Quantitative traceable temperature measurement using novel thermal imaging camera.

Matthew J Hobbs,Matthew P Grainger,Chengxi Zhu,Jon R Willmott,Chee Hing Tan

doi:10.1364/oe.26.024904

Abstract

Conventional thermal imaging cameras, based on focal-plane array (FPA) sensors, exhibit inherent problems: such as stray radiation, cross-talk and the calibration uncertainty of ensuring each pixel behaves as if it were an identical temperature sensor. Radiation thermometers can largely overcome these issues, comprising of only a single detector element that can be optimised and calibrated. Although the latter approach can provide excellent accuracy for single-point temperature measurement, it does not provide a temperature image of the target object. In this work, we present a micromechanical systems (MEMS) mirror and silicon (Si) avalanche photodiode (APD) based single-pixel camera, capable of producing quantitative thermal images at an operating wavelength of 1 µm. This work utilises a custom designed f-theta wide-angle lens and MEMS mirror, to scan +/- 30° in both x- and y-dimensions, without signal loss due to vignetting at any point in the field of view (FOV). Our single-pixel camera is shown to perform well, with 3 °C size-of-source effect (SSE) related temperature error and can measure below 700 °C whilst achieving ± 0.5 °C noise related measurement uncertainty. Our measurements were calibrated and traceable to the International Temperature Scale of 1990 (ITS-90). The combination of low SSE and absence of vignetting enables quantitative temperature measurements over a spatial field with measurement uncertainty at levels lower than would be possible with FPA based thermal imaging cameras.

Highlights

Thermal imaging cameras are commonly used in manufacturing and industrial processing for fault detection, temperature measurement and process control [1,2,3,4]
When the measurement of absolute temperature is required, a quantitative approach to thermal imaging should be used. Such applications require the measurement of temperature not at a single-point upon the target, which could be provided by the use of a single-pixel radiation thermometer [5,6,7], but over a spatial field, in the form of a thermal image temperature map
The use of focal-plane array (FPA) based thermal imaging cameras for accurate quantitative temperature measurements provides significantly increased measurement uncertainties compared to radiation thermometers

Summary

Introduction

Thermal imaging cameras are commonly used in manufacturing and industrial processing for fault detection, temperature measurement and process control [1,2,3,4]. Such applications require the measurement of temperature not at a single-point upon the target, which could be provided by the use of a single-pixel radiation thermometer [5,6,7], but over a spatial field, in the form of a thermal image temperature map. The use of FPA based thermal imaging cameras for accurate quantitative temperature measurements provides significantly increased measurement uncertainties compared to radiation thermometers.

Results

Conclusion