method for the conversion of absorptiehologrammen in fasenhologrammen

摘要

1326313 Holograms AGFA-GEVAERT A G 14 May 1971 [26 May 1970] 14888/71 Heading G2J Phase holograms are photographically produced from absorption holograms using a light-sensitive layer which undergoes a change of refractive index or exposure. Preferred layers are bichromated gelatine and photo-crosslinkable polymers (e.g. polyvinyl annamates), an exposed bichromated gelatine layer may be soaked (especially in a hardening solution), optionally treated with a photographic fixer, rapidly dehydrated (e.g. with isopropanol) and dried. Preferably the image bearing surface of the absorption hologram is contacted with the support of the light-sensitive layer and a laser beam passed through the assembly while maintaining the Bragg condition. In modifications either (a) a mirror is contacted with the light-sensitive layer so that two transmission and two reflection holograms are recorded, or (b) a second reference beam is additionally used so that single transmission and reflection holograms are recorded. Any shrinkage in the absorption hologram can be compensated by using shorter wavelength light for the exposure. Reference has been directed by the Comptroller to Specification 1259971.