mn2718281828
The figure shown on the project board is my first attempt to demonstrate the multispectral computer vision plant biofeedhack system concept. The picture was taken with a modified LED grow light and Raspberry Pi noir camera. The picture shows different images of a five week old basil plant leaf illuminated by different LED wavelengths. Top left is a computer vision enhanced image. Top right is white light image. Images below are recorded with ultraviolet (uv1,uv2), blue(blu), green (grn), red and infrared (ir) LED light. Remaining pictures are processed composite images that highlight color contrast. Computer vision software (SimpleCV) extracts the leaf image (colored dark green) and measures number of pixels in the area, length, width and perimeter (bottom text). The picture shows that a measurement system can be built to characterize plant growth and multispectral leaf reflectance. The measurements can then be used to tailor the LED light for different growth conditions.
Update Mar 2019.
Several related computer vision projects using opencv are posted at:
Steve Schuler
Celine
Tim Gremalm
Hi. You know that, for example, using red and green light together doesn't really make yellow light? It's an illusion caused by the human vision system. We have receptors, nominally red, that is sensitive to red but also a fair way into yellow. Nominally-green responds to orange through to cyan. Etc.
So true spectral yellow of 580nm excites the red and green cones. Your brain is wired to know that, so something stimulating R + G is assumed to be yellow. But it could also just be a red and green light, separately, shining on the same area, reflecting into the eye. Seeing red and green simultaneously, the brain assumes it's seeing yellow, but no 580nm is there, just 550nm and 650nm. The brain can't comprehend two separate colours in one area. So it assumes.
Of course, that's how your monitor works. But at school it was implied the colours "mix" somehow or somewhere, perhaps on the illuminated object. But we're also taught that light waves of different colours don't interfere. The final step, it's an illusion in the human head-meat, I was certainly never told and I don't think most people are.
If a plant cares about colour (and they do), then you have no yellow to offer them. The chemical reactions in their leaves aren't fooled by imitation yellow! (or magenta, or any other visible colour beside the 3 you have supplied).
So my point is, perhaps you need a wide spectrum of LEDs, you can get them in all sorts of in-between wavelengths, it's surprising how many variants there are, even plain red and green have a few varieties, often "superbright" LEDs are just of a wavelength we respond better to.
I'm not certain whether you need these other wavelengths, just pointing out something that, certainly, I wasn't aware of for quite a long time into my adult life.
Oh of course this R+G+B illusion thing also applies to most cameras! They use the same system, since they were built for humans. This might not be a problem, since like us, they can see yellow, even though they really can't see yelllow! So you can still take photos of whichever wavelength, you just need to be sure you're applying the correct one.
[hmm, wouldn't it be interesting to make a camera whose RGB filters were very strict and narrow? so they'd only detect a narrow band around 650nm red, etc. Yellow or cyan would show up dark, not pass the receptor. In a way it would demonstrate human sight and how things actually look! In a way...]