JPH0556898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blood flow meter using semiconductor laser light.

When a semiconductor laser light source enters the fiber using a lens, reflected light from the end face of the fiber returns to the semiconductor laser light source, creating random mode hops.

Therefore, since the spectrum of the semiconductor laser light, which is a reference for blood flow measurement, changes discretely, the blood flow measurement value fluctuates greatly, making measurement impossible.

In view of the above, it is an object of the present invention to eliminate random mode hops caused by anti-upward return light generated at optical sites such as fibers provided at a later stage and contact interfaces with fibers.

The features of the present invention are as follows.

When the semiconductor laser is stable (constant temperature, no return light, constant output), the oscillation mode is single as shown in Figure 3a, but in an unstable state,
When the temperature changes or return light hits, the oscillation mode (period, wavelength, etc.) changes randomly. (See FIG. 3b) The present invention is to eliminate random noise by superimposing an alternating current on the drive current for generating a semiconductor laser, and periodically oscillating a small mode.

That is, these light periodic mode hops offset and average out the effective reflected return light generated at the fiber end, thereby maintaining the spectral width of the source semiconductor laser output.

Unlike the conventional example, in which a pulsed laser instantaneously becomes multi-mode, the present invention instantaneously generates a single mode at intervals of 150 kHz by alternating current superposition. (See Figure 3c) This alternating current has a frequency that is outside the measurement frequency band consisting of the semiconductor laser output frequency and the beat frequency, preferably higher than this.
It is not particularly limited.

Examples of the present invention will now be described.

In FIG. 1, a DC power source 1 is connected to a semiconductor laser output means 3, and an AC power source 2 is connected to a switch 9.
It is connected to the semiconductor laser output means 3 via.

The semiconductor laser output means 3 is composed of a semiconductor laser, a condensing unit, etc., and is connected to a light transmitting fiber 4 for transmitting the condensed semiconductor laser to the test site.

Reference numeral 5 denotes a light-receiving fiber for transmitting the semiconductor laser light returned from the test site to a blood flow meter 6 that obtains actual blood flow volume, velocity, etc.

In this embodiment, the light transmitting fiber 4 and the light receiving fiber 5 will be explained separately, but they may be integrated.

A light transmitting ferrule 10 is formed at the light transmitting end of the light transmitting fiber 4, and a light receiving ferrule 11 is formed at the light receiving end of the light receiving fiber 5.

Further, in the present invention, it is used in combination with a condensing unit shown in FIG.

The structure and operation of the condensing unit will be explained below.

In FIG. 4, 21 is a semiconductor laser light source, which is composed of a semiconductor laser or the like. 2
Reference numeral 2 denotes a lens, which focuses the semiconductor laser light output from the semiconductor laser light source 21.

Reference numeral 23 denotes a laser beam incident side ferrule, which is a fiber holding component for holding the optical fiber 24 in the main body 201. A condensing path 29 was provided between the ferrule 23 and the lens 22, and a polarizing plate 28 was placed in the middle.

25 is a laser emission side ferrule, which is a fiber holding part for connecting the semiconductor laser light transmitted through the optical fiber 24 to other optical equipment, or an irradiation device for irradiating the semiconductor laser light onto an object to be measured such as a living body. It is also a mouth part.

27 is a DC power supply that supplies electrical energy to irradiate the semiconductor laser from the semiconductor laser light source.

The ferrule 23 is fixed to the main body 201 at an angle of about 9° to the optical axis, and the length of the light collecting path 29 is about 60 mm.

Next, the operation of this embodiment will be explained in detail with reference to the drawings.

The semiconductor laser light emitted from the semiconductor laser light source 21 is focused by a lens 22, enters a fiber 24 held at an angle by a ferrule 23, and is emitted from a fiber held by a ferrule 25. It is emitted.

When the light is focused on the fiber held by the ferrule 23, a portion of the light is reflected, but since the ferrule 23 has an angle (9°) with respect to the optical axis, it is difficult to return to the semiconductor laser.

Return light from the fiber in the ferrule 25 through the low-order mode is also difficult to enter the semiconductor laser.

Laser output side ferrule 25, fiber 2
4 may also take the shape shown in FIG. That is, the tip of the fiber 24 is processed to form an angle. The end face of the fiber 24 normally has a vertical cross section as shown by the broken line, but it is machined to form an angle of about 8°.

EXAMPLE Next, the Brownian motion of latex particles was measured using the present invention.

In FIG. 1, a liquid 8 containing latex particles is shown.
The light transmitting ferrule 1 is placed in the latex tank 7 into which the
0 and the light receiving ferrule 11 are inserted.

First, fluctuations in blood flow are measured with switch 9 open, and then fluctuations in blood flow are measured with switch 9 closed.

FIG. 2 is a graph in which the vertical axis represents the degree of fluctuation and the horizontal axis represents time. In time (2A),
Switch 9 was closed.

The frequency of AC is 150kHz, 1/10 of that of DC.
The voltage was . It is clear that the fluctuation almost disappears after time (2A).

Note that FIG. 1 is one embodiment, and any structure may be used as long as it can supply alternating current power to the semiconductor laser supply power source.

As described in detail above, random mode hops caused by reflected return light can be removed by superimposing alternating current electricity, and this has the effect of making it possible to accurately measure blood flow.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a graph showing the results of an experiment conducted using the embodiment shown in FIG. 1, and FIG. 3 is a diagram showing the operation of the present invention. The figures shown in FIGS. 4 and 5 are views showing a condensing unit in an embodiment of the present invention. 1... DC power supply, 2... AC power supply, 3... semiconductor laser output means, 4... light transmission fiber,
5...Light receiving fiber, 6...Blood flow meter, 7...
Latex tank, 8...liquid.

Claims (1)

[Claims] 1. A semiconductor laser output means, a condensing unit for condensing the semiconductor laser output light of the semiconductor laser output means, a power supply for supplying electric energy to the semiconductor laser output means, and an electric energy supplied to the semiconductor laser output means. On the other hand, the irradiation member includes a superimposing means for superimposing an AC electrical output having a frequency outside the measurement frequency band, an irradiation member for transmitting the laser light focused by the focusing unit and irradiating the object to be measured, and the irradiation member. A part or all of the contact interfaces of the respective constituent parts, the contact interfaces of the irradiation member and the condensing unit, and the irradiation interfaces of the irradiation member have a predetermined angle with respect to the optical axis. A semiconductor laser blood flow meter.