PURPOSE: To facilitate analysis and to expand the use range thereof by performing the excitation of an object and the detection of transmitted or reflected light modulted by the object by using one laser beam modulated by two frequencies.
CONSTITUTION: One laser beam generated by a light source 1 using a laser diode is focused on an object 15 to be inspected through an object lens 14. The laser beam has two intensity modified spectra having separate frequencies f1, f2. The object 15 receives effective excitation by the arithmetic mean of the frequencies f1, f2 to show thermo-wave wave reaction. The thermo-wave reaction of the object 15 is sent to a measuring detector 10 through an optical system 17 equivalent to the object lens 14. The laser beam turned to the object is partically divided by the semi-transparent mirror 2 arranged between the light source 1 and the object lens 14 to be sent to a collimation value detector 11. The outputs of the detectors 10, 11 are sent to a differential amplifier 16 and the amplitude of mixed frequency is detected.
HANSU DEIITAA GAIRAA
MATEIASU WAAGUNAA
MEAS.SCI.TECHNO=1991