JP4563600B2 - Light scattering measurement probe - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light scattering measurement probe that performs light scattering measurement by irradiating a sample with light and detecting light scattered from within a scattering volume.
[0002]
[Prior art]
Light scattering measurement device is used to determine the diffusion coefficient and hydrodynamic size of particles by measuring the fluctuation (time change) of scattered light intensity caused by the movement of particles (Brownian motion) in the fluid. It is a device.
In a conventional light scattering measurement device, a cylindrical or rectangular parallelepiped cell containing a sample fluid is irradiated with laser light through a lens, and the observation volume of the scattered light emitted from the sample is limited by a pinhole or the like. The light was measured with a photodetector such as a photomultiplier through the light receiving optical system.
[0003]
In this conventional light scattering measurement device, since the optical path length of the sample fluid in the cell is long, when the particle concentration of the solution increases, scattering by the scattered light (multiple scattering) occurs in the cell, and accurate scattered light information is obtained. It cannot be measured.
Therefore, a structure of a light scattering measurement probe has been proposed in which the end faces of the incident optical fiber and the receiving fiber are opposed to each other at a predetermined angle in the cell and the distance between the end faces is close (RRKhan, HSDhadwal, and K. Suh, Applied Optics 33 (25), 1994). By using this light scattering measurement probe, the observation volume can be reduced and the problem of multiple scattering can be avoided.
[0004]
[Problems to be solved by the invention]
In the light scattering measurement probe, minute lenses (including graded index fibers) for focusing the optical fiber at a target position are arranged on the end face of the incident optical fiber and the end face of the light receiving fiber, respectively. For this reason, high accuracy is required for the positional relationship between the optical fiber and the lens, making it difficult to ensure quality as a practical product.
[0005]
Therefore, the present invention is easy to manufacture, accurate and reliable in a wide concentration range from a sample having a low particle concentration in the fluid (concentration of about 0.001%) to a sample having a high particle concentration (about 10% concentration). An object of the present invention is to realize a light scattering measurement probe capable of performing highly scattered light intensity measurement.
[0006]
[Means for Solving the Problems]
The light scattering measurement probe according to the present invention includes an incident optical fiber for propagating light irradiating a sample, and a scattered light measurement optical fiber for collecting and propagating the scattered light. In this case, an intermediate lens for collimating the light of the optical fiber is respectively installed on the end face of the scattered light measuring optical fiber and the end face of the incident optical fiber, and each of the collimated lights is set to the same condensing point. A single condensing lens is arranged for tying, and the end face of the optical fiber for scattered light measurement is arranged in the central part, and the end face of the optical fiber for incident light is in the peripheral part when viewed from the opening face of the light scattering measurement probe. A transparent plate is disposed on the opening surface, and a light absorbing member that absorbs the light that comes out of the incident optical fiber and reflects off the transparent plate is provided .
[0007]
According to the above configuration, the light emitted from the incident optical fiber is converted into parallel light by the intermediate lens and condensed by the condenser lens. The scattered light from this condensing point enters the optical fiber for measuring scattered light through the intermediate lens. Therefore, the scattered light can be measured by detecting the light of the scattered light measuring optical fiber.
Since the intermediate lens is for collimating the light of the optical fiber, strictness is not required for the front-rear position on the optical axis. Therefore, the adjustment at the time of optical arrangement is reduced, and the manufacturing becomes very simple.
[0008]
Scattering angle to be detected is the focal length of the condenser lens, so determined by the distance between the scattered light measurement optical fiber and the incident optical fiber, or use a different condenser lens focal length, between the optical fiber The scattering angle can be set to a desired angle by setting the distance. Further, since a light absorbing member that absorbs light reflected from the incident optical fiber and hits the transparent plate is provided, extra light (stray light) is present inside the light scattering measurement probe by this light absorbing member. Can be prevented.
The condensing point of the condensing lens is preferably located outside the aperture surface of the light scattering measurement probe. With this structure, the scattered light can be observed without the light scattering measurement probe touching the sample fluid.
[0009]
A transparent plate may be sealed and installed on the opening surface, and the condensing position of the condensing lens may be positioned outside the transparent plate. With this structure, the scattered light can be measured by immersing the light scattering measurement probe in the sample fluid.
The transparent plate may be configured to be movable so that the distance from the condenser lens can be changed. With this structure, even if the condensing lens is slightly deviated from the design time, the condensing position of the condensing lens can be set to a predetermined position outside the transparent plate by moving the transparent plate. it can.
[0010]
Before Symbol transparent plate, it is preferable that a portion not pass the light, and treated with an opaque color (Claim 5). This is because extra light (stray light) is absorbed inside the light scattering measurement probe.
[0011]
Optical fiber is preferably a single-mode optical fiber (claim 6). As a result, measurement can be performed under conditions with better coherence.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of a measurement system including a light scattering measurement probe 3. The light emitted from the laser device 1 is focused by the lens 2 and is incident on the incident optical fiber 4. The tip of the incident optical fiber 4 is coupled to the light scattering measurement probe 3. The light scattering measurement probe 3 is inserted into the cell 5 filled with the sample liquid h, and the sample is irradiated with laser light from the tip of the light scattering measurement probe 3.
[0013]
Scattered light from the sample is received at the tip of the light scattering measurement probe 3 and enters the light receiving element 7 such as a photomultiplier from the light scattering measurement probe 3 through the scattered light measuring optical fiber 6. Data is measured. Then, in a processing circuit (not shown), the autocorrelation coefficient of the data is calculated, and the particle size and the like are obtained.
The incident optical fiber 4 and the scattered light measuring optical fiber 6 are preferably single mode optical fibers from the viewpoint of maintaining the coherence of light.
[0014]
FIG. 2 shows a cross-sectional view (a) and a bottom view (b) of the light scattering measurement probe 3. The bottom view (b) is a bottom view when the condenser lens 38 and the transparent glass plate 39 are removed.
The light scattering measurement probe 3 has a cylindrical body part 31 and a tip part 32 coupled to the body part 31. The trunk portion 31 is inserted with the incident optical fiber 4 and the scattered light measuring optical fiber 6. Since the light scattering measurement probe 3 is immersed in the sample liquid h, the incident optical fiber 4 and the scattered light measurement optical fiber 6 are passed through the tube 33 in order to prevent the sample liquid h from entering. The tube 33 is inserted into the body 31 together. The joint between the tube 33 and the body 31 and the joint between the tip 32 and the transparent glass plate 39 are watertight with an adhesive. Further, the joint portion between the body portion 31 and the tip portion 32 is watertight by the packing 51.
[0015]
The distal end portion 32 is provided with light guide portions 34 and 35 that are optically coupled to the incident optical fiber 4 and the scattered light measurement optical fiber 6, respectively. Aspherical intermediate lenses 36 and 37 for converting the light of the optical fiber 4 and the scattered light measuring optical fiber 6 into parallel light are provided. Further, a condensing lens 38 that collects the parallel light converted by the aspherical intermediate lenses 36 and 37 at one focal point is provided. A transparent glass plate 39 that covers the open end of the distal end portion 32 is disposed just before the condensing position of the condensing lens 38. Reference numeral 41 denotes an absorption trap for reflected light. Specifically, the light guides 34 and 35 are made of a multimode optical fiber or a piece of a single mode optical fiber.
[0016]
FIG. 3 is a cross-sectional view showing a main part of the distal end portion 32. The focal point P of the condenser lens is set slightly ahead of the outer surface of the transparent glass plate 39 disposed at the opening end of the distal end portion 32. FIG. 4 is an enlarged view of the vicinity of the focal position.
Referring mainly to FIG. 4, the focal position P is set at a position d (d = 50 to 100 μm) away from the outer surface 39 a of the transparent glass plate 39. The cross-sectional area of the incident light i of the incident optical fiber 4 squeezed by the condensing lens 38 is the smallest at the focal position P, and the scattered light measuring optical fiber 6 converted into parallel rays by the condensing lens 38. The focal length or refracting power (power) of the condenser lens 38 is designed so that the cross-sectional area of the scattered light s becomes the smallest at the focal position P.
[0017]
The portion where the incident light i of the incident optical fiber 4 squeezed by the condensing lens 38 and the scattered light s of the scattered light measuring optical fiber 6 converted by the condensing lens cross is the scattering volume of the sample liquid h. V (part for measuring scattered light).
2 to 4, the incident light i of the incident optical fiber 4 squeezed by the condenser lens 38 is regularly reflected by the inner surface of the transparent glass plate 39. If this specularly reflected light is reflected many times inside the light scattering measurement probe 3 and enters the scattered light measurement optical fiber 6, it will adversely affect the scattered light measurement. Therefore, a reflected light absorption trap 41 is provided. Absorbs regular reflection light.
[0018]
Further, in order to absorb stray light inside the light scattering measurement probe 3, it is preferable that a light absorption process by etching or the like is applied to the transparent glass plate 39 other than the light i, s and r transmitting portions. The hatched lines in FIG. 5 indicate the etched portions of the transparent glass plate 39 that have been subjected to the light absorption process.
When the light scattering measurement probe 3 having the above configuration is immersed in the sample liquid h and laser light is incident on the incident optical fiber 4, scattered light is emitted through the scattered light measuring optical fiber 6. This scattered light can be detected by the light receiving element 7. Since the scattering volume can be made very small, it is possible to prevent a decrease in measurement accuracy due to multiple scattering.
[0019]
FIG. 6 shows a cross-sectional view (a) and a bottom view (b) of a light scattering measurement probe 3A according to a modified example.
The light scattering measurement probe 3A is characterized in that the distal end portion 32 includes a first housing 32a on which light guide portions 34 and 35, aspherical intermediate lenses 36 and 37, and a condensing lens 38 are mounted, and a transparent glass plate 39. It is divided into the mounted second casing 32b. The first housing 32a is formed with a male screw, and the second housing 32b is formed with a female screw so that they can be fitted to each other. Depending on the position of this screw, the transparent glass plate 39 moves back and forth relative to the first housing 32a. Therefore, the focal position P can be adjusted to be an arbitrary distance from the transparent glass plate 39.
[0020]
The merit of this structure is that the focal position P can be accurately set at a predetermined distance from the transparent glass plate 39. The manufacturer of the light scattering measurement probe 3A accurately sets the focal position P before shipment (after setting, the first casing 32a and the second casing 32b are fixed by adhesion), and the shipment is performed. can do.
FIG. 7 shows a cross-sectional view (a) and a bottom view (b) of a light scattering measurement probe 3B according to another modification.
[0021]
A feature of the light scattering measurement probe 3B is that a transparent glass plate is not attached to the opening surface of the distal end portion 32. Therefore, it is not a watertight structure. The condensing point of the condensing lens 38 is located outside the opening surface of the light scattering measurement probe.
Because of this structure, the entire light scattering measurement probe 3B cannot be immersed in the liquid, but can be measured without touching the surface of the sample liquid h, for example, as shown in FIG. Further, as shown in FIG. 8 (b), measurement can be performed from outside the transparent wall of the cell 5 filled with the sample liquid h.
[0022]
When such measurement is performed, since there is no glass plate, refraction and absorption of light by the glass plate can be avoided, and more sensitive scattered light measurement can be performed.
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.
[0023]
【The invention's effect】
As described above, according to the light scattering measurement probe of the present invention, it is possible to perform highly accurate and reliable scattered light intensity measurement in a wide concentration range of the sample fluid.
[Brief description of the drawings]
1 is an overall configuration diagram of a measurement system including a light scattering measurement probe 3. FIG.
2 is a cross-sectional view (a) and a bottom view (b) of a light scattering measurement probe 3. FIG.
FIG. 3 is a cross-sectional view showing a main part of a tip portion 32. FIG.
FIG. 4 is an enlarged view of the vicinity of a focal position of a tip portion 32. FIG.
FIG. 5 is a view showing a transparent glass plate 39 subjected to a light absorption process.
6A and 6B are a sectional view and a bottom view of a light scattering measurement probe 3A according to a modification of the present invention.
7A and 7B are a cross-sectional view and a bottom view of a light scattering measurement probe 3B according to another modification of the present invention.
FIG. 8 is a diagram showing how to use the light scattering measurement probe 3B.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser apparatus 2 Lens 3, 3A, 3B Light scattering measurement probe 4 Incident optical fiber 5 Cell 6 Scattered light measurement optical fiber 7 Light receiving element 31 Body part 32, 32a, 32b Tip part 33 Tube 34, 35 Light guide part 36 37 Aspherical intermediate lens 38 Condensing lens 39 Transparent glass plate 41 Absorption trap

Claims (6)

A light scattering measurement probe that performs light scattering measurement by irradiating a sample with light and detecting light scattered from within the scattering volume,
Inserting into the light scattering measurement probe an incident optical fiber for propagating the light irradiating the sample and a scattered light measuring optical fiber for collecting and propagating the scattered light,
In light scattering measurement in the probe, the end face and the end face of the incident optical fiber of the scattered light measuring optical fiber, we established an intermediate lens for collimating the light of the optical fiber, respectively, each of said collimated Install a single condenser lens to connect the light to the same focal point ,
When viewed from the opening surface of the light scattering measurement probe, the end surface of the scattered light measurement optical fiber is disposed at the center, and the end surface of the incident optical fiber is disposed at the periphery thereof,
A light scattering measurement probe comprising: a transparent plate disposed on the opening surface; and a light absorbing member that absorbs light that comes out of the incident optical fiber and reflects on the transparent plate .   The light scattering measurement probe according to claim 1, wherein a condensing point of the condensing lens is located outside an opening surface of the light scattering measurement probe. The light scattering measurement probe according to claim 1, wherein the transparent plate is hermetically installed on the opening surface, and a condensing position of the condensing lens is located outside the transparent plate. The transparent plate, as it is possible to change the distance from the condenser lens, the light scattering measurement probe according to claim 1, characterized in that it can move. Wherein the transparent plate, according to claim 1 light scattering measurement probe, wherein the portion does not pass through the light, and treated with an opaque color.   The light scattering measurement probe according to claim 1, wherein the optical fiber is a single mode optical fiber.

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