Abstract: Phase holograms are recorded in the visible with high efficiency by the use of a transparent photosensitive recording composition containing a transparent thermochromic electrochromic or photochromic compound capable of forming a chromatic sensitizer temporarily in situ in the composition when under the influence of external physical excitation appropriate to the nature of the compound, namely heat, an electric field or irradiation. In the process of recording, the physical excitation is applied and maintained during the duration of the recording, whereafter the physical excitation is terminated and the recording composition becomes transparent again leaving the recording constituted solely by local refractive index variations.

Abstract: Photosensitive compositions which include a homogeneous mixture ofA. at least one diazonium salt which is photodecomposable into phenol;B. at least one spiropyran compound which is photodecomposable into mercocyanine; and optionallyC. a material which is normally solid at ambient temperatures and has a melting point no higher than about 150.degree.C and which when in the molten state is a solvent for the phenol and merocyanine compounds from (a) and (b), above.The merocyanine and phenol form colored complexes when reacted in the molten or dissolved state.The photosensitive compositions of the present invention can be used for preparing reproductions of original transparencies containing image areas and non-image transparent areas as positives or negatives thereof and in colors ranging from blue-black, blue, green, red, orange, brown and colors in between.