| 摘要 |
PROBLEM TO BE SOLVED: To ensure precision without using high gradation DAC in the case of Ref adjustment, by performing correction to component irregularity and its fluctuation with time of an illumination light source, a reference white plate, etc., by reference (Ref) adjustment of an ADC without using a variable gain amplifier. SOLUTION: The reference white plate and an original document of reference concentration in the initial state like the plant delivery are read with the same Ref after Ref adjustment of DAC 36 setting a peak valueαas a target, and both output peak levelsα2,β2 are preserved. In the case of normal usage, correction corresponding to change with time is performed. As to the Ref adjustment of only the reference white plate, adjustment is performed to obtain the initial peak levelα2, and a set value RefV2' at this time is obtained. In the case of actual reading, the reference white plate and the original document are read with RefV2', and the respective data are produced. But the original document is multiplied by a coefficientα2/β2, and a mutual relation between level values of the reference white plate and the reference concentration original document in the initial adjustment is reflected.
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