a plane orthogonal to the optical axis OA1. Similarly, the elastic member 1412 has a hole 151b formed in the guide groove 151 along a direction substantially parallel to the surface orthogonal to the optical axis OA1 in one of the side walls adjacent to the side wall in which the hole 151a is formed. Inserted. One end of each of the elastic members 1411 and 1412 is in contact with the bottom surface of each of the holes 151a and 151b (that is, the surface on the side wall side of the housing 15 in the guide groove 151), and the other end of each of the elastic members 1411 and 1412 is a polarization plane rotating member. It is in contact with the outer periphery of the element 12. The elastic member 1411 biases the polarization plane rotating element 12 toward the side wall on the side facing the side wall where the hole 151a is formed. The elastic member 1412 urges the polarization plane rotating element 12 toward the side wall facing the side wall where the hole 151b is formed. That is, the direction urged by the elastic member 1412 is substantially orthogonal to the direction urged by the elastic member 1411.
Each of the elastic members 1411 and 1412 can be, for example, a coil spring or a spring plunger.

  The shaft position adjusting member 1413 is, for example, a screw-like member having a screw groove formed on the outer periphery, and a guide groove is formed on the side wall of the casing 15 on the side facing the side wall where the hole 151a into which the elastic member 1411 is inserted is formed. It is inserted into a through-hole 151 c formed so as to penetrate from the bottom surface of 151 toward the outside of the housing 15. A thread groove is also formed on the inner periphery of the through hole 151c, and the shaft position adjusting member 1413 and the through hole 151c are screwed together.

  The tip of the shaft position adjusting member 1413 is in contact with the outer periphery of the polarization plane rotating element 12 on the side opposite to the side on which the elastic member 1411 is in contact. When the shaft position adjusting member 1413 is rotated, for example, clockwise about its center line as a rotation axis, the tip of the shaft position adjusting member 1413 moves to the inside of the housing 15, that is, to the left along the horizontal direction in FIG. Move towards. As a result, the polarization plane rotating element 12 is also pressed by the axial position adjusting member 1413 and moves toward the elastic member 1411. On the other hand, when the shaft position adjusting member 1413 is rotated counterclockwise with its center line as the rotation axis, the tip of the shaft position adjusting member 1413 moves to the outside of the housing 15, that is, along the horizontal direction in FIG. Move to the right. As described above, since the polarization plane rotating element 12 is urged toward the side wall in which the through hole 151c is formed by the elastic member 1411, the tip of the shaft position adjusting member 1413 moves toward the outside of the housing 15. Accordingly, the polarization plane rotating element 12 also moves toward the side wall in which the through hole 151c is formed (that is, to the right side in FIG. 9C).

  Similarly, the shaft position adjusting member 1414 is, for example, a screw-like member having a thread groove formed on the outer periphery, and is formed on the side wall of the casing 15 on the side facing the side wall where the hole 151b into which the elastic member 1412 is inserted is formed. The guide groove 151 is inserted into a through-hole 151 d formed so as to penetrate from the bottom surface of the guide groove 151 toward the outside of the housing 15. A thread groove is also formed on the inner periphery of the through hole 151d, and the shaft position adjusting member 1414 and the through hole 151d are screwed together.

  The tip of the shaft position adjusting member 1414 is in contact with the outer periphery of the polarization plane rotating element 12 on the side opposite to the side on which the elastic member 1412 is in contact. When the shaft position adjusting member 1414 is rotated clockwise, for example, with its center line as the rotation axis, the tip of the shaft position adjusting member 1414 moves downward into the housing 15, that is, along the vertical direction in FIG. 9C. Move towards. As a result, the polarization plane rotating element 12 is also pressed by the axial position adjusting member 1414 and moves toward the elastic member 1412. Conversely, when the shaft position adjusting member 1414 is rotated counterclockwise with the center line as the rotation axis, the tip of the shaft position adjusting member 1414 moves to the outside of the housing 5, that is, along the vertical direction in FIG. 9C. Move upwards. As described above, since the polarization plane rotating element 12 is urged toward the side wall in which the through hole 151d is formed by the elastic member 1412, the tip of the shaft position adjusting member 1414 moves toward the outside of the housing 15. Accordingly, the polarization plane rotating element 12 also moves toward the side wall in which the through-hole 151d is formed (that is, upward in FIG. 9C).

  In this way, by rotating the axis position adjusting members 1413 and 1414, the polarization plane rotating element 12 moves in two directions orthogonal to each other within a plane orthogonal to the optical axis OA1 of the objective lens 104. Therefore, the translation adjustment mechanism 141 can match the optical axis OA2 of the polarization plane rotating element 12 with the optical axis OA1 of the objective lens 104.

  Note that the shaft position adjusting members 1413 and 1414 may not be screw-shaped members. For example, the shaft position adjusting members 1413 and 1414 may be piezoelectric elements. In this case, one end of the shaft position adjusting members 1413 and 1414 is in contact with the outer periphery of the polarization plane rotating element 12, and the other end of the shaft position adjusting members 1413 and 1414 is fixed inside the side wall of the housing 5. In this case, by changing the voltage applied to the piezo element from the controller 110 or the drive circuit 111, the length of the piezo element also changes. Therefore, the polarization plane rotating element 12 moves in a plane orthogonal to the optical axis OA1 of the objective lens 104 in accordance with a change in the length of the piezoelectric element. Therefore, by appropriately adjusting the voltage applied to the piezoelectric elements of the axial position adjusting members 1413 and 1414, the translation adjusting mechanism 141 causes the optical axis OA2 of the polarization plane rotating element 12 to coincide with the optical axis OA1 of the objective lens 104. be able to.

  Also for the optical element 10 according to the second embodiment, the optical axes of the polarization plane rotating element 12 and the phase inverting element 13 which are liquid crystal optical elements are attached to the housing 15 by the same procedure as the assembly procedure shown in FIG. The optical element 10 can be assembled so as to coincide with the optical axis of the objective lens 104 thus obtained.

  However, when making the optical axis of the phase inverting element 13 coincide with the optical axis of the objective lens 104, a voltage is applied from the drive circuit 111 (not shown) to the liquid crystal layer of the phase inverting element 13. As a result, an image having different brightness for each annular zone having a different phase according to the pattern of the transparent electrode can be observed through the observation optical system of the optical axis position adjusting device. Therefore, the user may adjust the position of the phase inverting element 13 by operating the translation adjustment mechanism 142 so that the center of the image of the annular zone overlaps the position corresponding to the optical axis of the objective lens.

  Next, an optical element according to a third embodiment of the present invention will be described. The optical element according to the third embodiment includes, as a liquid crystal optical element, a phase modulation element that controls the phase of a transmitted light beam so as to correct wavefront aberration generated in an optical system including an objective lens. The optical element according to the third embodiment is different from the optical element according to the first embodiment in that the function of the phase modulation element housed in the housing 5 and the structure of the transparent electrode included in the phase modulation element are liquid crystals. It differs from the function of the optical element 3 and the structure of the transparent electrode of the liquid crystal optical element 3. In the third embodiment, the liquid crystal optical element included in the optical element is only a phase modulation element. Therefore, hereinafter, the function of the phase modulation element, the transparent electrode included in the phase modulation element, and the related portion will be described. Regarding points other than the transparent electrode included in the phase modulation element according to the third embodiment, the optical axis adjustment mechanism, and the housing, refer to the description of the corresponding components in the first embodiment.

  Similarly to the liquid crystal optical element according to the first embodiment, the phase modulation element included in the optical element according to the third embodiment also includes two transparent substrates and a liquid crystal layer sandwiched between the transparent substrates. The liquid crystal molecules sealed in the liquid crystal layer are, for example, homogeneously aligned. Further, a transparent electrode is provided between the liquid crystal layer and each transparent substrate. By adjusting a voltage applied between the two transparent electrodes, a laser beam is transmitted to the light beam transmitted through the liquid crystal optical element. A phase distribution for canceling aberration generated in the optical system of the microscope 100 is given.

FIG. 12 is a schematic front view of a phase modulation element illustrating an example of one structure of two transparent electrodes included in the phase modulation element according to the third embodiment. The other of the two transparent electrodes of the phase modulation element is formed so as to cover the entire liquid crystal layer, for example. Alternatively, both transparent electrodes may have the shape shown in FIG.
As shown in FIG. 12, the transparent electrode 71 includes a circular electrode 71 a centering on an intersection c ₀ of the optical axis of the phase modulation element 7 and the phase modulation element 7, and a plurality of concentric ring-shaped electrodes. 71b to 71i. The outer periphery of the ring-shaped electrode 71i corresponds to the outer periphery of the active region where the liquid crystal molecules are driven. The diameter of the active region is designed so as to substantially match the pupil diameter of the objective lens 104, for example.

  In the example shown in FIG. 12, the wiring is drawn out from the circular electrode 71a and each of the annular electrodes 71b to 71i so that the circular electrode 71a and each of the annular electrodes 71b to 71i can be controlled independently, The wiring is connected to the drive circuit 111. Furthermore, the circular electrode 71a and the annular electrodes 71b to 71i are insulated by being arranged apart from each other. Then, by controlling the voltage applied to the liquid crystal layer by the circular electrode 71a and the annular electrodes 71b to 71i, for each annular portion of the liquid crystal layer corresponding to the circular electrode 71a and the annular electrodes 71b to 71i. The optical path length can be changed. As a result, the optical element can give a desired concentric phase distribution to the light beam passing through the phase modulation element 7.

  The diameter of the circular electrode 71a and the width of each of the annular electrodes 71b to 71i are set by, for example, dividing a desired phase distribution profile along the diameter direction of the light beam at equal phase intervals. That is, it is preferable that the zone corresponding to the position where the change in the phase modulation amount with respect to the change in distance from the optical axis is large is set narrower.

  Each of the circular electrode 71a and each of the annular electrodes 71b to 71i may be connected to an adjacent annular electrode by an electrode (resistor) having the same electrical resistance. In this case, the annular electrode corresponding to the position where the phase modulation amount is maximized and the position where the phase modulation amount is minimized is determined from the desired phase distribution. A potential corresponding to the maximum phase modulation amount is applied to the annular electrode or the circular electrode at the position where the phase modulation amount is maximum, while the annular electrode or circle at the position where the phase modulation amount is minimum. A potential corresponding to the minimum phase modulation amount is applied to the electrode. As a result, the potential difference between adjacent annular electrodes becomes the same by resistance division. Therefore, the liquid crystal optical element can be driven by a simple driving circuit rather than independently driving each annular electrode.

  FIGS. 13A and 13B are diagrams illustrating examples of electrodes to which a voltage is applied in the phase modulation element 7 according to the third embodiment. 13 (a) and 13 (b), the electrode 71a is a central circular electrode, and the annular electrode 71i is the outermost annular electrode. The annular electrode 71m, which is one of the annular electrodes 71b to 71h, represents an annular electrode to which the highest potential is applied. Adjacent annular electrodes are connected by a resistance R.

  In FIG. 13A, each electrode is driven by a two-level voltage. The same lowest potential V1 is applied to the center circular electrode 71a and the outermost annular electrode 71i, while the highest potential V2 is applied to the annular electrode 71m. By selecting a defocus value between the spot focused by the objective lens 104 and the observation target position so that the phase at the center and the end in the phase distribution of the wavefront aberration generated in the optical system of the laser microscope 100 becomes equal, The phase of the light beam passing through the central circular electrode 71a and the phase of the light beam passing through the outermost ring electrode 71i can be matched. In this case, as shown in FIG. 13A, even if the potentials applied to the center circular electrode 71a and the outermost ring electrode 71i are the same, the phase modulation amount that can cancel the phase distribution due to wavefront aberration is set to the liquid crystal layer. Can be generated. As described above, in the example of the two-level driving, by changing the potential difference between the lowest potential V1 and the highest potential V2, the region corresponding to each annular electrode in the liquid crystal layer is changed without changing the shape of the phase modulation profile. The magnitude of the phase modulation amount can be changed.

  In contrast, in FIG. 13B, each electrode is driven by a three-level voltage. In this configuration, a potential V3 different from the potential V1 applied to the circular electrode 71a is applied to the outermost ring electrode 71i. As described above, an objective lens having a different numerical aperture NA was used as the objective lens 104 by applying a potential V3 different from the potential V1 so that an arbitrary phase modulation amount is generated also in the outermost ring electrode 71i. Even in this case, the phase modulation element 7 can cause the liquid crystal layer to have a different phase modulation amount distribution for each objective lens. Therefore, the phase modulation element 7 can compensate the wavefront aberration with high accuracy according to the objective lens used.

FIG. 14 (a) shows an example of the distribution of voltage applied between each annular electrode of the liquid crystal optical element and the transparent electrode facing it in order to correct wavefront aberration caused by the optical system including the objective lens. FIG. 14B is a diagram illustrating an example of the distribution of the phase modulation amount generated by the phase modulation element 7 in accordance with the voltage distribution illustrated in FIG. 14A and 14B, the horizontal axis represents the distance from the optical axis OA, and the regions 71a to 71i correspond to the circular electrode 71a and the annular electrodes 71b to 71i, respectively. In FIG. 14A, the vertical axis represents the voltage applied between the electrodes. A graph 1401 represents a voltage distribution according to the distance from the optical axis. On the other hand, in FIG. 14B, the vertical axis represents the amount of phase modulation, and represents that the phase is delayed toward the bottom. A graph 1402 represents the distribution of the phase modulation amount generated by the phase modulation element 7 according to the distance from the optical axis. In this example, since the phase modulation amounts at the center and the outermost circumference are different, the liquid crystal optical element is preferably driven with three levels of voltage.
As shown in graphs 1401 and 1402, the amount of phase modulation increases as the voltage between the electrodes increases.

  Each time the objective lens is replaced, the potentials V1, V2, and V3 applied to the circular electrode 71a, the annular electrode 71m, and the annular electrode 71i are canceled so that the phase distribution corresponding to the wavefront aberration generated in the optical system is canceled. A ratio is set. For final voltage adjustment, for example, while looking at the image manually, the controller obtains information such as contrast obtained from the image, and automatically sets the optimum potential while feeding back the information to the applied potential. May be.

  Note that a general laser microscope includes a plurality of laser light sources having different wavelengths, and a necessary phase modulation amount is different for each laser light source. The difference in the amount of phase modulation due to the difference in wavelength can be dealt with by changing the voltage applied to the liquid crystal layer. Further, the difference in phase modulation amount due to temperature change or the like can be canceled by adjusting the applied voltage.

  As described above, the phase modulation element 7 in this embodiment also provides a phase modulation amount with the optical axis of the phase modulation element 7 itself as the rotation center, so that the optical axis of the objective lens and the optical axis of the phase modulation element 7 are If they do not match, the phase modulation element 7 may not be able to appropriately correct the wavefront aberration generated in the optical system including the objective lens. Therefore, also in this embodiment, it is preferable that the optical axis of the objective lens 104 coincides with the optical axis of the phase modulation element 7.

  Also for the optical element according to the third embodiment, the optical axis of the phase modulation element 7 matches the optical axis of the objective lens 104 attached to the housing by the same procedure as the assembly procedure shown in FIG. The optical element can be assembled.

  However, in the third embodiment, when the optical axis of the phase modulation element 7 coincides with the optical axis of the objective lens 104, the optical axis of the phase inverting element 13 in the second embodiment is set to the light of the objective lens 104. As in the case of matching with the axis, by applying a voltage different for each annular electrode from the driving circuit 111 to the liquid crystal layer of the phase modulation element 7, the luminous flux transmitted through the liquid crystal layer is applied to the annular electrode. The optical axis adjustment mechanism 4 may be operated so that the center of the image of the annular zone overlaps with the position corresponding to the optical axis of the objective lens 104 in a state where an image with different brightness can be observed for each corresponding annular zone portion.

  The optical element may include a plurality of phase modulation elements arranged along the optical axis direction of the objective lens 104 as a liquid crystal optical element. Each phase modulation element may give different distributions of phase modulation amounts to the light beams transmitted through the phase modulation element so as to correct different types of wavefront aberrations.

  Each phase modulation element can have the same configuration as the phase modulation element 7 according to the third embodiment, for example. The phase modulation elements are arranged so that the alignment directions of the liquid crystal molecules sealed in the liquid crystal layers of the phase modulation elements are parallel to each other. Each phase modulation element may have concentric annular electrodes as shown in FIG. 12, for example, as in the liquid crystal optical element according to the third embodiment. Even in this case, the potential applied to each annular electrode of one of the two phase modulation elements is made different from the potential applied to each annular electrode of the other phase modulation element. The modulation element may give a distribution of the phase modulation amount for correcting the third-order spherical aberration to the light beam, and the other phase modulation element may give the distribution of the phase modulation amount for correcting the fifth-order spherical aberration to the light beam.

  Alternatively, the transparent electrode patterns included in the two phase modulation elements may be different from each other.

  FIG. 15 is a schematic front view showing an example of the structure of one of the two transparent electrodes of one of the two phase modulation elements according to this modification. Note that the liquid crystal molecules sealed in the liquid crystal layer included in the phase modulation element are aligned along a direction orthogonal to the x-axis in FIG. The other of the two transparent electrodes included in the phase modulation element is formed so as to cover the entire liquid crystal layer, for example. Alternatively, both transparent electrodes may have the shape shown in FIG. In this modification as well, the other phase modulation element can have the same configuration as the liquid crystal optical element according to the third embodiment, for example.

  The transparent electrode 72 shown in FIG. 15 is optimized so as to give the distribution of the phase modulation amount suitable for correcting the coma aberration generated in the optical system of the laser microscope 100 to the light beam transmitted through the phase modulation element. Yes. As shown in FIG. 15, two electrodes 72 a and 72 b for advancing the phase to an inner region 722 that enters a predetermined distance (for example, 50 μm) from the effective diameter 721 of the light beam incident on the phase modulation element, Two electrodes 72c and 72d for delaying the phase are arranged. Further, a reference electrode 72e for applying a reference voltage is disposed in the inner region 721 where the electrodes 72a to 72d are not disposed. Although not shown for simplification, a space is provided between the electrodes and is insulated from each other.

  When a positive (+) potential is applied to the electrodes 72a and 72b with respect to a reference potential (for example, 0 V) applied to the reference electrode 72e, a potential difference is generated between the transparent electrodes facing each other with the liquid crystal layer interposed therebetween, and the liquid crystal therebetween. The orientation changes in accordance with the potential difference. Therefore, the light beam passing through this portion is subjected to an action that can advance its phase. Further, when a negative (−) potential is applied to the electrodes 72c and 72d with respect to the reference potential applied to the reference electrode 72e, a potential difference is generated between the opposing transparent electrodes with the liquid crystal layer interposed therebetween, and the liquid crystal between them The orientation changes according to the potential difference. Therefore, the light beam passing through this portion is subjected to an action that delays its phase.

  As a result, by appropriately adjusting the potential applied to each electrode, the phase modulation element responds to coma aberration with respect to the light beam obliquely incident on the objective lens 104 along the x-axis direction in FIG. A phase modulation amount distribution that cancels the phase distribution of the light beam can be provided.

  According to still another modification, the optical element includes a phase modulation element having the electrode pattern shown in FIG. 15 and an electrode obtained by rotating the electrode pattern shown in FIG. 15 by 90 degrees around the optical axis. And a phase modulation element having a pattern. Thereby, the light modulation element can correct coma aberration of a light beam obliquely incident on the objective lens not only in the x-axis direction in FIG. 15 but also in any direction.

In the case of an optical element having two phase modulation elements as in these modified examples, each phase modulation element is light having the same configuration as the optical axis adjustment mechanism 14 and the casing 15 of the optical element according to the second embodiment. It can be held by the shaft adjusting mechanism and the housing.
Also in the case of this modification, when the optical axis of each phase modulation element is made to coincide with the optical axis of the objective lens, the liquid crystal layer of the phase modulation element that makes the optical axis coincide with the optical axis of the objective lens Apply voltage. Then, the user estimates the position of the optical axis of the phase modulation element from the positional relationship between the electrode pattern and the optical axis of the phase modulation element while observing the electrode pattern obtained by applying the voltage. The optical axis adjustment mechanism may be operated so that the estimated position is aligned with the optical axis of the objective lens.

  According to another modification, even if the optical element has only a polarization plane rotating element as the liquid crystal optical element as in the first embodiment, the optical axis of the liquid crystal optical element is the optical axis of the objective lens. In order to align, the optical element may have the optical axis adjustment mechanism according to the second embodiment.

  Further, the entire optical axis adjusting mechanism or a part thereof may be removable from the housing. For example, in the second embodiment, after the optical axes of the polarization plane rotating element and the phase inverting element are aligned with the optical axis of the objective lens, the polarization plane rotating element and the phase inverting element are formed of, for example, an adhesive. Used to fix to the housing. Thereafter, the shaft position adjusting member of the optical axis adjusting mechanism is removed from the housing. By configuring the optical axis adjustment mechanism in this way, a part or all of the optical axis adjustment mechanism can be used as a jig that can be used in common for a plurality of optical elements according to the present invention. The number of parts of the optical element itself is reduced, and as a result, the cost of the optical element is reduced.

  Further, when the optical element has a plurality of liquid crystal optical elements, the liquid crystal optical elements are integrated by previously matching the optical axes of the liquid crystal optical elements, and then the integrated liquid crystal optical element is changed to the first embodiment. May be placed in the enclosure. For example, the liquid crystal optical element according to the first embodiment may be one in which a polarization plane rotating element and a phase conversion element are integrated. In this case, the optical axis of the polarization plane rotation element and the optical axis of the phase conversion element are aligned in advance. Therefore, for example, the polarization plane rotation element and the phase inversion element are supported by one casing. The casing may have the same structure as the casing of the optical element according to the second embodiment, for example. However, the housing does not need to have a protrusion for attaching the objective lens mounting opening and the housing to the light irradiation device. Instead, a substantially circular opening having a diameter larger than the diameter of the light beam passing through the polarization plane rotation element and the phase inversion element is formed in the housing on the outer wall substantially parallel to the polarization plane rotation element and the phase inversion element. It only has to be done. In addition, since only one of the polarization plane rotation element and the phase inversion element needs to be movable with respect to the other, the casing includes either one of the polarization plane rotation element and the phase inversion element as shown in FIG. The translation adjustment mechanism as shown in FIG.

  In order to make the optical axis of the polarization plane rotation element coincide with the optical axis of the phase inversion element, for example, a housing that supports the polarization plane rotation element and the phase inversion element is attached to the optical axis adjustment device as described above. Then, the user observes the image of the polarization plane rotation element and the image of the phase inversion element formed by the observation optical system of the optical axis adjustment device, and each sector area corresponding to the optical axis of the polarization plane rotation element. The plane-of-polarization rotating element or the phase inversion element may be moved so that the intersection of the two boundaries coincides with the center of the concentric ring zone of the phase inversion element corresponding to the optical axis of the phase inversion element.

  Furthermore, the objective lens, the liquid crystal optical element, and the optical axis adjustment mechanism may be directly attached to the light irradiation device. In this case, the component that supports the liquid crystal optical element and the optical axis adjustment mechanism may be a component that is separate from the component that supports the objective lens.

  Note that the objective lens integrated with the optical element according to each of the above-described embodiments or modifications thereof may not be an objective lens for a microscope. For example, the objective lens may be an objective lens used in a laser processing apparatus or an interferometer. The optical element according to each of the above-described embodiments or modifications thereof can be suitably used for various light irradiation apparatuses such as a laser processing apparatus or an interferometer.

  As described above, those skilled in the art can make various modifications in accordance with the embodiment to be implemented within the scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Laser microscope 101 Laser light source 102 Collimating optical system 103 Optical element 104 Objective lens 105 Sample 106 Beam splitter 107 Confocal optical system 108 Confocal pinhole 109 Detector 110 Controller 111 Driving circuit 10 Optical element 3 and 12 Polarizing plane rotation element ( Liquid crystal optical element)
13 Phase reversal element (liquid crystal optical element)
7 Phase modulation element (liquid crystal optical element)
4, 14 Optical axis adjustment mechanism 41 Translation adjustment mechanism 42 Tilt adjustment mechanism 42a-42c Feed screw 141, 142 Translation adjustment mechanism 1411, 1412 Elastic member 1413, 1414 Axis position adjustment member 5, 15 Housing 51 Objective lens attachment port 151, 152 Guide groove 30, 130 Liquid crystal layer 31, 32, 131, 132 Transparent substrate 33, 34, 133, 134 Transparent electrode 35, 36, 135, 136 Alignment film 37, 137 Liquid crystal molecule 38, 138 Seal member 39, 139 Mirror frame

Claims (13)

A liquid crystal layer that is disposed closer to the light source than the objective lens and includes liquid crystal molecules, and two first transparent electrodes that are disposed to face each other with the liquid crystal layer interposed therebetween, and transmit through the liquid crystal layer A first liquid crystal optical that controls the phase or plane of polarization of a linearly polarized light emitted from the light source by applying a voltage corresponding to the predetermined wavelength between the two first transparent electrodes. Elements,
An optical axis adjustment mechanism capable of moving the first liquid crystal optical element relative to the objective lens so that the optical axis of the first liquid crystal optical element can be aligned with the optical axis of the objective lens;
An optical element.   The optical axis adjustment mechanism is parallel to a plane orthogonal to the optical axis of the objective lens and is capable of moving the first liquid crystal optical element in a first direction and a second direction orthogonal to each other. The optical element according to claim 1, further comprising an adjustment mechanism.   The optical element according to claim 1, wherein the optical axis adjustment mechanism includes a tilt adjustment mechanism that can adjust an inclination of an optical axis of the first liquid crystal optical element with respect to an optical axis of the objective lens.   The optical element according to any one of claims 1 to 3, further comprising a housing that integrally holds the objective lens and the first liquid crystal optical element.   The said housing further has an attachment part which attaches the said housing to the microscope apparatus which has the said light source so that the said 1st liquid crystal optical element may be arrange | positioned near the said light source rather than the said objective lens. Optical elements. A second liquid crystal optical element disposed closer to the light source than the first liquid crystal optical element;
Second light that can move the second liquid crystal optical element independently of the first liquid crystal optical element so that the optical axis of the second liquid crystal optical element can be aligned with the optical axis of the objective lens. The optical element according to claim 1, further comprising an axis adjustment mechanism.   The second liquid crystal optical element transmits the phase of the incident light transmitted through a part of the plurality of concentric ring zones centered on the optical axis of the second liquid crystal optical element to another ring. The optical element according to claim 6, wherein the optical element is inverted with respect to a phase of the incident light transmitted through the band. The liquid crystal layer of the first liquid crystal optical element has a plurality of regions arranged along a circumferential direction around the optical axis of the first liquid crystal optical element, and each of the plurality of regions The alignment directions of the liquid crystal molecules contained are different from each other,
Each of the plurality of regions of the liquid crystal layer has a polarization plane of a component transmitted through the region of the linearly polarized light by applying a voltage according to the predetermined wavelength between the two transparent electrodes. , According to the alignment direction of the liquid crystal molecules contained in the region, rotate to be parallel to the radial direction centered on the optical axis of the first liquid crystal optical element,
The optical element as described in any one of Claims 1-7. One of the two first transparent electrodes of the first liquid crystal optical element is arranged corresponding to each of a plurality of concentric annular zones centered on the optical axis of the first liquid crystal optical element. A plurality of annular electrodes,
The first liquid crystal optical element is configured such that, for each of the plurality of annular electrodes, a different voltage is applied between the annular electrode and the other of the two first transparent electrodes. The optical element according to claim 1, wherein a phase modulation amount of the linearly polarized light transmitted through the annular zone is controlled for each annular zone. The optical element is disposed in an optical system having the light source and the objective lens,
For each of the plurality of annular electrodes, to generate a phase modulation amount of the linearly polarized light that passes through each of the plurality of annular zones so as to cancel the phase distribution of wavefront aberration generated in the optical system. A driving device that adjusts a voltage applied between the annular electrode and the other of the two first transparent electrodes, and the driving device is configured to operate the optical axis adjustment mechanism during operation of the two second axis electrodes; The optical element of Claim 9 comprised so that a voltage can be applied between one transparent electrode. A plurality of regions arranged along a circumferential direction centering on the first optical axis, and transmitting each of the plurality of regions through a polarization plane of linearly polarized light emitted from a light source having a predetermined wavelength Thus, a liquid crystal optical element that is rotated so as to be parallel to the radial direction centered on the first optical axis is disposed on the light source side of the objective lens,
An image of the plurality of regions of the liquid crystal optical element is formed on an image plane of the optical system by a predetermined optical system, and the center of the image of the plurality of regions corresponds to the second optical axis of the objective lens. By moving the liquid crystal optical element relative to the objective lens so as to coincide with the position on the image plane, the first optical axis of the liquid crystal optical element is shifted to the second light of the objective lens. A method of assembling an optical element, wherein the optical element is aligned with a shaft. A first transparent electrode, a second transparent electrode that is disposed to face the first transparent electrode, and has a predetermined positional relationship with respect to the first optical axis; and the first transparent electrode A liquid crystal layer containing liquid crystal molecules sandwiched between an electrode and the second transparent electrode, and the phase of linearly polarized light having a predetermined wavelength emitted from a light source that passes through the liquid crystal layer, A liquid crystal optical element that is controlled by applying a voltage according to the predetermined wavelength between the first transparent electrode and the second transparent electrode is disposed closer to the light source than the objective lens,
Applying a voltage between the first transparent electrode and the second transparent electrode;
An image of the pattern of the first transparent electrode is formed on the image plane of the optical system by a predetermined optical system, and a point in the predetermined positional relationship with the image corresponds to the second optical axis of the objective lens The liquid crystal optical element is moved relative to the objective lens so as to coincide with the position on the image plane, so that the first optical axis of the liquid crystal optical element is the first of the objective lens. A method of assembling an optical element, wherein the optical element is aligned with the optical axis of No. 2. A light source that outputs linearly polarized light having a predetermined wavelength;
An optical element for controlling the phase or plane of polarization of the linearly polarized light;
An objective lens for condensing the light beam transmitted through the optical element at a predetermined spot of the sample;
A light receiving element for receiving light from the predetermined spot;
Have
The optical element is
A liquid crystal layer including liquid crystal molecules; and two first transparent electrodes arranged to face each other with the liquid crystal layer interposed therebetween, and having a predetermined wavelength emitted from the light source that transmits the liquid crystal layer A liquid crystal optical element that controls the phase or polarization plane of linearly polarized light by applying a voltage corresponding to the predetermined wavelength between the two first transparent electrodes;
An optical axis adjustment mechanism capable of moving the liquid crystal optical element relative to the objective lens so that the optical axis of the liquid crystal optical element can be aligned with the optical axis of the objective lens;
A housing that integrally holds the objective lens and the liquid crystal optical element;
A microscope apparatus characterized by comprising:

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