427-0075-01-12 Version 110 November 2017 42
2 Basic Operation and Configuration
2.5 Thermal Imaging Overview
PT-602CZ HD Only—When power is applied to the PT-602CZ HD camera, a compact integral Stirling
cooler (also known as a cryocooler) starts automatically. The cryocooler makes an audible noise when
it is operating, and requires up to 8 minutes to cool the thermal imager down to its operating
temperature. When cooling down, the thermal video image shows a blue screen with the note:
Unit cooling, kindly wait.
The thermal camera makes an image based on temperature differences. In the thermal image, by
default the hottest item in the scene appears as white and the coldest item is black, and all other items
are represented as a gray scale value between white and black.
It may take some time to get used to the thermal imagery from the camera, especially for someone
who only has experience with normal daylight cameras. Having a basic understanding of the
differences between thermal and daylight cameras can help with getting the best performance from the
thermal camera.
Both thermal and daylight cameras have detectors (pixels) that detect energy. One difference between
thermal and daylight cameras has to do with where the energy comes from to create an image. When
viewing an image with an ordinary camera, there has to be some source of visible light (something hot,
such as the sun or lights) that reflects off the objects in the scene to the camera. The same is true with
human eyesight; the vast majority of what people see is based on reflected light energy.
On the other hand, the thermal camera detects energy that is
directly radiated from objects in the scene. Most objects in
typical surroundings are not hot enough to radiate visible light,
but they easily radiate the type of infrared energy that the
thermal camera can detect. Even very cold objects, like ice
and snow, radiate this type of energy.
The camera is capable of sensing very small temperature
differences, and produces a video image that typically has
dramatic contrast in comparison to daylight cameras. This
high contrast level from the thermal video enables intelligent
video analytic software to perform more reliably.
The performance of the camera varies throughout the day. Right after sunset, objects warmed by the
sun will appear warmest. Early in the morning, many of these objects will appear cooler than their
surroundings, so be sure to look for subtle differences in the scene, as opposed to just hot targets.
While the imagery on the monitor may at first look similar to ordinary black and white daylight video,
experience with the camera in varying conditions and seasons will lead to an appreciation of the
characteristics that make thermal imaging distinct. A few tips on how to interpret some of the imagery
may help to make the most of the system.
The camera senses small differences in apparent radiation from the objects in view, and displays them
as either white (or lighter shades of gray) for warmer objects, and black (or darker shades of gray) for
colder objects. This is why hot objects such as parts on an engines and exhaust pipes appear white,
while the sky, puddles of water and other cold objects appear dark (or cool). Scenes with familiar
objects will be easy to interpret with some experience. The camera automatically optimizes the image
to provide the best contrast in most conditions.
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