Im­age In­ten­si­fiers — The Key to Night Vi­sion

Im­age in­ten­si­fi­ca­tion is the ba­sis of night vi­sion thus an im­age in­ten­si­fier is a de­vice for in­creas­ing the in­ten­sity of ex­ist­ing light in the en­vi­ron­ment for an op­ti­cal sys­tem to en­able to op­er­ate in low-light con­di­tions

SP's LandForces - - FRONT PAGE - Lt Gen­eral Naresh Chand (Retd)

Im­age in­ten­si­fi­ca­tion is the ba­sis of night vi­sion thus an im­age in­ten­si­fier is a de­vice for in­creas­ing the in­ten­sity of ex­ist­ing light in the en­vi­ron­ment for an op­ti­cal sys­tem to en­able to op­er­ate in low-light con­di­tions.

IT HAS AL­WAYS BEEN the dream of all armies to be able to carry out op­er­a­tions by day and night in all weather con­di­tions. It was dur­ing World War II and the Korean War that the de­vel­op­ment of im­age-in­ten­si­fi­ca­tion tech­nol­ogy be­gan to help the snipers to en­gage their tar­gets at night or in bad weather con­di­tions.

Im­age in­ten­si­fiers have made this dream come true by mak­ing night into day. Im­age in­ten­si­fiers cou­pled with ther­mal im­agers have given birth to mul­ti­ple mil­i­tary ap­pli­ca­tions for night vi­sion like sur­veil­lance, tar­get ac­qui­si­tion, sight­ing de­vices for aim­ing, bat­tle dam­age as­sess­ment and in­tel­li­gence gath­er­ing. Th­ese ap­pli­ca­tions are ap­pli­ca­ble across all plat­forms rang­ing from the in­fantry soldier to ar­tillery guns, tanks; aerial and naval plat­forms.

Im­age In­ten­si­fier How it works?

Im­age in­ten­si­fi­ca­tion is the ba­sis of night vi­sion thus an im­age in­ten­si­fier is a de­vice for in­creas­ing the in­ten­sity of ex­ist­ing light in the en­vi­ron­ment for an op­ti­cal sys­tem to en­able to op­er­ate in low-light con­di­tions. Th­ese con­di­tions could be night; light from flu­o­res­cence of ma­te­ri­als in X-rays or gamma rays; for con­ver­sion of non-vis­i­ble light sources such as near-in­frared or short wave in­frared to a vis­i­ble im­age. Sim­ply ex­plained-the im­age in­ten­si­fier is a vacuum tube in which im­age in­ten­si­fi­ca­tion is achieved by a com­plex con­ver­sion of en­ergy par­ti­cles. The sys­tem works by col­lect­ing pho­tons through an ob­jec­tive lens which are then con­verted into elec­trons through a pho­to­cath­ode. Their elec­tri­cal en­ergy is then in­creased by a de­vice called mi­cro-chan­nel plate (MCP) which is then con­verted back into light through a phos­phor screen (that is why the im­age ap­pears green­ish in colour) and the fi­nal im­age can be viewed through an eye­piece lens. Pho­ton is a par­ti­cle rep­re­sent­ing a quan­tum of light or other elec­tro­mag­netic ra­di­a­tion. The sys­tem is pro­vided power with a so­phis­ti­cated minia­turised power sup­ply sys­tem. MCP is a key com­po­nent where the elec­tron am­pli­fi­ca­tion takes place. It is a thin disc that con­tains mil­lions of densely spaced chan­nels. When the elec­trons pass through th­ese chan­nels, they are mul­ti­plied man­i­fold and strike the phos­phor with greater en­ergy which is thou­sands time brighter than the orig­i­nal im­age picked up in less/no light con­di­tions.

De­vel­op­ment in Im­age In­ten­si­fier

Tech­nol­ogy. Early snipers used im­age con­vert­ers (sniper­scopes) that re­quired an in­frared light source to il­lu­mi­nate their tar­get and is now called Gen­er­a­tion (Gen) 0. Fur­ther de­vel­op­ment took place when the starlight scope was de­vel­oped dur­ing the early 1960s which used three im­proved im­age-in­ten­si­fier tubes which pro­duced a clear cen­tre im­age with a dis­tor­tion at the pe­riph­ery. This was called Gen One. Gen Two was de­vel­oped in the late 1960s with a ma­jor break­through with the de­vel­op­ment of the MCP. The pho­to­cath­ode process was fur­ther re­fined with the S-25 cath­ode re­sult­ing in much higher photo re­sponse. The size and weight was also re­duced which en­abled them to be used with head- and hel­met-mounted gog­gles. In the mid-1970s, ad­vance pho­to­cath­ode tech­nol­ogy was de­vel­oped in Gen 3 which in­creased the tube’s sen­si­tiv­ity dra­mat­i­cally; par­tic­u­larly in the near-IR re­gion. This re­sulted in longer ranges for the sys­tem. How­ever the process of de­vel­op­ment is work in progress. Some key de­vel­op­ments are minia­ture high­volt­age power sup­ply sys­tem and in­creas­ing the re­li­a­bil­ity in ex­cess of 15,000 hours with­out much degra­da­tion. Some ex­am­ples are:

PHOTONIS. PHOTONIS has de­vel­oped INTENS im­age in­ten­si­fier tube which en­ables night vi­sion ca­pa­bil­i­ties in dark mil­i­tary mis­sion con­di­tions such as deep moun­tain val­leys and jun­gle ter­rain. The tube of­fers band­width sen­si­tiv­ity from 4001000 nano me­tre and pro­vides a 40 per cent in­crease in de­tec­tion, recog­ni­tion, and iden­ti­fi­ca­tion (DRI) over pre­vi­ous tubes. INTENS is equipped with an Auto-Gat­ing power sup­ply for op­er­a­tions in dy­namic light con­di­tions, a high-con­trast green P22 phos­phor and a sig­nal to noise ra­tio of 30. In ad­di­tion, the INTENS tube has an op­er­a­tional life­time of over 10,000 hours.

ITT In­dus­tries. ITT has de­vel­oped a new high-per­for­mance im­age in­ten­si­fier called Pin­na­cle for use in ex­ist­ing avi­a­tion and ground night vi­sion sys­tems. Pin­na­cle pro­vides sub­stan­tial per­for­mance in­creases in low light de­tec­tion, high light res­o­lu­tion and in­tra-scene dy­namic range (the abil­ity to see de­tail in dark ar­eas of a scene where bright cul­tural light­ing is present -- for ex­am­ple, into a dark al­ley where street­lights are also in the scene). The new Pin­na­cle in­ten­si­fier can be used in all avi­a­tion and ground sys­tems that cur­rently ac­cept 18 mm im­age in­ten­si­fiers. The im­proved per­for­mance is pos­si­ble due to a new high-per­for­mance MCP, a newly de­signed gat­ing power sup­ply and im­proved man­u­fac­tur­ing process.

Ther­mal Imag­ing Tech­nolo­gies

Ther­mal Imag­ing (TI) is not re­lated to im­age in­ten­si­fi­ca­tion but en­ables night vi­sion. It does not rely on ex­ist­ing light through which the hu­man eye can see a im­age but de­tects ob­jects based on heat emit­ted by them. The warmer the ob­ject, the more in­frared long-wave light it ra­di­ates and the more de­tectable it is. How­ever it does not have high res­o­lu­tion of the im­age as com­pared to im­age in­ten­si­fier of the sim­i­lar field of view. A spe­cial lens fo­cuses the in­frared light emit­ted by all of the ob­jects in view which is scanned by in­frared-de­tec­tor el­e­ments which in turn form a de­tailed tem­per­a­ture pat­tern called a ther­mo­gram. The de­tec­tor ar­ray works very fast and ob­tains the tem­per­a­ture in­for­ma­tion in about onethir­ti­eth of a se­cond to make the ther­mo­gram. The ther­mo­gram is trans­lated into elec­tric im­pulses which are then con­verted into dis­play data where it ap­pears as var­i­ous col­ors de­pend­ing on the in­ten­sity of the in­frared emis­sion. There are two com­mon types of ther­mal-imag­ing de­vices which are Un-cooled and Cryo­geni­cally cooled. Un-cooled is the most com­mon TI de­vice which can op­er­ate at room tem­per­a­ture, is com­pletely quiet and ac­ti­vates im­me­di­ately. How­ever there have been crit­i­cal de­vel­op­ments in un­cooled ther­mal im­agers with the use of vana­dium ox­ide and amor­phous sil­i­con which have made them suit­able for head-mounted ap­pli­ca­tions. Cryo­geni­cally cooled is more ex­pen­sive but has an in­cred­i­ble res­o­lu­tion and sen­si­tiv­ity that re­sult from cool­ing the el­e­ments. Cryo­geni­cal­ly­cooled sys­tems can dis­cern a dif­fer­ence as small as 0.1 C from more than 300 m away, which is enough to tell if a per­son is hold­ing a gun at that dis­tance.

Com­bi­na­tion of Im­age In­ten­si­fiers and Ther­mal Im­agers

Night vi­sion de­vices would be­come more ef­fec­tive if the im­age in­ten­si­fier and the ther­mal im­ager is com­bined to bring out the best at­tributes of both. Ear­lier the ther­mal im­agers had greater size, weight and power (SWaP) con­sump­tion thus it was not prac­ti­cal to use them in user mounted ap­pli­ca­tions like night vi­sion gog­gles (NVG). How­ever ad­vances in re­cent years with un­cooled ther­mal im­agers have greatly im­proved th­ese fea­tures mak­ing them more suit­able for head-mounted ap­pli­ca­tions. This has re­sulted in Sen­sor Fu­sion.

Sen­sor fu­sion. Sen­sor fu­sion com­bines the re­spec­tive strengths of im­age in­ten­si­fier and ther­mal imag­ing tech­nolo­gies into one de­vice. Such a com­bi­na­tion en­ables a user to view a much greater part of the light spec­trum which can span from vis­i­ble to near­in­frared to long-wave in­frared. Thus the user can view the in­for­ma­tion from both the vis­i­ble and ther­mal spec­trums through a sin­gle de­vice which gives him a greater ad­van­tage while car­ry­ing out mil­i­tary, se­cu­rity and law en­force­ment du­ties. This type of sen­sor fu­sion has led to the de­vel­op­ment of new night-vi­sion tech­nolo­gies and de­vices like the en­hanced night-vi­sion gog­gle (ENVG) that com­bines a ther­mal im­ager with an im­age in­ten­si­fier. The im­age in­ten­si­fier works like a stan­dard NVG in this sys­tem but im­age from the ther­mal sen­sor is through a video dis­play. Both the in­puts are then op­ti­cally over­laid to pro­vide a fused im­age. De­vel­op­ments are on to com­bine the video out­put of a ther­mal im­ager di­rectly with the video out­put of an elec­tronic out­put im­age in­ten­si­fier. Th­ese new de­vices would then dis­play a com­plete dig­i­tally fused im­age through HMD (head-mounted/hel­met dis­play) in a de­vice known as the dig­i­tally en­hanced night-vi­sion gog­gle (ENVG-D).

L-3’s AN/PVS-31 BNVD. This is a com­pact, light­weight, Gene III dual-tube gog­gle with an er­gonomic low-pro­file de­sign to pro­vide bet­ter sit­u­a­tional aware­ness than a sin­gle-tube gog­gle. Its twin-tube de­sign pro­vides pro­tec­tion in the field against fail­ure or dam­age ver­sus a sin­gle-tube de­vice. L-3 In­sight de­signed the AN/PVS-31 BNVD to in­crease sys­tem res­o­lu­tion, re­duce head­borne weight, im­prove sys­tem cen­tre of grav­ity and im­prove sit­u­a­tional aware­ness. Har­ris’ AN/PVS-14 Monoc­u­lar Night Vi­sion De­vice. AN/PVS-14 is de­signed for use by the in­di­vid­ual soldier in a va­ri­ety of ground-based night op­er­a­tions. It fea­tures the su­pe­rior per­for­mance of the Gen 3 F9815 im­age in­ten­si­fier tube with a vari­able gain con­trol to achieve an op­ti­mum bal­ance in the im­ages seen by both eyes. For weapon firing, the AN/PVS-14 can be mounted on a MIL-STD-1913 weapon rail be­hind a stan­dard col­li­mated dot sight. The Knight Vi­sion® PVS-22 Clip-On

Night Vi­sion Weapon Sight. PVS-22 uses the lat­est high per­for­mance Gen 3 in­ten­si­fier tube in a proven de­sign, where the cata­diop­tric lens (re­frac­tion and re­flec­tion are com­bined in an op­ti­cal sys­tem) pro­vides high per­for­mance light col­lec­tion with an ef­fec­tive f/1.2 in a light weight op­tic. The PVS-22 Weapon Sight is ap­pro­pri­ate for front line ri­fles such as the M4 Car­bine, M16A2/A4, M249, M14, and day sights with mag­ni­fi­ca­tion up to 10x. Night Vi­sion De­vices’ MINI BNVD AA

18mm. MINI BNVD AA 18mm is Dual Tube Night Vi­sion Gog­gle with Sin­gle Gain Con­trol. With a sys­tem weight of about 440 gm, the MINI BNVD is the light­est fully func­tional dual tube gog­gle in the world, which uti­lizes 18mm Gen 2/3 Im­age In­ten­si­fiers and in­cludes im­por­tant fea­tures such as a fully fo­cus­ing eye­piece and a fo­cus­able IR Il­lu­mi­na­tor.

En­hanced Night Vi­sion Gog­gleBinoc­u­lar (ENVG-B) Pro­gramme

To op­er­ate more ef­fec­tively at night, U.S. Army has given $391.8 mil­lion three-year con­tract to L-3 In­sight dur­ing May, 2018 for the ENVG-B. The ENVG fam­ily rep­re­sents hel­met-mounted night-vi­sion gog­gles that blend im­age in­ten­si­fi­ca­tion and long wave in­frared sen­sors for com­bat at night, in bad weather, and in smoke and dust. Har­ris and L-3 In­sight are build­ing ENVG II, while BAE Sys­tems and DRS are build­ing ENVG III. ENVG III weapon sights also has a im­proved res­o­lu­tion and a wider field of view which en­ables rapid tar­get ac­qui­si­tion.

Com­bi­na­tion of ENVG III and Fam­ily of Weapons Sights-In­di­vid­ual (FWS-I) tech­nol­ogy

The FWS-I, when mounted on a soldier’s weapon, will trans­mit its sight pic­ture through ra­dio to the ENVG III, which is mounted on a soldier’s hel­met. The FWS-I is de­signed for the M4 and M16 ri­fles, and can mount on those ri­fles in front of day sights that have al­ready been bore-sighted. The ENVG will com­bine ther­mal imag­ing with im­age in­ten­si­fi­ca­tion tech­nol­ogy. A va­ri­ety of modes will al­low soldiers to see in their gog­gles only the im­age from the ENVG III it­self, only the im­age from the FWS-I, or a com­bi­na­tion of the two. Us­ing a ‘pic­ture-in-pic­ture’ mode, the im­age from the FWS-I is dis­played at the bot­tom right of the im­age that is com­ing from the gog­gle. This com­bines the rapid tar­get ac­qui­si­tion tech­nol­ogy and can be ef­fec­tively be used for sur­veil­lance, aim­ing weapons dur­ing day­light, dark­ness, ad­verse weather and dirty bat­tle­field con­di­tions. This sys­tem should be with the U.S. Army by the first quar­ter of 2019.

L-3’s AN/PSQ-20B ENVG L-3 In­sight.

AN/PSQ-20B ENVG is a hel­met-mounted dual wave­band monoc­u­lar which en­ables the user to view im­ages through one eye, but not through two eyes as a binoc­u­lar de­vice can. The AN/PSQ-20B ENVG pro­vides im­proved tar­get­ing and iden­ti­fi­ca­tion by fus­ing im­age in­ten­si­fi­ca­tion tech­nol­ogy with ther­mal im­agery to bring out the best in both sen­sors.

In­dian Per­spec­tive Bharat Elec­tron­ics Limited Op­tronic De­vices Ltd (BELOP)

Im­age In­ten­si­fier Tube man­u­fac­tur­ing fa­cil­ity BEL.

BELOP (for­merly BEL DELFT) is an fully owned sub­sidiary of BEL which started man­u­fac­tur­ing Gen2 Im­age In­ten­si­fiers in col­lab­o­ra­tion with and as a Joint Ven­ture with BV DELFT Nether­lands in 1994. This was aimed at hav­ing indige­nous ca­pa­bil­ity in In­dia for such crit­i­cal tech­nolo­gies. Sub­se­quently, the tech­nol­ogy was up­graded to Su­per Gen­er­a­tion and Hy­per Gen­er­a­tion grade with in-house de­vel­op­ments. In 2012, the plant was up­graded to pro­duce XD-4 II Tubes with tech­ni­cal know-how from PHOTONIS, France, and about 40,000 tubes were sup­plied. The plant is presently be­ing up­graded to XR-5 grade with a ca­pac­ity to pro­duce more than 30,000 Im­age In­ten­si­fier Tubes per year. BEL also has plans to pro­duce MCP in­dige­nously with ToT from PHOTONIS once the XR-5 is fully es­tab­lished.

Tata Ad­vanced Sys­tems Limited (TASL)

Night Vi­sion De­vices is one of the ar­eas of strate­gic in­ter­est for Tata Ad­vanced Sys­tems Limited (TASL). TASL has en­tered into a part­ner­ship with Ex­elis Inc., the world leader in Gen 3 Im­age In­ten­si­fi­ca­tion based NVDs, to man­u­fac­ture and sup­ply th­ese sys­tems to In­dian De­fence mar­ket. As part of the drive to­wards achiev­ing in­di­geni­sa­tion, TASL has set up a pro­duc­tion fa­cil­ity in In­dia, for assem­bly and man­u­fac­ture of sub-as­sem­blies and com­plete sys­tems.

PHO­TO­GRAPH: US Army

The AN/PSQ-20 En­hanced Night Vi­sion Gog­gle (ENVG) pro­vides in­creased ca­pa­bil­ity by in­cor­po­rat­ing im­age in­ten­si­fi­ca­tion and long-wave in­frared sen­sors into a sin­gle, hel­met-mounted pas­sive de­vice.

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