A novel laser screen method with retroreflector for velocity measurement is introduced for some special velocity measuring occasions like wide spreading range or large caliber projectiles.The large effective screen area is formed by laser diode

cylinder lens

photodiode with a central hole

and retroreflector.When flying objects with high speed pass through the laser screen

change of light flux is transformed by photodiode into electronic signal and sampled by data sampling card.Data processing is finished by professional software in computer.A new important concept of remained divergence angle and measuring method based on digital CMOS camera are put forward.It gives the typical sampled waveform and a series of speed data of Φ7.62 mm projectile measured by the retroreflector laser screen system with effective screen area of Φ500 mm.As a result

the velocity measurement method based on retroreflector laser screen has advantages of convenience in optic adjustment

large effective laser screen area and high sensitivity.