Radioprotection No 59-4 | Page 88

Radioprotection 2024 , 59 ( 4 ), 327 – 337 © J . M . Deniel , Published by EDP Sciences , 2024 https :// doi . org / 10.1051 / radiopro / 2024022 Available online at : https :// www . radioprotection . org /

ARTICLE

Assessing optical radiation exposure to opaque incandescent materials by picture analysis � Part 2 : from pixel radiance to eye irradiance

J . -M . Deniel * Institut national de recherche et de sécurité ( INRS ), 1 , rue du Morvan , CS 60027 , 54519 Vandoeuvre-lès-Nancy Cedex , France . Received : 31 October 2023 / Accepted : 20 June 2024

Abstract – Incandescent materials emit optical radiation that can cause cataracts , especially in industrial processes . This risk must be assessed to help employers choose an effective means of protecting workers . Where possible , this is done by software simulation . Otherwise , near-infrared irradiance must be measured at the worker ’ s eye . Since radiometers and spectroradiometers are too expensive for most preventers , a novel and virtually free method has been proposed . Using a photograph , it assesses irradiance by summing the irradiance corresponding to each pixel representing the opaque glowing materials in the image . Pixel irradiance is evaluated from the radiance of the colored body whose temperature and emissivity correspond to the pixel color , weighted by the geometric configuration associated with the pixel in the camera perspective . The first principle � converting pixel color to radiance � was the subject of a first paper . This paper presents the second principle : calculating irradiance at the eye from pixel radiance . This method is accurate enough to assess cataract risk , thereby helping employers to protect workers . An easy and inexpensive way to calibrate the camera is under investigation in view to making it widespread .

Keywords : infrared radiation / imaging / occupational exposure

1 Introduction

Industrial workers are at risk for skin burns and thermal damage to the retina and to the cornea ( cataracts ). This is due to visible and infrared optical radiation emitted by incandescent materials , typically in the 800 to 1,300 ° C range .

The European Union has set occupational daily limits ( European Union , 2006 ) for the average occupational irradiance E IR from infrared radiation ( IR ). It is expressed in equation ( 1.1 ) where E ( l ) is the spectral irradiance at the eye .

* Corresponding author : jean-marc . deniel @ inrs . fr

Software simulation cannot assess certain exposure situations . In these cases , it is necessary to measure IR irradiance at the worker ’ s eye , which requires expensive equipment . To avoid this pitfall a novel method has been presented ( Deniel , 2024 ), that is affordable for most preventers .

This method considers a color camera picture as a matrix of pixel colors , where each pixel p corresponds to a direction in space from the camera ’ s point of view . It is based on two principles shown in the flowchart in Figure 1 , explained in the previous and present papers respectively .

The first is illustrated in the right part of Figure 1 . It assumes that a colored body with spectral emissivity m ( l ) ata given temperature T can represent the radiance of an incandescent opaque material . This B ( m , T l ) radiance follows equation ( 1.2 ), where h is the Planck constant , c is the speed of light in the vacuum , and k is the Boltzmann constant .

Bm ð ; T ; lÞ ¼ 2hc2 l 5

�

1 exp hc klT

mðlÞ � 1 ð1:2Þ

The previous paper ( Deniel , 2024 ) explains how to convert the color of any pixel p corresponding to a glowing opaque material into a spectral emissivity m p ( l ) and a temperature T p , then into B ( m , T p , l ).

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( https :// creativecommons . org / licenses / by / 4.0 ), which permits unrestricted use , distribution , and reproduction in any medium , provided the original work is properly cited .