Abstract

Various methods of optical edge enhancement have been developed. Among them the real-time absolute grad operator is the most attractive. Although hologram based local nonlinear filter can perform the |grad| operation, there are many difficulties in making and operating this holographic filter. In addition, relatively low optical efficiency is a problem. We present here a novel optical filter with the function of AJ₁(2πr₀ρ)e^jϕ, where ρ and ϕ are the variables in polar coordinates at the Fourier plane. This filter is a local nonlinear device that can perform the |grad| operation in real time and can be realized by using a liquid crystal modulator. The transmission-type device has the advantages of high optical efficiency, ease of fabrication, and insensitivity to mechanical vibrations. Experimental results have shown the proposed device has promising applications.

© 1992 Optical Society of America