Diffractive beam direction needs to be controlled agilely and precisely in beam steering and some diffraction
applications. Far field fringe generation, wave front distortion correction by employing programmable diffractive element
is a new interesting research area. A phase-only liquid crystal spatial light modulator is used to produce arbitrary
For the practical application, the main technology we tried includes: 1) the fast recovering speed from arbitrary fringe
to the phase distribution of liquid crystal spatial light modulator, 2) the expected fringe light intensity information is
delivered by phase information. The previous G-S phase recovering algorithm demands more iterative calculations,
which is not suitable for real time purpose. According to the statistics of light field distribution of expected fringes, a
pseudorandom phase encoding method has been used in this work. The expected fringe light intensity information is used
to limit the initial value for phase recovering calculation. By this way, the iterative time has been reduced largely, and
the phase recovering is optimized as well. The expected diffraction fringe can be obtained through 3-5 iterative
The experiment results show that the technology is satisfactory for fast applications.
A 256×256 pixels commercial phase-only Liquid Crystal Spatial Light Modulator (LCSLM) is adopted to generate arbitrary spot patterns successfully. An improved Fourier iterative algorithm combining with pseudorandom phase encoding is proposed to satisfy the real-time processing requirement. The improved algorithm based on the (Gerchberg-Saxton) G-S algorithm with the initial phases generated by the pseudorandom phase encoding method. By employing the improved algorithm, the intensity error of a 4×4 spots array pattern is less than 7%.