JPH11326860A - Wave front converting element and laser scanner using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wave-front converting element and a laser scanner using it, which can scan focal positions of a luminous flux in the direction of the optical axis without using mechanical mechanism, and offsetting the aberration caused in such a case. SOLUTION: This laser scanner has a luminous flux branching element 2 arranged in an optical path of a laser beam flux 1, a beam expander 3, a wave- front converting element 4 capable of changing a wave-front form of the light as necessary, an object lens 5 for converging the light on a specimen side 6, a detector 8, and a control device 9. The wave-front converting element 4 consists of liquid crystal elements constituted so that each micro-divided region can be controlled independently by a control device 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a wavefront conversion element capable of arbitrarily converting the wavefront shape of light, and a laser scanning device using the element.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a three-dimensional image of a specimen, for example, in a scanning laser microscope, the specimen or an objective lens is mechanically moved in the optical axis direction, and an optical image on each surface inside the specimen is sequentially formed. I needed to take it. However, with this method, it is difficult to realize accurate scanning in the optical axis direction in terms of position control errors and reproducibility due to mechanical movement.
In the case of sample scanning, there is a problem that high-speed scanning cannot be performed if the sample is large. Further, when the specimen is a biological specimen or the like and the objective lens is directly immersed in a living body or a culture solution to observe a high-speed movement of the living body, scanning the objective lens causes
This adversely affects the specimen to be observed, such as vibration, which is not preferable. Further, when the refractive index of the immersion medium of the objective lens is different from the refractive index of the specimen, there is a problem that the resolution is reduced due to the aberration (spherical aberration) generated due to the movement of the focusing position. .

On the other hand, as an optical element capable of changing the power (wavefront shape), a liquid crystal lens, a liquid lens, or a combination thereof is known. In particular, a liquid crystal is used to change a focal length and a focal position. Examples of the method include those disclosed in JP-A-5-93895, JP-A-5-100201, and JP-A-5-53089. Also, as a method of changing the magnification using liquid crystal,
Japanese Unexamined Patent Application Publication No. 9-318909 discloses a liquid crystal lens in which the electrodes are arranged in an annular shape as a means for changing the optical characteristics of the liquid crystal lens. A control method is used. Note that, in these prior examples, there is no mention at all of how aberrations generated as a whole by changing the power when the liquid crystal lens is used in combination with a plurality of other optical systems.

[0004] As for the liquid lens, Japanese Patent Laid-Open No. 8-1
Although it is disclosed in, for example, Japanese Patent Application Publication No. 14703, there is no mention at all in the case of using the optical system in combination with a plurality of optical systems as to how aberration generated as a whole due to a change in power is handled.

[0005] Adaptive optics is used, for example, when used in a telescope to cancel the wavefront turbulence of light due to fluctuations in the atmosphere. In addition, when used in a microscope, adaptive optics is used when light passes through a sample. It is used for the purpose of canceling the wavefront disturbance of the light, and it is used only for the purpose of canceling the wavefront (aberration) that has been disturbed. By giving power to it, the focal position of the optical system changes. It is not used from the point of view of letting it do. Furthermore,
In terms of aberration correction, it does not specifically show how to perform aberration correction.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems and circumstances of the prior art, and an object thereof is to provide a method without using a mechanical mechanism. A wavefront conversion element capable of scanning the light-converging position of the light beam in the direction of the optical axis, canceling out aberrations occurring at that time, and reducing deterioration of light-collecting performance and imaging performance due to scanning, and a wavefront conversion element using the same. To provide a laser scanning device.

[0007]

In order to achieve the above object, a wavefront conversion element according to the present invention comprises a liquid crystal element configured so that each of the finely divided regions can be controlled independently. Is changed, the wavefront shape of the light transmitted therethrough or reflected therefrom can be appropriately changed.

According to the present invention, each of the regions has a matrix shape or a fan shape.

In order to achieve the above object, a laser scanning device according to the present invention focuses light emitted from a laser at a sample position using an optical system, and scans the focused position in the optical axis direction. The laser scanning device according to any one of claims 1 to 3, further comprising an optical element capable of canceling out aberrations caused by the scanning.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing an embodiment of the present invention, referring to FIG. 1, an aberration (spherical aberration) generated by the scanning in the optical axis direction and a aberration for canceling the aberration will be described. The aspherical characteristic will be described.

In general, when the light wavefront is defocused by an aberration-free lens, the wavefront collapse is vertically (front-back) symmetric with respect to the focal point position, and the degree of the collapse is NA (numerical aperture).
Becomes larger as it goes toward the periphery (peripheral portion when viewed from the pupil), so that the aspherical power for canceling it needs to be increased as it goes to the periphery, that is, as the distance from the optical axis increases.
In FIG. 1, the traveling direction of light is drawn in reverse to the actual direction for easy understanding. That is, light is drawn from the focal position of the objective lens and the defocused positions before and after the focal position. Here, the light beam coming out of the focal position F of the objective lens is emitted from the objective lens as collimated light having no aberration, that is, a plane wave. On the other hand, the light beam that has come out of the point A defocused to the front side is emitted from the objective lens as a convergent light beam.
Since the bending at a large portion (peripheral portion of the luminous flux) becomes large, in order to return this to a collimated light having no aberration, that is, a plane wave, an aspheric lens having concave power and having a concave power that becomes stronger toward the periphery is used. An optical element having characteristics equivalent to the above is required.

Conversely, the light beam that has exited from the point B defocused rearward is divergent light, but its wavefront has a large bend at the portion where the NA is large due to the influence of aberration. In order to return to light, an optical element having characteristics equivalent to an aspherical lens that has a convex power and becomes stronger toward the periphery is required. In general, when a collimated light beam is condensed by a single lens, the power of a thick general spherical lens increases toward the periphery, and spherical aberration occurs at the focal position. It is known that in order to correct this, it is possible to collect light with no aberration by making the power weaker toward the periphery by making it aspherical, but when canceling out the aberration caused by defocus, The opposite is true.

Although an actual objective lens or the like is not necessarily aberration-free, when a high-precision objective lens used in a laser microscope is used with quasi-monochromatic light such as laser light, the objective lens becomes substantially aberration-free. It can be considered applicable.
Further, when the refractive index of the immersion medium of the objective lens is smaller than the refractive index of the sample (observing the sample in water with a dry objective lens), spherical aberration occurs in the direction in which the ray angle becomes gentle at the interface, The power of the aspherical surface for canceling the power needs to be increased toward the periphery, and the aspherical surface characteristic as described above is required. Further, since the amount of aberration increases with an increase in the NA of the objective lens and the amount of movement of the condensing position in the optical axis direction, the amount of aspherical surface for canceling the aberration also increases accordingly.

When the refractive index of the immersion medium of the objective lens is larger than the refractive index of the sample (observation of the sample in water with an oil immersion objective lens), the spherical aberration in the direction in which the ray angle becomes tight at the interface. Therefore, it is necessary to make the aspherical characteristic for canceling out the power weaker toward the periphery, that is, lower than the power of a spherical surface having the same paraxial curvature.
This is the opposite of the direction that cancels out the wavefront collapse when defocused, and in the case of a small NA, the aberration due to the refractive index mismatch is smaller than the aberration due to defocus.
The aspheric characteristic that cancels out the overall aberration may increase as its power moves away from the optical axis, but oil immersion objective lenses are generally used to increase the NA, and the aberrations due to the mismatch of the refractive index are generally used. Since the generation amount is extremely large, the total aberration has a tendency to generate aberration due to a refractive index mismatch, and the aspherical characteristic that cancels out the aberration decreases as the power becomes farther from the optical axis. Further, since the amount of generated aberration increases with an increase in the NA of the objective lens and the amount of movement of the condensing position in the optical axis direction, the amount of aspherical surface for canceling the aberration also increases accordingly, and the same paraxial The difference (deviation) from a spherical surface having a curvature increases.

Next, the basic structure and operation of the present invention will be described with reference to FIG. In the figure, 1 is a light beam emitted from a laser (not shown), 2 is a light beam splitting element, 3 is a beam expander, 4 is a wavefront conversion element that can change the wavefront of the light beam into an arbitrary shape, 5 is an objective lens, and 6 is an objective lens. A focal position of the objective lens 5 (a sample surface in a normal case); 7, a defocus position deviated in a direction away from the objective lens 5 from the focal position 6;
8 is a photodetector, 9 is a control device for driving the wavefront conversion element.

In FIG. 2, a light beam 1 passes through a light beam splitting element 2, is collimated to a desired size by a beam expander 3, and is incident on a wavefront conversion element 4, where the wavefront is appropriately adjusted by a control device 9. After being deformed, it is collected by the objective lens 5. In this case, when the wavefront converting element 4 is controlled by the control device 9 so as not to deform the wavefront at all, the light beam 1 is focused on the focal position 6, but the wavefront converting element 4 is controlled by the control device 9. ,
When the light beam 1 is given a wavefront deformation so as to become a diffuse beam, the light beam 1 is focused on the defocus position 7.

Normally, the objective lens 5 is designed to converge the collimated beam to the focal position 6 with substantially no aberration when the collimated beam is incident. Not only does the position shift, but also aberration occurs. Therefore, the wavefront converting element 4 has an aspherical characteristic, and can deform the wavefront of the beam so as to cancel the generated aberration. In this case, if the wavefront conversion element 4 continuously deforms the wavefront over the entire area of the divergent beam to the convergent beam, and at the same time cancels out the aberration generated at that time, the light at the condensing position of the incident beam is Scanning in the axial direction is always possible without aberration. In the case of a laser scanning microscope, light (reflected light, fluorescent light, etc.) emitted from the focusing position
Travels backward in the optical path, is reflected by the light beam branching element 2 and
Is detected by

Hereinafter, embodiments of the present invention will be described more specifically with reference to the illustrated examples. Embodiment 1 FIG. 3 is a schematic configuration diagram of a first embodiment of the laser scanning device according to the present invention. In the figure, substantially the same members as those used in FIG. 2 are denoted by the same reference numerals. Although the present embodiment has the same basic configuration as that shown in FIG. 2 and is not shown, scanning within the same test surface is performed by moving a stage. The detection system is a so-called confocal system using a confocal lens 10 and a confocal pinhole 11. Further, in this embodiment, the wavefront converting element 4 capable of changing the wavefront into an arbitrary shape is constituted by a diffractive lens composed of a homogeneous liquid crystal element, and is controlled by the liquid crystal controller 9. It has become.

A homogeneous type liquid crystal element can control its phase between zero and 2π according to the magnitude of the applied voltage. When this is used as an optical element, it can be used as a phase modulation element. Can be used. or,
Since the phase can be controlled between zero and 2π, reversing the characteristic reverses the phase, meaning that when considered as a lens element, it is possible to reverse from a convex lens to a concave lens. . It is to be noted that, even when the liquid crystal elements are arranged in a matrix or a fan shape, each element can be controlled independently, as in a normal liquid crystal.

FIG. 4 is a conceptual diagram when a diffractive lens is realized by a homogeneous type of subdivided liquid crystal. Generally, a diffractive lens is manufactured by controlling the shape (pitch) and phase in the radial direction. The information (shape and phase data in the polar coordinate system) is converted into matrix information (shape and gradation in the Cartesian coordinate system). Alternatively, it can be converted into polar coordinate information (shape and gradation in a polar coordinate system). The gradation in this case is not a normal light and dark gradation, but a phase gradation between zero and 2π. Conversely, by controlling the phase gradation of each element of the subdivided liquid crystal, an arbitrary diffraction lens can be constituted by the subdivided liquid crystal.

As shown in FIG. 5, when the diffractive lens has a shape (so-called kinoform) in which a straight line extends from a position where the phase is zero to a position where the phase becomes 2π, the diffraction efficiency is theoretically 100.
%. However, when a diffractive lens is composed of subdivided liquid crystals, it is impossible to form a kinoform, which is approximated stepwise. If there is a sufficient number of liquid crystal elements within the pitch at a large pitch, a shape equivalent to a substantially kinoform can be realized, but at a small pitch such as a peripheral portion, the number of liquid crystal elements contained therein is small. Therefore, a rough staircase approximation is obtained. In the present embodiment, the shape of the diffractive lens is limited so that at least four liquid crystal elements can enter even within the minimum pitch. Therefore, the worst case is a four-stage approximation of the kinoform, and a diffraction efficiency of about 81% can be realized. This value hardly poses a problem in practical use even in a general optical system. However, in the case of this embodiment, the unnecessary order light increased due to the decrease in the diffraction efficiency is cut by the confocal pinhole 11 at the time of detection. It doesn't matter at all.

Embodiment 2 FIG. 6 is a schematic structural view of a laser scanning device according to a second embodiment of the present invention. In the figure, substantially the same members as those used in FIG. 2 are denoted by the same reference numerals. In this embodiment, the present invention is applied to a confocal laser microscope for fluorescence observation of a beam scan method, in which a wavefront conversion element (a diffraction lens made of finely divided liquid crystal) is provided in an incident laser beam and in a detection optical path. Each of them is provided with a feature that the two liquid crystal control devices 9 are controlled in an interlocking and independent manner. Reference numeral 12 denotes a liquid crystal diffraction lens (wavefront conversion element) for excitation light, and reference numeral 13 denotes a laser. A dichroic mirror that transmits light and reflects fluorescence, 14 is a scanning optical system that scans in the X and Y directions, 15 is a pupil projection lens, 16 is an imaging lens, 17 is a liquid crystal diffraction lens for fluorescence (wavefront conversion element), Reference numeral 18 denotes a signal processing system having a magnification variation correction mechanism, 19 denotes a display, and 20 denotes an image storage device.

The light beam 1 emitted from the laser is collimated to a desired size by the beam expander 3 and enters the liquid crystal diffraction lens 12. The beam whose wavefront shape has been changed passes through the dichroic mirror 13 and is scanned by the scanning optical system 14 in both the X and Y directions. The scanned beam is condensed by the pupil projection lens 15 at the focal position of the imaging lens 16, and scanned by the imaging lens 16 and the objective lens 5 on the sample surface 6 in the XY directions. Fluorescence from the specimen surface 6 excited by the focused excitation beam travels backward in the optical path, is reflected by the dichroic mirror 13, and passes through the liquid crystal diffraction lens 17, the confocal lens 10, and the confocal pinhole 11 for fluorescence. Through the detector 8.
The detected signal is displayed on a display 19 via a signal processing system 18 and is simultaneously stored in an image storage device 20.

As in the first embodiment, scanning in the optical axis direction is performed with almost no aberration by controlling the liquid crystal diffraction lens 12 for excitation light, and the fluorescent light provided in the detection optical system is provided. By interlocking and controlling the liquid crystal diffraction lens 17 described above, diffraction lenses optimized for excitation light and fluorescence having different wavelengths can be configured. However, in the present embodiment, since the liquid crystal diffraction lens 12 is not arranged at a position completely conjugate with the pupil of the objective lens 5, the power is applied to the liquid crystal diffraction lens so that the focal length of the entire system is increased. (Magnification) changes slightly. Therefore, if an optical slice image is taken as it is, the size of the image changes depending on the slice position, and when a three-dimensional image is constructed, the shape of the sample cannot be faithfully reproduced. However, if the optical system is known, it is possible to calculate the magnification change accompanying the scanning in the optical axis direction.
It becomes possible to construct a three-dimensional image that is faithful to the shape of the sample by canceling out the magnification change.

Embodiment 3 FIG. 7 is a schematic structural view of a laser scanning device according to a third embodiment of the present invention. In the drawing, substantially the same members as those used in the above-described embodiment are denoted by the same reference numerals. In this embodiment, the present invention is applied to a multi-photon excitation fluorescence microscope of a beam scan type, and a pupil position of the objective lens 5 is projected by a relay optical system in order to eliminate a magnification change accompanying scanning in an optical axis direction. A liquid crystal subdivided lens is provided at a position, and is characterized in that it is controlled by the liquid crystal controller 9. In the figure, 21 is a liquid crystal diffraction lens (wavefront conversion element), 22 is a pupil relay optical system, 2
Reference numeral 3 denotes a detection optical system.

The light beam 1 emitted from the laser is collimated to a desired size by the beam expander 3, and the collimated light beam is scanned by the scanning optical system 14 in the XY directions. The scanned beam is condensed by the pupil projection lens 15 at the focal position of the imaging lens 16 and enters the liquid crystal diffraction lens 21 via the imaging lens 16. The luminous flux whose wavefront shape has been changed here is projected by the pupil relay optical system 22, passes through the dichroic mirror 13, and passes through the objective lens 5.
Scans the sample surface 6 in the XY directions. The fluorescence from the specimen surface 6 excited by the focused excitation beam travels backward in the optical path, is reflected by the dichroic mirror 13, and is detected by the detector 8 via the detection optical system 23.

The liquid crystal diffraction lens 21 via the control device 9
As in the first embodiment, the scanning in the optical axis direction is performed with no aberration by the operation of the first embodiment. Although the present embodiment is not a confocal system, the fluorescence itself due to multiphoton excitation is a non-linear phenomenon in itself, and occurs only near the focus of the excitation beam. Multi-photon excitation does not occur with the increased unnecessary order light, so that there is no problem at all. However, in fluorescence observation by multiphoton excitation, the wavelength range of the excitation light and the wavelength range of the fluorescence are far apart, so if there is a liquid crystal diffraction lens in the coaxial optical path, the shape is optimized for light of one wavelength. When this occurs, the diffraction efficiency of the other light decreases and does not affect the imaging characteristics, but the amount of detected light may be lost. Therefore, it is better to provide only in the excitation laser light path as in this embodiment. . In this embodiment, if the detection optical system 23 and the detector 8 are removed, and instead, for example, an observation system using normal illumination or the like is added, a laser scanning device that enables cell operation using a laser trap device or laser manipulation is provided. Become.

Embodiment 4 In this embodiment, a wavefront conversion element is obtained by adding a refraction lens 24 or a refraction surface 25 to the liquid crystal diffraction lens 21 in the third embodiment. FIGS. 8 (a) and 8 (b) An example of each is shown in FIG. In general, a diffractive lens has an inverse dispersion characteristic, and a normal refracting lens bends better as the wavelength is longer, as opposed to bending as light with a shorter wavelength. Therefore, a refraction lens 24 is added to the liquid crystal diffraction lens 21 including the diffraction surface 21a and the substrate 21b (see FIG. 8A).
Alternatively, by using the outer surface of the substrate 21b itself as a refractive lens surface (see FIG. 8B), a wavefront conversion element capable of effectively correcting chromatic aberration can be obtained.
That is, if the wavefront conversion element having such a configuration is used, even when laser beams having different wavelengths are simultaneously incident, or when laser beams having a wavelength width are incident, there is no chromatic aberration, and the condensing position of the laser beam can be adjusted. Scanning can be performed in the optical axis direction. In this case, if the wavelength is different, the diffraction efficiency is reduced, but the unnecessary order light increased with the wavelength does not adversely affect the imaging characteristics, as described in the third embodiment.

The present invention is not limited to the embodiments described above, and it goes without saying that various combinations are possible. Although only a diffraction lens made of subdivided liquid crystal has been described as an example of a wavefront conversion element, the wavefront conversion element is a Fresnel lens made of subdivided liquid crystal or an element capable of exhibiting the same characteristics as those (so-called liquid crystal). Lens or liquid lens).

As described above, the wavefront conversion element according to the present invention and the laser scanning device using the same have the features as described in the claims, and also have the following features.

(1) The phase of the minute area is controlled to form a diffraction lens.
Or the wavefront conversion element according to 2. Thereby, a phase type diffraction lens having arbitrary characteristics can be configured.

(2) The method according to (1) or (1), wherein the phase of the minute region is controlled to approximate the kinoform shape stepwise so as to have a lens function. Wavefront conversion element. This makes it possible to achieve high diffraction efficiency at a specific wavelength.

(3) The wavefront conversion element according to (1) or (2) or (1), wherein an aspherical wavefront is formed by controlling the phase of the minute area. Thereby, an arbitrary aspherical characteristic can be provided.

(4) The method according to (1) or (2) or (1), wherein the phase of the minute region is controlled to approximate the kinoform shape stepwise to form an aspherical wavefront. The wavefront conversion element according to any one of the preceding claims. Thereby, a phase type diffraction lens having arbitrary aspherical characteristics can be configured.

(5) The wavefront conversion element according to the above (2) or (4), wherein the minute regions included in the approximation of the kinoform shape are at least four regions per pitch. As a result, the kinoform, which is an ideal shape of the diffraction lens, can be approximated by at least four steps, and at the worst, a high-efficiency diffraction lens having a diffraction efficiency of 81% or more can be formed.

(6) The wavefront conversion element according to (1) or (2) or (1) to (5), wherein the liquid crystal is of a homogeneous type. As a result, a highly efficient wavefront conversion element can be realized by phase control instead of amplitude control.

(7) The optical element has a characteristic equivalent to the function of a coaxial symmetric lens, and scanning in the direction of the optical axis is enabled by a power change of the optical element.
3. The laser scanning device according to claim 1. This enables scanning of the laser beam condensing position in the optical axis direction without using a mechanical mechanism.

(8) The laser according to (3) or (7), wherein the means for canceling the aberration generated by the scanning in the optical axis direction is based on the aspherical characteristic of the optical element. Scanning device. This makes it possible to sufficiently cancel the aberration that occurs when scanning is performed in the optical axis direction.

(9) When the refractive index of the immersion medium of the objective lens and the refractive index of the sample are substantially the same, or the refractive index of the immersion medium of the objective lens is smaller than the refractive index of the sample, The spherical characteristic increases as its power moves away from the optical axis, and the amount of the spherical characteristic increases with the numerical aperture of the objective lens and the amount of movement of the condensing position in the optical axis direction with respect to the focal position of the objective lens. The laser scanning device according to claim 3 or (7) or (8), wherein the laser scanning device is increased. As a result, even when scanning is performed in the optical axis direction to obtain a three-dimensional image, which is the greatest feature of a laser microscope, it is possible to reduce the reduction in resolution due to the occurrence of aberrations associated therewith, and to obtain a favorable optical slice. An image is obtained.

(10) When the refractive index of the immersion medium of the objective lens is larger than the refractive index of the sample, the aspherical characteristic of the optical element becomes smaller as its power away from the optical axis, but the same paraxial curvature is obtained. The difference (deviation) from the spherical surface having the following is increased with an increase in the numerical aperture of the objective lens and the amount of movement of the light-collecting position in the optical axis direction based on the focal position of the objective lens. The laser scanning device according to claim 3, or (7) or (8). As a result, even when scanning is performed in the optical axis direction to obtain a three-dimensional image, which is the greatest feature of a laser microscope, it is possible to reduce the reduction in resolution due to the occurrence of aberrations associated therewith, and to obtain a favorable optical slice. An image is obtained. Further, with respect to the operation of a sample such as a laser trap, it is possible to prevent the trapping force from decreasing due to aberration.

(11) The laser device is a laser microscope that focuses light from a laser beam on a sample surface and detects light (reflected light, fluorescence, etc.) emitted from the sample surface.
4. The apparatus according to claim 3, wherein the optical member is arranged in a substantially parallel light beam in a so-called common light path between an optical member (a polarizing beam splitter or a dichroic mirror) for splitting the incident laser light beam and the detection light beam. 7) The laser scanning device according to any one of items 7 to 10. Thus, in the reflection observation or the fluorescence observation, when the wavelength of the excitation light and the wavelength of the fluorescence are close, the optical member can be shared by the illumination system and the detection system.

(12) The laser scanning device focuses light from the laser on the sample surface, and emits light (reflected light,
A laser microscope for detecting fluorescence and the like, wherein the optical element is between an optical member (a polarizing beam splitter or a dichroic mirror) for splitting an incident laser beam and a detection beam and a light source, and between the optical member and a detector. The laser scanning device according to any one of claims 3 to 7, wherein the laser scanning devices are arranged in substantially parallel light beams in both optical paths and can be independently controlled. . Thereby, even in the case of fluorescence observation in which the wavelength region of the excitation light and the wavelength region of the fluorescence are separated, the optical member can be optimized according to each wavelength region.

(13) The laser scanning device focuses the light from the laser on the sample surface and detects the fluorescence emitted by the multiphoton excitation there, or focuses the laser light on the sample surface. A laser device for performing a sample operation (trap, manipulation, etc.), wherein the optical element is arranged only in a substantially parallel light beam in an incident laser light path, wherein: The laser scanning device according to any one of 10). This makes it possible to omit unnecessary optical members in a multiphoton laser microscope in which only the condensing state of incident laser light needs to be controlled, and to optimize only necessary optical members.
Alternatively, in a laser trap device or a laser processing machine, etc., only the focusing state of the incident laser light needs to be controlled.
Unnecessary optical members can be omitted, and only necessary optical members can be optimized.

(14) The optical element capable of canceling the scanning in the direction of the optical axis and the aberration generated thereby is arranged at a position conjugate with the pupil position of the objective lens. The laser scanning device according to any one of (11) to (13). As a result, similar power addition and aberration correction based on aspherical characteristics can be performed from the on-axis light beam to the off-axis light beam, and laser scanning that does not change the magnification of the optical system even when scanning in the optical axis direction by adding power is performed. An apparatus can be provided.

(15) The optical element capable of canceling the scanning in the direction of the optical axis and the aberration generated thereby is arranged near the pupil position of the objective lens or a position conjugate with the pupil position. When a beam scanning method is used, a mechanism is provided which electrically and softly corrects a change (magnification change) in the focal length of the condensing optical system due to a change in power of the optical element when displaying an image. The laser scanning device according to any one of (11) to (13). As a result, substantially the same power addition and aberration correction based on aspherical characteristics can be performed from the on-axis light beam to the off-axis light beam, and a three-dimensional image faithful to the sample can be constructed. That is,
If the position of the optical element does not exactly coincide with the pupil position, scanning in the optical axis direction by adding power changes the focal length (magnification) of the optical system, which causes a problem when constructing a three-dimensional image. coming out. However, if the optical system is known, it is possible to calculate the magnification change accompanying the scanning in the optical axis direction,
This makes it possible to electrically or softly correct the image when displaying the image.

(16) When the optical element capable of canceling the scanning in the direction of the optical axis and the aberration caused by the scanning is not arranged at the pupil position of the objective lens or at a position conjugate with the pupil position or in the vicinity thereof The laser scanning device according to any one of (11) to (13), wherein a stage scanning method is used for scanning. As a result, the light-collecting characteristics and the image-forming characteristics need only consider the on-axis state.
In addition, it is possible to provide a laser scanning device which does not need to be concerned with a change in focal length due to scanning in the optical axis direction.

(17) The optical element capable of canceling the scanning in the direction of the optical axis and the aberration caused by the scanning is controlled so as to sequentially realize data (power and aspherical characteristics) stored in advance. 3. The method according to claim 2, wherein the light converging position is scanned in the optical axis direction.
Or the laser scanning device according to any one of (7) to (16). As a result, total system control of a device that requires scanning in the optical axis direction can be performed.

(18) A liquid crystal lens, a liquid lens, or a micromirror device whose power and shape can be freely changed by the optical element capable of canceling the scanning in the direction of the optical axis and the aberration generated thereby. Or (3) a combination thereof.
Alternatively, the laser scanning device according to any one of the above (7) to (17). Thus, scanning in the optical axis direction can be performed without using a mechanical mechanism, and the accompanying reduction in light-collecting performance and imaging performance can be eliminated.

(19) A laser light source, an objective lens for condensing a light beam from the laser light source on a sample or the like, and the wavefront conversion element according to any one of (1) to (2) or (1) to (6). And a control device for controlling the wavefront conversion element,
A laser scanning device, wherein the condensing position is scanned in an optical axis direction by controlling a phase distribution of the wavefront conversion element. This makes it possible to scan the laser beam condensing position in the optical axis direction without using a mechanical mechanism.

(20) A laser light source, an objective lens for condensing a light beam from the laser light source on a sample or the like, and the wavefront conversion element according to any one of (1) to (2) or (1) to (6). And a control device for controlling the wavefront conversion element,
A laser scanning apparatus characterized in that by controlling the phase distribution of the wavefront conversion element, the light condensing position is scanned in the direction of the optical axis, and the aberration generated by the scanning is canceled. Accordingly, scanning of the laser condensing position in the optical axis direction can be performed without using a mechanical mechanism, and aberration generated when scanning in the optical axis direction can be sufficiently canceled.

(21) The wavefront conversion element according to any one of (1) to (6) or (1) to (6), and a laser light source, an objective lens for condensing a light beam from the laser light source on a sample or the like. And a control device for controlling the wavefront conversion element, and a laser scanning apparatus characterized in that the phase distribution of the wavefront conversion element is controlled so as to cancel out aberrations caused by movement of the condensing position. . This makes it possible to scan the converging position of the laser beam in all directions of x, y, and z without using a mechanical mechanism, and to sufficiently cancel the aberration generated when scanning the laser beam. Can be.

(22) A laser light source, an objective lens for condensing a light beam from the laser light source on a sample or the like, and the wavefront conversion element according to any one of (1) to (2) or (1) to (6). And a control device for controlling the wavefront conversion element, wherein the refractive index of the immersion medium of the objective lens and the refractive index of the sample are substantially the same, or the refractive index of the immersion medium of the objective lens is When the refractive index is smaller than the aspherical characteristic of the wavefront conversion element, the power increases as the power is away from the optical axis, and the amount is based on the numerical aperture of the objective lens and the focal position of the objective lens. A laser scanning device, wherein the phase distribution of the wavefront conversion element is controlled so as to increase with an increase in the amount of movement of the focusing position in the optical axis direction. As a result, even when scanning is performed in the optical axis direction to obtain a three-dimensional image, which is the greatest feature of a laser microscope, it is possible to reduce the reduction in resolution due to the occurrence of aberrations associated therewith, and to obtain a favorable optical slice image. Can be obtained.

(23) A wavefront conversion element according to any one of (1) to (6) or (1) to (6), and a laser light source, an objective lens for condensing a light beam from the laser light source on a sample or the like. And a control device for controlling the wavefront conversion element, wherein when the refractive index of the immersion medium of the objective lens is larger than the refractive index of the sample or the like, the aspheric characteristic of the wavefront conversion element is such that the power is the optical axis. The distance (deviation) from a spherical surface having the same paraxial curvature depends on the numerical aperture of the objective lens and the amount of movement of the condensing position in the optical axis direction with respect to the focal position of the objective lens. A laser scanning apparatus, wherein the phase distribution of the wavefront conversion element is controlled so as to increase as the number of laser scanning elements increases. As a result, even when scanning is performed in the optical axis direction to obtain a three-dimensional image, which is the greatest feature of a laser microscope, it is possible to reduce the reduction in resolution due to the occurrence of aberrations associated therewith, and to obtain a good optical slice. An image can be obtained. In addition, it is possible to prevent the trapping force from being reduced due to aberration in the operation of a sample such as a laser trap.

(24) The wavefront conversion element according to any one of (1) to (2) or (1) to (6),
It is arranged in the vicinity of an optical system having a predetermined power consisting of a refracting surface, and it is possible to move the condensing position of the laser beam by the objective lens in the optical axis direction by a change in the combined power. And a laser scanning device having an aspherical characteristic such that aberration of the optical system generated by the wavefront conversion element is corrected. As a result, even when scanning in the direction of the optical axis, which is a major feature of the laser scanning device, it is possible to reduce the reduction in light-collecting performance due to the occurrence of aberrations associated with the scanning. An image can be obtained. Further, the diffractive lens has an inverse dispersion characteristic, and when combined with a normal refractive surface, chromatic aberration is effectively corrected. Therefore, by adopting this configuration, chromatic aberration does not occur even when laser beams having different wavelengths are simultaneously incident or when laser beams having a wavelength width are incident, and the focusing position of the laser beam is moved in the optical axis direction. It is possible to do. However, since the aspherical characteristics in this case have various characteristics depending on the power of the refracting surface to be combined, the aberrations generated there, the immersion medium of the objective lens used, and the state of the sample (refractive index), the characteristics must be determined without exception. Can not.

[0055]

As described above, according to the present invention, an arbitrary wavefront shape can be formed, and a certain kind of image data in a Cartesian coordinate system or a polar coordinate system is reproduced on a liquid crystal to thereby form an optical element. It is possible to provide a wavefront conversion element capable of having a function as Also, by combining with an optical system such as an objective lens, it is possible to provide a wavefront conversion element capable of canceling the movement of the light-converging position and the aberration generated thereby.

Further, according to the present invention, it is possible to scan the light condensing position in the optical axis direction without using a mechanical mechanism, and it is possible to prevent the light condensing performance from deteriorating. When applied to a microscope, it is possible to provide a laser scanning device capable of obtaining a good optical slice image of a specimen without lowering the resolution.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining spherical aberration generated in accordance with scanning of a light-converging position in the optical axis direction and aspherical characteristics for canceling the spherical aberration.

FIG. 2 is a diagram for explaining the basic configuration and operation of the laser scanning device according to the present invention.

FIG. 3 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 4 is a conceptual diagram when a diffractive lens is realized by a homogeneous-type subdivided liquid crystal.

FIG. 5 is a diagram for explaining a kinoform of a diffractive lens and its four-step approximation.

FIG. 6 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a third embodiment of the present invention.

8A and 8B are configuration diagrams of a main part of a fourth embodiment of the present invention, wherein FIG. 8A is a diagram in which a liquid crystal diffraction lens and a refractive lens are combined, and FIG.
FIG. 3 is a diagram in a case where an outer surface facing a diffraction surface of a liquid crystal diffraction lens is formed as a refraction surface.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 laser beam 2 beam splitter 3 beam expander 4 wavefront converter 5 objective lens 6 sample surface (focal position of objective lens) 7 position farther from the focal position of objective lens (direction away from objective lens) 8 detector 9 Control device 10 Confocal lens 11 Confocal pinhole 12 Liquid crystal diffraction lens (wavefront conversion element) for excitation light 13 Dichroic mirror 14 Scanning optical system 15 Pupil projection lens 16 Imaging lens 17 Liquid crystal diffraction lens for fluorescence (wavefront conversion element) ) 18 signal processing system 19 display 20 image storage device 21 diffraction lens (wavefront conversion element) made of subdivided liquid crystal 21a diffraction surface 21b substrate 22 pupil relay optical system 23 detection optical system 24 refractive lens 25 refractive surface

Claims (3)

[Claims] 1. A liquid crystal device comprising: a liquid crystal element configured so that each of finely divided regions can be independently controlled; and by changing a phase of each of the regions, a light transmitted through or reflected therefrom is changed. A wavefront conversion element capable of appropriately changing a wavefront shape. 2. The wavefront conversion device according to claim 1, wherein each of the regions has a matrix shape or a fan shape. 3. A laser scanning apparatus in which light emitted from a laser is focused on a sample position using an optical system and the focused position is scanned in the optical axis direction. A laser scanning device comprising an optical element capable of canceling out.