Leaf surface assessment
Measurement of foliage surfaces for the assessment of leaf indices is a tedious task and/or requires expensive equipment. We have developed a method which is based on a commercial scanner and data processing by our own software development.
Leaves are spread on the scanner window and scanned at a line distance of 0.25 mm. In addition, the reflected light is assessed for the three basic colour components (red, green, blue = RGB). Spatial resolution is set to 16 pixels per mm 2 which is sensitive enough for leaf area measurement and still allows rapid scans. Signal noise is reduced by image pre-processing which detects and eliminates “noisy” pixels.
The software assesses as well “green levels”. This provides further information beyond the mere leaf area measurement. Threshold levels can be set for brightness and green levels. When properly adjusted, the area for healthy and diseased or dead tissue can be indicated separately. Thus, the device provides information about the total leaf area as well as the proportion of diseased tissue. For plausibility testing, the scan can be displayed as preview image. Any changes of RGB and brightness levels are mirrored in the image, which helps to find the proper setting for each individual species and situation (diseases).
The device can be run in any lab at low costs. The equipment has been extensively tested and proven to be reliable and fast.