JP2006235319A - Device for controlling movement of particulate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling the movement of particulate, which realizes the movement of the condensed position of a laser beam by a control means having simple constitution, and which is made light in weight and small in size and advantageous economically. <P>SOLUTION: In the device where a beam from a laser beam source 711 is condensed by an objective 721 so as to capture an object at a focal position, a lens composed of a liquid crystal optical element 720 where the orientation control of liquid crystal molecules is performed by the application of external voltage to vary the effective refractive index distribution characteristic of liquid crystal is arranged between the laser beam source 711 and the objective 721. By varying the focal position of the incident laser beam, the position of the object is controlled. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fine particle movement control device, and particularly an apparatus that is effective for reducing the size and weight by reducing peripheral components.

  There are manipulators (also called optical tweezers) for moving fine observation objects such as fine particles and cells in a non-contact manner. In this manipulator, the object to be observed can be captured by irradiating the object to be observed with the focal point of the laser beam, and the object can be captured and moved by the light pressure.

  In this type of manipulator, it is necessary to control the movement of the focus of the laser beam in order to move the observation object to an arbitrary position. Conventionally, it has been realized by mechanical means as means for controlling the movement of the focus of the laser beam. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2003-175497), an additional lens system that can move on the optical axis is disposed on the optical axis between the laser light source and the condenser lens. Then, the additional lens system is moved on the optical axis, the spherical aberration is controlled, and the focal position is adjusted. In some cases, the observation object is irradiated with an optical fiber through an optical fiber to be captured, and the movement of the observation object mechanically fine-tunes the tip of the optical fiber (for example, JP 09-043434 A).

  The above-described conventional particle movement control device is a method of mechanically controlling using an optical component (such as a lens or a mirror) in order to control the position of the particle by moving the focal position of the laser beam.

  For this reason, peripheral components are large, and are not suitable for reduction in size and weight. In addition, since the mechanical control device is required to have high accuracy, the price is also expensive.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fine particle movement control device that can realize the focal position of laser light with a control means having a simple configuration, can be reduced in weight and size, and is economically advantageous. There is.

  In order to solve the above-mentioned problem, the present invention provides an apparatus for condensing a beam from a laser light source with an objective lens and capturing an object near the focal point. The lens is made of a liquid crystal optical element that can change the effective refractive index distribution characteristics of the liquid crystal, and the position of the object can be controlled by changing the focal position of the incident laser light. To do.

  By the above means, a mechanical drive mechanism is not required for laser beam position control, and a light and small particle movement control device can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration example of a particulate movement control device according to the present invention. A stand 702 is erected and attached to the end of the base 701. A support body 703 is disposed at an upper portion of the base 701 and is attached to a stand 702. A liquid crystal optical element 720, which will be described later, is disposed on the upper surface of the support base 702.

  An arm 704 is located on the upper side of the support body 703 and is attached to the stand 702. An objective lens 721 is attached to the tip of the stand 702. A sample stage 705 is located above the arm 704 and is attached to the stand 702. A sample holder 722 is disposed on the upper surface of the sample table 705.

  A lens barrel 707 having an objective lens 723 is further attached to the stand 702. An imaging camera (for example, a CCD camera) 709 is attached on the optical axis of the lens barrel 707 via a filter 708.

  The output of the imaging camera 709 is supplied to a monitor 801 such as a personal computer.

  Reference numeral 711 denotes a laser light source, and laser light from the laser light source 711 is reflected by the reflection mirrors 712 and 713 and guided to the rising mirror 716 via the collimator lenses 714 and 715. The laser light from the rising mirror 716 is controlled by its optical characteristics in the liquid crystal optical element 720, focuses on the observation object (fine particles) of the sample holder 722 via the objective lens 721, and captures the fine particles. be able to.

  The three-dimensional movement position control of the fine particles can be performed by operating the control unit 810 and controlling the characteristics of the liquid crystal optical element 720. The control unit 810 will be described in detail later.

  The movement of the fine particles in the sample holder 722 is captured by the imaging camera 709 via the objective lens 723 and the filter 708, and the image is displayed on the monitor 801. The filter 708 is provided to cut the color of the laser light and accurately capture an image of the fine particles.

(Description of basic configuration and basic operation of liquid crystal optical element 720)
The liquid crystal optical element 720 will be described in detail. In FIG. 2, 111 is a 1st board | substrate (transparent glass), and the 1st electrode 21 (as a material is ITO material) is formed in the inner surface side. A second substrate (transparent glass) 112 is disposed on the first electrode 21 side so as to face each other in parallel. A second electrode 22 (made of Al) is formed outside the second substrate 112. As shown in FIG. 2B, the second electrode 22 has a round hole 222 (for example, a diameter of 4.5 mm).

  Between the first electrode 21 side of the first substrate 111 and the second substrate 112, a liquid crystal layer 311 (for example, 130 μm thick) in which liquid crystal molecules are aligned in one direction is formed. 41 and 42 are spacers for obtaining the liquid crystal layer 311.

  Furthermore, on the upper surface of the second electrode 22, a third electrode 23 (made of an ITO material as a material) is formed via an insulating layer 113 (for example, a thin glass of 70 μm). A protective layer (glass) 114 is disposed on the upper surface of the third electrode 23. The surfaces of the first and second substrates sandwiching the liquid crystal layer are coated with polyimide. Also, rubbing is performed in the x-axis direction.

  Here, when the optical element described above functions as a liquid crystal lens, a first voltage Vo is applied between the first electrode 21 and the second electrode 22. The voltage Vo is supplied from the voltage supply unit 52. Here, a voltage value at which the best optical characteristic (the characteristic at this time is referred to as the first stage optical characteristic) is set. Next, the second voltage Vc is applied to the first electrode 21 and the third electrode 23 independently of the first voltage Vo. The second voltage Vc is supplied from the voltage supply unit 52. By varying the second voltage Vc, the optical characteristic of the lens (referred to as the second stage optical characteristic) can be controlled. The optical characteristics of the second stage are varied from a state where the focal length is very close to a state where it is close to infinity (or infinite). This is a case where the second voltage Vc is uniformly changed in the second electrode 22.

  Here, the liquid crystal optical element 720 can deflect the focal position. For this purpose, the second electrode 22 is divided into a plurality of parts. For example, the second electrode 22 is divided into four as shown in FIG. The voltage applied to each of the electrodes 22a-22d can be variably controlled by the control unit 810.

  In FIG. 3, a voltage of Vo = 70 V (a fixed voltage value indicating the best characteristics) is applied between the first electrode 21 and the second electrode 22, and the second voltage ( The control voltage shows a potential distribution when Vc = 10V is applied. z is the optical axis direction, and y is the direction orthogonal to the optical axis. x, y, and z are the same as those in FIG. When the density of the plurality of equipotential lines indicating the potential distribution is high, the focal length of the lens is long, and when the density of the equipotential lines is low, the focal length of the lens is short.

  4A and 4B show another example of potential distribution. In FIG. 4A, a voltage of Vo = 70 V (fixed voltage value indicating the best characteristic) is applied between the first electrode 21 and the second electrode 22, and the second voltage (control voltage) Vc is applied. The potential distribution when = 10 V is applied is shown. FIG. 4B shows the potential distribution when the control voltage is varied and the second voltage (control voltage) Vc = 20 V is applied. This change in potential distribution corresponds to the tilt angle of the liquid crystal molecules and also corresponds to the light refraction angle. The focal length is longer in the state of FIG. 4B than in the state of FIG.

  FIG. 5 shows a state of the phase delay φ of light in the liquid crystal lens in the above embodiment. Basically, a square distribution characteristic is shown in which the phase delay gradually decreases from the center of the y-axis toward the periphery. Here, when the control voltage (second voltage) Vc is varied, the phase difference between the center and the periphery becomes smaller. That is, the focal length is longer at Vc = 50V than when Vc = 10V.

  FIG. 6 shows the relationship between the change in focal length of the optical element of the present invention and the previous control voltage Vc. The focal length is varied by varying the control voltage Vc. One embodiment of the present invention is not limited to the above configuration.

  FIG. 7A is a specific configuration example of the control unit 55, and FIG. 7B is an explanatory diagram showing movement positions of various focal lengths when the focal length is controlled by the control unit 810. is there.

  The voltage applied to the electrode 22a is extracted from the slider of the variable resistor 55a, and a divided voltage between the voltage + V and the voltage −V is extracted. Similarly, the voltage applied to the electrode 22b is extracted from the slider of the variable resistor 55b, and a divided voltage between the voltage + V and the voltage −V is extracted. The voltage applied to the electrode 22c is taken out from the slider of the variable resistor 55c, and a divided voltage between the voltage + V and the voltage −V is taken out. The voltage applied to the electrode 22d is extracted from the slider of the variable resistor 55d, and a divided voltage between the voltage + V and the voltage −V is extracted.

  By slightly varying the voltage applied to each electrode, the focal position can be moved in the x-axis direction or the y-axis direction, and further in both directions, as shown in FIG. 7B. It can also be moved in the z-axis direction. That is, it is possible to control the movement of the focal position within a three-dimensional range.

(Composite characteristics of the compound lens of the liquid crystal optical element 720 and the objective lens 721)
FIG. 8A shows the measurement result of the change in focal length f when the second voltage Vc is applied to the liquid crystal optical element 720. FIG. 8B shows the relationship between the focal length f _LC of the optical element 720 and the focal length f of the compound lens. FIG. 8C shows the relationship between the focal length f _LC of the optical element 720 and the focal spot size of the compound lens.

  Further, FIG. 9 shows the amount of movement of the captured fine particles in the optical axis (z) direction when the second voltage Vc is controlled.

  FIG. 10 shows the relationship between the voltage and the shift amount when fine particles (for example, polystyrene fine particles) are captured and the control unit 810 is adjusted and shifted. FIGS. 11A to 11D show a state in which the fine particles 812 are controlled to move on the screen 811 of the monitor 801. FIG. FIG. 11A shows a state in which the fine particles 812 have moved when, for example, the potential difference between the divided electrodes AC is changed to 15 V, 35 V, 55 V, and 72 V as the control potential.

  As described above, according to the present invention, it is possible to capture the fine particles at the focal position of the laser beam and control the movement in three dimensions as well as two dimensions. The present invention is not limited to such an embodiment, and the electrode 22 is divided into a larger number of electrodes, and the control voltage applied thereto is controlled, thereby further finely controlling the movement of the fine particles. It is possible.

FIG. 12 further shows another embodiment of the present invention. In this example, a plurality of pairs of liquid crystal optical elements and objective lenses (compound lenses) are used. That is, although this apparatus is a surface emitting laser array, a wide range 850 can be obtained as a sample moving area of the sample holder by devising its arrangement. On a circle 851 having a center 851, compound lenses L ₀ , L ₁ , L ₂ , L ₃ ,..., L ′ ₀ , L ′ ₁ , L ′ ₂ , L ′ ₃ ,. At this time, the optical axes of the compound lenses L ₀ , L ₁ , L ₂ , L ₃ ,..., L ′ ₀ , L ′ ₁ , L ′ ₂ , L ′ ₃ ,. Since the sample capturing area 850 is disposed between the center 851 and the compound lenses L ₀ , L ₁ , L ₂ , L ₃ ,..., L ′ ₀ , L ′ ₁ , L ′ ₂ , L ′ ₃ ,. is there. When configured in this way, particles are captured halfway by the beam of a certain compound lens, and these particles are captured and captured by the beam of the next compound lens, and the movement of the particles is controlled one after another. It becomes possible. As another usage, it is possible to use a method in which a plurality of fine particles are captured by the beam of each compound lens and the movement of each fine particle is independently controlled.

  In the present invention, the optical characteristics of the liquid crystal optical element are not limited to the above characteristics. The above characteristics have a focal length in the optical axis direction and a deflection characteristic in a direction crossing the optical axis, and the captured object near the focal point can be controlled in three dimensions.

  However, the liquid crystal optical element may have a characteristic capable of changing the polarization state of the laser light, and not only the three-dimensional position control of the captured object having optical anisotropy but also the direction of the anisotropy or the rotation operation. Control may be obtained. The polarization state can be easily controlled by adjusting the rubbing process or by providing a plurality of liquid crystal layers.

  Further, by the same processing, the liquid crystal optical element has an elliptical refractive index distribution characteristic, that is, an anamorphic lens characteristic, and three-dimensional position control of the captured object having geometrical or optical anisotropy. Not only that, it is also possible to obtain control of the anisotropic direction or rotational motion.

  A plurality of pairs of liquid crystal optical elements and corresponding objective lenses are arranged in a two-dimensional array, and a plurality of objects captured by applying a voltage to each liquid crystal optical element are independently controlled in three-dimensional positions. Control of the anisotropic direction or rotational motion may be obtained.

  Further, the liquid crystal optical element and the corresponding objective lens are integrated with a two-dimensional surface-emitting laser array, and a plurality of captured objects are not only three-dimensionally controlled but also anisotropic direction or rotation Operation control may be obtained.

  Alternatively, a plurality of liquid crystal optical elements and corresponding objective lenses may be arranged in a two-dimensional array, and a voltage may be applied to each liquid crystal optical element to cause laser light to interfere in the sample capturing area region. By performing this interference, it is possible to obtain not only three-dimensional control but also rotation control of a plurality of captured objects at the same time.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment. The shape of the third electrode may be given by either a sine wave function, a superposition function of the sine wave function, or a power function. Further, although one liquid crystal lens is shown, a configuration in which a plurality of liquid crystal lenses are arranged may be used. Further, it may be a two-dimensional array such as a compound eye.

  The optical element of the present invention can be used in various applications such as a magnifying lens and a lens of an imaging unit used as a visual function in a robot.

1 is a configuration explanatory view showing a configuration of a fine particle movement control device according to the present invention. FIG. FIG. 2 is a configuration explanatory view showing an embodiment of a liquid crystal optical element used in the apparatus of FIG. 1. FIG. 3 is an explanatory diagram illustrating an example of a potential distribution of an element in order to explain a function of the liquid crystal optical element illustrated in FIG. 2. It is explanatory drawing which shows the example in which the electric potential distribution of the element changed in order to demonstrate the function of the liquid crystal optical element shown in FIG. FIG. 3 is an explanatory diagram showing how the phase of a light wave passing through the optical element changes in order to explain the function of the liquid crystal optical element shown in FIG. 2. FIG. 3 is an explanatory diagram showing how the focal length with respect to a control voltage changes in order to explain the function of the liquid crystal optical element shown in FIG. 2. FIG. 2 is an explanatory diagram illustrating a specific configuration example of a control unit illustrated in FIG. 1 and transition of a focal position of a liquid crystal lens. The measurement result of the change in the focal length f when the second voltage Vc is applied to the liquid crystal optical element, the relationship between the focal length f _LC of the liquid crystal optical element and the focal length f of the compound lens, and the focal length of the liquid crystal optical element is an explanatory view showing the relationship between the spot size of the focus of the f _LC composite lens. It is explanatory drawing which shows the relationship between the movement distance at the time of carrying out movement control of the focus of a compound lens to an optical axis (z) direction, and the 2nd voltage Vc. It is explanatory drawing which shows the relationship between the voltage at the time of capture | acquiring and shifting fine particle and a shift amount. It is explanatory drawing which shows a mode that fine particle movement control is carried out on the screen of a monitor. It is explanatory drawing which shows the other example of the liquid crystal optical element which concerns on the apparatus of this invention.

Explanation of symbols

21 ... 1st electrode, 22 ... 2nd electrode, 222 ... hole, 23 ... 3rd electrode, 51, 52, 61, 62 ... Voltage supply part, 55 ... Control part, 111 ... 1st board | substrate, 112 2nd substrate, 113 ... Insulating layer, 114 ... Protective layer, 711 ... Laser light source, 720 ... Liquid crystal optical element, 721 ... Objective lens, 722 ... Sample holder, 723 ... Objective lens, 708 ... Filter, 709 ... Imaging camera , 801... Monitor, 810.

Claims (7)

  In an apparatus that collects a beam from a laser light source with an objective lens and captures an object near the focal point, the liquid crystal molecules are controlled by applying an external voltage between the laser light source and the objective lens, thereby effectively A fine particle movement control apparatus comprising: a lens having a liquid crystal optical element capable of varying a refractive index distribution characteristic; and controlling a position of the object by varying a focal position of incident laser light.   The liquid crystal optical element has a convex lens characteristic, a focal length in the optical axis direction, and a deflection characteristic in a direction crossing the optical axis, and controls the captured object near the focal point in three dimensions. The fine particle movement control device according to claim 1, wherein: The liquid crystal optical element has a characteristic capable of changing the polarization state of the incident laser light, and not only the three-dimensional position control of the captured object having optical anisotropy,
3. The fine particle movement control device according to claim 1, wherein control of an anisotropic direction or rotational operation can be obtained. The liquid crystal optical element has an elliptical refractive index distribution characteristic, that is, an anamorphic lens characteristic, and not only the three-dimensional position control of an object having a captured geometrical or optical anisotropy,
4. The fine particle movement control device according to claim 1, wherein control of anisotropic direction or rotational operation can be obtained.   If a plurality of pairs of the liquid crystal optical element and the corresponding objective lens are arranged in a two-dimensional array, and a plurality of objects captured by applying a voltage to each liquid crystal optical element are independently controlled in a three-dimensional position. 4. The fine particle movement control device according to claim 1, wherein control of anisotropic direction or rotational motion can be obtained.   The liquid crystal optical element and the corresponding objective lens are integrated with a two-dimensional surface emitting laser array, and a plurality of captured objects are not only three-dimensionally controlled but also anisotropically or rotated. 4. The fine particle movement control apparatus according to claim 1, wherein control is obtained.   A plurality of objects captured by arranging a plurality of liquid crystal optical elements and corresponding objective lenses in a two-dimensional array, applying a voltage to each liquid crystal optical element, and causing laser light to interfere in a sample capturing area region. 4. The fine particle movement control device according to claim 1, wherein not only three-dimensional control but also rotation control can be obtained simultaneously.

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