Table 1.
Summary of sensors that have been used for phenotyping PPI
| Sensor, technology | Imaging/non-imaging | Active/passive | Effect measured | Excitation/illumination wavelengths | Measured wavelengths |
|---|---|---|---|---|---|
| Monochrome | Imaging | Mainly active | Reflectance | Variable | Variable |
| RGB | Imaging | Mainly active, passive at large scale | Reflectance | Variable, usually visible spectrum |
Range: ~ 400–700 nm R: ~ 600 nm G: ~ 530 nm B: ~ 460 nm |
| Hyperspectral | Both | Mainly active, passive at large scale | Reflectance, transmission | Variable | 400–2500 nm |
| Thermal | Mainly imaging | Passive | Emission | NA | 8–15 µm |
| Chlorophyll fluorescence (kinetics) | Imaging/non-imaging | Active | Emission | 400–700 nm | ~ 650–800 nm |
| Fluorescence | Imaging/non-imaging | Active | Emission | Mostly 300–400 nm | Mainly 400–700 nm |
| Raman spectroscopy | Non-imaging | Active | Inelastic scattering of photons (Raman scattering) | Variable, often 785–830 nm [17] | Raman bands, 400–2133 cm−1 [18] |
| Optical coherence tomography | Imaging | Active | Reflectance of coherent light | 800–1000 nm or 1200–1400 nm | 800–1000 nm or 1200–1400 nm |
| X-ray computed tomography | Imaging | Active | Attenuation, phase shift | ~ 0.01–0.1 nm | Visible light using scintillator |