IEEE Instrumentation & Measurement - September 2023 - 25

its ability to produce consistent and reliable results over time.
All sensors are working as expected and the system is capable
of executing its main functions for 1-2 hours, depending on
the number of concurrent tasks. Finally, a series of safety and
user experience tests were conducted, described in the follow
section.
Electromagnetic Compatibility (EMC) Tests
Electromagnetic radiation is intrinsic to electronic devices, and
all devices radiate a certain amount of energy. To ensure the
correct performance of surrounding devices and avoid health
issues, the radiated energy must remain within certain thresholds
to comply with certain standards. In compliance with
the UNE EN 55011 Standard, the prototype was identified as
group 1 class B device. Therefore, it was tested in an anechoic
chamber at a distance of 3 m from an antenna, with its cables
wrapped to avoid loops. The maximum emission value was
identified at 324 MHz with a magnitude value of 45.8 dB(uV),
which is close to the limit threshold. Consequently, a quasipeak
test was carried out for a range of frequencies from 320
to 340 MHz to verify the magnitude of this peak. The results of
this test are displayed in Fig. 4. The quasi-peak is 40.2 dB(uV)
which is much lower than the threshold of this frequency of
47 dB(uV). Thus, the result of the test indicates that the device
operates within the thresholds set by international standards
for devices of its class.
Thermal Measurements
Thermal tests aim to prove the safety of any device by demonstrating
that it is not able to cause harm due to contact with
the user's skin. Thermal images identify the highest thermal
pixel of the image and provide a thermal map and corresponding
scale for the entire image. Fig. 5 provides thermal pictures
of the smart glasses after 1 hour of operation. The images were
taken in the USE laboratory with the FLIR e90 thermal camera.
The temperature reached in the glasses after 1 hour of operation
causes no skin damage and, therefore, is not hazardous
for the user.
End User Tests
An initial set of tests including potential patients and doctors
who used the prototype were conducted. During the tests, the
end users evaluated the system's functionalities and ease of
use. The test population consisted of 30 participants, 45% of
whom were men and 55% were women. All participants were
employed people over 40 years old. The following graph depicts
the users' feedback regarding the benefits that the See
Far solution introduces as a percentage of the participants that
found each feature of the system very, fairly, slightly or not at
all important.
Feedback from the tests suggests that the See Far glasses
solution can be a beneficial tool for working people with
visual impairments. Functionalities related to image processing
were the most promising features enabled by AR
technologies. Magnification was the most relevant functionality,
followed by contrast and brightness increments.
The merger of both functionalities awakened the patients'
interest.
On the contrary, functionalities related to navigation, such
as obstacles or hazard recognition, were considered not important.
The feature-related functionalities like face recognition
were considered as not so important, being mainly supported
by presbyopia and glaucoma patients.
(a)
The system's usability and the fact that the buttons needed
to operate the device were kept to a minimum were also key
evaluation points. The glasses' weight and appearance were a
major concern. The low-profile waveguide lenses of the glasses
drew the attention of patients, resulting in positive feedback.
On the other hand, the users found the device a bit bulky and
(b)
Fig. 4. EMC emissions, V axis (dBμV)/(a) Operating measurement; (b) Quasipeak
measurement.
September 2023
Fig. 5. Thermal images of glasses frame front part after one hour of
operation.
IEEE Instrumentation & Measurement Magazine
25

IEEE Instrumentation & Measurement - September 2023

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