A Multicriteria Approach to Exploring Combinations of External Surveillance Conditions Defining a Given NVD Working Range Value

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1 BULGARIAN ACADEMY OF SCIENCES CYBERNETICS AND INFORMATION TECHNOLOGIES Volume 9, No 4 Sofi 2009 Applictions A Multicriteri Approch to Exploring Combintions of Externl Surveillnce Conditions Defining Given NVD Working Rnge Vlue Dniel Borissov, Ivn Mustkerov Institute of Informtion Technologies, 1113 Sofi E-mils: dborissov@iit.bs.bg mustkerov@iit.bs.bg Abstrct: The working rnge is one of the most significnt night vision devices prmeter, given in ctlogue dtsheets. From user s point of view it is interesting to explore different combintions of externl surveillnce conditions defining given working rnge vlue of night vision devices. For this purpose, multicriteri optimiztion problem is formulted. The optimiztion problem solutions give combintions of mbient night illumintion, tmospheric trnsmittnce nd contrst between surveillnce trget nd the bckground, tht define the given detecting rnge vlue of night vision goggles by stnding mn The multicriteri nture of the optimiztion problems llows influencing the solutions by the user s preferences bout the expected externl surveillnce conditions vlues. The results of number of numericl experiments using rel dt re described. It is demonstrted tht there exist different externl surveillnce conditions combintions defining the given device working rnge. Keywords: Night vision devices, working rnge, externl surveillnce conditions, multicriteri optimiztion problem, numericl experiments. 1. Introduction Night vision technology, providing the bility for observtion t night, is one of the most fscinting technologies in use tody [1, 2]. The Night Vision Devices (NVD) hve their origin in the militry reserch nd development, but it is the non-militry pplictions tht hve led to the dvncement of this technology. Night vision is 102

2 becoming more nd more populr nowdys. There exist two different night vision technologies ech hving its own dvntges nd disdvntges low-light imge intensifying nd therml imging. The technology, bsed on the use of electronic imge intensifying technology, is used in most of the devices nd they re the object of investigtion in the pper. A wide rnge of night vision devices with vriety of their prmeters re vilble [3-8] to suit the vrious requirements for different pplictions [9]. The working rnge is one of the most significnt NVD prmeter. The working rnge, given in ctlogue dtsheets, is shown without mentioning the vlues of the externl surveillnce conditions for which it is vlid. The min gol of the pper is to develop n pproch to estimte numericlly the possible externl surveillnce conditions combintions, defining the given working rnge vlue. A stnding mn trget is considered nd the impct of mbient night illumintion, tmospheric trnsmittnce nd contrst between the trget nd bckground re investigted. Multicriteri tsk formultion for exploring combintions of externl surveillnce conditions, defining the given NVD working rnge vlue, is used. 2. Night vision nd externl surveillnce conditions The NVD bsed on electronic imge intensifying technology s the most populr type of NVD re chosen for the investigtions. There re mny night vision devices prmeters tht chrcterize their performnce, like: working rnge, field of view, imge qulity, spectrl response, weight, opertionl bttery life, etc. The visul performnce through night vision devices is function of mny prmeters such s: trget contrst, objective nd eyepiece lens focus, signl/noise of the imge intensifier tube, qulity of the imge intensifier nd NVG output luminnce to the eye [10]. The working rnge vlue is prcticlly the most importnt prmeter ffected significntly by externl surveillnce conditions mbient night illumintion, tmospheric trnsmittnce, contrst between trget nd bckground, trget type [11-13]. The influence of the externl surveillnce conditions on the NVD performnce cn be described shortly s: Ambient night illumintion the night vision technology using vilble light intensifying relies on the mbient light (strlight, moonlight, or sky glow from distnt mnmde sources, such s city lights, etc.). Atmospheric trnsmittnce depends on the surfce terrin nd the surroundings, ir temperture, tmospheric pressure, reltive humidity, number nd size distribution of tmospheric erosols, concentrtion of bnorml tmospheric constituents in the opticl pth such s smoke, dust, exhust fumes, nd chemicl effluents, nd refrctive indices of ll types of erosol in the opticl pth [14]. Contrst between the bckground nd surveillnce trget monochromtic contrst difference between the integrted trget nd bckground intensities. Surveillnce trget type different objects re to be observed under night conditions nd the lrger the object is, the esier it is to see. 103

3 3. Problem formultion The NVD working rnge vlue is result of complex dependency of NVD prmeters nd the externl surveillnce conditions. This reltionship cn be expressed nlyticlly using formul s developed nd described in [15, 16]: 0.07Din fоbττ o S δekаоb R = Σ m, MФmin.ph where: D in is the dimeter of the objective inlet pupil in m, f ob objective focl length in mm, τ а, τ о tmosphere nd objective trnsmittnce dimensionless prmeters, Ф min.ph Imge Intensifier Tube (IIT) photocthode limiting light flow in lm, δ IIT limiting resolution in lp/mm, S Σ IIT luminous sensitivity in A/lm, М signl-to-noise rtio of IIT (dimensionless prmeter), E mbient light illumintion in lx, K contrst dimensionless prmeters lso, nd А оb trget (surveillnce object) re in m 2. By substituting the re by the so clled reduced trget re A ' ob in m 2 different types of working rnge cn be clculted detection rnge, recognition rnge nd identifiction rnge [15]. From user s point of view it is interesting to know wht combintions of the externl surveillnce conditions vlues would give the working rnge dt listed in ctlogue dtsheets. To determine sets of different combintions of the externl surveillnce conditions vlues, for which the NVD working rnge cn be chieved, s shown in the ctlogue dt, multicriteri optimiztion problem is formulted: (1) subject to: 104 min E min K minτ 0.07 D f τ S δeτ KА' Σ R * MФ =, (2) in оb o ob min.ph l u (3) E E E, l u (4) τ τ τ, l u (5) K K K. where R * is the given device ctlogue stnding mn detection rnge in meters, E u, τ u, K u re upper nd lower E l, τ l, K l limits for the mbient light illumintion, tmosphere trnsmittnce nd contrst. 4. Numericl experiments The formulted multicriteri nonliner optimiztion problem (1)-(5) is used for numericl experiments to get combintions of vlues of the externl surveillnce conditions, stisfying equlity (2). For the purpose of numericl experiments the

4 most widely used type NVD, i.e., Night Vision Goggles (NVGs) re considered. Representtive NVGs [17] with the following ctlogue prmeters dt re used: imge intensifier tube Gen. 3 US with limiting resolution of δ = 68 lp/mm, photocthode sensitivity S Σ = A/lm, signl to noise rtio M = 25 nd photocthode sensitivity Φ min.ph = ; objective with inlet pupil dimeter of D in = m, focl length f ob = 26 mm nd objective trnsmittnce τ o = 0.8 ; s: NVG detecting rnge R * = 325 m. The prcticl vlues of externl surveillnce conditions prmeters re chosen night illumintion E in the intervl E 0.01; tmosphere trnsmittnce τ in the intervl 0.65 τ 0.80 ; contrst K between surveillnce trget nd bckground in the intervl 0.1 K 0.5 ; typicl stnding men trget with reduced trget re A ' ob = 0.72 m 2, The corresponding multicriteri optimiztion tsk is (6) min E min K minτ subject to: (7) E K τ = 325, (8) E 0.01, (9) 0.1 K 0.5, (10) 0.65 τ Using the weighted sum method [18], the originl problem is trnsformed to single criterion problem: (11) min ( we 1 ' + wk 2 ' + wτ 3 ' ) subject to constrints (8)-(10) nd (12) w i = 1, i E 0.01 K 0.5 τ 0.80 where E ' =, K ' = nd τ ' = re the normlized objective functions. The weighted sum method sclrizes set of objectives into single objective by pre-multiplying ech objective with usersupplied weight coefficient. The reltive importnce of ech objective function is reflected by those coefficients. 105

5 Experimentl results nd discussion. Using vriety of weight coefficients, reflecting user requirements bout the externl surveillnce conditions, three different optimiztion cses re solved. The first cse is bsed on objective function (11) nd restrictions (8)-(10) nd (12) nd considers the whole prcticl rnge of externl surveillnce conditions vlues. In the second cse some of the externl surveillnce conditions re limited in given boundries. The third cse is focused on combintions of externl surveillnce conditions where some of them re fixed with given vlues. The optimiztion tsks solutions supply externl surveillnce conditions combintions defining the given mn detection rnge for ech cse. First cse optimiztion solutions (considering the whole prcticl rnge of the externl surveillnce conditions) Tble Tble 1. Weight coefficients nd solution results for Cse 1 No w 1 w 2 w 3 E, lux K τ R, m The solution results in Tble 1 give different combintions for mbient night illumintion nd contrst between bckground nd trget. The tmosphere trnsmittnce hs reltively smll fesible intervl which defines the lowest possible vlue. Different weight coefficients (s reflection of user s importnce bout the externl surveillnce conditions) led to different combintion of externl surveillnce conditions, stisfying the given NVG mn detecting rnge. Second cse optimiztion solutions (considering limits for some externl surveillnce conditions) Tble 2. Tble 2. Weight coefficients nd solution results for Cse 2 ( 0.15 K 0.45, 0.7 τ 0.75 ) No w 1 w 2 w 3 E, lux K τ R, m When some preliminry informtion bout the expected vlues of the externl surveillnce conditions exists, they cn be restricted within some nrrower limits. This cse is numericlly tested, decresing the fesible intervls for the contrst K

6 nd tmosphere trnsmittnce τ, using the sme sets of weight coefficients s in the first cse. This reflects in optimiztion tsks solutions in Tble 2 defining different combintions of the surveillnce conditions for the given NVG mn detecting rnge. Third cse optimiztion solutions (considering tmospheric trnsmittnce with fixed vlue τ = 0.73 ) Tble 3. Tble 3. Weight coefficients nd solution results for Cse 3 ( τ = 0.73 ) No w 1 w 2 w 3 E, lux K τ R, m In some prcticl cses, some of the externl surveillnce conditions could be considered s known with fixed vlues. The pproch proposed ws tested with fixed vlue bout the tmospheric trnsmittnce τ = 0.73 using three different combintions of weight coefficients. The solution s results define different combintions of night illumintion nd contrst vlues to blnce the fixed tmospheric trnsmittnce τ vlue (Tble 3). It is possible to give fixed vlues for other externl surveillnce conditions to investigte the possible combintions stisfying the given NVG working rnge. Sometimes tht could led to unfesible optimiztion tsk formultion. Chnging the given fixed vlues nd experimenttion with them will help to overcome such kind of problems. 5. Summry nd conclusions The current pper proposes multicriteri optimiztion pproch for investigting different NVD externl surveillnce conditions combintions, defining the given NVD working rnge vlue. The NVD working rnge is one of the most significnt prmeters, given in ctlogue dtsheets. From user s point of view it is interesting to explore possible combintions of externl surveillnce conditions stisfying the given NVD working rnge vlue. For this purpose multicriteri optimiztion pproch is developed nd described. Three different optimiztion cses re explored. The first cse considers s fesible the whole prcticl rnge of externl surveillnce conditions vlues; in the second cse some of the fesible externl surveillnce conditions limits re nrrowed; the third cse is focused on combintions of externl surveillnce conditions where some of them re fixed with given vlues. Using vriety of weight coefficients, reflecting user s requirements towrds the externl surveillnce conditions importnce, number of numericl experiments for ech cse re conducted. The formulted multicriteri optimiztion problems solutions give combintions of mbient night illumintion, tmospheric trnsmittnce nd contrst between surveillnce trget nd the bckground tht define the given night vision goggles stnding mn detecting rnge vlue. The multicriteri nture of the optimiztion problems llows ffecting the solutions by 107

7 user s preferences bout the expected externl surveillnce conditions vlues. The numericl experiments, bsed on rel NVG prmeters dt, demonstrte tht there exist different externl surveillnce conditions combintions, defining the given device working rnge for ech tested cse. It should be pointed out tht it is possible to get unfesible optimiztion tsk formultion when restricting nd fixing vlues of some externl surveillnce conditions. Further experimenttion with other externl surveillnce conditions limits nd vlues should be done to overcome the infesibility. If prcticlly resoned, the proposed optimiztion tsks formultions could be modified, wekening equlity (2) to inequlities with upper nd lower limits. This will led to externl surveillnce conditions combintions defining NVD working rnge within given limits. The multicriteri tsks formultions could be solved by other user preferble methods. The numericl experimenttion shows tht the proposed multicriteri optimiztion pproch could be used for determining the resonble NVD externl surveillnce conditions combintions, stisfying the given s prmeter dt NVD working rnge. Acknowledgments. The investigtions in this work re supported by IIT-BAS Reserch Projects No nd by the Europen Socil Fund nd Bulgrin Ministry of Eduction, Youth nd Science under the Opertive Progrmme Humn Resources Development, Grnt BG051PO001/07/3.3-02/7. R e f e r e n c e s 1. D s, S., Y-L, Z h n g, W. K. K r e b s. Color Night Vision for Nvigtion nd Surveillnce. In: Proc. of the Fifth Joint Conference on Informtion Sciences. J. Sutton nd S. C. Kk, Eds. Atlntic City, New York, M c u d, T., G. C r i g, R. S. A l l i s o n, P. G u t e r m n, P. T h o m s, S. J e n n i n g s. Detection of Motion-Defined Form Using Night Vision Goggles (Accessed July 2009) Night Vision Equipment (Accessed July 2009) Night Vision Goggles, Binoculrs, Monoculrs, Rifle Scopes (Accessed July 2009) Night Vision Devices: Monoculrs, Binoculrs, Goggles, Scopes, Lsers (Accessed July 2009) ITT Night Vision (Accessed July 2009) Night Vision Goggles, Rifle Scopes & Monoculrs (Accessed July 2009) Night Vision Optics by ATN: Night Vision Goggles, Scopes, Binoculrs & Monoculrs (Accessed July 2009) S h w l e e, W. The Drk nd Mysterious World of Night Vision: Understnding ANVIS/NVIS/NVG Technology in the Cockpit. Avionics News, Februry 2008, Mrsco, P. L., H. L. Tsk. The Impct of Trget Luminnce nd Rdince on Night Vision Device Visul Performnce Testing. In: Proc. Helmet- nd Hed-Mounted Displys VIII: Technologies nd Applictions. Clrence E. Rsh, Colin E. Reese, Eds. Vol. 5079, 2003, Night Vision Goggle (NVG) Comptible Light Sources. SAE Aerospce Recommended Prctice, ARP4168,

8 12. Lighting, Aircrft, Night Vision Imging System (NVIS) Comptible, MIL-STD-3009, 2 Februry M u s l, A. K., A. K. J i s w l. Effect of Imge Intensifier Tube Equivlent Bckground Illumintion on Rnge Performnce of Pssive Night Sight. Defence Science Journl, Vol. 57, 2007, No 6, S m i t h, C. M. Detection of Specil Opertions Forces Using Night Vision Devices, ORNL/TM- 2001/172 (Accessed August 2009) B o r i s s o v, D., I. M u s t k e r o v. A Working Distnce Formul for Night Vision Devices Qulity Preliminry Informtion. Cybernetics nd Informtion Technologies, Vol. 6, 2006, No 3, B o r i s s o v, D., I. M u s t k e r o v. A Generlized Optimiztion Method for Night Vision Devices Design Considering Stochstic Externl Surveillnce Conditions. In: Applied Mthemticl Modelling. Vol. 33. Elsevier Inc., 2009, Dul-Tube Goggle D-321G Genertion 3 (Accessed October 2009). e=nvm&product_code=d-321g-a&ctegory_code=bg 18. Multi-Objective Optimiztion Using Evolutionry Algorithms. Klynmoy Deb, Wiley, ISBN: , p. 109

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