Applications & Uses
Forensics investigators use infrared photography to see things in a crime scene that are invisible to the eye. TNO, an independent research organization, conducted tests on a sample crime scene in February 2010. They compared a regular photograph to an infrared photograph taken at the same time and found some interesting results. In the regular photograph, a man can be seen lying on an average living room floor with a switched-off computer monitor in front of him – there is very little visible to the eye that would be helpful in investigating this crime. However, in the infrared photograph, a lot more becomes clear. A key ring can be seen in the man’s pocket, distinguished in a different color through his jeans, and heat is visible around the monitor showing that it had been switched off in the past hour-and-a-half. Not only this, but the scientist in charge of the tests, Dr Miranda van Iersel, discovered that at room temperature and humidity, infrared photographs can pick up traces of soil up to four hours after it has been removed, and drops of water for up to 22 hours.
In infrared photographs, biological waste such as urine, blood and sperm can also be seen despite being invisible to the naked eye. As with the above examples, this is because infrared photography can register the difference in temperature between an object and its environment.