Evaluation of the size-of-source effect in thermal imaging cameras

Pušnik, Igor (author), Geršak, Gregor (author)

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.

• Language: English
• Keywords: temperature, thermal imaging camera, accuracy, size-of-source effect, SSE, region of interest, ROI
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FE - Faculty of Electrical Engineering
• Publication status: Published
• Publication version: Version of Record
• Year: 2021
• Number of pages: 22 str.
• Numbering: Vol. 21, iss. 2, art. 607
• PID: 20.500.12556/RUL-134901
• UDC: 621.317
• ISSN on article: 1424-8220
• DOI: 10.3390/s21020607
• COBISS.SI-ID: 47911683
• Publication date in RUL: 10.02.2022

Record is a part of a journal

• Title: Sensors
• Shortened title: Sensors
• Publisher: MDPI
• ISSN: 1424-8220
• COBISS.SI-ID: 10176278

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.
• Licensing start date: 16.01.2021

Secondary language

• Language: Slovenian
• Keywords: temperatura, termovizijske kamere, točnost, učinek velikosti vira, SSE, področje zanimanja, ROI

Projects

• Funder: ARRS - Slovenian Research Agency
• Project number: P2-0225
• Name: Metrologija in kakovost

• Funder: Other - Other funder or multiple funders
• Funding programme: Republic of Slovenia, Ministry of Economic Development and Technology, Metrology Institute
• Project number: 6401-18/2008/70