Page 41 - EE Times Europe November 2021 final

EE|Times EUROPE 41

PARTNER CONTENT
Thermal Imaging Sensors for Fever Detection

By Hasan Gadjali, Co-Founder and COO, and Stanislav Nikolaev Markov, Scientist, Meridian Innovation Ltd.

here are many applications in elec-
tronics that promise to make our lives
more comfortable and safer. Thermal
T imaging cameras are increasingly seen
to hold such promise, particularly since the
onset of the Covid-19 pandemic.
The rapid global spread of the virus
presented an unprecedented challenge to
public health, food systems, and the world of
work and led to a dramatic loss of human life
worldwide. It decimated jobs and placed mil-
lions of livelihoods at risk. In the face of this
crisis, finding a way to measure body tem-
perature quickly from a distance — including
the ability to scan groups of people simulta-
neously, without the need to interfere with
their activity — becomes very important for
managing the pandemic. This is because an
elevated temperature is one of the common
symptoms of viral infection, and therefore, Figure 1: Visual camera image versus thermal camera image (Source: Meridian Innovation)
the ability to efficiently identify people who
are running a fever can help to confine the
spread of the virus that causes Covid-19. way, e.g., by changing their resistance or by Beyond a simple analogy, the reference
Thermal imaging sensors are at the core of generating a voltage output due to the to a gray-scale image is useful because one
the technology that gives us this ability. Seebeck effect. These changes are amplified can easily intuit that a thermal image can
and digitized by a readout circuit, and the also be processed and analyzed by more or
Thermal imaging sensors resulting digital codes are eventually trans- less standard techniques of visual image
processing. It can also be displayed as an
formed into temperature values.
are now readily available Therefore, each thermal detector measures informative heat map, whereby for each
and affordable for mass- the surface temperature of the objects in its temperature value, there is a specific associ-
own instantaneous field of view — the frac-
ated color.
market products, and tion of the world from which it can perceive An example of a visual image, gray-scale
reference hardware designs emitted heat radiation. The ordered two- thermal image, and a colored thermal image
— all three pertaining to the same scene — is
dimensional array of detectors then yields
are emerging to facilitate a two-dimensional array of pixels — akin to shown in Figure 1.
a gray-scale visual image, but in this case,
These thermal images are captured by a
adoption of the technology. each pixel represents how hot that part of the special camera module using the LWIR ther-
scene is, instead of how bright it is. mal imaging chip shown in Figure 2.
THERMAL IMAGING SENSORS
But what are thermal imaging sensors, and
how do thermal imaging cameras let us mea-
sure core body temperature from a distance?
Thermal imaging sensors are microelectro-
mechanical system (MEMS) chips that include
an array of detectors sensitive to impinging
long-wave infrared electromagnetic radiation
(LWIR), in the range of 8- to 14-μm wave-
lengths. All objects above 0 Kelvin and all
living organisms radiate in this spectral range,
and the intensity of this radiation is represen-
tative of their surface temperature.
Unlike visual light of wavelengths between
400 and 700 nm, LWIR radiation is invisible
to the human eye. However, the detectors
forming the array of a thermal imager are
able to respond to the incident infrared heat Figure 2: Meridian Innovation 80 × 62 resolution LWIR thermal imaging chips and
by changing their properties in a measurable module (Source: Meridian Innovation)

www.eetimes.eu | NOVEMBER 2021