Dual-band infrared camera systems allow viewing and comparison of the 3-5µ and 8-12µ spectrum regions, improve visibility at sunrise/sunset and help distinguish between targets and decoys. They also enhance the ability to defeat many IR countermeasures such as smoke, camouflage and flares. As dual band 3rd generation FLIR systems progress, we introduce coatings for these systems. This paper describes advanced dual band coatings for the 3-5µ and 8-12µ spectrum regions, with reference to single band coatings. Theoretical and measured designs are shown for ZnSe, ZnS, Ge and IG-6 substrates. Triple band AR coatings with additional transmittance at 1.06µ are also demonstrated.
Diamond Like Carbon (DLC) or Hard Carbon (HC) single layer coatings on optical substrates are commonly used.
As a single layer, the resulting average reflectance in different spectral ranges (about 2.5% in the 3-5 μm region)
needs improvements. We propose multilayer coatings having a DLC upper layer applied on Si, Ge and other
materials. These coatings result in an average reflection of less than 0.5% in either the 3.4-5 μm or the 8-11.5 μm
regions. The average transmittance in these regions is more than 97%. The durability is comparable to single layer
DLC coatings. These coatings are suitable to front surface FLIR lens assemblies. The effect on the performance of a
zoom lens assembly and the reduction of the Narcissus effect is shown.
A durable Interference Filter for 1.65 (mu) with peak transmittance of above 90% is shown. The filter consists of Si and SiO2 layers on glass, with a SiO2 top layer for additional durability. Applying on the other side of the substrate an edge filter (long wave pass filter) with the same materials, resulted with a large blocking spectral region, without the use of an absorbing glass substrate.
Laser induced chemical vapor deposition (LCVD) of silicon nitride and silicon dioxide single and double layers have been investigated using excimer laser operating at a wavelength of 193 nm. The composition of silicon nitride which was formed in SiH4/NH3 gas mixture was nearly stochiometric having a refractive index of 1.8 - 1.9 and contained small amount of hydrogen. Deposition of silicon dioxide was investigated using SiH4/N2O. Using this gas mixture the film composition depended strongly upon the SiH4/N2O ratio. At high ratio the film formed was silicon oxynitride, which contained both Si-N and Si-O bonds. The film also contained small amount of Si-H bonds. Decreasing SiH4/N2O ratio led to the formalin of pure silicon dioxide with a refractive index of 1.45. A double layer coating of both silicon nitride and silicon dioxide resulted in the formation of antireflection coating with a reflectivity of about 0.5% at 750 nm.
A fiber optic radiometer based on a cooled photonic detector was designed and constructed. The radiometer is capable of measuring in real time the temperature of tissue irradiated with a CO2 laser. A silver halide IR fiber is used to deliver the CO2 laser radiation to the target and also to deliver the thermal radiation emitted from the target back to the detector. Two methods of measurements were examined, both of which solve the problem of detector blinding by reflected CO2 radiation. A theory of operation for this silver halide fiber optic radiometer, based on lock-in amplifier techniques, is presented. A short discussion of the radiometer design and construction is given. This work forms a basis for the subject of measuring, in real time, fast radiometric signals caused by CO2 laser irradiation. Such a radiometer is very useful when dealing with pulsed photo thermal radiation with 10.6-μm CO2 laser radiation. This technique is very useful in medicine and industry.
A fiber optic radiometer based on a cooled photonic detector was designed and constructed. The radiometer was capable of measuring in real time the temperature of a tissue irradiated with CO2 laser. A silver halide I.R. fiber was used to deliver the CO2 laser radiation needed to irradiate the target, and also to deliver the thermal radiation emitted from the target back to the detector. Two methods of measurements were examined, both of which solve the problem of the reflected CO2 radiation which blinds the detector. A theory for silver halide fiber optic radiometer based on lock in amplifier techniques is presented. Discussion of the radiometer design and construction is given. This work can be a good basis for the subject of measuring, in real time, radiometric signals caused by CO2 laser irradiation. Such a radiometer is of great use, when dealing with Photo Thermal Radiation, P.T.R., with 10.6 micrometers , CO2 laser wave length, which is very useful in medicine and industry.
A bearnsplitting assembly that divides a single visible beam into
three channels was designed, developed and produced. Each channel
receives a spectrally balanced beam with equal intensity and color
differences. The spectral and intensity balancing was achieved by
application of two neutral bearrisplitters at 4S angle of incidence
and a third surface with a total internal reflection (TIR). A
simple method to design neutral dielectric bearnsplitters is shown
and the design considerations are described.
This bearrisplitter is particularly suitable for dividing a single
beam into biocular observation in the case where the dimensions of
the beaxnsplitting element is limited.
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