Optical stem diameter measurement for crop monitoring

The greenhouse horticulture sector is constantly looking for ways to optimize and further automate production processes. This leads to an increasing focus on sensor technology to monitor crop growth and development. Stem thickness and its variation is a crucial indicator of crop growth. However, traditional methods that involve contact with the crop—such as mechanical calipers—can cause damage, negatively impacting plant growth.

In this project, we are investigating whether a non-contact optical measurement method can be a reliable and better alternative to current mechanical measurements. The measurement concept, based on a laser and camera, was developed in a previous project (Measuring crop growth with sensors) by the Photonics research group at The Hague University of Applied Sciences for a different, less demanding application. However, it shows great promise for continuous, high-precision measurements, such as those required for stem thickness variations. A prototype of the measuring instrument will be developed and tested in collaboration with the companies 2Grow and Quantified. Accuracy, long-term reliability under greenhouse conditions, and integration with the data infrastructure are the key objectives.

Target group

• Horticultural sector and its technical suppliers

Results

• Prototype of stem thickness sensor with comparable accuracy as contact-based sensors (targeted resolution: 1 µm).
• Pre-production prototype
• Validated sensor performance based on long-term measurements in commercial greenhouse

Duration

Oktober 2025 – September 2026

Team 

Photonics research group 

• Daan Boesten, junior researcher ([email protected])
• Steven van den Berg, professor Photonics

Partners

Quantified, 2Grow

Funding

Regieorgaan SIA en Holland High Tech, KIEM HighTech programma