Thermal Image Bruise Detection

Thermal imaging is a non-destructive and non-contact infrared sensing technique, which creates a bit-map called a thermogram by detecting infrared radiation emitted from an object. Up to 100% of apple bruises were detected using thermal imaging during warming of the fruit, due to differences in thermal diffusivity and between bruised and sound tissue. Apples were bruised by dropping them from 0.46 m on a smooth concrete floor and then were held at 26°C and 50% RH for 48 hours. They were then thermally imaged using a ThermaCamaPM390 (FLIR Systems, Inc., Portland, OR) during heating and cooling treatements. Thermal images of bruised tissue showed at least 1-2°C difference from sound tissue within 30-180 s. Thermal imaging did not detect bruises under steady-state temperature conditions, indicating that detection was not due to differences in thermal emissivity. The technique could provide a basis for automatic bruise sorting, and possibly a better understanding of bruised tissue.