1. Thermal Imaging and Law Enforcement
Ashraf Wilsily

2. 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

3. 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

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

5. 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.

6. 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

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

8. 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.

9. 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

10. 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

11. 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

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

13. 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