JP4214933B2 - Liquid viscosity measuring device and viscosity measuring method - Google Patents

Description

  The present invention relates to a technique for measuring the viscosity of a liquid using a laser. In the present invention, particles are trapped using a laser, and the viscosity of the liquid is measured by moving the trapped particles relative to the liquid.

A technique for measuring the viscosity of a liquid using a laser has been developed. According to this technique, it is possible to measure the viscosity in a minute region (local) as compared with other viscosity measuring methods.
Non-Patent Document 1 discloses a viscosity measurement method using a laser trapping method. In this method, a particle that is floating in the liquid is irradiated with a condensing laser, the particle is trapped at the condensing position of the laser, and the liquid and the laser converging position are relative to each other with the particle trapped at the condensing position. Move to. The particles are subjected to a trapping force caused by a focused laser and a resistance force due to the viscosity of the liquid. When the viscous resistance exceeds the laser trapping force, the particles leave the focusing position. Viscosity resistance force can be measured from the laser trapping force acting on the particles when they are removed from the focusing position, and the viscosity of the liquid can be obtained by adding the relative velocity of the particles and the particle radius to the viscosity resistance force. it can. The laser trapping force is determined by the output of the laser, the refractive index of the particle, the radius of the particle, etc. If the particles are the same, it is determined by the output of the laser.

Iwashita Masataka, Master's thesis, University of Tokyo, 2000, p. 7-8

  There are several methods for removing particles trapped at the laser focusing position from the focusing position. In one method, the laser trapping force is reduced by gradually decreasing the laser output while maintaining the relative velocity v of the particles trapped by the laser with respect to the liquid constant. In this method, a laser trap force (identified from a laser output) when particles are detached from a laser condensing position is measured. In another method, the relative velocity v of the particles trapped by the laser to the liquid is increased while maintaining the laser trapping force constant by maintaining the laser output constant. In this method, the relative velocity v when the particles are detached from the laser focusing position is measured.

In the laser trapping method, the viscosity of the liquid is obtained based on Stokes' law. According to Stokes' law, when a particle having a radius R moves in a liquid having a viscosity η at a relative speed v, the viscous resistance force F acting on the particle is given by equation (1).
F = 6πηRv (1)
In the laser trapping method, it is assumed that a viscous resistance force F having a magnitude equal to the laser trapping force is applied when particles are detached from the laser condensing position.
Equation (2) for viscosity η is derived from equation (1).
η = (1 / 6πR) (F / v) (2)
Substituting into equation 2 the particle radius R, the laser trapping force F when the particle is released from the laser focusing position, and the relative velocity v when the particle is released from the laser focusing position, the viscosity of the liquid η can be obtained.

According to the study by the present inventors, it has been found that the measurement results when the viscosity is measured by the laser trapping method may vary. As a result of exploring the cause, the following events have been found.
In the technique of measuring the viscosity of a liquid using a laser, before moving the laser focusing position relative to the liquid, the laser focusing position and the position of particles floating in the liquid are matched to each other. It is necessary to trap the particles at the light position. In the prior art, an optical microscope installed above the liquid is used to match the laser focusing position with the particle existence position.

According to the position adjustment technique using the optical microscope installed above the liquid, it is possible to make the laser converging position coincide with the particle existing position while observing in a plane parallel to the liquid surface. However, in the depth direction of the liquid, it is not guaranteed that the laser condensing position and the particle existing position coincide.
The laser trapping force acts not only in the plane parallel to the liquid surface but also in the liquid depth direction. That is, the laser trapping force tries to maintain the particles at the condensing position in any three-dimensional direction.
If the viscosity of the liquid is low, the laser trapping force acting in the depth direction of the liquid will be sufficient if the laser focusing position and the particle location in the depth direction of the liquid do not match exactly, As a result, the particles move in the depth direction of the liquid, and the condensing position and the particle position also coincide in the depth direction of the liquid. If the thickness of the liquid is thin, the laser converging position in the depth direction of the liquid and the presence position of the particles are almost the same. Inconsistencies were never a problem.

  However, when the viscosity of the liquid is high, the laser trapping force acting in the depth direction of the liquid cannot move the particles in the depth direction of the liquid, and the condensing position and the particle position coincide in the depth direction of the liquid. In some cases, the measurement by the laser trapping method may be completed without doing so, and it has been found that the measurement results vary due to this. The laser trapping force is distributed three-dimensionally with the laser focusing position as the center. Unless the laser condensing position and the particle existence position are matched not only in the plane parallel to the liquid surface but also in the depth direction of the liquid, the same laser trapping force cannot be obtained even with the same laser output. Since the laser trapping force is determined by the laser output in the laser trapping method, the measurement results vary if the same laser output does not result in the same laser trapping force.

  The present invention addresses the problems found by the above research and suppresses variations in measurement results by solving the problem that the same laser trapping force does not occur even with the same laser output.

The present invention irradiates particles floating in a liquid with a focused laser, traps the particles at the focused position, and measures the viscosity of the liquid by moving the trapped particles relative to the liquid. Embodied in a device.
The viscosity measuring apparatus of the present invention includes a first optical system for generating a focused laser for irradiating the particles, and a second optical system capable of detecting the presence position in 3-dimensional space of the particles suspended in the liquid A position adjusting means for matching a condensing position of the condensing laser generated by the first optical system in the three-dimensional space with an existing position of the particles detected by the second optical system in the three-dimensional space; And a means for moving the focusing position of the focusing laser generated by one optical system relative to the liquid.
The position adjusting means for matching the condensing position of the condensing laser generated by the first optical system in the three-dimensional space and the position of the particles detected by the second optical system in the three-dimensional space is the entire liquid May be used to change the position where the particles are present, or may be used to change the focusing position of the focusing laser. That is, the position adjusting means is characterized in that at least one of the condensing position of the condensing laser and the presence position of the particles can be moved in three axial directions. Further, this position adjusting means may be a means for diverting the focusing position of the focusing laser relative to the liquid.

According to the above-described viscosity measuring apparatus, by using the second optical system, the position of the particles suspended in the liquid can be measured three-dimensionally (not only in the plane parallel to the liquid surface but also in the depth direction of the liquid). (Including) can be detected accurately. Therefore, it is possible to three-dimensionally match the particle existence position and the laser focusing position (including not only in the plane parallel to the liquid surface but also in the liquid depth direction). Therefore, the relationship between the laser output and the laser trapping force is stabilized, and the problem that the same laser trapping force is not obtained even with the same laser output is solved. According to the above viscosity measuring apparatus, even when the viscosity of the liquid is high, the measurement result does not vary, and the true viscosity of the liquid can be accurately measured.
Although the present invention may be understood to be the one in which the position where the particles are present and the focused position of the laser are also coincided with each other in the depth direction of the liquid, the conventional technique works in the depth direction of the liquid. It was created in the presence of circumstances where it was thought that it was not necessary to precisely match the position of the particle and the focused position of the laser at the liquid depth due to the laser trapping force. It is impossible to evaluate that the laser condensing position is also made coincident with the depth direction of the liquid.

  The second optical system includes a parallel light generator, an objective lens that condenses the parallel light at the focal point and converts radiation light from the focal point into parallel light, a converging lens that condenses the parallel light at the focal point, and a converging lens It is preferable to have a pinhole arranged at the focal point of and a detector for detecting light that has passed through the pinhole.

The second optical system is a so-called confocal optical system, and the detection light intensity when particles are present at the focus of the objective lens and the detection light intensity when particles are not present at the focus of the objective lens are sensitive. To change. Even if particles are present on the optical axis of the objective lens, the detected light intensity when the particles are deviated from the focal point of the objective lens in the depth direction, and particles are present at the focal point of the objective lens even in the depth direction. The detected light intensity changes sensitively. This makes it possible to accurately detect whether or not particles are present at the focal point of the objective lens in the depth direction.
If it is found that particles are present at the focal point of the objective lens even in the depth direction, the focal depth of the particle trapping laser may be made to coincide with the focal depth of the objective lens of the second optical system.
When the presence / absence of particles is detected by a photodetector, any of reflection, absorption, and scattering phenomenon by particles may be used. If the particles are stained with a fluorescent material, luminescence can be used.

A configuration in which the parallel laser generator and objective lens of the first optical system also serve as the parallel light generator and objective lens of the second optical system may be employed. Or the structure which is not combined can also be employ | adopted.
If the dual-use configuration is adopted, not only the device configuration is simplified, but if it is confirmed that particles are present at the focal position of the objective lens using the second optical system, it is naturally used for trapping. Thus, the particles are present at the laser focusing position, and the operability is also improved.
If a configuration that does not serve as both is employed, the trapping laser beam and the parallel beam for particle position detection can be separated. The trapping laser light is required to have a high output in order to secure a trapping force, and when irradiated for a long time, the temperature of the liquid may increase and the viscosity may change. The collimated light for particle position detection may have a small output and does not change the viscosity in order not to raise the temperature of the liquid even when irradiated for a long time. In the particle position detection stage, small output light is used, and in the viscosity detection stage, a high output laser is irradiated for a short time to detect the viscosity.

  The second optical system includes at least two photodetectors, and each photodetector detects the position of the particle in a three-dimensional space by observing the particle existence site from different directions. Preferably there is.

By observing the particle location from a plurality of directions, it is possible to know the particle location in the three-dimensional space. The photodetector may be a CCD camera or the like that can measure the light intensity distribution in the field of view. Alternatively, for example, a phototransistor or the like that can measure the total light intensity within a narrow visual field may be used. In the latter case, if the center line of the field of view of two or more photodetectors is positioned so as to intersect at the condensing position of the trapping laser beam, both of the two or more photodetectors detect the presence of particles. By adjusting the positional relationship, the condensing position of the trapping laser light in the three-dimensional space and the particle existence position in the three-dimensional space can be matched.
When the presence / absence of particles is detected by a photodetector, any of reflection, absorption, and scattering phenomenon by particles may be used. If the particles are stained with a fluorescent material, luminescence can be used.

When measuring the viscosity using the laser trapping phenomenon, the present inventors have determined the position of the particles floating in the liquid in the three-dimensional space and the concentration of the trapping laser in the three-dimensional space. We recognized for the first time the importance of precisely matching the light position.
The present invention can also be embodied in a method for accurately measuring viscosity. The method created in the present invention is to irradiate particles floating in a liquid with a focused laser, trap the particles at the focused position, and move the focused position relative to the liquid. This is a method of measuring the viscosity of the liquid by moving the particles trapped at the condensing position relative to the liquid, and prior to moving the condensing position relative to the liquid, the three-dimensional space of the condensing laser And a step of matching the position where the light is focused and the position where the particles are present in the three-dimensional space. In this step, a position adjusting means capable of moving at least one of the laser condensing position and the particle existing position in the three-axis directions is used.

  Prior to the relative movement of the condensing position with respect to the liquid, if the step of matching the condensing position in the three-dimensional space with the particle existence position in the three-dimensional space is performed, the reproducibility of the measurement result is greatly increased. improves. It becomes possible to accurately measure the true viscosity of a liquid (particularly the viscosity of a highly viscous liquid).

  According to the present invention, it is possible to accurately measure the true viscosity of a liquid to be measured.

First, the main features of the present invention are listed.
(Embodiment 1)
The liquids to be measured are various liquids such as paints and polymer materials. In particular, the present invention is particularly effective for a highly viscous liquid. The form of the liquid is not particularly limited, and it may be a thin film or a laminated film, or a dispersion system composed of two or more phases. Viscosity can be measured for each film or each phase having only a minute volume.
(Embodiment 2)
Means for changing the temperature of the liquid to be measured. Viscosity can be measured at any temperature.
(Embodiment 3)
The particles may be any particles that float in the liquid without sedimentation. In order to prevent precipitation, the surface of the particles may be treated. Particles may be added to the liquid for viscosity measurement, but particles previously contained in the liquid can also be used.
(Embodiment 4)
The particles themselves may be a substance that emits light of a predetermined wavelength (fluorescence or the like) to the irradiation laser, or such a substance may be bound to the surface of the particles. Since the detection accuracy in the confocal system is improved, the position of the particles floating in the liquid can be detected with high accuracy.
(Embodiment 5)
The shape of the particles is not particularly limited, but is preferably spherical. In the case of spherical particles, the above equation (1) is established, so that measurement is easy and measurement accuracy is high. The particle diameter is required to be sufficiently smaller than the three-dimensional dimension of the liquid mass to be measured. This is because the formula (1) is established when the value is sufficiently small. The particle size distribution is preferably as small as possible. The particle size is indispensable for calculating the viscosity. If the distribution range is sufficiently small, the average particle size can be used as the particle size for viscosity calculation, and it is not necessary to measure the particle size every time the viscosity is measured. On the other hand, if the distribution range is large, the particle diameter must be measured every time the viscosity is measured.
(Embodiment 6)
The particles trapped by the laser are preferably transparent to the laser. The material of the particles is small in absorption, scattering, and reflection, and preferably has a refractive index higher than that of the liquid.
(Embodiment 7)
The concentration of particles in the liquid is preferably as low as possible within a range that does not take more time than necessary to find the particles to be trapped by irradiation with the laser. This is because if the concentration is high, the influence of the concentration of the particles on the viscosity of the liquid cannot be ignored.
(Embodiment 8)
A laser generator used for the laser trapping method has a laser light source and a condensing optical system. (Embodiment 9)
As the laser light source, various lasers such as a solid-state laser, a gas laser, and a semiconductor laser can be used. The wavelength of the laser is desirably one that does not affect the liquid and particles, and specifically, it is desirable that the absorption by the liquid and particles be as small as possible. The laser preferably uses a Gaussian beam having an intensity gradient. It is desirable that the laser power be as large as possible without adversely affecting the liquid and particles. This is because the magnitude of the force with which the laser traps particles is proportional to the laser power, and the higher the trapping force, the higher the accuracy of measurement. The laser power is preferably variable.
(Embodiment 10)
The condensing optical system condenses the laser from the laser light source so as to focus on the liquid to be measured.
(Embodiment 11)
The distance between the condensing optical system and the liquid is preferably short. This is because the spot diameter at the condensing position is proportional to the focal length, so that the shorter the distance, the smaller the spot diameter, the higher the power density at the condensing position and the greater the trapping force. In addition, according to the present invention, it can be said that it is particularly effective because the position of the floating particles can be matched in three dimensions with respect to the condensing position where the spot diameter is small and the power density is high.
Embodiment 12
The relative movement device of the condensing position and the liquid may be one that applies the viscous resistance force of the liquid to the trapped particles by moving the condensing position, or applies the viscous resistance force to the trapped particles by moving the liquid. It may be a thing. In the former case, a galvanometer mirror can be used, and in the latter case, fine movement means such as a piezo element can be used. The latter is preferable because it can be manufactured easily and at low cost.
(Embodiment 13)
The relative movement device is preferably a device that linearly moves trapped particles or liquid at a constant speed. This is because Stokes' law of the formula (1) is used for calculating the viscosity. When the inertial force is negligible compared with the viscous resistance force of the above formula (1), a constant acceleration linear motion, a constant velocity circular motion, or a simple vibration may be used. The direction of motion is not limited, but it is preferable to be in a two-dimensional plane perpendicular to the incident surface of the laser in order to easily calculate the viscosity.
(Embodiment 14)
As the particle measuring device, a microscope, a video camera, an image analysis device, or the like can be used. When the particle measuring apparatus performs automatic measurement, it is preferable to have a photodetector and detect the interaction light between the laser and the particles irradiated with the laser with the photodetector. You may detect the interaction light with the light from the light source different from a laser, and the particle | grains with which the laser was irradiated. As the photodetector, for example, a semiconductor photodetector such as a photodiode, a photomultiplier tube, or the like can be used. By using a small photodetector, not only can the size of the entire viscosity measuring apparatus be reduced, but also the cost can be simplified and reduced. In addition, an electrical device such as an electrostatic capacity type motion meter, a magnetic device using particles as magnetic particles and using a magnetic sensor, a sound device such as an ultrasonic motion meter, or the like may be used.
(Embodiment 15)
Light (reflection light, transmitted light, scattered light, fluorescence, etc.) due to the interaction of reflection, absorption, scattering, fluorescence, and the like by the particles is generated when the particles are irradiated with light, but is not generated when the particles are not irradiated. Therefore, in the case where the motion is detected based on whether or not the particles remain at the laser focusing position by the particle measuring device having the photodetector, the motion can be detected by detecting the presence or absence of the interaction light due to the particles. .
(Embodiment 16)
In order to accurately measure the true viscosity of the liquid, it is preferable to measure the viscosity of particles floating in various places such as the upper layer, middle layer, and lower layer of the liquid, and use the average value as the measured value. Alternatively, the viscosity is measured by particles suspended at the center of the liquid being supported (the surface vicinity is in contact with the liquid support, for example, and external influences are thought to overlay the measured values). Is preferred.

Embodiments will be described in detail below with reference to the drawings.
First Example FIG. 1 shows a schematic configuration diagram of a viscosity measuring apparatus according to a first example.
22 is a glass plate, and a liquid 24 to be measured is applied to the glass plate 22. In this liquid 24, spherical silica having a very small particle size distribution is added and floated.

A condensing optical system (first optical system) is formed by the trap laser generator 32, the first galvanometer mirror 34, the condensing lens 36, and the like.
The first galvanometer mirror 34 can move two-dimensionally in a plane (a plane parallel to the liquid surface) perpendicular to the optical axis (in this example, the vertical direction on the paper surface). Further, the condensing lens 36 is configured to be movable along the optical axis (along the depth direction of the liquid 24) by an adjustment mount (not shown) or the like. The condensing position of the laser can move in the liquid 24 in three dimensions.
The parallel laser from the trap laser generator 32 is condensed in the liquid 24 by the condenser lens 36 and can trap the floating particles 26.

On the other hand, a confocal optical system includes a position detection laser generator 42, a half mirror 43, a second galvanometer mirror 44, an objective lens 45, a converging lens 46, a confocal pinhole 47, a photodetector 48, and the like. (Second optical system) is formed.
The objective lens 45 condenses the parallel laser from the position detection laser generator 42 at the focal point in the liquid 24 and converts the emitted light from the focal point into parallel light. The converging lens 46 focuses parallel light on the confocal pinhole 47. The photodetector 48 can detect light that has passed through the confocal pinhole 47.
The second galvanometer mirror 44 can move the focal point of the objective lens 45 in a two-dimensional manner in a plane perpendicular to the optical axis (a plane parallel to the liquid surface). Further, the objective lens 45 is configured to be movable along the optical axis (along the depth direction of the liquid) by an adjustment mount (not shown), whereby a parallel laser beam from the position detection laser generator 42 is obtained. Is movable in the liquid 24 in three dimensions.

  The parallel laser from the position detection laser generator 42 is focused on the liquid 24 via the half mirror 43, the second galvanometer mirror 44, and the objective lens 45. By scanning the focal point in three dimensions, the particle 26 floating in the liquid 24 is focused. The reflected light from the particles 26 present at the focal point returns to the incident optical path by the objective lens 45 and the galvanometer mirror 44, passes through the half mirror 43, and forms an image on the confocal pinhole 47 through the converging lens 46. The By using the confocal pinhole 47, the light intensity from only the reflected light of the particle 26 at the focal point in the liquid 24 can be detected by the photodetector 48. Thereby, the position of the particles 26 suspended in the liquid 24 can be detected in three dimensions.

The viscosity measuring method according to the first embodiment will be described. Prior to the measurement, a calibration curve illustrated in FIG. 2 is obtained.
In order to obtain a calibration curve, particles having a known radius are suspended in a liquid having a known viscosity by an existing method that does not use a laser, and the particles are trapped at a condensing position by a laser. In this state, the condensing position with respect to the liquid 24 when the condensing position is displaced with respect to the liquid 24 and the particles cannot be trapped in the condensing position due to the viscous resistance acting on the trapped particles. The moving speed and the output of the laser trapping the particles are detected. Relationship between "viscosity, moving speed, and laser output" when it becomes impossible to trap particles for various liquids with different viscosities by changing the laser output, changing the moving speed By arranging the above, the calibration curve of FIG. 2 can be obtained.

After obtaining a calibration curve, the viscosity measurement process for a liquid whose viscosity is unknown is started.
First, the position of the suspended particle 26 is detected by scanning the focal point in three dimensions in the liquid 24 applied to the liquid support 22 using a confocal optical system. At this stage, the trap laser generator 32 of the condensing optical system is not operating.
Next, the detected three-dimensional position of the particle 26 is transmitted to the computer 52, and the computer 52 corresponds to the three-dimensional position of the particle 26 to collect with the first galvanometer mirror 34 of the condensing optical system. The position of the optical lens 36 is adjusted so that the condensing position of the laser from the trap laser generating device 32 coincides with the position of the detected particle 26. Thereby, the position of the particle | grains 26 which are floating and the condensing position of a laser can be made to correspond in three dimensions. As a result, a constant trapping force corresponding to the laser output can be applied to the particles 26.

  With the laser output from the trap laser generator 32 kept constant, the trap particles 26 are linearly moved relative to the liquid 24 by the first galvanometer mirror 34 of the condensing optical system. At this time, the focal point of the confocal optical system is also moved following the movement of the trap particles 26. This may be achieved by controlling the first galvanometer mirror 34 and the second galvanometer mirror 44 in synchronization using the computer 52. Then, viscous resistance force from the liquid 24 acts on the trapped particles 26. The viscous resistance force tries to overcome the trapping of the particles 26 at the condensing position. If the moving speed is increased while keeping the laser output constant, the trapped particles 26 are detached from the laser focusing position when a certain moving speed is reached. When the trapped particles 26 leave the condensing position, the light intensity detected by the photodetector 48 of the confocal optical system decreases. The moment when the light intensity decreases is a state where the trapping force of the laser and the viscous resistance force are balanced. From the laser output at this time and the moving speed of the particles 26, the viscosity of the liquid 24 can be calculated using a calibration curve obtained in advance.

According to the above embodiment, since the position of the floating particle 26 and the condensing position of the laser from the trap laser generator 32 can be matched in three dimensions, the true viscosity of the liquid can be accurately determined. Can be measured. Moreover, the reproducibility of viscosity measurement can be improved.
According to the confocal optical system of the above-described embodiment, the second galvanometer mirror 44 and the objective lens 45 can be used to scan the focus in the liquid 24 in three dimensions, and the position of the particle 26 can be detected in a very short time. can do.
Until the position of the suspended particle 26 is detected, only the low-power position detection laser generator 42 is used, and the viscosity is measured by irradiating the high-power laser for a short time at the viscosity detection stage. Can be implemented. Problems such as an increase in the temperature of the liquid 24 can be avoided.

As a modification of the first embodiment, the viscosity of the liquid can also be measured by the following method.
(1) The moment when the trap particles 26 are detached from the condensing position of the laser may be detected by reducing the laser output while keeping the moving speed of the trap particles 26 constant.
(2) Using the first galvanometer mirror 34 of the condensing optical system, the trap particles 26 are displaced so as to draw a circle in a plane perpendicular to the optical axis, and a viscous resistance force from the liquid acts on the trap particles 26. You may let them. In this case as well, the moment when the trapped particles 26 leave the condensing position is detected by a technique in which the laser output is decreased while the circular motion period remains constant, or the circular motion period is decreased while the laser output remains constant. can do.
(3) The position detection laser generator 42 does not have to be a laser generator and may be any apparatus that can generate parallel light. For example, a device that converts light from a light source such as a lamp into parallel light through a pinhole may be used.
(4) The moment when the trapped particles 26 leave the light collection position may be detected visually using a microscope. According to this configuration, after detecting the position of the floating particle using the confocal optical system, the laser irradiation from the position detection laser generator 42 can be stopped. It is possible to eliminate the influence of the trapping force acting on the particles by the laser itself from the position detection laser generator 42 and the influence of the liquid temperature rising by the laser from the position detection laser generator 42. it can.
(5) The moment when the trapped particles 26 leave the condensing position may be detected by image analysis using a video camera. In addition to the same effect as (4), the viscosity measurement is automated, so it is not time-consuming and suitable.
(6) The viscosity may be measured by irradiating a suspended particle with a laser and moving the particle by its light pressure. In this case, after the position of the floating particle is detected by the confocal optical system, the particle is irradiated with a laser from the condensing optical system. The particles move by receiving a light pressure corresponding to the laser output. Using the installed video camera, this particle movement is recorded and recorded. The moving speed of the particles can be measured by analyzing the image of this photographing record with a computer. Thereby, the viscosity of the liquid can be measured. According to this example, as compared with the case where particles are trapped with a laser, the laser irradiation time is short, and an increase in the temperature of the liquid can be suppressed.
Even when measuring with the laser light pressure, prior to the measurement, the laser light pressure is applied to particles suspended in a liquid of known viscosity, and the "viscosity, moving speed, and laser output" It is necessary to obtain a calibration curve for the relationship.

(Second embodiment)
In FIG. 3, the schematic block diagram of the viscosity measuring apparatus of 2nd Example is shown.
122 is a glass plate 122, and a polymer solution 124 having a viscosity of 1 Pa · s is applied to the glass plate 122. About 10 ⁻³ wt% of particles 126 made of spherical borosilicate silica having a very small particle size distribution and a radius of 1 μm are suspended in the polymer solution 124. The polymer solution 124 is applied on the glass plate 122 so as to have a film thickness of 50 μm.
The glass plate 122 is placed on a piezo stage 125 (125X, 125Y, 125Z). The piezo stage 125 has a piezo element configured to be displaceable in three axial directions (X, Y, and Z directions). The piezo stage 125 is movable in three axial directions (X, Y, and Z directions) with the plane parallel to the liquid surface as the XY plane and the depth direction of the liquid 124 as the Z axis. As the piezo stage 125 moves in the triaxial direction, the glass plate 122 can also move in the triaxial direction.

  The laser generator 142 is a YAG laser having a wavelength of 532 nm, and the parallel laser generated from the laser generator 142 is reflected by the half mirror 143 and is one point in the polymer solution 124 via the condenser lens 145. It is focused on. When the particle 126 is present at the condensing position, the particle 126 is trapped at the condensing position, and the reflected light from the particle 126 passes through the half mirror 143 via the condensing lens 145, and further converges. 146 forms an image on the confocal pinhole 147. By using the confocal pinhole 147, the light intensity from only the reflected light of the particle 126 at the condensing position can be detected by the photodiode 148. In this embodiment, a laser for laser trap and a laser for particle position detection are used in combination, and only one laser generator 142 is provided. The positions of the laser generator 142, the half mirror 143, the condensing lens 145, the converging lens 146, and the confocal pinhole 147 are fixed by a gantry or the like (not shown). Therefore, in this embodiment, the laser condensing position is also fixed.

Next, a method for measuring the viscosity according to the second embodiment will be described. A calibration curve as shown in FIG. 2 is obtained in advance.
First, the piezo stage 125 was moved in three axis directions. Then, since the particle 126 entered the laser condensing position, the light intensity detected by the photodiode 148 increased. The movement of the piezo stage 125 was stopped at a location where the light intensity increased. As a result, the condensing position of the laser and the position of the particle 126 floating in the polymer solution 124 are matched in three dimensions, and the particle 126 can be trapped by the laser.
Next, if the moving speed of the piezo stage 125 is increased from 5 μm to 1 μm in the horizontal plane (XY plane) with the laser output kept constant, the photodiode 148 is moved when the moving speed is 9 μm. The light intensity detected at 1 decreased. As a result, it was found that the trapped particles 126 were detached from the condensing position when the moving speed was 9 μm. From the calibration curve obtained in advance, it was calculated that the viscosity of this liquid was 1 Pa · s, and it was confirmed that the true viscosity of the liquid could be accurately measured.
When the same measurement was repeated 5 times, the viscosity was measured as 1 Pa · s, and good reproducibility was confirmed.

(Comparative example)
Next, a comparative example of the second embodiment was examined. In this comparative example, the position adjustment was performed only with the optical microscope installed above the liquid without using the confocal optical system of the second example. Therefore, although the position in the plane parallel to the liquid surface (XY plane) is adjusted, position adjustment in the depth direction (Z-axis direction) of the liquid is not guaranteed. Note that the detachment of particles from the condensing position was detected by a CCD camera.
When the moving speed of the piezo stage 125 is increased by 5 μm to 1 μm in a plane parallel to the liquid surface (XY plane) while the laser output is kept constant, the laser focusing position is increased when the moving speed is 7 μm. It was observed with a CCD camera that the trapped particles 126 were detached. From the calibration curve obtained in advance, the viscosity of this liquid was calculated to be 1.3 Pa · s, which deviated from the true viscosity (1 Pa · s) of the liquid.
When the same measurement was repeated 5 times, the viscosity was measured as 1.3 Pa · s, 0.9 Pa · s, 1.0 Pa · s, 1.8 Pa · s, and 0.6 Pa · s. The measured value has an error of up to 3 times. From this result, it was found that it is very important to make the laser focusing position and the particle position coincide in this kind of viscosity measurement technique. .

(Third embodiment)
In FIG. 4, the schematic block diagram of the viscosity measuring apparatus of 3rd Example is shown.
Reference numeral 222 denotes a glass plate 222 (or plastic that transmits light), and a coating material 224 having a viscosity of 0.5 Pa · s is applied to the glass plate 222. In this paint 224, particles 226 made of spherical polystyrene having a very small particle size distribution and a radius of 0.5 μm are added and floated by about 10 ⁻³ wt%. The paint 224 is applied on the glass plate 222 so as to have a film thickness of 100 μm.
One end of the glass plate 222 is fixed to a stage 228. This stage 228 is controlled by a computer in three axial directions (the plane parallel to the liquid surface is the XY plane, and the depth direction of the liquid is the Z-axis direction. ) Can be moved. As a result, the glass plate 222 is also movable in the three-axis direction as the stage 228 is moved in the three-axis direction.

  The trapping laser generator 232 is a YAG laser having a wavelength of 1064 nm, and the parallel laser generated from the laser generator 232 is reflected by the half mirror 234 and is a point in the paint 224 via the condenser lens 236. It is focused on. When the particle 226 exists at this condensing position, the particle 226 is trapped at the condensing position.

In the figure, reference numeral 272 denotes a halogen lamp 272, and among the optical paths of light from the halogen lamp 272, the optical path of transmitted light that has passed through the particles 226 is indicated by a broken line.
The optical path of one transmitted light is transmitted through the condenser lens 236 and the half mirror 234, and its light intensity is detected by the photodiode 276 via the converging lens 274. The other optical path is detected by a CCD camera 278. That is, it is possible to detect light from different directions.
The positions of the trap laser generator 232, the half mirror 234, the condensing lens 236, and the converging lens 274 are fixed by a frame (not shown) or the like. The optical axis is fixed in a direction perpendicular to the liquid surface.

Next, a method for measuring the viscosity according to the third embodiment will be described. A calibration curve as shown in FIG. 2 is obtained in advance.
First, the stage 228 was programmed to move in three axial directions under computer control and stop at a point where the light intensity detected by the photodiode 276 increases. At this time, the positional relationship between the laser condensing position and the floating particles 226 is the same in a plane parallel to the liquid surface (XY plane). However, it was confirmed by the CCD camera 278 that it did not coincide with the Z-axis direction (optical axis direction). Therefore, the stage 228 was moved along the Z-axis direction, and the laser condensing position and the position of the floating particle 226 were matched in three dimensions.
According to the present embodiment, until the position adjustment stage can be performed using the halogen lamp 272 without using a laser, the temperature rise of the paint 224 can be suppressed and an expensive laser can be used. Since it can be avoided, it is suitable for extending the service life of the laser.

Next, laser was irradiated from the trap laser generator 232 to trap the particles 226.
Using the stage 228, the glass plate 222 was linearly moved at a constant speed of 1 μm in a plane parallel to the liquid surface (XY plane). When the laser output was decreased by 1% from the maximum value every second in this state, the light intensity detected by the photodiode 276 decreased when the laser output decreased to 47%. Thereby, it was found that the trapped particles 226 were detached from the condensing position at the time of this laser output. Note that the light intensity detected by the photodiode 276 detects the light from the halogen lamp 272, so that the trap particles 226 can be accurately separated without being mistaken as a decrease in light intensity due to a decrease in laser output. Can be detected. From the calibration curve obtained in advance, it was calculated that the viscosity of this liquid was 0.5 Pa · s, and it was confirmed that the true viscosity could be accurately measured.
When the same measurement was repeated 5 times, the viscosity was measured as 0.5 Pa · s, and the reproducibility was confirmed.

In the above-described embodiment, the case is described in which the viscosity of the liquid is measured by trapping the particles at the focusing position of the focusing laser and moving the trapped particles relative to the liquid.
On the other hand, the viscosity of the liquid can also be measured by irradiating the particle with a focused laser and moving the particle relative to the liquid with light pressure. Also in this case, it is useful to match the focused position of the focused laser beam in the three-dimensional space with the existing position of the particles in the three-dimensional space. This greatly improves the reproducibility of measurement results.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

The schematic block diagram of 1st Example is shown. An example of a calibration curve is shown. The schematic block diagram of 2nd Example is shown. The schematic block diagram of 3rd Example is shown.

Explanation of symbols

22: Liquid support 24: Measurement sample 32: Trapping laser generator (an example of a first laser generator)
42: Position detection laser generator (an example of a second laser generator)

Claims (5)

It is a device that measures the viscosity of a liquid by irradiating a focused laser on particles floating in the liquid, capturing the particles at the focused position, and moving the captured particles relative to the liquid,
A first optical system that generates a focused laser that irradiates the particles;
A second optical system capable of detecting the presence position in 3-dimensional space of particles suspended in a liquid,
And the condensing position in 3-dimensional space of the condensing laser first optical system occurs, a position adjusting means for matching the present position in the three-dimensional space of the detected particles in the second optical system,
Means for moving the focusing position of the focusing laser generated by the first optical system relative to the liquid;
A has,
The viscosity measuring apparatus characterized in that the position adjusting means is capable of moving at least one of the condensing position or the existing position in three axial directions .   The second optical system includes a parallel light generator, an objective lens that condenses the parallel light at the focal point and converts radiation light from the focal point into parallel light, a converging lens that condenses the parallel light at the focal point, and a converging lens The viscosity measuring apparatus according to claim 1, further comprising: a pinhole disposed at the focal point of the first and a detector for detecting light that has passed through the pinhole.   3. The viscosity measuring apparatus according to claim 2, wherein the parallel laser generator and the objective lens of the first optical system also serve as the parallel light generator and the objective lens of the second optical system.   The second optical system includes at least two photodetectors, and each photodetector detects a position where the particles exist in a three-dimensional space by observing the existence site of the particles from different directions. The viscosity measuring apparatus according to claim 1, wherein: The particles suspended in the liquid are irradiated with a condensing laser to capture the particles at the condensing position, and the particles captured at the condensing position are moved relative to the liquid by moving the condensing position relative to the liquid. It is a method of measuring the viscosity of the liquid by relative movement,
Prior to the relative movement of the condensing position with respect to the liquid, the step of matching the condensing position of the condensing laser in the three-dimensional space with the position of the particles in the three-dimensional space ,
In the step, a liquid viscosity measuring method using a position adjusting means capable of moving at least one of the light condensing position or the existence position in three axial directions .

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