A laser pulse contrast ratio measurement device is presented, the device comprising a laser pulse generator for generating a sum frequency laser pulse, the laser pulse generator providing an interaction zone, a beam guide device having a first beam guide for guiding a reference beam to said interaction zone in said laser pulse generator and a second beam guide for guiding a probe beam to said interaction zone in said laser pulse generator. The device further comprises a detection unit for detecting the sum frequency laser pulse generated in said laser pulse generator. The probe beam has a probe beam frequency, whereas the reference beam has a reference beam frequency, wherein the reference beam frequency corresponds to the second harmonic of the probe beam frequency. The beam guide device of said device is adapted to direct the reference beam and the probe beam in a non-collinear manner under an interaction angle on said laser pulse generator so that the probe beam and the reference beam interact in the interaction zone of the laser pulse generator so as to generate the sum frequency laser pulse in the laser pulse generator, and wherein the beam guide device is adjusted to provide the interaction angle between the reference beam and the probe beam in the interaction zone in the laser pulse generator to be greater than 3°.