Photoacoustic imaging, an emerging biomedical imaging modality, holds great promise for preclinical and clinical researches. It combines the high optical contrast and high ultrasound resolution by converting laser excitation into ultrasonic emission. In order to generate photoacoustic signal e±-ciently, bulky Q-switched solid-state laser systems are most commonly used as excitation sources and hence limit its commercialization. As an alternative, the miniaturized semiconductor laser system has the advantages of being inexpensive, compact, and robust, which makes a signi¯cant e®ect on production-forming design. It is also desirable to obtain a wavelength in a wide range from visible to nearinfrared spectrum for multispectral applications. Focussing on practical aspect, this paper reviews the state-of-the-art developments of low-cost photoacoustic system with laser diode and light-emitting diode excitation source and highlights a few representative installations in the past decade.
In this paper, a Fabry–Pérot interference fiber sensor was fabricated by using a Polyvinyl chloride membrane (20 μm in thickness) attached at the end of a ferrule with an inner diameter of 1.1 mm. In consideration of the vibration response of the membrane, the feature of the first-order natural frequency of membrane was analyzed by COMSOL Multiphysics. The acoustic sensing performance of the Fabry–Pérot fiber interference sensor was studied in air. The results reveal that the sensor possessed good acoustic pressure sensitivity, in the order of 33.26 mV/Pa. In addition, the noise-limited minimum detectable pressure level was determined to be 58.9 μPa/Hz1/2 and the pressure-induced deflection obtained was 105 nm/Pa at the frequency of 1 kHz. The response of the sensor was approximately consistent with the reference sensor from 1 to 7 kHz. All these results support that the fabricated Fabry–Pérot fiber interference sensor may be applied for ultra-sensitive pressure sensing applications.
Currently, biometrics are widely used in recognition technology; however, biometric recognition systems are vulnerable to malicious spoofing attacks. Thus, the security of such systems requires enhancements. This paper reports a novel vascular recognition system based on simple photoacoustic imaging to resist spoofing attacks. The amplitude and the delay of the maximum-value arrival time of the photoacoustic signal were used for detecting the vascular optical absorption and depth prior to vascular imaging. The proposed photoacoustic detection system detected fake vascular biometrics and demonstrated improved recognition rates with resistance toward spoofing attacks. In addition, the recognition rate increased from 95% to 97.5% as only real vasculatures were imaged. Moreover, the results verified the feasibility of using photoacoustic images for vascular recognition. The proposed photoacoustic system is noninteracting, low cost, robust, and highly anticounterfeiting.
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