The present invention provides an optical detection system in which a first mirror of the control unit is used to receive light beam and redirect it into a first one-dimensional off-axis parabolic mirror. The first one-dimensional off-axis parabolic mirror then directs the light beam to a cylindrical lens. Through the mechanism of reflection, the cylindrical lens further directs the light beam to a second one-dimensional off-axis parabolic mirror. The second one-dimensional off-axis parabolic mirror then directs the light beam into a second mirror. The detection unit of the system is used to detect the light beam coming from the control unit, so as to convert the light signals into electric signals for the analysis in the process unit afterwards.