JPH0357432A - Semiconductor laser blood flow meter - Google Patents

Abstract

PURPOSE:To eliminate random mode-pop generated by a reflected return light generated by an optical part such as a contact interface, etc., by superposing an AC electric output having other frequency than a measuring frequency band to electric energy supplied to a semiconductor laser output means. CONSTITUTION:By superposing an AC current to a driving current for generating a semiconductor laser, and swinging small periodically the mode, a random noise is eliminated. That is, this light periodical mode-pop averages by offsetting an effective reflected return light generated in the end of a fiber, therefore, spectral width of an output of a source semiconductor laser can be maintained. A DC power source 1 is connected to a semiconductor laser output means 3, and an AC power source 2 is connected to the semiconductor laser output means 3 through a switch. The semiconductor laser output means 3 is constituted of a semiconductor laser and a condensing unit, etc., and connected to a light sending fiber 4 for transmitting a condensed semiconductor laser to the part to be examined.

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 a fiber using a lens, reflected light from one end of the fiber returns to the semiconductor laser light source, causing 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, an object of the present invention is to eliminate random mode hops caused by reflected return light that occurs at an optical site such as a fiber provided at a subsequent stage or a contact interface with a fiber.

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 either single, as shown in Figure 3 (a), or it is unstable, or when the temperature changes (or return). When there is light, the oscillation modes (period, wavelength, etc.) jump randomly.

(See FIG. 3(b)) The present invention is to eliminate random noise by superimposing an alternating current on a drive current for generating a semiconductor laser, and periodically oscillating a small mode.

That is, this light periodic mode hop offsets and averages the effective reflected return light generated at one end of the fiber, so that the spectral width of the source semiconductor laser output can be maintained.

In the present invention, 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 using AC weight. (See FIG. 3(C)) This alternating current has a frequency outside the measurement frequency band consisting of the semiconductor laser output frequency and the beat frequency, preferably higher than this, but is not particularly limited.

Examples of the present invention will now be described.

In Figure 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).
) is connected to the semiconductor laser output means (3).

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

(5) is a light-receiving fiber for transmitting the semiconductor laser light returned from the test site to the blood flow meter (6) for measuring actual blood flow volume, speed, 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 (lO) 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.

(22) is a lens, and semiconductor laser light source (21)
The laser beam output from the semiconductor laser is focused.

(23) is the ferrule on the laser beam incidence side, and the main body (
201) is a fiber holding component for holding the optical fiber (24). Ferrule (23) and lens (
22) A condensing path (29) was provided between them, and a polarizing plate (28) was placed in the middle.

(25) is a ferrule on the laser output side, which is a fiber holding part for connecting the semiconductor laser light transmitted through the optical fiber (24) to other optical equipment, or for connecting the semiconductor laser light to an object to be measured such as a living body. The irradiation port component (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 the lens (22), enters the fiber (24) held at an angle by the ferrule (23), and enters the fiber (24) held at an angle by the ferrule (23). It is emitted from a fiber held by a ferrule.

When focusing on the fiber held by this ferrule (23), Ichiro is reflected, but the ferrule (23)
3) has an angle (9°) with respect to the optical axis, so it is difficult to return to a semiconductor laser.

Return light passing through the (l mode) from the fiber in the filter (25) is also difficult to enter the semiconductor laser.

Laser output side ferrule (25), fiber (24)
) can also take the shape shown in FIG. In other words, the tip of the fiber (24) is processed to form an angle. The end of the normal fiber (24) has a vertical cross section as shown by the broken line, but it is processed to form an angle of about 8 degrees.

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

In Figure 1, a light transmitting ferrule (10) is added to a latex liquid (7) containing a latex liquid (8).
and insert the light receiving ferrule (11).

First, the fluctuation of blood flow is measured with the switch (9) open, and then the fluctuation of blood flow is measured with the switch (9) closed.

FIG. 2 is a graph in which the vertical axis represents the degree of fluctuation and the horizontal axis represents time {IA. At time IJ (2A), the switch (9) was closed.

The frequency of AC is 150kHz, l/10 compared to 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 eliminated by superimposing alternating current electricity, and there are effects such as accurate blood flow measurement.

[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. 4 and 5 are diagrams showing a light condensing unit in an embodiment of the present invention. DC power supply, AC power supply, semiconductor laser output means, fiber blood flow meter for light transmission and reception, latex bath, liquid.

Claims (1)

[Claims] (1) Semiconductor laser output means, a focusing unit for condensing the semiconductor laser output light of the semiconductor laser output means, a power source for supplying electrical energy to the semiconductor laser output means, and electricity supplied to the semiconductor laser output means A semiconductor laser blood flow meter comprising a superimposing means for superimposing alternating current electrical output having a frequency outside the measurement frequency band on energy.