A fiber optic device for measuring liquids which are drawn into an end of the device to a predetermined distance from the end of the optical fibers

The first branch 1a of the optical fiber 1 is connected to the light source 2, and the second branch 1b is connected to the optical measuring unit 3. A taper-shaped tip member 8 is fitted to a tip end of the optical fiber unit 1 with the use of a jig member 4. The inner hollow space 7 in the tip member 8 is connected with the air suction device 11, through the gap 5 formed between the optical fiber unit 1 and the jig member 4 and the air suction tube 10. The air suction device 11 discharges air from the inner hollow space 7 to suck liquid through the through-hole 6 into the inner hollow space. The air suction device 11 is controlled by the controller 12. Because the optical fiber unit can directly irradiate liquid with light, measurement can be performed with high sensitivity. The optical fiber unit is prevented from contamination.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for measuring optical 
characteristics of various kinds of liquid analyte with the use of an 
optical fiber. This device can measure the amount of light absorbed or 
scattered by a liquid analyte and can measure the amount of light 
fluorescently or chemically emitted from the liquid. 
2. Description of the Related Art 
Conventionally, there are two methods for measuring, with the use of an 
optical fiber, the amount of light fluorescently or chemically emitted 
from a liquid analyte. In one method, one end of the optical fiber is 
immersed directly into a liquid held in a vessel so as to irradiate the 
liquid with detection light. In the other method, an optically transparent 
container is additionally provided. A liquid analyte from the vessel is 
first transferred to the optically transparent container and then 
irradiated with detection light through the transparent wall of the 
container. 
In the first method, the optical fiber is contaminated by the liquid. 
Although the second method eliminates contamination of the optical fiber, 
measurements are insufficiently accurate. Because the optical fiber is 
separated from the liquid by the thickness of the container wall, less 
light reaches the optical fiber, thereby lowering efficiency at which 
light is picked up. 
SUMMARY OF THE INVENTION 
It is therefore, an object of the present invention to overcome the 
above-described drawbacks, and to provide a device that can directly 
irradiate liquid with light from an optical fiber and directly pick up 
light from the liquid by the optical fiber to enhance measurement accuracy 
while preventing the optical fiber from being contaminated with the 
liquid. 
In order to attain the object and other objects, the present invention 
provides a device for measuring optical characteristics of liquid, 
comprising: an optical fiber unit having a detection end and a first end 
opposed to each other; a tip member mounted on the detection end of the 
optical fiber unit for being immersed into liquid to be detected, the tip 
member having a wall defining an inner hollow space, into which the 
detecting end of the optical fiber unit being exposed, and defining a 
through-hole communicated with the inner hollow space; an air suction unit 
connected with the inner hollow space of the tip member for discharging 
air out of the inner hollow space, to thereby suck a proper amount of the 
liquid through the through-hole into the inner hollow space, the optical 
fiber unit receiving, at the detecting end, light emitted from the liquid 
thus held in the inner hollow space and guiding the light from the 
detecting end toward the first end; and an optically-measuring unit 
connected to the first end of the optical fiber unit for receiving the 
light guided to the first end and for measuring the light, to thereby 
measure optical characteristics of the liquid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
A device for optically measuring liquids according to a preferred 
embodiment of the present invention will be described while referring to 
the accompanying drawings wherein like parts and components are designated 
by the same reference numerals as those shown in FIGS. 1 and 2 to avoid 
duplicating description. 
The device 100 for optically measuring liquids of the embodiment includes 
an optical fiber unit 1 constructed from a pair of optical fibers. Each of 
the optical fibers has a diameter in the range of 3 mm.phi. and 7 mm.phi.. 
The two optical fibers are connected along end sections to form a Y-shaped 
unit consisting of a trunk portion 1c and a first and second branch 
portions 1a and 1b. The trunk portion 1c is formed from the connected 
lengths of the two optical fibers. A detection end 15 forms the tip of the 
trunk portion 1c opposite the fork of the Y shape. The first and second 
branch portions 1a and 1b are formed from the unconnected lengths of the 
optical fibers. The first branch portion 1a is connected to a light source 
2, such as a xenon lamp and a halogen lamp. The light source 2 is for 
emitting excitation light of wavelength in the range of 250 nm and 1800 
nm. The second branch portion 1b is connected to an optical measuring unit 
3, such as a photon counter and a photon multi-channel analyzer. The 
optical measuring unit 3 is for measuring the amount of scintillation 
light emitted from liquid analyte upon excited with the excitation light, 
as will be described later. 
A tubular jig 4 is provided mounted on the trunk portion 1c so that a gap 5 
is produced between the narrower outer periphery of the trunk portion 1c 
and the larger inner periphery of the tubular jig 4. The jig 4 is fixedly 
secured to the trunk portion 1c. The end of the jig 4 near the detection 
end 15 of the trunk portion 1c is tapered, thereby forming a tapered 
portion 4a. 
A tip member 8 is fitted to the tubular jig 4. The tip member 8 has a 
tapered wall 8a enclosing an inner hollow space 7. A tip end of the 
tapered wall 8a is formed with a through-hole 6 in communication with the 
inner hollow space 7. The tip member 8 is securely fitted to the jig 4 in 
such a manner that the tapered wall 8a is adhered to the tapered portion 
4a. This configuration leaves the detection end 15 of the optical fiber 
unit 1 exposed in the inner hollow space 7. 
The tubular jig 4 has a through-hole 4b at a predetermined position on the 
peripheral wall. One end 10a of an air suction tube 10 is fitted to the 
through-hole 4b so as to be fluid communication with the gap 5. An air 
suction device 11 such as an air discharge pump is connected to the other 
end of the air suction tube 10. 
A controller 12 such as a microcomputer is connected to the air suction 
device 11 for driving the air suction device 11. The controller 12 
controls air suction volume, air suction speed, and timing at which the 
air suction starts and stops. The controller 12 is connected also to the 
optical measuring unit 3 for receiving measured results and for 
calculating optical characteristics of the liquid analyte based on the 
measured results. 
To measure optical characteristics of liquid analyte with the device 100 
constructed as described above, the jig member 4 is located upright in a 
vessel, in which liquid analyte is held, so that the tip end of the 
cone-shaped tip member 8 faces downwardly. In this condition, the 
detecting end 15 is positioned above the through-hole 6. Then, the tip 
member 8 is immersed in the liquid, until the through-hole 6 nearly 
contacts the surface of the liquid. 
Then, the controller 12 starts driving the air suction device 11 to 
discharge or draw air from the inner hollow space 7 through the Gap 5 and 
the air suction tube 10. This produces a negative pressure inside the 
inner hollow space 7, which in turn sucks, through the through-hole 6, an 
amount of liquid 13 required for measurement. The controller 12 controls 
the air suction device 11 to suck an amount of air at a speed sufficient 
to raise the level 14 of the liquid 13 in the inner hollow space 7 until 
quite close to but not in contact with the surface of the detection end 
15. For example, controlling the air suction amount in a range of 100 
.mu.L to 1 mL and the air suction speed of 0.1 mL per seconds can suck the 
liquid 13 until its surface 14 reaches the level lower than the detection 
end 15 by a distance L of about 3.0 mm or less. 
Although not shown in the drawings, a liquid level sensor may be 
additionally provided in the inner hollow space 7. The liquid level sensor 
is for outputting a signal indicative of the level of liquid sucked into 
the inner hollow space 7. The controller 12 can regulate drive of the air 
suction device 11 based on the signal. 
When the liquid is properly sucked into the tip member 8, the light source 
2 starts emitting excitation light. The excitation light is guided by the 
first branch portion 1a and the trunk portion 1c to be radiated from the 
detection end 15 onto the liquid 13 held in the tip member 8. The liquid 
13 emits scintillation light when excited with the excitation light. The 
scintillation light is then received by the detection end 15. The 
scintillation light is guided by the trunk portion 1c and the second 
branch portion 1b. The optical measuring unit 3 receives the scintillation 
light emitted from the end of the branch portion 1b. 
It is noted that the detecting end 15 receives not only the scintillation 
light but also some amounts of excitation light that is reflected from and 
scattered by the liquid 13. The measuring unit 3 includes a wavelength 
selector, such as an interference filter and a spectrometer, for 
separating the scintillation light from the excitation light. In the 
optical measuring unit 3, therefore, the scintillation light is separated 
from the excitation light before being measured. Thus, only the desired 
information on the scintillation light emitted from the liquid 13 is 
obtained. 
The controller 12 automatically controls the above-described series steps 
of operation: the liquid sucking step; the excitation light irradiating 
step; and the scintillation light measuring step. Simultaneously with 
these operations, the controller 12 displays and records the measured 
results. 
As described above, according to the present invention, the level 14 of the 
liquid 13 can be finely adjusted very close to but not in contact with the 
detecting end 15 of the optical fiber unit. It is therefore possible to 
reliably detect scintillation light emitted from the liquid with high 
sensitivity while preventing the optical fiber unit from being 
contaminated by the liquid analyte. 
While the invention has been described in detail with reference to the 
specific embodiment thereof, it would be apparent to those skilled in the 
art that various changes and modifications may be made therein without 
departing from the spirit of the invention. 
For example, in the above-described embodiment, the gap 5 for sucking the 
liquid into the inner hollow space 7 is formed between the outer periphery 
of the optical fiber unit 1 and the inner periphery of the tubular jig 4. 
However, the gap may be formed by other various methods. For example, the 
optical fiber unit 1 may be made from a bundle of a plurality of optical 
fibers. The gaps formed between the plurality of optical fibers may be 
used for sucking the liquid into the inner hollow space 7. Alternatively, 
the air suction tube 10 may be directly connected to the inner hollow 
space 7. In this case, the gap 5 may be omitted. 
In the present embodiment, the wavelength of the scintillation light is 
selected in the measuring unit 3. By also selecting the wavelength of the 
excitation light, the excitation light can be separated from the 
scintillation light to be measured by the optical measuring unit 3. In 
this case, the device of the present invention serves as a turbidimeter. 
As described above, according to the present invention, the tip member is 
immersed in a liquid analyte. The air suction unit is driven to discharge 
air out of the inner hollow space of the tip member, thereby sucking 
liquid into the tip member through the through-hole. Driving of the air 
suction unit stops when the surface level of the liquid in the inner 
hollow space of the tip member reaches a position that is apart from the 
surface of the detecting end of the optical fiber with a predetermined 
small distance. Then, the liquid thus held in the tip member is optically 
detected by the detecting end of the optical fiber. 
Thus, the optical fiber can directly irradiate the liquid with the 
excitation light and also can directly pick up light emitted from the 
liquid as excited with the excitation light. The optical fiber can 
therefore high-efficiently pick up light emitted from the liquid to 
thereby detect the light with high sensitivity. Because the end surface of 
the optical fiber unit is located very close to but not in contact with 
the liquid level, the optical fiber can be prevented from being 
contaminated by the liquid. Drawing or discharging air from the inner 
hollow space of the tip member, which is fitted to the tip end of the 
optical fiber unit, can easily perform fine adjustment of the distance or 
gap between the level of the liquid sucked into the inner hollow space and 
the detecting end surface of the optical fiber. When desiring to promote 
reaction in the liquid for measuring a predetermined substance contained 
in the liquid, control of the liquid sucking speed can attain an optimum 
condition for the promotion.