Multichannel Ultrasound Focusing Delay Control Method Based on Variable-Length Shift Register for Airborne Ultrasound Tactile Feedback

This paper presents a multichannel ultrasound focusing delay control method based on a variable-length shift register to solve the problem of using counters that occupy more resources. The proposed method can realize the delay control of the driving signal of each transducer of an ultrasound array and achieve ultrasound focusing. While collecting and storing the input data, the shift register moves the stored data to the right, and the delay control of driving signals of all the channels can start simultaneously by controlling the enabling time of the input signal of the shift register. Using experiments, it is verified that the error of the proposed method is related to the frequency of the delay control clock; the higher the frequency of the delay control clock is, the smaller the error and the diameter of the focal point are. The proposed method uses only one shift register to achieve ultrasound focusing without using additional hardware circuits and thus occupies fewer system resources. The proposed method can be applied in the human-computer interaction, virtual reality, and augmented reality fields.