SPECTROPHOTOMETER

PURPOSE:To enable the calibration and inspection of equipment based on the intensity of a sample light at absolute 0 by getting the order and combination of taking out the sample light, reference light and a dark specified. CONSTITUTION:The output of a detector 8 such as thermocouple is applied to a signal component separation circuit 11 as amplified and separated into a frequency (f) corresponding to one cycle of an optical path switching means and a frequency 2f doubling it with BPFs 12 and 13. A signal proportional to the intensity I of sample lights and a signal proportional to the intensity I0 of reference light are obtained from a component synchronous rectification circuits 15 and 16 and applied to a ratio computation circuit 19, which outputs a signal corresponding to I/I0. The component of a fundamental frequency (f) is a function of the sample light I alone, hence irrelevant to the intensity I0 of the reference light. In other words, when the intensity I of the sample light is 0, the component of the fundamental frequency (f) is 0. Therefore, the sample light optical path is intercepted to turn the intensity I of the sample light to absolute 0. This enable the calibration and inspection of equipment based on it thereby facilitating the adjustment and inspection while improving the accuracy.