Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1990-03-26
1992-05-12
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250575, G01N 1506
Patent
active
051130831
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a light scattering measuring apparatus for measuring, at an arbitrary scattering angle, the Doppler shift of the scattered light from a sample.
BACKGROUND OF THE INVENTION
The light scattering measuring apparatus is used as an optical measuring apparatus in which a laser light is irradiated to colloid particles in a fluid, blood corpuscles in blood or the like and the Doppler shift of the scattered light is observed, thereby to measure the moving velocity of the particles.
As the light scattering measuring apparatus of the type above-mentioned, a heterodyne-type light scattering measuring apparatus is widely used in which the scattering light is heterodyne-detected with the use of a reference light obtained by splitting light from the same light source, so that the frequency distribution of the scattered light is detected with precision.
In the heterodyne-type light scattering measuring apparatus, it is preferable to make a provision such that the light scattering measuring angle is continuously changed. This is because, in such an arrangement, particles having a variety of sizes may be efficiently measured and the velocity distribution of particles having a size distribution may be measured according to the scattering angle. Accordingly, a variety of light scattering measuring apparatus of this type have been proposed.
For example, there has been proposed (1) apparatus, as shown in FIG. 6, in which the incident light LD and the reference light LR parallel thereto are formed from a laser beam L with the use of a half-mirror BS and a reflecting mirror P, and both lights are incident upon a large-diameter convex lens LE, and the scattering light LS from a sample S at the focal position F of the convex lens LE is measured together with the reference light LR (E. E. Uzgiris, D. H. Cluxton, Rev. Sci. Instrum, 51 (1), Jan. 1980).
In the light scattering measuring apparatus above-mentioned, the Doppler shift may be observed according to the heterodyne method. However, to change the scattering angle .theta., it is required to adjust the incident position of the reference light LR with the use of the general nature that the refraction angle of light incident upon a convex lens becomes greater as the incident point is separated away from the center of the convex lens. It is therefore necessary to move the reflecting mirror P to change the distance X between the direct light LD and the reference light LR. In addition to such a movement of the reflecting mirror P, the rotation of the position of a photodetector DET for receiving the scattering light LS, around the focal point F of the lens LE is also required.
However, even though the reflecting mirror P is moved, the scattering angle .theta. cannot be directly measure since the optical path is not visual. Accordingly, the scattering angle .theta. may be merely presumed based on a calculating equation representing the relationship between the distance X and the scattering angle .theta., or based on the angle at which the light intensity at the photodetector DET is maximized, or the like. This involves the likelihood that an error will be introduced. Further, since the reference light LR passes through the sample, the noise component in the signal is increased. This makes it difficult to measure small-diameter particles of which scattering intensity is small. Thus, the resolution is disadvantageously deteriorated.
There has been also proposed an apparatus, as shown in FIG. 7, in which only the incident light LD is incident upon a sample S through a convex lens LE1, and the resultant scattering light LS is united, at a half-mirror BS, with the reference light LR guided from another optical path, and the heterodyned light is incident upon a photodetector DET, where measurement is carried out. According to this arrangement, measurement similar to that achieved in the apparatus shown in FIG. 6 may be made by integrally moving the sample S and the lenses LE1, LE2 along a direction A. However, it is also difficult,
REFERENCES:
patent: 3732014 (1973-05-01), Urgiris
patent: 4242194 (1980-12-01), Steiner et al.
patent: 4466738 (1984-08-01), Huang et al.
patent: 4611916 (1986-09-01), Yoshizumi
patent: 4990791 (1991-02-01), Nishi
Akagi Motonobu
Kubo Yasuhiro
Oka Koichi
Otani William
Zasu Yasushi
Davenport T.
Nelms David C.
Otsuka Electronics Co., Ltd.
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