Thermal Imaging Thermal Imaging and Law and Law

EnforcementEnforcement

Ashraf WilsilyAshraf Wilsily

A Brief IntroductionA Brief Introduction ““Can you see?” –Can you see?” –Minority ReportMinority Report What is thermal imaging?What is thermal imaging?

– ““See” heat as it radiates from objectSee” heat as it radiates from object– All objects above 0K emit thermal IR energyAll objects above 0K emit thermal IR energy– Is it the same as the green images from Is it the same as the green images from

James Bond movies? James Bond movies? – IR theoryIR theory

How and why does it work?How and why does it work? LimitationsLimitations Application to Law EnforcementApplication to Law Enforcement

Radiation & IR TheoryRadiation & IR Theory Three methods by which heat flows from Three methods by which heat flows from

one object to another: radiation, one object to another: radiation, convection, conductionconvection, conduction

IR radiation, “beyond red”, or beyond IR radiation, “beyond red”, or beyond visiblevisible– Near IR (from .7Near IR (from .7m to 1.3m to 1.3m)m)– Mid IR (from 1.3Mid IR (from 1.3m to 3m to 3m)m)– Thermal IR (beyond 3Thermal IR (beyond 3m to microwave)m to microwave)

Only one related to sensation of heatOnly one related to sensation of heat

Every body emits energy from its surface Every body emits energy from its surface as electromagnetic wavesas electromagnetic waves

Heat transmittance between objects

Thermal profiles show “false color” (left). Night vision characterized by

green color (above).

How thermal imagers (IR cameras) workHow thermal imagers (IR cameras) work

Lens focuses IR light emitted by objects in viewLens focuses IR light emitted by objects in view Focused light is scanned by a phased array of Focused light is scanned by a phased array of

IR-detector elementsIR-detector elements Translation of data into electric impulsesTranslation of data into electric impulses Impulses sent to a signal-processing unit to Impulses sent to a signal-processing unit to

translate the info from elements into data for translate the info from elements into data for displaydisplay

Signal processing unit sends info to the display, Signal processing unit sends info to the display, where it appears as various “where it appears as various “false colorsfalse colors” ” depending on intensity of IR emissiondepending on intensity of IR emission– The combination of all impulses from all elements The combination of all impulses from all elements

creates the image: creates the image: thermal profilethermal profile

Basic Components of Thermal-Basic Components of Thermal-Imaging SystemImaging System

                                                                                          

                                                      

                                                                                                             

Daylight

At Night

IR imager

Thermal profiles show “false color”

Examples of thermal imagers

LimitationsLimitations

Cannot “see” through walls, or glassCannot “see” through walls, or glass– Exterior heat loss is measured firstExterior heat loss is measured first

Cannot see through clothingCannot see through clothing– If one is carrying a gun, the exterior of the If one is carrying a gun, the exterior of the

coat would appear “cooler” to the camera coat would appear “cooler” to the camera indicating a possible gun possessionindicating a possible gun possession

Parameters important in thermal imaging Parameters important in thermal imaging may not achieve desired performancemay not achieve desired performance– Temperature range, spectral range, accuracy, Temperature range, spectral range, accuracy,

resolution, maximum frame rate, etc.resolution, maximum frame rate, etc.

Law EnforcementLaw Enforcement Thermal Building ProfilesThermal Building Profiles

– Used in US to conduct thermal profiles of Used in US to conduct thermal profiles of buildings suspected of harboring illegal buildings suspected of harboring illegal growing operationsgrowing operations

– An airborne forward-looking IR unit or An airborne forward-looking IR unit or handheld thermal imaging camera is needed handheld thermal imaging camera is needed for such auditsfor such audits

– Relative temperature to other buildingsRelative temperature to other buildings– Marijuana processing generates lots of heat Marijuana processing generates lots of heat

from high-voltage bulbs that simulate from high-voltage bulbs that simulate sunlightsunlight

– Does it always work? Can account to this by Does it always work? Can account to this by using ‘extra’ insulationusing ‘extra’ insulation

Law Enforcement…Law Enforcement… Locating fugitivesLocating fugitives

– Can locate an escapee, an armed robber on foot or Can locate an escapee, an armed robber on foot or in a backyard at a distancein a backyard at a distance

Vehicle pursuitVehicle pursuit– Vehicle engines, tires, and brakes all emit heatVehicle engines, tires, and brakes all emit heat– Speeding increases this heat, making fugitives’ car Speeding increases this heat, making fugitives’ car

easier to distinguish among other vehicles on roadeasier to distinguish among other vehicles on road– Advantages? Endangering citizens less and police Advantages? Endangering citizens less and police

still able to track fleeing vehiclestill able to track fleeing vehicle

More on Law Enforcement…More on Law Enforcement… Disturbed surface scenarioDisturbed surface scenario

– Find large amounts of cash, drugs, and bodies buried in Find large amounts of cash, drugs, and bodies buried in the ground or hidden in structure walls or flooringthe ground or hidden in structure walls or flooring

– Differences in temp and moisture content are critical Differences in temp and moisture content are critical factors in their discoveriesfactors in their discoveries

– Can detect temp differences to 0.01Can detect temp differences to 0.01°°C & recognize C & recognize disturbed ground and patched wallboard even when disturbed ground and patched wallboard even when surface is camouflaged wellsurface is camouflaged well

Surveillance of marine and aerial suspectsSurveillance of marine and aerial suspects

Perimeter surveillancePerimeter surveillance

Suspect Marijuana grow house Locating fugitives at a distance

Vehicle pursuit Surveillance of marine and aerial suspects

SummarySummary New set of eyes to ‘see’ heatNew set of eyes to ‘see’ heat

Going beyond the visibleGoing beyond the visible

Many applications but extensively used Many applications but extensively used in law enforcementin law enforcement

Accepted in the US as evidence in Accepted in the US as evidence in courtscourts