Friday, July 14, 2017

Imaging Fruit from the Ground Up

A suggestion given at a program review in the Robotics Vision lab where I'm working this summer was to image fruit from below the trees. The reasoning is that the fruits would hang down where the leaves can't block the view to them. It sounds like a good idea, however, I found the thermal imager would respond well to this. Why?

Yep, there's fruit here. The peaches are still green, but visible from beneath the tree.
The thermal infrared image from near the center of the visible image above. There are peaches to the left and bottom left of the dark hole above the center of the image.
The issue with the Seek Reveal (at least with the way I have it set up) is that it scales the colors of its image based on the range of temperatures it detects. Looking up means the imager will see the sky. Now the sky is very cold in thermal infrared, meaning the sky becomes the black color setting. The warmest tree leaf or fruit meanwhile become the white color setting. Since there is such a large difference between the cold sky and the warm leaves and fruit, any difference in temperature between a fruit and a leaf is tiny in comparison. Therefore, no difference between fruit and leaves can be made out in the image.

Thermal imaging may still be useful for distinguishing between fruit and leaves with robotic vision. That's because fruit, being more massive than a leaf, should maintain a warmer temperature after a cool night. However, for thermal imaging to detect this, the thermal image needs to be taken without the sky being in view. Or, the thermal imager can't auto-scale its image based on temperature extremes it detects.

I may need a different thermal imager to make robotic vision possible.    

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