Field of the Invention and Related Art Statement
The present invention relates to an automatic analyzer comprising a reaction line along which a number of reaction vessels each containing respective test liquids are transported and photometering means for effecting the photometry for the test liquids in the reaction vessels by transmitting light beams through the reaction vessels.
An automatic analyzer of single-line and multi-item type has been proposed in which a plurality of test items, i.e. a plurality of substances in samples are analyzed by means of a single reaction line. In such an automatic analyzer, test liquids contained in reaction vessels have to be photometered with the aid of light beams having different wavelengths corresponding to respective test items.
FIG. 1 is a schematic view showing a known photometering apparatus disclosed in Japanese Patent Publication No. 65-21,303. The photometering apparatus comprises a light source 1 emitting white light, i.e. light including whole wavelength components, a condenser lens 2 for collecting the white light and making it incident upon reaction vessels 4 transported along a reaction line 3. Light transmitted through a test liquid contained in a reaction vessel 4 is made incident upon a spectroscope 6 via a slit 5 and is divided into a plurality of light beams having different wavelengths. These light beams are then made incident upon a plurality of light detectors 8-1, 8-2, . . . 8-n, respectively by means of a slit 7 having a plurality of holes 7a. One or more output signals supplied from the light detectors 8-1, 8-2, . . . 8-n are selected in accordance with test items to be measured for respective samples.
FIG. 2 is schematic view illustrating another known photometering apparatus described in Japanese Patent Laid-open Publication, Kokai Sho 60-117,118. In this known apparatus, white light emitted from a light source 11 is evenly made incident upon incident ends of a plurality of optical fibers 13 via a condenser lens 12. Exit ends of optical fibers 13 are secured at positions which are predetermined in accordance with wavelengths of measuring light beams emanating from a diffraction grating 14. In opposition to the exit ends of optical fibers 13 there is arranged a rotary disc 19 which is rotated by a motor 17. As shown in FIG. 3, the rotary disc 19 has formed therein a plurality of sector slits 18 corresponding to the positions at which the exit ends of optical fibers 13 are arranged. The motor 17 is driven such that any one of slits 18 in the disc 19 can be positioned opposite an exit end of an optical fiber in accordance with a test item destined for a test liquid contained in a reaction vessel 16 which is just indexed at a measuring position defined by slit 20. Therefore, a light beam having a desired wavelength is made incident upon the reaction vessel 16 from the diffraction grating 14, and the light transmitted through the reaction vessel is received by a light detector 21. The reaction vessels 16 are transported along a reaction line 15 through the measuring position.
In the known photometering apparatus illustrated in FIG. 1, since the white light has a large amount of energy and is made incident upon the test liquid, some substances in test liquids might be decomposed or altered, so that in practice it is difficult to carry out the measurement precisely.
This problem could be removed by the known apparatus illustrated in FIG. 2, because only a slight flux having a desired wavelength corresponding to a test item is made incident upon a test liquid. However, in this known apparatus, in order to select the wavelength it is necessary to rotate the slit disc 19, and therefore a long time period may be necessary for measuring test items, thereby reducing the processing ability of such systems. Moreover, the white light emitted from the light source 11 is divided into a plurality of light beams with the aid of the optical fibers and thus weaking the intensity of respective light beams. And as a result, noise can affect the weakened photometered signals thus decreasing the accuracy of the photometry.
U.S. Pat. No. 4,528,159, issued on July 9, 1985, discloses another known automatic analyzer comprising a light source emitting white light, first and second filter wheels arranged rotatably, and first and second light guides arranged between a cuvette and the filter wheels, respectively. Light emitted from the light source is evenly made incident upon filter elements of the first filter wheel, and a light flux emanating from a filter element is made incident upon a cuvette containing a test liquid via the first light guide. A light flux transmitted through the cuvette is made incident upon a light detector by means of the second light guide and a filter element of the second filter wheel. This known photometering apparatus is principally the same as the known apparatus shown in FIG. 2, and thus it requires a rather long time period to rotate the first and second filter wheels so as to index desired filter elements thereof into the measuring optical path in accordance with a test item to be measured.