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This paper presents a hardware design of an ultrasound imaging system for transmitting pulses and acquiring echo signals to/from individual elements of an array transducer. Since most of the ultrasound imaging systems in the market provide only image files after reconstruction, the presented hardware can be controlled by a computer in order to transmit pulses in specific patterns to transducer elements and in order to access the data from individual transducer elements. It benefits the research and development of new algorithms for beamforming, image reconstruction, and other applications, such as elastography and ultrasonic transmission tomography.

Problem statement: Uniformly herbicide rate is used as a conventional practice in Thailand for controlling weeds in sugarcane fields. Since weeds usually grow in certain areas with nonuniformly distribution, uniform herbicide rate approach is not suitable and non-sustainable agricultural technique both in terms of economic an environmental aspect. To address these issues, Variable Herbicide Rate (VHR) was introduced. The VHR composes of two main components, which are weed monitoring and real-time spraying. Approach: This study investigated with a development of a fast and robust weed monitoring system for VHR using over between-row of sugarcane fields. The proposed method was designed to work under natural illumination condition. The near-ground images were captured using a typical web camera without any assistant light diffuser. The proposed weed monitoring is a machine vision based approach. The Non Green Subtraction (NGS) technique was proposed for soil background segmentation. Results: The proposed technique exploited variations among three triplets, which are red, green and blue under bright and dull lighting condition to achieve better background segmentation results. The non-background pixels were then classified into weeds and non-weeds using the Offset Excessive Green (OEG) technique. Conclusion: From our experimental results, the proposed method is robust under illumination variations such as in sunny and after raining day conditions. Weeds under different lighting conditions are reliably detects. The approach is less sensitive to chosen threshold value comparing to the OEG technique. The proposed method is very effective especially in spare weeds condition. It is fast, suitable for using in real-time application.

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An ultrasound image is reconstructed from echo signals received by array elements of a transducer. The time of flight of the echo depends on the distance between the focus to the array elements. The received echo signals have to be delayed to make their wave fronts and phase coherent before summing the signals. In digital beamforming, the delays are not always located at the sampled points. Generally, the values of the delayed signals are estimated by the values of the nearest samples. This method is fast and easy, however inaccurate. There are other methods available for increasing the accuracy of the delayed signals and, consequently, the quality of the beamformed signals; for example, the in-phase (I)/quadrature (Q) interpolation, which is more time consuming but provides more accurate values than the nearest samples. This paper compares the signals after dynamic receive beamforming, in which the echo signals are delayed using two methods, the nearest sample method and the I/Q interpolation method. The comparisons of the visual qualities of the reconstructed images and the qualities of the beamformed signals are reported. Moreover, the computational speeds of these methods are also optimized by reorganizing the data processing flow and by applying the graphics processing unit (GPU). The use of single and double precision floating-point formats of the intermediate data is also considered. The speeds with and without these optimizations are also compared.