The heat is on

Developments in infrared imaging mean that it is now more powerful, and more affordable than ever giving more and more laboratories the chance to utilise thermographic technology

The advantages of using infrared to study thermal performance are manifold but its non-contact, non-destructive capabilities are perhaps the reason why this technology has become such an important instrument in such a broad variety of research and development applications. Heat patterns are very difficult to predict. This means that it is rarely possible to know where to attach thermocouples to make accurate measurements and evaluate heat dissipation effectively. Furthermore, since the thermocouple needs to be in contact with the component under test, it can influence and even compromise the test results. 
 
An infrared camera produces comprehensive images in a non-contact mode. Even if the exact location of the problem isn’t obvious it will show up very clearly – and sometimes at the most unexpected location – on the thermal image. Today’s infrared cameras can produce very high-resolution images so that the smallest of temperature differences on the smallest of objects can be seen. Frames can be stored in real-time and at high speed allowing for detailed and extensive analysis of highly dynamic events typically found in R&D environments.
 
New detector technologies have also made infrared cameras more affordable than ever.  Thanks to this evolution, universities and smaller research centres are also discovering the benefits of infrared. Complementary software packages have also become extremely powerful. The visual comparison of thermal images can be difficult as subtle temperature changes cannot always be detected by the naked eye. Thanks to features such as image subtraction, two thermal images can now have the temperature of each pixel subtracted from each other. The resultant image will show just the temperature differences between the two images and sometimes this differential can be extremely small.
 
Superframing is another important infrared development for R&D. This facility dramatically extends the effective scene brightness of an infrared imaging system whilst maintaining thermal contrast even at low temperature. It consists of varying the exposure or the integration time of the camera from frame to frame in a cyclic manner.  The resulting subframes are then combined into single superframes that greatly extend temperature ranges allowing scenes featuring extreme temperature differences to be visualised easily.
 
Connectivity is also a significant development area. Cameras now have Gigabit Ethernet, Camera Link and USB interfaces to extend their flexibility and have their own URL for easy networking.

A good example of this latest generation of infrared cameras is the new ThermoVision SC6000HS from FLIR Systems. Available as an off-the-shelf package it can be specified with a choice of detector, software platform, high-speed data recorder and optics to optimise performance.
 
The product of two and half years of R&D itself, this has been designed to record and analyse the thermal performance of dynamic events typically in the field of pulsed laser detection, atmospheric phenomenology, non-destructive testing and target signature research.
 
The camera’s high 18mK sensitivity and high image quality is provided by its cooled 640 x 512 (327,680 pixels) focal plane array. It can be equipped with a choice of detector to suit the wavelength required. The indium antimonide (InSb) option for example makes events between 3 and 5 micron waveband clearly visible whilst the indium gallium arsenide (InGaAs) FPA is for researchers typically involved in target signature and laser research who want to see what is happening between 0.9 and 1.7 micron  waveband .  A quantum well infrared detector (QWIP) model is also available for those interested in the long wave section of the IR spectrum, from 8 to 9.2 microns.
 
The SC6000 Series cameras are also the first to introduce high-speed FPA windowing and simultaneous video output and new read-out technology is an important contributor to this performance. It allows a subset of the total image to selectively read-out with user-adjustable window size at a much higher frame rate. The sub-sample window size and location can be arbitrarily chosen and is easily defined using the camera control software.
 
This read-out technology, in the form of a standard CMOS integrated circuit, also allows a range of other advanced features to be incorporated such as snapshot simultaneous pixel exposure, adjustable gain for low background applications, variable exposure times, invert/revert and precise external synchronisation in a variety of modes.
 
Infrared cameras now of course come in a range of shapes and sizes for either fixed or portable use. Even the lower end scientific cameras are considerably more powerful and affordable than they were just a few years ago. Many are IEE1394 Firewire enabled providing 50Hz frame rates and 50 mK NETD. With a choice of lenses and software they have a variety of analogue and digital I/O to enable batch triggers, external optics correction and alarms to be enabled. Compatibility with other systems such as Compact Vision from National Instruments is also beneficial in the research environment.
 
So typically where would you find infrared in daily use? Its application is wide-ranging.  In the pharmaceutical industry scientists employ thermography to study temperature changes and chemical reactions in new drug development. New cooking, baking and freezing techniques in the food industry are developed with its help. And it is naturally being used in fundamental and applied research in universities as infrared technology has become easily affordable.
 
In the medical field infrared is now accepted as an accurate and reliable tool for medical assessment and diagnosis. While traditional use in the study of vascular problems such as Raynaud’s syndrome is well documented, a variety of other applications are coming to the fore, including  changes in the thermal conductivity of the skin caused by burns, skin ulceration or other grafting, as well as the re-assessment of the benefits of the technique in early detection of breast cancer . Other common applications include the early detection of skin cancer, in pain management, burn depth assessment, fever detection and open heart surgery.
 
In the automotive sector infrared is firmly established in the development of new, energy efficient components and systems. Researchers are using the technology to look at the total heat management of cars. Many of today’s common car features such as windshield defrosting and seat heating are being developed and tested with its help, as well as the management of heat dissipation in power electronics - particularly pertinent as new hybrid vehicles are evolving . The thermal performance of tyres is another hot topic.
 
The technology also has a significant presence in the non-destructive testing arena  - particulary in the Aerospace industry with the stress analysis of engineering composites and other high performance materials. It is used to determine under what circumstances the material begins to fatigue and is therefore a highly important process in aircraft design. Aviation uses also include shock and pulse thermography as a regular part of the inspection of passenger and military aircraft. 
 
The veterinary world provides a variety of applications for the thermal imaging camera.  As heat is one of the major signs of inflammation or injury infrared is ideal for detection and diagnosis. Frayed nerves and muscle damage can also be easily seen. Typical applications include axial pathology, articular pathology, fractures, tendi-nopathies and podo-trochlear syndrome. Infrared is also widely used in animal behavioural studies.
 
As our world becomes more computerised there is considerable demand for products that are smaller, higher-performing and easier to use. Laptops, mobile phones, digital cameras and AV equipment are all subject to this trend. Scientists designing these products are challenged with managing heat dissipation without sacrificing performance or cost. Thanks to thermography they are able to visualise and quantify heat patterns easily in the devices they create.  Macro- and microscopic lenses make it possible to view the smallest targets.
 
Infrared has always shown great potential in scientific research and product development and year on year it becomes more powerful, more flexible and easier to use. However what makes it such an exciting prospect is that this continues to be achieved in tandem with cost reduction. Infrared is no longer the domain of big budgets. It is a technology that is now highly affordable and many believe we are only just scratching the surface of what it can be employed to do.

By Paul Slacker
Paul Sacker is the Sales and Marketing Manager at FLIR Systems UK, the UK arm of the world’s largest infrared company.  He holds degrees in mechanical engineering and business management and has been involved in the fields of condition monitoring and predictive maintenance since 1993.