Thermal Imaging

Thermal imaging of leaves is important in assessing a plant’s responses to heat load and water deprivation.  Regulation of stomatal aperture to balance the opposing requirements of drought avoidance and self-cooling is critical to the survival of crops under extreme conditions.  Variations in mechanisms for self-cooling may allow certain plants to better withstand periods of high irradiance and low water availability.

Measuring leaf temperature with a high resolution camera may seem a simple solution to assessing variations within and between plants in their ability to regulate temperature by evapotranspiration.  However, care must be taken to ensure that any measured variations result from the physiological responses of the plant, rather than environmental variations in the measurement chamber.  For this reason, the PlantScreen™ system is designed to create homogeneous incident irradiance at fixed distances from the LED panels, and the LED panels themselves produce minimal heat load on the leaf.


Technique Description
  • Measurement of long-wavelength infrared (LWIR) range of the electromagnetic spectrum
  • Dynamic measurement of infrared radiation emitted by all objects
  • Analysis of spatio-temporal variations in stomatal conductance and transpiration over plant surface
  • Automatic accurate calculation of plant surface temperature
  • Leaf temperature is used as indicator of leaf water content, for measurement of stomatal conductance and mutant selection, as a selection trait for drought resistance in dry environments, etc.
Key Features
  • Non-destructive measurement of plant and leaf temperature
  • Highly homogenous LED light panel for active thermal image acquisition
  • Top and side view configuration possible
  • Rotating table for multiple angle thermal image acquisition
  • Programmable measuring protocols
  • Automatic data analysis
  • Temperature -controlled cabinet wall for high contrast imaging

The PlantScreenTM thermal imaging station incorporates a customized LWIR camera with a resolution of 1024 x 760 pixels and 16 bit depth.  Such high resolution allows greater spatial discrimination of thermal zones within the sample. Average, standard deviation, median and minimal and maximal temperature are obtained across the whole plant surface.  Housed in a light proof cabinet with automatic doors, it includes a light source to induce dynamic responses so that the camera can be used to assess stomatal activity and/or water distribution within plants. Most thermal imaging systems merely generate simple heat maps which are not very robust indicators of the plant’s physiological responses, since these are influenced by environmental parameters that can vary in greenhouse conditions. Heat maps may not result in meaningful values when compared with measurements of temperature dynamics.
The wall of the thermal imaging cabinet is maintained at a fixed temperature higher than that of the plant to create contrast between the image of the plant and the wall, allowing for easy discrimination of the plant tissue against background. The station includes multiple PT1000 sensors for ambient temperature measurements.


Thermal Imaging Includes:

  • Position feedback
  • Conveyor belt with position
  • Automatic entrance
  • Top view and manual side
  • Adjustable light panel with camera above plant Range: 0 – 1250 mm
  • Accuracy ± 3 mm
  • User-defined height position via software, or automatic positioning based on measured height of
  • User can manually move camera into side view measuring
  • Controlled thermal environment with LED light panel for illumination of samples with adjustable intensity of illumination
  • White LED light source with maximum intensity 1000 µmol photons/m2/s, measured 50 cm from light source. Desired light intensity set in software with range of 0 – 100% and steps of 1%
  • User-defined measuring protocol
  • Automated object selection. Objects selected using masks created from RGB
  • PC with control software
  • Data and picture stored in database or local PC if database is not accessible
  • Scanning time depends on protocol g. 5s for single picture to minutes when plant response to environmental change is studied
  • Reference temperature sensor with known

Thermal Camera Specifications

Spectral range 7.5 – 14 um Temperature stabilization No thermoelectric cooling

required (TEC-less)

Detector Uncooled Microbolometer

Focal Plane Array

Integration type Rolling shutter
Detector format (IR pixels) 1024 x 768 A to D conversion resolution 16 bit
NETD <0.02°C @ + 30°C/ 20 mK Camera Control GigE Vision
Pixel operability > 99% Trigger In or out (Configurable)
Lens (included Wide angle, 15 or 30mm Operating temperature -25  to 55C
Frame rate: 30 Hz @ full frame (up to

240Hz sub-format

Dimensions 220 x 101 x 95 mm (L x W

x H)

Window of interest Window mode possible – 640×480@60Hz,

384×288@120Hz,

1024×96@240Hz

Head Weight 1.2 Kg