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Biochemical analyzer is one of the important instruments in the clinical diagnosis, and its optical system is the important
component. The operation of this optical system can be regard as three parts. The first is transforms the duplicate colored
light as the monochromatic light. The second is transforms the light signal of the monochromatic, which have the
information of the measured sample, as the electric signal by use the photoelectric detector. And the last is to send the
signal to data processing system by use the control system. Generally, there are three types monochromators: prism,
optical grating and narrow-band pass filter. Thereinto, the narrow-band pass filter were widely used in the semi-auto
biochemical analyzer. Through analysed the principle of biochemical analyzer base on the narrow-band pass filter, we
known that the optical has three features. The first is the optical path of the optical system is a non- imaging system. The
second, this system is wide spectrum region that contain visible light and ultraviolet spectrum. The third, this is a little
aperture and little field monochromatic light system. Therefore, design idea of this optical system is: (1) luminous energy
in the system less transmission loss; (2) detector coupled to the luminous energy efficient; mainly correct spherical
aberration. Practice showed the point of Image quality evaluation: (1) dispersion circle diameter equal the receiving
device pixel effective width of 125%, and the energy distribution should point target of 80% of energy into the receiving
device pixel width of the effective diameter in this dispersion circle; (2) With MTF evaluation, the requirements in 20lp/
mm spatial frequency, the MTF values should not be lower than 0.6. The optical system should be fit in with ultraviolet
and visible light width spectrum, and the detector image plane can but suited the majority visible light spectrum when by
defocus optimization, and the image plane of violet and ultraviolet excursion quite large. Traditional biochemical
analyzer optical design not fully consider this point, the authors introduce a effective image plane compensation measure
innovatively, it greatly increased the reception efficiency of the violet and ultraviolet.
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