The invention provides a swill-cooked dirty oil detecting
system. A semi-reflection and semi-transmission
beam splitter is arranged at an emission port of a
femtosecond laser; a pulse
laser light is split into a pump light path and a detecting light path; the pump light path is connected with a photochopper, a first attenuation sheet, a first reflecting mirror, a second reflecting mirror, a first focusing lens and a
gallium arsenide photoconductive antenna in sequence; a sample box is arranged on a
confocal point of second and third paraboloidal mirrors; a second collimating lens, a
half wave plate, a light
path delay device, a third reflecting mirror, a
polarizer and a
high resistivity silicon reflecting mirror are arranged on the detecting light path in sequence; the
femtosecond laser after being sampled by an electrooptic
crystal is detected by being directed with a photoelectric
detector via a quarter wave plate, a third focusing lens, a fourth reflecting mirror, a fourth focusing lens, a Wollstone
prism as well as second and third attenuation sheets; and the variation of
voltage magnitude caused by terahertz
waves is recorded, so that a
time domain terahertz
signal including swill-cooked dirty oil information is obtained. The swill-cooked dirty oil detecting
system provided by the invention has the advantages of simple detecting process, high efficiency, rapidness and accurate detecting result.