Optical-vortex control device and optical-vortex control method

Abstract

An optical-vortex control device 1 controls the motion of a microbody in a medium in a sample 90 and includes a light source 10, an optical-vortex generation unit 20, lenses 30-33, an aperture 34, a dichroic mirror 40, a lighting unit 50, an imaging unit 60, and a control unit 70. The objective lens 30 condenses an optical vortex generated by the optical-vortex generation unit 20 and irradiates the microbody in the medium in the sample 90 with the condensed optical vortex to optically trap the microbody. The imaging unit 60 captures an image of the microbody optically trapped and in motion, and outputs image data thereof. The control unit 70 analyzes the motion of the microbody on the basis of the image data, and adjusts the phase distribution of the optical vortex generated by the optical-vortex generation unit 20 on the basis of the result of the analysis, thereby controlling the motion of the microbody. Accordingly, an optical-vortex control device that makes it possible to readily generate a desired optical vortex is realized.

Description

Optical vortex control device and optical vortex control method

[0001] The present disclosure relates to an optical vortex control device and an optical vortex control method.

[0002] A technique for optically trapping a microscopic object in a medium using an optical vortex is known. An optical vortex has a phase singularity on the propagation axis, and has a doughnut-shaped optical intensity distribution where the optical intensity is zero on the propagation axis and reaches a maximum at a certain distance from the propagation axis.

[0003] An optical vortex is characterized by its doughnut-shaped light intensity distribution and orbital angular momentum. When an optical vortex with orbital angular momentum is irradiated onto a minute object in a medium, the minute object receives angular momentum from the optical vortex and rotates along an orbit with high optical intensity around the propagation axis. In other words, the optical vortex can optically trap minute objects in the medium and control their motion.

[0004] Depending on the performance of the optical components in the optical system from the light source to the minute object and the adjustment accuracy during construction of the optical system, the optical vortex irradiated onto the minute object may not be the desired one, and the movement of the minute object may not be the desired one. For example, even if you want to move a minute object at a constant speed along a perfectly circular trajectory, depending on the performance of the optical components and the adjustment accuracy during construction of the optical system, the trajectory of the minute object's movement may become elliptical or the speed may fluctuate.

[0005] Non-Patent Documents 1 to 5 describe techniques for improving the accuracy of optical trapping by estimating the aberration of an optical system based on intensity information of an optical vortex and correcting the aberration based on this estimation result. The techniques described in Non-Patent Documents 4 and 5 use machine learning to learn the relationship between the amount of aberration correction and intensity information, and then calculate the amount of aberration correction from the intensity information.

[0006] In the technology described in Non-Patent Document 6, a modulation pattern presented on the modulation surface of a spatial light modulator is imaged onto a sample surface, and a minute object on the sample surface is optically trapped and moved. The modulation pattern is then adjusted based on the intensity information of the optical vortex and the motion information of the minute object.

[0007] Specifically, a phase grating pattern based on the intensity information of the optical vortex is added to the modulation pattern presented on the modulation surface of the spatial light modulator to achieve the desired optical amplitude distribution on the sample surface.Furthermore, the phase distribution is adjusted based on the motion information of the micro-particles (specifically, the angular velocity distribution) for the modulation pattern presented on the modulation surface of the spatial light modulator to achieve the desired motion of the micro-particles (specifically, to homogenize the orbital angular momentum density distribution (OAM-density)).

[0008] S. N. Khonina, et al., "Strengthening the longitudinal component of the sharply focused electric field by means of higher-order laser beams", Optics Letters, Vol.38, No.17, pp.3223-3226, 2013Y. 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, 2007Yansheng Liang, et al., "Aberration correction in holographic optical tweezers using a high-order optical vortex", Applied Optics, Vol.57, No.13, pp.3618-3623, 2018Benjamin P. Cumming, et al., "Direct determination of aberration functions in microscopy by an artificial neural network", Optics Express, Vol.28, No.10, pp.14511-14521, 2020Jin Li, et al., "Study on Aberration Correction of Adaptive Optics Based on Convolutional Neural Network", Photonics, Vol.8, 377, pp.1-9, 2021Mingzhou Chen, et al., "Dynamics of microparticles trapped in a perfect vortex beam", Optics Letters, Vol.38, No.22, pp.4919-4922, 2013.

[0009] The techniques described in Non-Patent Documents 1 to 5 require high-precision optical devices and complex post-processing to obtain intensity information of the optical vortex generated by a high-NA objective lens, which is not easy. The technique described in Non-Patent Document 6 has the same problems as those described in Non-Patent Documents 1 to 5, and is also not easy in that it requires adjusting the modulation pattern presented on the modulation surface of the spatial light modulator in two stages.

[0010] The embodiments aim to provide an optical vortex control device and an optical vortex control method that can easily generate a desired optical vortex.

[0011] An embodiment is an optical vortex control device that includes a light source that outputs light, an optical vortex generation unit that generates an optical vortex from the light, a focusing optical system that focuses the optical vortex, an imaging unit that images a moving microscopic object optically trapped by the optical vortex focused by the focusing optical system and outputs image data, and a control unit that analyzes the movement of the microscopic object based on the image data and adjusts the phase distribution of the optical vortex generated by the optical vortex generation unit based on the analysis results.

[0012] An embodiment is an optical vortex control method. The optical vortex control method includes an imaging step of using 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, capturing an image of a moving micro-object that is optically trapped by the optical vortex focused by the focusing optical system with an imaging unit and outputting image data, and a control step of analyzing the movement of the micro-object 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 results.

[0013] According to the optical vortex control device and optical vortex control method of the embodiment, a desired optical vortex can be easily generated.

[0014] FIG. 1 is a diagram illustrating the configuration of an optical vortex control device 1. FIG. 2 is a diagram illustrating the optical trapping of a micro-object 91 by an optical vortex. FIG. 3 is a diagram illustrating the optical trapping of a micro-object 91 by an optical vortex. FIG. 4 is a diagram illustrating an example of the intensity distribution of an optical vortex at a sample position (a) and (b). FIG. 5 is a diagram illustrating (a) the movement trajectory of a micro-object before optical vortex generation adjustment when objective lens A is used, and (b) the movement trajectory of a micro-object after optical vortex generation adjustment when objective lens A is used. FIG. 6 is a graph illustrating the torque distribution of a micro-object before and after optical vortex generation adjustment when objective lens A is used. FIG. 7 is a diagram illustrating (a) the movement trajectory of a micro-object before optical vortex generation adjustment when objective lens B is used, and (b) the movement trajectory of a micro-object after optical vortex generation adjustment when objective lens B is used. FIG. 8 is a graph illustrating the torque distribution of a micro-object before and after optical vortex generation adjustment when objective lens B is used. 9A shows the trajectory of the movement of the micro-body before the optical vortex generation adjustment when objective lens C is used, and (b) shows the trajectory of the movement of the micro-body after the optical vortex generation adjustment when objective lens C is used. FIG. 10 is a graph showing the torque distribution of the micro-body before and after the optical vortex generation adjustment when objective lens C is used. FIG. 11A shows the trajectory of the movement of the micro-body before the optical vortex generation adjustment when objective lens D is used, and (b) shows the trajectory of the movement of the micro-body after the optical vortex generation adjustment when objective lens D is used. FIG. 12 is a graph showing the torque distribution of the micro-body before and after the optical vortex generation adjustment when objective lens D is used. FIG. 13A shows the trajectory of the movement of the micro-body before the optical vortex generation adjustment when objective lens E is used, and (b) shows the trajectory of the movement of the micro-body after the optical vortex generation adjustment when objective lens E is used. FIG. 14 is a graph showing the torque distribution of the micro-body before and after the optical vortex generation adjustment when objective lens E is used. FIG. 15 is a diagram showing an example of an adjustment pattern for optical vortex generation adjustment. Figure 16 is a table summarizing the ellipticity and torque distribution variance values ​​before and after optical vortex generation adjustment when each of objective lenses A to E is used.

[0015] Hereinafter, with reference to the accompanying drawings, an embodiment of an optical vortex control device and an optical vortex control method will be described in detail. Note that in the description of the drawings, the same elements are given the same reference numerals and duplicate explanations will be omitted. The present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0016] 1 is a diagram showing the configuration of optical vortex control device 1. Optical vortex control device 1 is a device that controls the movement of minute objects in a medium in 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.

[0017] The medium in the sample 90 is a liquid or a gas. The shape of the particles in the medium may be any shape, such as a sphere, a cube, or a cone. The material of the particles may also be any material, such as polystyrene beads, glass, or quartz crystal. The particles have a size and weight that allows them to be optically trapped by the optical vortex in the medium.

[0018] The light source 10 outputs light, preferably a laser light source that produces coherent light, and the light output from the light source 10 is preferably at a wavelength that is subject to low thermal absorption by the medium in the sample 90.

[0019] Optical vortex generator 20 is optically connected to light source 10. Optical vortex generator 20 receives the light output from light source 10, generates an optical vortex, and outputs it. The optical vortex generated by optical vortex generator 20 is a light beam with a spiral wavefront, such as a Laguerre-Gauss beam or a Bessel beam. A diffractive optical element, a spatial light modulator, or the like is preferably used as optical vortex generator 20.

[0020] The spatial light modulator has a plurality of pixels arranged two-dimensionally and can modulate and output at least the phase of light at each pixel. The spatial light modulator may also be capable of modulating the amplitude of light at each pixel. By using such a spatial light modulator as the optical vortex generator 20, optical vortices of various shapes can be easily generated according to the set modulation pattern without changing the optical system, and various evaluations of the state of optical trapping of microscopic objects can be performed.

[0021] The spatial light modulator used as optical vortex generator 20 may be a transmissive or reflective type, and in the latter case may be an LCOS-SLM (Liquid Crystal on Silicon - Spatial Light Modulator). Figure 1 shows a reflective spatial light modulator as optical vortex generator 20. In Figure 1, the light output from light source 10 is obliquely incident on optical vortex generator 20, but the light may also be incident on optical vortex generator 20 at an angle closer to perpendicular.

[0022] Lens 31, aperture 34, lens 32, dichroic mirror 40 and objective lens 30 constitute a focusing optical system that guides the optical vortex output from optical vortex generating unit 20 to a microscopic object in the medium of sample 90.

[0023] The rear focal position of lens 31 and the front focal position of lens 32 coincide with each other. Aperture 34 has an opening at the rear focal position of lens 31. Lenses 31 and 32 are arranged so that the modulation plane of optical vortex generating unit 20 and the pupil plane of objective lens 30 are in a conjugate positional relationship with each other, and an image of the optical vortex output from optical vortex generating unit 20 is formed near the pupil plane of objective lens 30.

[0024] Dichroic mirror 40 reflects the light arriving from lens 32 to objective lens 30. Objective lens 30 focuses and irradiates the optical vortex onto minute objects in the medium of sample 90, optically trapping the objects. A λ / 4 plate or λ / 2 plate can be placed on the optical path of the optical vortex before it enters objective lens 30 to control the rotational shape (circle, ellipse) of the minute objects.

[0025] The illumination unit 50 is provided on the opposite side of the sample 90 from the objective lens 30, 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. The illumination unit 50 may be a white light source, a mercury lamp, a laser light source, or the like.

[0026] The imaging unit 60 images the moving, optically trapped micro-particles 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.

[0027] The control unit 70 analyzes the movement of the minute object based on the image data output from the imaging unit 60. Based on the analysis results, the control unit 70 adjusts the phase distribution of the optical vortex generated by the optical vortex generating unit 20 to control the movement of the minute object. A computer or the like is used as the control unit 70.

[0028] The control unit 70 includes a processing unit including, for example, a CPU or FPGA, which analyzes the movement of the micro-particles and adjusts the generation of the optical vortex, a display unit such as an LCD display which displays the movement of the micro-particles imaged by the imaging unit 60, modulation patterns for generating the optical vortex, and adjustment patterns for adjustment, an input unit such as a keyboard or mouse which accepts adjustment conditions for generating the optical vortex and instructions to start adjustment, and a memory unit including a hard disk drive or RAM which stores programs for processing performed by the processing unit and various data.

[0029] 2 and 3 are diagrams illustrating the optical trapping of a minute object 91 by an optical vortex. FIG. 2 shows a view perpendicular to the propagation axis of the optical vortex L. FIG. 3 shows a view along the propagation axis of the optical vortex L, with the doughnut-shaped area of ​​high optical intensity of the optical vortex L indicated by hatching. When the optical vortex L is focused and irradiated onto a sample 90, the optical vortex L can optically trap a minute object 91 in a medium 92 in the sample 90, causing the minute object 91 to rotate around the propagation axis. The rotational motion of the minute object 91 is, for example, a circular motion or an elliptical motion.

[0030] 4(a) and (b) show an example of the intensity distribution of an optical vortex at the sample position. This figure shows the light intensity on a plane perpendicular to the propagation axis as shades of gray, with whiter colors indicating higher light intensity.

[0031] As shown in this figure, the optical vortex has a doughnut-shaped light intensity distribution where the light intensity is maximized at a certain radial distance from the propagation axis. Both the light intensity distributions in Figures 4(a) and 4(b) are intended to generate a perfectly circular light intensity distribution where the light intensity is maximized at a certain radial distance from the propagation axis, thereby moving the optically trapped micro-object along a perfectly circular trajectory.

[0032] However, the light intensity distribution shown in Figure 4(a) has a lower circularity than the light intensity distribution shown in Figure 4(b), and as a result, the movement trajectory of the optically trapped micro-object differs significantly from a perfect circle. The reason the light intensity distribution differs from the desired one is thought to be due to aberrations in the optical system caused by limitations in the performance of the optical components that make up the optical system of the optical vortex control device and the adjustment precision during construction of the optical system.

[0033] In this embodiment, the optical vortex control method corrects the aberration of the optical system based on the motion information of the optically trapped micro-object, thereby bringing the light intensity distribution at the sample position closer to the desired one. The optical vortex control method of this embodiment includes an imaging step and a control step.

[0034] In the imaging step, the moving optically trapped micro-object is imaged by the imaging unit 60 and image data is output. In the control step, the movement of the micro-object 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 results.

[0035] The optical vortex generator 20 may include one spatial light modulator, or two spatial light modulators optically connected in series. When the optical vortex generator 20 includes one spatial light modulator, the adjustment pattern (phase distribution) for adjusting the optical vortex generation determined based on the analysis results of the movement of the micro-object is superimposed on the modulation pattern for generating the optical vortex before adjustment, and the superimposed modulation pattern is presented by one spatial light modulator.

[0036] Furthermore, if the optical vortex generating unit 20 includes two spatial light modulators, one spatial light modulator can be made to present a modulation pattern for generating the optical vortex before adjustment, and the other spatial light modulator can be made to present an adjustment pattern (phase distribution) for adjusting the generation of the optical vortex obtained based on the analysis results of the movement of the micro-object.

[0037] In the control step, the control unit 70 analyzes the motion of the micro-object, preferably any one of the motion trajectory, position distribution, and torque distribution of the micro-object. Alternatively, the control unit 70 may analyze the sum of squares of the difference between the motion trajectory of the micro-object and a desired trajectory, or any parameter related to the motion.

[0038] In the control step, the control unit 70 analyzes the motion of the minute object, preferably based on a function that uses as a variable any of the motion trajectory, position distribution, velocity distribution, angular velocity, and torque distribution of the minute object.

[0039] In analyzing the motion trajectories of minute objects, for example, the motion trajectories of minute objects obtained based on image data are approximated by an ellipse, and the ellipticity, which is the ratio of the minor axis to the major axis of the ellipse, is calculated. In analyzing the position distribution of minute objects, for example, the circumferential direction around the propagation axis is divided into multiple sections at fixed angles, and the position distribution of minute objects in the circumferential direction around the propagation axis is calculated by determining which of the multiple sections the minute objects are located in in each frame of image data.

[0040] In addition, when analyzing the torque distribution of a micro-body, for example, the circumferential direction around the propagation axis is divided into multiple sections at fixed angles, and the torque of the micro-body is calculated in each of the multiple sections based on image data, thereby calculating the torque distribution of the micro-body in the circumferential direction around the propagation axis.

[0041] When a minute object is in rotational motion, the relationship between the average angular velocity ω, torque N, and viscous resistance coefficient Γ is expressed by the following equation (1). The viscous resistance coefficient Γ is determined from the statistical variance of the angular velocity according to the Fluctuation Dissipation Theorem of Brownian motion.

[0042] Statistical set of angular velocity information {ω} of a minute object exhibiting Brownian motion in a circular orbit under a constant rotational force ｉ} (i = 1, 2, ..., M), the fluctuation-dissipation theorem is expressed by the following equations (2) and (3): T is the absolute temperature, and k Ｂ is the Boltzmann constant, and Δω is the variance of the angular velocity. Note that correction may be performed to calculate the correct angular velocity variance from experimental data.

[0043] The imaging unit 60 acquires image data at a constant frame rate using a plurality of pixels arranged two-dimensionally on an imaging surface that receives light from the minute object. Since information on the movement of the minute object is acquired based on this image data, it is preferable that the exposure time of each frame and the movement of the minute object have the following relationship:

[0044] The center of gravity of the particle is calculated by calculating the center of gravity of the image of the particle in each frame. However, if the exposure time of each frame is too long, the distance traveled by the particle during the exposure becomes long, and the image of the particle becomes elongated in the direction of movement, making it difficult to accurately determine the center of gravity of the particle.

[0045] Therefore, to accurately determine the center of gravity of a microscopic object, it is preferable that the distance the object moves during the exposure time on each frame image is smaller than the size of the object's image. By calculating the center of gravity, position information of the object can be obtained with an accuracy below the diffraction limit. The distance the object moves during the exposure time depends on the amount of light from the optical vortex.

[0046] Furthermore, the velocity vector of the minute object can be calculated based on the center of gravity position of the minute object in each image of a frame at a certain time t1 and a frame at the next time t2, and further, the velocity vector distribution of the minute object in the circumferential direction can be calculated. However, if the difference between time t1 and time t2 is too large, it becomes difficult to distinguish the rotation direction of the minute object (whether clockwise or counterclockwise).

[0047] Therefore, in order to be able to distinguish the rotation direction of the particles, it is preferable that the product of the average angular velocity of the rotational motion of the particles and the exposure time of each frame is smaller than 180°.

[0048] In the control step, the control unit 70 uses one or more of these analysis results. When using one analysis result, the control unit 70 adjusts the optical vortex generation by the optical vortex generating unit 20 so that the evaluation value based on that analysis result is minimized. When using multiple analysis results, the control unit 70 adjusts the optical vortex generation by the optical vortex generating unit 20 so that the evaluation function is minimized, for example, by using the linear sum of the evaluation values ​​based on each analysis result as the evaluation function.

[0049] For example, if one wishes to move a micro-object at a constant speed along a perfectly circular trajectory, an ellipticity evaluation value A, which indicates how much the trajectory of the micro-object deviates from a perfect circle, is calculated based on the ellipticity, and a variance evaluation value B, which indicates the degree of variation in the speed of the micro-object's movement, is calculated based on the variance of the position distribution or torque distribution of the micro-object. Furthermore, an evaluation function expressed by the formula αA + βB is calculated using coefficients α and β. The optical vortex generation by the optical vortex generating unit 20 is then adjusted so that the value of this evaluation function is minimized.

[0050] In the control step, when the control unit 70 determines an adjustment pattern for adjusting the optical vortex generation by the optical vortex generating unit 20 based on the analysis results, it is preferable for the control unit 70 to represent the adjustment pattern using Zernike polynomials, and it is also preferable for the control unit 70 to determine the adjustment pattern using an optimization method.

[0051] Zernike polynomials are orthogonal polynomials defined on a unit circle and are expressed by two exponents (a non-negative integer n and an integer m) and two variables (a radius vector ρ and a deviation angle φ). Zernike polynomials are used in the field of optics, in particular, to analytically treat axially symmetric optical aberrations based on diffraction theory. Zernike polynomials can also be used to represent aberration correction patterns.

[0052] Examples of the optimization method that can be used include simulated annealing, genetic algorithms, blind search, etc. When the amount of aberration correction is expressed as a linear sum of multiple aberration components, the coefficient of each aberration component can be found using the optimization method.

[0053] In the control step, the control unit 70 superimposes an adjustment pattern for adjusting the optical vortex generation, determined based on the analysis results of the movement of the micro-object, on the modulation pattern for generating the optical vortex before adjustment, and causes the optical vortex generator 20 to present the superimposed modulation pattern. This allows the control unit 70 to adjust the generation of the optical vortex by the optical vortex generator 20 to control the movement of the micro-object. The adjustment pattern may include both an amplitude distribution and a phase distribution, but may also include only a phase distribution.

[0054] Next, we will explain the examples. In the examples, the motion trajectories and torque distributions of the micro-objects were determined before and after optical vortex generation adjustment for each of the five objective lenses A to E used as objective lens 30 in the configuration of optical vortex control device 1 shown in Figure 1.

[0055] Of the five objective lenses A to E, the same person constructed the optical system of the optical vortex control device 1 using four objective lenses B to E, but another person constructed the optical system of the optical vortex control device 1 using the remaining objective lens A. Furthermore, of the five objective lenses A to E, four objective lenses A to D had the same specifications, but the remaining objective lens E had different specifications.

[0056] The four objective lenses A to D are plan semi-apochromatic objective lenses that correct chromatic aberration and field curvature aberration, and have high transmittance over a wide band from the ultraviolet to near-infrared range. Plan semi-apochromatic objective lenses have higher specifications than achromatic objective lenses, and are suitable for use in generating optical vortices. Objective lens E is an achromatic objective lens that corrects chromatic aberration in the visible range, and is the most common. Achromatic objective lenses are considered unsuitable for photography because the periphery becomes blurred when focused on the center of the field of view.

[0057] A spatial light modulator was used as the optical vortex generator 20, and the hologram to be displayed was designed using the Kirk-Jones method. The design parameters were a deviation index of 2, a radial index of 0, and a beam size radius of 2.00 mm. The radius of the optical vortex generated on the pupil plane of the objective lens is preferably 20% or more of the radius of the pupil plane.

[0058] In the sample 90 of this example, polystyrene beads with a diameter of 0.40 μm were used as the microparticles 91, and pure water was used as the medium 92. An annular spacer was sandwiched between two glass plates, and the microparticles and medium were placed in the space formed by these plates. The microparticles (polystyrene beads) suspended in the medium (pure water) were then optically trapped by an optical vortex focused by an objective lens.

[0059] With the goal of moving the micro-particle at a constant speed along a perfectly circular trajectory, the optical vortex generation by the optical vortex generator 20 was adjusted so that the value of the evaluation function expressed as the linear sum of the ellipticity evaluation value A and the variance evaluation value B was minimized. Before and after adjusting the optical vortex generation, the center of gravity of the micro-particle in each frame of the image data was plotted as a point on the xy plane, the motion trajectory of the micro-particle was approximated by an ellipse, and the ellipticity, which is the ratio of the minor axis to the major axis of the ellipse, was calculated. The ellipticity evaluation value A was calculated based on this ellipticity.

[0060] In addition, before and after the optical vortex generation adjustment, the circumferential direction around the propagation axis was divided into 72 sections at regular intervals of 5°, and the torque of the micro-objects in each section was calculated based on the image data to determine the torque distribution of the micro-objects in the circumferential direction around the propagation axis. The variance evaluation value B was calculated based on the variance of this torque distribution.

[0061] Figure 5(a) is a diagram showing the movement trajectory of a micro-body before optical vortex generation adjustment when objective lens A is used. Figure 5(b) is a diagram showing the movement trajectory of a micro-body after optical vortex generation adjustment when objective lens A is used. Figure 6 is a graph showing the torque distribution of a micro-body before and after optical vortex generation adjustment when objective lens A is used.

[0062] Figure 7(a) is a diagram showing the movement trajectory of a micro-body before optical vortex generation adjustment when objective lens B is used. Figure 7(b) is a diagram showing the movement trajectory of a micro-body after optical vortex generation adjustment when objective lens B is used. Figure 8 is a graph showing the torque distribution of a micro-body before and after optical vortex generation adjustment when objective lens B is used.

[0063] Figure 9(a) is a diagram showing the movement trajectory of a micro-body before optical vortex generation adjustment when objective lens C is used. Figure 9(b) is a diagram showing the movement trajectory of a micro-body after optical vortex generation adjustment when objective lens C is used. Figure 10 is a graph showing the torque distribution of a micro-body before and after optical vortex generation adjustment when objective lens C is used.

[0064] Figure 11(a) is a diagram showing the movement trajectory of a micro-object before optical vortex generation adjustment when objective lens D is used. Figure 11(b) is a diagram showing the movement trajectory of a micro-object after optical vortex generation adjustment when objective lens D is used. Figure 12 is a graph showing the torque distribution of a micro-object before and after optical vortex generation adjustment when objective lens D is used.

[0065] Figure 13(a) is a diagram showing the movement trajectory of a micro-body before optical vortex generation adjustment when objective lens E is used. Figure 13(b) is a diagram showing the movement trajectory of a micro-body after optical vortex generation adjustment when objective lens E is used. Figure 14 is a graph showing the torque distribution of a micro-body before and after optical vortex generation adjustment when objective lens E is used.

[0066] In Figures 5(a), 5(b), 7(a), 7(b), 9(a), 9(b), 11(a), 11(b), 13(a), and 13(b), the positions of the centers of gravity of the micro-particles in each frame of image data are plotted as points on the x-y plane, and the density of the points is indicated by the shade of gray. In Figures 6, 8, 10, 12, and 14, the horizontal axis represents the angular position in the circumferential direction around the propagation axis, and the vertical axis represents the torque.

[0067] 15 is a diagram showing an example of an adjustment pattern for adjusting the generation of an optical vortex. This adjustment pattern is a phase distribution expressed by Zernike polynomials.

[0068] Figure 16 is a table summarizing the ellipticity and torque distribution variance values ​​before and after optical vortex generation adjustment when using each of objective lenses A to E. As shown in the results of the examples, after optical vortex generation adjustment, the ellipticity was able to approach 1 compared to before optical vortex generation adjustment, and the motion trajectory of the micro-object was able to approach a perfect circle. Furthermore, after optical vortex generation adjustment, the variance value of the torque distribution of the micro-object in the circumferential direction around the propagation axis was able to be reduced compared to before optical vortex generation adjustment, and the speed of the micro-object's motion was able to approach a constant value.

[0069] According to this embodiment, it is possible to easily generate and adjust an optical vortex that can bring the movement of optically trapped micro-particles closer to the desired one, regardless of the performance of the optical components that make up the optical system or the adjustment accuracy when constructing the optical system.

[0070] The techniques described in Non-Patent Documents 1 to 6 require high-precision optical devices and complex post-processing to acquire optical vortex intensity information, making it difficult to adjust the generation of the optical vortex. In contrast, in this embodiment, there is no need to acquire optical vortex intensity information, making it easy to adjust the generation of the optical vortex.

[0071] In the technology described in Non-Patent Document 6, the modulation pattern presented to the spatial light modulator is adjusted in two stages: amplitude distribution adjustment and phase distribution adjustment, making it difficult to adjust the generation of an optical vortex. In contrast, in this embodiment, only phase distribution adjustment is required, making it easy to adjust the generation of an optical vortex. Furthermore, since only phase distribution adjustment is required in this embodiment, it is also preferable in that light loss can be suppressed.

[0072] The optical vortex control device and optical vortex control method are not limited to the above-described embodiments and configuration examples, and various modifications are possible.

[0073] The first aspect of the optical vortex control device according to the above embodiment comprises a light source that outputs light, an optical vortex generating unit that generates an optical vortex from this light, a focusing optical system that focuses the optical vortex, an imaging unit that images a moving micro-object that is optically trapped by the optical vortex focused by the focusing optical system and outputs image data, and a control unit that analyzes the movement of the micro-object 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 results.

[0074] In the second aspect of the optical vortex control device, in the configuration of the first aspect, the optical vortex generating unit may be configured to include a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating and outputting at least the phase of light at each pixel.

[0075] In the third aspect of the optical vortex control device, in the configuration of the second aspect, the control unit may be configured to superimpose an adjustment pattern for adjusting the generation of the optical vortex on a modulation pattern for generating the optical vortex, and present the superimposed modulation pattern to the spatial light modulator.

[0076] In the optical vortex control device of the fourth aspect, in the configuration of the third aspect, the control unit may be configured to obtain the adjustment pattern as a phase distribution.

[0077] In the optical vortex control device of the fifth aspect, in the configuration of the third or fourth aspect, the control unit may be configured to determine the adjustment pattern using Zernike polynomials.

[0078] In the optical vortex control device of the sixth aspect, in the configuration of any of the third to fifth aspects, the control unit may be configured to determine the adjustment pattern using an optimization method.

[0079] In the seventh aspect of the optical vortex control device, in any of the configurations of the first to sixth aspects, the control unit may be configured to analyze the movement of the micro-body by analyzing any of the movement trajectory, position distribution, and torque distribution of the micro-body.

[0080] In the eighth aspect of the optical vortex control device, in the configuration of any of the first to sixth aspects, the control unit may be configured to analyze either the velocity distribution or angular velocity of the micro-object as the movement of the micro-object.

[0081] In the ninth aspect of the optical vortex control device, in any of the configurations of the first to sixth aspects, the control unit may be configured to analyze the movement of the micro-body based on a function with any of the movement trajectory, position distribution, velocity distribution, angular velocity, and torque distribution of the micro-body as variables.

[0082] The first aspect of the optical vortex control method according to the above embodiment uses a light source that outputs light, an optical vortex generating unit that generates an optical vortex from this light, and a focusing optical system that focuses the optical vortex, and includes an imaging step in which an imaging unit captures an image of a moving micro-object that is optically trapped by the optical vortex focused by the focusing optical system and outputs image data, and a control step in which the movement of the micro-object is analyzed based on the image data and the phase distribution of the optical vortex generated by the optical vortex generating unit is adjusted based on the analysis results.

[0083] In the second aspect of the optical vortex control method, in the configuration of the first aspect, the optical vortex generating unit may be configured to include a spatial light modulator having a plurality of pixels arranged two-dimensionally and modulating and outputting at least the phase of light at each pixel.

[0084] In the third aspect of the optical vortex control method, in the configuration of the second aspect, in the control step, an adjustment pattern for adjusting the generation of the optical vortex may be superimposed on a modulation pattern for generating the optical vortex, and the superimposed modulation pattern may be presented to the spatial light modulator.

[0085] In the optical vortex control method of the fourth aspect, in the configuration of the third aspect, the control step may be configured to obtain the adjustment pattern as a phase distribution.

[0086] In the optical vortex control method of the fifth aspect, in the configuration of the third or fourth aspect, the control step may be configured to determine the adjustment pattern using Zernike polynomials.

[0087] In the optical vortex control method of the sixth aspect, in the configuration of any of the third to fifth aspects, the control step may be configured to use an optimization method to determine the adjustment pattern.

[0088] In the seventh aspect of the optical vortex control method, in the configuration of any of the first to sixth aspects, the control step may be configured to analyze the movement of the micro-body by analyzing any of the movement trajectory, position distribution, and torque distribution of the micro-body.

[0089] In the eighth aspect of the optical vortex control method, in any of the configurations of the first to sixth aspects, the control step may be configured to analyze either the velocity distribution or angular velocity of the micro-object as the movement of the micro-object.

[0090] In the ninth aspect of the optical vortex control method, in the configuration of any of the first to sixth aspects, the control step may be configured to analyze the movement of the micro-body based on a function whose variables are any of the movement trajectory, position distribution, velocity distribution, angular velocity, and torque distribution of the micro-body.

[0091] The embodiments can be used as an optical vortex control device and an optical vortex control method that can easily generate a desired optical vortex.

[0092] 1...optical vortex control device, 10...light source, 20...optical vortex generation unit, 30-33...lens, 34...aperture, 40...dichroic mirror, 50...illumination unit, 60...imaging unit, 70...control unit, 90...sample, 91...microscopic object, 92...medium.

Claims

1. 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 images a moving microscopic object optically trapped by the optical vortex focused by the focusing optical system and outputs image data; a control unit that analyzes the movement of the minute object 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; An optical vortex control device comprising:

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 and outputting at least the phase of light at each pixel.

3. The optical vortex control device described in claim 2, wherein the control unit superimposes an adjustment pattern for adjusting the generation of an optical vortex on a modulation pattern for generating an optical vortex, and causes the spatial light modulator to present the superimposed modulation pattern.

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

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

6. The optical vortex control device according to claim 3 , wherein the control unit determines 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 the movement of the micro-object by analyzing one of the movement trajectory, position distribution, and torque distribution of the micro-object.

8. The optical vortex control device according to any one of claims 1 to 6, wherein the control unit analyzes either the velocity distribution or angular velocity of the minute object as the movement of the minute object.

9. An optical vortex control device as described in any one of claims 1 to 6, wherein the control unit analyzes the movement of the micro-object based on a function having as variables any of the movement trajectory, position distribution, velocity distribution, angular velocity and torque distribution of the micro-object.

10. 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, an imaging step of imaging a moving microscopic object optically trapped by the optical vortex focused by the focusing optical system with an imaging unit and outputting image data; a control step of analyzing the movement of the minute object 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; An optical vortex control method comprising:

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 and outputting at least the phase of light at each pixel.

12. The optical vortex control method described in claim 11, wherein in the control step, an adjustment pattern for adjusting the generation of an optical vortex is superimposed on a modulation pattern for generating an optical vortex, and the superimposed modulation pattern is presented to the spatial light modulator.

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

14. The optical vortex control method according to claim 12, wherein the adjustment pattern is determined using Zernike polynomials in the control step.

15. The optical vortex control method according to claim 12, wherein the adjustment pattern is determined using an optimization method in the control step.

16. An optical vortex control method according to any one of claims 10 to 15, wherein in the control step, the movement of the micro-object is analyzed as any one of the movement trajectory, position distribution, and torque distribution of the micro-object.

17. An optical vortex control method according to any one of claims 10 to 15, wherein in the control step, the movement of the micro-object is analyzed as either the velocity distribution or angular velocity of the micro-object.

18. An optical vortex control method according to any one of claims 10 to 15, wherein in the control step, the movement of the micro-object is analyzed based on a function having as variables any of the movement trajectory, position distribution, velocity distribution, angular velocity and torque distribution of the micro-object.