Flying - - Contents -

En­hanced-vi­sion sys­tems see what dan­gers lurk

If you’ve flown in re­duced vis­i­bil­ity or on a clear, moon­less night and won­dered what was ahead, you’re not alone. Pilots fly­ing air­craft equipped with an en­hanced vi­sion sys­tem re­ceive in­creased sit­u­a­tional aware­ness in­for­ma­tion de­liv­ered to the cock­pit in lim­ited-vis­i­bil­ity sit­u­a­tions both day and night.

Man­u­fac­tur­ers such as Max-viz, Kolls­man and Rock­well Collins pro­duce in­frared sen­sors like those in for­ward-look­ing in­frared (FLIR) cam­eras used by the mil­i­tary and law en­force­ment.

EVS in­frared cam­eras de­tect the heat of ob­jects to cre­ate a blackand-white im­age of the world ahead, whether it’s a per­son stand­ing on the ramp, moun­tains to ei­ther side of the ap­proach path or lights on the ac­tive run­way .

Typ­i­cal EVS com­po­nents in­clude one or more in­frared sen­sors, an im­age pro­ces­sor and a dis­play de­vice. The EVS cam­era is nor­mally placed in the nose cone of the air­craft, just be­neath the wind­shield or bot­tom of the nose.

Keep­ing the EVS sen­sors clean is not nor­mally a con­cern be­cause, un­like tra­di­tional cam­eras, in­frared units see past dirt and bugs to cre­ate a clear im­age. An EVS does use a heat­ing el­e­ment to pre­vent the buildup of ice.

The Max-viz 2300, as an ex­am­ple, adds be­tween two and five pounds to an air­craft’s empty weight and measures 2.8 inches in di­am­e­ter and 6.8 inches in length.

The MV 2300 uses two sep­a­rate sen­sors. A ther­mal de­tec­tor re­acts to long-wave in­frared (LWIR) light us­ing a vana­dium ox­ide (VOX) sen­sor to de­tect elec­tro­mag­netic waves in the 8- to 12-mi­cron range. The ther­mal de­tec­tor uses a 30-hertz re­fresh rate, cre­at­ing a 640-by-480-pixel res­o­lu­tion out­put in a black-and­white “video ap­pear­ing” for­mat. The ther­mal sen­sor is ca­pa­ble of de­tect­ing tem­per­a­ture changes of less than one-tenth of 1 de­gree Cel­sius.

The sec­ond el­e­ment, a run­way light de­tec­tor, is ac­tu­ally a com­ple­men­tary metal-ox­ide-semi­con­duc­tor (CMOS) vis­i­ble light sen­sor to de­tect elec­tro­mag­netic waves in the 400to 900-nanome­ter range, al­low­ing de­tec­tion of LED lights.

The MV 2300 sys­tem uses an im­age pro­ces­sor to con­trol dy­namic range and the blend­ing of vis­i­ble and in­frared images.

An EVS re­quires ei­ther a mul­ti­func­tion dis­play in­stalled in the panel or a head-up dis­play, usu­ally hung in front of the pi­lot’s eyes to dis­play the EVS im­agery.

EVS units come in two va­ri­eties: cooled and un­cooled. The first uses a cryo­geni­cally cooled IR de­tec­tor typ­i­cally us­ing a mid-wave, aka MWIR, to de­tect ra­di­a­tion in the 3to 5-mi­cron range.

Fly­ing through thick ma­rine fog, more en­ergy can be de­tected by the MWIR than the un­cooled LWIR. But on a cold, dark night, ther­mal en­ergy shifts to­ward longer wave­lengths, mak­ing an LWIR de­tec­tor in the 8- to 12-mi­cron range more ef­fec­tive.

Be­cause cooled and un­cooled de­tec­tors each have strengths, an EVS needs more sen­sors to see more. It’s the rea­son why the EVS trend to­day is to­ward blend­ing dif­fer­ent de­tec­tors in one sys­tem.


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