Pseudocoloring method using two different spatial modulations
Pseudocoloring of gray level information is a technique for introducing false colors in a black-and-white transparency. The importance of this operation is based on the human eye’s ability to distinguish different colors better than gray levels. In the last few years several pseudocoloring optical methods have been proposed. Furthermore, the pseudocoloring technique has been extended to encode image spatial spectral bands and holographic interferometric fringe patterns. In a recent paper we presented a further generalization of pseudocoloring for assigning false colore to depth level contours of 3-D objects. In this Letter we propose a modification of the pseudocoloring speckle method for storing two images in a single recording material in such a way that each recorded image has a different spatial modulation. Therefore, in a decoding step, on illuminating the processed plate with a white light source, there exist two wavelength values for which the spatial spectra of both encoded images are centered at the same spatial frequency value. Thus, an additive mixture of both images is produced with a pseudocoloring effect which depends on the two mentioned wavelengths.