(i) Field of the Invention
The present invention relates to a method for analyzing data by an on-line near infrared spectral analyzer.
(ii) Description of the Related Art
As a manufacturing process management, there are an off-line management and an on-line management. In the off-line management, a specimen sampled from a manufacturing line is sent to an analyzing room which is away from the line, its characteristic value is analyzed, and the result is fed back to the line. In the analysis, a chemical analysis is performed in many cases, so that it takes a long time for the analysis. In the on-line management, a specimen sampled by an automatic sampler is automatically sent to an analytical instrument and is automatically analyzed. An analytical result is fed back to the line.
In recent years, a technique for a non-destructive inspection using a near infrared spectroscopy has progressed and is used to analyze protein or starch of food or feed. Consequently, time and costs are sharply reduced as compared with a conventional chemical analysis. As for an object to be measured as well, not only chemical characteristics but also physical characteristics can be measured. Although the near infrared spectroscopy or an infrared spectroscopy is used in the on-line analysis in few cases so far, as effects of a laboratory analysis become more apparent, needs of the on-line analysis are being raised.
In the near infrared spectroscopy, an object to be measured is analyzed by a chemical means or a physical means to make its characteristic value clear, a spectrum of the same object to be measured is obtained by a laboratory near infrared spectral analyzer, and a calibration indicative of a relation between the spectrum and the characteristic value is formed. The spectrum of the next target to be measured is measured by the laboratory near infrared spectral analyzer and the characteristic value of the object to be measured is estimated from the spectrum and the calibration. In order to form the calibration, works such as chemical analysis and clarification of physical characteristics of a large quantity of objects to be measured are needed.
When the on-line analysis is performed by the near infrared spectroscopy, the calibration formed by the laboratory near infrared spectral analyzer cannot be used as it is. Hitherto, since the structure of the spectral analyzer is complicated, even in case of the spectral analyzers having the same structure, the sampling measurement is performed by each spectral analyzer and the calibration is obtained by each spectral analyzer. Particularly, an optical fiber is used in a near infrared spectral analyzer for on-line in many cases. Since the optical fiber is not used in the near infrared spectral analyzer for laboratory (for off-line) in most of cases, however, a difference in spectral characteristics occurs. In an optical system using a diffraction grating for laboratory, dispersed light is irradiated onto an object. However, in the system for on-line, white light is irradiated onto a sample and there is a case where transmission light or reflection light is dispersed by the diffraction grating. It is impossible to transfer or share the calibration between the spectral analyzers having different structures as mentioned above, so that it is considered that the on-line analysis is difficult.