The Allure of Multicolored Images

by Michael Vollmer | Klaus-Peter Mollmann

Подпись: Building thermography using infrared cameras is becoming increasingly popular, since effective thermal insulation of buildings is in great demand. The gaudy false-colour images contain a great deal of information, but can easily be misin-terpreted by those lacking in knowledge and experience. We give an introduction to the technology and its tricks on the basis of selected examples. The technology of infrared imaging systems has developed rapidly since the mid-1990s. It has been driven by progress in microsystem technology, which has produced increasingly powerful detector arrays (sensors for infrared radiation) and read-out circuits. At present, a variety of camera systems for various applications are on the market [1]. They are used in many areas of technology and teaching [1-4]. For civil applications, IR cameras with megapixel detector arrays are already available. In recent years, much less expensive cameras with a smaller number of pixels have come onto the market. Typical of these are systems in the price range under 5000 1, with 160 x 120 or even only 60 x 60 pixels, and reduced software options. This is not surprising, since contact-free temperature measurement is an excellent instrument for analyzing e.g. the thermal insulation of buildings (Figure 1). image216"

In this field, the word “infrared” is often replaced by “thermal”, so that one usually speaks of thermal cameras and thermal images.

This basically positive development however creates some problems, in particular since the false-color images must be interpreted correctly. There are many traps lurking here, and we demonstrate some of them using examples. For this reason, several businesses and also the camera man­ufacturers offer training and certification courses on the fundamentals and applications of thermography [5]. To be sure, such courses cost as much as the less expensive cam­eras, so that some “services” dispense with the course and nevertheless offer thermographic analyses.

This is where the problem begins, as measurements car­ried out with an IR camera can be traced back to a variety of different sources of thermal radiation. Here, in addition to the object being investigated, the environment and even the camera itself play a role. In addition, there is a large number of possible error sources in recording and inter­preting thermal images [1]. These can be avoided or cor­rected only by users who have a precise knowledge of the underlying thermal and radiation transport mechanisms. Untrained users, on the other hand, often simply produce colorful pictures.