Radioprotection No 59-4 | Page 92

J-M Deniel : Radioprotection 2024 , 59 ( 4 ), 327 – 337 331
Table 1 . Exposure to our blackbody at various ZþZ 0 distances : theoretical E th and measured E m irradiance on [ 1,000 ; 2,500nm ], and estimated
by theory E IR , th and CatRayon E 5 IR , CR and camera picture analysis E IR , pc on [ 780 ; 3,000nm ]. At 800 celsius and 97 and 492 mm measurements
failed . At 1,100 celsius and 97 mm the camera and the blackbody were a little misaligned . They were too misaligned at 1,200 celsius and
172 mm .
Black body temperature
Distance Z + Z 0
∫ 2 ; 500nm l¼1 ; 000 EðlÞ∂l theory
measured
∫ 3 ; 000nm
l¼780 EðlÞ∂l theory
by CR 5
by camera
setting
Z + Z 0
E th
E m
E IR , th
5
E IR , CR
E IR , pci
° C
mm
W / m 2
800
97
209
� *
344
368
300
172
67
39
109
108
96
492
8
� *
13
13
12
900
97
381
341
589
579
527
172
122
101
187
185
175
492
15
12
23
22
22
1,000
97
644
571
944
928
811
172
207
174
299
198
220
492
25
20
37
36
32
1,100
97
1,023
918
1,433
1,410
863 **
172
328
292
455
452
343
492
40
33
55
56
47
1,200
97
1,542
1,348
2,083
2,050
1,886
172
495
440
661
657
� ***
492
61
49
81
81
73
1,300
97
2,231
2,089
2,922
2,876
2,711
172
716
692
927
922
846
492
88
74
113
112
102
E th ≈ p r2 d 2
∫
2500nm
l¼1000
2hc 2
l 5
1 � ∂l ð3:1Þ � 1 exp hc klT
Table 2 . Comparison of E m measured and E IR estimated irradiance in front of our metal furnace . NB : at 1140 ° C , pixels corresponding to the heating coils are overexposed : their red channel is saturated .
In Table 1 ,
– over [ 1,000 ; 2,500 nm ], we compare E th and E m irradiance ,
– over [ 780 ; 3,000 nm ], we compare theoretical E IR , th irradiance and estimations by CatRayon ( E IR , CR 5 ) and picture analysis ( E th , pic ).
3.2 Estimated vs measured irradiance from the metal furnace
As shown in Figure 2 the camera and the optics were positioned next to each other in front of the furnace opening . A pipe reduced the spectroradiometer optics field of measurement to limit E m irradiance from the surrounding . The conditions of measurement and camera shots were those described in ( Deniel , 2024 ).
The furnace opening is not a clear virtual frontier as in the case of the blackbody . That is why we considered the focus distance on the nearest samples inside the furnace . We
ð estimated an irradiance correction factor Z�Z 0Þ 2 between 1.131
Z 2 and 1.1524 .
Temp . setting Focusing dist . E m E IR ° C mm W / m 2
800
1,051
399
377
900
1,026
785
984
1,000
998
1,453
1,797
1,100
1,150
1,924
1,820
1,140
1,143
2,685
2,690 *
Table 2 shows the comparison of irradiance between E m measured over [ 1,000 ; 2,500 nm ] and E IR evaluated by picture analysis over [ 780 ; 3,000 nm ].
3.3 Picture definition vs irradiance estimation
It is possible to retrieve camera pictures in definitions equal and lower than that of the sensor . This may be advantageous in terms of memory space consumption and the number of pictures retrieved and analyzed per second . However , there is a loss in precision , each pixel being associated with a wider solid angle and hue changing especially along the edges and shape of the items .