Grating photometer

#The present application claims priority of the Chinese Patent Application No. 200620014767.0, entitled “A Grating Photometer”, filed on Sep. 15, 2006, which is incorporated herein by reference in its entirety.

#The present invention relates to a gracing photometer, and specifically to an extinction structure for the grad photometer.

#A photometer is the key of a automatic biochemical analyzer, which is required to have high accuracy and wide linear range. In a photometric measurement system, the stray light is one of the main factors that influence accuracy and linearity of absorbance, so the stray light must be reduced to an extent small enough. In a grating dispersing optical system, the zero order spectrum corresponds to the ray whose order of spectrum is zero Since the zero order spectrum is non-dispersive, that is, it integrates the zero order spectral energy of all wavelengths the zero order spectral energy takes up a relatively large proportion of the total incident energy. This portion of ray whose order of spectrum is zero is reflected and scattered in the apparatus to form the stray light, therefore forming an interfering background at the position of detecting a spectral signal and reducing the signal-to-noise ratio and analytical sensitivity of the apparatus.

#FIG. 1 is a schematic diagram showing a optical system of a grating photometer;

#FIG. 2 is a structural diagram of a grating photometer according to an embodiment of the present invention;

#FIG. 3 shows a profile of the grating photometer according to all embodiment of the present invention.

#Referring to FIG. 1 to FIG. 3, a grating photometer according to an embodiment of the present invention comprises a light splitting box 14, a preamplifier box 19, a photodiode array 12 and are optical assembly. The light splitting box 14 is a sealed box including a light splitting chamber 16. The preamplifier box 19, also a sealed box, is mounted on a side wall of the light splitting chamber 16. The optical assembly is mounted in the light splitting box 14, and the photodiode array 12 is configured in the preamplifier box 19. The optical assembly comprises a light source 1, a first lens 2, an optic fiber bundle 3, a second lens 4, a cuvette 5, a third lens 6, an entrance slit 7, a diaphragm 8 and a concave, flat-field grating 9. The diaphragm 8 compares to form the light splitting chamber 16. The light emitted from the light source 1 is converged via the first lens 2 into the incident end of the optic fiber bundle 3, and, go though the exit end of the optic fiber bundle 3, then converged by the second lens 4, passes through the cuvette 5 and finally gets converged into the entrance slit 7 via the third lens 6. The light beam passing through the entrance slit 7 is restricted by the diaphragm 8 and incident on the concave, flat-field grating 9 which is provided in the light splitting chamber 16. The light beam is diffracted and converged by the grating 9, so the entrance slit is imaged on a slit array 11 behind a band-pass filter 10 (the slit array 11 is mounted in the preamplifier box 19). The detected spectrum is selected by each slit in the slit array 11 and received by the photodiode array 12 behind the slit array 11.

#As shown in FIGS. 3 and 4, there is provided a first emotion hole 141 at a place on the side wall of the light splitting chamber 16 which corresponds to the position of the zero order spectrum line, and a second exaction hole 191 at a place on the preamplifier box 19 which also corresponds to the position of the zero order spectrum line. The first extinction hole 141 is a through hole and the second extinction hole 191 is a blind hole. Additionally, there is provided a sealing gasket 18 between the preamplifier box 19 and the light splitting box 14. In the sealing gasket 18, there is also provided a through hole 181 which connects the first extinction hole 141 and the second extinction hole 191.

#In this embodiment, the first and second extinction holes 141 aid 191 may be circular, square or other shapes. The first extinction hole 141 may be coaxial or non-coaxial with the second extinction hole 191, as long as the zero order spectrum line can enter in them to obtain the same effect. Preferably, the first extinction hole 141 is not aligned with the second extinction bole 191, as shown in FIG. 4. Additionally, the aperture of the first extinction hole 141, the aperture of the second extinction hole 191 and the aperture of the through hole 181 on the sealing gasket may be same or different.