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
3 Approved without Funding
FIAN Lebedev, Russia, Moscow
- Scientific Center NIIKHIMFOTOPROEKT, Russia, Moscow\nVNIIEF, Russia, N. Novgorod reg., Sarov
- Fukui University / Research Center for Development of Far-Infrared Region, Japan, Fukui\nLawrence Berkeley National Laboratory, USA, CA, Berkeley\nENEA / ICF Physics and Technology Laboratory, Italy, Frascati\nGeneral Atomics, USA, CA, San Diego\nAGFA-Gevaert N. V., Belgium, Mortsel
Project summaryThe offered project is devoted to the development of a new infrared (IR) photographic films sensitive in the wavelengths range 1300-1700 nm at simultaneous improvement of IR films characteristics (sensitivity, photographic latitude and resolving power) in already mastered range 800-1300 nm.
This films are used, in particular, in research of the space characteristics of radiation (pergence, distribution of the flux density in the cross section of the beam) of the lasers operating in the IR spectrum area (neodymium, iodine). It is connected with the fact that in the region of wavelengths ~1300 nm and more there are no highly sensitive detectors of radiation of a CCD arrays type which are widely spread for more short-wave spectrum region 190-1100 nm. Of special note is that such films can be used in usual photographic registration equipment what makes essentially cheaper the process of obtaining new information in comparison with equipment on the CCD arrays base. Their use in already developed super high speed photographic recorders for the visible spectrum opens new possibilities of investigation of processes in the IR range in the modes of slot-hole scanning and time lens in microsecond exposure interval. It is important, that IR films have practically unlimited transversal sizes for images registration while receiving sites of CCD arrays used for the similar purposes, are limited by several millimetres what demands additional rather sophisticated re-projection optics usually causing the loss of space resolution and illumination power of registration. IR films are insensitive to electrical and magnetic fields, as well as to the influence of the temperature in the range between -30oC and +50oC that is extremely important in the number of applications.
Other possible areas of application of such films are the following: 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 a photography of works of art in IR rays, that allows to reveal on pictures primary sketches and to distinguish the originals from their fakes), and fiber-optics communication technologies.
Thus, improvement of the IR films characteristics and extension of the area of their spectral sensitivity should allow to make a new steps in researches in the IR spectrum region. The final objective of the project is preparation of commercial prototypes of the films suitable for application in various laboratories of the world.
It is well known that the efficiency of spectral sensitisation of silver halide (AgHal) emulsions by polymethine dyes is significantly lowered on moving into the infrared region of the spectrum. There is an empirical rule which states that on increasing the wavelength of IR radiation by 100 nm the light sensitivity of photographic materials falls by approximately an order of magnitude. This conclusion led to a theoretical determination of the practical limit of spectral sensitization of AgHal emulsions as about 1240-1350 nm.
In the theory of photographic processes the reduction in sensitivity is considered to be connected with the energy deficiency constantly growing as one advances to the IR spectrum field. Such an energy restriction imposes a principal prohibition on the development of high-sensitivity infrared photomaterials. But, the investigation of the process of spectral sensitization shows that the reduction of spectral sensitivity efficiency in the IR field is determined by the existence of secondary dark reactions of oxidation of the products of photoreproduction of AgHal (Ag atoms), where molecules of dyes play a role of catalyzer, rather than by energy deficiency. In an infra-red photographic material after photoexcitation an oxidizing process takes place (which is stimulated by the infradye) thus the precentres of the latent photographic image burn down.
Development of methods for inhibition of these so called reactions of self-desensitization of dyes with the use of organic supersensitizers permitted to increase substantially an efficiency of sensitization in the IR region of spectrum.
The longest wavelength IR –film produced in SC NIIKHIMFOTOPROEKT and not having any foreign analogues is the I-3 film for the registration of radiation with =1315 nm. A possibility of sensitization of AgHal emulsion to the spectrum range with 1300 nm and creation of new long-wave IR photographic materials is of fundamental importance because it opens up the range considered until recently as inaccessible to photographic techniques .
As a result of recent researches the new methods of supersensitization of IR-films were found, allowing to increase even more the efficiency of spectral sensitization in the IR region of spectrum and to bring them nearer to a level of efficiency in the visible region of spectrum. These methods completely inhibit secondary dark processes of dyes self-desensitization. Development of new methods of supersensitization of IR-films allows to improve essentially the basic characteristics of IR-films.
For development of longwave IR films it is necessary to conduct cycle of works including synthesis of new organic dyes – AgHal spectral sensitizers, synthesis of photographic emulsions with determined surface properties, investigation of supersensitizion processes of new dyes and finally, to find ways of stabilisation of IR films. At all stages of the project it is necessary to carry out investigations with experimental samples of the films for determination of absolute sensitivity and its dependence on radiation wavelength, film resolution and dynamic range.
Therefore, the main questions which will be solved in the course of project realization could be formulated as follows:
1. Synthesis of new IR polymethine dyes – derivatives of benzotiazole and quinoline for the spectral sensitization of silver halides in the spectrum region 1300-1700 nm.
2. Synthesis of microcrystals of AgHal with various forms for selection of an emulsion system with optimal dye adsorption.
3. Development of methods for supersensitization of adsorbed dyes to increase the efficiency of spectral sensitization in the IR spectrum region.
4. Antihalo protection of IR films.
5. Stabilisation of IR films in time.
6. Preparation of IR films samples for investigation of their characteristics.
7. Creation of stands on the basis of IR lasers (1060 mm – 1700 mm) for determination of characteristics of IR films.
8. Determination of the main characteristics (spectral sensitivity, resolving power, photographic latitude etc.) of IR films on laser stands.
9. Creation of research stand for measurement of IR films characteristics, including a solid-state laser source on the base of an optical parametric generator (OPG) with continuously tunable wavelength of output IR radiation and diagnostics measurement equipment.
10. Measurement of absolute sensitivity of IR films and its dependence on the wavelength in the range 1300-1700 nm, dynamic range and spatial resolution of the films with the use of OPG radiation.
11. Experimental testing of IR films in the possible fields of their application.The project will be executed by forces of three institutes: SC NIKHIMFOTOPROEKT (Moscow), P.N.Lebedev Physical institute of Russian Academy of Sciences (Moscow) and Russian Federal Nuclear Center (VNIIEF, Sarov city). All Russian organisation-participants of the Project will concentrate their efforts on the creation and testing of the experimental samples of new IR films with more perfect characteristics both for laser beams and common radiation sources.
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