Thermal Imaging and Law Enforcement Ashraf Wilsily

A Brief Introduction “Can you see?” –Minority Report What is thermal imaging? “See” heat as it radiates from object All objects above 0K emit thermal IR energy Is it the same as the green images from James Bond movies? IR theory How and why does it work? Limitations Application to Law Enforcement The invisible has been a mystery for so long. Questions arise on what we don’t see. As one of the actors of the movie says, “Can you see?” Well, it is the goal of this presentation to present “seeing” the invisible Now before letting your imagination take off, we will be seeing ‘heat”. This is the purpose of thermal imaging. As heat is radiated from an object, we can detect it Are these cameras like night googles in James Bond movies? No, “greenish” images are “image intensification” technology. These amplify available light to simulate daylight Thermal imaging does not rely on visible light, produces a black and white image called “thermal profile” that highlights the temp differences of objects

Radiation & IR Theory Three methods by which heat flows from one object to another: radiation, convection, conduction IR radiation, “beyond red”, or beyond visible Near IR (from .7mm to 1.3mm) Mid IR (from 1.3mm to 3mm) Thermal IR (beyond 3mm to microwave) Only one related to sensation of heat Every body emits energy from its surface as electromagnetic waves Radiation – most powerful, with speed of light (eg from sun to earth) Convection – faster than conduction as in liquid or gas Conduction – heat moving in a solid It is the function of thermal imagers to capture this radiation

Heat transmittance between objects Thermal profiles show “false color” (left). Night vision characterized by green color (above).

How thermal imagers (IR cameras) work Lens focuses IR light emitted by objects in view Focused light is scanned by a phased array of IR-detector elements Translation of data into electric impulses Impulses sent to a signal-processing unit to translate the info from elements into data for display Signal processing unit sends info to the display, where it appears as various “false colors” depending on intensity of IR emission The combination of all impulses from all elements creates the image: thermal profile It takes 1/30 of a second to produce the thermogram This info is obtained from several 1000 pts in field of view of the detector array The signal processing unit is a circuit board with a chip that does that translation The IR camera measures and displays a “thermal profile” of objects in relation to temperature of the surrounding objects. So a person, warmer than the surrounding air may appear “white”, while cooler surrounding air or buildings will appear in varying shades of gray.

Basic Components of Thermal-Imaging System                                                                                                                                                  1) Lens focuses IR light emitted by objects in view 2) Focused light is scanned by a phased array of IR-detector elements 3) Translation of data into electric impulses 4) Impulses sent to a signal-processing unit to translate the info from elements into data for display 5) Signal processing unit sends info to the display, where it appears as various “false colors” depending on intensity of IR emission The combination of all impulses from all elements creates the image: thermal profile

Examples of thermal imagers Daylight                                                                                                               Thermal profiles show “false color” At Night IR imager

Limitations Cannot “see” through walls, or glass Exterior heat loss is measured first Cannot see through clothing If one is carrying a gun, the exterior of the coat would appear “cooler” to the camera indicating a possible gun possession Parameters important in thermal imaging may not achieve desired performance Temperature range, spectral range, accuracy, resolution, maximum frame rate, etc.

Law Enforcement Thermal Building Profiles Used in US to conduct thermal profiles of buildings suspected of harboring illegal growing operations An airborne forward-looking IR unit or handheld thermal imaging camera is needed for such audits Relative temperature to other buildings Marijuana processing generates lots of heat from high-voltage bulbs that simulate sunlight Does it always work? Can account to this by using ‘extra’ insulation

Law Enforcement… Locating fugitives Vehicle pursuit Can locate an escapee, an armed robber on foot or in a backyard at a distance Vehicle pursuit Vehicle engines, tires, and brakes all emit heat Speeding increases this heat, making fugitives’ car easier to distinguish among other vehicles on road Advantages? Endangering citizens less and police still able to track fleeing vehicle

More on Law Enforcement… Disturbed surface scenario Find large amounts of cash, drugs, and bodies buried in the ground or hidden in structure walls or flooring Differences in temp and moisture content are critical factors in their discoveries Can detect temp differences to 0.01°C & recognize disturbed ground and patched wallboard even when surface is camouflaged well Surveillance of marine and aerial suspects Perimeter surveillance

Surveillance of marine Suspect Marijuana grow house Locating fugitives at a distance Surveillance of marine and aerial suspects Vehicle pursuit

Summary New set of eyes to ‘see’ heat Going beyond the visible Many applications but extensively used in law enforcement Accepted in the US as evidence in courts