SPECTROPHOTOMETER

PURPOSE:To enhance the reliability of spectrophotometer, by such a simple constitution that a first sector and a second sector each having a pervious part and a reflective part are respectively used as a beam splitting one and a beam coupling one while spectral diffraction is performed by a frequency component detecting system. CONSTITUTION:The light from a light source 1 for an infrared region is reflected by a concave mirror 2 and the reflected light is split into two light beams by a first rotary sector 3. The first sector has a reflective part and a pervious part each having a specific pattern and the reflected light is converted to a reference light beam 14 while the pervious light to a sample light beam 15 by both parts. A second sector 9 has a pervious part and a reflective part each having a specific pattern and the reference light beam 14 permeated through the second sector 9 and the sample light beam 15 reflected by the second sector 9 mutually passes a monochromator 12 to be incident to a detector 13. The first sector 3 and the second sector 9 are synchronously rotated at a rotation ratio of 1:4 and the ratio of sample beam/reference beam is directly calculated from the output of the detector 13 by a frequency component detecting system.