High-Sensitive Infrared Photographic Films
Creation and Research of High-Sensitive Infrared Photographic Films for 1300-1700 nm Spectral Range
Tech Area / Field
- CHE-RAD/Photo and Radiation Chemistry/Chemistry
- PHY-OPL/Optics and Lasers/Physics
8 Project completed
Senior Project Manager
Lapidus O V
FIAN Lebedev, Russia, Moscow
- Lawrence Berkeley National Laboratory, USA, CA, Berkeley
Project summaryIt is well known that the efficiency of spectral sensitization of silver halide (AgHal) emulsions by polymethine dyes is significantly lowered upon transition to the infrared region of the spectrum. There is an empirical rule which states that when wavelength of IR radiation is increased by 100nm the light sensitivity of photographic materials falls by approximately an order of magnitude. However, studies of spectral sensitization processes have shown that the fall in efficiency of sensitization in the IR region is determined not by energy deficiency but by the occurrence of secondary dark reactions of oxidation of the primary products of photoreduction of AgHal (atoms of silver), in which dye molecules act as catalysts. The development of methods to inhibit these so-called reactions of dye self-desensitization using organic supersensitizers has made it possible to dramatically improve the efficiency of sensitization in the IR region of the spectrum. The use of supersensitizer compositions has enabled the NIIKHIMFOTOPROEKT (National Research and Design Institute of Photochemical Industry) to produce a high sensitivity infrared film, I-1060V-2, with a sensitization zone of 800-1100nm and an energy sensitivity at the sensitization maximum of max = 1060nm, much higher than that of analogues. The I-1060V-2 infrared film does not need additional hypersensitization and, with respect to light sensitivity, it is approximately a factor of ten better than the best overseas analogue, the photographic material I-Z from Kodak (USA), after preliminary hypersensitization. The longest wavelength IR–film produced in NIIKHIMFOTOPROEKT is the I-3 film for registration of light with max =1315nm.
The design of new long wavelength IR photographic materials is of particular importance as it facilitates the sensitization of AgHal emulsions to the > 1300nm region of the spectrum, which was considered inaccessible to photographic techniques until only recently.
As a result of research in recent years, new methods have been found for the supersensitization of IR-films, allowing a further increase in the efficiency of spectral sensitization in the IR region of a spectrum and culminating in a level of efficiency in the visible region of the spectrum. These methods completely inhibit secondary dark processes of dye self-desensitization and include determination of optimum compositions of supersensitizers, microcrystals of silver halide of a definite structure and IR dyes, to achieve maximum photographic effect. The developed new methods of supersensitization of IR-films allow an essential improvement in the basic characteristics of IR-films. This concerns an increase in photosensitivity without an increase in film resolution, or a substantial growth in film resolution without a change in photosensitivity. However, the most essential achievement consists in simplification of the technology of manufacturing and chemical- photographic processing of IR-films. Characteristically, new-generation IR-films can be applied in the same way as traditional ones, without additional operations. The new methods of supersensitization create the basis for the development of new-generation IR-films with max 1300nm.
For the development of longwave IR-films one must conduct a cycle of works including synthesis of new organic dyes - spectral sensitizers AgHal, synthesis of photographic emulsions with certain surface properties, research of processes of supersensitization of new dyes and, finally, the search for ways to stabilize IR-films. At all stages the research should be conducted with experimental samples of films, to determine absolute sensitivity and its dependence on wavelength radiation, spatial resolution of a photographic film and its dynamic range, with the purpose of optimizing the technological processes of emulsion production.
For these purposes facilities will be created for film testing, on the basis of an electron accelerator (emitting absolutely calibrated synchrotron radiation with a wide output spectrum) at the Lebedev Physical Institute and IR spectral range laser setups in VNIIEF, to determine IR film spectral, energetic and spatial characteristics, and to optimize their use.
Possible areas of application of such films are: spectroscopy, astronomy and astrophysics, medicine (e.g. for photographic registration of hypodermic vascular alterations), criminalistics (e.g. for detection and revealing of erasures and counterfeits of documents); art (for photography of works of art in IR rays, to reveal primary sketches and to distinguish originals from fakes).
The first year of the project is devoted to the development of methods to increase the photosensitivity and resolution of IR-films for registration of radiation in the 1300-1400nm zone.
The second year of the project is devoted to the creation of IR-films with >1400nm.
The new methods of IR-film supersensitization, to be developed in the framework of the Project, and modern synthesizing photoemulsions will be protected by respective patents.
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