DEVELOPMENT OF AN IMPROVED HIGH INTENSITY HIGH RESOLUTION SCREEN FOR REAR PROJECTION

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Document Number (FOIA) /ESDN (CREST): 
CIA-RDP79B00873A001600010002-5
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RIPPUB
Original Classification: 
K
Document Page Count: 
53
Document Creation Date: 
December 28, 2016
Document Release Date: 
September 11, 2012
Sequence Number: 
2
Case Number: 
Publication Date: 
September 20, 1963
Content Type: 
MISC
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PDF icon CIA-RDP79B00873A001600010002-5.pdf2.05 MB
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Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 DEVELOPMENT OF AN IMPROVED HIGH INTENSITY HIGH RESOLUTION SCREEN FOR REAR PROJECTION ? STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT DEVELOPMENT OF AN IMPROVED HIGH INTENSITY HIGH RESOLUTION SCREEN FOR REAR PROJECTION Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 SIN31NO3 JO 3181,1 Veclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 SI-AT TABLE OF CONTENTS LETTER OF TRANSMITTAL COST QUOTATION TERMS AND CONDITIONS 1 INTRODUCTION 2 OBJECT OF SCREEN RESEARCH AND DEVELOPMENT WORK 3 FEASIBILITY DEMONSTRATION 4 DETAILED WORK STATEMENT 5 PROJECTION 'SYSTEM FOR FINAL FEASIBILITY DEMONSTRATIONS 6 SUGGESTED FURTHER STUDIES BASED ON OUTCOME OF ABOVE WORK 7 PROGRAM SCHEDULE APPENDIX TECHNICAL DATA Miscellaneous Properties Percent Transmission vs Wavelength for Cronar Film .007" Percent Transmission vs Wavelength for Cronar Film .005" Percent Transmission vs Wavelength for Cronar Film .004" Density vs Wavelength for Type 5430 Film Density vs Wavelength for Type 5427 Film CAPABILITIES Available Equipment at RESUMES :esearch Center STAT STAT STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 [Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 L. STAT Main Post Office Box 2143 Washington, D.C. Subject: Reference: Gentlemen: High Resolution Projection System Letter Proposal 3-1303 Proposal 3-1303A Thank you for your verbal request for a further proposal on a high resolution projection system. The present proposal is basically a research and development program centered on the development of a suitable fluorescent screen for such a system. The basic idea of this proposal has been tested by and a patent has been applied for. The development of the the point where it is readily reproducible. In the course of the program-a suitable projector and optical system will be designed to excite the screen. screen will be taken to A complete cost breakdown for the work specified is attached, together with a time schedule. The costing of the program is based on a cost-plus-fixed-fee contract under the Armed Services Procurement Regulations, appropriate details are enclosed. The basic research work work will be a with The our facilities on the screen materials will be done at the as they are ideally equipped to do this work. This subcontract: however, the overall program control and direction and located close to easily maintained. enabling control and liaison to be ill submit monthly progress reports, in addition to a final report, on the findings of the whole program. Just prior to the submission of this proposal we received your samples of Type 5247 and 5430 film. We have run density versus wavelength tests on these and the graphs are included in the Appendix under Technical Data. STAT STAT STAT STAT STAT STAT remains STAT STAT STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Washington, D. C. At your request, has limited posal to the home office in the distribution of 20 SeptembISTAT53 Page 2 information regarding this p:STAT STAT Should you have any questions regarding this proposal, or require either additional information or a local contact, please do not hesitate to contact us. WDS:ek Sincerely, Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 R Next 1 Page(s) In Document Denied Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 0 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 SNOWONO3 ONV SIAIII31 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT 3-1303B TERMS AND CONDITIONS (Cost-Plus-Fixed-Fee Researchand Development Contract) Terms and Conditions substantially in agreement with the Armed Services Procure- ment Regulations would be acceptable to under STAT any Cost-Plus-Fixed-Fee Research and Development Contract resulting from this proposal. It is requested that the following provisions be incorporated in the resulting contract.; 1. "Stop Work Orders!' Clause ASPR 7-404,5 2. Contractors Independent Research Programs a. Any invention made in the performance of any work by the Contractor under the Contractor's own product improvement program or the Contractors Independent Research Program, even though supported by an allowance of costs for such pro- gram as a part of the overhead costs hereof, will not be sub- ject to the "Property Rights in Inventions" clause of this contract unless said work is identified in writing as being required in the performance of this contract. b. The concept contained herein is regarded properietary and retains all rights to concept. commercial applications of the 3. Payment - Net within 30 days after date of invoice. 4. Payment of the fixed-fee under this contract shall be made in monthly installments. Each installment shall bear the same proportion to the total amount of the fixed-fee asthe_proportion of work completed at the date of such claim bears to the total work called for under this contract. 5. Reimbursement and settlement of overhead expenses shall be on an actual rate as established by the cognizant Government audit agency. Pending establishment of the final overhead rates for any period, provisional reimbursement will be made on the basis of billing rates approved by the cognizant Government Auditor. Declassified in Part - Sanitized Copy Approved for Release 2012/09/11 : CIA-RDP79B00873A001600010002-5 STAT LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 TERMS AND CONDITIONS (Continued) [: (Cost-Plus-Fixed-Fee Research and Development Contract) STAT STAT 3-1303B 6, "Authorization and Consent" clause ASPR 9-102.2. 7. "Patent Rights" Clauses ASPR 9-107.1(a), 9-107.2(a) and 9-107.2(b). 8. Authority to Subcontract - Sole Source Subcontract Approval, is hereby granted approval to subcontract to STAT STAT as a sole source subcontractor, a portion of STAT the work on a Cost-Plus-Fixed-Fee basis. General - cognizant Government Audit Agency is the Air Force Auditor General in coordination with Administrative Contracting Officer, Headquarters, Los Angeles Contract Management District. STAT STAT STAT STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 NOI1d1113S30 1V3INH331 LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT C 1. INTRODUCTION Our earlier proposal Register No. 3-1303A, was for a system designed to STAT increase the rate of information transfer from a projected film image to an observer. The proposal covered areas of research which would improve screen resolution by using new screen materials, new projection techniques and by investigating certain physiological responses. This proposal Register No. 3-1303B is specifically for a research and STAT development program to produce a high intensity, high resolution fluorescent screen of optimum performance for the rear projection of a black and white film image. The light source used for projection will be strong in ultra- violet as well as visible light. requests that the concept contained herein, and the successful developmeniSTAT of an improved screen be regarded as proprietary and retains all rights to commercial applications. 1-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 2. OBJECT OF SCREEN. RESEARCH AND DEVELOPMENT WORK The object of this research and development work, as detailed below, is to produce a high resolution, rear-projection screen of improved performance. The proposed screen will comprise a layer of fluorescent material on a glass- like substrate and will have a high degree of transparency to visible light. Tests will be performed to determine the optimum illumination of the screen to provide the maximum rate of transfer of information. It will be illuminated by: a Ultraviolet light alone so that a visible linage may be formed on the screen. b. Visible light alone so that an aerial image can be formed and transmitted through the screen and viewed by a supplementary magnifier in front of the screen. c. A combination of visible and ultraviolet light, the aerial and visible linage as formed being brought to a focus in the same plane. A projector lens corrected for the ultraviolet and the visible is necessary for the above experiments. Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Li 7 STAT 3. FEASIBILITY DEMONSTRATION To demonstrate the feasibility of the screen small samples a few inches square will be used. From these an initial evaluation will be made to determine image quality using ultraviolet light,viewing. Final evaluation of the best samples will be made using a projector having high- power ultraviolet and visible light sources and which will achieve the magnifi- cations required in practice. The above is discussed in detail in the following work statement. 3-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT 41.= '71 4. DETAILED WORK STATEMENT Make necessary jigs and fixtures. b. On a suitable, transparent glass-like substrate make trial coatings of zinc sulfide and cadmium tungstate by vacuum deposition. Coatings will be of zinc sulfide activated with copper, chlorine, phosphorus or arsenic, and of cadmium tungstate with tungsten or manganese activator. .In parallel with the above an extensive search of literature will be made to determine what (applicable to the project) has been done in this field and whether there are more promising materials which should be tried. d. It is also proposed to make organic luminescent coatings of anthra- cene, fluorene, rubrene, diphenylcyclo-octatetraene and umbelliferone in an acrylic resin or a polycarbonate resin. e. These samples will be tested using ultraviolet stimulation and measurements made of visible emission brightness. f. An evaluation of the best of these coatings will be made to determine image quality using a small ultraviolet projector which is currently available and whether sufficient resolution and brightness can be obtained for direct image viewing. ?A feasibility demonstration will be carried out using a projector with a lens corrected for ultraviolet and visible light. The film frame will be projected on an area of at least 30 by 30 inches and an evalu- ation will be made of the visible image, the aerial image and the composite image formed by the ultraviolet and the visible light. 4-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 ' LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT 4.1 CHARACTERISTICS OF THE FILTERING a. For transmission of ultraviolet (UV) in the rpion required to excite a phosphor sensitive in the region 3500-4000 A. This would be a com- bination absorption filter having a characteristic as shown in Figure 1. The broken line is transmission by the lens materials and the full line is transmission of Corning 7-54 filter. The shaded area repre- sents transmitted UV. % RELATIVE TRANSM I SSI ON 350 400 WAVELENGTH (Mg) FIGURE 1 Percent Transmission for Corning 7-54 Filter and Lens Material 450 500 This combination would be used if it proves feasible to view the over- all scene and to study in detail an area of interest using luminescence of the screen only as discussed b. For transmission of both UV for exciting the phosphor, and visible for specular viewing, the filtering curve in Figure 2 would apply. Here the broken line is the lens and full line is a filter-like Balzer 1256/283 CALFLEX Bl/Kl. 4.2 CONTRAST TRANSFER FUNCTION GOAL Preparation of three types of luminescent screen is planned. These will be in- organic transparent, inorganic diffuse and organic transparent. Brightness of ultraviolet stimulated visible emission will be measured by a photocell. Resolu- tion capability will be evaluated by standard resolution test pattern image observations. t= 4-2 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 % TRANSMISSION 100 80 60 40 20 STAT 300 400 500 600 700 800 WAVELENGTH (Mg) FIGURE 2 Percent Transmission for mv and Visible for Lens and Filter Balzer 1256/283 CALFLEX Bl/K1 To measure contrast transfer function would require use of a specialized micro- densitometer, which we do not have. As the result of this program we shall be able to define the requirements for the apparatus to make these measurements. This may form the basis for a separate proposal in which we would undertake to compare performance of the screens produced in this work with those in the prior art. 4.3 FILM BASE AND EMULSION OPTICAL CONSIDERATIONS Information has been obtained concerning Eastman 5427 Aerographic duplicating film which has a cellulose acetate butyrate base and also for Eastman type 8427 Aerial Recon. duplicating film which has a cellulose tri-acetate base. Curves are shown in Figure 3 below, for spectral transmission of base alone and of processed unexposed base with emulsion. The curves show that transmission does not vary greatly throughout the spectrum of interest. Curves for other materials are included in the Appendix. H&D curves of density versus exposure for various processing procedures (see Figure 4 below) show that, for faithful reproduction of the original film, the range of transmission of the film may be from 607 (D = .22) to approximately .17 (D = 3.0) or about 600:1. 4-3 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 % TRANSMISSION 100 80 60 40 20 CELLULOSE ACETATE BUTYRATE STAT 5247 200 250 300 350 WAVELENGTH ( MI0 FIGURE 3 Percent Transmission versus Wavelength 4.4 PHOSPHOR CONSIDERATIONS 4.4.1 INORGANIC PHOSPHORS 400 A literature search for figures relating luminescent yield of phosphors for incident energy so far has yieldedolittle 4:formation on transparent phosphors excited by near ultraviolet (3500 A - 4000 A). Extensive discussions are given for diffuse or crystalline surfaces which are commonly used for TV and instru- mentation cathode ray tube phosphors. These phosphors are generally excited by electron beams and information relating to ultraviolet excited emission has been mostly qualitative. In general, manufacturers of phosphors regard ultraviolet stimulated visible emission as weak, compared to electron beam excited emission, yet it may be adequate for our purpose. One reason for the weak emission of transparent phosphors is that a single passage of the ultraviolet does not allow much path length for absorption. For diffusion crystalline phosphors a much greater path length is traversed due to multiple internal reflections in the crystals. For transparent phosphor screens, emission of light measured in the direction of the viewer is about 25 to 507 of the total emitted by the phosphor. 4.4.2 ORGANIC PHOSPHORS Organic luminescent materials have been investigated much more fully because absorption of ultraviolet and emission of visible and ultraviolet are used as a tool for analysis of organics. However some materials which luminesce in liquid solution will not do so in solid solution. For others the converse is true. Also increase of concentration in solution sometimes results in a decrease in emission. 4-4 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 iDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 ILLUMINANT: TUNGSTEN DEVELOPMENT: DK.50 AT 68? F ? (20? C) IN SENSITOMETRIC MACHINE 0.0 1.0 LOG EXPOSURE FIGURE 4 Percent Transmission versus Density 2.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 .8 DENSITY STAT 4-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 5. PROJECTION SYSTEM FOR FINAL FEASIBILITY DEMONSTRATION In conjunction with the above work a projection system will be designed capable of handling up to a 2.5 KW light source and yielding ultraviolet as well as visible light, with suitable filters therefore, it will be possible to excite the fluorescent screen with ultraviolet or visible light or both. To prevent damage to the film due to heat, infrared transmitting mirrors and infrared filters will be incorporated in addition to refrigerated air cooling as may prove necessary. The projector will illuminate a screen area of at least 30 by 30 inches so that any fluoresent sample under test will receive the energy per unit area that would be experienced in practice. In order to test the full capabilities of the screen, a projector lens will be designed so that the ultraviolet and visible light are brought to a sharp focus on the screen. The lens will therefore be corrected over the range from 35001 to 60000X and will also have a resolution of 200 lines per mm. The maximum magnification of the projector system will be approximately 50 times. An additional optical system may be used in front of the screen so that quality of the visible linage formed by the ultraviolet and the aerial image formed by the visible can be evaluated both independently and together. A minimum of four spectral interference filters will be provided to select appropriate wavelengths for the viewing of the visible light. 5-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 6. SUGGESTED FURTHER STUDIES BASED ON OUTCOME OF THE ABOVE WORK Should successful single layer fluorescent screen samples be developed, follow- up work and studies should encompass: a. The technique of making larger screens of approximately 30 by 30 inches should be mastered b. Screen samples having multiple coatings should be developed and evaluated. Such screens could render density levels in the form of color. c. The basic objective of obtaining maximum information transfer from a projected film image to an observer should be followed up using the maximum number of observer sensitivities. For example, the intensity of light on a multiple coated screen could control the depth to which light penetrates. Using coatings flourescing at different wavelengths, and using color-separating filters, an observers perspective detecting faculty could discern density levels. Other physiological responses, which were discussed in the previous proposal 3-1303A, and which could be applied to the viewing of a fluorescent screen, should be investigated in order to produce an optimum overall system. 6-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 STAT LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 r SI-AT 7. PROGRAM SCHEDULE The PERT diagram (Figure 7-1) depicts a summarized program outline. See Figure 7-2 for Program Organization. At the end of the first 3 weeks of the program a sufficient evaluation of the initial coatings will have been made so that the design and procurement of projector parts can proceed. Continued studies and work on experimental screen coatings will take place in parallel with the projector lens design, and projector procurement and assembly. This phase of the work will cover a period of thirteen weeks. The time spent on the literature survey of screen materials etc., will be about 120 hours. This time will be spread over a period of 16 weeks as shown on the PERT diagram. Final evaluation of the best screen using the projector with a 2.5 KW light source, and necessary filters etc. will take place over a 6 weeks period. s uniquely suited to accomplish the tasks required in this proposal. STAT A description of the background and facilities can be found in the Appendix. 7-1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 CD (TO 715e-classified in Part- Sanitized Copy Approved for Release 2012/09/11 : CIA-RDP79B00873A001600010002-5 cD11-= LITERATURE SURVEY OF SCREEN MATERIALS DESIGN OF JIGS AND IXTURE PROJECT AND PRO- ORGANI2- ? CUREMENT ATION OF PHOS HORS I WEEK I.WEEK EVALUATION ? OF INITIAL COATINGS CONTINUED WORK ON EXPERIMENTAL COATING AND MEASUREMENTS AS SAME FINAL EVALUATION AND FEASABILITY STUDIES OF BEST SCREENS 2 WEEKS PROJECTOR LENS DESIGN AND LENS MANUFACTURE AND ASSEMBLY OF PROCUREMENT OF PROJECTOR PARTS 8 WEEKS PROJECTOR SYSTEM WEEKS FIGURE 7-1 Program Outline 6 WEEKS 0 FINAL REPORT 0 2 WEEKS Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 25 WEEKS STAT STAT Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 Isection ,LDeclassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 11/1HIWAL jr rrIYc.ML,urt KODAK AERIAL AND SPECIAL SENSITIZED MATERIALS 11 1 MScrD.iflirs Pr.pertes Section 11 0 Optical Properties This section presents data on the optical characteristics of aerial films which might be of some use in the design of special photographic systems, or of value in the interpretation of effects. The spectral trans- mittance of film base and emulsion-coated films is given, together with typical values for haze, as it might affect the clarity of negatives, printing techniques, etc. The indexes of refraction of cellulose ester and Estar polyester bases are of practical importance in their effect on the fogging of aerial films by accidental edge illumination, and on image resolution. A. SPECTRAL TRANSMITTANCE The spectral-transmittance curves for cellulose ester and Estar bases, and for various aerial films which have been developed and fixed without exposure, are given in Figures 11-1, ?2, ?3, and ?4. Both types of base show a sharp cutoff in the ultraviolet region (Figure 11-1). The cellulose ester base does not transmit below about 270 millimicrons, or the Estar base below 315 millimicrons. In the visible region both types of clear base show excellent clarity with high, uniform transmission. In the case of the gray triacetate base the spectral transmission is affected by the dyes incorporated for antihalation purposes (Figure 11-3). Estar and cellulose ester bases show high transmission in the near infrared region out to 2 microns wavelength (Figure 11-4). Between 2 and 15 microns there is considerable variation in trans- mission with wavelength. In this region the infrared .absorption char- acteristics of the particular polymer are of value in analytical deter- minations of structure and composition, but are probably not of practical importance in photographic applications. The transmittance values for emulsion-coated films developed and fixed without exposure show changes from the base curves in june 1961 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 r Men ear raclas`sified in Part - Sanitized Copy Approved for Release 2012/09/11 : CIA-RDP791300873A001600010002-5 OM `"4 01118 the ultraviolet and visible regions (Figures 11-2 and 11-3). The transmission is slightly reduced as a result of residual traces of back- ing dyes and emulsion silver. Transmission in the near infrared region is not significantly affected by the presence of the fixed-out, clear gelatin layers (Figure 11-4). The data in Figures 11-1, ?2, ?3, and ?4 are based on total transmission. Measurements comparing the total, or diffuse-light, transmittance with the specular-light transmittance show the latter to be only 2 to 3 percent less for the film bases and for films that con- tain no matte in the emulsion or gel backing. Where a matte is present in the fixed-out film, the specular transmittance averages 12 to 15 percent less than the total transmittance. B. HAZE Extremely fine particles dispersed in the film base or gel layers act just as atmospheric haze does in the scattering of light rays. "Haze" is defined as that percentage of transmitted light which, in passing through a sample, deviates from the incident beam by fOrward scat- tering, i.e.: Scattered Light % Haze = Total Transmitted Light x 100 It may be measured by a hazemeter or recording spectropho- tometer, as described in American Society for Testing Materials, Method D 1003-59T. Typical haze measurements for film bases and unexposed proc- essed films are shown in Table 11-1. Both cellulose ester and Estar bases are quite free from light-scattering effects, and the haze of clear, processed films that contain no matte is generally less than I percent. In the gel-backed films a matte is incorporated to reduce intimacy of contact between laps of film and to avoid Newton's rings in printing operations. This matte results in haze values of 8 to 12 percent. The practical effect of this amount of light scattering is not ordinarily significant in the use of the films. Matte particles are not resolved except under conditions of very high magnification (80 to 100X). However, it must be recognized that haze might cause some slight loss of resolution in printing operations under very critical conditions involving specular illumination. C. REFRACTIVE INDEX The refractive indexes of film components are probably of practical interest only in very special cases where the design of systems re- quires recognition of this optical property. Typical values for refrac- tive index are as follows: r , Cellulose Ester Bases Estar Polyester Base Vertical axis Perpendicular to major axis in.olane of sheet Major axis in plane of sheet Gelatin N., Nr Refractive Index ND 1.48 1.50 1.64 1.66 1.50- 1.54 A material which exhibits variations in refractive index in dif- ferent directions is said to show birefringence. Because of the biaxial stretching of Estar base in manufacture, it exhibits this behavior. As shown above, the greatest difference in index of refraction is be- tween the thickness direction and the plane of the sheet. Differences in the plane of the sheet, not necessarily in the length and width directions, are slight and generally less than 0.02. The effect of this slight difference in orientation on dimensional stability of Estar base is discussed in Section 9. The birefringence of cellulose ester bases is almost negligible, being of the order of 10-5. D. EDGE FOG A very practical effect of the difference in refractive index between cellulose ester and Estar bases is in the extent of film fogging which may result from exposure of the film edges to light and consequent "piping" of the light through the film base. This is entirely separate from film fogging by accidental exposure of the emulsion surface to light. When the ratio of refractive index of the gelatin coating to the base is less than 1.0, as in the case of Estar base film (m=1.54/1.64), efficiency of internal reflection within the base is high over a wide range of incident angles. Where the ratio is greater than 1.0, as with cellulose ester base films (m=1.54/1.48), efficiency of internal re- flection is much lower. Therefore, much of the incident light striking the edge of Estar base is propagated through the base and is attenu- ated only gradually by absorption within the base and by refraction at the gel interfaces. Any light refracted out into the emulsion fogs the film. This may take the form of a fog density uniformly decreasing with dis- tance from the edges or, under certain geometric and optical con- ditions, the light may be lost from the support to the gel layers in a repeating wave form, resulting in a striated fog pattern. The high efficiency of light propagation through Estar base, - I Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 r r (11classif1ed in Part -Sanitized Copy Approved for Release 2012/09/11 : CIA-RDP79B00873A001600010002-5 Pei mir 1,3% compared with cellulose ester base, is the same as in polymethyl methacrylate and certain other plastics. Here, the phenomenon is utilized in medical applications, such as the bronchoscope, or as rod extensions on flashlights. This effect is evident on viewing a roll of Estar base Alm from the side, where light transmitted through the edges of the film base is visible. These effects are illustrated in exaggerated form in Figure 11-5 which shows the fog produced in various films that have all been given the same edge exposure in a laboratory comparison test. These films, shielded on the emulsion and base sides, were given a con- trolled exposure, with the illumination directed at the cut edge of the filrns. While there is a fixed, inherent characteristic of Estar base to "pipe" light, the actual depth of fog penetration is influ- enced by the emulsion speed. As the "piped" light attenuates with distance the threshold exposure of slower emulsions is reached sooner. This is indicated by the lesser penetration of fog in the slower Experi- mental High Definition (S0-132) and Experimental Panatomic-X (S0-130) Aerial Films, compared with the Experimental Plus-X (S0-102) Aerial Film, though all are on the same Estar base. Penetration is likewise affected by any absorbing or diffusing addenda in the base, such as haze, dye, or pigment. The gray cellu- lose triacetatc base very effectively stops the light penetration, as illustrated with Special High Definition Aerial Film (S0-243) in Figure 11-5. The above laboratory test is deliberately exaggerated. Figure 11-6 illustrates the effect of the base type on edge fog penetration under more practical conditions. Rolls of film with a clearance of 0.025 inch between the edges of the roll and the spool flange were exposed to an illumination of 2240 foot-candles for 4 minutes. A certain amount of the light was reflected from the inside of the flange at the proper incident angles to penetrate the film base and fog the emulsion, as illustrated. The Estar base film shows slightly deeper penetration than the triacetate base films. The increased fogging potentiality of polyester base films points out the need for prevention of accidental edge exposure. However, in normal practice aerial films are wound on flanged spools and loaded in cameras or magazines in the dark or in subdued light. Under these conditions edge fog, even with polyester base film, is not a problem. E. IMAGE DEFINITION The higher refractive index of Estar base compared with cellulose ester bases, may result in very slightly lower definition under some special circumstances. This is primarily because the ratio of the refractive indexes of the gel layer?Estar base combination is greater than this ratio for the gel layer?cellulose ester base combination. This effect is not significant in the case of camera negatives, as the image is normally formed by exposure of the emulsion surface. Resolution would only be affected by light penetrating the unproc- essed emulsion, with reflection from the back of the base or the back of an anti-halation gel layer. Thus, in camera negative films, the type of base has no significant effect on image quality. In the case of contact printing, in which the illumination comes through the base, optical characteristics of the base may have a small effect. Microscopic examination of resolution-chart images printed through both Estar and cellulose ester bases shows no differ- ence in sharpness, for film of normal resolution. As would be ex- pected, images printed with specular light are sharper than those printed with diffuse illumination, for both types of base. In the unusual case of successive generations of duplicating by contact printing, using film of very high resolving power (e.g., SO-l05), some small loss in definition occurs. The following table illustrates that with a very high resolution film, a greater loss occurs in contact printing by specular than by diffuse illumination. It also shows the difference in loss for the two types of bases. First Negative First Print Second Negative Specular Diffuse Specular Diffuse Cellulose Ester Base 390 lines/mm 360 360 330 330 Estar Polyester Base 390 lines/mm 330 360 270 330 Both before and after exposure and processing, the emulsion has some turbidity; consequently, some light is always traveling towards both surfaces at varying angles. It is this light that is multiply-reflected to produce the image degradation. . 1 1 Declassified in Part - Sanitized Copy Approved for Release 2012/09/11: CIA-RDP79B00873A001600010002-5 ? 1,1,716