Development of fast scanning module to efficiently enhance the capabilities of imaging system in biological and industrial applications

Abstract

Noninvasive inspection and nondestructive testing are the powerful technologies that have been used for material evaluation in biological and industrial applications, respectively, owing to their capabilities in structure visualization without causing damage to the original material. In these technologies, imaging system is a full-feature instrument that is used to visualize the internal structure of material in two-dimensional (2D) image. A specific sensor probe is attached to the scanning module of the imaging system, which is controlled to conduct the movement in a sequence in order to construct the 2D image. Till date, many researches have been reported to improve the scanning module of the imaging system in term of reducing scanning time while maintaining the high resolution of 2D image. In this study, a novel fast scanning module (FSM) was developed by exploiting the slider-crank mechanism, which was applied to imaging system to efficiently enhance its capabilities in biological and industrial applications. In biological applications, the FSM was developed based on a versatile slider-crank mechanism in term of changing the scanning range corresponding to a suitable B-scan frame rate for different scanning areas. The sensor probe was designed by integrated a laser light source and an ultrasound (US) transducer, which provided simultaneously the photoacoustic (PA) and US signals. The laser pulses were focused on the sample, thereby generating the acoustic waves due to thermoelastic expansion phenomenon. These acoustic waves were detected by an US transducer in PA imaging. In the US imaging, the same US transducer was used to propagate the US waves to the sample and receive the echo waves reflected off the sample. By acquiring simultaneous PA and US signals at the same time in each lateral resolution, integrated PA and US (PAUS) imaging system provided functional and anatomical information of the sample. The dragonfly wing was successfully imaged in the ex vivo experiment, which demonstrated the potential applications of the PAUS system in biological imaging. In the industrial applications, scanning acoustic microscopy (SAM) system was developed to evaluate the quality of the sample. Owing to the focused US transducer characteristics, SAM system was utilized to visualize the internal structure of some industrial products. First, the traditional SAM system (TSAM-400) was built to evaluate the resistance spot welding (RSW) joint under different welding parameters. By analyzing the scanning results, the good welding parameters for joining two stainless steel plates were determined. Second, the fast SAM system (FSAM) was designed based on a single slider-crank mechanism that was optimized for specific sample in order to significantly reduce the scanning time. Depend on the sample size, the multi-channels using the identical US transducers were implemented to extend the scanning area. The integrated circuit (IC) chip and RSW sample were successfully captured by using the FSAM with one channel. The FSAM system using two and four channels were setup to scan the printed circuit board (PCB) and 8-inch silicon wafer, respectively. Third, the WFSAM system was developed by exploiting double slider-crank mechanism that was used to evaluate the quality of 12-inch silicon wafer. Two slider-crank mechanisms were arranged to conduct the opposite rotation motion with a constant angular velocity in term of self-balanced of the system. To efficiently enhance the SAM capabilities in the in-line inspection, a novel water-probe was proposed to use for SAM system, that is waterstream. By using waterstream, the tested sample has been not immersed in water, which leads to the simple design of automotive SAM system and reduce the time-consumption. Waterstream is simulated to investigate the flow characteristics inside, which illustrates the continuous flow between transducer and sample, thereby maintaining the acoustic coupling during the scanning process. Moreover, the water pressure value is approximately equal to the atmospheric pressure, which can avoid any damage to the sample. Finally, waterstream is applied to the TSAM-400 and WFSAM systems to successfully capture image of some sample. These results demonstrate the potential application of waterstream in SAM in-line inspection.