Electromagnetic metamaterials, made from arrangements of subwavelength-sized structures, can be used to manipulate radiation. Designing metamaterials that have a positive refractive index along one axis and a negative refractive index along the orthogonal axis can result in birefringences, $\mathrm{\Delta }n>1$. The effect can be used to create wave plates with subwavelength thicknesses. Previous attempts at making wave plates in this way have resulted in very narrow usable bandwidths. In this paper, we use the Pancharatnam method to increase the usable bandwidth. A combination of finite element method and transmission line models was used to optimize the final design. Experimental results are compared with the modeled data.

Efficient strawberry harvesting using semi-autonomous robotic pickers requires a method for fast, automatic discrimination between ripe and unripe berries. In this paper we present a strawberry ripeness algorithm that has been developed and tested on images obtained with commercial cameras, recorded under daylight illumination on an outdoor strawberry farm. The method uses a 2D lookup table seeded such that regions for ripe strawberry, unripe strawberry and strawberry calyx exist in distinct locations in the table. Measurements show the ratio of ripe to unripe area provides a good estimator of ripeness and that the approach was practical for further extension to real-time use.

High-throughput phenotyping requires the automation of the process of extracting relevant quantitative information from crop images. We achieve this goal for dense wheat crops by applying model-based data analysis techniques (including clustering and data-fitting) to high-resolution 3D point clouds obtained from structured light laser scanners. By performing experiments comparing our estimates of crop height, spike height and spike width with manual measurements, we demonstrate that our approach is promising even in the challenging context of dense vegetation.

A first investigation into the use of microwaves for the non-destructive testing for the presence of black heart cavities is presented. Additionally a potato's complex permittivity data between 0.5 GHz to 20 GHz measured using a coaxial sensor and the recipe for a potato phantom are also presented. Electromagnetic finite-difference time-domain simulations of potatoes show that changes to how microwaves propagate through a potato caused by a cavity can produce measurable changes in S₂₁ at the potato's surface of up to 26 dB. Lab-based readings of the change in S21 caused by a phantom cavity submerged in a potato phantom liquid confirms the results of the simulation, albeit at a much reduced magnitude in the order of 0.1 dB.

The in-field measurement of phenotypes or traits of wheat such as ear size is important data for use in the development of newer wheat varieties. The data is currently gathered manually from hundreds of test plots by random sampling of the what within each plot. To improve the data quality and data collection speed, we investigate and compare the use three different 3D imaging technologies: multistereo imaging, time-of-flight and structured light laser scanning to produce point clouds of a wheat plant in-situ. Measurements of the wheat plant’s ear is made from the generated point clouds.