Optical vortex control device and optical vortex control method

Abstract

An optical vortex control device (1) is a device for controlling the movement of a microbody in a medium in a sample (90), and is provided with a light source (10), an optical vortex generation unit (20), lenses (30-33), an aperture (34), a dichroic mirror (40), an illumination unit (50), an imaging unit (60), and a control unit (70). The objective lens (30) focuses and irradiates the optical vortex generated by the optical vortex generation unit (20) onto a microbody in a medium in a sample (90), and collects light from the microbody. The imaging unit (60) captures an image of the micro-body that moves as a result of light trapping, and outputs image data. The control unit (70) analyzes the movement of the microbody on the basis of the image data, adjusts the phase distribution of the optical vortex generated by the optical vortex generation unit (20) on the basis of the analysis result, and controls the movement of the microbody. As a result, an optical vortex control device capable of easily generating a desired optical vortex is achieved.

Description

Technical Field

[0001] The invention relates to an optical vortex control device and an optical vortex control method. Background Art

[0002] A technique for trapping light from a microbody in a medium using an optical vortex is known. The optical vortex has a phase singularity on the propagation axis and a ring-shaped light intensity distribution in which the light intensity on the propagation axis is zero and the light intensity is maximum at a certain distance from the propagation axis.

[0003] In addition to having a ring-shaped light intensity distribution, the optical vortex is also characterized by having orbital angular momentum. If an optical vortex with orbital angular momentum is irradiated onto a microbody in a medium, the microbody receives angular momentum from the optical vortex and rotates along an orbit with high light intensity around the propagation axis. In other words, the optical vortex can capture light from the microbody in the medium and control the movement of the microbody.

[0004] Depending on the performance of the optical components in the optical system from the light source to the micro-body or the adjustment accuracy when constructing the optical system, the optical vortex irradiated to the micro-body is sometimes not the desired optical vortex, and the movement of the micro-body is sometimes not the desired movement. For example, even if the micro-body is intended to move on a perfect circular track at a certain speed, depending on the performance of the optical components or the adjustment accuracy when constructing the optical system, the trajectory of the movement of the micro-body is sometimes elliptical or the speed varies.

[0005] Non-patent documents 1 to 5 describe a technique for achieving high-precision light capture by estimating the aberration of an optical system based on intensity information of an optical vortex and performing aberration correction based on the estimation result. In the techniques described in non-patent documents 4 and 5, a machine learns the relationship between the aberration correction amount and the intensity information, and obtains the aberration correction amount based on the intensity information.

[0006] In the technique described in Non-Patent Document 6, a modulation pattern presented to the modulation surface of a spatial light modulator is imaged onto a sample surface, and light is trapped on a microbody on the sample surface to move it. The modulation pattern is then adjusted based on the intensity information of the optical vortex and the movement information of the microbody.

[0007] Specifically, a phase grating pattern is added based on the intensity information of the optical vortex with respect to the modulation pattern presented to the modulation surface of the spatial light modulator, so that the light amplitude distribution on the sample surface becomes the desired light amplitude distribution. Furthermore, the phase distribution is adjusted based on the motion information of the micro-body (specifically, the angular velocity distribution) with respect to the modulation pattern presented to the modulation surface of the spatial light modulator, so that the motion of the micro-body becomes the desired motion (specifically, the orbital angular momentum density distribution (OAM-density) is made uniform).

[0008] Prior art literature

[0009] Non-patent literature

[0010] Non-patent document 1: SNKhonina, et al., "Strengthening the longitudinal component of the sharply focused electric field by means of higher-orderlaser beams", Optics Letters, Vol. 38, No. 17, pp. 3223-3226, 2013

[0011] Non-patent document 2: Y. Iketaki, et al., "Investigation of the center intensity of first-and second-order Laguerre-Gaussian beams with linear and circular polarization", Optics Letters, Vol. 32, No. 16, pp. 2357-2359, 2007

[0012] Non-patent document 3: Yansheng Liang, et al., "Aberration correction inholographic optical tweezers using a high-order optical vortex", AppliedOptics, Vol.57, No.13, pp.3618-3623, 2018

[0013] Non-patent document 4: Benjamin P.Cumming, et al., "Direct determination of aberration functions in microscopy by an artificial neural network", OpticsExpress, Vol.28, No.10, pp.14511-14521, 2020

[0014] Non-patent literature 5: Jin Li, et al., "Study on Aberration Correction of Adaptive Optics Based on Convolutional Neural Network", Photonics, Vol. 8, 377, pp. 1-9, 2021

[0015] Non-patent document 6: Mingzhou Chen, et al., "Dynamics of microparticles trapped in a perfect vortex beam", Optics Letters, Vol. 38, No. 22, pp. 4919-4922, 2013 Summary of the invention

[0016] Problems to be solved by the invention

[0017] The techniques described in non-patent documents 1 to 5 require high-precision optical devices or complex post-processing to obtain the intensity information of the optical vortex generated by the high-NA objective lens, which is not easy. The technique described in non-patent document 6 has the same problems as the techniques described in non-patent documents 1 to 5, and the technique is also not easy in that the modulation pattern presented by the modulation surface of the spatial light modulator is adjusted in two stages.

[0018] An object of the embodiments is to provide an optical vortex control device and an optical vortex control method that can easily generate a desired optical vortex.

[0019] Technical means of solving problems

[0020] The embodiment is an optical vortex control device. The optical vortex control device comprises: a light source that outputs light; an optical vortex generating unit that generates an optical vortex from the light; a focusing optical system that focuses the optical vortex; an imaging unit that captures a micro-body moving due to the optical vortex light focused by the focusing optical system and outputs image data; and a control unit that analyzes the movement of the micro-body based on the image data and adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

[0021] The embodiment is an optical vortex control method. The optical vortex control method uses a light source that outputs light, an optical vortex generating unit that generates an optical vortex from the light, and a focusing optical system that focuses the optical vortex, and comprises: an imaging step, using the imaging unit to capture a micro-body that moves due to the optical vortex light focused by the focusing optical system, and outputting image data; a control step, which analyzes the movement of the micro-body based on the image data, and adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

[0022] Effects of the Invention

[0023] According to the optical vortex control device and the optical vortex control method of the embodiment, a desired optical vortex can be easily generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 2 is a diagram showing the structure of the optical vortex control device 1 .

[0025] Figure 2 This is a diagram for explaining light trapping of the microbody 91 by the optical vortex.

[0026] Figure 3 This is a diagram for explaining light trapping of the microbody 91 by the optical vortex.

[0027] Figure 4 (a) and (b) are diagrams showing an example of the intensity distribution of the optical vortex at the sample position.

[0028] Figure 5 (a) is a diagram showing the motion trajectory of the micro-body before the adjustment optical vortex generation when objective lens A is used, and (b) is a diagram showing the motion trajectory of the micro-body after the adjustment optical vortex generation when objective lens A is used.

[0029] Figure 6 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens A is used.

[0030] Figure 7 (a) is a diagram showing the motion trajectory of the microbody before the adjustment optical vortex generation when objective lens B is used, and (b) is a diagram showing the motion trajectory of the microbody after the adjustment optical vortex generation when objective lens B is used.

[0031] Figure 8 Graphs showing torque distributions of the microbodies before and after the adjustment of optical vortex generation when the objective lens B is used.

[0032] Fig. 9(a) is a diagram showing the motion trajectory of the micro-body before the adjustment optical vortex generation when the objective lens C is used, and (b) is a diagram showing the motion trajectory of the micro-body after the adjustment optical vortex generation when the objective lens C is used.

[0033] Fig.10 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens C is used.

[0034] Fig.11 (a) is a diagram showing the motion trajectory of the microbody before the adjustment of the optical vortex generation when the objective lens D is used, and (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens D is used.

[0035] Fig.12 Graphs showing torque distributions of the microbodies before and after the adjustment of optical vortex generation when the objective lens D is used.

[0036] Fig.13 (a) is a diagram showing the motion trajectory of the micro-body before the adjustment optical vortex generation when the objective lens E is used, and (b) is a diagram showing the motion trajectory of the micro-body after the adjustment optical vortex generation when the objective lens E is used.

[0037] Fig.14 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens E is used.

[0038] Fig.15 FIG. 1 is a diagram showing an example of an adjustment pattern for adjusting the generation of an optical vortex.

[0039] Fig.16 This is a table summarizing the variance values ​​of the ellipticity and torque distribution before and after the adjustment of the optical vortex generation when the objective lenses A to E are used. DETAILED DESCRIPTION

[0040] Below, with reference to the accompanying drawings, the embodiments of the optical vortex control device and the optical vortex control method are described in detail. In addition, the same elements are marked with the same symbols in the description of the accompanying drawings, and repeated descriptions are omitted. The present invention is not limited to these examples, and is intended to include all changes within the meaning and scope represented by the claims and equivalent to the claims.

[0041] Figure 11 is a diagram showing the structure of the optical vortex control device 1. The optical vortex control device 1 is a device for controlling the movement of micro-bodies in a medium in a sample 90, and includes a light source 10, an optical vortex generating unit 20, lenses 30 to 33, an aperture 34, a dichroic mirror 40, an illumination unit 50, an imaging unit 60, and a control unit 70.

[0042] The medium in the sample 90 is a liquid or a gas. The shape of the micro-body in the medium is arbitrary, and may be, for example, a sphere, a cube, a cone, etc. The material of the micro-body is also arbitrary, and may be, for example, polystyrene beads, glass, crystal, etc. The micro-body has a size and weight that can be captured by the optical vortex light in the medium.

[0043] The light source 10 outputs light. The light source 10 is preferably a laser light source that generates coherent light. The light output from the light source 10 is preferably a wavelength with low thermal absorption by the medium in the sample 90.

[0044] The optical vortex generating unit 20 is optically connected to the light source 10. The optical vortex generating unit 20 inputs the light output from the light source 10, and generates and outputs an optical vortex. The optical vortex generated by the optical vortex generating unit 20 is a light beam having a spiral wave surface, such as a Laguerre-Gaussian beam or a Bessel beam. As the optical vortex generating unit 20, a diffractive optical element or a spatial light modulator is preferably used.

[0045] The spatial light modulator has a plurality of pixels arranged in two dimensions, and can modulate at least the phase of light in each pixel and output it. The spatial light modulator can also be a spatial light modulator that can modulate the amplitude of light in each pixel. If such a spatial light modulator is used as the optical vortex generating unit 20, it is possible to easily generate optical vortices of various forms according to the set modulation pattern without changing the optical system, and it is possible to perform various evaluations on the state of light capture of the micro-body.

[0046] The spatial light modulator used as the optical vortex generating unit 20 may be a transmission type or a reflection type. In the latter case, it may be a LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator). Figure 1 In FIG. 1 , a reflective spatial light modulator is shown as the optical vortex generating unit 20. Figure 1 In the embodiment, the light output from the light source 10 is incident on the optical vortex generating portion 20 at an angle, but the light may be incident on the optical vortex generating portion 20 at an angle closer to vertical.

[0047] The lens 31 , the aperture 34 , the lens 32 , the dichroic mirror 40 , and the objective lens 30 constitute a focusing optical system that guides the optical vortex output from the optical vortex generating unit 20 to the microbody in the medium in the sample 90 .

[0048] The rear focal position of the lens 31 and the front focal position of the lens 32 are consistent with each other. The aperture 34 has an opening at the rear focal position of the lens 31. The lenses 31 and 32 make the modulation surface of the optical vortex generating unit 20 and the pupil plane of the objective lens 30 have a mutually conjugate positional relationship, and make the image of the optical vortex output from the optical vortex generating unit 20 imaged near the pupil plane of the objective lens 30.

[0049] The dichroic mirror 40 reflects the light reaching from the lens 32 toward the objective lens 30. The objective lens 30 focuses the optical vortex on the micro-body in the medium in the sample 90 to capture the light. It is also possible to arrange a λ / 4 plate or a λ / 2 plate on the optical path of the optical vortex before it enters the objective lens 30 to control the rotation shape (circle, ellipse) of the micro-body.

[0050] The illumination unit 50 is provided on the opposite side of the objective lens 30 across the sample 90, and outputs illumination light to the sample 90. The illumination unit 50 preferably outputs light of a wavelength different from the wavelength of the light output from the light source 10. As the illumination unit 50, a white light source, a mercury lamp, a laser light source, or the like is used.

[0051] The imaging unit 60 captures the micro-body moving by light capture and illuminated by the illumination unit 50 via the objective lens 30, the dichroic mirror 40 and the lens 33, and outputs image data. A CCD camera, a CMOS camera or the like is used as the imaging unit 60. The dichroic mirror 40 transmits light from the sample 90 illuminated by the illumination unit 50.

[0052] The control unit 70 analyzes the motion of the microbody based on the image data output from the imaging unit 60. Based on the analysis result, the control unit 70 adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit 20 and controls the motion of the microbody. As the control unit 70, a computer or the like is used.

[0053] The control unit 70 includes: a processing unit, which includes a CPU or FPGA, etc., which performs analysis of the movement of the micro-body or adjustment of the optical vortex generation; a display unit, such as a liquid crystal display, which displays the movement of the micro-body photographed by the camera unit 60 or a modulation pattern for optical vortex generation or an adjustment pattern for adjustment; an input unit, such as a keyboard or a mouse, which receives adjustment conditions for optical vortex generation or an instruction to start adjustment; and a storage unit, which includes a hard disk drive or RAM, etc., which stores programs or various data processed by the processing unit.

[0054] Figure 2 and Figure 3 This is a diagram for explaining light trapping of the microbody 91 by the optical vortex. Figure 2 The diagram shows a view observed in a direction perpendicular to the propagation axis of the optical vortex L. Figure 3The figure shows the observation along the propagation axis direction of the optical vortex L, and the shadow line shows the annular area with high light intensity of the optical vortex L. If the optical vortex L is focused and irradiated on the sample 90, the optical vortex L can capture light from the micro-body 91 in the medium 92 in the sample 90, and can rotate the micro-body 91 around the propagation axis. The rotational motion of the micro-body 91 is, for example, circular motion or elliptical motion.

[0055] Figure 4 (a) and (b) are diagrams showing an example of the intensity distribution of the optical vortex at the sample position. The diagram shows the light intensity on the plane perpendicular to the propagation axis in shades, and the closer to white, the greater the light intensity.

[0056] As shown in the figure, the optical vortex has a ring-shaped light intensity distribution in which the light intensity is maximum at a certain distance in the radial direction from the propagation axis. Figure 4 Both of the light intensity distributions (a) and (b) are intended to generate a perfect circular light intensity distribution in which the light intensity is maximum at a certain distance radially from the propagation axis, thereby causing the light-trapping micro-body to move on a perfect circular orbit.

[0057] However, with Figure 4 Compared with the light intensity distribution shown in (b), Figure 4 The circularity of the light intensity distribution shown in (a) is low, and as a result, the motion trajectory of the light-trapped micro-body is greatly different from a perfect circle. It is believed that the reason why the light intensity distribution is different from the desired light intensity distribution is due to the aberration of the optical system caused by the limited performance of the optical components constituting the optical system of the optical vortex control device or the limited adjustment accuracy when constructing the optical system.

[0058] In this embodiment, the aberration of the optical system is corrected based on the motion information of the micro-body trapped by light, so that the light intensity distribution at the sample position is close to the desired light intensity distribution. The optical vortex control method of this embodiment includes an imaging step and a control step.

[0059] In the imaging step, the micro-body moving due to light capture is imaged by the imaging unit 60 and image data is output. In the control step, the motion of the micro-body is analyzed based on the image data, and the phase distribution of the optical vortex generated by the optical vortex generating unit 20 is adjusted based on the analysis result.

[0060] In addition, the optical vortex generating unit 20 may include one spatial light modulator, or may include two spatial light modulators optically connected in series. In the case where the optical vortex generating unit 20 includes one spatial light modulator, it is sufficient to overlap the adjustment pattern (phase distribution) for adjusting the optical vortex generation obtained based on the analysis result of the motion of the micro-body with the modulation pattern for the optical vortex generation before the adjustment, and to indicate the overlapped modulation pattern to one spatial light modulator.

[0061] In addition, when the optical vortex generating unit 20 includes two spatial light modulators, it is sufficient to prompt one spatial light modulator with the modulation pattern for optical vortex generation before adjustment, and prompt the other spatial light modulator with the adjustment pattern (phase distribution) for adjusting optical vortex generation obtained based on the analysis results of the movement of the microbody.

[0062] In the control step, the control unit 70 preferably analyzes any one of the motion trajectory, position distribution, and torque distribution of the micro-body as the motion of the micro-body. In addition, as the motion of the micro-body, the sum of the squares of the difference between the motion trajectory of the micro-body and the desired trajectory can also be analyzed, and any parameter related to the motion can be analyzed.

[0063] In addition, in the control step, the control unit 70 preferably analyzes any one of the velocity distribution and angular velocity of the micro-body as the motion of the micro-body. In addition, in the control step, the control unit 70 preferably analyzes any one of the velocity distribution and angular velocity of the micro-body as the motion of the micro-body based on a function with any one of the motion trajectory, position distribution, velocity distribution, angular velocity and torque distribution of the micro-body as a variable.

[0064] In the analysis of the motion trajectory of the micro-body, for example, the motion trajectory of the micro-body obtained based on the image data is approximated by an ellipse, and the ratio of the short axis to the long axis of the ellipse, i.e., the ellipticity, is calculated. In the analysis of the position distribution of the micro-body, for example, the position distribution of the micro-body in the circumferential direction around the propagation axis is calculated by dividing the circumferential direction around the propagation axis into a plurality of intervals at a certain angle and calculating which interval of the plurality of intervals the micro-body is present in in each frame of the image data.

[0065] In addition, in the analysis of the torque distribution of the microbody, for example, the torque distribution of the microbody in the circumferential direction around the propagation axis is obtained by dividing the circumferential direction around the propagation axis into a plurality of intervals at a certain angle and obtaining the torque of the microbody in each of the plurality of intervals based on image data.

[0066] When a micro-body rotates, there is a relationship represented by the following equation (1) between the average angular velocity ω, torque N, and viscous drag coefficient Γ. The viscous drag coefficient Γ is determined from the statistical variance of the angular velocity according to the Fluctuation Dissipation Theorem of Brownian motion.

[0067] [Number 1]

[0068] N=Γω (1)

[0069] The statistical set {ω of angular velocity information given to a micro-body representing Brownian motion in a circular orbit under a certain torque i}(i=1, 2…M), the fluctuation dissipation theorem is expressed by the following equations (2) and (3). T is the absolute temperature, k B is the Boltzmann constant, and Δω is the variance of the angular velocity. In addition, a correction can be made to calculate the correct angular velocity variance based on experimental data.

[0070] [Number 2]

[0071]

[0072] [Number 3]

[0073]

[0074] The imaging unit 60 acquires image data at a constant frame rate using a plurality of pixels arranged two-dimensionally on an imaging plane that receives light from the micro-body. Since the motion information of the micro-body is acquired based on the image data, the exposure time of each frame and the motion of the micro-body preferably have the following relationship.

[0075] The center of gravity of the micro-body is calculated by performing a gravity calculation on the image of the micro-body in each frame of the image. However, if the exposure time of each frame is too long, the movement distance of the micro-body during the exposure becomes longer, and the image of the micro-body stretches along the movement direction, so it is difficult to accurately calculate the center of gravity of the micro-body.

[0076] Therefore, in order to accurately determine the center of gravity position of the micro-body, it is preferred to make the moving distance of the micro-body within the exposure time smaller than the size of the image of the micro-body on the image of each frame. Through the center of gravity calculation, the position information of the micro-body is obtained with an accuracy below the diffraction limit. In addition, the moving distance of the micro-body within the exposure time depends on the optical vortex light amount.

[0077] In addition, the velocity vector of the micro-body can be obtained based on the center of gravity position of the micro-body in the image of the frame at a certain time t1 and the frame at the next time t2, and the velocity vector distribution of the micro-body in the circumferential direction can be obtained. However, if the difference between time t1 and time t2 is too large, it is difficult to distinguish the direction of rotation of the micro-body (whether it is right turn or left turn).

[0078] Therefore, in order to be able to distinguish the direction of rotation of the microbody, the product of the average angular velocity of the rotational motion of the microbody and the exposure time of each frame is preferably smaller than 180°.

[0079] In the control step, the control unit 70 uses any one or more of the analysis results. When one analysis result is used, the optical vortex generation performed by the optical vortex generation unit 20 is adjusted so that the evaluation value based on the analysis result becomes the minimum. In addition, when multiple analysis results are used, for example, the linear sum of the evaluation values ​​based on the respective analysis results is set as an evaluation function, and the optical vortex generation performed by the optical vortex generation unit 20 is adjusted so that the value of the evaluation function becomes the minimum.

[0080] For example, when it is desired to make a micro-body move on a perfect circular orbit at a certain speed, an ellipticity evaluation value A indicating how much the motion orbit of the micro-body deviates from the perfect circle is obtained based on the ellipticity, and a variance evaluation value B indicating the degree of variation in the speed of the motion of the micro-body is obtained based on the variance value of the position distribution or torque distribution of the micro-body. In addition, an evaluation function represented by a formula of αA+βB is obtained using coefficients α and β. Then, the optical vortex generation performed by the optical vortex generation unit 20 is adjusted so that the value of the evaluation function becomes the minimum.

[0081] In the control step, when the control unit 70 obtains an adjustment pattern for adjusting the optical vortex generation by the optical vortex generating unit 20 based on the analysis result, it is preferred that the adjustment pattern be expressed using Zernike polynomials or that the adjustment pattern be obtained using an optimization method.

[0082] Zernike polynomials are orthogonal polynomials defined on the unit circle, and are represented by two exponents (non-negative integer n, integer m) and two variables (radius vector ρ, deflection angle φ). In particular, in the field of optics, Zernike polynomials are used when analyzing axially symmetric optical aberrations based on diffraction theory. In addition, Zernike polynomials can also be used to represent aberration correction patterns.

[0083] As the optimization method, for example, an annealing method, a genetic algorithm, a blind search, etc. When the aberration correction amount is represented by a linear sum of a plurality of aberration components, the coefficient of each aberration component can be obtained using an optimization method.

[0084] In the control step, the control unit 70 overlaps the adjustment pattern for adjusting the generation of the optical vortex obtained based on the analysis result of the motion of the micro-body with the modulation pattern for the generation of the optical vortex before the adjustment, and prompts the optical vortex generator 20 with the modulation pattern after the overlap. Thus, the control unit 70 can adjust the generation of the optical vortex by the optical vortex generator 20 and control the motion of the micro-body. The adjustment pattern may also be a pattern including both the amplitude distribution and the phase distribution, but can be a pattern including only the phase distribution.

[0085] Next, examples are described. In the examples, Figure 1In the structure of the optical vortex control device 1 shown, the motion trajectory and torque distribution of the micro-body are obtained before and after the adjustment of the optical vortex generation for each of the five objective lenses A to E used as the objective lens 30 .

[0086] The optical system of the optical vortex control device 1 is constructed using the same four objective lenses B to E among the five objective lenses A to E, but the optical system of the optical vortex control device 1 is constructed using another objective lens A. In addition, the four objective lenses A to D among the five objective lenses A to E have the same specifications, but the other objective lens E has a different specification.

[0087] The four objectives A to D are plan semi-apochromatic objectives that have corrected chromatic aberration and field curvature aberration, and have high transmittance in a wide band from the ultraviolet region to the near-infrared region. Plan semi-apochromatic objectives are higher specifications than achromatic objectives and are suitable for optical vortex generation. Objective E is an achromatic objective that corrects chromatic aberration in the visible region and is the most common objective. Achromatic objectives are not suitable for photography because the periphery will be blurred if the center of the field of view is focused.

[0088] A spatial light modulator is used as the optical vortex generating unit 20, and the displayed hologram is designed by the Kirk-Jones method. The design parameters are set to the deflection index 2, the radial index 0, and the beam size radius 2.00 mm. The radius of the optical vortex generated on the pupil plane of the objective lens is preferably 20% or more relative to the radius of the pupil plane.

[0089] In the sample 90 of this embodiment, polystyrene beads with a diameter of 0.40 μm are used as microbodies 91, and pure water is used as medium 92. A ring-shaped spacer is sandwiched between two glass plates, and the microbodies and the medium are contained in the space formed by them. Then, the optical vortex focused by the objective lens is used to capture light of the microbodies (polystyrene beads) suspended in the medium (pure water).

[0090] With the goal of making the micro-body move on a perfect circular orbit at a constant speed, the optical vortex generation performed by the optical vortex generation unit 20 is adjusted so that the value of the evaluation function represented by the linear sum of the ellipticity evaluation value A and the variance evaluation value B becomes the minimum. Before and after adjusting the optical vortex generation, the center of gravity position of the micro-body in each frame of the image data is plotted as a point on the xy plane, and the motion trajectory of the micro-body is approximated by an ellipse, and the ratio of the short diameter to the long diameter of the ellipse, that is, the ellipticity, is calculated. The ellipticity evaluation value A is calculated based on the ellipticity.

[0091] In addition, the torque distribution of the micro-body in the circumferential direction around the propagation axis is obtained by dividing the circumferential direction around the propagation axis into 72 intervals at a certain angle of 5° before and after adjusting the generation of the optical vortex, and obtaining the torque of the micro-body in each interval based on the image data. The variance evaluation value B is obtained based on the variance value of the torque distribution.

[0092] Figure 5 (a) is a diagram showing the motion trajectory of the microbody before the adjustment optical vortex generation when objective lens A is used. Figure 5 (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens A is used. Figure 6 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens A is used.

[0093] Figure 7 (a) is a diagram showing the motion trajectory of the microbody before the adjustment optical vortex generation when objective lens B is used. Figure 7 (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens B is used. Figure 8 Graphs showing torque distributions of the microbodies before and after the adjustment of optical vortex generation when the objective lens B is used.

[0094] Fig. 9 (a) is a diagram showing the motion trajectory of the microbody before the adjustment optical vortex generation when the objective lens C is used. Fig. 9 (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens C is used. Fig.10 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens C is used.

[0095] Fig.11 (a) is a diagram showing the motion trajectory of the microbody before the adjustment of the optical vortex generation when the objective lens D is used. Fig.11 (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens D is used. Fig.12 Graphs showing torque distributions of the microbodies before and after the adjustment of optical vortex generation when the objective lens D is used.

[0096] Fig.13 (a) is a diagram showing the motion trajectory of the microbody before the adjustment optical vortex is generated when the objective lens E is used. Fig.13 (b) is a diagram showing the motion trajectory of the microbody after the adjustment of the optical vortex generation when the objective lens E is used. Fig.14 Graphs showing torque distributions of the microbodies before and after the adjustment of the optical vortex generation when the objective lens E is used.

[0097] Figure 5 (a) Figure 5 (b) Figure 7 (a) Figure 7(b) Fig. 9 (a) Fig. 9 (b) Fig.11 (a) Fig.11 (b) Fig.13 (a) and Fig.13 (b) The center of gravity positions of the micro-bodies in each frame of the image data are plotted as dots on the xy plane, and the density of the dots is represented by light and dark. Figure 6 , Figure 8 , Fig.10 , Fig.12 and Fig.14 These are graphs with the angular position in the circumferential direction around the propagation axis as the horizontal axis and the torque as the vertical axis.

[0098] Fig.15 : is a diagram showing an example of an adjustment pattern for adjusting the generation of an optical vortex. The adjustment pattern is a phase distribution represented by a Zernike polynomial.

[0099] Fig.16 This is a table summarizing the variance values ​​of the ellipticity and torque distribution before and after the adjustment of the optical vortex generation when using objective lenses A to E respectively. As shown in the results of the embodiment, compared with before the adjustment of the optical vortex generation, after the adjustment of the optical vortex generation, the ellipticity can be made close to 1, and the motion trajectory of the micro-body can be made close to a perfect circle. In addition, compared with before the adjustment of the optical vortex generation, after the adjustment of the optical vortex generation, the variance value of the torque distribution of the micro-body in the circumferential direction around the propagation axis can be reduced, and the speed of the movement of the micro-body can be made close to a certain value.

[0100] According to the present embodiment, an optical vortex capable of bringing the motion of a light-trapping microbody close to a desired motion can be easily generated and adjusted regardless of the performance of optical components constituting the optical system or the adjustment accuracy when constructing the optical system.

[0101] In the techniques described in non-patent documents 1 to 6, since a high-precision optical device or complicated post-processing is required to obtain the intensity information of the optical vortex, it is not easy to adjust the generation of the optical vortex. In contrast, in the present embodiment, since it is not necessary to obtain the intensity information of the optical vortex, it is easy to adjust the generation of the optical vortex.

[0102] In the technology described in non-patent document 6, since the adjustment of the modulation pattern presented by the spatial light modulator is divided into two stages, namely, amplitude distribution adjustment and phase distribution adjustment, it is not easy to adjust the generation of the optical vortex. In contrast, in the present embodiment, since only the phase distribution adjustment can be performed, the adjustment of the generation of the optical vortex is easy. In addition, in the present embodiment, since only the phase distribution adjustment can be performed, the loss of light can be suppressed, which is also preferred from this point of view.

[0103] The optical vortex control device and the optical vortex control method are not limited to the above-described embodiments and configuration examples, and various modifications are possible.

[0104] The optical vortex control device of the first mode of the above-mentioned implementation manner comprises: a light source, which outputs light; an optical vortex generating unit, which generates an optical vortex from the light; a focusing optical system, which focuses the optical vortex; a camera unit, which images a micro-body that moves due to the capture of the optical vortex light focused by the focusing optical system, and outputs image data; and a control unit, which analyzes the movement of the micro-body based on the image data, and adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

[0105] The optical vortex control device of the second aspect may have the structure of the first aspect, wherein the optical vortex generating unit includes a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating at least a phase of light in each pixel for output.

[0106] In the optical vortex control device of the third aspect, in addition to the configuration of the second aspect, the control unit may overlap an adjustment pattern for adjusting optical vortex generation with a modulation pattern for optical vortex generation, and present the overlapped modulation pattern to the spatial light modulator.

[0107] In the optical vortex control device according to a fourth aspect, in addition to the configuration of the third aspect, the control unit may obtain the adjustment pattern as the phase distribution.

[0108] In the optical vortex control device according to a fifth aspect, in addition to the configuration of the third or fourth aspect, the control unit may obtain the adjustment pattern using Zernike polynomials.

[0109] In the optical vortex control device according to a sixth aspect, in addition to the configuration of any one of the third to fifth aspects, the control unit may obtain the adjustment pattern using an optimization method.

[0110] In the optical vortex control device of a seventh aspect, in addition to the configuration of any one of the first to sixth aspects, the control unit may analyze any one of a motion trajectory, a position distribution, and a torque distribution of the micro-body as the motion of the micro-body.

[0111] In the optical vortex control device according to an eighth aspect, in addition to the configuration of any one of the first to sixth aspects, the control unit may analyze any one of a velocity distribution and an angular velocity of the micro-body as the motion of the micro-body.

[0112] The ninth mode of the optical vortex control device can be based on the structure of any one of the first to sixth modes, and can also be a control unit that analyzes the movement of the micro-body based on a function with any one of the motion trajectory, position distribution, velocity distribution, angular velocity and torque distribution of the micro-body as a variable.

[0113] The first mode of the optical vortex control method of the above-mentioned embodiment uses a light source that outputs light, an optical vortex generating unit that generates an optical vortex from the light, and a focusing optical system that focuses the optical vortex, and comprises: a camera step, using the camera unit to capture the micro-body that moves due to the optical vortex light focused by the focusing optical system, and output image data; a control step, based on the image data, analyzing the movement of the micro-body, and adjusting the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

[0114] The optical vortex control method of the second aspect may be configured in accordance with the first aspect, wherein the optical vortex generating unit includes a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating at least a phase of light in each pixel for output.

[0115] The optical vortex control method of the third aspect may be based on the structure of the second aspect, wherein in the control step, an adjustment pattern for adjusting the generation of the optical vortex is overlapped with a modulation pattern for the generation of the optical vortex, and the overlapped modulation pattern is presented to the spatial light modulator.

[0116] The optical vortex control method according to a fourth aspect may be configured according to the third aspect, wherein in the controlling step, an adjustment pattern is obtained as a phase distribution.

[0117] The optical vortex control method according to a fifth aspect may be configured according to the third or fourth aspect, wherein in the control step, the adjustment pattern is obtained using Zernike polynomials.

[0118] The optical vortex control method according to a sixth aspect may be configured as any one of the third to fifth aspects, wherein in the control step, an optimization method is used to obtain the adjustment pattern.

[0119] The optical vortex control method of the seventh aspect may be configured according to any one of the first to sixth aspects, wherein in the control step, any one of a motion trajectory, a position distribution, and a torque distribution of the micro-body is analyzed as the motion of the micro-body.

[0120] The optical vortex control method according to an eighth aspect may be configured as any one of the first to sixth aspects, wherein in the control step, any one of a velocity distribution and an angular velocity of the micro-body is analyzed as the motion of the micro-body.

[0121] The ninth mode of the optical vortex control method may be based on the structure of any one of the first to sixth modes, and may be such that, in the control step, the motion of the micro-body is analyzed based on a function with any one of the motion trajectory, position distribution, velocity distribution, angular velocity and torque distribution of the micro-body as a variable.

[0122] Industrial Applicability

[0123] The embodiments can be utilized as an optical vortex control device and an optical vortex control method that can easily generate a desired optical vortex.

[0124] Explanation of symbols

[0125] 1 ... optical vortex control device, 10 ... light source, 20 ... optical vortex generating unit, 30 to 33 ... lenses, 34 ... aperture, 40 ... dichroic mirror, 50 ... illumination unit, 60 ... imaging unit, 70 ... control unit, 90 ... sample, 91 ... microbody, 92 ... medium.

Claims

1. An optical vortex control device, wherein: have: a light source, which outputs light; an optical vortex generating unit for generating an optical vortex from the light; A focusing optical system for focusing the optical vortex; an imaging unit that captures the moving micro-body captured by the optical vortex light focused by the focusing optical system and outputs image data; as well as A control unit analyzes the motion of the microbody based on the image data, and adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

2. The optical vortex control device according to claim 1, wherein: The optical vortex generating unit includes a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating at least a phase of light in each pixel and outputting the modulated light.

3. The optical vortex control device according to claim 2, wherein: The control unit overlaps an adjustment pattern for adjusting the generation of an optical vortex with a modulation pattern for generating an optical vortex, and presents the overlapped modulation pattern to the spatial light modulator.

4. The optical vortex control device according to claim 3, wherein: The control unit obtains the adjustment pattern as a phase distribution.

5. The optical vortex control device according to claim 3 or 4, wherein: The control unit obtains the adjustment pattern using Zernike polynomials.

6. The optical vortex control device according to any one of claims 3 to 5, wherein: The control unit obtains the adjustment pattern using an optimization method.

7. The optical vortex control device according to any one of claims 1 to 6, wherein: The control unit analyzes any one of a motion trajectory, a position distribution, and a torque distribution of the microbody as the motion of the microbody.

8. The optical vortex control device according to any one of claims 1 to 6, wherein: The control unit analyzes either a velocity distribution or an angular velocity of the micro-body as the motion of the micro-body.

9. The optical vortex control device according to any one of claims 1 to 6, wherein: The control unit analyzes the motion of the micro-body based on a function having any one of a motion trajectory, position distribution, velocity distribution, angular velocity, and torque distribution of the micro-body as a variable.

10. An optical vortex control method, wherein: A light source for outputting light, an optical vortex generating unit for generating an optical vortex from the light, and a focusing optical system for focusing the optical vortex are used, and the light source includes: an imaging step of imaging the micro-body moving by being captured by the optical vortex light focused by the focusing optical system using an imaging unit, and outputting image data; as well as A control step of analyzing the motion of the microbody based on the image data and adjusting the phase distribution of the optical vortex generated by the optical vortex generating unit based on the analysis result.

11. The optical vortex control method according to claim 10, wherein: The optical vortex generating unit includes a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating at least a phase of light in each pixel and outputting the modulated light.

12. The optical vortex control method according to claim 11, wherein: In the control step, an adjustment pattern for adjusting the generation of an optical vortex is overlapped with a modulation pattern for generating an optical vortex, and the overlapped modulation pattern is presented to the spatial light modulator.

13. The optical vortex control method according to claim 12, wherein: In the control step, the adjustment pattern is obtained as a phase distribution.

14. The optical vortex control method according to claim 12 or 13, wherein: In the control step, the adjustment pattern is obtained using Zernike polynomials.

15. The optical vortex control method according to any one of claims 12 to 14, wherein: In the control step, the adjustment pattern is obtained using an optimization method.

16. The optical vortex control method according to any one of claims 10 to 15, wherein: In the control step, as the motion of the micro-body, any one of a motion trajectory, a position distribution, and a torque distribution of the micro-body is analyzed.

17. The optical vortex control method according to any one of claims 10 to 15, wherein: In the control step, as the motion of the micro-body, either a velocity distribution or an angular velocity of the micro-body is analyzed.

18. The optical vortex control method according to any one of claims 10 to 15, wherein: In the control step, the motion of the micro-body is analyzed based on a function having any one of a motion trajectory, position distribution, velocity distribution, angular velocity, and torque distribution of the micro-body as a variable.

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