Gregor Geršak

Dr. Gregor Geršak

University of Ljubljana, Electrical engineering department, Ljubljana, Slovenia
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Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 December 2018 in Multimedia Tools and Applications
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GGGregor Geršak
Gregor Geršak
HLHuimin Lu
Huimin Lu
Jože GunaJože Guna
Jože Guna

16 January 2021 in Sensors
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Igor PušnikIgor Pušnik
Igor Pušnik
GGGregor Geršak
Gregor Geršak
In numerous applications, including current body temperature monitoring in viral pandemic management, thermal imaging cameras are used for quantitative measurements. These require determination of the measurement accuracy (error) and its traceability (measurement uncertainty). Within error estimation, the size-of-source effect (SSE) is an important error source. The SSE is the relation between the physical size of a target and the instrument’s nominal target size. This study presents a direct evaluation of the error due to the SSE. A stable and uniform temperature, generated by blackbodies, was measured by a high-quality thermal imager. To limit the generated radiation, custom-made blocking tiles with different apertures were used. Effects of aperture shapes and positions, camera-target distances and temperature levels on the error were investigated. The study findings suggest that due to the SSE the measured temperatures are too low, especially at longer camera-target distances. The SSE error depends on the number of pixels available and included into the region of interest, for which the accurate measurement is about to be performed. For an accurate temperature measurement, an array of at least 10 × 10 pixels should be exposed to the observed target radiation, while 3 × 3 central pixel area should be included in the temperature calculation.

5 February 2020 in PLOS ONE
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GGGregor Geršak
Gregor Geršak
JDJanko Drnovšek
Janko Drnovšek
Electrodermal activity (EDA) is an electrical property of the human skin, correlated with person’s psychological arousal. Nowadays, different types of EDA measuring devices are used in highly versatile fields–from research, health-care and education to entertainment industry. But despite their universal use the quality of their measuring function (their accuracy) is questioned or investigated very seldom. In this paper, we propose a concept of an EDA patient simulator—a device enabling metrological testing of EDA devices by means of a variable resistance. EDA simulator was designed based on a programmable light-controlled resistor with a wide resistance range, capable of simulating skin conductance levels (SCL) and responses (SCR) and was equipped with an artificial hand. The hand included electrically conductive fingers for attachment of EDA device electrodes. A minimal set of tests for evaluating an EDA device was identified, the simulator’s functionality discussed and some testing results presented.

13 October 2009 in Medical & Biological Engineering & Computing
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GGGregor Geršak
Gregor Geršak
AŽAleš Žemva
Aleš Žemva
JDJanko Drnovšek
Janko Drnovšek

16 November 2017 in Sensors
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JKJure Kranjec
Jure Kranjec
SBSamo Beguš
Samo Beguš
GGGregor Geršak
Gregor Geršak
MŠMatjaž Šinkovec
Matjaž Šinkovec
JDJanko Drnovšek
Janko Drnovšek
DHDomen Hudoklin
Domen Hudoklin
The object of the proposed paper is to design and analyze the performance of a non-contact heart rate variability (HRV) measuring device based on ultrasound transducers. The rationale behind non-contact HRV measurement is the goal of obtaining a means of long term monitoring of a patient’s heart performance. Due to its complexity as a non-contact measuring device, influential physical quantities, error source and other perturbations were thoroughly investigated. For medical purposes it is of utmost importance to define the target uncertainty of a measuring method from the side of physicians, while it is the role of scientists to realistically evaluate all uncertainty contributions. Within this paper we present a novelty method of non-contact HRV measurement based on ultrasound transducers operating at two frequencies simultaneously. We report laboratory results and clinical evaluations are given for healthy subjects as well as patients with known heart conditions. Furthermore, laboratory tests were conducted on subjects during a relaxation period, and after 1 min physical activity