Real-time holographic image restoration in azo dye doped polymer films

We describe a method that allows increasing the intensity of images holographically recorded in azo dye doped polymer films. The saturation of photoisomerization processes decreases the modulation depth of a holographic grating, hence the intensity of the reconstructed image. This process can be inhibited by illuminating a hologram with a uniform control beam that has the effect of increasing the saturation intensity of the film. Experiments done with a hologram recorded at 514 nm have shown that a control beam at 633 nm can increase the diffraction efficiency of the hologram, thus, allowing to restore the image at an intensity level facilitating its detection. (c) 2005 Elsevier B.V. All rights reserved.