If visibility is poor, thermal cameras can warn drivers of people or
animals on the road. Yet such devices have been very expensive –
until now. An important step has been taken to manufacture them more
cheaply. A new process will make the infrared lenses – a
component of such cameras – up to 70 percent cheaper.
Rain pelts down on the roof of the car; it is difficult to make out
anything in the pitch dark. Suddenly, a deer runs out of the forest and
onto the road, but the driver cannot respond in time. When it comes to
such dangerous situations, micro-bolometers constitute one way of
“extending” the human eye and defusing such dangerous
situations. They detect infrared rays – in other words, the heat
emitted by a living creature – and in case of danger, warn the
driver through an acoustic signal or a warning light. At about 2,000
euros, these devices are still quite expensive and are only being used
in luxury-class vehicles.
Production costs drop by over 70 percent
Part for part, these devices should be getting more affordable.
Researchers at the Fraunhofer Institute for Mechanics of Materials IWM
in Freiburg are working on the infrared lenses that are in the cameras.
“We have developed a production process for lenses that enables
us to lower the costs of these components by more than 70 percent. Thus
the prize for the micro-bolometer could be reduced,” says Dr.
Helen Müller, scientist at IWM. Normally, the lenses are made out
of crystalline materials like germanium, zinc selenide or zinc sulfide.
The problem is that these materials are very expensive and can only be
processed mechanically – it takes grinding, polishing or diamond
turning to shape them into the correctly. Obviously this involves high
processing costs. “Instead of crystalline materials, we use the
amorphous chalcogenide glass. Its softening temperature – that
is, the temperature at which it can be formed – is low.
Therefore, we can form it using non-isothermic hot stamping,”
says Müller. This process is similar to making waffles on a waffle
iron. The researchers place the chalcogenide glass between two pressing
tools which determine the form of the required lenses. Then, it is
heated and formed between both pressing tools – the “waffle
iron” is clamped together. After a few minutes, the glass is
cooled again to below the softening temperature and removed. And thus,
the lens is already perfect. In contrast to conventionally processed
optics, it no longer has to be further refined. The lenses manufactured
this way exhibit the same excellent optical imaging quality as those
that are polished. To ensure that no glass remains attached to the
tools, their surface is coated with anti-adhesive, non-stick coatings,
similar to the Teflon coating on a waffle iron. The scientists now want
to further refine the process towards cost-effective mass production.
The applications for micro-bolometers – and thus for
cost-effective lenses – are not limited to the automotive sector.
Imagine, for example, these devices assisting older people in their
homes, If the senior were to fall, the bolometer registers this event
and sends an alarm to relatives or neighbors through an optical or
acoustic signal. In production halls, bolometers can oversee and
monitor the production processes of various products, to ensure the
necessary temperatures are maintained and warn employees who are
spending time in danger zones. In residential buildings, the devices
could detect energy leaks, such as through unsealed windows or poorly
More information at http://www.iwm.fraunhofer.de/